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Sample records for al cr mn

  1. Oxidation behavior of cubic phases formed by alloying Al3Ti with Cr and Mn

    NASA Technical Reports Server (NTRS)

    Parfitt, L. J.; Nic, J. P.; Mikkola, D. E.; Smialek, J. L.

    1991-01-01

    Gravimetric, SEM, and XRD data are presented which document the significant improvement obtainable in the oxidation resistance of Al3Ti-containing alloys through additions of Cr. The L1(2) Al(67)Cr(8)Ti25 alloy exhibited excellent cyclic oxidation resistance at 1473 K, with the primary oxide formed being the ideally protective alpha-Al2O3. The Al(67)Mn(8)Ti(25) alloy also tested for comparison exhibited poor cyclic oxidation resistance, with substantial occurrence of TiO2 in the protective scales. Catastrophic oxidation was also encountered in the quaternary alloy Al(67)Mn(8)Ti(22)V(3).

  2. Electrochemical deposition and microstructural characterization of AlCrFeMnNi and AlCrCuFeMnNi high entropy alloy thin films

    NASA Astrophysics Data System (ADS)

    Soare, V.; Burada, M.; Constantin, I.; Mitrică, D.; Bădiliţă, V.; Caragea, A.; Târcolea, M.

    2015-12-01

    Al-Cr-Fe-Mn-Ni and Al-Cr-Cu-Fe-Mn-Ni high entropy alloy thin films were prepared by potentiostatic electrodeposition and the microstructure of the deposits was investigated. The thin films were co-deposited in an electrolyte based on a DMF (N,N-dimethylformamide)-CH3CN (acetonitrile) organic compound. The energy dispersive spectrometry investigation (EDS) indicated that all the five respectively six elements were successfully co-deposited. The scanning electron microscopy (SEM) analysis revealed that the film consists of compact and uniform particles with particle sizes of 500 nm to 4 μm. The X-ray diffractometry (XRD) patterns indicated that the as-deposited thin films were amorphous. Body-centered-cubic (BCC) structures were identified by XRD after the films were annealed at various temperatures under inert Ar atmosphere. The alloys adhesion on the substrate was determined by the scratch-testing method, with higher values obtained for the Al-Cr-Cu-Fe-Mn-Ni alloy.

  3. New type of Schottky diode-based Cu-Al-Mn-Cr shape memory material films

    NASA Astrophysics Data System (ADS)

    Aksu Canbay, C.; Dere, A.; Mensah-Darkwa, Kwadwo; Al-Ghamdi, Ahmed; Karagoz Genç, Z.; Gupta, R. K.; Yakuphanoglu, F.

    2016-07-01

    Cr-doped CuAlMn shape memory alloys were produced by arc melting method. The effects of Cr content on microstructure and transformation parameters of were investigated. The alloys were characterized by X-ray analysis, optical microscope observations and differential scanning calorimetry measurements. The grain size of the alloys was decreased by the addition of Cr into CuAlMn alloy system. The martensite transformation temperature was shifted both the lower temperature and higher temperature with the addition of chromium. This change was explained on the basis of the change in the thermodynamics such as enthalpy, entropy and activation energy values. The obtained results indicate that the phase transformation temperatures of the CuAlMn alloy system can be controlled by addition of Cr. We fabricated a Schottky barrier diode and observed that ideality factor and barrier height increase with increasing temperature. The diodes exhibited a thermal sensor behavior. This indicates that Schottky diode-based Cu-Al-Mn-Cr shape memory material films can be used as a sensor in high-temperature measurement applications.

  4. Synthesis of Waste Form in the Gd-Fe-Al-Ni-Mn-Cr-O System

    SciTech Connect

    Chae, S.C.; Jang, Y.N.; Bae, I.K.; Ryu, K.W.

    2006-07-01

    Poly-phase waste form which was the mixture of Gd{sub 3}Fe{sub 2}Al{sub 3}O{sub 12} and (Ni{sub x}Mn{sub 1-x})(Fe{sub y}Cr{sub 1-y}){sub 2}O{sub 4} was synthesized. Also, we are intended to examine phase relation and physicochemical properties of coexisted phases in the compositions and to confirm accommodation relation of elements and phases. Two types of phase series were observed: Garnet-perovskite-spinel and Garnet-spinel. The compositions of garnets and spinels were nonstoichiometric, and especially, this poly-phase ceramics may be in a good waste form. The excessive Gd in garnets indicated the immobilization of higher content of actinides. The nonstoichiometric compositions of garnet and spinel were attributed to the formation of perovskite in that perovskite contained Gd, Fe and Al from garnet and Cr from spinel. (authors)

  5. Interlayer thickness dependence of 90° exchange coupling in Co2MnAl/Cr/Co2MnAl epitaxial trilayer structures

    NASA Astrophysics Data System (ADS)

    Bosu, S.; Sakuraba, Y.; Saito, K.; Wang, H.; Mitani, S.; Takanashi, K.; You, C. Y.; Hono, K.

    2009-04-01

    The spacer layer thickness dependence of interlayer exchange coupling has been investigated in the fully epitaxial trilayers of the Co2MnAl (CMA)/Cr/CMA structure. A series of high-quality samples of CMA (20 nm)/Cr (tCr=0.3-8.1 nm)/CMA (10 nm) trilayers was prepared on a MgO substrate by ultrahigh vacuum compatible dc sputtering. Comparison of the results of the experiments and the simulations of magnetization curves revealed novel behavior, dominating the 90° coupling and the absence of 180° coupling. No clear oscillation, only a peak of the 90° coupling strength (J2˜-0.68 erg/cm2), was observed at tCr=1.2 nm.

  6. Plasma-Sprayed High Entropy Alloys: Microstructure and Properties of AlCoCrFeNi and MnCoCrFeNi

    NASA Astrophysics Data System (ADS)

    Ang, Andrew Siao Ming; Berndt, Christopher C.; Sesso, Mitchell L.; Anupam, Ameey; S, Praveen; Kottada, Ravi Sankar; Murty, B. S.

    2015-02-01

    High entropy alloys (HEAs) represent a new class of materials that present novel phase structures and properties. Apart from bulk material consolidation methods such as casting and sintering, HEAs can also be deposited as a surface coating. In this work, thermal sprayed HEA coatings are investigated that may be used as an alternative bond coat material for a thermal barrier coating system. Nanostructured HEAs that were based on AlCoCrFeNi and MnCoCrFeNi were prepared by ball milling and then plasma sprayed. Splat studies were assessed to optimise the appropriate thermal spray parameters and spray deposits were prepared. After mechanical alloying, aluminum-based and manganese-based HEA powders revealed contrary prominences of BCC and FCC phases in their X-ray diffraction patterns. However, FCC phase was observed as the major phase present in both of the plasma-sprayed AlCoCrFeNi and MnCoCrFeNi coatings. There were also minor oxide peaks detected, which can be attributed to the high temperature processing. The measured porosity levels for AlCoCrFeNi and MnCoCrFeNi coatings were 9.5 ± 2.3 and 7.4 ± 1.3 pct, respectively. Three distinct phase contrasts, dark gray, light gray and white, were observed in the SEM images, with the white regions corresponding to retained multicomponent HEAs. The Vickers hardness (HV0.3kgf) was 4.13 ± 0.43 and 4.42 ± 0.60 GPa for AlCoCrFeNi and MnCoCrFeNi, respectively. Both type of HEAs coatings exhibited anisotropic mechanical behavior due to their lamellar, composite-type microstructure.

  7. Electronic structure, magnetism, and antisite disorder in CoFeCrGe and CoMnCrAl quaternary Heusler alloys

    SciTech Connect

    Enamullah, .; Venkateswara, Y.; Gupta, Sachin; Varma, Manoj Raama; Singh, Prashant; Suresh, K. G.; Alam, Aftab

    2015-12-10

    In this study, we present a combined theoretical and experimental study of two quaternary Heusler alloys CoFeCrGe (CFCG) and CoMnCrAl (CMCA), promising candidates for spintronics applications. Magnetization measurement shows the saturation magnetization and transition temperature to be 3 μB, 866 K and 0.9 μB, 358 K for CFCG and CMCA respectively. The magnetization values agree fairly well with our theoretical results and also obey the Slater-Pauling rule, a prerequisite for half metallicity. A striking difference between the two systems is their structure; CFCG crystallizes in fully ordered Y-type structure while CMCA has L21 disordered structure. The antisite disorder adds a somewhat unique property to the second compound, which arises due to the probabilistic mutual exchange of Al positions with Cr/Mn and such an effect is possibly expected due to comparable electronegativities of Al and Cr/Mn. Ab initio simulation predicted a unique transition from half metallic ferromagnet to metallic antiferromagnet beyond a critical excess concentration of Al in the alloy.

  8. Electronic structure, magnetism, and antisite disorder in CoFeCrGe and CoMnCrAl quaternary Heusler alloys

    DOE PAGESBeta

    Enamullah, .; Venkateswara, Y.; Gupta, Sachin; Varma, Manoj Raama; Singh, Prashant; Suresh, K. G.; Alam, Aftab

    2015-12-10

    In this study, we present a combined theoretical and experimental study of two quaternary Heusler alloys CoFeCrGe (CFCG) and CoMnCrAl (CMCA), promising candidates for spintronics applications. Magnetization measurement shows the saturation magnetization and transition temperature to be 3 μB, 866 K and 0.9 μB, 358 K for CFCG and CMCA respectively. The magnetization values agree fairly well with our theoretical results and also obey the Slater-Pauling rule, a prerequisite for half metallicity. A striking difference between the two systems is their structure; CFCG crystallizes in fully ordered Y-type structure while CMCA has L21 disordered structure. The antisite disorder adds amore » somewhat unique property to the second compound, which arises due to the probabilistic mutual exchange of Al positions with Cr/Mn and such an effect is possibly expected due to comparable electronegativities of Al and Cr/Mn. Ab initio simulation predicted a unique transition from half metallic ferromagnet to metallic antiferromagnet beyond a critical excess concentration of Al in the alloy.« less

  9. Cubic structure and canted antiferromagnetism of CaMn7O12 doped with trivalent cations (Fe, Al, Cr)

    NASA Astrophysics Data System (ADS)

    Motin Seikh, Md.; Caignaert, V.; Lebedev, O. I.; Raveau, B.

    2014-02-01

    In this study, we show the dramatic effect of the doping of the octahedral sites with M3+ cations (Fe3+, Al3+ and Cr3+) upon the structure and magnetism of the rhombohedral double perovskite CaMn7O12. In the oxides CaMn7-xMxO12, charge ordering between Mn3+ and Mn4+ octahedral sites is destroyed leading to the cubic structure (Im-3), whereas the initial magnetic properties (TN~90 K) have disappeared leading to canted antiferromagnetism (TN≈50-70 K) for small x values (x ~0.2-1). A spin glass like behaviour is also observed for larger values (x~1) in the case of Fe substitution.

  10. Crystal growth and magnetic properties of Ln-Mn-Al (Ln=Gd, Yb) compounds of the CaCr{sub 2}Al{sub 10} and ThMn{sub 12} structure types

    SciTech Connect

    Fulfer, Bradford W.; Haldolaarachchige, Neel; Young, David P.; Chan, Julia Y.

    2012-10-15

    We report the growth and characterization of LnMn{sub 2+x}Al{sub 10-x} (Ln=Gd, Yb) crystals adopting the CaCr{sub 2}Al{sub 10} and ThMn{sub 12} structure types. Single crystals of LnMn{sub 2+x}Al{sub 10-x} were synthesized via the self-flux method and characterized with single crystal X-ray diffraction. We compare LnMn{sub 2+x}Al{sub 10-x} compounds adopting the CaCr{sub 2}Al{sub 10} and ThMn{sub 12} structure types, and outline synthesis methods to obtain each polymorph. Magnetic susceptibility measurements show paramagnetic behavior down to 3 K for both CaCr{sub 2}Al{sub 10}- and ThMn{sub 12}-type compounds, with observed magnetic moments of 1.3{mu}{sub B} for compounds adopting the CaCr{sub 2}Al{sub 10} structure type to 4.2{mu}{sub B} for those adopting the ThMn{sub 12} structure type. Compounds of both structure type exhibit metallic resistivity, with upturns at low temperature attributed to Kondo scattering. - Graphical abstract: We report the growth and characterization of LnMn{sub 2+x}Al{sub 10-x} (Ln=Gd, Yb) crystals adopting the CaCr{sub 2}Al{sub 10} and ThMn{sub 12} structure types. Single crystals of LnMn{sub 2+x}Al{sub 10-x} were synthesized via the self-flux method and characterized with single crystal X-ray diffraction. We compare LnMn{sub 2+x}Al{sub 10-x} compounds adopting the CaCr{sub 2}Al{sub 10} and ThMn{sub 12} structure types, and outline synthesis methods to obtain each polymorph. Magnetic susceptibility measurements show paramagnetic behavior down to 3 K for both CaCr{sub 2}Al{sub 10}- and ThMn{sub 12}-type compounds, with observed magnetic moments of 1.3{mu}{sub B} for compounds adopting the CaCr{sub 2}Al{sub 10} structure type to 4.2{mu}{sub B} for those adopting the ThMn{sub 12} structure type. Compounds of both structure type exhibit metallic resistivity, with upturns at low temperature attributed to Kondo scattering. Highlights: Black-Right-Pointing-Pointer We have grown Ln (Mn,Al){sub 12} (Ln=Gd, Yb) single crystals of the ThMn{sub 12

  11. The effects of Ni, Mo, Ti and Si on the mechanical properties of Cr free Mn steel (Fe-25Mn-5Al-2C)

    NASA Technical Reports Server (NTRS)

    Schuon, S. R.

    1982-01-01

    The FeMnAlC alloys may hold potential as Cr-free replacements for high strategic material iron base superalloys, but little is known about their intermediate temperature (650 C to 870 C) mechanical properties. The effects of alloying elements on the mechanical properties of model FeMnAlC alloys were studied. Results showed that modified FeMnAlC alloys had promising short term, intermediate temperature properties but had relatively poor stress rupture lives at 172 MPa and 788 C. Room temperature and 788 C tensile strength of FeMnAlC alloys were better than common cast stainless steels. Changes in room temperature tensile and 788 C tensile strength and ductility, and 788 C stress rupture life were correlated with changes in Ni, Mo, Ti, and Si levels due to alloying effects on interstitial carbon levels and carbide morphology. Fe-25Mn-5Al-2C had a very poor stress rupture life at 172 MPa and 788 C. Addition of carbide-forming elements improved the stress rupture life.

  12. Interdiffusion between the L1(2) trialuminides Al66Ti25Mn9 and Al67Ti25Cr8

    NASA Technical Reports Server (NTRS)

    Kumar, K. S.; Whittenberger, J. D.

    1992-01-01

    Concentration-distance profiles obtained from Al66Ti25Mn9/Al67Ti25Cr8 diffusion couples are used to determine the interdiffusion coeffients in the temperature range 1373-1073 K. The couples are treated as pseudobinaries, and the diffusion coefficients are determined using the Matano approach. The results are then used to compute the activation energies for diffusion, and a comparison is made with some existing data for the activation energy for creep of Al22Ti8Fe3.

  13. Galvanomagnetic properties of Fe2YZ (Y = Ti, V, Cr, Mn, Fe, Ni; Z = Al, Si) heusler alloys

    NASA Astrophysics Data System (ADS)

    Kourov, N. I.; Marchenkov, V. V.; Belozerova, K. A.; Weber, H. W.

    2015-11-01

    The Hall effect and the magnetoresistance of Fe2YZ Heusler alloys, where Y = Ti, V, Cr, Mn, Fe, and Ni, are the 3 d transition metals and Z = Al and Si are the s, p elements of the third period of the periodic table, are studied at T = 4.2 K in magnetic fields H ≤ 100 kOe. It is shown that, in the high-field limit ( H > 10 kOe), the value and the sign of the normal ( R 0) and anomalous ( R s ) Hall coefficients change anomalously during transition from paramagnetic (Y = Ti, V) to ferromagnetic (Y = Cr, Mn, Fe, Ni) alloys. These coefficients have different signs for all alloys. Constant R s in the ferromagnetic alloys is positive, proportional to the residual resistivity ratio ( R s ∝ ρ 0 3.1 ), and inversely proportional to spontaneous magnetization. The magnetoresistance of the alloys is a few percent and has a negative sign. A positive addition to transverse magnetoresistance is only detected in high magnetic fields, H > 10 kOe.

  14. Galvanomagnetic properties of Fe{sub 2}YZ (Y = Ti, V, Cr, Mn, Fe, Ni; Z = Al, Si) heusler alloys

    SciTech Connect

    Kourov, N. I. Marchenkov, V. V.; Belozerova, K. A.; Weber, H. W.

    2015-11-15

    The Hall effect and the magnetoresistance of Fe{sub 2}YZ Heusler alloys, where Y = Ti, V, Cr, Mn, Fe, and Ni, are the 3d transition metals and Z = Al and Si are the s, p elements of the third period of the periodic table, are studied at T = 4.2 K in magnetic fields H ≤ 100 kOe. It is shown that, in the high-field limit (H > 10 kOe), the value and the sign of the normal (R{sub 0}) and anomalous (R{sub s}) Hall coefficients change anomalously during transition from paramagnetic (Y = Ti, V) to ferromagnetic (Y = Cr, Mn, Fe, Ni) alloys. These coefficients have different signs for all alloys. Constant R{sub s} in the ferromagnetic alloys is positive, proportional to the residual resistivity ratio (R{sub s} ∝ ρ{sub 0}{sup 3.1}), and inversely proportional to spontaneous magnetization. The magnetoresistance of the alloys is a few percent and has a negative sign. A positive addition to transverse magnetoresistance is only detected in high magnetic fields, H > 10 kOe.

  15. Compression, bend, and tension studies on forged Al67Ti25Cr8 and Al66Ti25Mn(g) L1(2) compounds

    NASA Technical Reports Server (NTRS)

    Kumar, K. S.; Brown, S. A.; Whittenberger, J. D.

    1991-01-01

    Cast, homogenized, and isothermally forged aluminum-rich L1(2) compounds Al67Ti25Cr8 and Al66Ti25Mn(g) were tested in compression as a function of temperature and as a function of strain rate at elevated temperatures (1000 K and 1100 K). Three-point bend specimens were tested as a function of temperature in the range 300 K to 873 K. Strain gages glued on the tensile side of the ambient and 473 K specimens enabled direct strain measurements. A number of 'buttonhead' tensile specimens were electro-discharge machined, fine polished, and tested between ambient and 1073 K for yield strength and ductility as a function of temperature. Scanning electron microscope (SEM) examination of fracture surfaces from both the bend and tensile specimens revealed a gradual transition from transgranular cleavage to intergranular failure with increasing temperature.

  16. Effects of anodic passivation on the constitution, stability and resistance to corrosion of passive film formed on an Fe-24Mn-4Al-5Cr alloy

    NASA Astrophysics Data System (ADS)

    Zhang, Y. S.; Zhu, X. M.; Liu, M.; Che, R. X.

    2004-01-01

    The effects of anodic aging time and potential on the corrosion resistance, stability and constitution of the passive film formed on an Fe-24Mn-4Al-5Cr alloy in 50% HNO 3 solution were studied by using combined electrochemical measurements and Auger electron spectroscopic (AES)/X-ray photoelectron spectroscopic (XPS) analysis. In the anodic passive region, prolonged anodic aging time or increased passivating potential can induce better protective and stable properties of the passive film and better resistance to corrosion. With increasing aging time from 15 min to 5 h, the time required for the potential decay from the passive to active state increases from about 300 up to above 12,000 s, and the corrosion resistance in 1 mol l -1 Na 2SO 4 solution of Fe-24Mn-4Al-5Cr alloy, characterized by polarization curves, is superior to that of Fe-13% Cr-0.1% C stainless steel. AES and XPS analyses of the aging passive film show that these improvements of properties are related to modifications of the passive layer with time. The increase of resistance to corrosion is attributed to Al 2O 3 and Cr 2O 3 enrichment and oxides of Fe and Mn depletion in the passive film and a thickening of the effective barrier layer of oxides.

  17. High-field magnetization of heusler alloys Fe2 XY ( X = Ti, V, Cr, Mn, Fe, Co, Ni; Y = Al, Si)

    NASA Astrophysics Data System (ADS)

    Kourov, N. I.; Marchenkov, V. V.; Korolev, A. V.; Belozerova, K. A.; Weber, H. W.

    2015-10-01

    The magnetization curves of ferromagnetic Heusler alloys Fe2 XY (where X = Ti, V, Cr, Mn, Fe, Co, Ni are transition 3 d elements and Y = Al, Si are the s and p elements of the third period of the Periodic Table) have been measured at T = 4.2 K in the field range H ≤ 70 kOe. It has been shown that the high-field ( H ≥ 20 kOe) magnetization is described within the Stoner model.

  18. Structural Investigation and Indium Substitution in the Thermoelectric Mn2.7Cr0.3Si4Al2- x In x Series

    NASA Astrophysics Data System (ADS)

    Barbier, Tristan; Combe, Emmanuel; Funahashi, Ryoji; Takeuchi, Tomonori; Kubouchi, Masataka; Miyazaki, Yuzuru; Guilmeau, Emmanuel; Suzuki, Ryosuke O.

    2016-03-01

    Following the recent discovery of the promising Mn2.7Cr0.3Si4Al2 thermoelectric compound (having, e.g., automotive, industrial, and solar conversion applications), structural characterization by x-ray single-crystal diffraction analysis has been performed. This layered material is composed of two distinct crystallographic sites where both (Mn, Cr) and (Al, Si) are randomly distributed. The deduced crystallographic parameters were then confirmed by powder x-ray diffraction analysis through a temperature dependence of the phase stability, showing at the same time chemical stability up to 873 K. Taking into account the two distinct crystallographic sites highlighted, samples possessing two guest elements, one on each site, were then synthesized to improve the thermoelectric properties. A solid solution is found in the system Mn2.7Cr0.3Si4Al2- x In x with x varying from 0 to 0.2. Thus, double-substituted samples were studied by x-ray diffraction, electrical, and thermal measurements. The present paper describes and discusses the experimental results obtained.

  19. Catalytic oxidation of 2-Propanol over (Cr,Mn,Fe)-Pt/gamma-Al2O3 bimetallic catalysts and modeling of experimental results by artificial neural networks.

    PubMed

    Niaei, A; Salari, D; Aghazadeh, F; Caylak, N; Sepehrianazar, A

    2010-01-01

    The catalytic activity of transition metals (Cr,Mn,Fe) supported on the Pt/gamma -Al(2)O(3) industrial catalyst was investigated to bring about the complete oxidation of 2-Propanol. Catalytic studies were carried out under atmospheric pressure in a fixed bed reactor. X-ray diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM) and ICP-AES techniques were used to characterize a series of catalysts. Results showed that the Pt-Mn/gamma -Al(2)O(3) (3.88 wt.%Mn) at calcination temperature of 300 degrees C was the most promising catalyst based on activity, which might be contributed to the quantity of manganese loading, the favorable synergetic effects between Pt and Mn and the well-dispersed bimetallic phase. An artificial neural networks (ANN) model was developed to predict the performance of catalytic oxidation process over Pt-Mn/gamma -Al(2)O(3) bimetallic catalyst based on experimental data. For this purpose the Levenberg-Marquardt (LM) learning algorithm was employed to train the model by using laboratory experimental data. A comparison between the predicted results of the designed ANN model and experimental data was also conducted. The developed model can describe the catalytic oxidation over bimetallic catalysts under different conditions. PMID:20390890

  20. Lunar highland rocks - Element partitioning among minerals. II - Electron microprobe analyses of Al, P, Ca, Ti, Cr, Mn and Fe in olivine

    NASA Technical Reports Server (NTRS)

    Smith, J. V.; Hansen, E. C.; Steele, I. M.

    1980-01-01

    Lunar olivines from anorthosites, granulitic impactites, and rocks in the Mg-rich plutonic trend were subjected to electron probe measurements for Al, P, Ca, Ti, Cr and Mn, which show that the FeO/MnO ratio for lunar olivines lies between 80 and 110 with little difference among the rock types. The low values of Ca in lunar olivines indicate slow cooling to subsolidus temperatures, with blocking temperatures of about 750 C for 67667 and 1000 C for 60255,73-alpha determined by the Finnerty and Boyd (1978) experiments. An important paradox is noted in the low Ti content of Fe-rich olivines from anorthosites, although both Ti and Fe tend to become enriched in liquid during fractional distillation. Except for Ca and Mn, olivine from anorthosites has lower minor element values than other rock types. Formation from a chemically distinct system is therefore implied.

  1. The Mechanical and Corrosion Behaviors of As-cast and Re-melted AlCrCuFeMnNi Multi-Component High-Entropy Alloy

    NASA Astrophysics Data System (ADS)

    Soare, Vasile; Mitrica, Dumitru; Constantin, Ionut; Popescu, Gabriela; Csaki, Ioana; Tarcolea, Mihai; Carcea, Ioan

    2015-04-01

    A multi-component AlCrCuFeMnNi high-entropy alloy, prepared by vacuum induction melting, was investigated for structural, mechanical, and corrosion characteristics, before and after the re-melting process. Optical microscopy analysis revealed a dendritic solidification behavior. The interdendritic area contains two main phases and occasionally small hard phases. The re-melting process produced a finer dendritic structure, with rounded dendrites and reduced interdendritic hard phases. The SEM-EDAX analysis showed that the dendrite region contains a Widmanstatten type of structure and are composed of Cr-Fe rich phases, whereas the interdendrite region contains Cu and Mn rich phases. XRD analysis revealed two disordered BCC type A2 structures with high Cr and Fe content and an FCC A12 type of structure for the Cu and Mn rich interdendritic phase. The lattice constants, determined by X-ray diffraction, are 2.87 and 2.91 Å for the A2 phases and 3.67 Å for A1 phase. The Vickers micro hardness increased with the homogeneity of the alloy, having a maximum value of 4370 MPa for the re-melted sample. Corrosion tests carried out in 3.5 wt pct sodium chloride aerated solution indicated that the corrosion resistance improved with the re-melting process, being 1.5 to 2 times better than that of 304 stainless steel.

  2. Microstructures and Mechanical Performance of Plasma-Nitrided Al0.3CrFe1.5MnNi0.5 High-Entropy Alloys

    NASA Astrophysics Data System (ADS)

    Tang, Wei-Yeh; Chuang, Ming-Hao; Lin, Su-Jien; Yeh, Jien-Wei

    2012-07-01

    This study investigates the effect of plasma nitriding at 798 K (525 °C) on microstructures and the mechanical performance of Al0.3CrFe1.5MnNi0.5 high-entropy alloys (HEAs) obtained using different cast and wrought processing. All the alloys can be well nitride, with a thickness of around 80 μm, and attain a peak hardness level around Hv 1300 near the surface. The main nitride phases are CrN, AlN, and (Mn, Fe)4N. Those of the substrates are bcc, fcc, Al-, and Ni-rich B2 precipitates, and ρ phase. Their relative amounts depend on the prior processing and also change under the heat treatment during nitriding. The formation of ρ phase during nitriding could in-situ harden the substrate to attain the suitable level required for wear applications. This gives the advantage in simplifying the processing for making a wear-resistance component or a mold since austenitizing, quench hardening, and tempering required for steels such as SACM and SKD steels are no longer required and final finishing can be accomplished before nitriding. Nitrided Al0.3CrFe1.5MnNi0.5 samples have much better wear resistance than un-nitrided ones by 49 to 80 times and also exhibit superior adhesive wear resistance to conventional nitrided alloys: nitriding steel SACM-645 (AISI 7140), 316 stainless steel, and hot-mold steel SKD-61 (AISI H13) by 22 to 55 times depending on prior processing. The superiority is due to the fact that the present nitrided alloys possess a much thicker highly hardened layer than the conventional alloys.

  3. Influence of transition metals (Cr, Mn, Fe, Co and Ni) on the methane combustion over Pd/Ce-Zr/Al 2O 3 catalyst

    NASA Astrophysics Data System (ADS)

    Yue, Baohua; Zhou, Renxian; Wang, Yuejuan; Zheng, Xiaoming

    2006-06-01

    The effects of transition metals (Cr, Mn, Fe, Co and Ni) on the catalytic properties of Pd/Ce-Zr/Al 2O 3 catalyst for methane combustion have been investigated. The supported Pd catalysts are characterized by BET, XRD, TEM, TPR, TPO and TPSR measurements. Activity tests in methane combustion show that Pd/Ce-Zr-Ni/Al 2O 3 has the highest catalytic activity and thermal stability among all catalysts. The results of TEM show that the addition of Ni to Pd/Ce-Zr/Al 2O 3 increases the dispersion of Pd component and inhibits the site growth. The results of TPO and TPSR show that the addition of Ni inhibits the decomposition of PdO particles and improves the reduction-reoxidation properties of the active PdO species, which increases the catalytic activity and thermal stability of the Pd/Ce-Zr/Al 2O 3 catalyst.

  4. Specific features of the electrical resistivity of half-metallic ferromagnets Co2 MeAl ( Me = Ti, V, Cr, Mn, Fe)

    NASA Astrophysics Data System (ADS)

    Kourov, N. I.; Perevozchikova, Yu. A.; Weber, H. W.; Marchenkov, V. V.

    2016-07-01

    The transport properties of half-metallic ferromagnetic Heusler alloys Co2 MeAl ( Me = Ti, V, Cr, Mn, Fe are transition 3 d metals) have been measured in the temperature range of 4-900 K. The specific features of the behavior of the resistivity have been considered in the framework of the two-current model of conductivity that takes into account the existence of the energy gap in the electronic spectra of the alloys near the Fermi level of one of electron subbands that differs in the spin direction.

  5. ⁵³Mn-⁵³Cr and ²⁶Al-²⁶Mg ages of a feldspathic lithology in polymict ureilites

    SciTech Connect

    Goodrich, Cyrena Anne; Hutcheon, Ian D.; Kita, Noriko T.; Huss, Gary R.; Cohen, Barbara Anne; Keil, Klaus

    2010-07-01

    We report 53Mn–53Cr and 26Al–26Mg isotopic data, obtained by in-situ SIMS analysis, for feldspathic clasts in polymict ureilites DaG 319 and DaG 165. The analyzed clasts belong to the “albitic lithology,” the most abundant population of indigenous feldspathic materials in polymict ureilites, and are highly fractionated igneous assemblages of albitic plagioclase, Fe-rich pyroxenes, phosphates, ilmenite, silica, and Fe(Mn, K, P, Ti)-enriched glass. Glass in DaG 165 clast 19 has extremely high and variable 55Mn/52Cr ratios (500–58,000) and shows correlated 53Cr excesses up to ~ 1500‰, clearly indicating the presence of live 53Mn at the time of formation. The slope of the well-correlated isochron defined by glass and pyroxenes from this clast corresponds to (53Mn/55Mn) = (2.84 ± 0.10) × 10-6 (2σ). Data for less 55Mn/52Cr-enriched glasses from DaG 319 clast B1, as well as phosphates from several other clasts, are consistent with this isochron. The 53Mn/55Mn ratio obtained from the isochron implies that these clasts are 0.70 ± 0.18 Ma younger than the D'Orbigny angrite, corresponding to the absolute age of 4563.72 ± 0.22 Ma. Plagioclase in DaG 319 clast B1 has a fairly constant 27Al/24Mg ratio of ~ 900 and shows resolvable 26Mg excesses of ~ 2‰. The slope of the isochron defined by pyroxene and plagioclase in this clast is (3.0 ± 1.1) × 10-7 (2σ), corresponding to a time difference of 5.4 (-0.3/+0.5) Ma after CAI (assuming the canonical initial 26Al/27Al ratio of 5 × 10-5) and an age 0.5 (-0.3/+0.5) Ma younger than D'Orbigny. Its absolute age (relative to D'Orbigny) is 4563.9 (+ 0.4/-0.5) Ma, in agreement with the 53Mn–53Cr age from clast 19. These data provide the first high

  6. Characterization of Structural Properties of LiMxFe5-xO8 (M=Al, Cr, Mn) Spinel Solid Solutions

    NASA Astrophysics Data System (ADS)

    Darul, J.

    2008-08-01

    The structural properties of series spinel oxides with the general formula, LiM0.5Fe4.5O8 (M = Mn, Cr, Al), are investigated. The effect of limited substitution of manganese, chromium and aluminum ions in the lithium ferrite samples on the order-disorder phase transition in the spinel crystal lattice at room temperature is presented. In these materials it is found that the ordered structures have not been isolated as single phases under the present experimental conditions and this fact will certainly influence the magnetic behavior of the compounds. The Rietveld refinements of the synchrotron X-ray diffraction data revealed that transition metal ions hinders the ordering process and Al3+ ion was shown to be least effective in removing of order.

  7. Investigation of magnetic properties and electronic structure of layered-structure borides AlT{sub 2}B{sub 2} (T=Fe, Mn, Cr) and AlFe{sub 2–x}Mn{sub x}B{sub 2}

    SciTech Connect

    Chai, Ping; Stoian, Sebastian A.; Tan, Xiaoyan; Dube, Paul A.; Shatruk, Michael

    2015-04-15

    The ternary phases AlT{sub 2}B{sub 2} (T=Fe, Mn, Cr) and quaternary phases AlFe{sub 2–x}Mn{sub x}B{sub 2} have been synthesized by arc-melting and characterized by powder X-ray diffraction, magnetic measurements, Mössbauer spectroscopy, and electronic band structure calculations. All the compounds adopt the AlFe{sub 2}B{sub 2}-type structure, in which infinite zigzag chains of B atoms are connected by Fe atoms into [Fe{sub 2}B{sub 2}] slabs that alternate with layers of Al atoms along the b axis. The magnetic measurements reveal that AlFe{sub 2}B{sub 2} is a ferromagnet with T{sub C}=282 K while AlMn{sub 2}B{sub 2} and AlCr{sub 2}B{sub 2} do not show magnetic ordering in the studied temperature range of 1.8–400 K. A systematic investigation of solid solutions AlFe{sub 2−x}Mn{sub x}B{sub 2} showed a non-linear change in the structural and magnetic behavior. The ferromagnetic ordering temperature is gradually decreased as the Mn content (x) increases. The Mössbauer spectra reveal the presence of non-magnetic (NM) and ferromagnetic (FM) spectral components in all Mn-containing samples, with the amount of NM fraction increasing as the Mn content increases. While for the AlFe{sub 2−x}Mn{sub x}B{sub 2} samples with x=0.0 and 0.4 the hyperfine splitting of the FM spectral component collapses at temperatures close to the Curie temperatures determined from the magnetic measurements, for the x=1.2 and 1.6 samples the FM fraction exhibits a sizable unquenched hyperfine splitting at room temperature, a finding that is inconsistent with the observed magnetic properties. Along with the increase in the amount of the NM fraction, this observation suggests formation of Fe-rich and Mn-rich regions in the structure of the solid solutions. Quantum-chemical calculations and crystal orbital Hamilton population analysis provide a clear explanation of the distinction in properties for this series of compounds and also reveal the importance of electronic factors in modifying the

  8. Influence of deformation on the structure and the mechanical properties of a high-entropy Fe25Cr20Ni20Co10Mn15Al10 alloy

    NASA Astrophysics Data System (ADS)

    Gorban', B. F.; Nazarenko, V. A.; Danilenko, N. I.; Karpets, M. V.; Krapivka, N. A.; Firstov, S. A.; Makarenko, E. S.

    2014-10-01

    The phase composition, the hardness, and the elasticity modulus of a high-entropy Fe25Cr20Ni20Co10Mn15Al10 alloy have been studied in the as-cast state, after rolling deformation, and after subsequent high-temperature annealing. The alloy consists of the following two phases: solid substitutional solutions with bcc and fcc crystal lattices; in the as-cast state and after annealing the bcc solid solution is ordered according to B2 type (CsCl). The mixture rule is applied for the calculation of the electron density, the atomic radius, and the melting point at grain boundaries and in the grain volume of the alloy after deformation and annealing. The obtained data demonstrate that the alloy is thermally stable.

  9. Diffusion kinetics of Cr in spinel: Experimental studies and implications for 53Mn-53Cr cosmochronology

    NASA Astrophysics Data System (ADS)

    Posner, Esther S.; Ganguly, Jibamitra; Hervig, Richard

    2016-02-01

    The 53Mn-53Cr decay system, in which 53Mn decays to 53Cr (t1/2 = 3.7 Ma) has been widely used to construct 53Cr/52Cr vs. 55Mn/52Cr isochrons and thus determine relative ages of early solar system objects or events, assuming that the initial Cr isotopic ratio, (53Cr/52Cr)o, equals (53Mn/52Cr)o. With the primary objective of interpretation of these ages within a diffusion kinetic framework, we have determined the tracer diffusion coefficient of Cr in natural spinels, which are very close to the MgAl2O4 end-member composition, as a function of temperature and oxygen fugacity (f(O2)). It is found that the diffusion coefficient of Cr, D(Cr), in two stocks of spinels (referred to as cut-gems and gem-gravels) with very similar major element chemistry is consistently different, but the data in each stock yield well defined Arrhenius relations that show a difference of log D of 0.6-1.0, depending on temperature, with the D(Cr) in gem-gravel being higher than that in the cut-gem stock. The D(Cr) was found to have a positive dependence on f(O2) in the range of f(O2) of around ±2 log units relative to that of the wüstite-magnetite buffer. The difference in the D(Cr) between the two stocks and the observed D(Cr) vs. f(O2) relation has been explained in terms of a change of point defect concentration resulting from heterovalent substitution of trace elements and equilibration with the imposed f(O2) conditions, respectively. Assuming a homogeneous semi-infinite matrix, the closure temperature (Tc) of Cr diffusion in spinel has been calculated as a function of grain size, cooling rate, peak temperature (To) and f(O2). Also the dependence of D(Cr) and Tc(Cr) on the Cr# (i.e. Cr/(Cr + Al) ratio) has been accounted for using available D(Cr) vs. Cr# data in Suzuki et al. (2008). We argue, on the basis of crystal chemical considerations and available diffusion kinetic data for minerals, that the Tc for Mn should be much lower than that for Cr in spinel, olivine and orthopyroxene, and

  10. Microwave-assisted synthesis: A fast and efficient route to produce LaMO{sub 3} (M = Al, Cr, Mn, Fe, Co) perovskite materials

    SciTech Connect

    Prado-Gonjal, J.; Arevalo-Lopez, A.M.; Moran, E.

    2011-02-15

    Research highlights: {yields} Lanthanum perovskites can be prepared by microwave irradiation in a domestic set-up. {yields} Microwave-assisted synthesis yields well crystallized and pure materials, sometimes nanosized. {yields} Rietveld analysis has been performed to refine the structures. {yields} Magnetic and electric measurements are similar to those previously reported. {yields} Microwave-assisted synthesis is a fast and efficient method for the synthesis of lanthanum perovskites. -- Abstract: A series of lanthanum perovskites, LaMO{sub 3} (M = Al, Cr, Mn, Fe, Co), having important technological applications, have been successfully prepared by a very fast, inexpensive, reproducible, environment-friendly method: the microwave irradiation of the corresponding mixtures of nitrates. Worth to note, the microwave source is a domestic microwave oven. In some cases the reaction takes place in a single step, while sometimes further annealings are necessary. For doped materials the method has to be combined with others such as sol-gel. Usually, nanopowders are produced which yield high density pellets after sintering. Rietveld analysis, oxygen stoichiometry, microstructure and magnetic measurements are presented.

  11. Comparative Study of Absorption Spectra of V2+, Cr3+, and Mn4+ in α-Al2O3 Based on First-Principles Configuration--Interaction Calculations

    NASA Astrophysics Data System (ADS)

    Novita, Mega; Ogasawara, Kazuyoshi

    2012-10-01

    First-principles configuration--interaction (CI) calculations of the multiplet structures and the ground-state (GS) absorption spectra of isoelectronic 3d3 ions such as V2+, Cr3+, and Mn4+ in α-Al2O3 have been performed. The results of the molecular orbital (MO) calculations without lattice-relaxation effect indicated that the GSMOs are not appropriate for the calculation of the absorption spectra in the case of V2+ in α-Al2O3 (α-Al2O3:V2+) due to the strong mixing between the V 3d orbitals and the conduction band. Therefore we investigated the effect of orbital-relaxation by tentatively performing CI calculations using MOs obtained for several excited states and the CI calculation using the MOs in the intermediate t2g{}1.5eg{}1.5 configuration was found to give reasonable theoretical spectra. The theoretical peak energies and the relative peak intensities were improved further for α-Al2O3:V2+ and α-Al2O3:Cr3+ by consideration of energy corrections such as configuration-dependent correction (CDC) and correlation correction (CC). The comparison between the theoretical spectra and the experimental ones indicated that the theoretical spectra were significantly improved for α-Al2O3:V2+ and α-Al2O3:Cr3+ by consideration of the lattice-relaxation effect. As a result, the tendency of the variation of the peak energies among the isoelectronic 3d3 ions was clearly reproduced by the first-principles calculations. It was also found that none of the orbital-relaxation, the lattice-relaxation, CDC, and CC has significant effects on the absorption spectra of Mn4+ in α-Al2O3.

  12. Magnetism of Al-Mn quasicrystals

    SciTech Connect

    Liu, F.; Khanna, S.N.; Magaud, L.; Jena, P. ); de Coulon, V.; Reuse, F. ); Jaswal, S.S.; He, X. ); Cyrot-Lackman, F. )

    1993-07-01

    The effect of symmetry and concentration of Mn on the magnetism of Al-Mn quasicrystals has been investigated through self-consistent density-functional calculations using molecular clusters and supercell band-structure schemes. A single Mn atom surrounded by 54 Al atoms in an icosahedral or a cuboctahedral structure is found to be nonmagnetic. However, as the Mn concentration is increased, moments develop on Mn sites whose magnitude and coupling depend on their location.

  13. Electrochemical and corrosion properties of YNi{sub 2.5}M{sub 0.5} (M = Ni, Al, Fe, Cr, Cu, Co, Mn) hybride-forming alloys

    SciTech Connect

    Korobov, I.I.; Vasina, S.Ya.; Petrii, O.A.

    1995-06-01

    Hydrogen sorption by electrode materials based on YNi{sub 2.5}M{sub 0.5} (M = Ni, Al, Fe, Cr, Co, Cu, Mn) intermetallic compounds (IMC) with Cu and PTFE binders is studied in 1 M NaOH solution. The obtained reversible electrochemical capacities correspond to YNi{sub 2.5}M{sub 0.5}H{sub 1.3-1.7} hybrides which are stable at room temperature and atmospheric pressure. The application of Cu binder allows one to more completely use the material sorption capacity and promotes both extraction and sorption of hydrogen by IMC.

  14. Eutectic equilibria in the quaternary system Fe-Cr-Mn-C

    NASA Technical Reports Server (NTRS)

    Nowotny, H.; Wayne, S.; Schuster, J. C.

    1982-01-01

    The constitution of the quaternary system, Fe-Cr-Mn-C and to a lesser extent of the quinary system, Fe-Cr-Mn-Al-C were examined for in situ composite alloy candidates. Multivariant eutectic compositions were determined from phase equilibria studies wherein M7C3 carbides (approximately 30% by volume) formed from the melt within gamma iron. An extended field of the hexagonal carbide, (Cr, Fe, Mn)7 C3, was found without undergoing transformation to the orthorhombic structure. Increasing stability for this carbide was found for higher ratios of Cr/Fe(+) Cr + Mn. Aluminum additions promoted a ferritic matrix while manganese favored the desired gamma austenitic matrix. In coexistence with the matrix phase, chromium enters preferentially the carbide phase while manganese distributes equally between the gamma matrix and the M7C3 carbide. The composition and lattice parameters of the carbide and matrix phases were determined to establish their respective stabilities.

  15. Magnetic coupling in neutral and charged Cr{sub 2}, Mn{sub 2}, and CrMn dimers

    SciTech Connect

    Desmarais, N.; Reuse, F. A.; Khanna, S. N.

    2000-04-01

    Theoretical ab initio studies of neutral, cationic and anionic Cr{sub 2}, Mn{sub 2}, and CrMn dimers have been carried out to explore the progression of magnetic coupling with the number of electrons. It is shown that while Cr{sub 2} and Cr{sub 2}{sup -} have antiferromagnetically coupled atomic spins, Cr{sub 2}{sup +} has a ferromagnetic ground state closely followed by an antiferromagnetic state. On the other hand, all Mn{sub 2} dimers are ferromagnetic, irrespective of the charge. The neutral CrMn is ferrimagnetic while the charged CrMn are antiferromagnetic. In all cases, the charged dimers are found to be more stable than the neutral ones. The results are compared with available calculations and experiments and the difficulties associated with theoretical description and the experimental interpretations are discussed. (c) 2000 American Institute of Physics.

  16. Nanoparticles of pure and substituted maghemites (gamma-M(x)Fe(2_x)O3 where M = Al, Cr, Mn, Zn and 0 < or = x < or = 1.3): a comparative study.

    PubMed

    Prasad, N K; Gohri, V; Bahadur, D

    2011-03-01

    Magnetic nanoparticles of pure and substituted iron oxides are prepared by single step autocombustion or by wet chemical methods. The nanoparticles prepared by the first process had mixed phase of hematite and maghemite whereas the later essentially gives maghemite phase. XRD patterns and TEM micrographs of the pure and substituted maghemites samples suggest about their monophasic nature and inverse spinel structure. Further, the size of the particles for the above iron oxide samples was found to be in the range of 4 to 30 nm. Saturation magnetization value for the samples was observed to be varying with the type and the amount of substitution. For example, magnetization value initially increased and then decreased for Al- and Mn-substitutions but it continuously decreased for Cr- and Zn-substitutions. Contrary to the saturation magnetization value, the Curie temperature decreased continuously with increased substitutions irrespective of the type of substitutions. Due to higher magnetization value of Mn-substituted maghemite (for x = 0.2, 78 Am2/kg), it has higher heating ability and specific absorption rate compared to Al-substituted maghemite (for x = 0.07, 70 Am2/kg) and pure maghemite (62 Am2/kg). PMID:21449460

  17. CrMn underlayers for CoCrPt thin film media

    SciTech Connect

    Lee, L.L.; Laughlin, D.E.; Lambeth, D.N.

    1998-07-01

    An improved CoCrPt thin film medium or longitudinal magnetic recording which has a coercivity significantly greater than prior CoCrPt thin film media was investigated. A CrMn alloy underlayer was used, instead of the conventional Cr underlayer. A coercivity value of 4,280 Oe was easily reached in a CoCrPt film on a 50 nm thick CrMn underlayer as compared to 2,810 Oe with a pure Cr underlayer. It was found that the coercivity increase due to the Mn addition was realized if the substrates were preheated before the sputtering. Grain boundary interdiffusion of Mn from the underlayer to the magnetic layer may be the cause for the coercivity increase.

  18. Bulk modulus and specific heat of B-site doped (La0.3Pr0.7)0.65Ca0.35Mn1-xBxO3 (B=Fe, Cr, Ru, Al, Ga)

    NASA Astrophysics Data System (ADS)

    Srivastava, Archana; Thakur, Rasna; Gaur, N. K.

    2014-04-01

    Specific heat (Cp) thermal expansion (α) and Bulk modulus (BT) of lightly doped Rare Earth manganites (La0.3Pr0.7)0.65Ca0.35Mn1-xBxO3 (B3+ = Fe3+,Cr3+,Ga3+,Al3+,Ru4+); (0.3Mn0.97Fe0.03O3 as a function of temperature (10K≤T≤ 200K) is found to be in agreement with the published data. The trend of variation of Debye temperature with B-site cationic radius is predicted probably for the first time for the B-site doped rare earth manganites.

  19. Tough cryogenic alloys from the Fe-Mn and Fe-Mn-Cr systems

    NASA Technical Reports Server (NTRS)

    Schanfein, M. J.; Zackay, V. F.; Morris, J. W., Jr.

    1974-01-01

    By adjusting composition, metastable gamma (austenite) and epsilon (hexagonal) martensite may be retained in Fe-Mn and Fe-Mn-Cr alloys and used to impact toughness through the TRIP mechanism. The resulting alloys have excellent toughness at cryogenic temperatures. The best alloys obtained to date are: Fe-20Mn, with sigma (sub y) = 79ksi and K sub IC = 275ksi square root of (in) at 77 K, and Fc-16Mn-8Cr, with sigma sub y = 85ksi and K sub IC = 72ksi square root of (in) at 77 K.

  20. Electronic structure and magnetic properties of RT4Al8 (R = Sc, Y, La, Lu; T = Fe, Mn, Cr) compounds. Hydrostatic pressure effects

    NASA Astrophysics Data System (ADS)

    Zhuravleva, I. P.; Grechnev, G. E.; Panfilov, A. S.; Lyogenkaya, A. A.; Kotlyar, O. V.; Fedorchenko, A. V.; Feher, A.

    2016-06-01

    We present results of theoretical and experimental studies of the electronic structure and magnetic properties of RFe4Al8, RMn4Al8, and RCr4Al8 compounds with nonmagnetic elements R = Sc, Y, La, and Lu. The electron spectrum and field induced magnetic moment, as well as their dependences on the unit cell volume, are calculated for the paramagnetic phase of the RT4Al8 systems. The calculations are supplemented by measurements of the magnetic susceptibility of representative RT4Al8 compounds as a function of temperature and hydrostatic pressure.

  1. The corrosion behavior of Fe-Mn-Al weld metals

    NASA Astrophysics Data System (ADS)

    Aidun, Daryush K.

    2001-02-01

    The corrosion resistance of a newly developed iron-base, Fe-Mn-Al austenitic, and duplex weld metal has been examined in the NACE solution consisting of 5 wt.% NaCl, 0.5 wt.% acetic acid, and the balance distilled water. The electrochemical techniques such as potentiodynamic polarization, Tafel plots, linear polarization, cyclic polarization, and open-circuit potential versus time were employed. The Fe-Mn-Al weld metals did not passivate and exhibited high corrosion rates. Fe-Cr-Ni (310 and 316) weld and base metals were also examined in the NACE solution at room temperature. The 310 and 316 base metals were more resistant to corrosion than the as-welded 310 and 316 weld metals. Postweld heat treatment (PWHT) improved the corrosion performance of the Fe-Mn-Al weld metals. The corrosion resistance of Fe-Mn-Al weld metals after PWHT was still inferior to that of the 310 and 316 weld and base metals.

  2. Magnetic susceptibilities of liquid Cr-Au, Mn-Au and Fe-Au alloys

    SciTech Connect

    Ohno, S.; Shimakura, H.; Tahara, S.; Okada, T.

    2015-08-17

    The magnetic susceptibility of liquid Cr-Au, Mn-Au, Fe-Au and Cu-Au alloys was investigated as a function of temperature and composition. Liquid Cr{sub 1-c}Au{sub c} with 0.5 ≤ c and Mn{sub 1-c}Au{sub c} with 0.3≤c obeyed the Curie-Weiss law with regard to their dependence of χ on temperature. The magnetic susceptibilities of liquid Fe-Au alloys also exhibited Curie-Weiss behavior with a reasonable value for the effective number of Bohr magneton. On the Au-rich side, the composition dependence of χ for liquid TM-Au (TM=Cr, Mn, Fe) alloys increased rapidly with increasing TM content, respectively. Additionally, the composition dependences of χ for liquid Cr-Au, Mn-Au, and Fe-Au alloys had maxima at compositions of 50 at% Cr, 70 at% Mn, and 85 at% Fe, respectively. We compared the composition dependences of χ{sub 3d} due to 3d electrons for liquid binary TM-M (M=Au, Al, Si, Sb), and investigated the relationship between χ{sub 3d} and E{sub F} in liquid binary TM-M alloys at a composition of 50 at% TM.

  3. New series of triple molybdates AgA3R(MoO4)5 (A=Mg, R=Cr, Fe; A=Mn, R=Al, Cr, Fe, Sc, In) with framework structures and mobile silver ion sublattices

    NASA Astrophysics Data System (ADS)

    Kotova, Irina Yu.; Solodovnikov, Sergey F.; Solodovnikova, Zoya A.; Belov, Dmitry A.; Stefanovich, Sergey Yu.; Savina, Aleksandra A.; Khaikina, Elena G.

    2016-06-01

    Triple molybdates AgA3R(MoO4)5 (A=Mg, R=Cr, Fe; A=Mn, R=Al, Cr, Fe, Sc, In) of the NaMg3In(MoO4)5 type were synthesized and single crystals of AgMg3R(MoO4)5 (R=Cr, Fe) were grown. In their structures, the MoO4 tetrahedra, pairs and trimers of edge-shared (Mg, R)O6 octahedra are connected by common vertices to form a 3D framework. Large framework cavities involve Ag+ cations disordered on three nearby positions with CN=3+1 or 4+1. Alternating (Mg, R)O6 octahedra and MoO4 tetrahedra in the framework form quadrangular windows penetrable for Ag+ at elevated temperatures. Above 653-673 K, the newly obtained molybdates demonstrate abrupt reduction of the activation energy to 0.4-0.6 eV. At 773 K, AgMg3Al(MoO4)5 shows electric conductivity 2.5·10-2 S/cm and Ea=0.39 eV compatible with characteristics of the best ionic conductors of the NASICON type.

  4. Mn-Fe base and Mn-Cr-Fe base austenitic alloys

    DOEpatents

    Brager, Howard R.; Garner, Francis A.

    1987-09-01

    Manganese-iron base and manganese-chromium-iron base austenitic alloys designed to have resistance to neutron irradiation induced swelling and low activation have the following compositions (in weight percent): 20 to 40 Mn; up to about 15 Cr; about 0.4 to about 3.0 Si; an austenite stabilizing element selected from C and N, alone or in combination with each other, and in an amount effective to substantially stabilize the austenite phase, but less than about 0.7 C, and less than about 0.3 N; up to about 2.5 V; up to about 0.1 P; up to about 0.01 B; up to about 3.0 Al; up to about 0.5 Ni; up to about 2.0 W; up to about 1.0 Ti; up to about 1.0 Ta; and with the remainder of the alloy being essentially iron.

  5. Mn-Fe base and Mn-Cr-Fe base austenitic alloys

    DOEpatents

    Brager, Howard R.; Garner, Francis A.

    1987-01-01

    Manganese-iron base and manganese-chromium-iron base austenitic alloys designed to have resistance to neutron irradiation induced swelling and low activation have the following compositions (in weight percent): 20 to 40 Mn; up to about 15 Cr; about 0.4 to about 3.0 Si; an austenite stabilizing element selected from C and N, alone or in combination with each other, and in an amount effective to substantially stabilize the austenite phase, but less than about 0.7 C, and less than about 0.3 N; up to about 2.5 V; up to about 0.1 P; up to about 0.01 B; up to about 3.0 Al; up to about 0.5 Ni; up to about 2.0 W; up to about 1.0 Ti; up to about 1.0 Ta; and with the remainder of the alloy being essentially iron.

  6. Uptake of Al, As, Cr, Cd, Cu, Fe, Mn, Ni, Pb, Sr, and Zn in native wheatgrasses, wildryes, and bluegrass on three metal-contaminated soils from Montana

    Technology Transfer Automated Retrieval System (TEKTRAN)

    One of the biggest challenges to successfully phytoremediate contaminated mineland soils is the identification of native plants that possess a broad adaptation to ecological sites and either exclude or uptake heavy metals of interest. This study evaluated forage concentrations of aluminum (Al), ars...

  7. Structure, magnetism, and electron-transport properties of Mn2CrGa-based nanomaterials

    NASA Astrophysics Data System (ADS)

    Zhang, Wenyong; Kharel, Parashu; Skomski, Ralph; Valloppilly, Shah; Li, Xingzhong; Sellmyer, David J.

    2016-05-01

    Mn2CrGa in the disordered cubic structure has been synthesized using rapid quenching and subsequent annealing. The cubic phase transforms to a stable tetragonal phase when a fraction of Cr or Ga is replaced by Pt or Al, respectively. All samples are ferrimagnetic with high Curie temperatures (Tc); Mn2CrGa exhibits the highest Tc of about 813 K. The tetragonal samples have appreciable values of magnetocrystalline anisotropy energy, which leads to an increase in coercivity (Hc) that approaches about 10 kOe in the Pt-doped sample. The Hc linearly increases with a decrease of temperature, concomitant with the anisotropy change with temperature. All samples are metallic and show negative magnetoresistance with room-temperature resistivities on the order of 1 mΩcm. The magnetic properties including high Tc and low magnetic moment suggest that these tetragonal materials have potential for spin-transfer-torque-based devices.

  8. Solid state phase equilibria and intermetallic compounds of the Al-Cr-Ho system

    SciTech Connect

    Pang, Mingjun; Zhan, Yongzhong; Du, Yong

    2013-02-15

    The solid state phase equilibria of the Al-Cr-Ho ternary system at 500 Degree-Sign C were experimentally investigated. The phase relations at 500 Degree-Sign C are governed by 14 three-phase regions, 29 two-phase regions and 15 single-phase regions. The existences of 10 binary compounds and 2 ternary phases have been confirmed. Al{sub 11}Cr{sub 2}, Al{sub 11}Cr{sub 4} and Al{sub 17}Ho{sub 2} were not found at 500 Degree-Sign C. Crystal structures of Al{sub 9}Cr{sub 4} and Al{sub 8}Cr{sub 4}Ho were determined by the Rietveld X-ray powder data refinement. Al{sub 9}Cr{sub 4} was found to exhibit cubic structure with space group I4-bar 3m (no. 217) and lattice parameters a=0.9107(5) nm. Al{sub 8}Cr{sub 4}Ho crystallizes in ThMn{sub 12} structure type with space group I4/mmm (no. 139) and lattice parameters a=0.8909(4) nm, c=0.5120(5) nm. It is concluded that the obtained Al{sub 4}Cr phase in this work should be {mu}-Al{sub 4}Cr by comparing with XRD pattern of the hexagonal {mu}-Al{sub 4}Mn compound. - Graphical abstract: The solid state phase equilibria of the Al-Cr-Ho ternary system at 500 Degree-Sign C. Highlights: Black-Right-Pointing-Pointer Al-Cr-Ho system has been investigated. Black-Right-Pointing-Pointer Al{sub 9}Cr{sub 4} has cubic structure with space group I4-bar 3m. Black-Right-Pointing-Pointer Al{sub 8}Cr{sub 4}Ho crystallizes in ThMn{sub 12} type with space group I4/mmm. Black-Right-Pointing-Pointer Al{sub 4}Cr phase is {mu}-type at 500 Degree-Sign C.

  9. The effect of interstitial carbon on the mechanical properties and dislocation substructure evolution in Fe40.4Ni11.3Mn34.8Al7.5Cr6 high entropy alloys

    DOE PAGESBeta

    Wang, Zhangwei; Baker, Ian; Cai, Zhonghou; Chen, Si; Poplawsky, Jonathan D.; Guo, Wei

    2016-09-01

    A systematic study of the effects of up to 1.1 at. % carbon on the mechanical properties and evolution of the dislocation substructure in a series of a high entropy alloys (HEA) based on Fe40.4Ni11.3Mn34.8Al7.5Cr6 is presented. Transmission electron microscopy (TEM), synchrotron X-ray diffraction (XRD) and atom probe tomography (APT) were used to show that all the alloys are single-phase f.c.c. random solid solutions. The lattice constant, determined from synchrotron XRD measurements, increases linearly with increasing carbon concentration, which leads to a linear relationship between the yield strength and the carbon concentration. The dislocation substructures, as determined by a TEM,more » show a transition from wavy slip to planar slip and, at higher strains, and from cell-forming structure (dislocations cells, cell blocks and dense dislocation walls) to non-cell forming structure (Taylor lattice, microbands and domain boundaries) with the addition of carbon, features related to the increase in lattice friction stress. The stacking fault energy (measured via weak-beam imaging of the separation of dislocation partials) decreases with increasing carbon content, which also contributes to the transition from wavy slip to planar slip. The formation of non-cell forming structure induced by carbon leads to a high degree of strain hardening and a substantial increase in the ultimate tensile strength. In conclusion, the consequent postponement of necking due to the high strain hardening, along with the plasticity accommodation arising from the formation of microbands and domain boundaries, result in an increase of ductility due to the carbon addition.« less

  10. 53Mn-53Cr dating of aqueously formed carbonates in the CM2 lithology of the Sutter's Mill carbonaceous chondrite

    NASA Astrophysics Data System (ADS)

    Jilly, Christine E.; Huss, Gary R.; Krot, Alexander N.; Nagashima, Kazuhide; Yin, Qing-Zhu; Sugiura, Naoji

    2014-11-01

    Radiometric dating of secondary minerals can be used to constrain the timing of aqueous alteration on meteoritic parent bodies. Dolomite is a well-documented secondary mineral in CM chondrites, and is thought to have formed by precipitation from an aqueous fluid on the CM parent body within several million years of accretion. The petrographic context of crosscutting dolomite veins indicates that aqueous alteration occurred in situ, rather than in the nebular setting. Here, we present 53Mn-53Cr systematics for dolomite grains in Sutter's Mill section SM51-1. The Mn-Cr isotope data show well-resolved excesses of 53Cr correlated with 55Mn/52Cr ratio, which we interpret as evidence for the in situ decay of radioactive 53Mn. After correcting for the relative sensitivities of Mn and Cr using a synthetic Mn- and Cr-bearing calcite standard, the data yield an isochron with slope corresponding to an initial 53Mn/55Mn ratio of 3.42 ± 0.86 × 10-6. The reported error includes systematic uncertainty from the relative sensitivity factor. When calculated relative to the U-corrected Pb-Pb absolute age of the D'Orbigny angrite, Sutter's Mill dolomites give a formation age between 4564.8 and 4562.2 Ma (2.4-5.0 Myr after the birth of the solar system). This age is contemporaneous with previously reported ages for secondary carbonates in CM and CI chondrites. Consistent carbonate precipitation ages between the carbonaceous chondrite groups suggest that aqueous alteration was a common process during the early stages of parent body formation, probably occurring via heating from internal 26Al decay. The high-precision isochron for Sutter's Mill dolomite indicates that late-stage processing did not reach temperatures that were high enough to further disturb the Mn-Cr isochron.

  11. High temperature oxidation resistant coatings for the directionally solidified Ni-Nb-Cr-Al eutectic superalloy

    NASA Technical Reports Server (NTRS)

    Strangman, T. E.; Ulion, N. E.; Felten, E. J.

    1977-01-01

    Protective coatings required for the Ni-Nb-Cr-Al directionally solidified eutectic superalloy were developed and evaluated on the basis of oxidation resistance, diffusional stability, thermal fatigue, and creep resistance. NiCrAlY+Pt and NiCrAlY physical vapor-deposition coating systems exhibited the best combination of properties. Burner-rig testing indicated that the useful life of a 127-micron-thick NiCrAlY+Pt coating exceeds 1000 h at 1366 K. Eutectic-alloy creep lives at 1311 K and a stress of 151.7 MN/sq m were greater for NiCrAlY+Pt-coated specimens than for uncoated specimens by a factor of two.

  12. Cr(III) Oxidation Coupled With Microbially-Mediated Mn(II) Oxidation

    SciTech Connect

    Youxian Wu; Baolin Deng

    2006-04-05

    Cr(VI) can be reduced to less toxic and mobile Cr(III) species through abiotic and biological processes. Reductive immobilization of Cr(VI) has been widely explored as a cost effective technology for site remediation; Mn oxides are regarded as primary oxidants for Cr(III) oxidation in the environment; and Generation of Mn oxides from Mn(II) in natural environments is believed to be biologically catalyzed.

  13. Synthesis and characterization of Mn intercalated Mg-Al hydrotalcite.

    PubMed

    Yang, Chengxue; Liao, Libing; Lv, Guocheng; Wu, Limei; Mei, Lefu; Li, Zhaohui

    2016-10-01

    Mn intercalated hydrotalcite was prepared using a reconstruction method. And Mn intercalation was confirmed by XRD, FTIR, and thermal analyses. The different valences of Mn were present as determined by XPS. Calcination slightly promoted the isomorphic replacement of Mn(2+) and Mn(3+) for Mg(2+) and Al(3+), especially the replacement of Mn(2+) for Mg(2+) and Al(3+), and to some extent, reduced Mn intercalation. Ultrasonic treatment significantly increased Mn intercalation in permanganate form (Mn(7+)), and promoted the replacement of Mn(2+) for Mg(2+) and Al(3+). XRF analysis showed that ultrasonic treatment decreased the unbalanced layer charge of Mn intercalated hydrotalcite, while prolonged calcination increased it. These results may provide guidance on the preparation and application of Mn intercalated hydrotalcite. Extended calcination time and ultrasonic vibration increased the interlayer spacing of hydrotalcite, as a result of reduction in layer charge. As the layer charge was not completely balanced after Mn intercalation, a certain amount of CO3(2-) was re-adsorbed into the interlayer space. Mn-hydrotalcites with different layer charges, different contents of Mn with varying valences are expected to have different performances in the process of adsorption, degradation, and catalysis. PMID:27380016

  14. Ternary Borides Cr2AlB2, Cr3AlB4, and Cr4AlB6: The First Members of the Series (CrB2)nCrAl with n = 1, 2, 3 and a Unifying Concept for Ternary Borides as MAB-Phases.

    PubMed

    Ade, Martin; Hillebrecht, Harald

    2015-07-01

    Single crystals of the ternary borides Cr2AlB2, Cr3AlB4, Cr4AlB6, MoAlB, WAlB, Mn2AlB2, and Fe2AlB2 were grown from the elements with an excess of Al. Structures were refined by X-ray methods on the basis of single crystal data. All compounds crystallize in orthorhombic space groups. In each case boron atoms show the typical trigonal prisms BM6. The BM6-units are linked by common rectangular faces forming B-B-bonds. Thus, zigzag chains of boron atoms are obtained for MoAlB, WAlB, and M2AlB2 (M = Cr, Mn, Fe); chains of hexagons for Cr3AlB4; and double chains of hexagons for Cr4AlB6. The same subunits are known for the binary borides CrB, Cr3B4, Cr2B3, and β-WB, too. The boride partial structures are separated by single layers of Al-atoms in the case of the chromium compounds and double layers for WAlB, i.e., W2Al2B2. All crystal structures can be described using a unified building set principle with quadratic 4(4)-nets of metal atoms. The different compositions and crystal structures are obtained by different numbers of metal layers in the corresponding parts according to the formula (MB)2Aly(MB2)x. This principle is an extension of a scheme which was developed for the boridecarbides of niobium. Furthermore, there is a close similarity to the group of ternary carbides MAl(MC)n, so-called MAX-phases. Therefore, they might be named as "MAB-phases". The pronounced two-dimensionality and the mixture of strong covalent and metallic interactions make MAB-phases to promising candidates for interesting material properties. All compositions were confirmed by EDX measurements. Additionally, microhardness measurements were performed. PMID:26069993

  15. Cyclic and isothermal oxidation behavior at 1100 and 1200 C of Ni-20Cr, Ni-20Cr-3Mn, Ni-20Cr-3Si, and Ni-40Cr alloys

    NASA Technical Reports Server (NTRS)

    Lowell, C. E.

    1973-01-01

    Alloys of Ni-20Cr, Ni-20Cr-3Mn, Ni-20Cr-3Si, and Ni-40Cr were cyclically oxidized at 1100 and 1200 C for up to 100 hours. Oxidation behavior was judged by sample thickness and weight change, metallography, diffraction, and microprobe analysis. The least attacked were Ni-40Cr and Ni-20Cr-3Si. The alloy Ni-20Cr-3Mn was much less attacked than Ni-20Cr, but more than the other alloys. The formation of Cr2O3 accounted for the increased resistance of Ni-Cr and Ni-20Cr-3Si, and the formation of MnCr2O4 accounts for the improvement in Ni-20Cr-3mn over Ni-20Cr.

  16. Visible Light-Induced Electron Transfer from Di-mu-oxo Bridged Dinuclear Mn Complexes to Cr Centers in Silica Nanopores

    SciTech Connect

    Frei, Heinz; Weare, Walter W.; Pushkar, Yulia; Yachandra, Vittal K.; Frei, Heinz

    2008-06-03

    The compound (bpy)2MnIII(mu-O)2MnIV(bpy)2, a structural model relevant for the photosynthetic water oxidation complex, was coupled to single CrVI charge-transfer chromophores in the channels of the nanoporous oxide AlMCM-41. Mn K-edge EXAFS spectroscopy confirmed that the di-mu-oxo dinuclear Mn core of the complex is unaffected when loaded into the nanoscale pores. Observation of the 16-line EPR signal characteristic of MnIII(mu-O)2MnIV demonstrates that the majority of the loaded complexes retained their nascent oxidation state in the presence or absence of CrVI centers. The FT-Raman spectrum upon visible light excitation of the CrVI-OII --> CrV-OI ligand-to-metal charge-transfer reveals electron transfer from MnIII(mu-O)2MnIV (Mn-O stretch at 700 cm-1) to CrVI, resulting in the formation of CrV and MnIV(mu-O)2MnIV (Mn-O stretch at 645 cm-1). All initial and final states are directly observed by FT-Raman or EPR spectroscopy, and the assignments corroborated by X-ray absorption spectroscopy measurements. The endoergic charge separation products (DELTA Eo = -0.6 V) remain after several minutes, which points to spatial separation of CrV and MnIV(mu-O)2MnIV as a consequence of hole (OI) hopping as a major contributing mechanism. This is the first observation of visible light-induced oxidation of a potential water oxidation complex by a metal charge-transfer pump in a nanoporous environment. These findings will allow for the assembly and photochemical characterization of well defined transition metal molecular units, with the ultimate goal of performing endothermic, multi-electron transformations that are coupled to visible light electron pumps in nanostructured scaffolds.

  17. Cr(OH)₃(s) Oxidation Induced by Surface Catalyzed Mn(II) Oxidation

    SciTech Connect

    Namgung, Seonyi; Kwon, M.; Qafoku, Nikolla; Lee, Gie Hyeon

    2014-09-16

    This study examined the feasibility of Cr(OH)₃(s) oxidation mediated by surface catalyzed Mn(II) oxidation under common groundwater pH conditions as a potential pathway of natural Cr(VI) contaminations. Dissolved Mn(II) (50 μM) was reacted with or without synthesized Cr(OH)₃(s) (1.0 g/L) at pH 7 – 9 under oxic or anoxic conditions. In the absence of Cr(OH)₃(s), homogeneous Mn(II) oxidation by dissolved O₂ was not observed at pH ≤ 8.0 for 50 d. At pH 9.0, by contrast, dissolved Mn(II) was completely removed within 8 d and precipitated as hausmannite. When Cr(OH)₃(s) was present, this solid was oxidized and released substantial amounts of Cr(VI) as dissolved Mn(II) was added into the suspension at pH ≥ 8.0 under oxic conditions. Our results suggest that Cr(OH)₃(s) was readily oxidized by a newly formed Mn oxide as a result of Mn(II) oxidation catalyzed on Cr(OH)₃(s) surface. XANES analysis of the residual solids after the reaction between 1.0 g/L Cr(OH)₃(s) and 204 μM Mn(II) at pH 9.0 for 22 d revealed that the product of surface catalyzed Mn(II) oxidation resembled birnessite. The rate and extent of Cr(OH)₃(s) oxidation was likely controlled by those of surface catalyzed Mn(II) oxidation as the production of Cr(VI) increased with increasing pH and initial Mn(II) concentrations. This study evokes the potential environmental hazard of sparingly soluble Cr(OH)₃(s) that can be a source of Cr(VI) in the presence of dissolved Mn(II).

  18. Cr Isotopes in Allende Ca-Al-rich Inclusions

    NASA Technical Reports Server (NTRS)

    Bogdanovski, O.; Papanastassiou, D. A.; Wasserburg, G. J.

    2002-01-01

    We have determined Cr isotope compositions in minerals from Allende CAI in order to address the initial 53Mn (half-life 3.7 Ma) abundance in the solar system. Additional information is contained in the original extended abstract.

  19. Investigation of the mechanical properties of FeNiCrMnSi high entropy alloy wear resistant

    NASA Astrophysics Data System (ADS)

    Buluc, G.; Florea, I.; Chelariu, R.; Popescu, G.; Carcea, I.

    2016-06-01

    In this paper we investigated microstructure, hardness and wear resistance for FeNiCrMnAl, high entropy alloy. The FeNiCrMnSi, high entropy alloy was elaborated in a medium induction furnace, by choosing the silicon, as an alliance element within the equi- atomic high entropy alloy, we managed to obtain a dendritic structure, the formation of intermetallic compounds or separated silicon. The medium hardness value of the investigated alloy was 948.33 HV and the medium value of the friction coefficient was 0.6655 in the first 20 seconds and 0.5425 for 1667 seconds. The volume loss of the high entropy alloy FeNiCrMnSi was 0.0557 mm3.

  20. Laves phase in Ti-42Al-10Mn alloy

    SciTech Connect

    Chen, Z.; Jones, I.P.; Small, C.J.

    1996-07-01

    Mn is one of the most effective alloying additions to {gamma}-TiAl titanium aluminide for improving room temperature ductility. The purpose of this investigation as a whole is to study phase relationships in the Mn addition alloys over a wide range of temperatures and to determine the solubilities of Mn in the {gamma} and {alpha}{sub 2} phases in order to explore the potential of Mn additions to {gamma}-TiAl. The aim of this specific paper, however, is to confirm the identify of the ternary Ti{sub 3}Al{sub 3}Mn{sub 2} phase in the Ti-Al-Mn system and to show how to remove it.

  1. Microstructure and mechanical behavior of Fe30Ni 20Mn35Al15 and modified Fe30Ni 20Mn35Al15 alloys

    NASA Astrophysics Data System (ADS)

    Meng, Fanling

    A novel alloy with nominal composition Fe30Ni 20Mn35Al15 has been found to show good room-temperature strength and significant ductility. The current project is to study the wear properties of as-cast Fe30Ni20Mn35Al 15 and discuss the possibility of further improving the mechanical properties of this alloy. The dry sliding wear of as-cast Fe30Ni20Mn 35Al15 was studied in in four different environments, i.e. air, dry oxygen, dry argon and a 4% hydrogen/nitrogen mixture. Two-body and three-body abrasive wear mechanism was found for tests in oxygen-containing environments, while plastic flow mechanisms dominated the wear behavior for tests in argon. Hydrogen embrittlement led to 1000% increase of wear loss by causing more rapid crack nucleation of the asperities. The effects of different additions of chromium (≤ 8 at. %) on both microstructure and fracture behavior of Fe30Ni20Mn 35Al15 were investigated. All alloys consisted of (Ni, Al)-rich B2 and (Fe, Mn)-rich f.c.c. phases with most of the Cr residing in the f.c.c. phase. The addition of 6 at. % Cr not only increased the room temperature ductility, but also completely suppressed the environmental embrittlement observed in the Cr-free alloy at low strain rates. The effects of varying the Al concentration on the microstructures and tensile properties of six two-phase FeNiMnAl alloys with a composition close to Fe30Ni20Mn35Al15 were studied. The increase in f.c.c. volume fraction and f.c.c. lamellar width led to an increase in ductility and a decrease in yield strength. The correlation between the yield stress and f.c.c. lamellar spacing lambda obeyed a Hall-Petch-type relationship, i.e. sigmay=252+0.00027lambda-1, where the units for sigmay and lambda are MPa and meter, respectively. FeNiMnAl alloy with B2 and f.c.c. phases aligned along was reported to show high strength at room temperature. The mechanical properties of Fe 28Ni18Mn33Al21, consisting of (Ni, Al)-enriched B2 and (Fe, Mn)-enriched f.c.c. phases with

  2. Ferromagnetic Fe2CrAl Nanowires

    NASA Astrophysics Data System (ADS)

    Dulal, Rajendra; Dahal, Bishnu; Pegg, Ian L.; Philip, John

    Heusler alloy Fe2CrAl (FCA) nanowires were grown on silicon substrates. Nanowires have diameters in the range 50 to 200 nm and lengths up to 100 µm. They exhibit cubic L21 and A2 type structure with a space group, Pm m. Magnetic characterization reveals that they display ferromagnetic behavior and has a Curie temperature above 400 K. Magnetic behavior of FCA nanowires is different from the reported bulk behavior. Bulk FCA with L21 structure has a Curie temperature around 274 K. National Science Foundation under ECCS-0845501 and NSF-MRI, DMR-0922997.

  3. τ-MnAl with high coercivity and saturation magnetization

    SciTech Connect

    Wei, J. Z.; Song, Z. G.; Yang, Y. B.; Liu, S. Q.; Du, H. L.; Han, J. Z.; Zhou, D.; Wang, C. S.; Yang, Y. C.; Franz, A.; Többens, D.; Yang, J. B.

    2014-12-15

    In this paper, high purity τ-Mn{sub 54}Al{sub 46} and Mn{sub 54−x}Al{sub 46}C{sub x}alloys were successfully prepared using conventional arc-melting, melt-spinning, and heat treatment process. The magnetic and the structural properties were examined using x-ray diffraction (XRD), powder neutron diffraction and magnetic measurements. A room temperature saturation magnetization of 650.5 kAm{sup -1}, coercivity of 0.5 T, and a maximum energy product of (BH){sub max} = 24.7 kJm{sup -3} were achieved for the pure Mn{sub 54}Al{sub 46} powders without carbon doping. The carbon substituted Mn{sub 54−x}Al{sub 46}C{sub x}, however, reveals a lower Curie temperature but similar saturation magnetization as compared to the carbon-free sample. The electronic structure of MnAl shows that the Mn atom possesses a magnetic moment of 2.454 μ{sub B} which results from strong hybridization between Mn-Al and Mn-Mn. We also investigated the volume and c/a ratio dependence of the magnetic moments of Mn and Al. The results indicate that an increase in the intra-atomic exchange splitting due to the cell volume expansion, leads to a large magnetic moment for the Mn atom. The Mn magnetic moment can reach a value of 2.9 μ{sub B} at a volume expansion rate of ΔV/V ≈ 20%.

  4. A first principle study of phase stability, electronic structure and magnetic properties for Co2-xCrxMnAl Heusler alloys

    NASA Astrophysics Data System (ADS)

    Rached, H.; Rached, D.; Khenata, R.; Abidri, B.; Rabah, M.; Benkhettou, N.; Omran, S. Bin

    2015-04-01

    The structural stabilities, electronic and magnetic properties of Co2-xCrxMnAl alloys with (x=0,1 and 2) were investigated using the full-potential linear muffin-tin orbital (FP-LMTO) method, in the framework of the density functional theory (DFT) within the generalized gradient approximation (GGA) for the exchange correlation functional. The ground state properties including lattice parameter, bulk modulus for the two considered crystal structures Hg2CuTi-Type (X-Type) and Cu2MnAl-Type (L21-Type) are calculated. The half-metallicity within ferromagnetic ground state starts to appear in CoCrMnAl and Cr2MnAl. In the objective for the proposition of the new HM-FM in the Full-Heusler alloys, our results classified CoCrMnAl as new HM-FM material with high spin polarization.

  5. Creep and Toughness of Cryomilled NiAl Containing Cr

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. Daniel; Aikin, Beverly; Salem, Jon

    2000-01-01

    NiAl-AlN + Cr composites were produced by blending cryomilled NiAl powder with approx. 10 vol % Cr flakes. In comparison to the as-consolidated matrices, hot isostatically pressed Cr-modified materials did not demonstrate any significant improvement in toughness. Hot extruded NiAl-AlN+10.5Cr, however, possessed a toughness twice that determine for the base NiAl-AlN alloy. Measurement of the 1200 to 1400 K plastic flow properties revealed that the strength of the composites was completely controlled by the properties of the NiAl-AlN matrices. This behavior could be successfully modeled by the Rule-of-Mixtures, where load is shed from the weak Cr to the strong matrix.

  6. Magnetic coupling in ferromagnetic semiconductor (Ga,Mn)As/(Al,Ga,Mn)As bilayers

    NASA Astrophysics Data System (ADS)

    Wang, M.; Wadley, P.; Campion, R. P.; Rushforth, A. W.; Edmonds, K. W.; Gallagher, B. L.; Charlton, T. R.; Kinane, C. J.; Langridge, S.

    2015-08-01

    We report on a study of ferromagnetic semiconductor (Ga,Mn)As/(Al,Ga,Mn)As bilayers using magnetometry and polarized neutron reflectivity (PNR). From depth-resolved characterization of the magnetic structure obtained by PNR, we concluded that the (Ga,Mn)As and (Al,Ga,Mn)As layers have in-plane and perpendicular-to-plane magnetic easy axes, respectively, with weak interlayer coupling. Therefore, the layer magnetizations align perpendicular to each other under low magnetic fields and parallel at high fields.

  7. Magnetic coupling in ferromagnetic semiconductor (Ga,Mn)As/(Al,Ga,Mn)As bilayers

    SciTech Connect

    Wang, M.; Wadley, P.; Campion, R. P.; Rushforth, A. W.; Edmonds, K. W.; Gallagher, B. L.; Charlton, T. R.; Kinane, C. J.; Langridge, S.

    2015-08-07

    We report on a study of ferromagnetic semiconductor (Ga,Mn)As/(Al,Ga,Mn)As bilayers using magnetometry and polarized neutron reflectivity (PNR). From depth-resolved characterization of the magnetic structure obtained by PNR, we concluded that the (Ga,Mn)As and (Al,Ga,Mn)As layers have in-plane and perpendicular-to-plane magnetic easy axes, respectively, with weak interlayer coupling. Therefore, the layer magnetizations align perpendicular to each other under low magnetic fields and parallel at high fields.

  8. Mn-Cr systematics in primitive meteorites: Insights from mineral separation and partial dissolution

    NASA Astrophysics Data System (ADS)

    Göpel, Christa; Birck, Jean-Louis; Galy, Albert; Barrat, Jean-Alix; Zanda, Brigitte

    2015-05-01

    Cr isotopic compositions have been measured on carbonaceous chondrites (CC): Tafassasset, Paris, Niger I, NWA 5958, NWA 8157 and Jbilet Winselwan. In bulk samples, the 54Cr/52Cr ratios (expressed as ε54Cr) range from 0.93 to 1.58 ε units. These values are in agreement with values characteristic for distinct petrologic types. Despite this 54Cr heterogeneity, the variability in the 53Cr/52Cr ratios (expressed as ε53Cr) of 0.2 ε units and the Mn/Cr ratios is consistent with the previous finding of an isochron in the Mn-Cr evolution diagram. The Mn/Cr ratio in CC corresponds to variable abundances of high-T condensate formed and separated at the beginning of the solar system, thus the canonical 53Mn/55Mn ratio can be defined. Based on a consistent chronology for U-Pb and Mn-Cr between the earliest objects formed in the solar nebula and the D'Orbigny angrite we define a canonical 53Mn/55Mn ratio and ε53Cri of 6.8 × 10-6 and -0.177, respectively. The internal Mn/Cr systematics in Tafassasset and Paris were studied by two approaches: leaching technique and mineral separation. Despite variable ε54Cr values (up to >30 ε) linear co-variations were found between ε53Cr and Mn/Cr ratio. The mineral separates as well as the leachates of Tafassasset fall on a common isochron indicating that (1) cooling of the Tafassasset's parent body occurred at 4563.5 ± 0.25 Ma, and that (2) 54Cr is decoupled from the other isotopes even though temperatures >900 °C have been reached during metamorphism. In the case of Paris, the leachates form an alignment with a 53Mn/55Mn ratio higher than the canonical value. This alignment is not an isochron but rather a mixing line. Based on leachates from various CM and CI, we propose the occurrence of three distinct Cr reservoirs in meteoritic material: PURE54, HIGH53 and LOW53 characterized by a ε53Cr and ε54Cr of 0 and 25,000, -2.17 and 8, and 0.5 and -151, respectively. PURE54 has already been described and is carried by highly refractory

  9. Chemically sensitive amorphization process in the nanolaminated Cr2AC (A = Al or Ge) system from TEM in situ irradiation

    NASA Astrophysics Data System (ADS)

    Bugnet, Matthieu; Mauchamp, Vincent; Oliviero, Erwan; Jaouen, Michel; Cabioc'h, Thierry

    2013-10-01

    The effect of 320 keV Xe2+ ion-irradiation in Cr2AlC and Cr2GeC is investigated in situ in the transmission electron microscope. Both compounds amorphize at moderate fluences (1013-1014 Xe cm-2) but exhibit different amorphization mechanisms, bearing witness of the major influence of the chemical composition of the nanolaminated Mn+1AXn phases. It is proposed that amorphization takes place via a direct impact amorphization process in Cr2GeC whereas it is governed by a defect accumulation process in Cr2AlC.

  10. Synthesis and characterization of MnCrO4, a new mixed-valence antiferromagnet.

    PubMed

    Nalbandyan, Vladimir B; Zvereva, Elena A; Yalovega, Galina E; Shukaev, Igor L; Ryzhakova, Anastasiya P; Guda, Alexander A; Stroppa, Alessandro; Picozzi, Silvia; Vasiliev, Alexander N; Whangbo, Myung-Hwan

    2013-10-21

    A new orthorhombic phase, MnCrO4, isostructural with MCrO4 (M = Mg, Co, Ni, Cu, Cd) was prepared by evaporation of an aqueous solution, (NH4)2Cr2O7 + 2 Mn(NO3)2, followed by calcination at 400 °C. It is characterized by redox titration, Rietveld analysis of the X-ray diffraction pattern, Cr K edge and Mn K edge XANES, ESR, magnetic susceptibility, specific heat and resistivity measurements. In contrast to the high-pressure MnCrO4 phase where both cations are octahedral, the new phase contains Cr in a tetrahedral environment suggesting the charge balance Mn(2+)Cr(6+)O4. However, the positions of both X-ray absorption K edges, the bond lengths and the ESR data suggest the occurrence of some mixed-valence character in which the mean oxidation state of Mn is higher than 2 and that of Cr is lower than 6. Both the magnetic susceptibility and the specific heat data indicate an onset of a three-dimensional antiferromagnetic order at TN ≈ 42 K, which was confirmed also by calculating the spin exchange interactions on the basis of first principles density functional calculations. Dynamic magnetic studies (ESR) corroborate this scenario and indicate appreciable short-range correlations at temperatures far above TN. MnCrO4 is a semiconductor with activation energy of 0.27 eV; it loses oxygen on heating above 400 °C to form first Cr2O3 plus Mn3O4 and then Mn1.5Cr1.5O4 spinel. PMID:24090277

  11. Long afterglow properties of Zn2GeO4:Mn2+, Cr3+ phosphor

    NASA Astrophysics Data System (ADS)

    Cong, Yan; He, Yangyang; Dong, Bin; Xiao, Yu; Wang, Limei

    2015-04-01

    Zn2GeO4:Mn2+, Cr3+ phosphors were prepared by conventional solid state reaction and the photoluminescence properties were investigated. The Mn2+ activated Zn2GeO4 phosphors exhibited green emission at 533 nm due to the 4T1(4G) → 6A1(6S) transition of Mn2+ ions. With Cr3+ co-doping in Zn2GeO4 host, long afterglow characteristics were found from the same transition of Mn2+. The TL results revealed the presence of same traps in the phosphor, and the doping of Cr3+ ions deepened the VGe traps. The native defect VGe as a hole traps is responsible for the long afterglow emission in Zn2GeO4:Mn2+, Cr3+ phosphor. The possible mechanism of this phosphor has also been discussed.

  12. Preparation of Al-Cr-Fe Coatings by Heat Treatment of Electrodeposited Cr/Al Composite Coatings

    NASA Astrophysics Data System (ADS)

    Zhang, Min; Chen, Chang'an; Zhang, Guikai; Rao, Yongchu; Ling, Guoping

    Al-Cr-Fe coatings have been widely used in the surface engineering field of materials, due to their excellent corrosion resistance to water vapor and fused salt deposits. In this study, a new two-step approach was developed to prepare Al-Cr-Fe coatings on surfaces of SUS430 stainless steels. First, the Cr/Al composite coatings were prepared by electrodepositing Cr from aqueous solution then electrodepositing Al from AlCl3-1-ethyl-3-methyl-imidazolium chloride (AlCl3-EMIC) ionic liquid on SUS430 stainless steel substrate. In the second, heat treatment of the Cr/Al composite coatings was carried out to acquire Al-Cr-Fe coatings. Effects of the thickness of Cr/Al composite coatings, the time and temperature of heat treatment on composition and phase structure of alloy layers were studied by using scanning electron microscope (SEM), backscattered electron (BSE), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The structure transformation process and formation mechanism of Al-Cr-Fe coatings were discussed.

  13. Towards consistent chronology in the early Solar System: high resolution 53Mn-53Cr chronometry for chondrules.

    SciTech Connect

    Yin, Q; Jacobsen, B; Moynier, F; Hutcheon, I D

    2007-05-02

    New high-precision {sup 53}Mn-{sup 53}Cr data obtained for chondrules extracted from a primitive ordinary chondrite, Chainpur (LL3.4), define an initial {sup 53}Mn/{sup 55}Mn ratio of (5.1 {+-} 1.6) x 10{sup -6}. As a result of this downward revision from an earlier higher value of (9.4 {+-} 1.7) x 10{sup -6} for the same meteorite (Nyquist et al. 2001), together with an assessment of recent literature, we show that a consistent chronology with other chronometers such as the {sup 26}Al-{sup 26}Mg and {sup 207}Pb-{sup 206}Pb systems emerges in the early Solar System.

  14. Electronic structure, magnetism and stability of Co2CrX (X =Al, Ga, In) ab initio study

    NASA Astrophysics Data System (ADS)

    Dahmane, F.; Mesri, D.; Tadjer, A.; Khenata, R.; Benalia, S.; Djoudi, L.; Doumi, B.; Boumia, L.; Aourag, H.

    2016-01-01

    The structural, electronic as well as the magnetic properties of the Co2CrX (X =Al, Ga and In) full-Heusler alloy have been studied using first-principles calculations performed in the framework of density functional theory (DFT) within the generalized gradient approximation (GGA). It was taken into account both possible L21 structures (i.e. Hg2CuTi- and Cu2MnAl-type). Basically, for all compounds, the Cu2MnAl-type structure is energetically more stable than Hg2CuTi-type structure at the equilibrium volume. The electronic structure calculations for Co2CrAl reveal that half-metallic (HM) character in Cu2MnAl-type structure, Co2CrGa show nearly HM behavior and Co2CrIn has a metallic character. The predicted total magnetic moment is 3μB for Co2CrX (X =Al, Ga) which is in good convergence with the Slater-Pauling (SP) rule.

  15. Itinerant magnetism in CaMn2Al10

    NASA Astrophysics Data System (ADS)

    Simonson, Jack; Steinke, Lucia; Zellman, Shelby; Kistner-Morris, Jedediah; Puri, Akshat; Andrews, Evon; Aronson, Meigan

    2015-03-01

    We report the synthesis and basic properties of CaMn2Al10, a new itinerant magnet that is nearly isostructural with the known quantum critical compound YFe2Al10. Magnetic susceptibility measurements performed on single crystals reveal a cusp at 2 K. Electrical resistivity measurements similarly have a maximum at this temperature, and heat capacity measurements show a broad peak with total entropy of ~ 10 % R ln2. These results together with those of neutron diffraction measurements suggest that CaMn2Al10 is weakly magnetic and potentially close to a quantum critical point. Research supported by a DOD National Security Science and Engineering Fellowship via the AFOSR.

  16. The effect of Mn content on magnetism and half-metallicity of off-stoichiometric Co2MnAl

    NASA Astrophysics Data System (ADS)

    Feng, Yu; Zhou, Ting; Chen, Xiaorui; Yuan, Hongkuan; Chen, Hong

    2015-08-01

    Using the first-principles calculations within density functional theory (DFT), we investigate the influence of Mn content on magnetism and half-metallicity of off-stoichiometric Co2MnAl. From our calculation, the Mn-poor structure most likely results from antisite disorders where Mn atoms are partially substituted by Co (CoMn antisite) or Al (AlMn antisite) due to their lower formation energy than the structure missing Mn atom. Besides, the half-metallicity is immune to AlMn antisite, while the impurity Co atom in CoMn antisite is responsible for the dramatic decrease in spin polarization. Besides, in the Mn-rich structure where excess impurity Mn occupy the Co sites, impurity Mn atom exhibits antiparallel coupling with other magnetic atoms, resulting in ferrimagnetism. With increasing of Mn content, the spin polarization of Mn-rich structure increases from 75% to 100%. When Mn content rises up to α = 1.875, the corresponding compound Co1.125 Mn1.875 Al owns the perfect spin polarization and stable half-metallicity due to the reason that its Fermi level is situated nearly in the middle of the spin down gap. Hence, a large tunneling magnetoresistance (TMR) of magnetic tunnel junctions (MTJs) could be obtained by using Mn-rich Co2MnAl electrode. Furthermore, when Mn content reaches up to α = 2, the compound converts to inverse Heusler compound Mn2CoAl with an unique band structure that the conduction and valence band edges of the spin up electrons touch at the Fermi level, it is therefore classified to be spin gapless semiconductors.

  17. Hot Corrosion Performance of AlO-CrO/NiCoCrAlYTa and AlO/NiCoCrAlYTa Coatings Deposited by Atmospheric Plasma Spraying

    NASA Astrophysics Data System (ADS)

    Tao, Chong; Wang, Lei; Cheng, Nailiang; Hu, Hengfa; Liu, Yang; Song, Xiu

    2016-04-01

    AlO-CrO/NiCoCrAlYTa and AlO/NiCoCrAlYTa coatings were deposited on 316L stainless steel substrate using atmospheric plasma spraying, respectively, in order to improve the oxidation and corrosion resistance. The hot corrosion performance of the coatings at 700 and 900 °C were studied, and the detailed microstructures and phase composition of the coatings were analyzed using x-ray diffraction, scanning electron microscope with energy dispersive spectrometer, and transmission electron microscope. The results show that both coatings are structurally featured by slatted layers, consisting of amorphous phase, Cr2O3, Ni3Al, and Al2O3. The hot corrosion resistance of AlO-CrO/NiCoCrAlYTa coating is better than that of AlO/NiCoCrAlYTa coating. This improvement is attributed to lower porosity and more compact Cr2O3 in AlO-CrO/NiCoCrAlYTa coating which performs better than Al2O3 in blocking further inward progress of corrosion and oxidization.

  18. The resistance to cavitation erosion of CrMnN stainless steels

    SciTech Connect

    Fu, W.T.; Jing, T.F.; Zheng, Y.Z.; Yang, Y.B.; Yao, M.

    1998-12-01

    The resistance to cavitation erosion (CE) was measured using a magnetostrictive device and a rotating disk device for some CrMnN stainless steels (Chinese patent ZL 90 1 02197.0). The microstructural changes in the surface layer before and after CE were analyzed by use of Mossbauer spectra. Results show that the resistance to CE of duplex austenitic-martensitic CrMnN stainless steels is much better than that of ZG0Cr13Ni4-6Mo and ZG0Cr16Ni5Mo steel, which are in common use for hydraulic turbine runners. The metastable austenite and its changes in the process of CE are the key factors why the CrMnN stainless steels have excellent resistance to cavitation erosion.

  19. Transport and magnetic properties of the Co2MnSi/Al/Co2MnSi trilayer

    NASA Astrophysics Data System (ADS)

    Yu, H. L.; Zhang, H. B.; Jiang, X. F.; Zheng, Y.; Yang, G. W.

    2012-05-01

    Using density functional theory and non-equilibrium Green's function analysis, we studied the interface structure, interface stability, and magnetic and transport properties of the Co2MnSi/Al/Co2MnSi trilayer. It was found that only the CoCo/Al architecture is thermodynamically stable among four interfacial architectures, CoCo/Al, MnSi/Al, MnMn/Al, and SiSi/Al, and the other interface architectures are not accessible within the limits set under thermodynamic equilibrium with other phases. Calculations of the transmission spectrum, conductance, and resistance-area product showed that the Co2MnSi/Al/Co2MnSi trilayer is a promising candidate for the next-generation of recording sensors in ultrahigh-density hard disks.

  20. Bulk modulus and specific heat of B-site doped (La{sub 0.3}Pr{sub 0.7}){sub 0.65}Ca{sub 0.35}Mn{sub 1−x}B{sub x}O{sub 3} (B=Fe, Cr, Ru, Al, Ga)

    SciTech Connect

    Srivastava, Archana; Thakur, Rasna; Gaur, N. K.

    2014-04-24

    Specific heat (C{sub p}) thermal expansion (α) and Bulk modulus (B{sub T}) of lightly doped Rare Earth manganites (La{sub 0.3}Pr{sub 0.7}){sub 0.65}Ca{sub 0.35}Mn{sub 1−x}B{sub x}O{sub 3} (B{sup 3+} = Fe{sup 3+},Cr{sup 3+},Ga{sup 3+},Al{sup 3+},Ru4+); (0.3Mn{sub 0.97}Fe{sub 0.03}O{sub 3} as a function of temperature (10K≤T≤ 200K) is found to be in agreement with the published data. The trend of variation of Debye temperature with B-site cationic radius is predicted probably for the first time for the B-site doped rare earth manganites.

  1. A transition in the magneto-transport in the L10 MnAl thin films

    NASA Astrophysics Data System (ADS)

    Luo, Linqiang; Lu, Jiwei; Dao, Nam; Cui, Yishen; Wolf, Stuart A.

    2015-03-01

    In this talk we will report on L10 MnAl thin films with perpendicular magnetic anisotropy prepared on single crystal MgO substrates by co-sputtering Mn and Al targets. A Cr seeding layer enabled the epitaxial growth of the MnAl films. The magneto-resistance (MR) of these films was measured using a Hall bar structure. When the external magnetic field was applied perpendicular to the thin film surface, a change of the sign of MR was observed as will be discussed below. Above 175K, a negative magnetoresistance was observed with two maxima occuring at the coercivity fields of the MnAl thin films. Below 175K, the MR became positive, and the MR ratio increased with decreasing temperature. The possible mechanisms for the transition in the MR will be discussed in detail in this talk. They include the effects of inhomogeneity, chemical ordering and the underlying domain structure. The authors gratefully acknowledge financial support provided by INSPIRE program.

  2. Ti-Cr-Al-O Thin Film Resistors

    SciTech Connect

    Jankowski, A F; Hayes, J P

    2002-03-21

    Thin films of Ti-Cr-Al-O are produced for use as an electrical resistor material. The films are rf sputter deposited from ceramic targets using a reactive working gas mixture of Ar and O{sub 2}. Vertical resistivity values from 10{sup 4} to 10{sup 10} Ohm-cm are measured for Ti-Cr-Al-O films. The film resistivity can be design selected through control of the target composition and the deposition parameters. The Ti-Cr-Al-O thin film resistor is found to be thermally stable unlike other metal-oxide films.

  3. Oxidation of Fe-Cr-Al and Fe-Cr-Al-Y Single Crystals

    NASA Astrophysics Data System (ADS)

    Grabke, H. J.; Siegers, M.; Tolpygo, V. K.

    1995-03-01

    Single crystal samples of the alloy Fe-20%Cr-5%Al with and without Y-doping were used to study the "reactive element" (RE) effect, which causes improved oxidation behaviour and formation of a protective Al2O3 layer on this alloy. The oxidation was followed by AES at 10-7 mbar O2 up to about 1000 °C. Most observations were peculiar for this low pO2 environment, but yttrium clearly favors the formation of Al-oxide and stabilizes it also under these conditions, probably by favoring its nucleation. The oxides formed are surface compounds of about monolayer thickness, not clearly related to bulk oxides. Furthermore, the morphologies of oxide scales were investigated by SEM, after oxidation at 1000°C for 100 h at 133 mbar O2. On Fe-Cr-Al the scale is strongly convoluted and tends to spalling, whereas the presence of Y leads to flat scales which are well adherent. This difference is explained by a change in growth mechanism. The tendency for separation of oxide and metal was highest for the samples with low energy metal surface, i.e. (100) and (110), the scale was better adherent on the (111) oriented surface and on the polycrystalline specimen, since in the latter cases the overall energy for scale/metal separation is higher. All observations, from the low and from the high pO2 experiments, are discussed in relation to the approximately ten mechanisms proposed in the literature for explanation of the RE effects.

  4. Preparation, structural and magnetic characterization of DyCrMnO{sub 5}

    SciTech Connect

    Martinez-Lope, M.J.; Retuerto, M. Garcia-Hernandez, M.; Alonso, J.A.

    2009-03-15

    The title compound has been first synthesized by a citrate technique followed by thermal treatments under moderate oxygen pressure conditions, and characterized by X-ray and neutron powder diffraction (NPD) and magnetization measurements. The crystal structure of DyCrMnO{sub 5} has been refined from NPD data in the space group Pbam; a=7.2617(6) A, b=8.5161(6) A, and c=5.7126(5) A at 295 K. This oxide is isostructural with RMn{sub 2}O{sub 5} oxides (R=rare earths) and it contains infinite chains of (Cr, Mn){sup 4+}O{sub 6} octahedra-sharing edges, linked together by (Mn, Cr){sup 3+}O{sub 5} pyramids and DyO{sub 8} units. The high degree of antisite disordering exhibited by DyCrMnO{sub 5} is noteworthy. The octahedral positions are occupied by roughly 50% of Mn and Cr cations, and the pyramidal groups contain two thirds of Mn and one third of Cr cations. We assume that Mn and Cr cations at the octahedral positions exhibit a tetravalent oxidation state, whereas the metals at the pyramidal positions are trivalent, in order to preserve the electroneutrality of this oxide. The susceptibility vs temperature curve of DyCrMnO{sub 5} does not suggest the establishment of a long-range magnetic structure even at low temperatures; the NPD technique does not provide any signal of magnetic ordering, since the reflections do not show any magnetic contribution. - Graphical abstract: DyCrMnO{sub 5} is isostructural with DyMn{sub 2}O{sub 5}, belonging to the Pbam space group. The crystal structure contains infinite chains of edge-sharing Mn{sup 4+}O{sub 6} octahedra, interconnected by dimer units of Cr{sup 3+}O{sub 5} square pyramids. The low-temperature neutron powder diffraction (NPD) patterns do not show any magnetic contribution, indicating that a full long-range magnetic ordering is not established down to low temperature, although the Dy{sup 3+} magnetic moments are susceptible to be polarized by an external magnetic field at the lowest temperature of 5 K.

  5. Microstructure and Magnetic Properties of Bulk Nanocrystalline MnAl

    SciTech Connect

    Chaturvedi, A; Yaqub, R; Baker, I

    2014-01-22

    MnAl is a promising rare-earth free permanent magnet for technological use. We have examined the effects of consolidation by back-pressure, assisted equal channel angular extrusion processing on mechanically-milled, gas-atomized Mn-46% at. Al powder. X-ray diffraction showed both that the extruded rod consisted mostly of metastable tau phase, with some of the equilibrium gamma(2) and beta phases, and that it largely retained the as-milled nanostructure. Magnetic measurements show a coercivity of <= 4.4 kOe and a magnetization at 10 kOe of <= 40 emu/g. In addition, extrusions exhibit greater than 95% of the theoretical density. This study opens a new window in the area of bulk MnAl magnets with improved magnetic properties for technological use.

  6. The influence of cooling rate and Fe/Cr content on the evolution of Fe-rich compounds in a secondary Al-Si-Cu diecasting alloy

    NASA Astrophysics Data System (ADS)

    Fabrizi, A.; Timelli, G.

    2016-03-01

    This study investigates the morphological evolution of primary α-Al(Fe,Mn,Cr)Si phase in a secondary Al-Si-Cu alloy with respect to the initial Fe and Cr contents as well as to the cooling rate. The solidification experiments have been designed in order to cover a wide range of cooling rates, and the Fe and Cr contents have been varied over two levels. Metallographic and image analysis techniques have been used to quantitatively examine the microstructural changes occurring at different experimental conditions. The morphological evolution of the α-Fe phase has been also analysed by observing deep etched samples. By changing the cooling rate, α-Al15(Fe,Mn,Cr)3Si2 dodecahedron crystals, as well as Chinese- script, branched structures and dendrites form, while primary coarse β-Al5(Fe,Mn)Si needles appear in the alloy with the highest Fe content at low cooling rates.

  7. Oxide Transformation in Cr-Mn-Prealloyed Sintered Steels: Thermodynamic and Kinetic Aspects

    NASA Astrophysics Data System (ADS)

    Hryha, Eduard; Nyborg, Lars

    2014-04-01

    The main obstacle for utilization of Cr and Mn as alloying elements in powder metallurgy is their high oxygen affinity leading to oxidation risk during powder manufacturing, handling, and especially during further consolidation. Despite the high purity of the commercially available Cr- and Mn-prealloyed iron powder grades, the risk of stable oxide formation during the sintering process remains. Thermodynamic and kinetic simulation of the oxide formation/transformation on the former powder surface during heating and sintering stages using thermodynamic modeling tools (Thermo-Calc and HSC Chemistry) was performed. Simulation is based on the results from the analysis of amount, morphology, and composition of the oxide phases inside the inter-particle necks in the specimens from interrupted sintering trials utilizing advanced analysis tools (HRSEM + EDX and XPS). The effect of the processing parameters, such as sintering atmosphere composition, temperature profile as well as graphite addition on the possible scenarios of oxide reduction/formation/transformation for Fe-Cr-Mn-C powder systems, was evaluated. Results indicate that oxide transformation occurs in accordance with the thermodynamic stability of oxides as follows: Fe2O3 → FeO → Fe2MnO4 → Cr2FeO4 → Cr2O3 → MnCr2O4 → MnO/MnSiO x → SiO2. Spinel MnCr2O4 was identified as the most stable oxide phase at applied sintering conditions up to 1393 K (1120 °C). Controlled conditions during the heating stage minimize the formation of stable oxide products and produce oxide-free sintered parts.

  8. The Mn-53-Cr-53 System in CAIs: An Update

    NASA Technical Reports Server (NTRS)

    Papanastassiou, D. A.; Wasserburg, G. J.; Bogdanovski, O.

    2005-01-01

    High precision techniques have been developed for the measurement of Cr isotopes on the Triton mass spectrometer, at JPL. It is clear that multiple Faraday cup, simultaneous ion collection may reduce the uncertainty of isotope ratios relative to single Faraday cup ion collection, by the elimination of uncertainties from ion beam instabilities (since ion beam intensities for single cup collection are interpolated in time to calculate isotope ratios), and due to a greatly increased data collection duty cycle, for simultaneous ion collection. Efforts to measure Cr by simultaneous ion collection have not been successful in the past. Determinations on Cr-50-54Cr, by simultaneous ion collection on the Finnigan/ MAT 262 instrument at Caltech, resulted in large variations in extrinsic precision, for normal Cr, of up to 1% in Cr-53/Cr-52 (data corrected for mass fractionation, using Cr-50/Cr-52).

  9. Mechanical Characterization of CrN/CrAlN Multilayer Coatings Deposited by Magnetron Sputtering System

    NASA Astrophysics Data System (ADS)

    Kaouther, Khlifi; Hafedh, Dhiflaoui; Lassaad, Zoghlami; Ahmed, Ben Cheikh Larbi

    2015-10-01

    Chromium-based coatings are deposited on a 100Cr6 (AISI 52100) substrate by a physical vapor deposition magnetron sputtering system. The coatings have different structures, such as a CrN monolayer and CrAlN multilayer. The structural and morphological compositions of the coatings were evaluated using glow discharge optical emission spectroscopy, atomic force microscopy, and cross-sectional scanning electron microscopy. Nano-indentation tests were performed to investigate the mechanical properties. Domes and craters are shown to be uniformly distributed over the entire surfaces of the two coatings. Additionally, the CrN/CrAlN multilayer coating exhibits a rough surface, attractive mechanical properties, a high compressive stress, and a high plastic and elastic deformation resistance. The improvement of the mechanical properties of the CrN/CrAlN coating is mainly attributed to a reduction in the crystallite size. We found that this reduction was related to three factors: (1) the compositional change resulting from the substitution of aluminum for chromium, which can produce a decrease in the interatomic distance; (2) the structure of CrN/CrAlN, which was characterized by grain size refinement; and (3) the high number of interfaces, which explains the widely accepted concept of dislocation blocking by the layer interfaces.

  10. CaMn2Al10: Itinerant Mn magnetism on the verge of magnetic order

    DOE PAGESBeta

    Steinke, L.; Simonson, J. W.; Yin, W. -G.; Smith, G. J.; Kistner-Morris, J. J.; Zellman, S.; Puri, A.; Aronson, M. C.

    2015-07-24

    We report the discovery of CaMn2Al10, a metal with strong magnetic anisotropy and moderate electronic correlations. Magnetization measurements find a Curie-Weiss moment of 0.83μB/Mn, significantly reduced from the Hund's rule value, and the magnetic entropy obtained from specific heat measurements is correspondingly small, only ≈ 9% of Rln2. These results imply that the Mn magnetism is highly itinerant, a conclusion supported by density functional theory calculations that find strong Mn-Al hybridization. Consistent with the layered nature of the crystal structure, the magnetic susceptibility χ is anisotropic below 20 K, with a maximum ratio of χ[010]/χ[001] ≈ 3.5. A strong power-lawmore » divergence χ(T) ~ T–1.2 below 20 K implies incipient ferromagnetic order, an Arrott plot analysis of the magnetization suggests a vanishing low Curie temperature TC ~ 0. Our experiments indicate that CaMn2Al10 is a rare example of a system where the weak and itinerant Mn-based magnetism is poised on the verge of order.« less

  11. CaMn2Al10 : Itinerant Mn magnetism on the verge of magnetic order

    NASA Astrophysics Data System (ADS)

    Steinke, L.; Simonson, J. W.; Yin, W.-G.; Smith, G. J.; Kistner-Morris, J. J.; Zellman, S.; Puri, A.; Aronson, M. C.

    2015-07-01

    We report the discovery of CaMn2Al10 , a metal with strong magnetic anisotropy and moderate electronic correlations. Magnetization measurements find a Curie-Weiss moment of 0.83 μB/Mn , significantly reduced from the Hund's rule value, and the magnetic entropy obtained from specific heat measurements is correspondingly small, only ≈9 % of R ln 2 . These results imply that the Mn magnetism is highly itinerant, a conclusion supported by density functional theory calculations that find strong Mn-Al hybridization. Consistent with the layered nature of the crystal structure, the magnetic susceptibility χ is anisotropic below 20 K, with a maximum ratio of χ[010 ]/χ[001 ]≈3.5 . A strong power-law divergence χ (T ) ˜T-1.2 below 20 K implies incipient ferromagnetic order with a low Curie temperature TC<2 K . Our experiments indicate that CaMn2Al10 is a rare example of a system where the weak and itinerant Mn-based magnetism is poised on the verge of order.

  12. First-principles investigation of the stability of MN and CrMN precipitates under coherency strains in α-Fe (M = V, Nb, Ta)

    NASA Astrophysics Data System (ADS)

    Fors, Dan H. R.; Wahnström, Göran

    2011-06-01

    We perform a systematic ab initio study of the interface energetics of thin coherent rocksalt (nacl) structured MN and tetragonal CrMN films in bcc Fe (M = V, Nb, Ta), motivated by the vital role of MN and CrMN precipitates for the long-term creep resistance in 9%-12%Cr steels. The similarities and differences in the work of separations and the elastic costs for the coherency strains are identified, and the possibility for formation of coherent films are discussed. Our findings provide valuable information of the interface energetics, which in continuation can be combined with thermodynamical modeling to obtain a better understanding of the initial nucleation stage of the MN and CrMN precipitates, and their influence on the long-term microstructural evolution in 9%-12%Cr steels.

  13. TI--CR--AL--O thin film resistors

    DOEpatents

    Jankowski, Alan F.; Schmid, Anthony P.

    2000-01-01

    Thin films of Ti--Cr--Al--O are used as a resistor material. The films are rf sputter deposited from ceramic targets using a reactive working gas mixture of Ar and O.sub.2. Resistivity values from 10.sup.4 to 10.sup.10 Ohm-cm have been measured for Ti--Cr--Al--O film <1 .mu.m thick. The film resistivity can be discretely selected through control of the target composition and the deposition parameters. The application of Ti--Cr--Al--O as a thin film resistor has been found to be thermodynamically stable, unlike other metal-oxide films. The Ti--Cr--Al--O film can be used as a vertical or lateral resistor, for example, as a layer beneath a field emission cathode in a flat panel display; or used to control surface emissivity, for example, as a coating on an insulating material such as vertical wall supports in flat panel displays.

  14. Fretting Wear of Ti-48Al-2Cr-2Nb

    NASA Technical Reports Server (NTRS)

    Miyoshi, Kazuhisa; Lerch, Bradley A.; Draper, Susan L.

    2001-01-01

    An investigation was conducted to examine the wear behavior of gamma titanium aluminide (Ti-48Al-2Cr-2Nb in atomic percent) in contact with a typical nickel-base superalloy under repeated microscopic vibratory motion in air at temperatures from 296-823 K. The surface damage observed on the interacting surfaces of both Ti-48Al-2Cr-2Nb and superalloy consisted of fracture pits, oxides, metallic debris, scratches, craters, plastic deformation, and cracks. The Ti-48Al-2Cr-2Nb transferred to the superalloy at all fretting conditions and caused scuffing or galling. The increasing rate of oxidation at elevated temperatures led to a drop in Ti-48Al-2Cr-2Nb wear at 473 K. Mild oxidative wear was observed at 473 K. However, fretting wear increased as the temperature was increased from 473-823 K. At 723 and 823 K, oxide disruption generated cracks, loose wear debris, and pits on the Ti-48Al-2Cr-2Nb wear surface. Ti-48Al-2Cr-2Nb wear generally decreased with increasing fretting frequency. Both increasing slip amplitude and increasing load tended to produce more metallic wear debris, causing severe abrasive wear in the contacting metals. Keywords

  15. High-temperature oxidation behavior of a wrought Ni-Cr-W-Mn-Si-La alloy

    SciTech Connect

    Tawancy, H.M.

    1996-04-01

    An investigation was carried out to study the kinetics and products of oxidation of a wrought Ni-Cr-W-Mn-Si-La alloy at temperatures in the range of 950 to 1150{degrees}C. Oxidation kinetics were evaluated from measurements of weight change, metal loss, and internal penetration. Analytical electron microscopy, scanning electron microscopy, electron probe microanalysis, and X-ray diffraction were used to characterize the scale microstructure. Initially, La was observed to segregate within a surface layer of about 5 {mu}m thick, which promoted selective oxidation of Cr and Mn. Oxidation kinetics were found to follow a parabolic-rate law with an activation energy of about 232 kJ/mol. During steady-state oxidation, the scale consisted of an inner adherent layer of {alpha}-Cr{sub 2}O{sub 3} modified by the presence of La and Si, and shielded by an outer layer of MnCr{sub 2}O{sub 4}. Most of the La was segregated to grain boundaries of the {alpha}-Cr{sub 2}O{sub 3} scale, however, Si was homogeneously distributed. It was concluded that the characteristic oxidation resistance of the alloy was related to the synergistic effects of Ni and Cr and to the effective minor additions of La, Si, and Mn; however, the useful life of the scale was limited by rupture and surface depletion in Cr, leading to accelerated internal oxidation.

  16. LiCaAl/sub 6/:Cr/sup 3+/

    SciTech Connect

    Payne, S.A.; Chase, L.L.; Newkirk, H.W.; Smith, L.K.; Krupke, W.F. )

    1988-11-01

    The authors report the discovery of a new laser, LiCaAIF/sub 6/:Cr/sup 3/ (Cr/sup 3+/ :LiCAF). The intrinsic (extrapolated maximum) slope efficiency was found to be 67 percent. For comparison, they also measured the intrinsic slope efficiencies of BeAl/sub 2/O/sub 4/:Cr/sup 3+/ (alexandrite), Na/sub 3/Ga/sub 2/Li/sub 3/F/sub 12/:Cr/sup 3+/, and ScBO/sub 3/:Cr/sup 3+/, and obtained values of 65,28, and 26 percent, respectively. The tuning range of LiCaAIF/sub 6/:Cr/sup 3+/ was determined to be at least 720-840 nm. The conventional spectroscopic properties, such as the absorption, emission, and emission lifetimes as a function of temperature, are reported as well.

  17. Mn-Cr Systematics in Sphalerites and Niningerites From Qingzhen and Yamato69001: Implications Regarding Their Formation Histories

    NASA Astrophysics Data System (ADS)

    El Goresy, A.; Wadhwa, M.; Zinner, E. K.; Nagel, H.-J.; Janicke, J.; Crozaz, G.

    1992-07-01

    Recent Cr isotopic measurements of sphalerites and alabandites in three EL3 chondrites MAC88136, MAC88180, and MAC88184 and of sphalerites in the EH4 chondrite Indarch (El Goresy et al., 1992) revealed ^53Cr excesses (^53Cr*), resulting from the in situ decay of ^53Mn (tau(sub)1/2=3.7 Ma), in most grains analysed. However, the initial ^53Mn/^55Mn ratios calculated for these grains were quite variable, and it was concluded that redistribution of ^53Cr* by diffusional processes was the most likely cause for these variations. In a continuation of the previous work (El Goresy et al., 1992), we report new mineral-chemical and Cr-isotopic data for two EH3 chondrites, Qingzhen and Yamato 69001. The distribution of Fe, Mg, and Mn in niningerites and sphalerites occurring in individual sulfide assemblages was determined by electron microprobe analysis. Among the meteorites of the EH3 subgroup, Qingzhen and Yamato 69001 are unique in that niningerites in both meteorites display normal as well as reversed zoning, indicating complex thermal histories (Ehlers and El Goresy, 1988; Lin et al., 1989; Lin, 1991; Nagel, 1991). Niningerites have different MnS contents (9.2-32.6 mol% MnS in Qingzhen vs. 4.2- 6.3 mol% MnS in Yamato 69001), as do the sphalerites (4.0-9.2 mol% MnS in Qingzhen vs. 2.0-3.5 mol% in Yamato 69001). Sphalerites in both meteorites are normally zoned, with 46.0-49.8 mol% FeS in sphalerites from Qingzhen, and 42.3-49.7 mol% FeS in sphalerites from Yamato 69001. The spatial distributions of Fe and Mg in niningerites and of Fe and Mn in sphalerites indicate complex processes that may have occurred before accretion and/or during later metamorphic events in the parent body (El Goresy and Ehlers, 1989; Lin, 1991; Nagel, 1991). Ion microprobe measurements of 6 sphalerites and 3 niningerites in Qingzhen and of 3 sphalerites and 2 niningerites in Yamato 69001 showed that ^55Mn/^52Cr ratios in these sulfide phases are significantly lower than in sphalerites and

  18. AlMn Transition Edge Sensors for Advanced ACTPol

    NASA Astrophysics Data System (ADS)

    Li, Dale; Austermann, Jason E.; Beall, James A.; Becker, Daniel T.; Duff, Shannon M.; Gallardo, Patricio A.; Henderson, Shawn W.; Hilton, Gene C.; Ho, Shuay-Pwu; Hubmayr, Johannes; Koopman, Brian J.; McMahon, Jeffrey J.; Nati, Federico; Niemack, Michael D.; Pappas, Christine G.; Salatino, Maria; Schmitt, Benjamin L.; Simon, Sara M.; Staggs, Suzanne T.; Van Lanen, Jeff; Ward, Jonathan T.; Wollack, Edward J.

    2016-07-01

    Advanced ACTPol (AdvACT) will use an array of multichroic polarization-sensitive AlMn transition edge sensor (TES) bolometers read out through time-division multiplexing. Aluminum doped with a low concentration of manganese can be deposited to a bulk film thickness for a more reliable superconducting critical temperature uniformity compared to thin bilayers. To build the TES, the AlMn alloy is deposited, over Nb wiring, to a specific thickness to set the TES normal resistance. The doping concentration of manganese coarsely defines the TES critical temperature, while a fine tuning is achieved by heating the deposited film to a specific temperature. The TES island is connected to the thermal bath via four silicon-nitride membranes, where their geometry defines the thermal conductance to the temperature of the bath. Lastly, the TES heat capacity is increased by addition of PdAu electrically connected to the AlMn film. Designs and performance characteristics of these AlMn TESs are presented for use in AdvACT.

  19. [XPS and UPS characterization for Cr and Mn in high-temperature oxide films of bulk nanocrystalline 304 stainless steel].

    PubMed

    Xu, Song-Ning; Wang, Sheng-Gang; Han, Hai-Bao; Sun, Nai-Kun

    2013-03-01

    The authors studied the binding energies of valence electrons of two oxide scales, the atomic percentages of Cr and Mn elements in two oxide films, the work function of two oxide films on bulk nanocrystalline 304 stainless steel (BN-SS304) and conventional polycrystalline 304 stainless steel (CP-SS304). BN-SS304 was prepared by severe rolling technique, and the two oxide films were formed in atmosphere at 900 degrees C for 24 hours oxidation on BN-SS304 and CP-SS304 surfaces. In the two oxide films, Cr and Mn elements exist in the forms of Cr3+, Cr0, Mn4+ and Mn0. The atomic percentage ratios of Cr+ / (Cr3+ + Cr0) and Mn4+ / (Mn4+ + Mn0) in the oxide film on BN-SS304 are lower than those in the oxide film on CP-SS304. The interactions of the two oxides and the valence electrons of elements are Mn-O, Cr-O,3d and 4s of Mn0 and Cr0. The binding energies of the valence electrons in the oxide film on BN-SS304 are larger than those in the oxide film on CP-SS304, the work function of the oxide film on BN-SS304 is 0.07 eV larger than that on CP-SS304. PMID:23705465

  20. Influence of FeCrAl Content on Microstructure and Bonding Strength of Plasma-Sprayed FeCrAl/Al2O3 Coatings

    NASA Astrophysics Data System (ADS)

    Zhou, Liang; Luo, Fa; Zhou, Wancheng; Zhu, Dongmei

    2016-02-01

    Low-power plasma-sprayed FeCrAl/Al2O3 composite coatings with 1.5 mm thickness have been fabricated for radar absorption applications. The effects of FeCrAl content on the coating properties were studied. The FeCrAl presents in the form of a few thin lamellae and numerous particles, demonstrating relatively even distribution in all the coatings. Results show that the micro-hardness and porosity decrease with the increase in FeCrAl content. With FeCrAl content increasing from 28 to 47 wt.%, the bonding strength of the coatings with 1.5 mm thickness increases from 10.5 to 27 MPa, and the failure modes are composed of cohesive and adhesive failure, which are ascribed to the coating microstructure and the residual stress, respectively.

  1. Influence of Bulk Chemical Composition on Relative Sensitivity Factors for 55Mn/52Cr by SIMS: Implications for the 53Mn-53Cr Chronometer

    SciTech Connect

    Matzel, J; Jacobsen, B; Hutcheon, I D; Kita, N; Ryerson, F J

    2009-09-09

    The {sup 53}Mn-{sup 53}Cr systematics of meteorite samples provide an important high resolution chronometer for early solar system events. Accurate determination of the initial abundance of {sup 53}Mn ({tau}{sub 1/2} = 3.7 Ma) by secondary ion mass spectrometry (SIMS) is dependent on properly correcting for differing ion yields between Mn and Cr by use of a relative sensitivity factor (RSF). Ideal standards for SIMS analysis should be compositionally and structurally similar to the sample of interest. However, previously published Mn-Cr studies rely on few standards (e.g., San Carlos olivine, NIST 610 glass) despite significant variations in chemical composition. We investigate a potential correlation between RSF and bulk chemical composition by determining RSFs for {sup 55}Mn/{sup 52}Cr in 11 silicate glass and mineral standards (San Carlos olivine, Mainz glasses KL2-G, ML3B-G, StHs6/80-G, GOR128-G, BM90/21-G, and T1-G, NIST 610 glass, and three LLNL pyroxene-composition glasses). All standards were measured on the Cameca ims-3f ion microprobe at LLNL, and a subset were also measured on the Cameca ims-1270 ion microprobe at the Geological Survey of Japan. The standards cover a range of bulk chemical compositions with SiO{sub 2} contents of 40-71 wt.%, FeO contents of 0.05-20 wt.% and Mn/Cr ratios between 0.4 and 58. We obtained RSF values ranging from 0.83 to 1.15. The data obtained on the ims-1270 ion microprobe are within {approx}10% of the RSF values obtained on the ims-3f ion microprobe, and the RSF determined for San Carlos olivine (0.86) is in good agreement with previously published data. The typical approach to calculating an RSF from multiple standard measurements involves making a linear fit to measured {sup 55}Mn/{sup 52}Cr versus true {sup 55}Mn/{sup 52}Cr. This approach may be satisfactory for materials of similar composition, but fails when compositions vary significantly. This is best illustrated by the {approx}30% change in RSF we see between

  2. Experimental Study on Dynamic Mechanical Properties of 30CrMnSiNi2A Steel.

    NASA Astrophysics Data System (ADS)

    Huang, Fenglei; Yao, Wei; Wu, Haijun; Zhang, Liansheng

    2009-06-01

    Under dynamic conditions, the strain-rate dependence of material response and high levels of hydrostatic pressure cause the material behavior to be significantly different from what is observed under quasi-static condition. The curves of stress and strain of 30CrMnSiNi2A steel in different strain rates are obtained with SHPB experiments. Metallographic analyses show that 30CrMnSiNi2A steel is sensitive to strain rate, and dynamic compression leads to shear failure with the angle 45^o as the small carbide which precipitates around grain boundary changes the properties of 30CrMnSiNi2A steel. From the SHPB experiments and quasi-static results, the incomplete Johnson-Cook model has been obtained: σ=[1587+382.5(ɛ^p)^0.245][1+0.017ɛ^*], which can offer parameters for theory application and numerical simulation.

  3. Discontinuous coarsening behavior of Ni(2)MnAl intermetallic compound during isothermal aging treatment of Fe-Mn-Ni-Al alloys.

    PubMed

    Heo, Yoon-Uk; Takeguchi, Masaki; Furuya, Kazuo; Lee, Hu-Chul

    2010-08-01

    The discontinuous reaction of the Ni(2)MnAl intermetallic phase was investigated during the aging of a solution-treated Fe-8.3Mn-8.2Ni-4.2Al alloy. During aging, Ni(2)MnAl lamellae formed at the prior austenite grain boundaries and twin boundaries and grew into the neighboring grains. The presence of continuously precipitated fine Ni(2)MnAl particles before the growth of the discontinuously precipitated lamellae was confirmed by dark-field transmission electron microscopy, and it was concluded that the present reaction is a type of discontinuous coarsening process, alpha' + Ni(2)MnAl (continuous precipitation) --> alpha + Ni(2)MnAl (discontinuous coarsening). The chemical driving force and the reduction of the total coherent strain energy were suggested to be the driving force for the discontinuous coarsening reaction. PMID:20551447

  4. Investigation of Modified Ni-Cr-Mn Base Alloys for SOFC Interconnect Applications

    SciTech Connect

    Yang, Z Gary; Singh, Prabhakar; Stevenson, Jeffry W.; Xia, Gordon

    2006-09-01

    Two Ni-Cr-W-Mn base alloys based on Haynes 230 were developed and evaluated against criteria relevant to SOFC interconnect applications, which included oxidation behavior under SOFC operating conditions, scale electrical conductivity, and thermal expansion. It was found that, similar to the ferritic stainless steel Crofer22 APU, additions of Mn led to the formation of a unique scale that was comprised of a M3O4 (M=Mn, Cr, Ni, …) spinel-rich top layer and Cr2O3-rich sub-layer. The modified alloys demonstrated reasonable oxidation resistance under SOFC operating conditions, though the Mn additions increased the scale growth rate and thus sacrificed to some extent the oxidation resistance of the base alloy (Haynes 230). The formation of a spinel-rich top layer improved the scale conductivity, especially during the early stages of oxidation, but the higher scale growth rate resulted in a higher rate of increase in the area-specific electrical resistance. Due to their FCC crystal structure, the Ni-Cr-W-Mn base alloys demonstrated a CTE that was higher than that of anode-supported cells and candidate ferritic stainless steels such as Crofer22 APU.

  5. Multiferroicity in B-site ordered double perovskite Y2MnCrO6

    NASA Astrophysics Data System (ADS)

    Fang, Yong; Yan, Shi-Ming; Qiao, Wen; Wang, Wei; Wang, Dun-Hui; Du, You-Wei

    2014-11-01

    Double perovskite manganite Y2MnCrO6 ceramic is synthesized and its multiferroic properties are investigated. Novel multiferroic properties are displayed with respect to other multiferroics, such as high ferroelectric phase transition temperature, and the coexistence of ferrimagnetism and ferroelectricity. Moreover, the ferroelectric polarization of Y2MnCrO6 below the magnetic phase temperature can be effectively tuned by an external magnetic field, showing a remarkable magnetoelectric effect. These results open an effective avenue to explore magnetic multiferroics with spontaneous magnetization and ferroelectricity, as well as a high ferroelectric transition temperature.

  6. Mn-53-Cr-53 Systematics of R-Chondrite NWA 753

    NASA Technical Reports Server (NTRS)

    Jogo, K.; Shih, C-Y.; Reese, Y. D.; Nyquist, L. E.

    2006-01-01

    Chondrules and chondrites are interpreted as objects formed in the early solar system, and it is important to study them in order to elucidate its evolution. Here, we report the study of the Mn-Cr systematics of the R-Chondrite NWA753 and compare the results to other chondrite data. The goal was to determine Cr isotopic and age variations among chondrite groups with different O-isotope signatures. The Mn-53-Cr-53 method as applied to individual chondrules [1] or bulk chondrites [2] is based on the assumption that 53Mn was initially homogeneously distributed in that portion the solar nebula where the chondrules and/or chondrites formed. However, different groups of chondrites formed from regions of different O-isotope compositions. So, different types of chondrites also may have had different initial Mn-53 abundances and/or Cr isotopic compositions. Thus, it is important to determine the Cr isotopic systematics among chondrites from various chondrite groups. We are studying CO-chondrite ALH83108 and Tagish Lake in addition to R-Chondrite NWA753. These meteorites have very distinct O-isotope compositions (Figure 1).

  7. Dielectric function of the ferromagnetic semiconductor CdMnCrTe studied by using spectroscopic ellipsometry

    NASA Astrophysics Data System (ADS)

    Hwang, Younghun; Um, Youngho

    2014-11-01

    We describe the pseudo-dielectric function of Cd1- x- y Mn x Cr y Te ferromagnetic semiconductor alloys by using spectroscopic ellipsometry in the 1.0 ~ 6.0 eV spectral range at room temperature. The ellipsometry data include structures that can be attributed to the effects of Cr concentration on the E 0, E 1, E 1 + Δ1, and E 2 critical points. Critical-point (CP) parameters were obtained by fitting standard critical point (SCP) model line shapes to the numerically-calculated second- energy derivatives of ɛ( ω) = ɛ 1( ω) + iɛ 2( ω). The E 0, E 1, E 1 + Δ1, and E 2 energies decreased with Cr content y; this phenomenon is related to the hybridization of the valence and the conduction bands in CdTe with the 3 d states of Mn and Cr.

  8. Mechanism and kinetics of interaction of Fe, Cr, Mo, and Mn atoms with molecular oxygen

    SciTech Connect

    Akhmadov, U.S.; Zaslonko, I.S.; Smirnov, V.N.

    1988-09-01

    By means of resonance atomic absorption in shock waves, rate constants have been measured for the interaction of atoms of a number of transition metals (Fe, Cr, Mo, and Mn) with molecular oxygen. A new method is proposed and used for determining the exponent ..gamma.. in the modified Lambert-Beer law D = element of(ZN)/sup ..gamma../. The bond strength in CrO and MoO molecules has been estimated.

  9. AlMn Transition Edge Sensors for Advanced ACTPol

    NASA Technical Reports Server (NTRS)

    Li, Dale; Austermann, Jason E.; Beall, James A.; Tucker, Daniel T.; Duff, Shannon M.; Gallardo, Patricio A.; Henderson, Shawn W.; Hilton, Gene C.; Ho, Shuay-Pwu; Hubmayr, Johannes; Koopman, Brian J.; McMahon, Jeffrey J.; Nati, Federico; Niemack, Michael D.; Pappas, Christine G.; Salatino, Maria; Schmitt, Benjamin L.; Simon, Sara M.; Staggs, Suzanne T.; Van Lanen, Jeff; Ward, Jonathan T.; Wollack, Edward J.

    2016-01-01

    Advanced ACTPol (Adv ACT) will use an array of multichroic polarization sensitive AIMn transition edge sensor (TES) bolometers read out through time-division multiplexing. Aluminum doped with a low concentration of manganese can be deposited to a bulk film thickness for a more reliable superconducting critical temperature uniformity compared to thin bilayers. To build the TES, the AlMn alloy is deposited, over Nb wiring, to a specific thickness to set the TES normal resistance. The doping concentration of manganese coarsely defines the TES critical temperature, while a fine tuning is achieved by heating the deposited film to a specific temperature. The TES island is connected to the thermal bath via four silicon-nitride membranes, where their geometry defines the thermal conductance to the temperature of the bath. Lastly, the TES heat capacity is increased by addition of PdAu electrically connected to the AlMn film. Designs and performance characteristics of these AlMn TESs are presented for use in AdvACT.

  10. {sup 53}Mn-{sup 53}Cr CHRONOMETRY OF CB CHONDRITE: EVIDENCE FOR UNIFORM DISTRIBUTION OF {sup 53}Mn IN THE EARLY SOLAR SYSTEM

    SciTech Connect

    Yamashita, Katsuyuki; Yamakawa, Akane; Nakamura, Eizo; Maruyama, Seiji

    2010-11-01

    High-precision Cr isotope ratios for chondrules and metal grain separated from CB chondrite Gujba were determined. The {epsilon}{sup 54}Cr values ({epsilon}{sup i}Cr = [({sup i}Cr/{sup 52}Cr){sub sample}/({sup i}Cr/{sup 52}Cr){sub standard} - 1] x 10{sup 4}) for all samples were identical within the analytical uncertainty, with a mean value of +1.29 {+-} 0.02. Uniform {epsilon}{sup 54}Cr signatures of both chondrules and metal grains imply that the Cr isotope systematics of the meteorite was once completely equilibrated. The {epsilon}{sup 53}Cr values of the chondrules and metal grain, on the other hand, display a strong correlation with the {sup 55}Mn/{sup 52}Cr ratio. The {sup 53}Mn/{sup 55}Mn calculated from the slope of the isochron is (3.18 {+-} 0.52) x 10{sup -6}. This corresponds to absolute ages of 4563.7 {+-} 1.2 Ma and 4563.5 {+-} 1.1 Ma using angrites D'Orbigny and LEW 86010, respectively, as time anchors. These ages are consistent with the ages obtained using other short- and long-lived radio nuclides, supporting the uniform distribution of {sup 53}Mn in the early solar nebula.

  11. Synthesis, characterization and electrochemical performance of Al-substituted Li₂MnO₃

    DOE PAGESBeta

    Dhital, Chetan; Huq, Ashfia; Paranthaman, Mariappan Parans; Manivannan, Ayyakkannu; Torres-Castro, Loraine; Shojan, Jifi; Julien, Christian M.; Katiyar, Ram S.

    2015-08-08

    Li2MnO3 is known to be electrochemically inactive due to Mn in tetravalent oxidation state. Several compositions such as Li2MnO3 , Li1.5Al0.17MnO3, Li1.0Al0.33MnO3 and Li0.5Al0.5MnO3 were synthesized by a sol–gel Pechini method. All the samples were characterized with x-ray diffraction, Raman, x-ray photoelectron spectroscopy, scanning electron microscopy, Tap density and BET analyzer. X-ray diffraction patterns indicated the presence of monoclinic phase for pristine Li2MnO3and mixed monoclinic/spinel phases (Li2 - xMn1 - yAlx + yO3 + z) for Al-substituted Li2MnO3compounds. The Al substitution seems to occur both at Li and Mn sites, which could explain the presence of spinel phase. X-ray photoelectronmore » spectroscopy for Mn 2p orbital reveals a significant decrease in binding energy for Li1.0Al0.33MnO3 and Li0.5Al0.5MnO3 compounds. Cyclic voltammetry, charge/discharge cycles and electrochemical impedance spectroscopy were also performed. A discharge capacity of 24 mAh g-1 for Li2MnO3, 68 mAh g-1 for Li1.5Al0.17MnO3, 58 mAh g-1 for Li1.0Al0.33MnO3 and 74 mAh g-1 for Li0.5Al0.5MnO3 were obtained. As a result, aluminum substitutions increased the formation of spinel phase which is responsible for cycling.« less

  12. Mechanical and hardness evaluations of Fe-18Cr-18Mn alloys

    SciTech Connect

    Rawers, J.C.; Duttlinger, N.W.

    2008-01-01

    A series of Fe-18Cr-18Mn-N-C alloys was produced and evaluated to determine their mechanical and hardness properties. In one group, different levels of nitrogen and carbon were added to a base composition of Fe-18Cr-18Mn. The base Fe-18Cr-18Mn alloy had a fcc-bcc duplex microstructure. The addition of nitrogen and carbon stabilised the fcc phase. These alloys had increasing room temperature hardness, strength, and failure energy with increasing interstitial concentrations. At cryogenic and elevated temperatures, these alloys had increasing hardness (and by implication, increased strength) with increasing interstitial concentrations. In a second group, different levels of nitrogen and carbon were added to the base Fe-18Cr-18Mn composition to which minor solid solution additions of silicon, molybdenum, and nickel had been added. Minor alloy additions made only nominal improvement to mechanical and hardness properties. Nitrogen remained interstitial. However, these minor solid solution additions reduced carbon solubility resulting in the formation of M23C6 precipitates that, while increasing alloy hardness and strength, greatly reduced fracture toughness. The present study suggests that replacing nickel with manganese in stainless steels results not only in more economical alloys but also in alloys with higher strength and hardness.

  13. Corrosion Behavior of 35CrMn and Q235 Steel in Simulated Acid Rain Conditions

    NASA Astrophysics Data System (ADS)

    Zuo, Xiu-li; Xiang, Bin; Li, Xing; Wei, Zi-dong

    2012-04-01

    Effects of pH value, chloride ion concentration and alternation of wetting and drying time in acid rain on the corrosion of 35CrMn and Q235 steel were investigated through the measurement of polarization curves, electrochemical impedance spectroscopy, x-ray diffraction, and quantum mechanical calculations. The corrosion rate of 35CrMn and Q235 steel increased with decreasing pH values of the simulated acid rain, whereas the corrosion potential of 35CrMn and Q235 steel became more negative. The impedance became higher and the corrosion rate decreased with increasing test time. The dissolution rate of samples increased with chloride ion concentration. Results suggested that the corrosion rate of 35CrMn steel was obviously lower than that of Q235 steel for a more compact rust, α-FeOOH. Quantum chemical calculations further revealed that the increase in corrosion rate of the steel resulted from pitting corrosion caused by the corrosive chloride ion.

  14. Mn-Cr relative sensitivity factor in ferromagnesian olivines defined for SIMS measurements with a Cameca ims-1280 ion microprobe: Implications for dating secondary fayalite

    NASA Astrophysics Data System (ADS)

    Doyle, Patricia M.; Jogo, Kaori; Nagashima, Kazuhide; Huss, Gary R.; Krot, Alexander N.

    2016-02-01

    systematics of chondritic fayalite (Fa>90) should be determined using standards of similar composition that are measured under the same analytical conditions as the "unknown". The 53Mn-53Cr ages of secondary fayalites (Fa90-100) in the Elephant Moraine (EET) 90161 (L3.05), Vicencia (LL3.2), Asuka 881317 (CV3) and MacAlpine Hills (MAC) 88107 (C3) chondrites (2.4-1.3+1.8 , 4.0-1.1+1.4 , 4.2-0.7+0.8 and 5.1-0.4+0.5 Myrs after CV CAIs, respectively) are ∼3 Myr older when using an RSF measured on a matrix-matched (Fa99) standard, rather than on a San Carlos olivine. The inferred 53Mn-53Cr ages of fayalite formation are consistent with the ages reported for calcites in CM chondrites measured with similarly matrix-matched standards, suggesting an early onset of aqueous alteration on the ordinary and carbonaceous chondrite parent bodies heated by decay of 26Al.

  15. Simulation Study of Al-1Mn/Al-10Si Circular Clad Ingots Prepared by Direct Chill Casting

    NASA Astrophysics Data System (ADS)

    Wu, Li; Kang, Huijun; Chen, Zongning; Fu, Ying; Wang, Tongmin

    2016-02-01

    A modified direct chill casting process based on Novelis FusionTM Technology co-casting process was used recently to prepare Al-1Mn/Al-10Si circular clad ingots. In the current study, a comprehensive simulation model was developed to investigate the direct chill casting process for preparing the Al-1Mn/Al-10Si circular clad ingots, and a parametric study and experimental research of the direct chill casting process was conducted to explore potential success and failure casting conditions. The simulation results revealed the bonding mechanism of the Al-1Mn/Al-10Si interface in the direct chill casting process and identified the effect of certain parameters on casting performance. The results indicated that the effect of casting speed and Al-1Mn casting temperature on the variations of the minimum solid fraction of Al-1Mn at the interface is stronger than that of cooling water flow rate in inner mold, while Al-10Si casting temperature is the weakest of the four casting parameters. The corresponding experimental results verified that Al-1Mn/Al-10Si circular clad ingot with acceptable metallurgical bonding can be successfully prepared by direct chill casting process under the proper casting parameters. The thickness of diffusion zone is about 40 μm, and the fractured position in tensile test was located in the Al-1Mn alloy side which indicated the strength of the interfacial region is higher than that of Al-1Mn alloy.

  16. Effect of Manganese on Microstructures and Solidification Modes of Cast Fe-Mn-Si-Cr-Ni Shape Memory Alloys

    NASA Astrophysics Data System (ADS)

    Peng, Huabei; Wen, Yuhua; Du, Yangyang; Yu, Qinxu; Yang, Qin

    2013-10-01

    We investigated microstructures and solidification modes of cast Fe-(13-27)Mn-5.5Si-8.5Cr-5Ni shape memory alloys to clarify whether Mn was an austenite former during solidification. Furthermore, we examined whether the Creq/Nieq equations (Delong, Hull, Hammer and WRC-1992 equations) and Thermo-Calc software® together with database TCFE6 were valid to predict the solidification modes of cast Fe-(13-27)Mn-5.5Si-8.5Cr-5Ni shape memory alloys. The results have shown that the solidification modes of Fe-(13-27)Mn-5.5Si-8.5Cr-5Ni alloys changed from the F mode to the FA mode with increasing the Mn concentration. Mn is an austenite former during the solidification for the cast Fe-Mn-Si-Cr-Ni shape memory alloys. The Delong, Hull, Hammer, and WRC-1992 equations as well as Thermo-Calc software® together with database TCFE6 are invalid to predict the solidification modes of cast Fe-(13-27)Mn-5.5Si-8.5Cr-5Ni SMAs. To predict the solidification modes of cast Fe-Mn-Si-Cr-Ni alloys, a new Creq/Nieq equation should be developed or the thermodynamic database of Thermo-Calc software® should be corrected.

  17. Naturally Occurring Cr and Ni in the Sacramento Valley: II. Mn Oxides and the Mobility of Cr(VI) and Ni

    NASA Astrophysics Data System (ADS)

    Mills, C. T.; Morrison, J. M.; Goldhaber, M. B.; Foster, A. L.; Wolf, R. E.; Wanty, R. B.

    2007-12-01

    Soil manganese oxides can strongly affect the mobility and redox state of several toxic trace metals. We are studying the biogeochemical origin of Mn oxides and their association with Cr and Ni in soils of the Sacramento Valley, California. Both Cr and Ni are likely derived from ultramafic rocks that underlie Coast Range drainages to the west of the study area. The impact of weathering and erosion of these rocks is evident in the high levels of total Cr (80 to 1420 μg g-1) and nickel (65 to 224 μg g-1) that occur broadly in western Sacramento Valley soils. Although much of the Cr is bound in refractory spinels as Cr(III), some mobilization of Cr is apparent in the coincidence of enriched soils with high contents of Cr(VI) in ground water. Data from the National Water Information System (NWIS) shows 7 of 12 sampled wells within a 600 km2 area in the Sacramento Valley having Cr(VI) concentrations between 60 and 100% of the CA maximum contaminant level for drinking water (50 μg l-1). A 3-meter depth soil profile collected within the lower Putah Creek watershed was examined to investigate processes contributing to the oxidation and mobilization of natural Cr(III). Hydroxylamine hydrochloride-reducible Mn was determined for 8 depth intervals as a measure of manganese oxide occurrence. Concentrations of reducible Mn varied between 360 and 690 μg g-1 with depth and peaked at 2.7 m below the surface. Concentrations of anion exchangeable Cr(VI) were as high as 6 ng g-1 and were positively correlated (r2=0.59; p=0.07) with reducible Mn. Scanning electron microscopy of soil minerals from the 2.9 to 3.0 m interval showed Cr-bearing spinel grains enclosed within Mn oxide micro concretions suggesting a potential mechanism for the oxidation of natural Cr(III) to mobile Cr(VI). Consistent with the known tendency of Ni to sorb on Mn oxides, substantial Ni (13 to 45 μg g-1) was released in the reducible Mn fraction and it strongly correlates (r2=0.76; p=0.005) with reducible Mn

  18. Influence of oxygen partial pressure on the quasi-ternary system Cr-Mn-Ti oxide

    SciTech Connect

    Garcia-Rosales, C.; Schulze, H.A.; Naoumidis, A.; Nickel, H. . Research Centre Juelich)

    1993-11-01

    The quasi-ternary system Cr-Mn-Ti oxide was investigated at 1,000 C under oxygen partial pressures ranging from 0.21 bar to 10[sup [minus]21] bar (1 bar = 10[sup 5] Pa). X-ray diffraction analysis was used to identify phases and determine lattice parameters. The positions of phase boundaries as a function of oxygen partial pressure were measured using the emf method. The spinel MnCr[sub 2]O[sub 4] may be regarded as the most interesting compound in this system. Part of the chromium can be replaced by trivalent titanium at low oxygen partial pressures and by trivalent manganese at high pressures, and the formation of a limited solid solution with the spinel Mn[sub 2]TiO[sub 4] is possible in all cases. As a result, a coherent single-phase spinel region exists over the entire oxygen partial pressure range at 1,000 C.

  19. Characteristics of laser welded wrought Mg-Al-Mn alloy

    SciTech Connect

    Quan Yajie Chen Zhenhua; Yu Zhaohui; Gong Xiaosan; Li Mei

    2008-12-15

    Magnesium alloys have gained increased attention in recent years as a structural metal because of their property merits, which necessitates the development of welding techniques qualified for applications in the aeronautic and automotive industries. Laser welding is known to be an excellent method for joining metals. In this paper, a 3 kW CO{sub 2} laser beam was used to weld the wrought Mg-Al-Mn alloy. The characteristics of the microstructure and the mechanical properties of the joints were analyzed by optical microscopy (OM), energy dispersive spectrometry (EDS), scanning electron microscopy (SEM), tensile testing and hardness testing. The experimental results show that the wrought Mg-Al-Mn alloy can be joined successfully using optimized welding conditions. The results of tensile testing show that the highest ultimate tensile strength (UTS) of the joints is up to 94% of that of the base metal. The base metal consists of a typical rolled structure, the narrow heat affected zone (HAZ) has no obvious grain coarsening, and the fusion zone consists of fine grains with a high density of {gamma}-Mg{sub 17}Al{sub 12} precipitates. The hardness test results indicate that the microhardness in the fusion zone is higher than that of the base metal. The elemental analysis reveals that the Mg content in the weld is lower than that of the base metal, but the Al content is slightly higher.

  20. Sign reversal of magnetization in Mn substituted SmCrO3

    NASA Astrophysics Data System (ADS)

    Dash, Bibhuti B.; Ravi, S.

    2016-05-01

    Single phase samples of orthorhombic SmCr1-xMnxO3 compounds were prepared for x=0 to 0.50. Analysis of X-ray diffraction patterns shows a systematic increase in lattice parameters with increase in Mn concentration. The phenomenon of magnetization reversal is observed for x=0.10-0.30 samples with a maximum magnetic compensation temperature of 126 K. The mechanism of magnetization reversal is explained by considering the competition between the paramagnetic moments of Mn3+ and Sm3+ ions under the influence of negative internal field due to antiferromagnetically ordered Cr3+ ions and the canted ferromagnetic component of Cr3+ ions. For x≥0.40, the samples exhibit ferromagnetic like behavior.

  1. Hydrogen permeation characteristics of some Fe-Cr-Al alloys

    NASA Astrophysics Data System (ADS)

    Van Deventer, E. H.; Maroni, V. A.

    1983-01-01

    Hydrogen permeation data are reported for two Fe-Cr-Al alloys, Type-405 SS (Cr 14-A1 0.2) and a member of the Fecralloy family of alloys (Cr 16-A1 5). The hydrogen permeability of each alloy (in a partially oxidized condition) was measured over a period of several weeks at randomly selected temperatures (between 150 and 850°C) and upstream H 2 pressures (between 2 and 1.5 × 10 4 Pa). The permeabilities showed considerable scatter with both time and temperature and were 10 2 to 10 3 times lower than those of pure iron, even in strongly reducing environments. The exponent, n, for the relationship between upstream H 2 pressure, P, and permeability, φ, ( φ ~ Pn) was closer to 0.7 than to the expected 0.5, indicating a process limited by surface effects (e.g., surface oxide films) as opposed to bulk material effects. Comparison of these results with prior permeation measurements on other Fe-Cr-Al alloys, on Fe-Cr alloys, and on pure iron shows that the presence of a few weight percent aluminum offers the best prospects for achieving low tritium permeabilities with martensitic and ferritic steels used in fusion-reactor first wall and blanket applications.

  2. Thermodynamic Assessment of the Aluminum Corner of the Al-Fe-Mn-Si System

    NASA Astrophysics Data System (ADS)

    Lacaze, Jacques; Eleno, Luiz; Sundman, Bo

    2010-09-01

    A new assessment of the aluminum corner of the quaternary Al-Fe-Mn-Si system has been made that extends beyond the COST-507 database. This assessment makes use of a recent, improved description of the ternary Al-Fe-Si system. In the present work, modeling of the Al-rich corner of the quaternary Al-Fe-Mn-Si system has been carried out by introducing Fe solubility into the so-called alpha-AlMnSi and beta-AlMnSi phases of the Al-Mn-Si system. A critical review of the data available on the quaternary system is presented and used for the extension of the description of these ternary phases into the quaternary Al-Fe-Mn-Si.

  3. Precipitation Strengthening in Al-Ni-Mn Alloys

    NASA Astrophysics Data System (ADS)

    Fan, Yangyang; Huang, Kai; Makhlouf, Makhlouf M.

    2015-12-01

    Precipitation hardening of eutectic and hypoeutectic Al-Ni alloys by 2 to 4 wt pct. manganese is investigated with focus on the effect of the alloys' chemical composition and solidification cooling rate on microstructure and tensile strength. Within the context of the investigation, mathematical equations based on the Orowan Looping strengthening mechanism were used to calculate the strengthening increment contributed by each of the phases present in the aged alloy. The calculations agree well with measured values and suggest that the larger part of the alloy's yield strength is due to the Al3Ni eutectic phase, this is closely followed by contribution from the Al6Mn particles, which precipitate predominantly at grain boundaries.

  4. Some TEM observations of Al2O3 scales formed on NiCrAl alloys

    NASA Technical Reports Server (NTRS)

    Smialek, J.; Gibala, R.

    1979-01-01

    The microstructural development of Al2O3 scales on NiCrAl alloys has been examined by transmission electron microscopy. Voids have been observed within grains in scales formed on a pure NiCrAl alloy. Both voids and oxide grains grew measurably with oxidation time at 1100 C. The size and amount of porosity decreased towards the oxide-metal growth interface. It was postulated that the voids resulted from an excess number of oxygen vacancies near the oxide-metal interface. Short-circuit diffusion paths were discussed in reference to current growth stress models for oxide scales. Transient oxidations of pure, Y-doped, and Zr-doped NiCrAl was also examined. Oriented alpha-(Al,Cr)2O3 and Ni(Al,Cr)2O4 scales often coexisted in layered structures on all three alloys. Close-packed oxygen planes and directions in the corundum and spinel layers were parallel. The close relationships between oxide layers provided a gradual transition from initial transient scales to steady state Al2O3 growth.

  5. Some TEM observations of Al2O3 scales formed on NiCrAl alloys

    NASA Technical Reports Server (NTRS)

    Smialek, J.; Gibala, R.

    1979-01-01

    The microstructural development of Al2O3 scales on NiCrAl alloys has been examined by transmission electron microscopy. Voids were observed within grains in scales formed on a pure NiCrAl alloy. Both voids and oxide grains grew measurably with oxidation time at 1100 C. The size and amount of porosity decreased towards the oxide-metal growth interface. The voids resulted from an excess number of oxygen vacancies near the oxidemetal interface. Short-circuit diffusion paths were discussed in reference to current growth stress models for oxide scales. Transient oxidation of pure, Y-doped, and Zr-doped NiCrAl was also examined. Oriented alpha-(Al, Cr)2O3 and Ni(Al, Cr)2O4 scales often coexisted in layered structures on all three alloys. Close-packed oxygen planes and directions in the corundum and spinel layers were parallel. The close relationship between oxide layers provided a gradual transition from initial transient scales to steady state Al2O3 growth.

  6. XPS and EELS characterization of Mn2SiO4, MnSiO3 and MnAl2O4

    NASA Astrophysics Data System (ADS)

    Grosvenor, A. P.; Bellhouse, E. M.; Korinek, A.; Bugnet, M.; McDermid, J. R.

    2016-08-01

    X-ray Photoelectron Spectroscopy (XPS) and Electron Energy Loss Spectroscopy (EELS) are strong candidate techniques for characterizing steel surfaces and substrate-coating interfaces when investigating the selective oxidation and reactive wetting of advanced high strength steels (AHSS) during the continuous galvanizing process. However, unambiguous identification of ternary oxides such as Mn2SiO4, MnSiO3, and MnAl2O4 by XPS or EELS, which can play a significant role in substrate reactive wetting, is difficult due to the lack of fully characterized standards in the literature. To resolve this issue, samples of Mn2SiO4, MnSiO3 and MnAl2O4 were synthesized and characterized by XPS and EELS. The unique features of the XPS and EELS spectra for the Mn2SiO4, MnSiO3 and MnAl2O4 standards were successfully derived, thereby allowing investigators to fully differentiate and identify these oxides at the surface and subsurface of Mn, Si and Al alloyed AHSS using these techniques.

  7. Spin dependent transport properties of Mn-Ga/MgO/Mn-Ga magnetic tunnel junctions with metal(Mg, Co, Cr) insertion layer

    SciTech Connect

    Liang, S. H.; Tao, L. L.; Liu, D. P. Han, X. F.; Lu, Y.

    2014-04-07

    We report a first principles theoretical investigation of spin polarized quantum transport in Mn{sub 2}Ga/MgO/Mn{sub 2}Ga and Mn{sub 3}Ga/MgO/Mn{sub 3}Ga magnetic tunneling junctions (MTJs) with the consideration of metal(Mg, Co, Cr) insertion layer effect. By changing the concentration of Mn, our calculation shows a considerable disparity in transport properties: A tunneling magnetoresistance (TMR) ratio of 852% was obtained for Mn{sub 2}Ga-based MTJs, however, only a 5% TMR ratio for Mn{sub 3}Ga-based MTJs. In addition, the influence of insertion layer has been considered in our calculation. We found the Co insertion layer can increase the TMR of Mn{sub 2}Ga-based MTJ to 904%; however, the Cr insertion layer can decrease the TMR by 668%; A negative TMR ratio can be obtained with Mg insertion layer. Our work gives a comprehensive understanding of the influence of different insertion layer in Mn-Ga based MTJs. It is proved that, due to the transmission can be modulated by the interfacial electronic structure of insertion, the magnetoresistance ratio of Mn{sub 2}Ga/MgO/Mn{sub 2}Ga MTJ can be improved by inserting Co layer.

  8. Redox Dynamics of Mixed Metal (Mn, Cr, and Fe) Ultrafine Particles

    PubMed Central

    Nico, Peter S.; Kumfer, Benjamin M.; Kennedy, Ian M.; Anastasio, Cort

    2008-01-01

    The impact of particle composition on metal oxidation state, and on changes in oxidation state with simulated atmospheric aging, are investigated experimentally in flame-generated nanoparticles containing Mn, Cr, and Fe. The results demonstrate that the initial fraction of Cr(VI) within the particles decreases with increasing total metal concentration in the flame. In contrast, the initial Mn oxidation state was only partly controlled by metal loading, suggesting the importance of other factors. Two reaction pathways, one reductive and one oxidative, were found to be operating simultaneously during simulated atmospheric aging. The oxidative pathway depended upon the presence of simulated sunlight and O3, whereas the reductive pathway occurred in the presence of simulated sunlight alone. The reductive pathway appears to be rapid but transient, allowing the oxidative pathway to dominate with longer aging times, i.e. greater than ∼8 hours. The presence of Mn within the particles enhanced the importance of the oxidative pathway, leading to more net Cr oxidation during aging implying that Mn can mediate oxidation by removal of electrons from other particulate metals. PMID:20046215

  9. Redox Dynamics of Mixed Metal (Mn, Cr, and Fe) Ultrafine Particles

    SciTech Connect

    Nico, Peter S.; Kumfer, Benjamin M.; Kennedy, Ian M.; Anastasio, Cort

    2008-08-01

    The impact of particle composition on metal oxidation state, and on changes in oxidation state with simulated atmospheric aging, are investigated experimentally in flame-generated nanoparticles containing Mn, Cr, and Fe. The results demonstrate that the initial fraction of Cr(VI) within the particles decreases with increasing total metal concentration in the flame. In contrast, the initial Mn oxidation state was only partly controlled by metal loading, suggesting the importance of other factors. Two reaction pathways, one reductive and one oxidative, were found to be operating simultaneously during simulated atmospheric aging. The oxidative pathway depended upon the presence of simulated sunlight and O{sub 3}, whereas the reductive pathway occurred in the presence of simulated sunlight alone. The reductive pathway appears to be rapid but transient, allowing the oxidative pathway to dominate with longer aging times, i.e. greater than {approx}8 hours. The presence of Mn within the particles enhanced the importance of the oxidative pathway, leading to more net Cr oxidation during aging implying that Mn can mediate oxidation by removal of electrons from other particulate metals.

  10. Precipitation and fracture behaviour of Fe-Mn-Ni-Al alloys

    NASA Astrophysics Data System (ADS)

    Heo, Yoon-Uk; Lee, Hu-Chul

    2013-12-01

    The effects of Al addition on the precipitation and fracture behaviour of Fe-Mn-Ni alloys were investigated. With the increasing of Al concentration, the matrix and grain boundary precipitates changed from L10 θ-MnNi to B2 Ni2MnAl phase, which is coherent and in cube-to-cube orientation relationship with the α‧-matrix. Due to the suppression of the θ-MnNi precipitates at prior austenite grain boundaries (PAGBs), the fracture mode changed from intergranular to transgranular cleavage fracture. Further addition of Al resulted in the discontinuous growth of Ni2MnAl precipitates in the alloy containing 4.2 wt.% Al and fracture occurred by void growth and coalescence, i.e. by ductile dimple rupture. The transition of the fracture behaviour of the Fe-Mn-Ni-Al alloys is discussed in relation to the conversion of the precipitates and their discontinuous precipitation behaviour at PAGBs.

  11. Reversing ferroelectric polarization in multiferroic DyMn{sub 2}O{sub 5} by nonmagnetic Al substitution of Mn

    SciTech Connect

    Zhao, Z. Y.; Liu, M. F.; Li, X.; Wang, J. X.; Yan, Z. B.; Wang, K. F.; Liu, J.-M.

    2014-08-07

    The multiferroic RMn{sub 2}O{sub 5} family, where R is rare-earth ion or Y, exhibits rich physics of multiferroicity which has not yet well understood. DyMn{sub 2}O{sub 5} is a representative member of this family. The ferroelectric polarization of DyMn{sub 2}O{sub 5} is claimed to be magnetically relevant and have more than one component. Therefore, the polarization reversal upon the sequent magnetic transitions is expected. We investigate the evolution of the ferroelectric polarization upon a partial substitution of Mn{sup 3+} by nonmagnetic Al{sup 3+} in order to tailor the Mn{sup 3+}-Mn{sup 4+} interactions and then to modulate the polarization in DyMn{sub 2−x/2}Al{sub x/2}O{sub 5}. It is revealed that the polarization can be successfully reversed by Al-substitution via substantially suppressing the Mn{sup 3+}-Mn{sup 4+} interactions, while the Dy{sup 3+}-Mn{sup 4+} interactions can sustain against the substitution until a level as high as x = 0.2. In addition, the independent Dy spin ordering is shifted remarkably down to an extremely low temperature due to the Al{sup 3+} substitution. The present work unveils the possibility of tailoring the Mn{sup 3+}-Mn{sup 4+} and Dy{sup 3+}-Mn{sup 4+} interactions independently, and thus reversing the ferroelectric polarization.

  12. Quantum Chemical Design of Doped Ca2MnAlO(5+δ) as Oxygen Storage Media.

    PubMed

    Ling, Chen; Zhang, Ruigang; Jia, Hongfei

    2015-07-01

    Brownmillerite Ca2MnAlO5 has an exceptional capability to robustly adsorb half-molecules of oxygen and form Ca2MnAlO5.5. To utilize this unique property to regulate oxygen-involved reactions, it is crucial to match the oxygen release-intake equilibrium with targeted reaction conditions. Here we perform a comprehensive investigation of the strategy of tuning the oxygen storage property of Ca2MnAlO5 through chemical doping. For undoped Ca2MnAlO5+δ, our first-principles calculation predicts that the equilibrium temperature at a pressure of 1 atm of O2 is 848 K, which is in excellent agreement with experimental results. Furthermore, the doping of alkaline earth ions at the Ca site, trivalent ions at the Al site, and 3d transition metal ions at the Mn site is analyzed. By the doping of 12.5% of Ga, V, and Ti, the equilibrium temperature shifts to high values by approximately 110-270 K, while by the doping of 12.5% of Fe, Sr, and Ba, the equilibrium temperature is lowered by approximately 20-210 K. The doping of these elements is thermodynamically stable, and doping other elements including Mg, Sc, Y, Cr, Co, and Ni generates metastable compounds. The doping of a higher content of Fe, however, lowers the oxygen storage capacity. Finally, on the basis of our calculated data, we prove that the formation energetics of nondilute interacting oxygen vacancy in doped Ca2MnAlO5.5 scale linearly with a simple descriptor, the oxygen p-band position relative to the Fermi level. The higher-oxygen p-band position leads to a lower vacancy formation energy and thus a lower oxygen release temperature. Understanding such a relationship between fundamental quantum chemical properties and macroscopic properties paves the road to the design and optimization of novel functional oxides. PMID:26066573

  13. Adherent Al2O3 scales formed on undoped NiCrAl alloys

    NASA Technical Reports Server (NTRS)

    Smialek, James L.

    1987-01-01

    Changes in the spalling behavior of Al2O3 scales formed on an undoped NiCrAl alloy are described. Two samples of Ni-15Cr-13Al (wt pct), one a control and the other sanded, were subjected to 25 oxidation cycles. It is observed that adherent scales formed on the sanded sample; however, the control sample had speckled, spalled scales. The data reveal that the adherent scales are caused by repeated removal of surface layers after each oxidation cycle. It is determined that interfacial segregation of sulfur influences spallation and sulfur removal increases bonding. The effect of moisture on scale adhesions is investigated.

  14. Temporal evolution of ion energy distribution functions and ion charge states of Cr and Cr-Al pulsed arc plasmas

    SciTech Connect

    Tanaka, Koichi; Anders, André

    2015-11-15

    To study the temporal evolution of ion energy distribution functions, charge-state-resolved ion energy distribution functions of pulsed arc plasmas from Cr and Cr-Al cathodes were recorded with high time resolution by using direct data acquisition from a combined energy and mass analyzer. The authors find increases in intensities of singly charged ions, which is evidence that charge exchange reactions took place in both Cr and Cr-Al systems. In Cr-Al plasmas, the distributions of high-charge-state ions exhibit high energy tails 50 μs after discharge ignition, but no such tails were observed at 500 μs. The energy ratios of ions of different charge states at the beginning of the pulse, when less neutral atoms were in the space in front of the cathode, suggest that ions are accelerated by an electric field. The situation is not so clear after 50 μs due to particle collisions. The initial mean ion charge state of Cr was about the same in Cr and in Cr-Al plasmas, but it decreased more rapidly in Cr-Al plasmas compared to the decay in Cr plasma. The faster decay of the mean ion charge state and ion energy caused by the addition of Al into a pure Cr cathode suggests that the mean ion charge state is determined not only by ionization processes at the cathode spot but also by inelastic collision between different elements.

  15. Phase Separation kinetics in an Fe-Cr-Al alloy

    SciTech Connect

    Capdevila, C.; Miller, Michael K; Chao, J.

    2012-01-01

    The {alpha}-{alpha}{prime} phase separation kinetics in a commercial Fe-20 wt.% Cr-6 wt.% Al oxide dispersion-strengthened PM 2000{trademark} steel have been characterized with the complementary techniques atom probe tomography and thermoelectric power measurements during isothermal aging at 673, 708, and 748 K for times up to 3600 h. A progressive decrease in the Al content of the Cr-rich {alpha}{prime} phase was observed at 708 and 748 K with increasing time, but no partitioning was observed at 673 K. The variation in the volume fraction of the {alpha}{prime} phase well inside the coarsening regime, along with the Avrami exponent 1.2 and activation energy 264 kJ mol{sup -1}, obtained after fitting the experimental results to an Austin-Rickett type equation, indicates that phase separation in PM 2000{trademark} is a transient coarsening process with overlapping nucleation, growth, and coarsening stages.

  16. Magnetic, structural and optical properties of Mn-based and Cr-based diluted magnetic semiconductors and alloys

    NASA Astrophysics Data System (ADS)

    Alsaad, A.

    2009-03-01

    We have implemented supercell approach by using local spin density functional theory for Mn-doped GaN, Mn-doped ScN and the linear muffin-tin orbital method to predict the structural and magnetic properties of these novel diluted magnetic semiconductors and their GaxMn1-xN and ScxMn1-xN alloys. The global energy minimum of MnN is obtained for zinc-blende structure. If the compound is compressed by 6 % the energy minimum corresponds to the NaCl structure in disagreement with the experimentally observed a slightly tetragonally distorted rocksalt structure, known as ? phase. The rocksalt structure of CrN at about 8 % lattice expansion becomes stable in the ferromagnetic (FM) state and has a global minimum energy at a lattice constant of 3.9 å. We have observed an isostructural phase transition for ScxMn1-xN alloys from zince-blende phase to hexagonal phase that occurs at a hydrostatic pressure of 17.5 GPa. Moreover, the structural and optical properties of single crystal CrN/ScN superlattices and Cr1-xScxN alloys are studied in details. We report an isostructural phase transition from wurtzite (w-CrN) to hexagonal (h-ScN) at a hydrostatic pressure of 21 GPa. We have also used first-principles methods to study the electronic, optical and magnetic properties of MnN and MnAs compounds in the hypothetical cubic zinc-blende phase, a phase in which the two MnN and MnAs binaries have the same local environment as that they have in GaMnN and GaMnAs alloys. We show that MnN exhibits antiferromagnetic (AFM) ground state and MnAs adopts ferromagnetic (FM) ground state.

  17. Two-Phase (TiAl+TiCrAl) Coating Alloys for Titanium Aluminides

    NASA Technical Reports Server (NTRS)

    Brady, Michael P. (Inventor); Smialek, James L. (Inventor); Brindley, William J. (Inventor)

    1998-01-01

    A coating for protecting titanium aluminide alloys, including the TiAl gamma + Ti3Al (alpha(sub 2)) class, from oxidative attack and interstitial embrittlement at temperatures up to at least 1000 C. is disclosed. This protective coating consists essentially of titanium, aluminum. and chromium in the following approximate atomic ratio: Ti(41.5-34.5)Al(49-53)Cr(9.5-12.5)

  18. Structure and wear behavior of AlCrSiN-based coatings

    NASA Astrophysics Data System (ADS)

    Chen, Yun; Du, Hao; Chen, Ming; Yang, Jun; Xiong, Ji; Zhao, Haibo

    2016-05-01

    AlCrN, AlCrSiCN, AlCrSiN/MoN, and AlCrSiN/NbN coatings have been deposited on high-polished WC-Co cemented carbide substrate and tools by mid-frequency magnetron sputtering in Ar/N2 mixtures. Al0.6Cr0.4, Al0.6Cr0.3Si0.1, and C/Mo/Nb targets were used during the deposition. The microstructure and mechanical properties of as-deposited coatings were investigated. Investigations of the wear behaviors of coated tools were also performed. The results showed that cubic structure was formed in the coatings. Broader CrAlN (1 1 1) and (2 0 0) peaks without SiNx peak were formed in the AlCrSiN/MexN coatings, which showed a nanocomposited structure. Meanwhile, according to SEM micrographs, AlCrN exhibited a columnar structure, while, AlCrSiCN, AlCrSiN/MoN, and AlCrSiN/NbN coatings showed nanocrystalline morphology. The nano-multilayered coatings performed higher hardness, H/E, and H3/E2 ratios compared with AlCrN coating. Through the Rockwell adhesion test, all the coatings exhibited adhesion strength quality HF1. After turning Inconel 718 under dry condition, the nano-multilyered coatings showed better wear resistance than AlCrN coating. Due to the molybdenum and niobium in the coating, AlCrSiN/MoN and AlCrSiN/NbN coatings showed the best wear resistance.

  19. Comparison of AlCrN and AlCrTiSiN coatings deposited on the surface of plasma nitrocarburized high carbon steels

    NASA Astrophysics Data System (ADS)

    Chen, Wanglin; Zheng, Jie; Lin, Yue; Kwon, Sikchol; Zhang, Shihong

    2015-03-01

    The AlCrN and AlCrTiSiN coatings were produced on the surface of plasma nitrocarburized T10 steels by multi-arc ion plating. The comparison of the microstructures and mechanical properties of the duplex coatings were investigated by means of X-ray diffraction, optical microscope, scanning electron microscope and transmission electron microscope, in association with mechanical property measurement. The results show that the AlCrN coatings with columnar grown are mainly composed of nanocrytalline fcc-(Cr,Al)N phases with {111} preferred orientation, whereas the superlattice and nanocomposite AlCrTiSiN coatings with planar growth mainly consist of nanocrystalline fcc-(Cr,Al)N phases with {100} perfected orientation, hcp-AlN and Si3N4 amorphous phases. The AlCrTiSiN duplex coating with the compound layer reveals higher hardness, adhesion strength, load capacity and lower friction coefficient when compared with the other duplex coatings, which is due to its superlattice and nanocomposite structure. Additionally, these improved properties are related to the appearance of the γ‧-phase which plays the nucleation sites for the coating nitrides and provides a strong supporting effect for the AlCrN and AlCrTiSiN coatings. The main wear mechanism of the duplex coatings without compound layer is spalling and chipping wear as well as tribooxidation wear, whereas the main wear mechanism of the duplex coatings with compound layer is tribooxidation wear.

  20. Experimental evidence of Cr magnetic moments at low temperature in Cr2A(A=Al, Ge)C.

    PubMed

    Jaouen, M; Bugnet, M; Jaouen, N; Ohresser, P; Mauchamp, V; Cabioc'h, T; Rogalev, A

    2014-04-30

    From x-ray magnetic circular dichroism experiments performed at low temperature on Cr2AlC and Cr2GeC thin films, it is evidenced that Cr atoms carry a net magnetic moment in these ternary phases. It is shown that the Cr magnetization of the Al-based compound nearly vanished at 100 K in agreement with what has been recently observed on bulk. X-ray linear dichroism measurements performed at various angles of incidence and temperatures clearly demonstrate the existence of a charge ordering along the c axis of the structure of Cr2AlC. All these experimental observations support, in part, theoretical calculations claiming that Cr dd correlations have to be considered to correctly describe the structure and properties of these Cr-based ternary phases. PMID:24721758

  1. Al/sub 2/O/sub 3/ adherence on CoCrAl alloys

    SciTech Connect

    Kingsley, L.M.

    1980-04-01

    Adherence of protective oxides on NiCrAl and CoCrAl superalloys has been promoted by a dispersion of a highly oxygen reactive element or its oxide being produced within the protection system. Two aspects of this subject are investigated here: the use of Al/sub 2/O/sub 3/ as both the dispersion and protective oxide; and the production of an HfO/sub 2/ dispersion while simultaneously aluminizing the alloy. It was found that an Al/sub 2/O/sub 3/ dispersion will act to promote the adherence of an external scale of Al/sub 2/O/sub 3/ to a degree comparable to previously tested dispersions and an HfO/sub 2/ dispersion comparable to that produced by a Rhines pack treatment is produced during aluminization.

  2. Mechanical Properties and Microstructure of the CoCrFeMnNi High Entropy Alloy Under High Strain Rate Compression

    NASA Astrophysics Data System (ADS)

    Wang, Bingfeng; Fu, Ao; Huang, Xiaoxia; Liu, Bin; Liu, Yong; Li, Zezhou; Zan, Xiang

    2016-07-01

    The equiatomic CoCrFeMnNi high entropy alloy, which crystallizes in the face-centered cubic (FCC) crystal structure, was prepared by the spark plasma sintering technique. Dynamic compressive tests of the CoCrFeMnNi high entropy alloy were deformed at varying strain rates ranging from 1 × 103 to 3 × 103 s-1 using a split-Hopkinson pressure bar (SHPB) system. The dynamic yield strength of the CoCrFeMnNi high entropy alloy increases with increasing strain rate. The Zerilli-Armstrong (Z-A) plastic model was applied to model the dynamic flow behavior of the CoCrFeMnNi high entropy alloy, and the constitutive relationship was obtained. Serration behavior during plastic deformation was observed in the stress-strain curves. The mechanism for serration behavior of the alloy deformed at high strain rate is proposed.

  3. Mechanical Properties and Microstructure of the CoCrFeMnNi High Entropy Alloy Under High Strain Rate Compression

    NASA Astrophysics Data System (ADS)

    Wang, Bingfeng; Fu, Ao; Huang, Xiaoxia; Liu, Bin; Liu, Yong; Li, Zezhou; Zan, Xiang

    2016-05-01

    The equiatomic CoCrFeMnNi high entropy alloy, which crystallizes in the face-centered cubic (FCC) crystal structure, was prepared by the spark plasma sintering technique. Dynamic compressive tests of the CoCrFeMnNi high entropy alloy were deformed at varying strain rates ranging from 1 × 103 to 3 × 103 s-1 using a split-Hopkinson pressure bar (SHPB) system. The dynamic yield strength of the CoCrFeMnNi high entropy alloy increases with increasing strain rate. The Zerilli-Armstrong (Z-A) plastic model was applied to model the dynamic flow behavior of the CoCrFeMnNi high entropy alloy, and the constitutive relationship was obtained. Serration behavior during plastic deformation was observed in the stress-strain curves. The mechanism for serration behavior of the alloy deformed at high strain rate is proposed.

  4. Effect of Mn on the Formation of Oxide Buildups Upon HVOF-Sprayed MCrAlY-Ceramic-Type Cermet Coatings

    NASA Astrophysics Data System (ADS)

    Huang, Tsai-Shang

    2011-03-01

    Thermal spray coatings have been widely used on hearth rolls in a continuous annealing line to improve steel sheet quality and to prolong the roll service life. One of the common defects formed on a working hearth roll is the oxide buildup. HVOF-sprayed CoCrAlY-CrB2-Y2O3 coating was used in this study to duplicate buildups by reacting with Fe and Mn oxides. The reaction was performed in a furnace at 900 °C with inert gases flowing through. After reacting for 8 days, large Mn-rich buildups were formed on the coating while the buildups without Mn were very small. Mn was shown to enhance the formation of buildups. Buildups from a hearth roll were also examined and compared with the laboratory ones.

  5. Importance of doping and frustration in itinerant Fe-doped Cr2Al

    DOE PAGESBeta

    Susner, M. A.; Parker, D. S.; Sefat, A. S.

    2015-05-12

    We performed an experimental and theoretical study comparing the effects of Fe-doping of Cr2Al, an antiferromagnet with a N el temperature of 670 K, with known results on Fe-doping of antiferromagnetic bcc Cr. (Cr1-xFex)2Al materials are found to exhibit a rapid suppression of antiferromagnetic order with the presence of Fe, decreasing TN to 170 K for x=0.10. Antiferromagnetic behavior disappears entirely at x≈0.125 after which point increasing paramagnetic behavior is exhibited. Moreover, this is unlike the effects of Fe doping of bcc antiferromagnetic Cr, in which TN gradually decreases followed by the appearance of a ferromagnetic state. Theoretical calculations explainmore » that the Cr2Al-Fe suppression of magnetic order originates from two effects: the first is band narrowing caused by doping of additional electrons from Fe substitution that weakens itinerant magnetism; the second is magnetic frustration of the Cr itinerant moments in Fe-substituted Cr2Al. In pure-phase Cr2Al, the Cr moments have an antiparallel alignment; however, these are destroyed through Fe substitution and the preference of Fe for parallel alignment with Cr. This is unlike bulk Fe-doped Cr alloys in which the Fe anti-aligns with the Cr atoms, and speaks to the importance of the Al atoms in the magnetic structure of Cr2Al and Fe-doped Cr2Al.« less

  6. Interstitial precipitation in Fe-Cr-Al alloys

    NASA Astrophysics Data System (ADS)

    Spear, W. S.; Polonis, D. H.

    1994-06-01

    Two separate stages of precipitation have been identified during the aging of ternary Fel8Cr3Al and Fel8Cr5Al alloys at temperatures in the vicinity of 475 °C. The first stage involves the formation of interstitial precipitates resulting from C and N impurities; the second and slower stage is the formation of the Cr-rich α' phase. Transmission electron microscopy (TEM) results show that carbonitride precipitation occurs preferentially at dislocations, stacking faults, and grain boundaries, and also uniformly through the matrix. Aging for times in excess of 400 hours at 475 °C promotes coarsening of the heterogeneous precipitates and dissolution of the uniformly distributed matrix particles. A resistometric analysis shows that the kinetics of the initial stages of precipitation can be described by a (time)2/3 relation. This kinetic behavior is explained in terms of stress-assisted diffusion in the highly stressed matrix resulting from coherency strains accompanying carbonitride precipitation. Experimental values of the activation energy for the first stage reaction correlate closely with those reported for the interstitial diffusion of C and N in alpha iron.

  7. Normal and excess nitrogen uptake by iron-based Fe-Cr-Al alloys: the role of the Cr/Al atomic ratio

    NASA Astrophysics Data System (ADS)

    Jung, K. S.; Schacherl, R. E.; Bischoff, E.; Mittemeijer, E. J.

    2011-06-01

    Upon nitriding ferritic iron-based Fe-Cr-Al alloys, containing a total of 1.50 at. % (Cr + Al) alloying elements with varying Cr/Al atomic ratio (0.21-2.00), excess nitrogen uptake occurred, i.e. more nitrogen was incorporated in the specimens than compatible with only inner nitride formation and equilibrium nitrogen solubility of the unstrained ferrite matrix. The amount of excess nitrogen increased with decreasing Cr/Al atomic ratio. The microstructure of the nitrided zone was investigated by X-ray diffraction, electron probe microanalysis, transmission electron microscopy and electron energy loss spectroscopy. Metastable, fine platelet-type, mixed Cr1- x Al x N nitride precipitates developed in the nitrided zone for all of the investigated specimens. The degree of coherency of the nitride precipitates with the surrounding ferrite matrix is discussed in view of the anisotropy of the misfit. Analysis of nitrogen-absorption isotherms, recorded after subsequent pre- and de-nitriding treatments, allowed quantitative differentiation of different types of nitrogen taken up. The amounts of the different types of excess nitrogen as function of the Cr/Al atomic ratio are discussed in terms of the nitride/matrix misfit and the different chemical affinities of Cr and Al for N. The strikingly different nitriding behaviors of Fe-Cr-Al and Fe-Cr-Ti alloys could be explained on this basis.

  8. Carbon Nanostructures Grown on Fe-Cr-Al Alloy

    NASA Astrophysics Data System (ADS)

    Čaplovičová, Mária; Čaplovič, Ľubomír; Búc, Dalibor; Vinduška, Peter; Janík, Ján

    2010-11-01

    The morphology and nanostructure of carbon nanotubes (CNTs), synthesized directly on Fe-Cr-Al-based alloy substrate using an alcohol catalytic chemical vapour deposition method (ACCVD), were examined by transmission electron microscopy (TEM). The grown CNTs were entangled with chain-like, bamboo-like, and necklace-like morphologies. The CNT morphology was affected by the elemental composition of catalysts and local instability of deposition process. Straight and bended CNTs with bamboo-like nanostructure grew mainly on γ-Fe and Fe3C particles. The synthesis of necklace-like nanostructures was influenced by silicon oxide, and growth of chain-like nanostructures was supported by a catalysts consisting of Fe, Si, oxygen and trace of Cr. Most of nanotubes grew according to base growth mechanism.

  9. Synthesis, characterization and electrochemical performance of Al-substituted Li₂MnO₃

    SciTech Connect

    Dhital, Chetan; Huq, Ashfia; Paranthaman, Mariappan Parans; Manivannan, Ayyakkannu; Torres-Castro, Loraine; Shojan, Jifi; Julien, Christian M.; Katiyar, Ram S.

    2015-08-08

    Li2MnO3 is known to be electrochemically inactive due to Mn in tetravalent oxidation state. Several compositions such as Li2MnO3 , Li1.5Al0.17MnO3, Li1.0Al0.33MnO3 and Li0.5Al0.5MnO3 were synthesized by a sol–gel Pechini method. All the samples were characterized with x-ray diffraction, Raman, x-ray photoelectron spectroscopy, scanning electron microscopy, Tap density and BET analyzer. X-ray diffraction patterns indicated the presence of monoclinic phase for pristine Li2MnO3and mixed monoclinic/spinel phases (Li2 - xMn1 - yAlx + yO3 + z) for Al-substituted Li2MnO3compounds. The Al substitution seems to occur both at Li and Mn sites, which could explain the presence of spinel phase. X-ray photoelectron spectroscopy for Mn 2p orbital reveals a significant decrease in binding energy for Li1.0Al0.33MnO3 and Li0.5Al0.5MnO3 compounds. Cyclic voltammetry, charge/discharge cycles and electrochemical impedance spectroscopy were also performed. A discharge capacity of 24 mAh g-1 for Li2MnO3, 68 mAh g-1 for Li1.5Al0.17MnO3, 58 mAh g-1 for Li1.0Al0.33MnO3 and 74 mAh g-1 for Li0.5Al0.5MnO3 were obtained. As a result, aluminum substitutions increased the formation of spinel phase which is responsible for cycling.

  10. Removal of Cr(VI) from aqueous solutions by adsorption on MnO2.

    PubMed

    Gheju, Marius; Balcu, Ionel; Mosoarca, Giannin

    2016-06-01

    Adsorption of Cr(VI) on MnO2 was investigated with respect to effect of pH, temperature, ionic strength, initial Cr(VI) concentration, co-presence of different anions (HCO3(-), SO4(2-), H2PO4(-), NO3(-) and Cl(-)) and of low molecular weight natural organic materials (LMWNOM) (acetate, oxalate and citrate). The process was rapid during the first 3-5min, reaching equilibrium after one hour. Adsorption decreased with increasing pH, temperature and Cr(VI) initial concentration, and increased with increasing ionic strength. Co-presence of phosphate, sulfate, bicarbonate, citrate and oxalate hindered Cr(VI) adsorption, whereas nitrate, chloride and acetate did not exert any notable influence. The overall order of Cr(VI) adsorption suppression due to co-presence of anions and LMWNOM was H2PO4(-)>HCO3(-)>SO4(2-), and oxalate>citrate, respectively. Highest experimental equilibrium sorption capacity (0.83mgg(-1)) was obtained at 20°C and pH 5.9, while lowest (0.18mgg(-1)) was noticed in the co-presence of H2PO4(-), at 20°C and pH 6.9. Adsorption kinetics was successfully fitted by pseudo-second-order model. Mechanisms for both specific and non-specific adsorption are likely to be involved, while rate-controlling step involved both intra-particle and film diffusion processes. Cr(VI) was strongly bound to MnO2, which makes risks of its subsequent liberation into the environment to be low. PMID:26947189

  11. One-pot synthesis of Mn-doped TiO2 grown on graphene and the mechanism for removal of Cr(VI) and Cr(III).

    PubMed

    Chen, Zengping; Li, Yaru; Guo, Meng; Xu, Fengyun; Wang, Peng; Du, Yu; Na, Ping

    2016-06-01

    Mn-doped TiO2 grown on reduced graphene oxide(rGO) was synthesized by one-pot hydrothermal method and the photocatalytic removal of Cr by the material was investigated under sunlight. The materials were characterized by a combination of scanning electron microscopy, transmission electron microscopy, X-ray diffraction, thermogravimetric analysis, Brunauer-Emmett-Teller method, UV-vis diffuse reflectance spectra, photoluminescence spectra, electrochemical impedance spectroscopy and X-ray photoelectron spectroscopy. Cr(total) removal efficiency of the material is 97.32% in 30min and 99.02% in 60min under sunlight irradiation, as the initial concentration of Cr(VI) is 20mg/L. The high photocatalytic activity under visible light is considered mainly due to the Mn-doping, and rGO plays an important role in the synergetic effect of adsorption and photocatalysis to sustain the high efficient removal of Cr(VI) and Cr(III). Cr(VI) adsorbed on the surface of rGO is reduced to Cr(III) by photo electrons which are transported through rGO, and the reaction product Cr(III) continues to be adsorbed. The process contributes to the release of abundant photocatalytic sites of Mn-TiO2 and improves photocatalytic efficiency. The excellent adsorption and photocatalytic effect with the explanation of the synergetic mechanism are very useful not only for fundamental research but also for the potential practical applications. PMID:26921512

  12. Zener Relaxation Peak in an Fe-Cr-Al Alloy

    NASA Astrophysics Data System (ADS)

    Zhou, Zheng-Cun; Cheng, He-Fa; Gong, Chen-Li; Wei, Jian-Ning; Han, Fu-Sheng

    2002-11-01

    We have studied the temperature spectra of internal friction and relative dynamic modulus of the Fe-(25 wt%)Cr-(5 wt%)Al alloy with different grain sizes. It is found that a peak appears in the internal friction versus temperature plot at about 550°C. The peak is of a stable relaxation and is reversible, which occurs not only during heating but also during cooling. Its activation energy is 2.5 (+/- 0.15) eV in terms of the Arrhenius relation. In addition, the peak is not obvious in specimens with a smaller grain size. It is suggested that the peak originates from Zener relaxation.

  13. Growth and characterization of TiAlN/CrAlN superlattices prepared by reactive direct current magnetron sputtering

    SciTech Connect

    Barshilia, Harish C.; Deepthi, B.; Rajam, K. S.; Bhatti, Kanwal Preet; Chaudhary, Sujeet

    2009-01-15

    TiAlN and CrAlN coatings were prepared using a reactive direct current magnetron sputtering system from TiAl and CrAl targets. Structural characterization of the coatings using x-ray diffraction (XRD) revealed the B1 NaCl structure of TiAlN and CrAlN coatings with a prominent reflection along the (111) plane. The XPS data confirmed the bonding structures of TiAlN and CrAlN single layer coatings. Subsequently, nanolayered multilayer coatings of TiAlN/CrAlN were deposited on silicon and mild steel (MS) substrates at different modulation wavelengths ({lambda}) with a total thickness of approximately 1.0 {mu}m. The modulation wavelengths were calculated from the x-ray reflectivity data using modified Bragg's law. TiAlN/CrAlN multilayer coatings were textured along (111) for {lambda}<200 A and the XRD patterns showed the formation of superlattice structure for coatings deposited at {lambda}=102 A. The x-ray reflectivity data showed reflections of fifth and seventh orders for multilayer coatings deposited at {lambda}=102 and 138 A, respectively, indicating the formation of sharp interfaces between TiAlN and CrAlN layers. The cross-sectional scanning electron microscopy image of TiAlN/CrAlN multilayer coatings indicated a noncolumnar and dense microstructure. A maximum hardness of 39 GPa was observed for TiAlN/CrAlN multilayer coatings deposited at {lambda}=93 A, which was higher than the rule-of-mixture value (30 GPa) for TiAlN and CrAlN. Study of thermal stability of the coatings in air using micro-Raman spectroscopy indicated that the TiAlN/CrAlN multilayer coatings were stable up to 900 deg. C in air. TiAlN/CrAlN multilayer coatings also exhibited improved corrosion resistance when compared to the MS substrate.

  14. Development and High Temperature Property Evaluation of Ni-Co-Cr-Al Composite Electroforms

    NASA Astrophysics Data System (ADS)

    Srivastava, Meenu; Siju; Balaraju, J. N.; Ravisankar, B.

    2015-05-01

    Ni-Co-Cr-Al composite electroforms were developed with cobalt content of 10 and 40 wt.%. Cr and Al nano-particles were suspended in sulphamate electrolyte and co-deposited in the Ni-Co matrices. The surface morphology was investigated using field emission scanning electron microscope and the composition analyzed by energy-dispersive x-ray analysis. The oxidation resistance of the electroforms was studied from 600 to 1000 °C. The weight gain of Ni-10 wt.%Co-Cr-Al was less (better oxidation resistance) compared to Ni-Cr-Al and Ni-40 wt.%Co-Cr-Al. The x-ray diffraction studies revealed that the oxidation product formed on the surface of Ni-Cr-Al and Ni-10 wt.%Co-Cr-Al consisted of NiO and Al2O3, while Ni-40 wt.%Co-Cr-Al comprised oxides such as NiCo2O4, CrO3, CoO, NiO, and Al2O3. The hot corrosion behavior was investigated in 75%Na2SO4 + 25%NaCl environment at 800 °C. It was found that the hot corrosion resistance of the composite coating improved with increase in cobalt content. The probable composition suitable for high-temperature applications was found to be Ni-10 wt.%Co-Cr-Al.

  15. Thermoelectric Properties of Mn-Doped Ca5Al2Sb6

    NASA Astrophysics Data System (ADS)

    Zevalkink, Alex; Swallow, Jessica; Snyder, G. Jeffrey

    2012-05-01

    Ca5Al2Sb6 is a relatively inexpensive Zintl compound exhibiting promising thermoelectric efficiency at temperatures suitable for waste heat recovery. Motivated by our previous studies of Ca5Al2Sb6 doped with Na and Zn, this study focuses on doping with Mn2+ at the Al3+ site. While Mn is a successful p-type dopant in Ca5Al2Sb6, we find that incomplete dopant activation yields lower hole concentrations than obtained with either previously investigated dopant. High-temperature Hall effect and Seebeck coefficient measurements show a transition from nondegenerate to degenerate semiconducting behavior in Ca5Al2- x Mn x Sb6 samples ( x = 0.05, 0.1, 0.2, 0.3, 0.4) with increasing Mn content. Ultimately, no improvement in zT is achieved via Mn doping, due in part to the limited carrier concentration range achieved.

  16. Elastocaloric effect in CuAlZn and CuAlMn shape memory alloys under compression.

    PubMed

    Qian, Suxin; Geng, Yunlong; Wang, Yi; Pillsbury, Thomas E; Hada, Yoshiharu; Yamaguchi, Yuki; Fujimoto, Kenjiro; Hwang, Yunho; Radermacher, Reinhard; Cui, Jun; Yuki, Yoji; Toyotake, Koutaro; Takeuchi, Ichiro

    2016-08-13

    This paper reports the elastocaloric effect of two Cu-based shape memory alloys: Cu68Al16Zn16 (CuAlZn) and Cu73Al15Mn12 (CuAlMn), under compression at ambient temperature. The compression tests were conducted at two different rates to approach isothermal and adiabatic conditions. Upon unloading at a strain rate of 0.1 s(-1) (adiabatic condition) from 4% strain, the highest adiabatic temperature changes (ΔTad) of 4.0 K for CuAlZn and 3.9 K for CuAlMn were obtained. The maximum stress and hysteresis at each strain were compared. The stress at the maximum recoverable strain of 4.0% for CuAlMn was 120 MPa, which is 70% smaller than that of CuAlZn. A smaller hysteresis for the CuAlMn alloy was also obtained, about 70% less compared with the CuAlZn alloy. The latent heat, determined by differential scanning calorimetry, was 4.3 J g(-1) for the CuAlZn alloy and 5.0 J g(-1) for the CuAlMn alloy. Potential coefficients of performance (COPmat) for these two alloys were calculated based on their physical properties of measured latent heat and hysteresis, and a COPmat of approximately 13.3 for CuAlMn was obtained.This article is part of the themed issue 'Taking the temperature of phase transitions in cool materials'. PMID:27402936

  17. Stochastic jumps of magnetization in [Mn{(R/S)-pn}]2[Mn{(R/S)-pn}2(H2O)][Cr(CN)6]2 molecular magnet

    NASA Astrophysics Data System (ADS)

    Kirman, M. V.; Talantsev, A. D.; Koplak, O. V.; Morgunov, R. B.

    2015-03-01

    Series of stochastic jumps of the magnetic moment (up to five individual jumps) have been observed at the demagnetization of single crystals of [Mn{(R/S)-pn}]2[Mn{(R/S)-pn}2(H2O)][Cr(CN)6]2 molecular magnet in a narrow range of magnetic fields near the coercive force ( H c = 7.5 Oe). The magnetic field at which jumps of the magnetization arise decreases with an increase in the temperature.

  18. Effect of slag composition on the cleanliness of 28MnCr5 gear steel in the refining processes

    NASA Astrophysics Data System (ADS)

    Dong, Wen-liang; Ni, Hong-wei; Zhang, Hua; Lü, Ze-an

    2016-03-01

    The equilibrium reaction between CaO—Al2O3—SiO2—MgO slag and 28MnCr5 molten steel was calculated to obtain the suitable slag composition which is effective for decreasing the oxygen content in molten steel. The dissolved oxygen content [O] in molten steel under different top slag conditions was calculated using a thermodynamic model and was measured using an electromotive force method in slag-steel equilibrium experiments at 1873 K. The relations among [O], the total oxygen content (T.O), and the composition of the slag were investigated. The experimental results show that both [O] and T.O decrease with decreasing SiO2 content of the slag and exhibit different trends with the changes in the CaO/Al2O3 mass ratio of the slag. Increasing the CaO/Al2O3 mass ratio results in a decrease in [O] and an increase in T.O. To ensure that T.O ≤ 20 ppm and [O] ≤ 10 ppm, the SiO2 content should be controlled to <5wt%, and the CaO/Al2O3 mass ratio should be in the range from 1.2 to 1.6.

  19. Searching for 0+ states in 50Cr: Implications for the superallowed β decay of 50Mn

    NASA Astrophysics Data System (ADS)

    Leach, K. G.; Garrett, P. E.; Ball, G. C.; Bender, P. C.; Bildstein, V.; Brown, B. A.; Burbadge, C.; Faestermann, T.; Hadinia, B.; Holt, J. D.; Laffoley, A. T.; Jamieson, D. S.; Jigmeddorj, B.; Radich, A. J.; Rand, E. T.; Stroberg, S. R.; Svensson, C. E.; Towner, I. S.; Wirth, H.-F.

    2016-07-01

    A 52Cr(p ,t )50Cr two-neutron pickup reaction was performed using the Q3D magnetic spectrograph at the Maier-Leibnitz-Laboratorium in Garching, Germany. Excited states in 50Cr were observed up to an excitation energy of 5.3 MeV. Despite significantly increased sensitivity and resolution over previous work, no evidence of the previously assigned first excited 0+ state was found. As a result, the 02+ state is reassigned at an excitation energy of Ex=3895.0 (5 ) keV in 50Cr. This reassignment directly impacts direct searches for a nonanalog Fermi β+ decay branch in 50Mn. These results also show better systematic agreement with the theoretical predictions for the 0+ state spectrum in 50Cr using the same formalism as the isospin-symmetry-breaking correction calculations for superallowed nuclei. The experimental data are also compared to ab-initio shell-model predictions using the IM-SRG formalism based on N N and 3 N forces from chiral-EFT in the p f -shell for the first time.

  20. Magnetism of ordered and disordered Ni2MnAl full Heusler compounds

    NASA Astrophysics Data System (ADS)

    Simon, E.; Vida, J. Gy.; Khmelevskyi, S.; Szunyogh, L.

    2015-08-01

    Based on ab initio calculations and Monte Carlo simulations, we present a systematic study of the magnetic ground state and finite temperature magnetism of ordered and disordered Ni2MnAl full Heusler compounds. By increasing the degree of the long-range chemical disorder between the Mn and Al sublattices, the magnetic order progressively changes from the ferromagnetic state in the ordered L 21 phase toward a fully compensated antiferromagnetic state in the disordered B 2 phase and we also conclude that the Ni atoms exhibit induced moments. We determine the Mn-Mn interactions by using the magnetic force theorem and find dominating, but rather weak ferromagnetic couplings in the ordered L 21 phase. We used a recently proposed renormalization technique to include the weak Ni moments into the spin model, which indeed remarkably increased the nearest-neighbor Mn-Mn interaction. In accordance with the total energy calculations, in the disordered compounds, strong antiferromagnetic site-antisite Mn-Mn interactions appear. Determining the spin-spin correlation functions from Monte Carlo simulations, we conclude that above the transition temperature, short-range antiferromagnetic correlations prevail between the Mn atoms. In view of the potential application of disordered Ni2MnAl as a room temperature antiferromagnet, we calculate the magnetic anisotropy energies of tetragonally distorted samples in the B 2 phase and find that they are smaller by two orders in magnitude than in the frustrated antiferromagnet IrMn3.

  1. Host Atom Diffusion in Ternary Fe-Cr-Al Alloys

    NASA Astrophysics Data System (ADS)

    Rohrberg, Diana; Spitzer, Karl-Heinz; Dörrer, Lars; Kulińska, Anna J.; Borchardt, Günter; Fraczkiewicz, Anna; Markus, Torsten; Jacobs, Michael H. G.; Schmid-Fetzer, Rainer

    2014-01-01

    In the Fe-rich corner of the Fe-Cr-Al ternary phase diagram, both interdiffusion experiments [1048 K to 1573 K (775 °C to 1300 °C)] and 58Fe tracer diffusion experiments [873 K to 1123 K (600 °C to 850 °C)] were performed along the Fe50Cr50-Fe50Al50 section. For the evaluation of the interdiffusion data, a theoretical model was used which directly yields the individual self-diffusion coefficients of the three constituents and the shift of the original interface of the diffusion couple through inverse modeling. The driving chemical potential gradients were derived using a phenomenological Gibbs energy function which was based on thoroughly assessed thermodynamic data. From the comparison of the individual self-diffusivities of Fe as obtained from interdiffusion profiles and independent 58Fe tracer diffusivities, the influence of the B2-A2 order-disorder transition becomes obvious, resulting in a slightly higher activation enthalpy for the bcc-B2 phase and a significantly lower activation entropy for this phase.

  2. Luminescence Dynamics of Cr2+ in CdTe and Cd0.55Mn0.45Te

    NASA Astrophysics Data System (ADS)

    Bluiett, A.; Hommerich, U.; Seo, J. T.; Shah, R.; Trivedi, S. B.; Kutcher, S. W.; Chen, R. J.; Wang, C. C.; Zong, H.

    2001-04-01

    Cr^2+ in tetrahedrally coordinated CdTe and Cd_0.55Mn_0.45Te crystals are under investigation as potential host materials for tunable, mid-infrared (MIR) lasers. The small crystal field splitting of the free ion energy levels of Cr^2+ induces absorption (1900nm) and stokes shifted emission (2000nm-3000nm) bands in the MIR. Also, the relatively large ionic mass and tetrahedral environment of Cr^2+ in CdTe and Cd_0.55Mn_0.45Te have shown that the luminescence efficiency at room temperature is approximately 72100luminescence lifetime decreases rapidly, which suggest that the effects of nonradiative decay increases. The decay dynamics of Cr^2+ in CdTe and Cd_0.55Mn_0.45Te will be described with the model of Struck and Fonger for the non-radiative decay rate.

  3. CaMn2Al10: Itinerant Mn magnetism on the verge of magnetic order

    SciTech Connect

    Steinke, L.; Simonson, J. W.; Yin, W. -G.; Smith, G. J.; Kistner-Morris, J. J.; Zellman, S.; Puri, A.; Aronson, M. C.

    2015-07-24

    We report the discovery of CaMn2Al10, a metal with strong magnetic anisotropy and moderate electronic correlations. Magnetization measurements find a Curie-Weiss moment of 0.83μB/Mn, significantly reduced from the Hund's rule value, and the magnetic entropy obtained from specific heat measurements is correspondingly small, only ≈ 9% of Rln2. These results imply that the Mn magnetism is highly itinerant, a conclusion supported by density functional theory calculations that find strong Mn-Al hybridization. Consistent with the layered nature of the crystal structure, the magnetic susceptibility χ is anisotropic below 20 K, with a maximum ratio of χ[010][001] ≈ 3.5. A strong power-law divergence χ(T) ~ T–1.2 below 20 K implies incipient ferromagnetic order, an Arrott plot analysis of the magnetization suggests a vanishing low Curie temperature TC ~ 0. Our experiments indicate that CaMn2Al10 is a rare example of a system where the weak and itinerant Mn-based magnetism is poised on the verge of order.

  4. Hot corrosion of Co-Cr, Co-Cr-Al, and Ni-Cr alloys in the temperature range of 700-750 deg C

    NASA Technical Reports Server (NTRS)

    Chiang, K. T.; Meier, G. H.

    1980-01-01

    The effect of SO3 pressure in the gas phase on the Na2SO4 induced hot corrosion of Co-Cr, Ni-Cr, and Co-Cr-Al alloys was studied in the temperature range 700 to 750 C. The degradation of the Co-Cr and Ni-Cr alloys was found to be associated with the formation of liquid mixed sulfates (CoSO4-Na2SO4 or NiSO4-Na2SO4) which provided a selective dissolution of the Co or Ni and a subsequent sulfidation oxidation mode of attack which prevented the maintenance of a protective Cr2O3 film. A clear mechanism was not developed for the degradation of Co-Cr-Al alloys. A pitting corrosion morphology was induced by a number of different mechanisms.

  5. Alloying effects on the microstructure and phase stability of Fe-Cr-Mn steels

    SciTech Connect

    Rawers, J.C.

    2008-05-01

    Austenitic Fe–Cr–Mn stainless steels interstitially alloyed with nitrogen have received considerable interest lately, due to their many property improvements over conventional Fe–Cr–Ni alloys. The addition of nitrogen to Fe–Cr–Mn stabilizes the fcc structure and increases the carbon solubility. The benefits of increased interstitial nitrogen and carbon content include: enhanced strength, hardness, and wear resistance. This study examines the effect of carbon, silicon, molybdenum, and nickel additions on the phase stability and tensile behavior of nitrogen-containing Fe–Cr–Mn alloys. Nitrogen and carbon concentrations exceeding 2.0 wt.% were added to the base Fe–18Cr–18Mn composition without the formation of nitride or carbide precipitates. Minor additions of molybdenum, silicon, and nickel did not affect nitrogen interstitial solubility, but did reduce carbon solubility resulting in the formation of M23C6 (M=Cr, Fe, Mo) carbides. Increasing the interstitial content increases the lattice distortion strain, which is directly correlated with an increase in yield stress.

  6. Incorporation, valence state, and electronic structure of Mn and Cr in bulk single crystal β-Ga2O3

    NASA Astrophysics Data System (ADS)

    Lovejoy, T. C.; Chen, Renyu; Yitamben, E. N.; Shutthanadan, V.; Heald, S. M.; Villora, E. G.; Shimamura, K.; Zheng, S.; Dunham, S. T.; Ohuchi, F. S.; Olmstead, M. A.

    2012-06-01

    Single crystals of transition metal (TM) doped β-Ga2O3, a wide gap semiconductor system of interest for transparent conductive oxide and diluted magnetic semiconductor applications, have been studied in the dilute, non-interacting limit (≤0.06 cation %). Based on optical absorption, particle induced x-ray emission, and Rutherford backscattering measurements, Mn does not incorporate as well as Cr, and Mn degrades the crystal quality. Using superconducting quantum interference device (SQuID) magnetometry, a Brillouin type paramagnetic magnetization is observed for Mn or Cr doped crystals with an effective number of Bohr magnetons per TM ion of 5.88 ± 0.1 or 3.95 ± 0.1, respectively. A trace ferromagnetic signal is consistent with a very small concentration of secondary phases in the Mn-doped crystal. The position of the edge in x-ray absorption near edge structure (XANES) measurements suggests that the Cr takes the 3+ valence, while a mixture of Mn2+ and Mn3+ are present; based on the absence of a prominent pre-edge feature in the XANES, both TM predominantly occupy an octahedral site in β-Ga2O3. Density functional theory (DFT) results, optical absorption and SQuID data are consistent with this assignment. While the Cr-doped crystal is conductive, the Mn-doped crystal is insulating, which is consistent with the Mn2+/Mn3+ mixed valence, assuming the Fermi level is pinned mid-gap at the Mn 2+/3+ transition level, which is predicted by DFT to be 1.8 eV above the valence band maximum.

  7. Al-augite and Cr-diopside ultramafic xenoliths in basaltic rocks from western United States

    USGS Publications Warehouse

    Wilshire, H.G.; Shervais, J.W.

    1975-01-01

    Ultramafic xenoliths in basalts from the western United States are divided into Al-augite and Cr-diopside groups. The Al-augite group is characterized by Al, Ti-rich augites, comparatively Fe-rich olivine and orthopyroxene, and Al-rich spinel, the Cr-diopside group by Cr-rich clinopyroxene and spinel and by Mg-rich olivine and pyroxenes. Both groups have a wide range of subtypes, but the Al-augite group is dominated by augite-rich varieties, and the Cr-diopside group by olivine-rich lherzolites. ?? 1975.

  8. Process development for Ni-Cr-ThO2 and Ni-Cr-Al-ThO2 sheet

    NASA Technical Reports Server (NTRS)

    Cook, R. C.; Norris, L. F.

    1973-01-01

    A process was developed for the production of thin gauge Ni-Cr-ThO2 sheet. The process was based on the elevated temperature deposition of chromium onto a wrought Ni-2%ThO2 sheet and subsequent high temperature diffusion heat treatments to minimize chromium concentration gradients within the sheet. The mechanical properties of the alloy were found to be critically dependent on those of the Ni-2%ThO2 sheet. A similar process for the production of a Ni-Cr-Al-ThO2 alloy having improved oxidation resistance was investigated but the non-reproducible deposition of aluminum from duplex Cr/Al packs precluded successful scale-up. The mechanical properties of the Ni-Cr-Al-ThO2 alloys were generally equivalent to the best Ni-Cr-ThO2 alloy produced in the programme.

  9. Hot and cold rolling of high nitrogen Cr-Ni and Cr-Mn austenitic stainless steels

    SciTech Connect

    Iiola, R.; Hanninen, H.; Kauppi, T.

    1998-10-01

    Behavior of austenitic Cr-Ni-(0.14--0.50)N and Cr-Mn-(0.78--1.00)N steels in hot and cold rolling was investigated by rolling experiments and mechanical testing. Structure of the steels in the as-cast condition and fracture surfaces after the rolling experiments were investigated using optical and scanning electron microscopy (SEM). Resistance to deformation was calculated using rolling forces in hot rolling. Increase in strength in the rolling experiments was related to the nitrogen content of the steels. Resistance to deformation during hot rolling increased with decreasing rolling temperature and with increasing nitrogen content. In some steels, hot rolling led to edge cracking, which was more a function of impurity than nitrogen content. Microscopy revealed that the edge cracking occurred along grain boundaries and second phase particles. For the cold-rolled steels, the highest achievable reductions were limited due to a crocodiling phenomenon, that is, opening of the strip end. Fracture type at the opened strip end was a brittle-like fracture.

  10. A sulfur segregation study of PWA 1480, NiCrAl, and NiAl alloys

    NASA Technical Reports Server (NTRS)

    Jayne, D. T.; Smialek, J. L.

    1993-01-01

    Some nickel based superalloys show reduced oxidation resistance from the lack of an adherent oxide layer during high temperature cyclic oxidation. The segregation of sulfur to the oxide-metal interface is believed to effect oxide adhesion, since low sulfur alloys exhibit enhanced adhesion. X ray Photoelectron Spectroscopy (XPS) was combined with an in situ sample heater to measure sulfur segregation in NiCrAl, PWA 1480, and NiAl alloys. The polished samples with a 1.5 to 2.5 nm (native) oxide were heated from 650 to 1100 C with hold times up to 6 hr. The sulfur concentration was plotted as a function of temperature versus time at temperature. One NiCrAl sulfur study was performed on the same casting used by Browning to establish a base line between previous Auger Electron Spectroscopy (AES) results and the XPS results of this study. Sulfur surface segregation was similar for PWA 1480 and NiCrAl and reached a maximum of 30 at% at 800 to 850 C. Above 900 C the sulfur surface concentration decreased to about 3 at% at 1100 C. These results are contrasted to the minimal segregation observed for low sulfur hydrogen annealed materials which exhibit improved scale adhesion.

  11. Cr, Mn, and Ca distributions for olivine in angritic systems: Constraints on the origins of Cr-rich and Ca-poor core olivine in angrite LEW87051

    NASA Technical Reports Server (NTRS)

    Mikouchi, T.; Mckay, G.; Le, L.

    1994-01-01

    Angrite meteorites are a type of basaltic achondrites that are noted for their very old cyrstallization ages (4.55 b.y.) and unusual chemical and mineralogical properties. In spite of great interest, only four angrites have been found. LEW87051 is the smallest one which weighs 0.6 g. It is a porphyritic rock with coarse subhedral to euhedral olivines set in a fine-grained groundmass which clearly represents a crystallized melt. The largest uncertainty about the petrogenesis of LEW87051 is the relationship between the large olivine crystals and the groundmass. Prinz et al. suggests that olivines are xenocrysts, while McKay et al. proposed a fractional cyrstallization model based on experimental studies. However, the crystals have Cr-rich and Ca-poor cores which do not match experimental olivines. Although Jurewicz and McKay tried to explaine the zoning of the rim by diffusion, some features are not explained. There also exists a definite composition boundary of Fe(2+) and MnO between the core and the rim. To clarify the origin of these olivines, we have performed experiments using LEW87051 analogs to measure the effects of oxygen fugacity on distribution coefficients of various elements in an angritic system.

  12. Nanoscale Cellular Structures at Phase Boundaries of Ni-Cr-Al-Ti and Ni-Cr-Mo-Al-Ti Superalloys

    NASA Astrophysics Data System (ADS)

    Wang, Cong; Dunand, David C.

    2015-06-01

    The microstructural evolution of Ni-20 pct Cr wires was studied during pack cementation where Al and Ti, with and without prior cementation with Mo, are deposited to the surface of the Ni-Cr wires and subsequently homogenized in their volumes. Mo deposition promotes the formation of Kirkendall pores and subsequent co-deposition of Al and Ti creates a triple-layered diffusional coating on the wire surface. Subsequent homogenization drives the alloying element to distribute evenly in the wires which upon further heat treatment exhibit the γ + γ' superalloy structure. Unexpectedly, formation of cellular structures is observed at some of the boundaries between primary γ' grains and γ matrix grains. Based on additional features ( i.e., ordered but not perfectly periodic structure, confinement at γ + γ' phase boundaries as a cellular film with ~100 nm width, as well as lack of topologically close-packed phases), and considering that similar, but much larger, microstructures were reported in commercial superalloys, it is concluded that the present cellular structure solidified as a thin film, composed of eutectic γ + γ' and from which the γ' phase was subsequently etched, which was created by incipient melting of a region near the phase boundary with high solute segregation.

  13. Influence of Carbon on the Microstructure of a Fe-Mn-Si-Cr-Ni Alloy

    NASA Astrophysics Data System (ADS)

    Mostafa, Khaled M.; de Baerdemaeker, J.; van Caenegem, N.; Segers, D.; Houbaert, Y.

    2009-08-01

    The influence of the addition of C to the Fe-Mn-Si-Cr-Ni base material is investigated at room temperature. Steel samples were deformed during a tensile experiment up to a strain of 17%. Light optical microscopy (OM) and x-ray diffraction (XRD) gave information about the different micro-structural phases that exist in the deformed and the undeformed alloys. The evolution of the defect structure is followed by positron annihilation techniques such as Doppler broadening of annihilation radiation spectroscopy (DBAR) and the positron annihilation lifetime spectroscopy (PALS). During deformation a martensitic ɛ-phase is induced. The size of the martensite plates increases with increasing deformation.

  14. Letter Report Documenting Progress of Second Generation ATF FeCrAl Alloy Fabrication

    SciTech Connect

    Yamamoto, Y.; Yang, Y.; Field, K. G.; Terrani, K.; Pint, B. A.; Snead, L. L.

    2014-06-10

    Development of the 2nd generation ATF FeCrAl alloy has been initiated, and a candidate alloy was selected for trial tube fabrication through hot-extrusion and gun-drilling processes. Four alloys based on Fe-13Cr-4.5Al-0.15Y in weight percent were newly cast with minor alloying additions of Mo, Si, Nb, and C to promote solid-solution and second-phase precipitate strengthening. The alloy compositions were selected with guidance from computational thermodynamic tools. The lab-scale heats of ~ 600g were arc-melted and drop-cast, homogenized, hot-forged and -rolled, and then annealed producing plate shape samples. An alloy with Mo and Nb additions (C35MN) processed at 800°C exhibits very fine sub-grain structure with the sub-grain size of 1-3μm which exhibited more than 25% better yield and tensile strengths together with decent ductility compared to the other FeCrAl alloys at room temperature. It was found that the Nb addition was key to improving thermal stability of the fine sub-grain structure. Optimally, grains of less than 30 microns are desired, with grains up to and order of magnitude in desired produced through Nb addition. Scale-up effort of the C35MN alloy was made in collaboration with a commercial cast company who has a capability of vacuum induction melting. A 39lb columnar ingot with ~81mm diameter and ~305mm height (with hot-top) was commercially cast, homogenized, hot-extruded, and annealed providing 10mm-diameter bar-shape samples with the fine sub-grain structure. This commercial heat proved consistent with materials produced at ORNL at the lab-scale. Tubes and end caps were machined from the bar sample and provided to another work package for the ATF-1 irradiation campaign in the milestone M3FT-14OR0202251.

  15. NiAl(110)/Cr(110) interface: A density functional theory study

    NASA Astrophysics Data System (ADS)

    Liu, W.; Li, J. C.; Zheng, W. T.; Jiang, Q.

    2006-05-01

    The optimal geometries, thermodynamic properties, and electronic structures of NiAl(110)/Cr(110) interface are studied using a first-principle density functional plane-wave ultrasoft pseudopotential method. Surface energies of different NiAl surfaces are compared with those obtained based on the classical broken-bond rule. Simulation results indicate that the structure of Ni and Al placed in the hollow sites of Cr atoms at the interface is more thermodynamically stable, and the NiCr bonding is dominated by 3d electrons of Ni and Cr. It is found that NiAl(110)/Cr(110) alloying could lower brittleness of NiAl compounds. With simulated values of adhesion work and interface energy for NiAl(110)/Cr(110) system, its mechanical and thermodynamic properties are also discussed.

  16. Corrosion Behavior of Thermally Sprayed NiCrBSi Coating on 16MnR Low-Alloy Steel in KOH Solution

    NASA Astrophysics Data System (ADS)

    Zeng, Q.; Sun, J.; Emori, W.; Jiang, S. L.

    2016-05-01

    NiCrBSi coatings were selected as protective material and air plasma-sprayed on 16MnR low-alloy steel substrates. Corrosion behavior of 16MnR substrates and NiCrBSi coatings in KOH solution were evaluated by polarization resistance ( R p), potentiodynamic polarization curves, electrochemical impedance spectroscopy, and immersion corrosion tests. Electrolytes were solutions with different KOH concentrations. NiCrBSi coating showed superior corrosion resistance in KOH solution compared with the 16MnR. Corrosion current density of 16MnR substrate was 1.7-13.0 times that of NiCrBSi coating in the given concentration of KOH solution. By contrast, R p of NiCrBSi coating was 1.2-8.0 times that of the substrate, indicating that the corrosion rate of NiCrBSi coating was much lower than that of 16MnR substrate. Capacitance and total impedance value of NiCrBSi coating were much higher than those of 16MnR substrate in the same condition. This result indicates that corrosion resistance of NiCrBSi coating was better than that of 16MnR substrate, in accordance with polarization results. NiCrBSi coatings provided good protection for 16MnR substrate in KOH solution. Corrosion products were mainly Ni/Fe/Cr oxides.

  17. Gain measurements and average power capabilities of Cr(3+):LiSrAlF6

    NASA Astrophysics Data System (ADS)

    Hanson, F.; Bendall, C.; Poirier, P.

    1993-09-01

    Gain for flash-lamp-pumped Cr:LiSrAlF6 and Cr:Li(Sr(1-x),Ca(x))AlF6 from 790 to 1000 nm is reported. For Cr:LiSrAlF6 thermal fracture occurred at heat loadings of 4.5 W/cm and about 6 W/sq cm in the rod and slab geometry, respectively. Excited-state upconversion losses were evident in the slabs at high pump energy.

  18. Third element effect in the surface zone of Fe-Cr-Al alloys

    NASA Astrophysics Data System (ADS)

    Airiskallio, E.; Nurmi, E.; Heinonen, M. H.; Väyrynen, I. J.; Kokko, K.; Ropo, M.; Punkkinen, M. P. J.; Pitkänen, H.; Alatalo, M.; Kollár, J.; Johansson, B.; Vitos, L.

    2010-01-01

    The third element effect to improve the high temperature corrosion resistance of the low-Al Fe-Cr-Al alloys is suggested to involve a mechanism that boosts the recovering of the Al concentration to the required level in the Al-depleted zone beneath the oxide layer. We propose that the key factor in this mechanism is the coexistent Cr depletion that helps to maintain a sufficient Al content in the depleted zone. Several previous experiments related to our study support that conditions for such a mechanism to be functional prevail in real oxidation processes of Fe-Cr-Al alloys.

  19. The roles of Zr and Mn in processing and superplasticity of Al-Mg alloys

    NASA Technical Reports Server (NTRS)

    Mcnelley, Terry R.; Hales, S. J.

    1990-01-01

    Processing studies have been conducted on two alloys, of nominal compositions Al-10Mg-0.1Zr or Al-10Mg-0.5Mn, in order to clarify the role of the dispersoid forming Zr or Mn additions. Mechanical property data reveal that the Mn-containing alloy has a lower maximum elongation but exhibits superplastic response over a broader range of temperature. Microstructural investigations and texture analyses were utilized to assess the effect of the presence of Al8Mg5 precipitates in combination with either Al3Zr or Al6Mn dispersoid particles during isothermal rolling at 300 C and subsequent tensile deformation at temperatures from 200-425 C.

  20. Gd{sub 3+}-ESR and magnetic susceptibility of GdCu{sub 4}Al{sub 8} and GdMn{sub 4}Al{sub 8}

    SciTech Connect

    Coldea, R.; Coldea, M.; Pop, I.

    1994-03-01

    Gd ESR of GdCu{sub 4}Al{sub 8} and GdMn{sub 4}Al{sub 8} and magnetic susceptibility of GdCu{sub 4}Al{sub 8}, GdMn{sub 4}Al{sub 8}, and YMn{sub 4}Al{sub 8} were measured in the temperature range of 290K--460K and 90K--1050K, respectively. The occurrence of the Mn moment in YMn{sub 4}Al{sub 8} and GdMn{sub 4}Al{sub 8} is strongly correlated with the critical value of d{approx}2.6{angstrom} of the Mn-Mn distance below which the Mn moment is not stable. The experimental data for GdMn{sub 4}Al{sub 8}, compared with the data for the isostructural compounds GdCu{sub 4}Al{sub 8} and YMn{sub 4}Al{sub 8}, show that near the critical value of d, the existence of Mn moment depends not only on the value of d, but also on the local magnetic surroundings. It has been revealed that the magnetic character of Mn moment in YMn{sub 4}Al{sub 8} and GdMn{sub 4}Al{sub 8} changes from an itinerant electron type to a local-moment type with increasing temperature.

  1. Elimination of interface states of Co2MnSi/MgO/Co2MnSi magnetic tunneling junction by inserting an Al atomic layer

    NASA Astrophysics Data System (ADS)

    Yu, H. L.; Yang, G. W.

    2011-01-01

    Aiming at improvement performance of Co2MnSi/MgO/Co2MnSi magnetic tunneling junction (MTJ), we have studied interface behaviors of Co2MnSi/MgO by inserting an Al atomic layer between Heusler alloy and barrier, i.e., CoCo/Al/O, MnSi/Al/O, MnMn/Al/O and SiSi/Al/O four interfaces. It was found that CoCo/Al/O is stable and half-metallic, meaning interface states can be eliminated in this system. Hybridization and repulsion of transition-metal d and p states of sp atoms at interface and electrons transfer between interfacial atoms were suggested to be responsible for interface states elimination. These findings open a way to eliminate the interface states in MTJ.

  2. Rapid Solidification Behavior of Fe-Cr-Mn-Mo-Si-C Alloys

    NASA Astrophysics Data System (ADS)

    Ranganathan, Sathees; Makaya, Advenit; Fredriksson, Hasse; Savage, Steven

    2007-12-01

    The rapid solidification behavior of alloys in the Fe-Cr-Mn-Mo-Si-C system was investigated for different compositions and cooling rates. The C content was varied and alloying additions of Mo and B were studied with respect to their effect on the microstructure. The alloys were cast as either melt-spun ribbons or as 1-mm-thick plates after levitation or as rods 2 to 4 mm in diameter by injection into copper molds. A homogeneous single-phase structure was obtained for the alloy of composition 72.8Fe-8Cr-6Mn-5Si-5Mo-3.2C (wt pct), for a sample diameter of 2.85 mm, at a cooling rate of ≈1100 K/s. The single-phase structure was identified as a metastable solid solution, exhibiting the characteristics of the ɛ phase. Upon reheating, decomposition of the single-phase structure into fine bainite plates and secondary carbides was observed between 600 °C and 700 °C. The annealed structure obtained showed high hardness values (>850 HV).

  3. Synthesis, structures and magnetic properties of the dimorphic Mn2CrSbO6 oxide.

    PubMed

    Dos santos-García, Antonio J; Solana-Madruga, Elena; Ritter, Clemens; Ávila-Brande, David; Fabelo, Oscar; Sáez-Puche, Regino

    2015-06-21

    The perovskite polymorph of Mn(2)CrSbO(6) compound has been synthesized at 8 GPa and 1473 K. It crystallizes in the monoclinic P21/n space group with cell parameters a = 5.2180 (2) Å, b = 5.3710(2) Å, c = 7.5874(1) Å and β = 90.36(1)°. Magnetic susceptibility and magnetization measurements show the simultaneous antiferromagnetic ordering of Mn(2+) and Cr(3+) sublattices below TN = 55 K with a small canting. Low temperature powder neutron diffraction reveals a commensurate magnetic structure with spins confined to the ac-plane and a propagation vector κ = [1/2 0 1/2]. The thermal treatment of this compound induces an irreversible phase transition to the ilmenite polymorph, which has been isolated at 973 K and crystallizes in R3[combining macron] space group with cell parameters a = 5.2084 (4) Å and c = 14.4000 (11) Å. Magnetic susceptibility, magnetization and powder neutron diffraction data confirm the antiferromagnetic helical ordering of spins in an incommensurate magnetic structure with κ = [00 0.46] below 60 K, and the temperature dependence of the propagation vector up to κ = [00 0.54] at about 10 K. PMID:25623228

  4. Disorder, frustration and lattice volume effects in YMnIn, Th 0.8R 0.2MnAl (R=Sc, Lu and Y), ThMn 1.3Al 0.7 and ThMnAl 1- xIn x alloys

    NASA Astrophysics Data System (ADS)

    Dhar, S. K.; Manfrinetti, P.; Palenzona, A.

    2002-12-01

    The antiferromagnetic exchange interaction between the Mn ions in the cubic Laves-phase alloys Th 0.8R 0.2MnAl, ThMnAl 1- xIn x ( x≤0.2), ThMn 1.3Al 0.7 and the hexagonal Laves-phase YMnIn is inherently geometrically frustrated due to the tetrahedral co-ordination of the Mn ions. Together with disorder on the Mn-sublattice due to the partial replacement of Mn by Al and/or In, it leads to spin-glass-type freezing of the Mn magnetic moments in these alloys when the average Mn-Mn bond length is 2.850 Å or less. For alloys with greater bond lengths ( x>0.2), the data corroborate the suggestion made earlier [J. Magn. Magn. Mater. 231 (2000) 404] that the exchange becomes ferromagnetic.

  5. The Charpy impact behavior of Fe{sub 3}Al and Fe{sub 3}Al-20 at % Mn alloys

    SciTech Connect

    Liu, J.N.; Yan, W.; Ma, J.L.; Wu, K.H.

    1997-12-31

    A series of experiments were conducted to investigate the impact fracture behavior of Fe{sub 3}Al and Fe{sub 3}Al-20 Mn alloys. The results of this study indicated that: (i) The addition of Mn introduces an ordered L1{sub 2}-type phase in the Fe{sub 3}Al-based alloys. On the other hand, the addition of Mn decreases the order parameter of the DO{sub 3} {alpha} phase. (ii) The total-impact energy of an Fe{sub 3}Al alloy increases with the temperature at the low-temperature range (<600 C), then drops around 700 C, and finally increases again as the temperature further elevates. (iii) The trend of the variation of the impact energy of Fe{sub 3}Al-20 at % Mn alloy with temperature is the same as that of the Fe{sub 3}Al alloy. (iv) And the addition of Mn significantly improves the impact energy of the Fe{sub 3}Al-based alloy, and changes the variation of the crack-growth energy with the testing temperature when the temperature is above 700 C.

  6. Manganese valence and coordination structure in Mn,Mg-codoped {gamma}-AlON green phosphor

    SciTech Connect

    Takeda, Takashi; Xie, Rong-Jun; Hirosaki, Naoto; Matsushita, Yoshitaka; Honma, Tetuso

    2012-10-15

    The valence and coordination structure of manganese in a Mn,Mg-codoped {gamma}-AlON spinel-type oxynitride green phosphor were studied by synchrotron X-ray diffraction and absorption fine structure measurements. The absorption edge position of the XANES revealed the bivalency of Mn. Two cation sites are available in the spinel structure for cation doping: a tetrahedral site and an octahedral site. The pre-edge of the XANES and the distance to the nearest neighbor atoms obtained from the EXAFS measurement showed that Mn was situated at the tetrahedral site. Rietveld analysis showed that the vacancy occupied the octahedral site. The preferential occupation of the tetrahedral site by Mn and the roles of N and Mg are discussed in relation to the spinel crystal structure. - Graphical Abstract: Fourier transform of EXAFS of Mn K-edge for Mn,Mg-codoped green phosphor and Mn coordination structure. Highlights: Black-Right-Pointing-Pointer Mn, Mg-codoped {gamma}-AlON green phosphor for white LED. Black-Right-Pointing-Pointer The valence of Mn is divalent. Black-Right-Pointing-Pointer Mn occupies the tetrahedral site in the spinel structure.

  7. Optical properties of heusler alloys Co2FeSi, Co2FeAl, Co2CrAl, and Co2CrGa

    NASA Astrophysics Data System (ADS)

    Shreder, E. I.; Svyazhin, A. D.; Belozerova, K. A.

    2013-11-01

    The results of an investigation of optical properties and the calculations of the electronic structure of Co2FeSi, Co2FeAl, Co2CrAl, and Co2CrGa Heusler alloys are presented. The main focus of our attention is the study of the spectral dependence of the real part (ɛ1) and imaginary part (ɛ2) of the dielectric constant in the range of wavelengths λ = 0.3-13 μm using the ellipsometric method. An anomalous behavior of the optical conductivity σ(ω) has been found in the infrared range in the Co2CrAl and Co2CrGa alloys, which differs substantially from that in the Co2FeSi and Co2FeAl alloys. The results obtained are discussed based on the calculations of the electronic structure.

  8. Exploring the Cr2+ doping effect on structural, vibrational and dielectric properties of Mn-Zn ferrites

    NASA Astrophysics Data System (ADS)

    Choudhary, Pankaj; Tyagi, Tarun; Dar, M. A.; Varshney, Dinesh

    2016-05-01

    A series of Cr doped Mn-Zn ferrites with compositional formula Mn0.5Zn0.5-xCrxFe2O4 (x = 0, 0.3, 0.5) were prepared by solid-state reaction route. X-ray diffraction (XRD) analysis reveals that the samples prepared are polycrystalline cubic spinel in structure (Fd3m) with some secondary phase of α-Fe2O3. Slight variation in the lattice parameter of Cr doped Mn0.5Zn0.5Fe2O4 has been observed due to difference in ionic radii of cations. Small shift in Raman modes towards higher wave number has been observed. Further the line width decreases with the doping ions. A giant dielectric constant ~104 is observed for parent Mn0.5Zn0.5Fe2O4 which is found to decrease with increase in Cr2+ doping. Low dielectric loss is observed for Mn0.5Zn0.5Fe2O4 and improves with Cr2+ doping at Zn2+ site.

  9. Catalytic ozonation of petroleum refinery wastewater utilizing Mn-Fe-Cu/Al2O 3 catalyst.

    PubMed

    Chen, Chunmao; Yoza, Brandon A; Wang, Yandan; Wang, Ping; Li, Qing X; Guo, Shaohui; Yan, Guangxu

    2015-04-01

    There is of great interest to develop an economic and high-efficient catalytic ozonation system (COS) for the treatment of biologically refractory wastewaters. Applications of COS require options of commercially feasible catalysts. Experiments in the present study were designed to prepare and investigate a novel manganese-iron-copper oxide-supported alumina-assisted COS (Mn-Fe-Cu/Al2O3-COS) for the pretreatment of petroleum refinery wastewater. The highly dispersed composite metal oxides on the catalyst surface greatly promoted the performance of catalytic ozonation. Hydroxyl radical mediated oxidation is a dominant reaction in Mn-Fe-Cu/Al2O3-COS. Mn-Fe-Cu/Al2O3-COS enhanced COD removal by 32.7% compared with a single ozonation system and by 8-16% compared with Mn-Fe/Al2O3-COS, Mn-Cu/Al2O3-COS, and Fe-Cu/Al2O3-COS. The O/C and H/C ratios of oxygen-containing polar compounds significantly increased after catalytic ozonation, and the biodegradability of petroleum refinery wastewater was significantly improved. This study illustrates potential applications of Mn-Fe-Cu/Al2O3-COS for pretreatment of biologically refractory wastewaters. PMID:25649390

  10. Exchange bias effects in Heusler alloy Ni2MnAl/Fe bilayers

    NASA Astrophysics Data System (ADS)

    Tsuchiya, Tomoki; Kubota, Takahide; Sugiyama, Tomoko; Huminiuc, Teodor; Hirohata, Atsufumi; Takanashi, Koki

    2016-06-01

    Ni2MnAl Heusler alloy thin films were epitaxially grown on MgO(1 0 0) single crystal substrates by ultra-high-vacuum magnetron sputtering technique. X-ray diffraction and transmission electron microscopy observation revealed that the structures of all the Ni2MnAl thin films were B2-ordered regardless of the deposition temperature ranging from room temperature to 600 °C. The temperature dependence of electrical resistivity showed a kink about 280 K, which was consistent with a reported value of the Néel temperature for antiferromagnetic B2-Ni2MnAl. The magnetization curves of Ni2MnAl/Fe bilayer samples showed a shift caused by the interfacial exchange interaction at 10 K. The maximum value of the exchange bias field H ex was 55 Oe corresponding to the exchange coupling energy J k of 0.03 erg cm‑2.

  11. Microstructural stability of Fe-Cr-Al alloys at 450-550 °C

    NASA Astrophysics Data System (ADS)

    Ejenstam, Jesper; Thuvander, Mattias; Olsson, Pär; Rave, Fernando; Szakalos, Peter

    2015-02-01

    Iron-Chromium-Aluminium (Fe-Cr-Al) alloys have been widely investigated as candidate materials for various nuclear applications. Albeit the excellent corrosion resistance, conventional Fe-Cr-Al alloys suffer from α-α‧ phase separation and embrittlement when subjected to temperatures up to 500 °C, due to their high Cr-content. Low-Cr Fe-Cr-Al alloys are anticipated to be embrittlement resistant and provide adequate oxidation properties, yet long-term aging experiments and simulations are lacking in literature. In this study, Fe-10Cr-(4-8)Al alloys and a Fe-21Cr-5Al were thermally aged in the temperature interval of 450-550 °C for times up to 10,000 h, and the microstructures were evaluated mainly using atom probe tomography. In addition, a Kinetic Monte Carlo (KMC) model of the Fe-Cr-Al system was developed. No phase separation was observed in the Fe-10Cr-(4-8)Al alloys, and the developed KMC model yielded results in good agreement with the experimental data.

  12. Development of Rare-Earth Free Mn-Al Permanent Magnet Employing Powder Metallurgy Route

    NASA Astrophysics Data System (ADS)

    Singh, N.; Shyam, R.; Upadhyay, N. K.; Dhar, A.

    2015-02-01

    Most widely used high-performance permanent magnets are currently based on intermetallics of rare-earths in combination with Fe and Co. Rare-earth elements required for these magnets are getting expensive by the day. Consequently, there is a thrust worldwide to develop economical rare-earth free permanent magnets. It is acknowledged that the phase in Mn-Al alloys possesses magnetic properties without the presence of ferromagnetic elements such as Fe, Co, and Ni. In the present study, we report the synthesis of magnetic phase of Mn54Al46 alloy synthesized using mechanical alloying followed by solutionizing and annealing to obtain the desired magnetic phase. It is well known that Al dissolves partially in Mn matrix hence supersaturated solid solution of Mn54Al46 alloy powder was obtained by mechanical alloying using a planetary high-energy ball mill. For this purpose elemental Mn and Al powders were ball-milled in Argon atmosphere at 400 rpm using stainless steel bowl with ball to powder ratio of 15:1. These mechanically alloyed Mn54Al46 powders were then consolidated using spark plasma sintering at 550°C for 20 min. followed by solution treatment at 1050°C for 5 hrs and then water quenched to retain high temperature phase. Subsequently, the Mn54Al46 samples were annealed in the temperature range 450°C-650°C to obtain the magnetic phase. These samples were characterized by XRD and SEM and the magnetic properties were measured using a vibrating sample magnetometer (VSM). It was observed that the magnetization and coercivity of MnAl magnets exhibited strong dependence on annealing temperature and annealing time.

  13. Thermal and structural characterization of Cu-Al-Mn-X (Ti, Ni) shape memory alloys

    NASA Astrophysics Data System (ADS)

    Canbay, C. Aksu; Genc, Z. Karagoz; Sekerci, M.

    2014-05-01

    In this study, the Cu-Al-Mn-X (X = Ni, Ti) shape memory alloys at the range of 10-12 at.% of aluminum and 4-5 at.% manganese were produced by arc melting. We have investigated the effects of the alloying elements on the transformation temperatures, and the structural and the magnetic properties of the quaternary Cu-Al-Mn-X (X = Ni, Ti) shape memory alloys. The evolution of the transformation temperatures was studied by differential scanning calorimetry with different heating and cooling rates. The characteristic transformation temperatures and the thermodynamic parameters were highly sensitive to variations in the aluminum and manganese content, and it was observed that the nickel addition into the Cu-Al-Mn system decreased the transformation temperature although Ti addition caused an increase in the transformation temperatures. The effect of the nickel and the titanium on the thermodynamic parameters such as enthalpy and entropy values was investigated. The structural changes of the samples were studied by X-ray diffraction measurements and by optical microscope observations at room temperature. It is evaluated that the element Ni has been completely soluble in the matrix, and the main phase of the Cu-Al-Mn-Ni sample is martensite, and due to the low solubility of the Ti, the Cu-Al-Mn-Ti sample has precipitates, and a martensite phase at room temperature. The magnetic properties of the Cu-Al-Mn, Cu-Al-Mn-Ni and Cu-Al-Mn-Ti samples were investigated, and the effect of the nickel and the titanium on the magnetic properties was studied.

  14. Microstructure/Oxidation/Microhardness Correlations in Gamma-Based and Tau-Based Al-Ti-Cr Alloys

    NASA Technical Reports Server (NTRS)

    Brady, Michael P.; Smialek, J. L.; Humphrey, D. L.

    1994-01-01

    The relationships between alloy microstructure and air oxidation kinetics and alloy microstructure and microhardness in the Al-Ti-Cr system for exposures at 800 C and 1000 C were investigated. The relevant phases were identified as tau (Ll2), gamma (LIO), r-Al2Ti, TiCrAl (laves), and Cr2AI. Protective alumina formation was associated with tau, Al-rich TiCrAl, and gamma/TiCrAl mixtures. Brittleness was associated with the TiCrAl phase and tau decomposition to A12Ti + Cr2AI. It was concluded that two-phase gamma + TiCrAl alloys offer the greatest potential for oxidation resistance and room temperature ductility in the Al-Ti-Cr system.

  15. Effect of Ni content on microwave absorbing properties of MnAl powder

    NASA Astrophysics Data System (ADS)

    Wang, Zhen-zhong; Lin, Pei-hao; Huang, Wei-chao; Pan, Shun-kang; Liu, Ye; Wang, Lei

    2016-09-01

    MnAlNi powder was prepared by the process of vacuum levitation melting and high-energy ball milling, The morphology and phase structure of the powder were analyzed by Scanning Electron Microscope(SEM), X-ray diffraction(XRD) and the effect of the Ni content on microwave absorbing properties of MnAl powder was investigated by an vector network analyzer. The addition of Ni, which improved the microwave absorbing properties of MnAl powder but not changed the composition of Al8Mn5 alloy. The minimum reflectivity of (Al8Mn5)0.95Ni0.05 powder with a coating thickness (d) of 1.8 mm was about -40.8 dB and has better bandwidth effect, the absorbing mechanism of AlMnNi powders on the electromagnetic was related to the electromagnetic loss within the absorbing coatings and the effect of coating thickness on the interference loss of electromagnetic wave.

  16. Synthesis and characterization of Sr(Al,Cr) 12O 19 solid solution

    NASA Astrophysics Data System (ADS)

    Sandiumenge, Felip; Galí, Salvador

    1989-09-01

    Magnetoplumbite-type crystalline powders with SrAl 12- xCr xO 19 composition were synthesized in the range 0 ≤ x ≤ 4.4 by two different solid state reactions in air. The limited substitution of Al by trivalent Cr is accompanied by the appearance of a sesquioxide Al 2- yCr yO 3 solid solution and a new cubic phase with composition 3Al 2O 3 · SrCrO 4. These results are compared with those obtained in the synthesis of Sr(Fe,Cr) 12O 19 and Sr(Al,Fe) 12O 19 solid solutions. Finally, the cation distribution of Al and Cr in the system Sr(Al,Cr) 12O 19(Al,Cr) 2O 3 was obtained from X-ray diffraction profile analysis. The cationic distribution suggests that the solid solution range depends more on the crystal chemistry of the substitution than on the starting compounds used in the synthesis.

  17. Magnetism of hexagonal Mn{sub 1.5}X{sub 0.5}Sn (X = Cr, Mn, Fe, Co) nanomaterials

    SciTech Connect

    Fuglsby, R.; Kharel, P.; Zhang, W.; Sellmyer, D. J.; Valloppilly, S.; Huh, Y.

    2015-05-07

    Mn{sub 1.5}X{sub 0.5}Sn (X = Cr, Mn, Fe, Co) nanomaterials in the hexagonal Ni{sub 2}In-type crystal structure have been prepared using arc-melting and melt spinning. All the rapidly quenched Mn{sub 1.5}X{sub 0.5}Sn alloys show moderate saturation magnetizations with the highest value of 458 emu/cm{sup 3} for Mn{sub 1.5}Fe{sub 0.5}Sn, but their Curie temperatures are less than 300 K. All samples except the Cr containing one show spin-glass-like behavior at low temperature. The magnetic anisotropy constants calculated from the high-field magnetization curves at 100 K are on the order of 1 Merg/cm{sup 3}. The vacuum annealing of the ribbons at 550 °C significantly improved their magnetic properties with the Curie temperature increasing from 206 K to 273 K for Mn{sub 1.5}Fe{sub 0.5}Sn.

  18. Localized moment in Mn-doped γ-TiAl alloys

    NASA Astrophysics Data System (ADS)

    Coletti, J.; Suresh Babu, V.; Pavlovic, A. S.; Seehra, Mohindar S.

    1990-12-01

    For the γ-phase Ti50-xMnxAl50 alloys (x=0, 0.06, 0.77, 1.85, and 3.30), lattice parameters by x-ray diffraction and temperature dependence (5-300 K) of the magnetic susceptibility are measured. With Mn doping, the tetragonality of the L10 unit cell of γ-TiAl decreases and a localized moment μ~=2.31μB/Mn atom appears. The results can be explained in terms of Mn substituting for Ti, although a theoretical understanding of the small magnitude of the moment is still lacking.

  19. Comparative studies on the thermal stability and corrosion resistance of CrN, CrSiN, and CrSiN/AlN coatings

    SciTech Connect

    Kim, Gwang Seok; Kim, Sung Min; Lee, Sang Yul; Lee, Bo Young

    2009-07-15

    In this work, three kinds of Cr-based nitride coatings such as monolithic CrN, CrSiN coatings, and multilayered CrSiN/AlN coating with bilayer period of 3.0 nm were deposited on both Si (100) wafer and AISI H13 steel substrates by unbalanced magnetron sputtering. Thermal stability of these coatings was evaluated by annealing the coatings at temperatures between 600 and 1000 degree sign C for 30 min in air. In addition, the corrosion behaviors of these coatings were investigated by potentiodynamic polarization tests in a deaerated 3.5 wt. % NaCl solution at 40 degree sign C. Results from annealing test show the monolithic CrN and CrSiN coatings were completely oxidized after annealed at 800 and 900 degree sign C, and their cross sectional images and atomic force microscopy showed a loose and very porous morphology due to the oxidation. Also, the hardness values of the monolithic CrN and CrSiN coatings were decreased significantly from 22 and 27 GPa to 8 and 14 GPa, respectively. However, the multilayered CrSiN/AlN coating still exhibited a dense microstructure without visible change after annealed at 1000 degree sign C, and moreover, the relatively high hardness of 25 GPa was maintained. The superior thermal stability of the CrSiN/AlN multilayer coating could be attributed to the formation of the dense and stable oxidation barrier consisted of the Al{sub 2}O{sub 3}, Cr{sub 2}O{sub 3}, and amorphous SiO{sub 2} phases near the surface region, which retard the diffusion of oxygen into the coating. In the potentiodynamic polarization test results, it was found that the significantly improved corrosion resistance of the multilayered CrSiN/AlN coating was observed in comparison with those from the monolithic CrN and CrSiN coatings, and its corrosion current density (i{sub corr}) and protective efficiency were measured to be approximately 4.21 {mu}A/cm{sup 2} and 95%, respectively.

  20. Red-emitting AlN:Mn2+ phosphors prepared by combustion synthesis

    NASA Astrophysics Data System (ADS)

    Shi, Zhongqi; Zou, Yongyong; Jing, Ruifeng; Zhang, Kuo; Qiao, Guanjun; Wang, Hongjie

    2015-12-01

    Red-emitting Mn2+-doped AlN(AlN:Mn2+) phosphors were successfully prepared by a highly effective combustion synthesis method. The phase purity, morphology, element-composition and luminescence properties of the synthesized phosphors were investigated. X-ray diffraction (XRD) results show that the Mn2+-doped into the AlN host did not induce a second phase and distort the structure significantly. Scanning electron microscopy (SEM) images display that the phosphors have an irregular shape with a particle size in the range of 1-5 μm. X-ray photoelectron spectroscopy (XPS) spectrum indicates that Mn ions are divalent state. The synthesized AlN:Mn2+ phosphors exhibit a strong red emission centered at 600 nm, which is ascribe to the 4T1(4G)-6A1(6S) transition of Mn2+ under ultraviolet excitation. The emission intensity reaches its maximum when Mn2+-doped concentration is 3 mol%.

  1. An investigation of Cr(VI) removal with metallic iron in the co-presence of sand and/or MnO2.

    PubMed

    Gheju, M; Balcu, I; Vancea, C

    2016-04-01

    This study focused on the influence of sand and/or MnO2 co-presence on the mechanism and kinetics of Cr(VI) removal with Fe(0). The process was investigated under acidic and well-mixed conditions, over the temperature range of 6-32 °C. It was shown that both mechanism and kinetics of the removal process were highly dependent on composition and dose of reactive mixture added to Cr(VI) solution. At 22 °C, indirect chemical reduction with Fe(II) was the main removal path in H2O-Fe(0)-Cr(VI) and H2O-Fe(0)-Sand-Cr(VI) system, while in H2O-Fe(0)-MnO2-Cr(VI) and H2O-Fe(0)-MnO2-Sand-Cr(VI) system removal of Cr(VI) occurred mainly via adsorption on MnO2. The pseudo zero-order kinetic model provided the best match for H2O-Fe(0)-Cr(VI) and H2O-Fe(0)-Sand-Cr(VI) system, while in H2O-Fe(0)-MnO2-Cr(VI) and H2O-Fe(0)-MnO2-Sand-Cr(VI) system the process fitted well to the pseudo second-order model. Temperature influenced the efficiency and kinetics of the process in all investigated systems, and the removal mechanism only in H2O-Fe(0)-MnO2-Cr(VI) and H2O-Fe(0)-MnO2-Sand-Cr(VI) system. PMID:26826456

  2. Evaluation of Ti-48Al-2Cr-2Nb Under Fretting Conditions

    NASA Technical Reports Server (NTRS)

    Miyoshi, Kazuhisa; Lerch, Bradley A.; Draper, Susan L.; Raj, Sai V.

    2001-01-01

    The fretting behavior of Ti-48Al-2Cr-2Nb (y-TiAl) in contact with the nickel-base superalloy 718 was examined in air at temperatures from 296 to 823 K (23 to 550 C). The interfacial adhesive bonds between Ti-48Al-2Cr-2Nb and superalloy 718 were generally stronger than the cohesive bonds within Ti-48Al-2Cr-2Nb. The failed Ti-48Al-2Cr-2Nb debris subsequently transferred to the superalloy 718. In reference experiments conducted with Ti-6Al-4V against superalloy 718 under identical fretting conditions, the degree of transfer was greater for Ti-6A1-4V than for Ti-48Al-2Cr-2Nb. Wear of Ti-48Al-2Cr-2Nb generally decreased with increasing fretting frequency. The increasing rate of oxidation at elevated temperatures led to a drop in wear at 473 K. However, fretting wear increased as the temperature was increased from 473 to 823 K. At 723 and 823 K, oxide film disruption generated cracks, loose wear debris, and pits on the Ti-48Al-2Cr-2Nb wear surface. Both increasing slip amplitude and increasing load tended to produce more metallic wear debris, causing severe abrasive wear in the contacting metals.

  3. Magnetic States in Ensemble of Ferromagnetic Nanoparticles in Cu-Mn-Al Alloy.

    PubMed

    Konoplyuk, S M; Kozlova, L E; Kokorin, V V; Perekos, A O; Kolomiets, O V

    2016-12-01

    Two Cu-Mn-Al samples of different compositions were studied: one exhibiting martensitic transformation, another without structural transition. X-ray diffraction and magnetic measurements demonstrate that different magnetic behaviors of alloys originate from different concentrations and sizes of ferromagnetic nanoparticles, which appear after solid solution decomposition.Estimation of magnetic moments of ferromagnetic nanoparticles from magnetization curves was performed using Langevin function and compared to those obtained from X-ray examination. Granular systems are known to show giant magnetoresistance. Therefore, magnetoresistance of Cu-Mn-Al melt-spun ribbons after different aging times was measured. The study has shown that increase in the concentration of Mn atoms and time of aging in Cu-Mn-Al alloy leads to an increase in the amount of precipitated phase appearing as ferromagnetic nanoparticles. PMID:26762264

  4. Nanomechanical Behavior of CoCrFeMnNi High-Entropy Alloy

    NASA Astrophysics Data System (ADS)

    Mridha, Sanghita; Das, Santanu; Aouadi, Samir; Mukherjee, Sundeep; Mishra, Rajiv S.

    2015-08-01

    The nanomechanical behavior of the Co20Cr20Fe20Mn20Ni20 high-entropy alloy was investigated in as-cast, rolled, annealed, and thin-film forms. Dislocation nucleation was studied by repeated indents at a low load for each of the different processing conditions. Distinct displacement bursts (pop in) were observed in the loading curve marked by incipient plasticity for all the samples. The as-cast and annealed samples showed pop ins for 100% of the indents, whereas the rolled and thin-film samples showed a much lower fraction of displacement bursts. This was explained by the high density of dislocations for the cold-worked and thin-film conditions. The strong depth dependence of hardness was explained by geometrically necessary dislocations. The nanomechanical behavior and twinned microstructure indicate low stacking-fault energy for this high-entropy alloy.

  5. Mechanical cycling effects at Fe-Mn-Si-Cr-Ni SMAs obtained by powder metallurgy

    NASA Astrophysics Data System (ADS)

    Pricop, B.; Söyler, U.; Comčneci, R. I.; Özkal, B.; Bujoreanu, L. G.

    Specimens from Fe-Mn-Si-Cr-Ni SMA, obtained by powder metallurgy and compacted through hot rolling, were subjected to tensile loading-unloading cycles. The pseudoelastic parameters were determined based on recorded stress-strain curves, and their variation tendency with increasing the number of mechanical cycles was discussed. The gauges of tensile specimens were cut after mechanical cycling and were subjected to structural and dilatometric analysis. The structure was analyzed by XRD and SEM, aiming to reveal mechanical cycling effects. The thermomechanical response on heating, of mechanically cycled specimens, was recorded by dilatometry and revealed a tendency to enhance thermal expansion as an effect of increasing the number of cycles. The microstructural changes, induced by mechanical cycling, consisted in the stress induced formation of α' martensite.

  6. Formation of dislocations, precipitates and cavities in He-implanted Mn-Cr austenitic steels

    NASA Astrophysics Data System (ADS)

    Ruedl, E.; Valdrè, G.

    1991-03-01

    Solution-annealed discs of three Mn-Cr austenitic steels containing different amounts of C and N were uniformly implanted at 310 K with 1000 appm He corresponding to ~ 0.2 dpa. The samples were subsequently aged at temperatures from 923 to 1073 K for various times and, after electropolishing, examined by TEM, EDS and EELS. A study was made of the dislocation loops developing on aging and of the compositional changes in their neighbourhood. The formation and growth of precipitates and He-filled cavities was also investigated together with the elemental segregation to the cavity surfaces. It was found that the microstructural evolution in the three materials can take various forms depending on many parameters.

  7. FeAl underlayers for CoCrPt thin film longitudinal media

    SciTech Connect

    Lee, L.; Laughlin, D.E.; Lambeth, D.N.

    1997-04-01

    B2 ordered FeAl films with a small, uniform grain size have been produced by rf diode sputter deposition on glass substrates. CoCrPt films grown on FeAl underlayers were found to have the (10{bar 1}0) lamellar texture. The in-plane coercivities (H{sub c}) of the CoCrPt/FeAl films are comparable to those of the CoCrPt/Cr films and they can be further improved by inserting a thin Cr intermediate layer between the CoCrPt and the FeAl layers. By employing a MgO seed layer or a (002) textured Cr seed layer, (001) textured FeAl can be obtained. However, the (001) FeAl underlayer only induces a weak (11{bar 2}0) textured CoCrPt. Thus no improvement in H{sub c} over those produced on unseeded FeAl underlayers was observed. {copyright} {ital 1997 American Institute of Physics.}

  8. Structural disorder and magnetism in the spin-gapless semiconductor CoFeCrAl

    NASA Astrophysics Data System (ADS)

    Choudhary, Renu; Kharel, Parashu; Valloppilly, Shah R.; Jin, Yunlong; O'Connell, Andrew; Huh, Yung; Gilbert, Simeon; Kashyap, Arti; Sellmyer, D. J.; Skomski, Ralph

    2016-05-01

    Disordered CoFeCrAl and CoFeCrSi0.5Al0.5 alloys have been investigated experimentally and by first-principle calculations. The melt-spun and annealed samples all exhibit Heusler-type superlattice peaks, but the peak intensities indicate a substantial degree of B2-type chemical disorder. Si substitution reduces the degree of this disorder. Our theoretical analysis also considers several types of antisite disorder (Fe-Co, Fe-Cr, Co-Cr) in Y-ordered CoFeCrAl and partial substitution of Si for Al. The substitution transforms the spin-gapless semiconductor CoFeCrAl into a half-metallic ferrimagnet and increases the half-metallic band gap by 0.12 eV. Compared CoFeCrAl, the moment of CoFeCrSi0.5Al0.5 is predicted to increase from 2.01 μB to 2.50 μB per formula unit, in good agreement with experiment.

  9. Long range order and vacancy properties in Al-rich Fe{sub 3}Al and Fe{sub 3}Al(Cr) alloys

    SciTech Connect

    Kim, S.M.; Morris, D.G.

    1998-05-01

    Neutron powder diffraction measurements have been carried out in situ from room temperature to about 100 C in Fe28Al (28 at.% Al), Fe32.5Al (32.5 at.% Al) and Fe28Al15Cr (28 at.% Al, 5 at.% Cr) alloys. X-ray diffraction and TEM studies provided supporting information. The data were analyzed to obtain information about the temperature dependence of the DO{sub 3} and B2 long range order parameters, the location of the Cr atoms and their effect on the ordering energies, and on the vacancy formation and migration properties in Fe28Al and Fe32.5Al alloys. The location of the ternary alloying addition in DO{sub 3} and B2 ordered Al-rich Fe{sub 3}Al is shown to be consistent with considerations of interatomic bond energies.

  10. Dielectric relaxation and magnetodielectric response in DyMn0.5Cr0.5O3

    NASA Astrophysics Data System (ADS)

    Yuan, B.; Yang, J.; Zuo, X. Z.; Kan, X. C.; Zu, L.; Zhu, X. B.; Dai, J. M.; Song, W. H.; Sun, Y. P.

    2015-09-01

    We investigate the structural, magnetic, and magnetodielectric properties of DyMn0.5Cr0.5O3. The sample can be indexed with an orthorhombic phase with B site disordered space group Pbnm. The valence state of both Mn and Cr ions are suggested to be +3 based on the results of x-ray photoelectron spectroscopy. Two thermally excited dielectric relaxation at temperatures TN2 < T< 300 K and large magnetodielectric effect (MDC = 20%-30%) due to the disordered arrangement of Mn3+/Cr3+ ions associated with electron hopping between them are observed. The absence of any noticeable magnetoresistance effect (MR < 0.5%) demonstrates that the observed magnetodielectric effect is an intrinsic behavior. These results suggest that DyMn0.5Cr0.5O3 is a magnetodielectric compound, whose dielectric properties are dependence of the applied magnetic field, which exhibits such effects near room temperature and holds great promise for future device applications.

  11. V, Cr, and Mn in the earth, moon, EPB, and SPB and the origin of the moon - Experimental studies

    NASA Technical Reports Server (NTRS)

    Drake, Michael J.; Capobianco, Christopher J.; Newsom, Horton E.

    1989-01-01

    The abundances of V, Cr, and Mn inferred for the mantles of the earth and moon decrease in that order and are similar in both mantles (but distinct from those in the mantles of the Eucrite Parent Body and Shergottite Parent Body), suggesting a common origin for the mantles of the earth and the moon. This hypothesis was investigated on the basis of a comparison between the depletions of V, Cr, and Mn in the mantles of the earth and the moon, and the metal/silicate partition coefficients of these elements at 1260 C and 1 bar pressure among a S-bearing metallic liquid, a silicate melt, and a FeNi alloy. It was found that the earth and the moon depletions of V, Cr, and Mn are not correlated with metal/silicate partition coefficients; the V and Cr partitioned into S-rich metallic liquids under reducing conditions more strongly than Mn, consistent with the relative volatilities of these elements. This indicates that the depletion patterns of these elements in the mantles of the earth and moon cannot be attributed primarily to terrestrial core formation.

  12. The Effect of Core-Mantle Differentiation on V, Cr, and Mn: Experimental Metal/Silicate Partitioning Results

    NASA Technical Reports Server (NTRS)

    Chabot, N. L.; Agee, C. B.

    2001-01-01

    The abundances of V, Cr, and Mn are similarly depleted in the Earth and Moon. We present metal/silicate partitioning results which examine if the depletions can be explained by a core formation event. Additional information is contained in the original extended abstract.

  13. Bioaccessibility of Cr, Cu, Fe, Mg, Mn, Mo, Se and Zn from nutritional supplements by the unified BARGE method.

    PubMed

    Tokalıoğlu, Serife; Clough, Robert; Foulkes, Mike; Worsfold, Paul

    2014-05-01

    In this study, the Unified Bioaccessibility Research Group of Europe (BARGE) in vitro method was used to assess the bioaccessibility of Cr, Cu, Fe, Mg, Mn, Mo, Se, and Zn in ten nutritional supplement samples and three certified reference materials. The total digest, gastric phase and gastro-intestinal phase concentrations of Cu, Fe, Mg, Mn and Zn were determined by ICP-OES and Cr, Mo and Se by ICP-MS. The bioaccessible fractions of the elements in the gastric phase for the nutritional supplements were in the range 13-89% for Cr, 9-79% for Cu, 55-99% for Fe, 33-95% for Mg, 83-94% for Mn, 42-101% for Mo, 74-125% for Se and 81-104% for Zn. The range for the gastrointestinal phase was 6-65% for Cr, 27-66% for Cu, 3-14% for Fe, 34-91% for Mg, 53-62% for Mn, 40-109% for Mo, 53-146% for Se and 3-35% for Zn. PMID:24360457

  14. A Prussian-blue type ferrimagnet Na[MnCr(CN)6]: single crystal structure and magnetic properties.

    PubMed

    Dong, Wen; Zhu, Li-Na; Song, Hai-Bin; Liao, Dai-Zheng; Jiang, Zong-Hui; Yan, Shi-Ping; Cheng, Peng; Gao, Song

    2004-04-19

    A novel Prussian-blue type ferrimagnet Na[MnCr(CN)(6)] has been prepared and characterized by single crystal X-ray analysis and magnetic measurements. The complex has a face-centered cubic lattice and shows ferrimagnetic ordering below 60 K. PMID:15074961

  15. Thermoelectric properties of Fe and Al double substituted MnSiγ (γ~1.73)

    NASA Astrophysics Data System (ADS)

    Barczak, S. A.; Downie, R. A.; Popuri, S. R.; Decourt, R.; Pollet, M.; Bos, J. W. G.

    2015-07-01

    Two series of Fe and Al double substituted MnSiγ chimney ladders with a nominal valence electron count, VEC=14 per transition metal were prepared (γ=1.75). Simultaneous replacement of Mn with Fe and Si with Al yielded the Mn1-xFexSi1.75-xAlx series while the second Mn1-xFexSi1.75-1.75xAl2x series follows the pseudo-binary between MnSi1.75 and FeAl2. Scanning electron microscopy and elemental mapping revealed that ~60% of the nominal Al content ends up in the product with the remainder lost to sublimation, and that up to 7% Al can be substituted in the main group sublattice. Profile analysis of X-ray powder diffraction data revealed gradual changes in the cell metrics, consistent with the simultaneous substitution of Fe and Al in a fixed ratio. All samples are p-type with VEC≈13.95 from the structural data and ~1×1021 holes cm-3 from variable temperature Seebeck measurements. The substituted samples have lower electrical resistivities (ρ300 K=2-5 mΩ cm) due to an improved microstructure. This leads to increased thermoelectric power factors (largest S2/ρ=1.95 mW m-1 K-2) compared to MnSiγ. The thermal conductivity for the Mn0.95Fe0.05Si1.66Al0.1 sample is 2.7 W m-1 K-1 between 300 and 800 K, and is comparable to literature data for the parent material.

  16. Toluene removal by sequential adsorption-plasma catalytic process: Effects of Ag and Mn impregnation sequence on Ag-Mn/γ-Al2O3.

    PubMed

    Qin, Caihong; Huang, Xuemin; Dang, Xiaoqing; Huang, Jiayu; Teng, Jingjing; Kang, Zhongli

    2016-11-01

    A series of Ag-Mn/γ-Al2O3 were prepared under different Ag/Mn impregnation sequence and tested in the sequential adsorption-plasma catalytic removal of toluene. When Mn was impregnated first, the resulting catalyst, Ag-Mn(F)/γ-Al2O3, had longer breakthrough time, gave less emission of toluene, had higher CO2 selectivity, and had better carbon balance and COx yield compared to catalysts prepared via other impregnation sequences. After 120 min of NTP treatment, the carbon balance of Ag-Mn(F)/γ-Al2O3 was 91%, with 87% as COx contributions. A Brunauer-Emmett-Teller (BET) analysis and X-ray photoelectron spectroscopy (XPS) results show that, the impregnation sequence impacts the BET surface area and the ratio and existing state of Ag on the surface of the catalysts. The longer breakthrough time when using Ag-Mn(F)/γ-Al2O3 as catalyst is attributed to the large amount of Ag(+) on the surface. Ag(+) is a new active site for toluene adsorption. When Ag was impregnated first (Ag(F)-Mn/γ-Al2O3) or Ag and Mn co-impregnated (Ag-Mn-C/γ-Al2O3), the predominant specie was Ag(+). Both Ag(0) and Ag(+) species were detected on Ag-Mn(F)/γ-Al2O3. Ag(0) cooperation with MnOx may promote the migration of surface active oxygen. This would facilitate the oxidation of adsorbed toluene with CC bond already weakened by Ag(+) and would result in higher CO2 selectivity and better carbon balance as seen in the Ag-Mn(F)/γ-Al2O3 system. PMID:27494312

  17. Effect of on-site Coulomb interaction (U) on the electronic and magnetic properties of Fe2MnSi, Fe2MnAl and Co2MnGe

    NASA Astrophysics Data System (ADS)

    Sharma, Sonu; Pandey, Sudhir K.

    2016-04-01

    The electronic band structures, density of states' plots and magnetic moments of Fe2MnSi, Fe2MnAl, and Co2MnGe are studied by using the first principles calculation. The FM solutions using LSDA without U show the presence of half-metallic ferromagnetic (HFM) ground state in Fe2MnSi, whereas the ground state of Fe2MnAl is found to be metallic. In both compounds the maximum contribution to the total magnetic moment is from the Mn atom, while the Fe atom contributes very less. The electronic structures and magnetic moments of Fe-based compounds are affected significantly by U under around-the-mean-field (AMF) double counting scheme, whereas its effect is very less on Co2MnGe. The magnetic moment of Fe atom in Fe2MnSi (Fe2MnAl) increased by ∼70% (∼75%) and in Mn atom it decreases by ∼50% (∼70%) when the value of U is increased from 1 to 5 eV. Hund's like exchange interactions are increasing in Fe atom while decreasing in Mn atom with increase in U. The Fe and Mn moments are ferromagnetically coupled in Fe2MnSi for all values of U, whereas in Fe2MnAl they are coupled antiferromagnetically below U=2 eV and ferromagnetically above it. Above U=2 eV the metallic ground state of Fe2MnAl changes to semiconducting ground state and the ferromagnetic coupling between Fe and Mn atoms appears to be responsible for this. This shows that the validity of AFM double counting scheme is not robust for the entire range of U in the Fe2MnAl compound.

  18. The effect of disorder on the electronic and magnetic properties of Mn2CoAl/GaAs heterostructures

    NASA Astrophysics Data System (ADS)

    Feng, Yu; Tian, Chun-lin; Yuan, Hong-kuan; Kuang, An-long; Chen, Hong

    2015-11-01

    We study the effect of disorder, including swap and antisite, on the electronic and magnetic properties of heterostructures by using extensive first-principles calculations within density functional theory. Thirteen kinds of swap disorders and sixteen kinds of antisite disorders are proposed and studied comprehensively. Our calculation reveals that disorders at the interface have low formation energies, indicating that disorders are most likely to appear at the interface instead of the deep layer. Among all kinds of disorders, Mn1(Al) (where the interface Mn is occupied by an Al atom) and Mn1(As) (where the interface Mn is occupied by an As atom from a GaAs slab) antisite disorders possess the lowest formation energies. This shows that the interface Mn has a higher probability of being replaced by an Al atom, and that an As atom from a GaAs slab easily diffuses into a Mn2CoAl slab and occupies the position of the interface Mn. Moreover, further study on the interface electronic structure reveals that interface spin polarization suffers dramatic reduction due to Mn1(Al) and Mn1(As) antisite disorders. It can be deduced that the interface state, together with Mn1(Al) and Mn1(As) antisite disorders, may be the main causes of the low TMR ratio of Mn2CoAl/GaAs heterostructures.

  19. Microstructure evolution during annealing of TiAl/NiCoCrAl multilayer composite prepared by EB-PVD

    SciTech Connect

    Zhang, Rubing; Zhang, Deming; Chen, Guiqing; Wang, Yuesheng

    2014-07-01

    TiAl/NiCoCrAl laminate composite sheet with a thickness of 0.4–0.6 mm as well as a dimension of 150 mm × 100 mm was fabricated successfully by using electron beam physical vapor deposition (EB-PVD) method. The annealing treatment was processed at 1123 and 1323 K for 3 h in a high vacuum atmosphere, respectively. The phase composition and microstructure of TiAl/NiCoCrAl microlaminated sheet have been analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Based on the sheet characterization and results of the microstructure evolution during annealing treatment process, the diffusion mechanism of interfacial reaction in TiAl/NiCoCrAl microlaminate was investigated and discussed.

  20. Irradiation-enhanced α' precipitation in model FeCrAl alloys

    DOE PAGESBeta

    Edmondson, Philip D.; Briggs, Samuel A.; Yamamoto, Yukinori; Howard, Richard H.; Sridharan, Kumar; Terrani, Kurt A.; Field, Kevin G.

    2016-02-17

    Model FeCrAl alloys with varying compositions (Fe(10–18)Cr(10–6)Al at.%) have been neutron irradiated at ~ 320 to damage levels of ~ 7 displacements per atom (dpa) to investigate the compositional influence on the formation of irradiation-induced Cr-rich α' precipitates using atom probe tomography. In all alloys, significant number densities of these precipitates were observed. Cluster compositions were investigated and it was found that the average cluster Cr content ranged between 51.1 and 62.5 at.% dependent on initial compositions. This is significantly lower than the Cr-content of α' in binary FeCr alloys. As a result, significant partitioning of the Al from themore » α' precipitates was also observed.« less

  1. 1100 to 1500 K Slow Plastic Compressive Behavior of NiAl-xCr Single Crystals

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. Daniel; Darolia, Ram

    2003-01-01

    The compressive properties of near <001> and <111> oriented NiAl-2Cr single crystals and near <011> oriented NiAl-6Cr samples have been measured between 1100 and 1500 K. The 2Cr addition produced significant solid solution strengthening in NiAl, and the <111> and <001> single crystals possessed similar strengths. The 6Cr crystals were not stronger than the 2Cr versions. At 1100 and 1200 K plastic flow in all three Cr-modified materials was highly dependent on stress with exponents > 10. The <011> oriented 6Cr alloy exhibited a stress exponent of about 8 at 1400 and 1500 K; whereas both <001> and <111> NiAl-2Cr crystals possessed stress exponents near 3 which is indicative of a viscous dislocation glide creep mechanism. While the Cottrell-Jaswon solute drag model predicted creep rates within a factor of 3 at 1500 K for <001>-oriented NiAl-2Cr; this mechanism greatly over predicted creep rates for other orientations and at 1400 K for <001> crystals.

  2. Diffusional transport during the cyclic oxidation of gamma + beta, Ni-Cr-Al(Y, Zr) alloys

    NASA Technical Reports Server (NTRS)

    Nesbitt, J. A.; Heckel, R. W.

    1988-01-01

    The cyclic oxidation behavior of several cast gamma + beta, Ni-Cr-Al(Y, Zr) alloys and one low-pressure plasma spraying gamma + beta, Ni-Co-Cr-Al(Y) alloy was studied. Cyclic oxidation was found to result in a decreasing Al concentration at the oxide-metal interface due to a high rate of Al consumption coupled with oxide scale cracking and spalling. Diffusion paths plotted on the ternary phase diagram showed higher Ni concentrations with increasing cyclic oxidation exposures. The alloy with the highest rate of Al consumption and the highest Al content underwent breakaway oxidation following 500 1-hr cycles at 1200 C.

  3. Microstructures and mechanical properties of compositionally complex Co-free FeNiMnCr18 FCC solid solution alloy

    DOE PAGESBeta

    Wu, Z.; Bei, H.

    2015-07-01

    Recently, a structurally-simple but compositionally-complex FeNiCoMnCr high entropy alloy was found to have excellent mechanical properties (e.g., high strength and ductility). To understand the potential of using high entropy alloys as structural materials for advanced nuclear reactor and power plants, it is necessary to have a thorough understanding of their structural stability and mechanical properties degradation under neutron irradiation. Furthermore, this requires us to develop a similar model alloy without Co because material with Co will make post-neutron-irradiation testing difficult due to the production of the 60Co radioisotope. In order to achieve this goal, a FCC-structured single-phase alloy with amore » composition of FeNiMnCr18 was successfully developed. This near-equiatomic FeNiMnCr18 alloy has good malleability and its microstructure can be controlled by thermomechanical processing. By rolling and annealing, the as-cast elongated-grained-microstructure is replaced by homogeneous equiaxed grains. The mechanical properties (e.g., strength and ductility) of the FeNiMnCr18 alloy are comparable to those of the equiatomic FeNiCoMnCr high entropy alloy. Both strength and ductility increase with decreasing deformation temperature, with the largest difference occurring between 293 and 77 K. Extensive twin-bands which are bundles of numerous individual twins are observed when it is tensile-fractured at 77 K. No twin bands are detected by EBSD for materials deformed at 293 K and higher. Ultimately the unusual temperature-dependencies of UTS and uniform elongation could be caused by the development of the dense twin substructure, twin-dislocation interactions and the interactions between primary and secondary twinning systems which result in a microstructure refinement and hence cause enhanced strain hardening and postponed necking.« less

  4. Tribological Properties of the Fe-Al-Cr Alloyed Layer by Double Glow Plasma Surface Metallurgy

    NASA Astrophysics Data System (ADS)

    Luo, Xixi; Yao, Zhengjun; Zhang, Pingze; Zhou, Keyin; Wang, Zhangzhong

    2016-07-01

    A Fe-Al-Cr alloyed layer was deposited onto the surface of Q235 low-carbon steel via double glow plasma surface metallurgy (DGPSM) to improve the steel's wear resistance. After the DGPSM treatment, the Fe-Al-Cr alloyed layer grown on the Q235 low-carbon steel was homogeneous and compact and had a thickness of 25 µm. The layer was found to be metallurgically adhered to the substrate. The frictional coefficient and specific wear rate of the sample with a Fe-Al-Cr alloyed layer (treated sample) were both lower than those of the bare substrate (untreated sample) at the measured temperatures (25, 250 and 450 °C). The results indicated that the substrate and the alloyed layer suffered oxidative wear and abrasive wear, respectively, and that the treated samples exhibited much better tribological properties than did the substrate. The formation of Fe2AlCr, Fe3Al(Cr), FeAl(Cr), Fe(Cr) sosoloid and Cr23C6 phases in the alloyed layer dramatically enhanced the wear resistance of the treated sample. In addition, the alloyed layer's oxidation film exhibited a self-healing capacity with lubrication action that also contributed to the improvement of the wear resistance at high temperature. In particular, at 450 °C, the specific wear rate of treated sample was 2.524 × 10-4 mm3/N m, which was only 45.2% of the untreated sample.

  5. Low-moment ferrimagnetic phase of the Heusler compound Cr2CoAl

    NASA Astrophysics Data System (ADS)

    Jamer, Michelle E.; Marshall, Luke G.; Sterbinsky, George E.; Lewis, Laura H.; Heiman, Don

    2015-11-01

    Synthesizing half-metallic fully compensated ferrimagnets that form in the inverse Heusler phase could lead to superior spintronic devices. These materials would have high spin polarization at room temperature with very little fringing magnetic fields. Previous theoretical studies indicated that Cr2CoAl should form in a stable inverse Heusler lattice due to its low activation energy. Here, stoichiometric Cr2CoAl samples were arc-melted and annealed at varying temperatures, followed by studies of their structural and magnetic properties. High-resolution synchrotron X-ray diffraction revealed a chemically ordered Heusler phase in addition to CoAl and Cr phases. Soft X-ray magnetic circular dichroism revealed that the Cr and Co magnetic moments are antiferromagnetically oriented leading to the observed low magnetic moment in Cr2CoAl.

  6. Comparison in mechanical and tribological properties of CrTiAlMoN and CrTiAlN nano-multilayer coatings deposited by magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Wang, Tao; Zhang, Guojun; Jiang, Bailing

    2016-02-01

    CrTiAlN and CrTiAlMoN nano-multilayer coatings were deposited by closed field unbalanced magnetron sputtering. TiMoN and CrTiMoN nano-multilayer coatings with same Mo2N layer thickness were also prepared for comparison. The structure of these coatings is investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The mechanical and tribological properties were characterized and compared by nano-indentation and ball-on-disc test. It was found that these coatings were structured by fcc metal nitride phases (including CrN, TiN, AlN and Mo2N) and the preferred orientation changed from (1 1 1) to (2 0 0) with the increase of Mo content. The TEM results showed that the coatings exhibited typical columnar structure and nano-multilayer structure with modulation periods ranged from 3.2 nm to 7.6 nm. Among these coatings, CrTiAlMoN coatings presented the highest hardness, lowest coefficient of friction (COF) and wear rate. The hardness of these nano-multilayer coatings were determined by layer interfaces: TiN/Mo2N and AlN/Mo2N layer interface showed benefit on hardness enhancement while CrN/Mo2N layer interface led to a great hardness decrement. In comparison with the other as-deposited coatings, the low COF of CrTiAlMoN coatings was not only affected by Mo addition but also related to its oxidation behaviors.

  7. Development of ODS FeCrAl alloys for accident-tolerant fuel cladding

    SciTech Connect

    Dryepondt, Sebastien N.; Hoelzer, David T.; Pint, Bruce A.; Unocic, Kinga A.

    2015-09-18

    FeCrAl alloys are prime candidates for accident-tolerant fuel cladding due to their excellent oxidation resistance up to 1400 C and good mechanical properties at intermediate temperature. Former commercial oxide dispersion strengthened (ODS) FeCrAl alloys such as PM2000 exhibit significantly better tensile strength than wrought FeCrAl alloys, which would alloy for the fabrication of a very thin (~250 m) ODS FeCrAl cladding and limit the neutronic penalty from the replacement of Zr-based alloys by Fe-based alloys. Several Fe-12-Cr-5Al ODS alloys where therefore fabricated by ball milling FeCrAl powders with Y2O3 and additional oxides such as TiO2 or ZrO2. The new Fe-12Cr-5Al ODS alloys showed excellent tensile strength up to 800 C but limited ductility. Good oxidation resistance in steam at 1200 and 1400 C was observed except for one ODS FeCrAl alloy containing Ti. Rolling trials were conducted at 300, 600 C and 800 C to simulate the fabrication of thin tube cladding and a plate thickness of ~0.6mm was reached before the formation of multiple edge cracks. Hardness measurements at different stages of the rolling process, before and after annealing for 1h at 1000 C, showed that a thinner plate thickness could likely be achieved by using a multi-step approach combining warm rolling and high temperature annealing. Finally, new Fe-10-12Cr-5.5-6Al-Z gas atomized powders have been purchased to fabricate the second generation of low-Cr ODS FeCrAl alloys. The main goals are to assess the effect of O, C, N and Zr contents on the ODS FeCrAl microstructure and mechanical properties, and to optimize the fabrication process to improve the ductility of the 2nd gen ODS FeCrAl while maintaining good mechanical strength and oxidation resistance.

  8. NMR study of the ternary carbides M2 AlC (M=Ti,V,Cr)

    NASA Astrophysics Data System (ADS)

    Lue, C. S.; Lin, J. Y.; Xie, B. X.

    2006-01-01

    We have performed a systematic study of the layered ternary carbides Ti2AlC , V2AlC , and Cr2AlC using Al27 NMR spectroscopy. The quadrupole splittings, Knight shifts, as well as spin-lattice relaxation times on each material have been identified. The sign of the isotropic Knight shift varies from positive for Ti2AlC and V2AlC to negative for Cr2AlC , attributed to the enhancement of hybridization with increasing valence electron count in the transition metal. Universally long relaxation times are found for these alloys. Results provide a measure of Al-s Fermi-level density of states Ns(EF) for Ti2AlC and V2AlC . In addition, the evidence that Ns(EF) correlates with the transition metal d -electron count has been explored in the present NMR investigation.

  9. First-principles study of Mn adsorption on Al4C3(0 0 0 1) surface

    NASA Astrophysics Data System (ADS)

    Yao, L. F.; Li, K.; Zhou, N. G.

    2016-02-01

    First-principle calculation based on the density functional theory was adopted to investigate the adsorption energy, stability, electronic structure and bonding of Mn atom adsorption on Al-terminated and C-terminated Al4C3(0 0 0 1) surface under 0.25 ML and 0.5 ML. Results show that the structure of Mn adsorption on C-terminated Al4C3(0 0 0 1) surface is more stable than that on Al-terminated surface according to the formation energy calculation. For Mn adsorption on Al-terminated surface, Mn is more favorable to reside at the site H1 comparing with other sites. As well, for Mn adsorption on C-terminated surface, the structure of Mn adsorption at site H‧1 is the most stable one. By analyzing the electronic structure and bonding, it is found that the mixed metallic/covalent bonds are formed between Mn atoms and Al-terminated surface, while the covalent bonds are formed between Mn atoms and C-terminated surface. According to the interlayer spacing calculation, Al4C3(0 0 0 1) surfaces are reconstructed after Mn adsorption, which in turn affect the following stacking of Mg atoms on Al4C3(0 0 0 1) surface. The above analysis provided effective theoretical support to the experimental phenomenon that high Mn content has negative influence on the heterogeneous nucleation of Al4C3 particles for α-Mg grains.

  10. The influence of Cr and Al pack cementation on low carbon steel to improve oxidation resistance

    NASA Astrophysics Data System (ADS)

    Prasetya, Didik; Sugiarti, Eni; Destyorini, Fredina; Thosin, Kemas Ahmad Zaini

    2012-06-01

    Pack chromizing and aluminizing has been widely used for many years to improve hot temperature oxidation and corrosion resistance of metals. The coating process involves packing the steel in a powder mixture which contain aluminum and chromium source, and inert filler (usually alumina), and halide activator NH4Cl. Al and Cr were deposited onto carbon steel by pack cementation process using elemental Al and Cr powder as Al and Cr source, whereas NiCo alloys codeposited by electrodeposition. The position of Al and Cr could be under or over Ni-Co alloys deposited. Pack cementation was heated on dry inert gas at temperature 800 °C about 5 hours and 20 minute for Cr and Al respectively. Al and Cr was successfully deposited. Laying down effect of Al and Cr onto carbon steel whether up and down toward NiCo alloys coating have affected to oxidation resistance. The pack aluminizing as top layer given best resitance to restrain excessive oxide scale, in contrast pack chromizing reveal bad oxidation resistance, moreover occured spallation on layer.

  11. Correlation of EMR and optical spectroscopy data for Cr3+ and Mn2+ ions doped into yttrium aluminum borate YAl3(BO3)4 crystal - Extracting low symmetry aspects

    NASA Astrophysics Data System (ADS)

    Rudowicz, Czesław; Gnutek, Paweł; Açıkgöz, Muhammed

    2015-08-01

    In this study, the crystal field analysis for Cr3+ and Mn2+ ions doped into yttrium aluminum borate YAl3(BO3)4, for short YAB, crystal has been carried out to complement earlier study of the zero-field splitting (ZFS) parameters (ZFSPs). This analysis utilizes data on the distortion models obtained from analysis of the ZFSPs obtained experimentally by EMR for Cr3+ and Mn2+ ions at the Y3+ and Al3+ sites in YAB. This approach enables to verify and enhance reliability of the ZFSP modeling based on superposition model (SPM) analysis and the distortion models predicted previously. Subsequently, modeling of the crystal field parameters (CFPs) based on SPM analysis is carried out for Cr3+ and Mn2+ ions located at possible cation sites in YAB. The SPM predicted CFP values serve as input for the Crystal Field Analysis (CFA) package to calculate the CF energy levels. The predicted physical ZFS of the ground spin state, i.e. the 4A2 state for Cr3+ ion and the 6S state Mn2+ ions, enable calculation of the theoretical ZFSP values, D and D & (a-F), respectively, using the microscopic spin Hamiltonian (MSH) module in the CFA package. In this way, data on the distortions around the Cr3+ centers in YAB (and to a certain extent also for Mn2+ centers) obtained using the ZFSP data from EMR measurements may be correlated with data on the CF energy levels measured by optical spectroscopy. This modeling approach uncovers certain incompatibilities in the existing data for Cr3+:YAB, which call for reanalysis of the previous assignments of the energy levels observed in optical spectra and more accurate experimental data.

  12. Kinetics of borided 31CrMoV9 and 34CrAlNi7 steels

    SciTech Connect

    Efe, Goezde Celebi; Ipek, Mediha; Ozbek, Ibrahim; Bindal, Cuma

    2008-01-15

    In this study, kinetics of borides formed on the surface of 31CrMoV9 and 34CrAlNi7 steels borided in solid medium consisting of Ekabor II at 850-900-950 deg. C for 2, 4, 6 and 8 h were investigated. Scanning electron microscopy and optical microscopy examinations showed that borides formed on the surface of borided steels have columnar morphology. The borides formed in the coating layer confirmed by X-ray diffraction analysis are FeB, Fe{sub 2}B, CrB, and Cr{sub 2}B. The hardnesses of boride layers are much higher than that of matrix. It was found that depending on process temperature and time the fracture toughness of boride layers ranged from 3.93 to 4.48 MPa m{sup 1/2} for 31CrMoV9 and from 3.87 to 4.40 MPa m{sup 1/2} for 34CrAlNi7 steel. Activation energy, growth rate and growth acceleration of boride layer calculated according to these kinetic studies revealed that lower activation energy results in the fast growth rate and high growth acceleration.

  13. Solid state reduction of chromium (VI) pollution for Al2O3-Cr metal ceramics application

    NASA Astrophysics Data System (ADS)

    Zhu, Hekai; Fang, Minghao; Huang, Zhaohui; Liu, Yangai; Tang, Hao; Min, Xin; Wu, Xiaowen

    2016-04-01

    Reduction of chromium (VI) from Na2CrO4 through aluminothermic reaction and fabrication of metal-ceramic materials from the reduction products have been investigated in this study. Na2CrO4 could be successfully reduced into micrometer-sized Cr particles in a flowing Ar atmosphere in presence of Al powder. The conversion ratio of Na2CrO4 to metallic Cr attained 96.16% efficiency. Al2O3-Cr metal-ceramic with different Cr content (5 wt%, 10 wt%, 15 wt%, 20 wt%) were further prepared from the reduction product Al2O3-Cr composite powder, and aluminum oxide nanopowder via pressure-less sintering. The phase composition, microstructure and mechanical properties of metal-ceramic composites were characterized to ensure the potential of the Al2O3-Cr composite powder to form ceramic materials. The highest relative density and bending strength can reach 93.4% and 205 MP, respectively. The results indicated that aluminothermic reduction of chromium (VI) for metal-ceramics application is a potential approach to remove chromium (VI) pollutant from the environment.

  14. Pack cementation Cr-Al coating of steels and Ge-doped silicide coating of Cr-Nb alloy

    SciTech Connect

    He, Y.R.; Zheng, M.H.; Rapp, R.A.

    1995-08-01

    Carbon steels or low-alloy steels used in utility boilers, heat exchangers, petrochemical plants and coal gasification systems are subjected to high temperature corrosion attack such as oxidation, sulfidation and hot corrosion. The pack cementation coating process has proven to be an economical and effective method to enhance the corrosion resistance by modifying the surface composition of steels. With the aid of a computer program, STEPSOL, pack cementation conditions to produce a ferrite Cr-Al diffusion coating on carbon-containing steels by using elemental Cr and Al powders have been calculated and experimentally verified. The cyclic oxidation kinetics for the Cr-Al coated steels are presented. Chromium silicide can maintain high oxidation resistance up to 1100{degrees}C by forming a SiO{sub 2} protective scale. Previous studies at Ohio State University have shown that the cyclic oxidation resistance of MOSi{sub 2} and TiSi{sub 2} can be further improved by Ge addition introduced during coating growth. The halide-activated pack cementation process was modified to produce a Ge-doped silicide diffusion coating in a single processing step for the ORNL-developed Cr-Nb advanced intermetallic alloy. The oxidation behavior of the silicide-coated Cr-Nb alloy was excellent: weight gain of about 1 mg/cm{sup 2} upon oxidation at 1100{degrees}C in air for 100 hours.

  15. Evaluation of Al3Mg2 precipitates and Mn-rich phase in aluminum-magnesium alloy based on scanning transmission electron microscopy imaging

    SciTech Connect

    Zhu, Yakun; Cullen, David A; Kar, Soumya; Free, Michael P; Allard Jr, Lawrence Frederick

    2012-01-01

    Scanning transmission electron microscopy (STEM) and energy dispersive X-ray spectroscopy (EDS) were used to observe intergranular and intragranular -phase (Al3Mg2) formation and growth in as-received sample and long-term (~ 1 year) thermally treated samples of 5083-H131 alloy. Rod-shaped and equiaxed particles rich in Mn, Fe, and Cr were present in the as-received and heat treated samples. The -phase precipitated along grain boundaries as well as around and between preexisting Mn-Fe-Cr rich particles. The measured thickness of -phase along grain boundaries was lower than Zener Hillert diffusion model predicted value and the potential reasons were theoretically analyzed. Dislocation networks, grain boundaries, and different preexisting particles were observed to contribute to Mg diffusion and -phase precipitation.

  16. Al-21Ti-23Cr high-temperature protective coating on TiAl intermetallic compounds by RF magnetron sputtering

    SciTech Connect

    Park, J.Y.; Lee, H.N.; Wee, D.M.; Park, S.W.; Oh, M.H.

    1997-12-31

    Ti-48Al specimens were coated with Al-21Ti-23Cr film at 200 W, 0.8 Pa and 573 K by RF magnetron sputtering. The oxidation behavior of the coated specimens was investigated through isothermal and cyclic oxidation tests, and the tensile deformation properties of the coated specimens were also investigated before and after oxidation. The isothermal and cyclic oxidation curves showed that the Al-21Ti-23Cr film was very effective in decreasing the oxidation rate of Ti-48Al. This excellent oxidation resistance is attributable to the formation of a protective Al{sub 2}O{sub 3} layer on the surface of the Al-21Ti-23Cr film. It was found from the results of the tensile test that the protective Al{sub 2}O{sub 3} layer on the surface of the Al-21Ti-23Cr film enabled the Ti-48Al to maintain its tensile properties in an oxidizing environment.

  17. CONSTITUTIVE BEHAVIOR OF AS-QUENCHED Al-Cu-Mn ALLOY

    NASA Astrophysics Data System (ADS)

    Yang, Xia-Wei; Zhu, Jing-Chuan; Nong, Zhi-Sheng; Ye, Mao; Lai, Zhong-Hong; Liu, Yong

    2013-07-01

    The hot flow stress of as-quenched Al-Cu-Mn alloy was modeled using the constitutive equations. The as-quenched Al-Cu-Mn alloy were treated with isothermal hot compression tests in the temperature range of 350-500°C, the strain rate range of 0.001-1 s-1. The hyperbolic sine equation was found to be appropriate for flow stress modeling and prediction. Based on the hyperbolic sine equation, a constitutive equation is a relation between 0.2 pct yield stress and deformation conditions (strain rate and deformation temperature) was established. The corresponding hot deformation activation energy (Q) for as-quenched Al-Cu-Mn alloy was determined to be 251.314 kJ/mol. Parameters of constitutive equation of as-quenched Al-Cu-Mn alloy were calculated at different small strains (≤ 0.01). The calculated flow stresses from the constitutive equation are in good agreement with the experimental results. Therefore, this constitutive equation can be used as an accurate temperature-stress model to solve the problems of quench distortion of Al-Cu-Mn alloy parts.

  18. Thermodynamic analysis of chemical compatibility of several compounds with Fe-Cr-Al alloys

    NASA Technical Reports Server (NTRS)

    Misra, Ajay K.

    1993-01-01

    Chemical compatibility between Fe-19.8Cr-4.8Al (weight percent), which is the base composition for the commercial superalloy MA956, and several carbides, borides, nitrides, oxides, and silicides was analyzed from thermodynamic considerations. The effect of addition of minor alloying elements, such as Ti, Y, and Y2O3, to the Fe-Cr-Al alloy on chemical compatibility between the alloy and various compounds was also analyzed. Several chemically compatible compounds that can be potential reinforcement materials and/or interface coating materials for Fe-Cr-Al based composites were identified.

  19. Spectroscopic properties of {Cr}^{3+} in the spinel solid solution {ZnAl}_{2-x}{Cr}x{O}_4

    NASA Astrophysics Data System (ADS)

    Verger, Louisiane; Dargaud, Olivier; Rousse, Gwenaelle; Rozsályi, Emese; Juhin, Amélie; Cabaret, Delphine; Cotte, Marine; Glatzel, Pieter; Cormier, Laurent

    2016-01-01

    The evolution of the structural environment of {Cr}{^{3+}} along the solid solution {ZnAl}_{2-x}{Cr}x{O}_4 has been investigated using a multi-analytical approach. X-ray diffraction confirms that the system follows Vegard's law. Diffuse reflectance spectra show a decrease of the crystal field parameter with the Cr content, usually related to the increase of the Cr-O bond length in a point charge model. This interpretation is discussed and compared to the data obtained by first-principle calculations based on density functional theory. X-ray absorption near edge structure spectra at the Cr K-edge show a pronounced evolution in the pre-edge with the Cr content, characterised by the appearance of a third feature. Calculations enable to assign the origin of this feature to Cr neighbours. The colour change from pink to brownish pink and eventually green along the solid solution has also been quantified by calculating the L*, a*, b* and x, y coefficients in the system defined by the International Commission on Illumination.

  20. Oxidation behavior of arc evaporated Al-Cr-Si-N thin films

    SciTech Connect

    Tritremmel, Christian; Daniel, Rostislav; Mitterer, Christian; Mayrhofer, Paul H.; Lechthaler, Markus; Polcik, Peter

    2012-11-15

    The impact of Al and Si on the oxidation behavior of Al-Cr-(Si)-N thin films synthesized by arc evaporation of powder metallurgically prepared Al{sub x}Cr{sub 1-x} targets with x = Al/(Al + Cr) of 0.5, 0.6, and 0.7 and (Al{sub 0.5}Cr{sub 0.5}){sub 1-z}Si{sub z} targets with Si contents of z = 0.05, 0.1, and 0.2 in N{sub 2} atmosphere was studied in detail by means of differential scanning calorimetry, thermogravimetric analysis (TGA), x-ray diffraction, and Raman spectroscopy. Dynamical measurements in synthetic air (up to 1440 Degree-Sign C) revealed the highest onset temperature of pronounced oxidation for nitride coatings prepared from the Al{sub 0.4}Cr{sub 0.4}Si{sub 0.2} target. Isothermal TGA at 1100, 1200, 1250, and 1300 Degree-Sign C highlight the pronounced improvement of the oxidation resistance of Al{sub x}Cr{sub 1-x}N coatings by the addition of Si. The results show that Si promotes the formation of a dense coating morphology as well as a dense oxide scale when exposed to air.

  1. Ultrafast optical studies on GaAs/AlGaAs/GaMnAs quantum wells

    NASA Astrophysics Data System (ADS)

    Schulz, R.; Korn, T.; Wurstbauer, U.; Schuh, D.; Wegscheider, W.; Schüller, C.

    2010-01-01

    GaMnAs is a highly interesting material system for future spintronic devices. We present a study of nonmagnetic GaAs quantum wells (QW) embedded in AlGaAs barriers, close to a ferromagnetic GaMnAs layer. The samples were grown on semi-insulating GaAs(001) and contain two QWs, where one QW is close to the GaMnAs layer and the other one is farther away (120 nm), and serves as a reference. We studied the influence of the barrier material, e.g. a short-period AlAs/GaAs superlattice. The photoluminescence (PL) of the upper QWs, close to the GaMnAs layer, show a significant broadening. Additionally, time-resolved Faraday rotation (TRFR) reveals that the spin lifetime in the upper QW is up to 30 times longer than that in the lower QW. We attribute these observations to backdiffusion of Mn into the QW during and after growth. Both, the PL and the TRFR, are highly sensitive to small quantities (below 0.05 %) of Mn and allow us to study the efficiency of barrier layers in suppressing Mn diffusion.

  2. Study of the effect of different fermenting microorganisms on the Se, Cu, Cr, and Mn contents in fermented goat and cow milks.

    PubMed

    Quintana, Aida Verónica; Olalla-Herrera, Manuel; Ruiz-López, María Dolores; Moreno-Montoro, Miriam; Navarro-Alarcón, Miguel

    2015-12-01

    The aim of this study was to determine the Se, Cu, Cr, and Mn concentrations of different types of goat- and cow-milk fermented products and evaluate the influence of fermenting bacteria (classical fermenting starters and a probiotic strain) on these concentrations. Atomic absorption spectrometry with hydride generation was used to measure Se and electrothermal atomization to measure Cu, Cr and Mn. Analytical parameters determined in the fermented milks demonstrated that the procedures used were adequate for Se, Cu, Cr, and Mn analyses. Se levels were significantly lower in fermented goat milk products than in fermented cow milk products (p<0.05). Se, Cu, Cr, and Mn levels did not differ as a function of the fermenting bacteria used in commercial fermented goat or cow milks or in the lab-produced goat yoghurt. Given the Se, and Cr intakes for healthy adults, goat and cow yogurts may be important dietary sources. PMID:26041187

  3. An experimental and thermodynamic equilibrium investigation of the Pb, Zn, Cr, Cu, Mn and Ni partitioning during sewage sludge incineration.

    PubMed

    Liu, Jingyong; Fu, Jiewen; Ning, Xun'an; Sun, Shuiyu; Wang, Yujie; Xie, Wuming; Huang, Shaosong; Zhong, Sheng

    2015-09-01

    The effects of different chlorides and operational conditions on the distribution and speciation of six heavy metals (Pb, Zn, Cr, Cu, Mn and Ni) during sludge incineration were investigated using a simulated laboratory tubular-furnace reactor. A thermodynamic equilibrium investigation using the FactSage software was performed to compare the experimental results. The results indicate that the volatility of the target metals was enhanced as the chlorine concentration increased. Inorganic-Cl influenced the volatilization of heavy metals in the order of Pb>Zn>Cr>Cu>Mn>Ni. However, the effects of organic-Cl on the volatility of Mn, Pb and Cu were greater than the effects on Zn, Cr and Ni. With increasing combustion temperature, the presence of organic-Cl (PVC) and inorganic-Cl (NaCl) improved the transfer of Pb and Zn from bottom ash to fly ash or fuse gas. However, the presence of chloride had no obvious influence on Mn, Cu and Ni. Increased retention time could increase the volatilization rate of heavy metals; however, this effect was insignificant. During the incineration process, Pb readily formed PbSiO4 and remained in the bottom ash. Different Pb compounds, primarily the volatile PbCl2, were found in the gas phase after the addition of NaCl; the dominant Pb compounds in the gas phase after the addition of PVC were PbCl2, Pb(ClO4)2 and PbCl2O4. PMID:26354691

  4. Effects of Mn content on the deformation behavior of Fe-Mn-Al-C TWIP steels — A computational study

    SciTech Connect

    Wang, Yuan; Sun, Xin; Wang, Y. D.; Zbib, Hussein M.

    2015-04-01

    This paper presents a double-slip/double-twin polycrystal plasticity model using finite element solution to investigate the kinetics of deformation twinning of low-to-medium manganese (Mn) twinning-induced plasticity (TWIP) steels. Empirical equations are employed to estimate the stacking fault energy (SFE) of TWIP steels and the critical resolved shear stress (CRSS) for dislocation slip and deformation twinning, respectively. The results suggest that the evolution of twinning in Fe-xMn-1.4Al-0.6C (x=11.5, 13.5, 15.5, 17.5 and 19.5) TWIP steels, and its relation to the Mn content, can explain the effect of Mn on mechanical properties.the stress-strain. By comparing the double-slip/double-twin model to a double-slip model, the predicted results essentially reveal that the interaction behavior between dislocation slip and deformation twinning can lead to an additional work hardening. Also, numerical simulations are carried out to study the influence of boundary conditions on deformation behavior and twin formation. The nucleation and growth of twinning are found to depend on internal properties (e.g., mismatch orientation of grains and stress redistribution) as well as on external constraints (e.g., the applied boundary conditions) of the material.

  5. Study on the growth and corrosion resistance of manganese phosphate coatings on 30CrMnMoTi alloy steel

    NASA Astrophysics Data System (ADS)

    Fang, Liang; Xie, Liang-bo; Hu, Jia; Li, Yun; Zhang, Wen-ting

    Due to containing some alloy elements such as chromium, 30CrMnMoTi steel is usually difficult to be phosphated. In present paper, the growth process of the phosphate coating on 30CrMnMoTi alloy steel fabricated by a high temperature manganese phosphating was investigated. The microstructure, surface morphology, composition and corrosion resistance of the phosphate coatings were analyzed by XRD, SEM, EDS and electrochemical polarization method, respectively. The time dependence of open circuit potential (OCP) and the weight of the coating were also measured. It is found that the phosphate coating is mainly composed of (Mn,Fe)5H2(PO4)4·4H2O and consists of a lot of close packed lump crystallites. Based on the time dependence of morphology and the weight of phosphate films, it shows that the phosphating process mainly includes three stages: corrosion of the substrate, creation and growth of phosphate crystal nucleus and thickening of phosphate coating. For 30CrMnMoTi steel, it takes at least 30 seconds and 3 minutes for the first and second step, respectively: at the beginning stage of phospahting process, a lot of bubbles emit, then a complete film will form at the end of bubbling, and the nucleation of phosphate film is inhomogeneous, phosphate crystal nucleus usually forms preferentially at grain boundary. The coating weight-time curve is similar to that of the parabolic growth. The electrochemical polarization measurement shows that the corrosion potentials of the phosphated steel shifted positively about 480 mV than the bare steel and the results of neutral salt spray test (NSS) could reach 24 h, indicating the phosphating improved the corrosion resistance of the 30CrMnMoTi alloy steel.

  6. Luminescence Spectra of ZnAl 2 O 4 {:}Cr 3+ Spinel Nanopowders

    NASA Astrophysics Data System (ADS)

    Luc, H. H.; Nguyen, T. K.; Nguyen, V. M.; Suchocki, A.; Kamiñska, A.; Le, V. K.; Nguyen, V. H.; Luong, T. T.

    2002-12-01

    The synthetic ZnAl 2 O 4 spinels doped with Cr 3+ ions are prepared from ZnSO,dwi{4}>, Al 2 (SO 4 ) 3 , and Cr 2 (SO 4 ) 3 . The spinel single phase is detected from X-ray diffraction. Luminescence properties of Cr 3+ in ZnAl 2 O 4 were studied by low temperature luminescence and decay measurements. Four luminescence lines at 14570, 14520, 14460, and 14330 cm -1 were found to originate from structure distortion and the line at 14175 cm -1 - from chromium pairs. The broad emission band at about 13540 cm -1 is considered to arise from a new Cr 3+ center in ZnCr 2 O 4 .

  7. Effect of Cr and Mn ions on the structure and magnetic properties of GaFeO{sub 3}: Role of the substitution site

    SciTech Connect

    Saha, Rana; Shireen, Ajmala; Shirodkar, Sharmila N.; Waghmare, Umesh V.; Sundaresan, A.; Rao, C.N.R.

    2011-09-15

    Effect of substitution of Cr and Mn in the Fe and Ga sites of GaFeO{sub 3} on the structural parameters and magnetic properties has been investigated by preparing GaFe{sub 1-x}Cr{sub x}(Mn{sub x})O{sub 3} and Ga{sub 1-x}Cr{sub x}(Mn{sub x})FeO{sub 3} starting with appropriate oxide precursors. It is shown that, starting with Cr or Mn substituted Ga{sub 2}O{sub 3}, one obtains Ga{sub 1-x}Cr{sub x}(Mn{sub x})FeO{sub 3}, while reaction of Cr or Mn substituted {alpha}-Fe{sub 2}O{sub 3} with Ga{sub 2}O{sub 3} yields GaFe{sub 1-x}Cr{sub x}(Mn{sub x})O{sub 3}. The structural parameters and magnetic properties vary significantly with the substitution site of Cr showing a large decrease in the unit cell parameters as well as the T{sub C} and other magnetic properties when the substitution is at the octahedral Fe (1, 2) site. Substitution of Cr at the octahedral Ga2 site results in marginal changes. Substitution of Mn in the Ga and Fe sites also show differences although the changes themselves are much smaller. First-principles calculations confirm such site-specificity and show how Cr substitution affects the properties differently when substituted at the Ga2 and Fe1 sites. - Graphical abstract: The important role of site-specific substitution of transition metal ions on the structure and magnetic properties of GaFeO{sub 3} has been investigated experimentally and theoretically. Highlights: > Substitution of transition metal ions to specific cation site. > Ionic radii of the cation dictate the disorder associated with the specific site. > Site-specificity explains magnetic ordering and structural parameters.

  8. Formation Mechanisms of Alloying Element Nitrides in Recrystallized and Deformed Ferritic Fe-Cr-Al Alloy

    NASA Astrophysics Data System (ADS)

    Akhlaghi, Maryam; Meka, Sai Ramudu; Jägle, Eric A.; Kurz, Silke J. B.; Bischoff, Ewald; Mittemeijer, Eric J.

    2016-07-01

    The effect of the initial microstructure (recrystallized or cold-rolled) on the nitride precipitation process upon gaseous nitriding of ternary Fe-4.3 at. pct Cr-8.1 at. pct Al alloy was investigated at 723 K (450 °C) employing X-ray diffraction (XRD) analyses, transmission electron microscopy (TEM), atom probe tomography (APT), and electron probe microanalysis (EPMA). In recrystallized Fe-Cr-Al specimens, one type of nitride develops: ternary, cubic, NaCl-type mixed Cr1-x Al x N. In cold-rolled Fe-Cr-Al specimens, precipitation of two types of nitrides occurs: ternary, cubic, NaCl-type mixed Cr1-x Al x N and binary, cubic, NaCl-type AlN. By theoretical analysis, it was shown that for the recrystallized specimens an energy barrier for the nucleation of mixed Cr1-x Al x N exists, whereas in the cold-rolled specimens no such energy barriers for the development of mixed Cr1-x Al x N and of binary, cubic AlN occur. The additional development of the cubic AlN in the cold-rolled microstructure could be ascribed to the preferred heterogeneous nucleation of cubic AlN on dislocations. The nitrogen concentration-depth profile of the cold-rolled specimen shows a stepped nature upon prolonged nitriding as a consequence of instantaneous nucleation of nitride upon arrival of nitrogen and nitride growth rate-limited by nitrogen transport through the thickening nitrided zone.

  9. Formation Mechanisms of Alloying Element Nitrides in Recrystallized and Deformed Ferritic Fe-Cr-Al Alloy

    NASA Astrophysics Data System (ADS)

    Akhlaghi, Maryam; Meka, Sai Ramudu; Jägle, Eric A.; Kurz, Silke J. B.; Bischoff, Ewald; Mittemeijer, Eric J.

    2016-09-01

    The effect of the initial microstructure (recrystallized or cold-rolled) on the nitride precipitation process upon gaseous nitriding of ternary Fe-4.3 at. pct Cr-8.1 at. pct Al alloy was investigated at 723 K (450 °C) employing X-ray diffraction (XRD) analyses, transmission electron microscopy (TEM), atom probe tomography (APT), and electron probe microanalysis (EPMA). In recrystallized Fe-Cr-Al specimens, one type of nitride develops: ternary, cubic, NaCl-type mixed Cr1- x Al x N. In cold-rolled Fe-Cr-Al specimens, precipitation of two types of nitrides occurs: ternary, cubic, NaCl-type mixed Cr1- x Al x N and binary, cubic, NaCl-type AlN. By theoretical analysis, it was shown that for the recrystallized specimens an energy barrier for the nucleation of mixed Cr1- x Al x N exists, whereas in the cold-rolled specimens no such energy barriers for the development of mixed Cr1- x Al x N and of binary, cubic AlN occur. The additional development of the cubic AlN in the cold-rolled microstructure could be ascribed to the preferred heterogeneous nucleation of cubic AlN on dislocations. The nitrogen concentration-depth profile of the cold-rolled specimen shows a stepped nature upon prolonged nitriding as a consequence of instantaneous nucleation of nitride upon arrival of nitrogen and nitride growth rate-limited by nitrogen transport through the thickening nitrided zone.

  10. Flower-, wire-, and sheet-like MnO2-deposited diatomites: Highly efficient absorbents for the removal of Cr(VI).

    PubMed

    Du, Yucheng; Wang, Liping; Wang, Jinshu; Zheng, Guangwei; Wu, Junshu; Dai, Hongxing

    2015-03-01

    Flower-, wire-, and sheet-like MnO2-deposited diatomites have been prepared using a hydrothermal method with Mn(Ac)2, KMnO4 and/or MnSO4 as Mn source and diatomite as support. Physical properties of the materials were characterized by means of numerous analytical techniques, and their behaviors in the adsorption of chromium(VI) were evaluated. It is shown that the MnO2-deposited diatomite samples with different morphologies possessed high surface areas and abundant surface hydroxyl groups (especially the wire-like MnO2/diatomite sample). The wire-like MnO2/diatomite sample showed the best performance in the removal of Cr(VI), giving the maximum Cr(VI) adsorption capacity of 101 mg/g. PMID:25766015

  11. Coercivity enhancement in Mn-Al-Cu flakes produced by surfactant-assisted milling

    NASA Astrophysics Data System (ADS)

    Saravanan, P.; Hsu, Jen-Hwa; Vinod, V. T. P.; Černík, Miroslav; Kamat, S. V.

    2015-11-01

    We herein report the achievement of exceptionally high coercivity (Hc) values: 9.92 and 5.86 kOe at 5 and 300 K, respectively, for Mn55Al43Cu2 flakes produced by surfactant-assisted milling process without employing any heat-treatment. The use of surfactants such as oleic acid and oleylamine during milling yielded high-aspect ratio flakes for the Mn-Al-Cu alloy. Structural studies confirmed the presence of τ- and β-phases as the major constituents in the Mn-Al-Cu flakes. The observed Hc enhancement is due to the increase in anisotropy field and structural defects, which is hypothesized to originate from the domain-wall pinning as a consequence of precipitation of fine Cu-particles present at the grain boundaries.

  12. Flat panel display using Ti-Cr-Al-O thin film

    DOEpatents

    Jankowski, Alan F.; Schmid, Anthony P.

    2002-01-01

    Thin films of Ti--Cr--Al--O are used as a resistor material. The films are rf sputter deposited from ceramic targets using a reactive working gas mixture of Ar and O.sub.2. Resistivity values from 10.sup.4 to 10.sup.10 Ohm-cm have been measured for Ti--Cr--Al--O film <1 .mu.m thick. The film resistivity can be discretely selected through control of the target composition and the deposition parameters. The application of Ti--Cr--Al--O as a thin film resistor has been found to be thermodynamically stable, unlike other metal-oxide films. The Ti--Cr--Al--O film can be used as a vertical or lateral resistor, for example, as a layer beneath a field emission cathode in a flat panel display; or used to control surface emissivity, for example, as a coating on an insulating material such as vertical wall supports in flat panel displays.

  13. Process for producing Ti-Cr-Al-O thin film resistors

    DOEpatents

    Jankowski, Alan F.; Schmid, Anthony P.

    2001-01-01

    Thin films of Ti-Cr-Al-O are used as a resistor material. The films are rf sputter deposited from ceramic targets using a reactive working gas mixture of Ar and O.sub.2. Resistivity values from 10.sup.4 to 10.sup.10 Ohm-cm have been measured for Ti-Cr-Al-O film <1 .mu.m thick. The film resistivity can be discretely selected through control of the target composition and the deposition parameters. The application of Ti-Cr-Al-O as a thin film resistor has been found to be thermodynamically stable, unlike other metal-oxide films. The Ti-Cr-Al-O film can be used as a vertical or lateral resistor, for example, as a layer beneath a field emission cathode in a flat panel display; or used to control surface emissivity, for example, as a coating on an insulating material such as vertical wall supports in flat panel displays.

  14. NiAl-based Polyphase in situ Composites in the NiAl-Ta-X (X = Cr, Mo, or V) Systems

    NASA Technical Reports Server (NTRS)

    Johnson, D. R.; Oliver, B. F.; Noebe, R. D.; Whittenberger, J. D.

    1995-01-01

    Polyphase in situ composites were generated by directional solidification of ternary eutectics. This work was performed to discover if a balance of properties could be produced by combining the NiAl-Laves phase and the NiAl-refractory metal phase eutectics. The systems investigated were the Ni-Al-Ta-X (X = Cr, Mo, or V) alloys. Ternary eutectics were found in each of these systems and the eutectic composition, temperature, and morphology were determined. The ternary eutectic systems examined were the NiAl-NiAlTa-(Mo, Ta), NiAl-(Cr, Al) NiTa-Cr, and the NiAl-NiAlTa-V systems. Each eutectic consists of NiAl, a C14 Laves phase, and a refractory metal phase. Directional solidification was performed by containerless processing techniques in a levitation zone refiner to minimize alloy contamination. Room temperature fracture toughness of these materials was determined by a four-point bend test. Preliminary creep behavior was determined by compression tests at elevated temperatures, 1100-l400 K. Of the ternary eutectics, the one in the NiAl-Ta-Cr system was found to be the most promising. The fracture toughness of the NiAl-(Cr, Al)NiTa-Cr eutectic was intermediate between the values of the NiAl-NiAlTa eutectic and the NiAl-Cr eutectic. The creep strength of this ternary eutectic was similar to or greater than that of the NiAl-Cr eutectic.

  15. Effects of the substitution of Al for Mn on structure, magnetic, and magnetocaloric properties in MnCoGe

    NASA Astrophysics Data System (ADS)

    Si, Xiaodong; Liu, Yongsheng; Lu, Xiaofei; Wang, Wenli; Lei, Wei; Lin, Jia; Zhou, Tao; Xu, Yan

    2016-06-01

    The magnetic transition can be controlled by partial substitution of Al for Mn in Mn1-xAlxCoGe, leading to a wide transition temperature range around the room temperature. A well-defined linear relationship between the magnetic entropy change (|ΔSM|) and H2/3 demonstrates the second-order character of magnetic transition. In the case of x = 0.02, the relative cooling power of 242.3 J.kg-1 is achieved for Δμ0H = 5 T at 270.5 K. Interestingly, a corresponding monotonical decline in |ΔSM| is in relation to magnetic moment per formula unit. The observed large relative cooling power with wide phase transition temperatures makes these materials promising for room-temperature magnetic cooling applications.

  16. Perpendicularly magnetized {tau}-MnAl (001) thin films epitaxied on GaAs

    SciTech Connect

    Nie, S. H.; Zhu, L. J.; Lu, J.; Pan, D.; Wang, H. L.; Yu, X. Z.; Xiao, J. X.; Zhao, J. H.

    2013-04-15

    Perpendicularly magnetized {tau}-MnAl films have been epitaxied on GaAs (001) by molecular-beam epitaxy. Crystalline quality and magnetic properties of the samples were strongly dependent on growth temperature. The highest coercivity of 10.7 kOe, saturation magnetization of 361.4 emu/cm{sup 3}, perpendicular magnetic anisotropy constant of 13.65 Merg/cm{sup 3}, and magnetic energy product of 4.44 MGOe were achieved. These tunable magnetic properties make MnAl films valuable as excellent and cost-effective alternative for not only high density perpendicular magnetic recording storage and spintronics devices but also permanent magnets.

  17. Dynamical x-ray diffraction from an icosahedral Al-Pd-Mn quasicrystal

    SciTech Connect

    Kycia, S.

    1996-04-23

    Primary extinction effects in diffraction from single grains of Al-Pd- Mn, and presumably many other FCI alloys, may be significant and should be corrected for prior to use of diffraction data in structural determinations. Probes based on dynamical diffraction effects, such as x-ray standing wave fluorescence, multiple beam interference, and x-ray transmission topographs, may now be used to study the bulk and surface structure of some quasicrystals. The observation of dynamical diffraction from icosahedral Al-Pd-Mn is a striking confirmation of the fact that quasicrystals can present a degree of structural perfection comparable to that found in the best periodic intermetallic crystals.

  18. Characterization of the surface of Fe-19Mn-18Cr-C-N during heat treatment in a high vacuum - An XPS study

    SciTech Connect

    Zumsande, K.; Weddeling, A.; Hryha, E.; Huth, S.; Nyborg, L.; Weber, S.; Krasokha, N.; Theisen, W.

    2012-09-15

    Nitrogen-containing CrMn austenitic stainless steels offer evident benefits compared to CrNi-based grades. The production of high-quality parts by means of powder metallurgy could be an appropriate alternative to the standard molding process leading to improved properties. The powder metallurgical production of CrMn austenitic steel is challenging on account of the high oxygen affinity of Mn and Cr. Oxides hinder the densification processes and may lower the performance of the sintered part if they remain in the steel after sintering. Thus, in evaluating the sinterability of the steel Fe-19Mn-18Cr-C-N, characterization of the surface is of great interest. In this study, comprehensive investigations by means of X-ray photoelectron spectroscopy and scanning electron microscopy combined with energy dispersive X-ray spectroscopy were performed to characterize the surface during heat treatment in a high vacuum. The results show a shift of oxidation up to 600 Degree-Sign C, meaning transfer of oxygen from the iron oxide layer to Mn-based particulate oxides, followed by progressive reduction and transformation of the Mn oxides into stable Si-containing oxides at elevated temperatures. Mass loss caused by Mn evaporation was observed accompanied by Mn oxide decomposition starting at 700 Degree-Sign C. - Highlights: Black-Right-Pointing-Pointer Surface characterization by means of XPS, SEM, and EDX analyses. Black-Right-Pointing-Pointer Heat treatment of a high CrMn powder. Black-Right-Pointing-Pointer Transfer of oxygen from the iron oxide layer to manganese-based particulate oxides. Black-Right-Pointing-Pointer Progressive reduction of Mn oxides. Black-Right-Pointing-Pointer Transformation of the Mn oxides into stable Si-containing oxides.

  19. Sm-Nd, Rb-Sr, and Mn-Cr Ages of Yamato 74013

    NASA Technical Reports Server (NTRS)

    Nyquist, L. E.; Shih, C.- Y.; Reese, Y.D.

    2009-01-01

    Yamato 74013 is one of 29 paired diogenites having granoblastic textures. The Ar-39 - Ar-40 age of Y-74097 is approximately 1100 Ma. Rb-Sr and Sm-Nd analyses of Y-74013, -74037, -74097, and -74136 suggested that multiple young metamorphic events disturbed their isotopic systems. Masuda et al. reported that REE abundances were heterogeneous even within the same sample (Y-74010) for sample sizes less than approximately 2 g. Both they and Nyquist et al. reported data for some samples showing significant LREE enrichment. In addition to its granoblastic texture, Y-74013 is characterized by large, isolated clots of chromite up to 5 mm in diameter. Takeda et al. suggested that these diogenites originally represented a single or very small number of coarse orthopyroxene crystals that were recrystallized by shock processes. They further suggested that initial crystallization may have occurred very early within the deep crust of the HED parent body. Here we report the chronology of Y-74013 as recorded in chronometers based on long-lived Rb-87 and Sm-147, intermediate- lived Sm-146, and short-lived Mn-53.

  20. Hydrogen permeation in FeCrAl alloys for LWR cladding application

    NASA Astrophysics Data System (ADS)

    Hu, Xunxiang; Terrani, Kurt A.; Wirth, Brian D.; Snead, Lance L.

    2015-06-01

    FeCrAl, an advanced oxidation-resistant iron-based alloy class, is a highly prevalent candidate as an accident-tolerant fuel cladding material. Compared with traditional zirconium alloy fuel cladding, increased tritium permeation through FeCrAl fuel cladding to the primary coolant is expected, raising potential safety concerns. In this study, the hydrogen permeability of several FeCrAl alloys was obtained using a static permeation test station, which was calibrated and validated using 304 stainless steel. The high hydrogen permeability of FeCrAl alloys leads to concerns with respect to potentially significant tritium release when used for fuel cladding in LWRs. The total tritium inventory inside the primary coolant of a light water reactor was quantified by applying a 1-dimensional steady state tritium diffusion model to demonstrate the dependence of tritium inventory on fuel cladding type. Furthermore, potential mitigation strategies for tritium release from FeCrAl fuel cladding were discussed and indicate the potential for application of an alumina layer on the inner clad surface to serve as a tritium barrier. More effort is required to develop a robust, economical mitigation strategy for tritium permeation in reactors using FeCrAl clad fuel assemblies.

  1. Hydrogen permeation in FeCrAl alloys for LWR cladding application

    DOE PAGESBeta

    Hu, Xunxiang; Terrani, Kurt A.; Wirth, Brian D.; Snead, Lance L.

    2015-03-19

    FeCrAl is an advanced oxidation-resistant iron-based alloy class, is a highly prevalent candidate as an accident-tolerant fuel cladding material. Compared with traditional zirconium alloy fuel cladding, increased tritium permeation through FeCrAl fuel cladding to the primary coolant is expected, raising potential safety concerns. In our study, the hydrogen permeability of several FeCrAl alloys was obtained using a static permeation test station, which was calibrated and validated using 304 stainless steel. The high hydrogen permeability of FeCrAl alloys leads to concerns with respect to potentially significant tritium release when used for fuel cladding in LWRs. Also, the total tritium inventory insidemore » the primary coolant of a light water reactor was quantified by applying a 1-dimensional steady state tritium diffusion model to demonstrate the dependence of tritium inventory on fuel cladding type. Furthermore, potential mitigation strategies for tritium release from FeCrAl fuel cladding were discussed and indicate the potential for application of an alumina layer on the inner clad surface to serve as a tritium barrier. More effort is required to develop a robust, economical mitigation strategy for tritium permeation in reactors using FeCrAl clad fuel assemblies.« less

  2. Hydrogen permeation in FeCrAl alloys for LWR cladding application

    SciTech Connect

    Hu, Xunxiang; Terrani, Kurt A.; Wirth, Brian D.; Snead, Lance L.

    2015-03-19

    FeCrAl is an advanced oxidation-resistant iron-based alloy class, is a highly prevalent candidate as an accident-tolerant fuel cladding material. Compared with traditional zirconium alloy fuel cladding, increased tritium permeation through FeCrAl fuel cladding to the primary coolant is expected, raising potential safety concerns. In our study, the hydrogen permeability of several FeCrAl alloys was obtained using a static permeation test station, which was calibrated and validated using 304 stainless steel. The high hydrogen permeability of FeCrAl alloys leads to concerns with respect to potentially significant tritium release when used for fuel cladding in LWRs. Also, the total tritium inventory inside the primary coolant of a light water reactor was quantified by applying a 1-dimensional steady state tritium diffusion model to demonstrate the dependence of tritium inventory on fuel cladding type. Furthermore, potential mitigation strategies for tritium release from FeCrAl fuel cladding were discussed and indicate the potential for application of an alumina layer on the inner clad surface to serve as a tritium barrier. More effort is required to develop a robust, economical mitigation strategy for tritium permeation in reactors using FeCrAl clad fuel assemblies.

  3. Development of spin-gapless semiconductivity and half metallicity in Ti2MnAl by substitutions for Al

    NASA Astrophysics Data System (ADS)

    Lukashev, Pavel; Gilbert, Simeon; Staten, Bradley; Hurley, Noah; Fuglsby, Ryan; Kharel, Parashu; Huh, Yung; Valloppilly, Shah; Zhang, Wenyong; Yang, K.; Sellmyer, David J.

    In recent years, ever increasing interest in spin-based electronics has resulted in the search for a new class of materials that can provide a high degree of spin polarized electron transport. An ideal candidate would act like insulator for one spin channel and a conductor or semiconductor for the opposite spin channel (e.g., half metal (HM), spin-gapless semiconductor (SGS)). Here, we present the combined computational, theoretical, and experimental study of Ti2MnAl, a Heusler compound with potential application in the field of spintronics. We show that in the ground state this material is metallic, however it becomes a SGS when 50% of Al is substituted with In (e.g., Ti2MnAl0.5In0.5) , and a HM when 50% of Al is substituted with Sn (e.g., Ti2MnAl0.5Sn0.5) . Detailed study of the structural, electronic, and magnetic properties of these materials is presented. Financial support: DOE/BES (DE-FG02-04ER46152); NSF NNCI: 1542182; NRI; Academic and Scholarly Excellence Funds, Office of Academic Affairs, SDSU; UNI Faculty Summer Fellowship; Program for Outstanding Innovative Talents in Hohai University.

  4. The Effects of Helium Bubble Microstructure on Ductility in Annealed and HERF 21Cr-6Ni-9Mn Stainless Steel

    SciTech Connect

    Tosten, M.H.; Morgan, M.J.

    1998-01-01

    This study examined the effects of microstructure on the ambient temperature embrittlement from hydrogen isotopes and decay helium in 21Cr-6Ni-9Mn stainless steel. Hydrogen and tritium-exposed 21Cr-6Ni-9Mn stainless steel tensile samples were pulled to failure and then characterized by transmission electron microscopy (TEM) and optical microscopy. This study determined that ductility differences between annealed and high-energy-rate-forged (HERF) stainless steel containing tritium and its decay product, helium, could be related to differences in the helium bubble microstructures. The HERF microstructures were more resistant to tritium-induced embrittlement than annealed microstructures because the high number density of helium bubbles on dislocations trap tritium within the matrix and away from the grain boundaries.

  5. Microstructure and shape recovery characteristics in a TIG-welded Fe-Mn-Si-Cr-Ni shape memory alloy

    NASA Astrophysics Data System (ADS)

    Qiao, Zhixia; Li, Lianjin; Wang, Dongai; Li, Zongmin

    2007-07-01

    Microstructure of an Fe-Mn-Si-Cr-Ni shape memory alloy (SMA) after being TIG (tungsten-insert gas welding) welded was investigated using scanning electron microscope (SEM) and X-ray diffractometer. The results show that dendrite crystals composed of cellular sub-structures form in the weld zone due to remelting. There is no obvious change in microstructure of the heat-affected zone (HAZ) except for some degree of growth of austenite grains. Since both the weld zone and HAZ consist of single phase of austenite (γ), pre-strain can still induce the γ-->ɛ martensite transformation in welding joints of the alloy. Effect of TIG welding on shape recovery characteristics of the alloy was examined by bending tests and it was found that the TIG-welded Fe-Mn-Si-Cr-Ni alloy exhibits almost the same excellent SME as the base material.

  6. Structural and magnetic properties of a prospective spin gapless semiconductor MnCrVAl

    NASA Astrophysics Data System (ADS)

    Huh, Y.; Gilbert, S.; Kharel, P.; Jin, Y.; Lukashev, P.; Valloppilly, S.; Sellmyer, D. J.

    Recently a new class of material, spin gapless semiconductors (SGS), has attracted much attention because of their potential for spintronic devices. We have synthesized a Heusler compound, MnCrVAl, which is theoretically predicted to exhibit SGS by arc melting, rapid quenching and thermal annealing. First principles calculations are employed to describe its structural, electronic and magnetic properties. X-ray diffraction indicates that the rapidly quenched samples crystallize in the disordered cubic structure. The crystal structure is stable against heat treatment up to 650oC. The samples show very small saturation magnetization, 0.3 emu/g, at room temperature under high magnetic field, 30 kOe. Above room temperature, the magnetization increases with increasing temperature undergoing a magnetic transition at 560oC, similar to an antiferromagnetic-to-paramagnetic transition. The prospect of this material for spintronic applications will be discussed. This research is supported by SDSU Academic/Scholarly Excellence Fund, and Research/Scholarship Support Fund. Research at UNL is supported by DOE (DE-FG02-04ER46152, synthesis, characterization), NSF (ECCS-1542182, facilities), and NRI.

  7. Determination of the recovery stress under constraint in Fe29Mn7Si5Cr SMA

    NASA Astrophysics Data System (ADS)

    van Caenegem, N.; Duprez, L.; Verbeken, K.; Houbaert, Y.; Segers, D.; van Humbeeck, J.

    2008-05-01

    Ferrous shape memory alloys (SMAs) do not possess a complete shape recovery. Several attempts to improve the shape recovery still fail to achieve 100% recovery. For some applications, however, the recovery stress under constraint might be more important. In this work, a procedure was designed to measure these stresses under constraint in a Fe29MnSiCr SMA. The net recovery stress was defined as the maximal difference between the stresses developed in deformed and an undeformed sample. The calculation of σthermal(T) = E(T)α(T)(T-T0) can replace the measurement of the stress developed in the undeformed sample. The effect of partially free recovery before recovery under constraint is also investigated. It was remarkable that after annealing at 200°C, the net stress did not decrease although about 50% of the shape recovery has already taken place. This allows to use this alloy as a pipe joint, where the diameter of the joint can be larger than the one of the pipes, since the free recovery will hardly lower the recovery stresses under constraint.

  8. Microstructure and Mechanical Properties After Shock Wave Loading of Cast CrMnNi TRIP Steel

    NASA Astrophysics Data System (ADS)

    Eckner, Ralf; Krüger, L.; Ullrich, C.; Rafaja, D.; Schlothauer, T.; Heide, G.

    2016-08-01

    The mechanical response of shock wave-prestrained high-alloy Cr16-Mn7-Ni6 TRIP steel was investigated under compressive and tensile loading at room temperature. Previous shock wave loading was carried out using a flyer-plate assembly with different amounts of explosives in order to achieve shock pressures of 0.3, 0.6, 0.9, and 1.2 Mbar. A significant increase in hardness and strength was observed as compared with the initial as-cast condition. In contrast, a slight decrease in strain hardening rates was measured together with a decrease in fracture elongation in the tensile test. Microstructural analyses of the shock-loaded samples were performed by light optical and scanning electron microscopy. The microstructure revealed a high density of deformation bands consisting of separated stacking faults, ɛ-martensite, or twins. Significant amounts of deformation-induced α'-martensite were only present at the highest shock pressure of 1.2 Mbar. The thickness of the deformation bands and the number of martensite nuclei at their intersections increased with increasing shock pressure. In all shock-loaded specimens, pronounced phase transformation occurred during subsequent mechanical testing. Consequently, the amount of the deformation-induced α'-martensite in the shock-loaded specimens was higher than in the unshocked as-cast samples.

  9. Factors Affecting the Hydrogen Embrittlement Resistance of Ni-Cr-Mn-Nb Welds

    SciTech Connect

    G.A. Young; C.K. Battige; N. Liwis; M.A. Penik; J. Kikel; A.J. Silvia; C.K. McDonald

    2001-03-18

    Nickel based alloys are often welded with argon/hydrogen shielding gas mixtures to minimize oxidation and improve weld quality. However, shielding gas mixtures with {ge} 1% hydrogen additions can result in hydrogen concentrations greater than 5 wt. ppm in the weld metal and reduce ductility via hydrogen embrittlement. For the conditions investigated, the degree of hydrogen embrittlement is highly variable between 5 and 14 wt. ppm. investigation of hydrogen embrittlement of EN82H GTAW welds via tensile testing, light microscopy, transmission electron microscopy, orientation imaging microscopy, and thermal desorption spectroscopy shows that this variability is due to the inhomogeneous microstructure of the welds, the presence of recrystallized grains, and complex residual plastic strains. Specifically, research indicates that high residual strains and hydrogen trapping lower the ductility of Ni-Cr-Mn-Nb weld metal when dissolved hydrogen concentrations are greater than 5 wt. ppm. The inhomogeneous microstructure contains columnar dendritic, cellular dendritic, and recrystallized grains. The decreased tensile ductility observed in embrittled samples is recovered by post weld heat treatments that decrease the bulk hydrogen concentration below 5 wt. ppm.

  10. Identification of Precipitates in Cr-Mn-N Based Steel After Thermal Exposures

    NASA Astrophysics Data System (ADS)

    Ondruška, Michal; Dománková, Mária; Jáňa, Miroslav; Marônek, Milan

    2014-06-01

    The paper deals with the identification of precipitates in the Cr-Mn-N steels after thermal exposure. The purpose of the study is to clarify the M2N precipitation by isothermal annealing at the temperatures of 750 and 900 °C with a holding time of 5, 10, 30 min, 1 hr. and 10 hrs. Microstructure of austenitic steel was characterised by the typical presence of annealing twins. Stepwise etching was observed at the holding time of 5 and 10 minutes, but at the holding time of 30 minutes, secondary particles were precipitated at the grain boundaries. Corrosion tests revealed that holding time significantly affected steel structure. M2N is the dominant precipitate, but the occurrence of σ-phase was occasionally observed especially at the interface of discontinuous precipitation and austenitic matrix. Slight increase of hardness at the grain boundaries was caused due to the precipitation of secondary phases during isothermal holding. The maximum hardness of 294 HV was measured on the sample isothermally annealed at 750 °C and holding for 10 hrs. The research provides theoretical basis for the heat affecting of steels, such as, for example, in welding.

  11. Friction and Wear Behavior of 30CrMnSiA Steel at Elevated Temperatures

    NASA Astrophysics Data System (ADS)

    Qu, Sheng-guan; Lai, Fu-qiang; Wang, Guang-hong; Yuan, Zhi-min; Li, Xiao-qiang; Guo, Hui

    2016-04-01

    The friction and wear properties of 30CrMnSiA steel were investigated at elevated temperature from 100 to 600 °C. Thereafter, the wear debris and worn surfaces were examined to understand the wear mechanisms. The remained debris with relatively high hardness created three-body abrasion at lower temperatures (100-300 °C). Abrasive wear prevailed at the conditions with high friction coefficients and wear rates. A significant change in friction and wear behavior occurred at 400 °C. At the temperature of 400 °C, oxidation induced mild wear was found because of the formation of load-bearing oxide film. Both the friction coefficients and wear rates of the steel were lowest at 400 °C. At the temperatures of 500-600 °C, a mild-to-severe wear transition occurred which resulted in an increase in the friction coefficients and wear rates of the steel. This is related to the decrease in the strength of matrix and hardness of worn surfaces and subsurfaces. The predominant wear mechanism is considered to be severe abrasive, adhesive wear and a fatigue delamination of the oxide film.

  12. Thermomechanical properties of Cr:Tm:Ho:Y sub 3 Al sub 5 O sub 12

    SciTech Connect

    Marion, J.E.

    1990-05-15

    The thermomechanical properties of Cr:Ho:Tm:Y{sub 3}Al{sub 5}O{sub 12} have been measured and compared to similar measurements on Nd:Y{sub 3}Al{sub 5}O{sub 12}. We find that, in general, the properties are similar, with the single exception being thermal diffusivity. Nd:YAG has substantially higher thermal diffusivity than Cr:Tm:Ho:YAG. Consequently, the intrinsic thermal stress resistance figure of merit which governs a materials resistance to fracture in the presence of a steady thermal gradient is lower in Cr:Tm:Ho:YAG than in Nd:YAG. 6 refs., 1 tab.

  13. Modeling degradation and failure of Ni-Cr-Al overlay coatings

    NASA Technical Reports Server (NTRS)

    Nesbitt, J. A.; Heckel, R. W.

    1984-01-01

    Degradation of a Ni-16Cr-25Al-0.06Zr overlay coating on a Ni-22Cr substrate was examined after oxidation accompanied by thermal cycling. Concentration/distance profiles were measured in the coating and substrate after various one-hour cycles at 1150 C. A numerical model was developed to simulate coating degradation by simultaneous oxidation and coating/substrate interdiffusion. The validity of the model was confirmed by comparison of predicted and measured concentration/distance profiles. The ability of the model to identify critical system parameters was demonstrated for the case of the initial Al and Cr content of the coating and substrate.

  14. Growth, structural, and magnetic characterization of epitaxial Co2MnSi films deposited on MgO and Cr seed layers

    NASA Astrophysics Data System (ADS)

    Ortiz, G.; García-García, A.; Biziere, N.; Boust, F.; Bobo, J. F.; Snoeck, E.

    2013-01-01

    We report detailed structural characterization and magneto-optical Kerr magnetometry measurements at room temperature in epitaxial Co2MnSi thin films grown on MgO(001) and Cr(001) buffered MgO single crystals prepared by sputtering. While Co2MnSi/Cr//MgO(001) films display the expected cubic anisotropy, the magnetization curves obtained for Co2MnSi//MgO(001) samples exhibit a superimposed in-plane uniaxial magnetic anisotropy. The evolution of magnetization with film thickness points to a relevant interfacial Co2MnSi-buffer layer (Cr or MgO) contribution which competes with magnetic properties of bulk Co2MnSi, resulting in a drastic change in the magnetism of the whole sample. The origin of this interfacial magnetic anisotropy is discussed and correlated with our structural studies.

  15. Structural relaxation around substitutional Cr3+ in MgAl2O4

    NASA Astrophysics Data System (ADS)

    Juhin, Amélie; Calas, Georges; Cabaret, Delphine; Galoisy, Laurence; Hazemann, Jean-Louis

    2007-08-01

    The structural environment of a substitutional Cr3+ ion in a MgAl2O4 spinel has been investigated by Cr K -edge extended x-ray absorption fine structure and x-ray absorption near edge structure (XANES) spectroscopies. First-principles computations of the structural relaxation and of the XANES spectrum have been performed, with a good agreement with the experiment. The Cr-O distance is close to that in MgCr2O4 , indicating a full relaxation of the first neighbors, and the second shell of Al atoms relaxes partially. These observations demonstrate that Vegard’s law is not obeyed in the MgAl2O4-MgCr2O4 solid solution. Despite some angular site distortion, the local D3d symmetry of the B site of the spinel structure is retained during the substitution of Cr for Al. Here, we show that the relaxation is accommodated by strain-induced bond buckling, with angular tilts of the Mg-centered tetrahedra around the Cr-centered octahedron. By contrast, there is no significant alteration of the angles between the edge-sharing octahedra, which build chains aligned along the three fourfold axes of the cubic structure.

  16. Assessing the elastic properties and ductility of Fe-Cr-Al alloys from ab initio calculations

    NASA Astrophysics Data System (ADS)

    Nurmi, E.; Wang, G.; Kokko, K.; Vitos, L.

    2016-01-01

    Fe-Al is one of the best corrosion resistant alloys at high temperatures. The flip side of Al addition to Fe is the deterioration of the mechanical properties. This problem can be solved by adding a suitable amount of third alloying component. In the present work, we use ab initio calculations based on density functional theory to study the elastic properties of Fe?Cr?Al? alloys for Al and Cr contents up to 20 at.%. We assess the ductility as a function of chemistry by making use of the semi-empirical correlations between the elastic parameters and mechanical properties. In particular, we derive the bulk modulus to shear modulus ratio and the Cauchy pressure and monitor their trends in terms of chemical composition. The present findings are contrasted with the previously established oxidation resistance of Fe-Cr-Al alloys.

  17. A study of the impurity structure for 3d 3 (Cr 3+ and Mn 4+) ions doped into rutile TiO 2 crystal

    NASA Astrophysics Data System (ADS)

    Açıkgöz, Muhammed

    2012-02-01

    The local environment around 3d 3 (Cr 3+ and Mn 4+) ions doped into rutile TiO 2 crystals has been investigated using superposition model (SPM) analysis. The zero-field splitting (ZFS) parameters (ZFSPs) D and E are modeled for the Cr 3+ and Mn 4+ ions at both the substitutional Ti sites with local symmetry orthorhombic D2h and the interstitial sites (ISs) with the same symmetry. Several model parameter sets are adopted so as to acquire the best agreement between the calculated ZFSPs and those measured by electron magnetic resonance (EMR). The feasible values of the structural distortions (Δ RY, Δ RXZ and Δ θ) resulting from dopant Cr 3+ and Mn 4+ ions are determined. As a result, it is confirmed that Mn 4+ ions substitute for Ti 4+ sites in rutile TiO 2 crystal; however, it is suggested that Cr 3+ ions may replace at not only Ti 4+ site but also IS.

  18. Properties of molecular beam epitaxy grown Eu{sub x}(transition metal){sub y} films (transition metals: Mn, Cr)

    SciTech Connect

    Balin, K.; Nowak, A.; Gibaud, A.; Szade, J.; Celinski, Z.

    2011-04-01

    The electronic and crystallographic structures, as well as the magnetic properties, of Eu{sub x}(transition metal){sub y} (transition metals: Mn, Cr) thin films grown by molecular beam epitaxy were studied. Relative changes of the Eu/Mn and Eu/Cr ratios derived from the XPS lines, as well as x-ray reflectivity, indicate mixing of the Eu/Mn and Eu/Cr layers. Valency transitions from Eu{sup 2+} to Eu{sup 3+} were observed in both systems for most studied stoichiometries. A transition to a magnetically ordered phase was observed at 15 K, 40 K, and 62 K for selected films in the Eu-Mn system, and at 50 K for the film with a Eu/Cr ratio of 0.5.

  19. Synthesis and magnetic properties of Al doped Zn0.995Mn0.005O powers

    NASA Astrophysics Data System (ADS)

    Li, Xiang; Yu, Zhou; Long, Xue; Lin, Pengtin; Cheng, Xingwang; Liu, Ying; Cao, Chuanbao; Zhang, Hongwei; Wu, Guangheng; Yu, Richeng

    2009-06-01

    Chemical method was employed to synthesize Mn and Al codoped ZnO, namely, Zn0.995-xMn0.005AlxO with the nominal composition of x =0, 0.005, and 0.02. Structural, optical, and magnetic properties of the produced samples were studied. The results indicated that introduce Al as additional dopants induces in an enhancement of the ferromagnetism in Zn0.995Mn0.005O. The enhanced ferromagnetism (FM) in (Mn,Al) codoped sample can be understood in view of that introducing of Al could promote spinodal decomposition and lead to Mn rich regions. The Mn rich regions could be responsibility for the observed enhancement of FM at room temperature.

  20. Hardness and microstructural variation of Al-Mg-Mn-Sc-Zr alloy.

    PubMed

    Ikeshita, Sumiha; Strodahs, Ansis; Saghi, Zineb; Yamada, Kazuhiro; Burdet, Pierre; Hata, Satoshi; Ikeda, Ken-Ichi; Midgley, Paul A; Kaneko, Kenji

    2016-03-01

    Variations of Vickers hardness were observed in Al-Mg-Mn alloy and Al-Mg-Mn-Sc-Zr alloy at different ageing times, ranging from a peak value of 81.2 HV at 54 ks down to 67.4 HV at 360 ks, below the initial hardness value, 71.8 HV at 0 ks for the case of Al-Mg-Mn-Sc-Zr alloy. Microstructures of samples at each ageing stage were examined carefully by transmission electron microscopes (TEMs) both in two-dimensions and three-dimensions. The presence of different types, densities, and sizes of particles were observed dispersed spherical Al3Sc1-xZrx and also block-shaped Al3Sc precipitates growing along <100>Al with facets {100} and {110} of the precipitates. TEM analysis both in two-dimensions and three-dimensions, performed on various samples, confirmed the direct correlation between the hardness and the density of Al3Sc. PMID:26748212

  1. Corrosion Behavior of High Nitrogen Nickel-Free Fe-16Cr-Mn-Mo-N Stainless Steels

    NASA Astrophysics Data System (ADS)

    Chao, K. L.; Liao, H. Y.; Shyue, J. J.; Lian, S. S.

    2014-04-01

    The purpose of the current study is to develop austenitic nickel-free stainless steels with lower chromium content and higher manganese and nitrogen contents. In order to prevent nickel-induced skin allergy, cobalt, manganese, and nitrogen were used to substitute nickel in the designed steel. Our results demonstrated that manganese content greater than 14 wt pct results in a structure that is in full austenite phase. The manganese content appears to increase the solubility of nitrogen; however, a lower corrosion potential was found in steel with high manganese content. Molybdenum appears to be able to increase the pitting potential. The effects of Cr, Mn, Mo, and N on corrosion behavior of Fe-16Cr-2Co-Mn-Mo-N high nitrogen stainless steels were evaluated with potentiodynamic tests and XPS surface analysis. The results reveal that anodic current and pits formation of the Fe-16Cr-2Co-Mn-Mo-N high nitrogen stainless steels were smaller than those of lower manganese and nitrogen content stainless steel.

  2. In situ neutron-diffraction study of the Ti38V30Cr14Mn18 structure during hydrogenation

    NASA Astrophysics Data System (ADS)

    Fei, Yang; Kong, Xiangcheng; Wu, Zhu; Li, Huanhuan; Peterson, V. K.

    2013-11-01

    The phase transformations of the Ti38V30Cr14Mn18 alloy during hydrogenation and dehydrogenation using deuterium (D2) were investigated using in situ neutron powder diffraction (NPD) at various D2 pressures up to 2 MPa. Initially, the first hydride that formed, Ti38V30Cr14Mn18D15, had the same body centered cubic (BCC) crystal structure as the starting alloy. Upon further hydrogenation, the system displays a distinct two-phase mixture of the intermediate BCC and body-centered tetragonal (BCT) phases, that exist in a ration of 1.38:1.42, respectively. At the end of the deuterium absorption, the phase pure Ti38V30Cr14Mn18D183 material forms, with a face-centered cubic (FCC) structure. Upon dehydrogenation, all hydride phases eventually returned to the initial alloy phase without any amorphization or disproportionation. Using standard Rietveld refinement, information on the variation of the deuterium site occupancy, the lattice symmetry, and the cell volume were determined during these phase changes and are presented.

  3. Electrokinetic recovery of Cd, Cr, As, Ni, Zn and Mn from waste printed circuit boards: effect of assisting agents.

    PubMed

    Xiu, Fu-Rong; Zhang, Fu-Shen

    2009-10-15

    The printed circuit boards (PCBs) contains large number of heavy metal such as Cd, Cr, As, Ni, Zn and Mn. In this study, the use of electrokinetic (EK) treatment with different assisting agents has been investigated to recover the heavy metals from waste PCBs, and the effectiveness of different assisting agents (HNO(3), HCl, citric acid) was evaluated. The PCBs were first pre-treated by supercritical water oxidation (SCWO) process, then subjected to EK process. The heavy metal speciation, migration and recovery efficiency in the presence of different assisting agents during EK process were discussed. The mass loss of Cd, Cr, As and Zn during the SCWO process was negligible, but approximately 52% of Ni and 56% of Mn were lost in such a process. Experimental results showed that different assisting agents have significant effect on the behavior and recovery efficiency of different heavy metals. HCl was highly efficient for the recovery of Cd in waste PCBs due to the low pH and the stable complexation of Cl(-). Citric acid was highly efficient for the recovery of Cr, Zn and Mn. HNO(3) was low efficient for recovery of most heavy metals except for Ni. PMID:19481346

  4. Cyclic Oxidation Behavior of CuCrAl Cold-Sprayed Coatings for Reusable Launch Vehicles

    NASA Technical Reports Server (NTRS)

    Raj, Sai; Karthikeyan, J.

    2009-01-01

    The next generation of reusable launch vehicles is likely to use GRCop-84 [Cu-8(at.%)Cr-4%Nb] copper alloy combustion liners. The application of protective coatings on GRCop-84 liners can minimize or eliminate many of the environmental problems experienced by uncoated liners and significantly extend their operational lives and lower operational cost. A newly developed Cu- 23 (wt.%) Cr-5% Al (CuCrAl) coating, shown to resist hydrogen attack and oxidation in an as-cast form, is currently being considered as a protective coating for GRCop-84. The coating was deposited on GRCop-84 substrates by the cold spray deposition technique, where the CuCrAl was procured as gas-atomized powders. Cyclic oxidation tests were conducted between 773 and 1,073 K to characterize the coated substrates.

  5. High-pressure synthesis of L10 MnAl with near-stoichiometric composition.

    PubMed

    Kinemuchi, Y; Fujita, A; Ozaki, K

    2016-07-01

    L10 MnAl, which is a nonequilibrium ferromagnetic phase, is fabricated successfully with various compositions via high-pressure synthesis. The L10 phase is observed at pressures higher than 5 GPa, indicating that the volume effect is crucial for the stabilization of this phase. The employed synthesis route does not require a Mn-rich ε-phase, which has conventionally been used as the precursor compound. This allows for the synthesis of the L10 phase with a near-stoichiometric composition. In addition to variations in the composition in terms of the Mn/Al ratio, the axial ratio (c/a) as well as the ordering parameter (S) are modified systematically, with the maximum c/a and S values corresponding to the stoichiometric composition. With this structural change, the highest coercive force is also observed at the stoichiometric composition. PMID:27302146

  6. First-principles study of spin-transfer torque in Co2MnSi/Al/Co2MnSi spin-valve

    NASA Astrophysics Data System (ADS)

    Tang, Ling; Yang, Zejin

    2013-11-01

    The spin-transfer torque (STT) in Co2MnSi(CMS)/Al/Co2MnSi spin-valve system with and without interfacial disorder is studied by a first-principles noncollinear wave-function-matching method. It is shown that in the case of clean interface the angular dependence of STT for CoCo/Al (the asymmetry parameter Λ ≈4.5) is more skewed than that for MnSi/Al (Λ≈2.9), which suggests the clean CoCo/Al architecture is much more efficient for the application on radio frequency oscillation. We also find that even with interfacial disorder the spin-valve of half-metallic CMS still has a relatively large parameter Λ compared to that of conventional ferromagnet. In addition, for clean interface the in-plane torkance of MnSi/Al is about twice as large as that of CoCo/Al. However, as long as the degree of interfacial disorder is sufficiently large, the CoCo/Al and MnSi/Al will show approximately the same magnitude of in-plane torkance. Furthermore, our results demonstrate that CMS/Al/CMS system has very high efficiency of STT to switch the magnetic layer of spin-valve.

  7. First-principles study of spin-transfer torque in Co{sub 2}MnSi/Al/Co{sub 2}MnSi spin-valve

    SciTech Connect

    Tang, Ling Yang, Zejin

    2013-11-21

    The spin-transfer torque (STT) in Co{sub 2}MnSi(CMS)/Al/Co{sub 2}MnSi spin-valve system with and without interfacial disorder is studied by a first-principles noncollinear wave-function-matching method. It is shown that in the case of clean interface the angular dependence of STT for CoCo/Al (the asymmetry parameter Λ≈4.5) is more skewed than that for MnSi/Al (Λ≈2.9), which suggests the clean CoCo/Al architecture is much more efficient for the application on radio frequency oscillation. We also find that even with interfacial disorder the spin-valve of half-metallic CMS still has a relatively large parameter Λ compared to that of conventional ferromagnet. In addition, for clean interface the in-plane torkance of MnSi/Al is about twice as large as that of CoCo/Al. However, as long as the degree of interfacial disorder is sufficiently large, the CoCo/Al and MnSi/Al will show approximately the same magnitude of in-plane torkance. Furthermore, our results demonstrate that CMS/Al/CMS system has very high efficiency of STT to switch the magnetic layer of spin-valve.

  8. Discharge properties of Mg-Al-Mn-Ca and Mg-Al-Mn alloys as anode materials for primary magnesium-air batteries

    NASA Astrophysics Data System (ADS)

    Yuasa, Motohiro; Huang, Xinsheng; Suzuki, Kazutaka; Mabuchi, Mamoru; Chino, Yasumasa

    2015-11-01

    The discharge behaviors of rolled Mg-6 mass%Al-0.3 mass%Mn-2 mass%Ca (AMX602) and Mg-6 mass%Al-0.3 mass%Mn (AM60) alloys used as anodes for Magnesium-air batteries were investigated. The AMX602 alloy exhibited superior discharge properties compared to the AM60 alloy, especially at low current density. The discharge products of the AMX602 alloy were dense and thin, and many cracks were observed at all current densities. In addition, the discharge products were detached at some sites. These sites often corresponded to the positions of Al2Ca particles. The comparison of the discharge and corrosion tests indicated that the dense and thin discharge products of AMX602 were easily cracked by dissolution of the Mg matrix around Al2Ca particles, and the cracks promoted the penetration of the electrolyte into the discharge products, retaining the discharge activity. In contrast, concerning the AM60 alloy, thick discharge products were formed on the surface during discharge, and cracking of the discharge products hardly occurred, degrading the discharge properties. Localized and deeply corroded pits that could result from the detachment of metal pieces from the anode during discharge were partly observed in the AM60 alloy. It is suggested that these detached metal pieces are another reason for the low discharge properties of the AM60 alloy.

  9. Simulation of the aluminothermic smelting of Mo-Ti-Al and Mo-Ti-V-Cr-Al alloys

    NASA Astrophysics Data System (ADS)

    Udoeva, L. Yu.; Chumarev, V. M.; Larionov, A. V.; Rylov, A. N.; Trubachev, M. V.

    2013-08-01

    Thermodynamic simulation is performed to estimate the parameters and indicators of the aluminothermic melting of Mo-Ti-Al and Mo-Ti-V-Cr-Al master alloys intended for the alloying of titanium. The simulation is carried out with the HSC 6.1 Chemistry software package and is based on approximate calculations of the thermodynamic properties of Mo, Cr, and V aluminides, which are unavailable in handbooks. A comparison of the calculated and experimental data on the compositions of the forming alloys demonstrates that the developed models are adequate to technological processes and can be applied to optimize the parameters and to predict the compositions of smelting products.

  10. Al-Mn coating electrodeposited from ionic liquid on NdFeB magnet with high hardness and corrosion resistance

    NASA Astrophysics Data System (ADS)

    Ding, Jingjing; Xu, Bajin; Ling, Guoping

    2014-06-01

    Al-Mn coatings were electrodeposited on sintered NdFeB permanent magnet in MnCl2-AlCl3-1-ethyl-3-methylim-idazolium chloride (MnCl2-AlCl3-EMIC) ionic liquid at room temperature. The coatings were characterized by scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The adhesion strength of the coating on NdFeB substrate was evaluated by thermal shock and scratch test. The hardness and corrosion behavior of Al-Mn coating were measured by a Knoop microhardness tester, immersion test and neutral salt spray test respectively. The results showed that the amorphous structure of the deposits was obtained at the current density of 6 mA/cm2, while higher current densities resulted in a mixed structure of amorphous and crystalline. The Al-Mn coating showed excellent adhesion strength on NdFeB substrate with the thermal shock test over 30 cycles and Lc > 80 N. The hardness of Al-Mn coating was up to 5.4 GPa. The amorphous Al-Mn coating showed an anodic sacrificial protection with a low corrosion rate for NdFeB. Meanwhile, the magnetic properties measured by an AMT-4 magnetic measurement device showed that Al-Mn coating did not deteriorate the magnetic property of NdFeB.

  11. The microstructure of near-equiatomic B2/f.c.c. FeNiMnAl alloys

    SciTech Connect

    Baker, I.; Wu, H.; Wu, X.; Miller, M.K.; Munroe, P.R.

    2011-10-15

    A microstructural analysis of two FeNiMnAl alloys, Fe{sub 30}Ni{sub 20}Mn{sub 30}Al{sub 20} and Fe{sub 25}Ni{sub 25}Mn{sub 30}Al{sub 20}, was performed by a combination of atom probe tomography and transmission electron microscopy techniques. Although the microstructures of both alloys, which consist of alternating platelets aligned along < 100> of the B2-ordered phase, are similar to B2/b.c.c. two-phase alloys previously observed in the FeNiMnAl system, the two phases present in the current alloys are B2-ordered and f.c.c., with the latter phase being heavily twinned. Very fine ({approx} 5 nm) precipitates, whose chemistry was similar to that of the f.c.c. (Fe, Mn)-rich phase, were found within the B2 (Ni, Al)-rich phase in both alloys. - Highlights: {yields} The microstructures of the novel alloys Fe{sub 30}Ni{sub 20}Mn{sub 30}Al{sub 20} and Fe{sub 25}Ni{sub 25}Mn{sub 30}Al{sub 20} were characterized. {yields} Atom probe tomography and transmission electron microscopy were used in the study. {yields} A < 100>-aligned B2-ordered phase and heavily-twinned f.c.c. phase were present. {yields} Very fine (Fe, Mn)-rich precipitates were found within the B2 (Ni, Al)-rich phase.

  12. Anomalous magnetic configuration of Mn{sub 2}NiAl ribbon and the role of hybridization in the martensitic transformation of Mn{sub 50}Ni{sub 50−x}Al{sub x} ribbons

    SciTech Connect

    Zhao, R. B.; Zhao, D. W.; Li, G. K.; Ma, L. E-mail: houdenglu@mail.hebtu.edu.cn; Zhen, C. M.; Hou, D. L. E-mail: houdenglu@mail.hebtu.edu.cn; Wang, W. H.; Liu, E. K.; Chen, J. L.; Wu, G. H.

    2014-12-08

    The magnetic configuration of Mn{sub 2}NiAl ribbon has been investigated. In contrast to Ni{sub 2}MnAl, the compound Mn{sub 2}NiAl with considerable disorder does exhibit ferromagnetism and, due to exchange interaction competition, both ferromagnetic and antiferromagnetic moment orientations can coexist between nearest neighbor Mn atoms. This is unexpected in Heusler alloys. Regarding the mechanism of the martensitic transformation in Mn{sub 50}Ni{sub 50−x}Al{sub x}, it is found that increasing the Al content results in an unusual change in the lattice constant, a decrease of the transformation entropy change, and enhancement of the calculated electron localization. These results indicate that the p-d covalent hybridization between Mn (or Ni) and Al atoms gradually increases at the expense of the d-d hybridization between Ni and Mn atoms. This leads to an increased stability of the austenite phase and a decrease of the martensitic transformation temperature. For 11 ≤ x ≤ 14, Mn{sub 50}Ni{sub 50−x}Al{sub x} ferromagnetic shape memory alloys are obtained.

  13. Three-dimensionally Ordered Macroporous Structure Enabled Nanothermite Membrane of Mn2O3/Al.

    PubMed

    Zheng, Guoqiang; Zhang, Wenchao; Shen, Ruiqi; Ye, Jiahai; Qin, Zhichun; Chao, Yimin

    2016-01-01

    Mn2O3 has been selected to realize nanothermite membrane for the first time in the literature. Mn2O3/Al nanothermite has been synthesized by magnetron sputtering a layer of Al film onto three-dimensionally ordered macroporous (3DOM) Mn2O3 skeleton. The energy release is significantly enhanced owing to the unusual 3DOM structure, which ensures Al and Mn2O3 to integrate compactly in nanoscale and greatly increase effective contact area. The morphology and DSC curve of the nanothermite membrane have been investigated at various aluminizing times. At the optimized aluminizing time of 30 min, energy release reaches a maximum of 2.09 kJ∙g(-1), where the Al layer thickness plays a decisive role in the total energy release. This method possesses advantages of high compatibility with MEMS and can be applied to other nanothermite systems easily, which will make great contribution to little-known nanothermite research. PMID:26935405

  14. Three-dimensionally Ordered Macroporous Structure Enabled Nanothermite Membrane of Mn2O3/Al

    NASA Astrophysics Data System (ADS)

    Zheng, Guoqiang; Zhang, Wenchao; Shen, Ruiqi; Ye, Jiahai; Qin, Zhichun; Chao, Yimin

    2016-03-01

    Mn2O3 has been selected to realize nanothermite membrane for the first time in the literature. Mn2O3/Al nanothermite has been synthesized by magnetron sputtering a layer of Al film onto three-dimensionally ordered macroporous (3DOM) Mn2O3 skeleton. The energy release is significantly enhanced owing to the unusual 3DOM structure, which ensures Al and Mn2O3 to integrate compactly in nanoscale and greatly increase effective contact area. The morphology and DSC curve of the nanothermite membrane have been investigated at various aluminizing times. At the optimized aluminizing time of 30 min, energy release reaches a maximum of 2.09 kJ•g-1, where the Al layer thickness plays a decisive role in the total energy release. This method possesses advantages of high compatibility with MEMS and can be applied to other nanothermite systems easily, which will make great contribution to little-known nanothermite research.

  15. [Cathodoluminescent characteristics of green-emitting ZnAl2O4:Mn thin film phosphors].

    PubMed

    Lou, Zhi-dong; Xu, Zheng; Yi, Lan-jie; Yang, Sheng-yi

    2008-06-01

    Green electroluminescence was obtained from thin films of ZnAl2O4: Mn prepared by rf magnetron sputtering onto thick insulating ceramic sheets. Photoluminescence and stress-stimulated luminescence was obtained for Mn-doped ZnAl2O4 powder synthesized by the solid phase reaction. Since it is extremely stable chemically and thermally, ZnAl2O4 may emerge as an alternative choice to sulphide-based phosphors. In the present paper, thin films of ZnAl2O4: Mn were grown on aluminosilicate ceramic plates using spray pyrolysis of aqueous solutions. The cathodoluminescence (CL) properties of the films under low to medium excitation voltage (<5 kV) were investigated. The films exhibited green CL after being annealed at temperatures above 550 degrees C, which corresponds to the transition between 4 T1 and (6)A1 of Mn2+ ions located in the tetra coordination of the Zn2+ site in the spinel structure. The chromaticity coordinates were x = 0.150 and y = 0.734 with a dominant wavelength of 525 nm and an 82% color purity. The CL luminance and efficiency depended on the excitation voltage and current density. Saturation effects were observed as the current density increased. A luminance of 540 cd x m(-2) and an efficiency of 4.5 lm x W(-1) were obtained at an excitation voltage of 4 kV with a current density of 38 microA x cm(-2). PMID:18800691

  16. Synthesis, characterization, photoluminescence and EPR investigations of Mn doped MgAl 2O 4 phosphors

    NASA Astrophysics Data System (ADS)

    Singh, Vijay; Chakradhar, R. P. S.; Rao, J. L.; Kim, Dong-Kuk

    2007-07-01

    MgAl 2O 4:Mn phosphors have been prepared at 500 °C by combustion route. Powder X-ray diffraction (XRD) indicated the presence of mono-MgAl 2O 4 phase. Scanning electron microscopy showed that the powder particle crystallites are mostly angular. Fourier transform infrared spectroscopy confirmed the presence of AlO 6 group which makes up the MgAl 2O 4 spinel. Photoluminescence studies showed green/red emission indicating that two independent luminescence channels in this phosphor. The green emission at 518 nm is due to 4T1 → 6A1 transition of Mn 2+ ions. The emission at 650 nm is due to the charge-transfer deexcitation associated with the Mn ion. EPR spectrum exhibits allowed and forbidden hyperfine structure at g=2.003. The g≈2.00 is due to Mn 2+ ion in an environment close to tetrahedral symmetry. It is observed that N and χ increase with decrease of temperature obeying the Boltzmann law. The variation of zero-field splitting parameter ( D) with temperature is evaluated and discussed.

  17. Three-dimensionally Ordered Macroporous Structure Enabled Nanothermite Membrane of Mn2O3/Al

    PubMed Central

    Zheng, Guoqiang; Zhang, Wenchao; Shen, Ruiqi; Ye, Jiahai; Qin, Zhichun; Chao, Yimin

    2016-01-01

    Mn2O3 has been selected to realize nanothermite membrane for the first time in the literature. Mn2O3/Al nanothermite has been synthesized by magnetron sputtering a layer of Al film onto three-dimensionally ordered macroporous (3DOM) Mn2O3 skeleton. The energy release is significantly enhanced owing to the unusual 3DOM structure, which ensures Al and Mn2O3 to integrate compactly in nanoscale and greatly increase effective contact area. The morphology and DSC curve of the nanothermite membrane have been investigated at various aluminizing times. At the optimized aluminizing time of 30 min, energy release reaches a maximum of 2.09 kJ∙g−1, where the Al layer thickness plays a decisive role in the total energy release. This method possesses advantages of high compatibility with MEMS and can be applied to other nanothermite systems easily, which will make great contribution to little-known nanothermite research. PMID:26935405

  18. Thermal stability and thermo-mechanical properties of magnetron sputtered Cr-Al-Y-N coatings

    SciTech Connect

    Rovere, Florian; Mayrhofer, Paul H.

    2008-01-15

    Cr{sub 1-x}Al{sub x}N coatings are promising candidates for advanced machining and high temperature applications due to their good mechanical and thermal properties. Recently the authors have shown that reactive magnetron sputtering using Cr-Al targets with Al/Cr ratios of 1.5 and Y contents of 0, 2, 4, and 8 at % results in the formation of stoichiometric (Cr{sub 1-x}Al{sub x}){sub 1-y}Y{sub y}N films with Al/Cr ratios of {approx}1.2 and YN mole fractions of 0%, 2%, 4%, and 8%, respectively. Here, the impact of Y on thermal stability, structural evolution, and thermo-mechanical properties is investigated in detail. Based on in situ stress measurements, thermal analyzing, x-ray diffraction, and transmission electron microscopy studies the authors conclude that Y effectively retards diffusional processes such as recovery, precipitation of hcp-AlN and fcc-YN, grain growth, and decomposition induced N{sub 2} release. Hence, the onset temperature of the latter shifts from {approx}1010 to 1125 deg. C and the hardness after annealing at T{sub a}=1100 deg. C increases from {approx}32 to 39 GPa with increasing YN mole fraction from 0% to 8%, respectively.

  19. Preliminary Study on Fatigue Strengths of Fretted Ti-48Al-2Cr-2Nb

    NASA Technical Reports Server (NTRS)

    Miyoshi, Kazuhisa; Lerch, Bradley A.; Draper, Susan L.

    2002-01-01

    The fatigue behavior (stress-life curve) of gamma titanium aluminide (Ti-48Al-2Cr-2Nb, atomic percent) was examined by conducting two tests: first, a fretting wear test with a fatigue specimen in contact with a typical nickel-based superalloy contact pad in air at temperatures of 296 and 823 K and second, a high-cycle fatigue test of the prefretted Ti-48Al-2Cr-2Nb fatigue specimen at 923 K. Reference high-cycle fatigue tests were also conducted with unfretted Ti-48Al-2Cr-2Nb specimens at 923 K. All Ti-48Al-2Cr-2Nb fatigue specimens were machined from cast slabs. The results indicate that the stress-life results for the fretted Ti-48Al-2Cr-2Nb specimens exhibited a behavior similar to those of the unfretted Ti-48Al-2Cr-2Nb specimens. The values of maximum stress and life for the fretted specimens were almost the same as those for the unfretted specimens. The resultant stress-life curve for the unfretted fatigue specimens was very flat. The flat appearance in the stress-life curve of the unfretted specimens is attributed to the presence of a high density of casting pores. The fatigue strengths of both the fretted and unfretted specimens can be significantly affected by the presence of this porosity, which can decrease the fatigue life of Ti-48Al-2Cr-2Nb. The presence of the porosity made discerning the effect of fretting damage on fatigue strength and life of the specimens difficult.

  20. Cr4 + :Gd3Sc2Ga3O12 passive Q-switch for the Cr3 + :LiCaAlF6 laser

    NASA Astrophysics Data System (ADS)

    Kuo, Yen-Kuang; Yang, Yang; Birnbaum, Milton

    1994-05-01

    A Cr4+:Gd3Sc2Ga3O12 (Cr4+:GSGG) broad-band saturable absorber has been demonstrated to be an excellent passive Q-switch for the flashlamp-pumped tunable Cr3+:LiCaAlF6 (Cr:LiCAF) laser at room temperature. A single Q-switched laser output pulse of 11 mJ in energy and 37 ns in duration at 778 nm was obtained in a nonoptimized laser.

  1. The Microstructure of Near-Equiatomic B2/f.c.c. FeNiMnAl Alloys

    SciTech Connect

    Baker, Ian; Wu, H; Wu, Xiaolan; Miller, Michael K; Munroe, P R

    2011-01-01

    A microstructural analysis of two FeNiMnAl alloys, Fe{sub 30}Ni{sub 20}Mn{sub 30}Al{sub 20} and Fe{sub 25}Ni{sub 25}Mn{sub 30}Al{sub 20}, was performed by a combination of atom probe tomography and transmission electron microscopy techniques. Although the microstructures of both alloys, which consist of alternating platelets aligned along <100> of the B2-ordered phase, are similar to B2/b.c.c. two-phase alloys previously observed in the FeNiMnAl system, the two phases present in the current alloys are B2-ordered and f.c.c., with the latter phase being heavily twinned. Very fine ({approx} 5 nm) precipitates, whose chemistry was similar to that of the f.c.c. (Fe, Mn)-rich phase, were found within the B2 (Ni, Al)-rich phase in both alloys.

  2. Observation of Precipitation Evolution in Fe-Ni-Mn-Ti-Al Maraging Steel by Atom Probe Tomography

    NASA Astrophysics Data System (ADS)

    Pereloma, E. V.; Stohr, R. A.; Miller, M. K.; Ringer, S. P.

    2009-12-01

    We describe the full decomposition sequence in an Fe-Ni-Mn-Ti-Al maraging steel during isothermal annealing at 550 °C. Following significant pre-precipitation clustering reactions within the supersaturated martensitic solid solution, (Ni,Fe)3Ti and (Ni,Fe)3(Al,Mn) precipitates eventually form after isothermal aging for ~60 seconds. The morphology of the (Ni,Fe)3Ti particles changes gradually during aging from predominantly plate-like to rod-like, and, importantly, Mn and Al were observed to segregate to these precipitate/matrix interfaces. The (Ni,Fe)3(Al,Mn) precipitates occurred at two main locations: uniformly within the matrix and at the periphery of the (Ni,Fe)3Ti particles. We relate this latter mode of precipitation to the Mn-Al segregation.

  3. Observation of Precipitation Evolution in Fe-Ni-Mn-Ti-Al Maraging Steel using Atom Probe Tomography

    SciTech Connect

    Pereloma, E. V.; Stohr, R A; Miller, Michael K; Ringer, S. P.

    2009-01-01

    We describe the full decomposition sequence in an Fe-Ni-Mn-Ti-Al maraging steel during isothermal annealing at 550 C. Following significant pre-precipitation clustering reactions within the supersaturated martensitic solid solution, (Ni,Fe){sub 3}Ti and (Ni,Fe){sub 3}(Al,Mn) precipitates eventually form after isothermal aging for {approx}60 seconds. The morphology of the (Ni,Fe){sub 3}Ti particles changes gradually during aging from predominantly plate-like to rod-like, and, importantly, Mn and Al were observed to segregate to these precipitate/matrix interfaces. The (Ni,Fe){sub 3}(Al,Mn) precipitates occurred at two main locations: uniformly within the matrix and at the periphery of the (Ni,Fe){sub 3}Ti particles. We relate this latter mode of precipitation to the Mn-Al segregation.

  4. Characterization of a CuAlBe Alloy with Different Cr Contents

    NASA Astrophysics Data System (ADS)

    da M. Candido, Gemierson Valois; de A. Melo, Tadeu Antônio; De Albuquerque, Victor Hugo C.; Gomes, Rodinei Medeiros; de Lima, Severino Jackson G.; Tavares, João Manuel R. S.

    2012-11-01

    In this article, the use of chromium (Cr) as a grain refiner for a CuAlBe shape memory alloy is discussed. Alloys with 0.1, 0.2, 0.3, and 0.5 wt.% Cr were characterized by optical microscopy, scanning electron microscope, and x-ray diffraction. Also, the influence of the different percentages of Cr on the grain size and on the mechanical properties was analyzed through macro- and microscopic evaluations and by tensile and hardness tests, respectively. Finally, the phase transformation temperatures of the alloys were determined by thermal analysis using differential scanning calorimetry. The results showed that the higher the Cr content, the greater the grain refinement effect and lower the hardness. In addition, at room temperature the alloys with 0.1 and 0.2 wt.% Cr were austenitic, while the rest were martensitic. The tensile tests showed that the alloy with 0.2 wt.% Cr provided the best strain-stress performance. The conclusion was that the use of 0.2 wt.% Cr as a grain refiner improved the mechanical properties of the CuAlBe alloy; however, the same was not observed for the other Cr contents.

  5. Oxidation Resistant Ti-Al-Fe Diffusion Barrier for FeCrAlY Coatings on Titanium Aluminides

    NASA Technical Reports Server (NTRS)

    Brady, Michael P. (Inventor); Smialke, James L. (Inventor); Brindley, William J. (Inventor)

    1996-01-01

    A diffusion barrier to help protect titanium aluminide alloys, including the coated alloys of the TiAl gamma + Ti3Al (alpha2) class, from oxidative attack and interstitial embrittlement at temperatures up to at least 1000 C is disclosed. The coating may comprise FeCrAlX alloys. The diffusion barrier comprises titanium, aluminum, and iron in the following approximate atomic percent: Ti-(50-55)Al-(9-20)Fe. This alloy is also suitable as an oxidative or structural coating for such substrates.

  6. Lattice dynamics in austenitic stainless steels Fe 18Cr 12Ni 2Mo and Fe 18Cr 16Ni 10Mn

    NASA Astrophysics Data System (ADS)

    Rajevac, V.; Hoelzel, M.; Danilkin, S. A.; Hoser, A.; Fuess, H.

    2004-04-01

    Phonon dispersion curves of austenitic stainless steels Fe-18Cr-16Ni-10Mn and Fe-18Cr-12Ni-2Mo have been measured by triple-axis neutron spectroscopy. The data were analysed using Born-von Karman interactions as well as calculations including the contribution of conduction electrons on the lattice dynamics. An appropriate description of the experimental data was obtained by taking into account two-neighbour shells plus the contribution of the electron gas. The elastic constants and moduli obtained are close to reported results by ultrasonic studies on polycrystalline samples. The phonon densities of states in both systems calculated from the dispersion curves agree well with results obtained by time-of-flight neutron spectroscopy on polycrystalline samples. The Debye temperature THgr(T) shows a minimum around 40 K, similar to copper and nickel.

  7. Radiation tolerance of neutron-irradiated model Fe-Cr-Al alloys

    NASA Astrophysics Data System (ADS)

    Field, Kevin G.; Hu, Xunxiang; Littrell, Kenneth C.; Yamamoto, Yukinori; Snead, Lance L.

    2015-10-01

    The Fe-Cr-Al alloy system has the potential to form an important class of enhanced accident-tolerant cladding materials in the nuclear power industry owing to the alloy system's higher oxidation resistance in high-temperature steam environments compared with traditional zirconium-based alloys. However, radiation tolerance of Fe-Cr-Al alloys has not been fully established. In this study, a series of Fe-Cr-Al alloys with 10-18 wt % Cr and 2.9-4.9 wt % Al were neutron irradiated at 382 °C to 1.8 dpa to investigate the irradiation-induced microstructural and mechanical property evolution as a function of alloy composition. Dislocation loops with Burgers vector of a/2<111> and a<100> were detected and quantified. Results indicate precipitation of Cr-rich α‧ is primarily dependent on the bulk chromium composition. Mechanical testing of sub-size-irradiated tensile specimens indicates the hardening response seen after irradiation is dependent on the bulk chromium composition. A structure-property relationship was developed; it indicated that the change in yield strength after irradiation is caused by the formation of these radiation-induced defects and is dominated by the large number density of Cr-rich α‧ precipitates at sufficiently high chromium contents after irradiation.

  8. Radiation tolerance of neutron-irradiated model Fe-Cr-Al alloys

    DOE PAGESBeta

    Field, Kevin G.; Hu, Xunxiang; Littrell, Kenneth C.; Yamamoto, Yukinori; Snead, Lance Lewis

    2015-07-14

    The Fe Cr Al alloy system has the potential to form an important class of enhanced accident-tolerant cladding materials in the nuclear power industry owing to the alloy system's higher oxidation resistance in high-temperature steam environments compared with traditional zirconium-based alloys. However, radiation tolerance of Fe Cr Al alloys has not been fully established. In this study, a series of Fe Cr Al alloys with 10 18 wt % Cr and 2.9 4.9 wt % Al were neutron irradiated at 382 C to 1.8 dpa to investigate the irradiation-induced microstructural and mechanical property evolution as a function of alloy composition.more » Dislocation loops with Burgers vector of a/2 111 and a 100 were detected and quantified. Results indicate precipitation of Cr-rich is primarily dependent on the bulk chromium composition. Mechanical testing of sub-size-irradiated tensile specimens indicates the hardening response seen after irradiation is dependent on the bulk chromium composition. Furthermore, a structure property relationship was developed; it indicated that the change in yield strength after irradiation is caused by the formation of these radiation-induced defects and is dominated by the large number density of Cr-rich α' precipitates at sufficiently high chromium contents after irradiation.« less

  9. Radiation tolerance of neutron-irradiated model Fe-Cr-Al alloys

    NASA Astrophysics Data System (ADS)

    Field, Kevin G.; Hu, Xunxiang; Littrell, Kenneth C.; Yamamoto, Yukinori; Snead, Lance L.

    2015-10-01

    The Fe-Cr-Al alloy system has the potential to form an important class of enhanced accident-tolerant cladding materials in the nuclear power industry owing to the alloy system's higher oxidation resistance in high-temperature steam environments compared with traditional zirconium-based alloys. However, radiation tolerance of Fe-Cr-Al alloys has not been fully established. In this study, a series of Fe-Cr-Al alloys with 10-18 wt % Cr and 2.9-4.9 wt % Al were neutron irradiated at 382 °C to 1.8 dpa to investigate the irradiation-induced microstructural and mechanical property evolution as a function of alloy composition. Dislocation loops with Burgers vector of a/2<111> and a<100> were detected and quantified. Results indicate precipitation of Cr-rich α‧ is primarily dependent on the bulk chromium composition. Mechanical testing of sub-size-irradiated tensile specimens indicates the hardening response seen after irradiation is dependent on the bulk chromium composition. A structure-property relationship was developed; it indicated that the change in yield strength after irradiation is caused by the formation of these radiation-induced defects and is dominated by the large number density of Cr-rich α‧ precipitates at sufficiently high chromium contents after irradiation.

  10. Radiation tolerance of neutron-irradiated model Fe-Cr-Al alloys

    SciTech Connect

    Field, Kevin G.; Hu, Xunxiang; Littrell, Kenneth C.; Yamamoto, Yukinori; Snead, Lance Lewis

    2015-07-14

    The Fe Cr Al alloy system has the potential to form an important class of enhanced accident-tolerant cladding materials in the nuclear power industry owing to the alloy system's higher oxidation resistance in high-temperature steam environments compared with traditional zirconium-based alloys. However, radiation tolerance of Fe Cr Al alloys has not been fully established. In this study, a series of Fe Cr Al alloys with 10 18 wt % Cr and 2.9 4.9 wt % Al were neutron irradiated at 382 C to 1.8 dpa to investigate the irradiation-induced microstructural and mechanical property evolution as a function of alloy composition. Dislocation loops with Burgers vector of a/2 111 and a 100 were detected and quantified. Results indicate precipitation of Cr-rich is primarily dependent on the bulk chromium composition. Mechanical testing of sub-size-irradiated tensile specimens indicates the hardening response seen after irradiation is dependent on the bulk chromium composition. Furthermore, a structure property relationship was developed; it indicated that the change in yield strength after irradiation is caused by the formation of these radiation-induced defects and is dominated by the large number density of Cr-rich α' precipitates at sufficiently high chromium contents after irradiation.

  11. Processing of Mn-Al nanostructured magnets by spark plasma sintering and subsequent rapid thermal annealing

    NASA Astrophysics Data System (ADS)

    Saravanan, P.; Vinod, V. T. P.; Černík, Miroslav; Selvapriya, A.; Chakravarty, Dibyendu; Kamat, S. V.

    2015-01-01

    The potential of spark plasma sintering (SPS) in combination with rapid thermal annealing (RTA) for the processing of Mn-Al nanostructured magnets is explored in this study. Ferromagnetic α-Mn alloy powders were processed by high-energy ball milling using Mn (56 at%) and Al (44 at%) as constituent metal elements. The alloying action between Mn and Al due to intensive milling was studied by X-ray diffraction and field-emission scanning electron microscope; while the phase transformation kinetics was investigated using differential scanning calorimetry. The evolution of ferromagnetic properties in the as-milled powders was studied by superconducting quantum interference device (SQUID). Among the Mn-Al alloy powders collected at various milling intervals, the 25 h milled Mn-Al powders showed a good combination of coercivity, Hc (11.3 kA/m) and saturation magnetization, Ms (5.0 A/m2/kg); accordingly, these powders were chosen for SPS. The SPS experiments were conducted at different temperatures: 773, 873 and 973 K and its effect on the density, phase composition and magnetic properties of the Mn-Al bulk samples were investigated. Upon increasing the SPS temperature from 773 to 973 K, the bulk density was found to increase from 3.6 to 4.0 g/cm3. The occurrence of equilibrium β-phase with significant amount of γ2-phase was obvious at all the SPS temperatures; however, crystallization of some amount of τ-phase was evident at 973 K. Irrespective of the SPS temperatures, all the samples demonstrated soft magnetic behavior with Hc and Ms values similar to those obtained for the 25 h milled powders. The magnetic properties of the SPSed samples were significantly improved upon subjecting them to RTA at 1100 K. Through the RTA process, Hc values of 75, 174 and 194 kA/m and Ms values of 19, 21 and 28 A/m2/kg were achieved for the samples SPSed at 773, 873 and 973 K, respectively. The possible reasons for the observed improvement in the magnetic properties of the SPSed

  12. Substitution in ce2tsi3 intermetallic compositions with t = (Cr, Mn, Fe, Co, or Ni) x (Pd or Au) 1-x. Technical report No. 30

    SciTech Connect

    1996-07-10

    Alloys of composition Ce2(3d/T)Si3, with `3d` one of Cr, Mn, Fe, Co or Ni and `T` being Pd or Au, were separated and examined by powder x-ray diffraction. Select single phase compositions were further examined by magnetic susceptibility, by resistivity for the Pd and Co end-members and by specific heat for Ce2CoSi3. For compounds not containing cobalt, effective cerium moments consistent with trivalent cerium were observed. A re-examination of the AlB2 related structure of Ce2CoSi3 by single crystal methods revealed ordering of cobalt within the CoSi3 hexagonal layer. Magnetic susceptibility, resistance and specific heat measurements suggest valence fluctuation behavior of the cerium in Ce2CoSi3. A return to trivalent cerium magnetic behavior occurs on increasing palladium or gold substitution for cobalt.

  13. Energy transfer between Eu-Mn and photoluminescence properties of Ba0.75Al11O17.25-BaMgAl10O17:Eu2+,Mn2+ solid solution

    NASA Astrophysics Data System (ADS)

    Zhou, Jun; Wang, Yuhua; Liu, Bitao; Li, Feng

    2010-08-01

    In order to evaluate the energy transfer between Eu-Mn in Ba0.75Al11O17.25-BaMgAl10O17 solid solution, Ba0.75Al11O17.25-BaMgAl10O17:Eu2+,Mn2+ phosphors were prepared by flux method. The crystal structure and the morphology of the solid solution were demonstrated by x-ray dirrfactometer and scanning electron microscopy. The photoluminescence mechanisms were explained by the energy transfer of Eu2+ to Mn2+ and the Dexter theory. A redshift of green emission peak and a decrease in decay time with the increase in Mn2+ concentration were observed. These phenomena are attributed to the formation of Mn2+ paired centers after analysis by a method of Pade approximations.

  14. Elevated Temperature Deformation of Fe-39.8Al and Fe-15.6Mn-39.4Al

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. Daniel

    2004-01-01

    The elevated temperature compressive properties of binary Fe-39.8 at % Al and Fe-15.6Mn-39.4Al have been measured between 1000 and 1300 K at strain rates between 10(exp 7) and 10(exp 3)/ s. Although the Mn addition to iron aluminide did not change the basic deformation characteristics, the Mn-modified alloy was slightly weaker. In the regime where deformation of FeAl occurs by a high stress exponent mechanism (n = 6), strength increases as the grain size decreases at least for diameters between approx. 200 and approx. 10 microns. Due to the limitation in the grain size-flow stress-temperature-strain rate database, the influence of further reductions of the grain size on strength is uncertain. Based on the appearance of subgrains in deformed iron aluminide, the comparison of grain diameters to expected subgrain sizes, and the grain size exponent and stress exponent calculated from deformation experiments, it is believed that grain size strengthening is the result of an artificial limitation on subgrain size as proposed by Sherby, Klundt and Miller.

  15. Synthesis of TiB2/Fe-Cr-Al nanocomposite powder.

    PubMed

    Sachan, Ritesh; Park, Jong-Woo

    2008-10-01

    In this study, a route for synthesizing TiB2/Fe-Cr-Al nanocomposite is proposed via high energy ball milling by using directly coarse powders of TiB2, Fe, Cr and Al. Various compositions of these powder mixtures are milled up to 48 hrs to investigate the effect of composition on the crystalline refinement. The crystalline size is analyzed by an X-ray diffractometer for powder samples containing 30 to 100 wt% TiB2 (the rest of the powder consists of Fe-20 wt%Cr-5 wt%Al composition). The crystalline size after 48 hrs of ball milling decreases with increasing TiB2, and then again increases after reaching a minimum value of 18 nm at 70% TiB2. By transmission electron microscopic analysis, it is confirmed that particles of TiB2 are significantly reduced and finely dispersed in the Fe-Cr-Al matrix. The particle size of TiB2 is found around 20-25 nm, reinforced in the matrix. Considering the results of this study, the proposed mechanical milling route can be recommended as a promising way for fabrication of TiB2/Fe-Cr-Al nanocomposite powder. PMID:19198473

  16. LPE growth of Mn, Ni- and Al-substituted copper ferrite films

    NASA Astrophysics Data System (ADS)

    van der Straten, P. J. M.; Metselaar, R.

    1980-06-01

    Single-crystalline Mn-, Ni-, and Al-substituted copper ferrite films are grown by the LPE method from a PbO-B2O3 flux on (111)-MgO substrates. Solid solutions between copper ferrite and Mn3O4, NiFe2O4, and CuAl2O4 are obtained. The segregation coefficients for Ni and Al are shown to be linearly dependent on the growth temperature. From domain-structure observations and from torque measurements it is concluded that a positive uniaxial anisotropy is present in the copper ferrite films. After stress relief at the deposition temperature a stress develops during cooling to room temperature due to a difference in thermal expansion coefficients of film and substrate. This stress is responsible for the observed anisotropy.

  17. Characterization of Al-Mn particles in AZ91D investment castings

    SciTech Connect

    Lun Sin, S.; Dube, D. Tremblay, R.

    2007-10-15

    Manganese is currently added to Mg-Al alloys in order to improve the corrosion behavior of cast components. A part of this manganese is dissolved in the magnesium matrix and the balance is found as fine Al(Mn,Fe) particles dispersed within castings. For AZ91D specimens prepared using the plaster mould investment casting process, these particles were observed in very large quantity at the surface of castings. These particles were characterized by scanning electron microscopy and electron probe microanalysis. It was found that they consist of Al{sub 8}Mn{sub 5} phase and that their morphology and size depend on local solidification conditions. Their presence at the surface of the castings is related to low solidification rates and reduced thermal gradients at the mould/metal interface.

  18. Electric, magnetic, and thermo-electric properties of Cr doped La0.8Ca0.2Mn1-xCrxMnO3 manganites

    NASA Astrophysics Data System (ADS)

    Manjunatha, S. O.; Rao, Ashok; Babu, P. D.; Chand, Tara; Okram, G. S.

    2016-07-01

    A detailed study of the structural, magnetic, magneto-transport and thermoelectric properties of polycrystalline La0.8Ca0.2Mn1-xCrxMnO3 (0Cr-content, both TMI and TC are observed to decrease. The electrical resistivity data is analyzed using different theoretical models at various regions viz., metallic, insulating and percolation region. Analysis in the metallic region (TTMI) is well described using SPH model. However, the resistivity data in the whole temperature range is analyzed using a phenomenological model based on phase segregation of ferromagnetic metallic and paramagnetic insulating regions. Thermoelectric power, S measurements were performed to understand the conduction mechanism and to ascertain the types of charge carrier responsible for conduction. It is observed that pristine as well as Cr-doped compounds show positive value of S which demonstrates that the charge carriers are holes.

  19. Nature, density, and catalytic role of exposed species on dispersed VOx/CrOx/Al2O3 catalysts.

    PubMed

    Yang, Shuwu; Iglesia, Enrique; Bell, Alexis T

    2006-02-16

    The structure and surface composition of binary oxides consisting of CrO(x) and VO(x) dispersed on alumina and their effects on the rate and selectivity of oxidative dehydrogenation (ODH) of propane were examined and compared with those for CrO(x) and VO(x) dispersed on alumina. VO(x) deposition on an equivalent CrO(x) monolayer on alumina and deposition of CrO(x) on an equivalent monolayer of VO(x) deposited on alumina led to CrVO(4) species during thermal treatment with concomitant reduction of Cr(6+) to Cr(3+). Autoreduction of Cr(6+) to Cr(3+) is also detected for CrO(x), even without the presence of VO(x). Infrared spectroscopy of NO adsorbed at 153 K probes the relative abundance of alumina and of V(5+), Cr(3+), and Cr(6+) at surfaces. This technique detects differences in the surface composition of VO(x)/CrO(x)()/Al(2)O(3) and CrO(x)/VO(x)/Al(2)O(3). The first of these samples is enriched in VO(x) relative to CrO(x) compared with the second sample. Consistent with this finding, VO(x)/CrO(x)/Al(2)O(3) and CrO(x)/VO(x)/Al(2)O(3) are distinguishable in their ODH activities and propene selectivities. The highest ODH activity and propene selectivity is observed for VO(x)/CrO(x)/Al(2)O(3), which exhibits a surface enriched in VO(x) and having a low surface concentration of Cr(6+). PMID:16471878

  20. Ab initio study of Fe{sub 2}MnZ (Al, Si, Ge) Heusler alloy using GGA approximation

    SciTech Connect

    Jain, Vivek Kumar Jain, Vishal Lakshmi, N. Venugopalan, K.

    2014-04-24

    Density functional theory based on FP-LAPW method used to investigate the electronic structure of Fe{sub 2}MnZ, shows that the total spin magnetic moment shows a trend consistent with the Slater–Pauling curve. The Fe and Mn magnetic moment depend on choice of Z element although the magnetic moment of Z element is negative and less than 0.1 μ{sub B}. Spin polarization calculations evidence 100% spin polarization for Fe{sub 2}MnSi. Fe{sub 2}MnAl and Fe{sub 2}MnGe show metallic behavior with 93%, 98% spin polarization.

  1. The structure, Raman spectroscopy and evidence of ferromagnetic transition in CuCr1-xMxO2 (M=Mn and Rh) compounds

    NASA Astrophysics Data System (ADS)

    Elkhouni, T.; Amami, M.; Colin, C. V.; Strobel, P.; Ben Salah, A.

    2014-04-01

    The CuCr1-xMxO2 (M=Mn, Rh) polycrystalline powders were synthesized by the direct solid state reaction of Cu2O and M2O3 (M=trivalent cation or mixer of trivalent cation for transition metal). The magnetic susceptibility was measured in the temperature range of 0-300 K. It was found that the magnetic susceptibility (χ) increases rapidly with the doping of Cr3+ by Mn3+ and Rh3+ ions with existence of paramagnetic substance at low temperature. With the substitution of magnetic Mn3+ and Rh3+ for Cr3+ (S=3/2), the antiferromagnetic (AF) transition becomes broader and the transition temperature increases. However, at low temperature, the magnetic data for CuCr1-xMxO2 (M=Mn, Rh) show evidence for weak ferromagnetic (FM) transition between 100 K and 130 K. Clear hysteresis loops indicate that FM order exists in both of them Mn or Rh-doped samples at 4 K. All samples behave like semiconductors. The ferromagnetism properties can be attributed to the double exchange interaction between the Mn3+ or Rh3+ and Cr3+ semiconductors compounds.

  2. Investigating half-metallicity in PtXSb alloys (X=V, Mn, Cr, Co) at ambient and high pressure

    NASA Astrophysics Data System (ADS)

    Habbak, Enas L.; Shabara, Reham M.; Aly, Samy H.; Yehia, Sherif

    2016-08-01

    The structural, electronic, magnetic and elastic properties of half-Heusler alloys PtMnSb, PtVSb, PtCrSb and PtCoSb are investigated using first-principles calculation based on Density Functional Theory DFT. The Full Potential local Orbital (FPLO) method, within the General Gradient Approximation (GGA) and Local Spin Density Approximation (LSDA), have been used. The calculated structural, electronic and magnetic properties are in good agreement with available experimental and theoretical data. Using GGA approximation, only PtVSb shows a half-metallic behavior with a spin-down band gap and total magnetic moment of 0.802 eV and 2 μB respectively. Both of PtVSb and PtMnSb alloys are half-metallic with spin-down band gaps of 0.925 eV and 0.832 eV and magnetic moments of 2 μB and 4 μB respectively using LSDA approximation. The bulk modulus and its first pressure-derivative of these alloys are calculated using the modified Birch-Murnaghan equation of state (EOS). The effect of pressure on the lattice constant, energy gap and bulk modulus is investigated. Under pressure, PtMnSb and PtCrSb turn into half-metallic alloys at nearly 6 GPa and 27 GPa respectively using GGA approximation.

  3. Sediment fractionation of Cu, Ni, Zn, Cr, Mn, and Fe in one experimental and three natural marshes

    SciTech Connect

    Lindau, C.W.; Hossner, L.R.

    1982-07-01

    Dredged sediments from the Gulf Intracoastal Waterway near Galveston, Tex., were used as a substrate material in the construction of an experimental intertidal salt marsh. Selected substrate properties were compared with those of established marshes. Clay mineralogical properties of the experimental marsh were compared with those of three nearby natural marshes. A sequential chemical extraction procedure was used to obtain data on the partitioning of micronutrients and heavy metals among selected marsh substrate fractions. Clay minerals found in the sediments of the experimental marsh were equivalent to those identified in the natural marshes. Total elemental substrate concentrations of Cu, Ni, Cr, Zn, Mn, and Fe averaged 7.9, 8.6, 25.5, 25.2, 123, and 12,200 ..mu..g/g, respectively, over the four marsh sites. Copper, nickel, zinc, and chromium displayed only minor variations in substrate partitioning between the experimental and natural marsh samples. Micronutrients and heavy metal concentrations in the exchangeable and water-soluble fraction were low compared with other fractions. Approximately 30% of the total substrate Cu, Ni, and Zn was associated with the organic matter fraction. Metals fixed within the lattice structures of clay and silicate minerals ranged from 20% Mn for experimental marsh samples to 90% Cr for one of the natural marshes. Major differences in Mn and Fe substrate partitioning were observed when the experimental marsh samples were compared with those of the natural marshes.

  4. Influence of recrystallization on phase separation kinetics of oxide dispersion strengthened Fe Cr Al alloy

    SciTech Connect

    Capdevila, C.; Miller, Michael K; Pimentel, G.; Chao, J.

    2012-01-01

    The effect of different starting microstructures on the kinetics of Fe-rich ({alpha}) and Cr-rich ({alpha}') phase separation during aging of Fe-Cr-Al oxide dispersion strengthened (ODS) alloys has been analyzed with a combination of atom probe tomography and thermoelectric power measurements. The results revealed that the high recrystallization temperature necessary to produce a coarse grained microstructure in Fe-base ODS alloys affects the randomness of Cr-atom distributions and defect density, which consequently affect the phase separation kinetics at low annealing temperatures.

  5. Role of Y in the oxidation resistance of CrAlYN coatings

    NASA Astrophysics Data System (ADS)

    Domínguez-Meister, S.; El Mrabet, S.; Escobar-Galindo, R.; Mariscal, A.; Jiménez de Haro, M. C.; Justo, A.; Brizuela, M.; Rojas, T. C.; Sánchez-López, J. C.

    2015-10-01

    CrAlYN coatings with different aluminum (4-12 at.%) and yttrium (2-5 at.%) contents are deposited by d.c. reactive magnetron sputtering on silicon and M2 steel substrates using metallic targets and Ar/N2 mixtures. The influence of the nanostructure and chemical elemental distribution on the oxidation resistance after heating in air at 1000 °C is studied by means of cross-sectional scanning electron microscopy (X-SEM), energy dispersive X-ray analysis (EDX), X-ray diffraction (XRD) and glow discharge optical emission spectroscopy (GD-OES). The sequential exposure to the metallic targets during the synthesis leads to a multilayer structure where concentration of metallic elements (Cr, Al and Y) is changing periodically. A good oxidation resistance is observed when Al- and Y-rich regions are separated by well-defined CrN layers, maintaining crystalline coherence along the columnar structure. This protective behavior is independent of the type of substrate and corresponds to the formation of a thin mixed (Al, Cr)-oxide scale that protects the film underneath. The GD-OES and XRD analysis have demonstrated that Y acts as a reactive element, blocking the Fe and C atoms diffusion from the steel and favoring higher Al/Cr ratio in the passivation layer after heating. The coating with Y content around 4 at.% exhibited the best performance with a thinner oxide scale, a delay in the CrN decomposition and transformation to Cr2N, and a more effective Fe and C blocking.

  6. BeAl6O10: Cr3+: a promising active medium for femtosecond lasers

    NASA Astrophysics Data System (ADS)

    Petrov, V. V.; Pestryakov, Efim V.; Trunov, V. I.; Kirpichnikov, A. V.; Alimpiev, A. I.

    2003-10-01

    The new laser crystals BeAl6O10:Cr3+ were grown, spectral-luminescence and CW laser properties were investigated and compared with those of well-known laser medium-alexandrite (BeAl2O4:Cr3+). CW laser generation on vibronic transition 4T2-4A2 of Cr3+ ions in BeAl6O10 crystals was realized in the range of 800-880 nm under Ar+ laser pumping. The emission cross-section of laser transition was estimated about 6×10-20 cm2. We confirmed these crystals are perspective for generation of femtosecond pulses in the near IR region under LD pumping.

  7. Effect of Microstructure on Creep in Directionally Solidified NiAl-31Cr-3Mo

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. Daniel; Raj, S. V.; Locci, I. E.

    2001-01-01

    The 1200 to 1400 K slow strain rate characteristics of the directionally solidified (DS) eutectic Ni-33Al-31Cr-3 Mo have been determined as a function of growth rate. While differences in the light optical level microstructure were observed in alloys grown at rates ranging from 7.6 to 508 mm/h, compression testing indicated that all had essentially the same strength. The exception was Ni-33 Al-31Cr-3Mo DS at 25.4 mm/h which was slightly stronger than the other growth velocities; no microstructural reason could be found for this improvement. Comparison of the approximately 1300 K properties revealed that four different DS NiAl-34(Cr,Mo) alloys have a similar creep resistance which suggests that there is a common, but yet unknown, strengthening mechanism.

  8. Effect of Microstructure on Creep in Directionally Solidified NiAl-31Cr-3Mo

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. D.; Raj, S. V.; Locci, I. E.

    2001-01-01

    The 1200 to 1400 K slow strain rate characteristics of the directionally solidified (DS) eutectic Ni-33Al-31Cr-3 Mo have been determined as a function of growth rate. While differences in the light optical level microstructure were observed in alloys grown at rates ranging from 7.6 to 508 mm/h, compression testing indicated that all had essentially the same strength. The exception was Ni-33Al-31Cr-3Mo DS at 25.4 mm/h which was slightly stronger than the other growth velocities; no microstructural reason could be found for this improvement. Comparison of the approx. 1300 K properties revealed that four different DS NiAl-34(Cr,Mo) alloys have a similar creep resistance which suggests that there is a common, but yet unknown, strengthening mechanism.

  9. Abrasive resistance of metastable V-Cr-Mn-Ni spheroidal carbide cast irons using the factorial design method

    NASA Astrophysics Data System (ADS)

    Efremenko, V. G.; Shimizu, K.; Cheiliakh, A. P.; Pastukhova, T. V.; Chabak, Yu. G.; Kusumoto, K.

    2016-06-01

    Full factorial design was used to evaluate the two-body abrasive resistance of 3wt%C-4wt%Mn-1.5wt%Ni spheroidal carbide cast irons with varying vanadium (5.0wt%-10.0wt%) and chromium (up to 9.0wt%) contents. The alloys were quenched at 920°C. The regression equation of wear rate as a function of V and Cr contents was proposed. This regression equation shows that the wear rate decreases with increasing V content because of the growth of spheroidal VC carbide amount. Cr influences the overall response in a complex manner both by reducing the wear rate owing to eutectic carbides (M7C3) and by increasing the wear rate though stabilizing austenite to deformation-induced martensite transformation. This transformation is recognized as an important factor in increasing the abrasive response of the alloys. By analyzing the regression equation, the optimal content ranges are found to be 7.5wt%-10.0wt% for V and 2.5wt%-4.5wt% for Cr, which corresponds to the alloys containing 9vol%-15vol% spheroidal VC carbides, 8vol%-16vol% M7C3, and a metastable austenite/martensite matrix. The wear resistance is 1.9-2.3 times that of the traditional 12wt% V-13wt% Mn spheroidal carbide cast iron.

  10. Microstructure and mechanical properties of (Ti,Al,Zr)N/(Ti,Al,Zr,Cr)N films on cemented carbide substrates

    NASA Astrophysics Data System (ADS)

    Zhao, Shi-lu; Zhang, Jun; Zhang, Zhen; Wang, Shuang-hong; Zhang, Zheng-gui

    2014-01-01

    (Ti,Al,Zr)N/(Ti,Al,Zr,Cr)N bilayer films were deposited on cemented carbide (WC-8%Co) substrates by multi-arc ion plating (MAIP) using two Ti-Al-Zr alloy targets and one pure Cr target. To investigate the composition, morphology, and crystalline structure of the bilayer films, a number of complementary methods of elemental and structural analysis were used, namely, scanning electron microscopy (SEM), energy disperse X-ray spectroscopy (EDS), and X-ray diffraction (XRD). Adhesive strength and mechanical properties of the films were evaluated by scratch testing and Vickers microindentation, respectively. It is shown that the resulting films have a TiN-type face-centered cubic (FCC) structure. The films exhibit fully dense, uniform, and columnar morphology. Furthermore, as the bias voltages vary from -50 to -200 V, the microhardness (max. Hv0.01 4100) and adhesive strength (max. > 200 N) of the bilayer films are superior to those of the (Ti,Al,Zr)N and (Ti,Al,Zr,Cr)N monolayer films.

  11. Carriers-mediated ferromagnetic enhancement in Al-doped ZnMnO dilute magnetic semiconductors

    SciTech Connect

    Saleem, Murtaza; Siddiqi, Saadat A.; Atiq, Shahid; Anwar, M. Sabieh; Hussain, Irshad; Alam, Shahzad

    2011-11-15

    Nano-crystalline Zn{sub 0.95-x}Mn{sub 0.05}Al{sub x}O (x = 0, 0.05, 0.10) dilute magnetic semiconductors (DMS) were synthesized by sol-gel derived auto-combustion. X-ray diffraction (XRD) analysis shows that the samples have pure wurtzite structure typical of ZnO without the formation of secondary phases or impurity. Crystallite sizes were approximated by Scherrer formula while surface morphology and grain sizes were measured by field emission scanning electron microscopy. Incorporation of Mn and Al into the ZnO structure was confirmed by energy-dispersive X-ray analysis. Temperature dependent electrical resistivity measurements showed a decreasing trend with the doping of Al in ZnMnO, which is attributable to the enhancement of free carriers. Vibrating sample magnetometer studies confirmed the presence of ferromagnetic behavior at room temperature. The results indicate that Al doping results in significant variation in the concentration of free carriers and correspondingly the carrier-mediated magnetization and room temperature ferromagnetic behavior, showing promise for practical applications. We attribute the enhanced saturation magnetization and electrical conductivity to the exchange interaction mediated by free electrons.

  12. A re-evaluation of the Mn-Cr systematics of olivine from the angrite meteorite D’Orbigny using Secondary Ion Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    McKibbin, Seann J.; Ireland, Trevor R.; Amelin, Yuri; Holden, Peter; Sugiura, Naoji

    2013-12-01

    ‘Quenched’ angrite meteorites are among the best time markers of igneous activity in early formed planetesimals of the Solar System. They can be precisely dated by the Mn-Cr extinct nuclide decay system because they contain olivine with high Mn/Cr. Nevertheless, there is disagreement between various determinations of the initial 53Mn/55Mn for this meteorite, hindering their use for cross-calibration between chronometric systems and between Secondary Ion Mass Spectrometry (SIMS) and bulk measurement techniques. Here we re-evaluate the Mn-Cr systematics of olivine from the quenched angrite D’Orbigny using Sensitive High-mass Resolution Ion Micro Probe Reverse Geometry (SHRIMP-RG) to search for heterogeneity in isotope systematics and check for inter-laboratory bias. We investigated possible bias arising due to different data reduction methods and have paid careful attention to the relative sensitivities of Mn and Cr by utilising a three-component mixing model to correct for matrix effects associated with Mg, Fe and Ca zoning in angrite olivine. We have determined an initial 53Mn/55Mn of 3.60 (±0.39) × 10-6 and 3.44 (±0.29) × 10-6 (2σ errors) for D’Orbigny olivine by the Mean of Ratios and Ratio of Total Counts data reduction methods. These values are in agreement with those found by some previous bulk and mineral-scale determinations, and with the generally accepted initial 53Mn/55Mn of this meteorite, but not with previous SIMS work on this material. The source of this discrepancy remains unclear. We can exclude heterogeneity in D’Orbigny as a source of discrepancy because we used the same sample and the meteorite appears to have consistent initial 53Mn/55Mn over both micro- and macro-scales. The discrepancy between this and the previous SIMS study probably reflects an unrecognised systematic analytical bias, possibly associated with relative sensitivities of Mn and Cr or with mass spectrometric backgrounds (isobaric interferences or scattered ions

  13. Phase Transformations of an Fe-0.85 C-17.9 Mn-7.1 Al Austenitic Steel After Quenching and Annealing

    NASA Astrophysics Data System (ADS)

    Cheng, Wei-Chun

    2014-09-01

    Low-density Mn-Al steels could potentially be substitutes for commercial Ni-Cr stainless steels. However, the development of the Mn-Al stainless steels requires knowledge of the phase transformations that occur during the steel making processes. Phase transformations of an Fe-0.85 C-17.9 Mn-7.1 Al (wt.%) austenitic steel, which include spinodal decomposition, precipitation transformations, and cellular transformations, have been studied after quenching and annealing. The results show that spinodal decomposition occurs prior to the precipitation transformation in the steel after quenching and annealing at temperatures below 1023 K and that coherent fine particles of L12-type carbide precipitate homogeneously in the austenite. The cellular transformation occurs during the transformation of high-temperature austenite into lamellae of austenite, ferrite, and kappa carbide at temperatures below 1048 K. During annealing at temperatures below 923 K, the austenite decomposes into lamellar austenite, ferrite, κ-carbide, and M23C6 carbide grains for another cellular transformation. Last, when annealing at temperatures below 873 K, lamellae of ferrite and κ-carbide appear in the austenite.

  14. Elastic Modulus Measurement of ORNL ATF FeCrAl Alloys

    SciTech Connect

    Thompson, Zachary T.; Terrani, Kurt A.; Yamamoto, Yukinori

    2015-10-01

    Elastic modulus and Poisson’s ratio for a number of wrought FeCrAl alloys, intended for accident tolerant fuel cladding application, are determined via resonant ultrasonic spectroscopy. The results are reported as a function of temperature from room temperature to 850°C. The wrought alloys were in the fully annealed and unirradiated state. The elastic modulus for the wrought FeCrAl alloys is at least twice that of Zr-based alloys over the temperature range of this study. The Poisson’s ratio of the alloys was 0.28 on average and increased very slightly with increasing temperature.

  15. Development and quality assessments of commercial heat production of ATF FeCrAl tubes

    SciTech Connect

    Yamamoto, Yukinori

    2015-09-01

    Development and quality assessment of the 2nd generation ATF FeCrAl tube production with commercial manufacturers were conducted. The manufacturing partners include Sophisticated Alloys, Inc. (SAI), Butler, PA for FeCrAl alloy casting via vacuum induction melting, Oak Ridge National Laboratory (ORNL) for extrusion process to prepare the master bars/tubes to be tube-drawn, and Rhenium Alloys, Inc. (RAI), North Ridgeville, OH, for tube-drawing process. The masters bars have also been provided to Los Alamos National Laboratory (LANL) who works with Century Tubes, Inc., (CTI), San Diego, CA, as parallel tube production effort under the current program.

  16. The effect of yttrium and thorium on the oxidation behavior of Ni-Cr-Al alloys

    NASA Technical Reports Server (NTRS)

    Kumar, A.; Douglass, D. L.; Nasrallah, M.

    1974-01-01

    The investigation reported included a determination of the optimum composition of a Ni-Cr-Al ternary alloy with respect to oxidation resistance and minimum film-spalling tendencies. Yttrium and thorium in small amounts were added to the ternary alloy and an investigation of the oxidation mechanism and the oxide scale adherence was conducted. It was found that the oxidation mechanism of Ni-Cr-Al ternary alloys depends upon the composition of the alloy as well as the time, oxygen pressure, and temperature of oxidation.

  17. Microstructure and Phase Analysis in Mn-Al and Zr-Co Permanent Magnets

    NASA Astrophysics Data System (ADS)

    Lucis, Michael J.

    In America's search for energy independence, the development of rare-earth free permanent magnets is one hurdle that still stands in the way. Permanent magnet motors provide a higher efficiency than induction motors in applications such as hybrid vehicles and wind turbines. This thesis investigates the ability of two materials, Mn-Al and Zr-Co, to fill this need for a permanent magnet material whose components are readily available within the U.S. and whose supply chain is more stable than that of the rare-earth materials. This thesis focuses on the creation and optimization of these two materials to later be used as the hard phase in nanocomposites with high energy products (greater than 10 MGOe). Mn-Al is capable of forming the pure L10 structure at a composition of Mn54Al43C3. When Mn is replaced by Fe or Cu using the formula Mn48Al43C3T6 the anisotropy constant is lowered from 1.3·107 ergs/cm3 to 1.0·107 ergs/cm3 and 0.8·10 7 ergs/cm3 respectively. Previous studies have reported a loss in magnetization in Mn-Al alloys during mechanical milling. The reason for this loss in magnetization was investigated and found to be due to the formation of the equilibrium beta-Mn phase of the composition Mn3Al2 and not due to oxidation or site disorder. It was also shown that fully dense Mn-Al permanent magnets can be created at hot pressing temperatures at or above 700°C and that the epsilon-phase to tau-phase transition and consolidation can be combined into a single processing step. The addition of small amounts of Cu to the alloy, 3% atomic, can increase the compaction density allowing high densities to be achieved at lower pressing temperatures. While the structure is still under debate, alloys at the composition Zr2Co11 in the Zr-Co system have been shown to have hard magnetic properties. This thesis shows that multiple structures exist at this Zr2Co11 composition and that altering the cooling rate during solidification of the alloy affects the ratio of the phase

  18. Study of the effect of annealing on defects in Fe Mn Si Cr Ni C alloy by slow positron beam

    NASA Astrophysics Data System (ADS)

    Mostafa, Khaled. M.; De Baerdemaeker, J.; Van Caenegem, N.; Segers, D.; Houbaert, Y.

    2008-10-01

    FeMnSi shape memory alloys (SMAs) have received much attention as one-way SMAs due to their cost-effectiveness. Variable-energy (0-30 keV) positron beam studies have been carried out on a Fe-Mn-Si-Cr-Ni-C alloy with different degrees of deformation. Doppler broadening profiles of the positron annihilation as a function of incident positron energy were shown to be quite sensitive to defects introduced by deformation. The variation of the nature and the concentration of defects are studied as a function of isochronal annealing temperature. These results are correlated with the data measured with the positron annihilation lifetime spectroscopy (PALS). The positron annihilation results are compared to XRD and optical microscopy (OM).

  19. Investigation of thermal, mechanical and magnetic behaviors of the Cu-11%Al alloy with Ag and Mn additions

    SciTech Connect

    Silva, R.A.G.; Paganotti, A.; Gama, S.; Adorno, A.T.; Carvalho, T.M.; Santos, C.M.A.

    2013-01-15

    The investigation of thermal, mechanical and magnetic behaviors of the Cu-11%Al, Cu-11%Al-3%Ag, Cu-11%Al-10%Mn and Cu-11%Al-10%Mn-3%Ag alloys was made using microhardness measurements, differential scanning calorimetry, X-ray diffractometry, scanning electron microscopy, energy dispersion X-ray spectroscopy and magnetic moment change with applied field measurement. The results indicated that the Mn addition changes the phase stability range, the microhardness values and makes undetectable the eutectoid reaction in annealed Cu-11%Al and Cu-11%Al-3%Ag alloys while the presence of Ag does not modify the phase transformation sequence neither microhardness values of the annealed Cu-11%Al and Cu-11%Al-10%Mn alloys, but it increases the magnetic moment of this latter at about 2.7 times and decreases the rates of eutectoid and peritectoid reactions of the former. - Highlights: Black-Right-Pointing-Pointer The microstructure of Cu-Al alloy is modified in the Ag presence. Black-Right-Pointing-Pointer ({alpha} + {gamma}) phase is stabilized down to room temperature when Ag is added to Cu-Al alloy. Black-Right-Pointing-Pointer Ag-rich phase modifies the magnetic characteristics of Cu-Al-Mn alloy.

  20. Influence of Temperature on Fatigue-Induced Martensitic Phase Transformation in a Metastable CrMnNi-Steel

    NASA Astrophysics Data System (ADS)

    Biermann, Horst; Glage, Alexander; Droste, Matthias

    2016-01-01

    Metastable austenitic steels can exhibit a fatigue-induced martensitic phase transformation during cyclic loading. It is generally agreed that a certain strain amplitude and a threshold of the cumulated plastic strain must be exceeded to trigger martensitic phase transformation under cyclic loading. With respect to monotonic loading, the martensitic phase transformation takes place up to a critical temperature—the so-called M d temperature. The goal of the present investigation is to determine an M d,c temperature which would be the highest temperature at which a fatigue-induced martensitic phase transformation can take place. For this purpose, fatigue tests controlled by the total strain were performed at different temperatures. The material investigated was a high-alloy metastable austenitic steel X3CrMnNi16.7.7 (16.3Cr-7.2Mn-6.6Ni-0.03C-0.09N-1.0Si) produced using the hot pressing technique. The temperatures were set in the range of 283 K (10 °C) ≤ T ≤ 473 K (200 °C). Depending on the temperature and strain amplitude, the onset of the martensitic phase transformation shifted to different values of the cumulated plastic strain, or was inhibited completely. Moreover, it is known that metastable austenitic CrMnNi steels with higher nickel contents can exhibit the deformation-induced twinning effect. Thus, at higher temperatures and strain amplitudes, a transition from the deformation-induced martensitic transformation to deformation-induced twinning takes place. The fatigue-induced martensitic phase transformation was monitored during cyclic loading using a ferrite sensor. The microstructure after the fatigue tests was examined using the back-scattered electrons, the electron channeling contrast imaging and the electron backscatter diffraction techniques to study the temperature-dependent dislocation structures and phase transformations.

  1. Precipitation sensitivity to alloy composition in Fe-Cr-Mn austenitic steels developed for reduced activation for fusion application

    SciTech Connect

    Maziasz, P.J.; Klueh, R.L.

    1988-01-01

    Special austenitic steels are being designed in which alloying elements like Mo, Nb, and Ni are replaced with Mn, W, V, Ti, and/or Ta to reduce the long-term radioactivity induced by fusion reactor irradiation. However, the new steels still need to have properties otherwise similar to commercial steels like type 316. Precipitation strongly affects strength and radiation-resistance in austenitic steels during irradiation at 400--600/degree/C, and precipitation is also usually quite sensitive to alloy composition. The initial stage of development was to define a base Fe-Cr-Mn-C composition that formed stable austenite after annealing and cold-working, and resisted recovery or excessive formation of coarse carbide and intermetallic phases during elevated temperature annealing. These studies produced a Fe-12Cr-20Mn-0.25C base alloy. The next stage was to add the minor alloying elements W, Ti, V, P, and B for more strength and radiation-resistance. One of the goals was to produce fine MC precipitation behavior similar to the Ti-modified Fe-Cr-Ni prime candidate alloy (PCA). Additions of Ti+V+P+B produced fine MC precipitation along network dislocations and recovery/recrystallization resistance in 20% cold worked material aged at 800/degree/C for 166h, whereas W, Ti, W+Ti, or Ti+P+B additions did not. Addition of W+Ti+V+P+B also produced fine MC, but caused some sigma phase formation and more recrystallization as well. 29 refs., 14 figs., 9 tabs.

  2. Deformation and annealing study of NiCrAlY

    NASA Technical Reports Server (NTRS)

    Ebert, L. J.; Trela, D. M.

    1978-01-01

    The elevated temperature properties (tensile and creep) of NiCrALY, a nickel base alloy containing nominally 16% chromium, 4% aluminum, and 2 to 3% yttria (Y2O3) were evaluated and the optimal combination of thermomechanical treatments for maximum creep resistance was determined. Stored strain energy in as-extruded bars (14:1 extrusion ratio) permitted the development of a large grain size in the material when it was annealed at the maximum safe temperature 2450 F (1343 C). With a one-hour anneal at this temperature, the relatively fine grain size of the as-extruded material was changed to one in which the average grain diameter approached 1 mm, and the aspect ratio was about 10. The material was capable of being cold worked (by rolling) in amounts greater than 30% reduction in area. When the cold worked material was given a relaxation treatment, consisting of heating one hour at 1600 F(871 C), and then a high temperature anneal at 2450 F (1343 C) for one hour, both the high temperature strength and the high temperature creep resistance of the material was further enhanced.

  3. Importance of doping and frustration in itinerant Fe-doped Cr2Al

    SciTech Connect

    Susner, M. A.; Parker, D. S.; Sefat, A. S.

    2015-05-12

    We performed an experimental and theoretical study comparing the effects of Fe-doping of Cr2Al, an antiferromagnet with a N el temperature of 670 K, with known results on Fe-doping of antiferromagnetic bcc Cr. (Cr1-xFex)2Al materials are found to exhibit a rapid suppression of antiferromagnetic order with the presence of Fe, decreasing TN to 170 K for x=0.10. Antiferromagnetic behavior disappears entirely at x≈0.125 after which point increasing paramagnetic behavior is exhibited. Moreover, this is unlike the effects of Fe doping of bcc antiferromagnetic Cr, in which TN gradually decreases followed by the appearance of a ferromagnetic state. Theoretical calculations explain that the Cr2Al-Fe suppression of magnetic order originates from two effects: the first is band narrowing caused by doping of additional electrons from Fe substitution that weakens itinerant magnetism; the second is magnetic frustration of the Cr itinerant moments in Fe-substituted Cr2Al. In pure-phase Cr2Al, the Cr moments have an antiparallel alignment; however, these are destroyed through Fe substitution and the preference of Fe for parallel alignment with Cr. This is unlike bulk Fe-doped Cr alloys in which the Fe anti-aligns with the Cr atoms, and speaks to the importance of the Al atoms in the magnetic structure of Cr2Al and Fe-doped Cr2Al.

  4. Compositional variation of photoluminescence from Mn doped MgAl2O4 spinel

    NASA Astrophysics Data System (ADS)

    Sakuma, Takashi; Minowa, Shunsuke; Katsumata, Toru; Komuro, Shuji; Aizawa, Hiroaki

    2014-11-01

    Spinel (MgAl2O4) crystals doped with 1.0% Mn have been grown by floating zone (FZ) technique with various Mg compositions, x = MgO/Al2O3, from 0.2 to 1.0. Compositional variations of photoluminescence are evaluated for a fluorescence thermometer application using crystals grown. Strong photoluminescence (PL) peak is observed at λ from 512 to 520 nm from the crystals grown from compositions, x, from 0.3 to 1.0. Peak wavelength of PL increases linearly from 512 to 520 nm with x. Weak PL peaking at λ = 750 nm is also observed from the specimens. Compositional variations of PL are considered to be due to the variation of crystal field surrounding the Mn2+ ions. The variation of crystal field strength agrees with the compositional variation of lattice constant.

  5. Processing, Microstructure and Mechanical Properties of the CrMnFeCoNi High-Entropy Alloy

    NASA Astrophysics Data System (ADS)

    Gludovatz, Bernd; George, Easo P.; Ritchie, Robert O.

    2015-08-01

    Equiatomic multi-component alloys, referred to variously as high-entropy alloys, multi-component alloys, or compositionally complex alloys in the literature, have recently received significant attention in the materials science community. Some of these alloys can display a good combination of mechanical properties. Here, we review recent work on the processing, microstructure and mechanical properties of one of the first and most studied high-entropy alloys, namely the single-phase, face-centered cubic alloy CrMnFeCoNi, with emphasis on its excellent damage tolerance (strength with toughness) in the temperature range from room temperature down to liquid nitrogen temperature.

  6. Effects of cold rolling on the microstructure and mechanical properties of Fe-Ni-Mn-Mo-Ti-Cr maraging steels

    NASA Astrophysics Data System (ADS)

    Mahmudi, Abbas; Nedjad, Syamak Hossein; Behnam, Mir Masud Jabbari

    2011-10-01

    Effects of cold rolling on the microstructure and mechanical properties of Fe-Ni-Mn-Mo-Ti-Cr maraging steels were studied. To investigate the microstructure and mechanical properties, optical microscopy, scanning electron microscopy, X-ray diffraction, tensile test, and hardness test were used. The results show that the solution-annealing treatment in the cold-rolled steel redounds to the formation of submicrocrystalline Fe2(Mo, Ti) Laves phase particles, which are stable at high temperatures. These secondary Laves phase particles prevent from recrystallization at high temperatures and correspond to semi-brittle fracture in the subsequent aging treatment.

  7. Ferromagnetic interfacial interaction and the proximity effect in a Co2FeAl/(Ga,Mn)As bilayer.

    PubMed

    Nie, S H; Chin, Y Y; Liu, W Q; Tung, J C; Lu, J; Lin, H J; Guo, G Y; Meng, K K; Chen, L; Zhu, L J; Pan, D; Chen, C T; Xu, Y B; Yan, W S; Zhao, J H

    2013-07-12

    The magnetic properties of a Co2FeAl/(Ga,Mn)As bilayer epitaxied on GaAs (001) are studied both experimentally and theoretically. Unlike the common antiferromagnetic interfacial interaction existing in most ferromagnet-magnetic semiconductor bilayers, a ferromagnetic interfacial interaction in the Co2FeAl/(Ga,Mn)As bilayer is observed from measurements of magnetic hysteresis and x-ray magnetic circular dichroism. The Mn ions in a 1.36 nm thick (Ga,Mn)As layer remain spin polarized up to 400 K due to the magnetic proximity effect. The minor loops of the Co2FeAl/(Ga,Mn)As bilayer shift with a small ferromagnetic interaction field of +24 Oe and -23 Oe at 15 K. The observed ferromagnetic interfacial coupling is supported by ab initio density functional calculations. These findings may provide a viable pathway for designing room-temperature semiconductor spintronic devices through magnetic proximity effect. PMID:23889435

  8. Ferromagnetic Interfacial Interaction and the Proximity Effect in a Co2FeAl/(Ga,Mn)As Bilayer

    NASA Astrophysics Data System (ADS)

    Nie, S. H.; Chin, Y. Y.; Liu, W. Q.; Tung, J. C.; Lu, J.; Lin, H. J.; Guo, G. Y.; Meng, K. K.; Chen, L.; Zhu, L. J.; Pan, D.; Chen, C. T.; Xu, Y. B.; Yan, W. S.; Zhao, J. H.

    2013-07-01

    The magnetic properties of a Co2FeAl/(Ga,Mn)As bilayer epitaxied on GaAs (001) are studied both experimentally and theoretically. Unlike the common antiferromagnetic interfacial interaction existing in most ferromagnet-magnetic semiconductor bilayers, a ferromagnetic interfacial interaction in the Co2FeAl/(Ga,Mn)As bilayer is observed from measurements of magnetic hysteresis and x-ray magnetic circular dichroism. The Mn ions in a 1.36 nm thick (Ga,Mn)As layer remain spin polarized up to 400 K due to the magnetic proximity effect. The minor loops of the Co2FeAl/(Ga,Mn)As bilayer shift with a small ferromagnetic interaction field of +24Oe and -23Oe at 15 K. The observed ferromagnetic interfacial coupling is supported by ab initio density functional calculations. These findings may provide a viable pathway for designing room-temperature semiconductor spintronic devices through magnetic proximity effect.

  9. First-principles study on the magnetism and electronic structure in 3d transition metal (X=Sc, V, Cr, Mn, Fe, Ni, Cu) doped CoO

    NASA Astrophysics Data System (ADS)

    Liu, R. X.; Wang, X. C.; Chen, G. F.; Yang, B. H.

    2016-03-01

    We have studied the electronic structure and magnetism of the single transitional metal element X=Sc, V, Cr, Mn, Fe, Ni, Cu-doped CoO systems by first-principles calculations. At X=Sc, Cr, Cu, the binding energy of the doped systems is lower than pure CoO, suggesting that these systems are energetically stable. In the Sc, V, Cr, Mn, Fe, Ni, Cu-doped 2×2×2 CoO supercells, the total magnetic moments are 3.03, 5.64, 6.80, 7.70, 6.93, 2.30 and 1.96 μB, respectively. At X=Cr and Fe, the doped CoO systems are half-metallic with a high spin polarization. The large magnetic moment and high spin polarization in the Cr and Fe-doped CoO are important for the design of the spintronic devices.

  10. Structural, magnetic, and superconducting properties of pulsed-laser-deposition-grown La<mn>1.85mn> Sr<mn>0.15mn> CuO<mn>4mn> / La<mn>2mn>/>3mn> Ca<mn>1mn>/>3mn> MnO>3mn> superlattices on (001)-oriented LaSrAlO>4mn> substrates

    SciTech Connect

    Das, S.; Sen, K.; Marozau, I.; Uribe-Laverde, M. A.; Biskup, N.; Varela, M.; Khaydukov, Y.; Soltwedel, O.; Keller, T.; Döbeli, M.; Schneider, C. W.; Bernhard, C.

    2014-03-12

    Epitaxial La<mn>1.85mn> Sr<mn>0.15mn> CuO<mn>4mn> / La<mn>2mn>/>3mn> Ca<mn>1mn>/>3mn> MnO>3mn> (LSCO/LCMO) superlattices (SL) on (001)- oriented LaSrAlO4 substrates have been grown with pulsed laser deposition (PLD) technique. Their structural, magnetic and superconducting properties have been determined with in-situ reflection high energy electron diffraction (RHEED), x-ray diffraction, specular neutron reflectometry, scanning transmission electron microscopy (STEM), electric transport, and magnetization measurements. We find that despite the large mismatch between the in-plane lattice parameters of LSCO (a = 0.3779 nm) and LCMO (a = 0.387 nm) these superlattices can be grown epitaxially and with a high crystalline quality. While the first LSCO layer remains clamped to the LSAO substrate, a sizeable strain relaxation occurs already in the first LCMO layer. The following LSCO and LCMO layers adopt a nearly balanced state in which the tensile and compressive strain effects yield alternating in-plane lattice parameters with an almost constant average value. No major defects are observed in the LSCO layers, while a significant number of vertical antiphase boundaries are found in the LCMO layers. The LSCO layers remain superconducting with a relatively high superconducting onset temperature of Tconset ≈ 36 K. The macroscopic superconducting response is also evident in the magnetization data due to a weak diamagnetic signal below 10 K for H ∥ ab and a sizeable paramagnetic shift for H ∥ c that can be explained in terms of a vortex-pinning-induced flux compression. The LCMO layers maintain a

  11. Cycling of trace metals (Mn, Fe, Mo, U, V, Cr) in deep pore waters of intertidal flat sediments

    NASA Astrophysics Data System (ADS)

    Beck, Melanie; Dellwig, Olaf; Schnetger, Bernhard; Brumsack, Hans-Jürgen

    2008-06-01

    Trace metals (Mn, Fe, Mo, U, Cr, V) were studied in pore waters of an intertidal flat located in the German Wadden Sea. The study system is an example of a permeable tidal flat system where pore water exchange is affected by tidal driven pressure gradients besides diffusion. Permanently installed in situ samplers were used to extract pore waters down to 5 m depth throughout one year. The samplers were either located close to the tidal flat margin or in central parts of the tidal flat. Despite dynamic sedimentological and hydrological conditions, the general trends with depth in deep tidal flat pore waters are remarkably similar to those observed in deep sea environments. Rates of trace metal cycling must be comparably large in order to maintain the observed pore water profiles. Trace metals further show similar general trends with depth close to the margin and in central parts of the tidal flat. Seasonal sampling revealed that V and Cr vary concurrent with seasonal changes in dissolved organic carbon (DOC) concentration. This effect is most notable close to the tidal flat margin where sulphate, DOC, and nutrients vary with season down to some metres depth. Seasonal variations of Mn, Fe, Mo, and U are by contrast limited to the upper decimetres of the sediment. Their seasonal patterns depend on organic matter supply, redox stratification, and particulate matter deposited on sediment surfaces. Pore water sampling within one tidal cycle provides evidence for pore water advection in margin sediments. During low tide pore water flow towards the creekbank is generated by a hydraulic gradient suggesting that deep pore waters may be seeping out of creekbank sediments. Owing to the enrichment of specific elements like Mn in pore water compared to sea water, seeping pore waters may have an impact on the chemistry of the open water column. Mass balance calculations reveal that the impact of deep pore waters on the Mn budget in the open water column is below 4%. Mn deep pore

  12. Development of ODS FeCrAl for compatibility in fusion and fission energy applications

    DOE PAGESBeta

    Pint, Bruce A.; Dryepondt, Sebastien N.; Unocic, Kinga A.; Hoelzer, David T.

    2014-11-15

    In this paper, oxide dispersion strengthened (ODS) FeCrAl alloys with 12–15% Cr are being evaluated for improved compatibility with Pb-Li for a fusion energy application and with high temperature steam for a more accident-tolerant light water reactor fuel cladding application. A 12% Cr content alloy showed low mass losses in static Pb-Li at 700°C, where a LiAlO2 surface oxide formed and inhibited dissolution into the liquid metal. All the evaluated compositions formed a protective scale in steam at 1200°C, which is not possible with ODS FeCr alloys. However, most of the compositions were not protective at 1400°C, which is amore » general and somewhat surprising problem with ODS FeCrAl alloys that is still being studied. More work is needed to optimize the alloy composition, microstructure and oxide dispersion, but initial promising tensile and creep results have been obtained with mixed oxide additions, i.e. Y2O3 with ZrO2, HfO2 or TiO2.« less

  13. Development of ODS FeCrAl for compatibility in fusion and fission energy applications

    SciTech Connect

    Pint, Bruce A.; Dryepondt, Sebastien N.; Unocic, Kinga A.; Hoelzer, David T.

    2014-11-15

    In this paper, oxide dispersion strengthened (ODS) FeCrAl alloys with 12–15% Cr are being evaluated for improved compatibility with Pb-Li for a fusion energy application and with high temperature steam for a more accident-tolerant light water reactor fuel cladding application. A 12% Cr content alloy showed low mass losses in static Pb-Li at 700°C, where a LiAlO2 surface oxide formed and inhibited dissolution into the liquid metal. All the evaluated compositions formed a protective scale in steam at 1200°C, which is not possible with ODS FeCr alloys. However, most of the compositions were not protective at 1400°C, which is a general and somewhat surprising problem with ODS FeCrAl alloys that is still being studied. More work is needed to optimize the alloy composition, microstructure and oxide dispersion, but initial promising tensile and creep results have been obtained with mixed oxide additions, i.e. Y2O3 with ZrO2, HfO2 or TiO2.

  14. Development of ODS FeCrAl for Compatibility in Fusion and Fission Energy Applications

    NASA Astrophysics Data System (ADS)

    Pint, B. A.; Dryepondt, S.; Unocic, K. A.; Hoelzer, D. T.

    2014-12-01

    Oxide dispersion strengthened (ODS) FeCrAl alloys with 12-15% Cr are being evaluated for improved compatibility with Pb-Li for a fusion energy application and with high temperature steam for a more accident-tolerant light water reactor fuel cladding application. A 12% Cr content alloy showed low mass losses in static Pb-Li at 700°C, where a LiAlO2 surface oxide formed and inhibited dissolution into the liquid metal. All the evaluated compositions formed a protective scale in steam at 1200°C, which is not possible with ODS FeCr alloys. However, most of the compositions were not protective at 1400°C, which is a general and somewhat surprising problem with ODS FeCrAl alloys that is still being studied. More work is needed to optimize the alloy composition, microstructure and oxide dispersion, but initial promising tensile and creep results have been obtained with mixed oxide additions, i.e. Y2O3 with ZrO2, HfO2 or TiO2.

  15. Directly obtained τ-phase MnAl, a high performance magnetic material for permanent magnets

    NASA Astrophysics Data System (ADS)

    Fang, Hailiang; Kontos, Sofia; Ångström, Jonas; Cedervall, Johan; Svedlindh, Peter; Gunnarsson, Klas; Sahlberg, Martin

    2016-05-01

    The metastable tetragonal τ-phase has been directly obtained from casting Mn0.54Al0.46 and (Mn0.55Al0.45)100C2 using the drop synthesis method. The as-casted samples were ball milled to decrease the particle size and relaxed at 500 °C for 1 h. The phase composition, crystallographic parameters, magnetic properties and microstructure were systematically studied. The results reveal that the τ-phase could be directly obtained from drop synthesis. The highest Ms of 117 emu/g was achieved in the (Mn0.55Al0.45)100C2 where the τ-phase was stabilized by doping with carbon. Carbon doping increased the c/a ratio of the τ-phase as it occupies specific interstitial positions (½, ½, 0) in the structure. Furthermore, ball milling increases the coercivity (Hc) at the expense of a decrease in magnetic saturation (Ms). The increase in coercivity is explained by a decrease of grain size in conjunction with domain wall pinning due to defects introduced during the ball milling process.

  16. Microstructure, mechanical properties, and high-temperature oxidation resistance of boronized {gamma}-TiAl(Mn)

    SciTech Connect

    Kim, S.; Yoon, Y.; Kim, H.; Park, K.

    1997-12-31

    Titanium aluminide (TiAl) based intermetallic compounds are considered as potential materials for high-performance automobile and aircraft engine components and airframe applications because of their low density (3.8 g/cm{sup 3}), high melting temperature (1,480 C), and good elevated temperature strength retention. To improve the wear and high-temperature oxidation resistance of reactively sintered {gamma}-TiAl(Mn) intermetallic compounds, they were boronized in the temperature range of 900 to 1,100 C for 5 to 11 hours with powder mixtures of B{sub 4}C and Na{sub 2}B{sub 4}O{sub 7}. It was found that the coating layer consisted of three sublayers, i.e., outer, middle, and inner sublayers. The outer, middle, and inner sublayers were identified as a mixture of TiB{sub 2} and TiO{sub 2}, a mixture of Al{sub 2}O{sub 3} and TiO{sub 2}, and Ti-rich TiAl based compounds, respectively. The coating layer significantly improved the surface hardness and the wear and high-temperature oxidation resistances. The highest surface hardness (Hv {approx} 2,720) was obtained at 900 C for 11 hours. This surface hardness is much higher than that of TiAl(Mn) (Hv {approx} 400). In addition, the specimens boronized at both 1,000 and 1,050 C for 9 hours showed an excellent high-temperature oxidation resistance. It is believed that the boronizing on the TiAl(Mn) intermetallics is very effective to improve the wear and high-temperature oxidation resistances.

  17. 30 W Cr:LiSrAlF6 flashlamp-pumped pulsed laser

    NASA Astrophysics Data System (ADS)

    Samad, Ricardo Elgul; Baldochi, Sonia Licia; Calvo Nogueira, Gesse Eduardo; Dias Vieira, Nilson, Jr.

    2007-01-01

    We report the performance of a flashlamp-pumped Cr:LiSrAlF6 (Cr:LiSAF) laser developed and built by us. The pumping cavity incorporates filters that select the flashlamps' emission spectrum to match the absorption bands of the gain medium, allowing control of the amount of nonradiactive decay heat contribution of the optical cycle, minimizing thermal effects on the laser operation. The laser generated 2 J pulses at 15 Hz, resulting in 30 W of average power, the highest power extracted from a Cr:LiSAF rod laser to our knowledge. We were able to conclude that the laser efficiency is affected by resonator configuration changes due to thermal lens effects, and not to thermal quenching of the Cr:LiSAF luminescence.

  18. Properties and performance of the LiCaAlF6:Cr3+ laser material

    NASA Astrophysics Data System (ADS)

    Payne, Stephen A.; Chase, Lloyd L.; Atherton, L. Jeffrey; Caird, John A.; Kway, Wayne L.; Shinn, Michelle D.; Hughes, Robert S.; Smith, Larry K.

    1990-04-01

    The laser properties of the LiCaAlF6:Cr3+ (Cr:LiCAF) material are reviewed. The impact of the absorption and emission spectra on the laser performance is discussed. Laser-pumping and flashlamp-pumping experiments have shown that Cr:LiCAF has potential for high efficiency, although the presence of scattering losses remains a significant problem. The "gradient freeze" growth technique has been found to generate lower-loss material compared to Czochralski growth. The thermal lensing of Cr:LiCAF has been measured to be small and is in rough agreement with the magnitude expected on the basis of the intrinsic thermo-optical properties.

  19. 30 W Cr:LiSrAlF 6 flashlamp-pumped pulsed laser.

    PubMed

    Samad, Ricardo Elgul; Baldochi, Sonia Licia; Calvo Nogueira, Gesse Eduardo; Vieira, Nilson Dias

    2007-01-01

    We report the performance of a flashlamp-pumped Cr:LiSrAlF(6) (Cr:LiSAF) laser developed and built by us. The pumping cavity incorporates filters that select the flashlamps' emission spectrum to match the absorption bands of the gain medium, allowing control of the amount of nonradiactive decay heat contribution of the optical cycle, minimizing thermal effects on the laser operation. The laser generated 2 J pulses at 15 Hz, resulting in 30 W of average power, the highest power extracted from a Cr:LiSAF rod laser to our knowledge. We were able to conclude that the laser efficiency is affected by resonator configuration changes due to thermal lens effects, and not to thermal quenching of the Cr:LiSAF luminescence. PMID:17167580

  20. Examination of Multiphase (Zr,Ti)(V,Cr,Mn,Ni)2 Ni-MH Electrode Alloys: Part II. Solid-State Transformation of the Interdendritic B2 Phase

    NASA Astrophysics Data System (ADS)

    Bendersky, L. A.; Wang, K.; Boettinger, W. J.; Newbury, D. E.; Young, K.; Chao, B.

    2010-08-01

    Solidification microstructure of multicomponent (Zr,Ti)-Ni-(V,Cr,Mn,Co) alloys intended for use as negative electrodes in Ni-metal hydride (Ni-MH) batteries was studied in Part I of this series of articles. Part II of the series examines the complex internal structure of the interdendritic grains formed by solid-state transformation and believed to play an important role in the electrochemical charge/discharge characteristics of the overall alloy composition. By studying one alloy, Zr21Ti12.5V10Cr5.5Mn5.1Co5.0Ni40.2Al0.5Sn0.3, it is shown that the interdendritic grains solidify as a B2 (Ti,Zr)44(Ni,TM)56 phase, and then undergo transformation to Zr7Ni10-type, Zr9Ni11-type, and martensitic phases. The transformations obey orientation relationships between the high-temperature B2 phase and the low-temperature Zr-Ni-type intermetallics, and consequently lead to a multivariant structure. The major orientation relationship for the orthorhombic Zr7Ni10 type is [011]Zr7Ni10//[001]B2; (100)Zr7Ni10//(100)B2. The orientation relationship for the tetragonal Zr9Ni11 type is [001]Zr9Ni11//[001]B2; (130)Zr9Ni11//(100)B2. Binary Ni-Zr and ternary Ti-Ni-Zr phase diagrams were used to rationalize the formation of the observed domain structure.

  1. Hafnium influence on the microstructure of FeCrAl alloys

    NASA Astrophysics Data System (ADS)

    Geanta, V.; Voiculescu, I.; Stanciu, E.-M.

    2016-06-01

    Due to their special properties at high temperatures, FeCrAl alloys micro-alloyed with Zr can be regarded as potential materials for use at nuclear power plants, generation 4R. These materials are resistant to oxidation at high temperatures, to corrosion, erosion and to the penetrating radiations in liquid metal environments. Also, these are able to form continuously, by the self-generation process of an oxide coating with high adhesive strength. The protective oxide layers must be textured and regenerable, with a good mechanical strength, so that crack and peeling can not appear. To improve the mechanical and chemical characteristics of the oxide layer, we introduced limited quantities of Zr, Ti, Y, Hf, Ce in the range of 1-3%wt in the FeCrAl alloy. These elements, with very high affinity to the oxygen, are capable to stabilize the alumina structure and to improve the oxide adherence to the metallic substrate. FeCrAl alloys microalloyed with Hf were prepared using VAR (Vacuum Arc Remelting) unit, under high argon purity atmosphere. Three different experimental alloys have been prepared using the same metallic matrix of Fe-14Cr-5Al, by adding of 0.5%wt Hf, 1.0%wt Hf and respectively 1.5%wt Hf. The microhardness values for the experimental alloys have been in the range 154 ... 157 HV0.2. EDAX analyses have been performed to determine chemical composition on the oxide layer and in the bulk of sample and SEM analyze has been done to determine the microstructural features. The results have shown the capacity of FeCrAl alloy to form oxide layers, with different texture and rich in elements such as Al and Hf.

  2. Using oxygen and carbon stable isotopes, 53Mn-53Cr isotope systematics, and petrology to constrain the history of carbonates and water in the CR and CM chondrite parent bodies

    NASA Astrophysics Data System (ADS)

    Tyra, Mark Anthony

    I carried out a petrologic and Mn-Cr isotopic study of carbonates in the paired CM1 chondrites, ALH 84049 and ALH 84051, in an effort to understand the origin and chronology of formation of carbonates in the most heavily altered CM chondrites. Dolomite is strongly compositionally zoned (Ca, Mg, Fe, Mn), indicating very heterogeneous formation conditions, yet all carbonate Mn-Cr analyses form individual isochrons. In this study, I also analyzed the Mn-Cr isotope systematics of the CR1 chondrite GRO 95577 and determined that siderite is the youngest secondary mineral yet observed in carbonaceous chondrites. This has implications for the CR parent body as it either was large enough to retain heat for long periods of time or was heated by impact after most aqueous alteration in carbonaceous chondrites had ceased. This study also presents analyses of carbonates in the same samples (ALH 84049 and GRO 95577) in-situ for their oxygen, and, in ALH 84049, carbon isotope composition to constrain aqueous alteration. The results show that multiple generations of carbonates must have occurred in ALH 84049 from a carbon source with either heterogeneous carbon isotopes or with changing carbon isotope compositions from ongoing methane formation. Furthermore, in GRO 95577, the oxygen isotope values suggest that calcite precipitated before siderite if CR chondrite fluids followed a closed system oxygen isotope evolution path similar to CM chondrites.

  3. Progress in the material development of LiCaAlF sub 6 :Cr sup 3+ laser crystals

    SciTech Connect

    Michelle D. Shinn.; Chase, L.L.; Caird, J.A.; Payne, S.A.; Atherton, L.J.; Kway, W.L.

    1990-03-01

    High Cr{sup 3+} doping levels, up to 8 mole percent, and low losses have been obtained with the tunable solid-state laser material LiCaAlF{sub 6}:Cr{sup 3+} (Cr:LiCAF). Measurements and calculations show that high pumping and extraction efficiencies are possible with the improved material. 13 refs., 4 figs., 1 tab.

  4. Thermodynamics of Nitrogen in Fe-Mn-Al-Si-C Alloy Melts

    NASA Astrophysics Data System (ADS)

    Paek, Min-Kyu; Chatterjee, Saikat; Pak, Jong-Jin; Jung, In-Ho

    2016-04-01

    Thermodynamic behavior of nitrogen in the entire range of the Fe-Mn-Al-Si-C liquid solution was modeled based on the critical evaluation and optimization of all available experimental data. The Gibbs energy of liquid solution was described using the Modified Quasichemical Model (MQM) in the pair approximation, instead of classical Wagner Interaction Parameter Formalism, to consider the strong interactions between species in liquid state. In particular, the dissolution behavior of N and formation of AlN in the entire ternary and higher order liquids were accurately predicted from the MQM only with binary model parameters of N.

  5. Environmental influence on the single-molecule magnet behavior of [Mn(III)6Cr(III)]3+: molecular symmetry versus solid-state effects.

    PubMed

    Hoeke, Veronika; Heidemeier, Maik; Krickemeyer, Erich; Stammler, Anja; Bögge, Hartmut; Schnack, Jürgen; Postnikov, Andrei; Glaser, Thorsten

    2012-10-15

    The structural, spectroscopic, and magnetic properties of a series of [Mn(III)(6)Cr(III)](3+) (= [{(talen(t-Bu(2)))Mn(III)(3)}(2){Cr(III)(CN)(6)}](3+)) compounds have been investigated by single-crystal X-ray diffraction (XRD), Fourier transform infrared (FT-IR) and electronic absorption spectroscopy, elemental analysis, electro spray ionization-mass spectrometry (ESI-MS) and matrix-assisted laser desorption ionization-mass spectrometry (MALDI-MS), cyclic voltammetry, AC and DC magnetic measurements, as well as theoretical analysis. The crystal structures obtained with [Cr(III)(CN)(6)](3-) as a counterion exhibit (quasi-)one-dimensional (1D) chains formed by hydrogen-bonded (1) or covalently linked (2) trications and trianions. The rod-shaped anion lactate enforces a rod packing of the [Mn(III)(6)Cr(III)](3+) complexes in the highly symmetric space group R3[overline] (3) with a collinear arrangement of the molecular S(6) axes. Incorporation of the spherical anion BPh(4)(-) leads to less-symmetric crystal structures (4-6) with noncollinear orientations of the [Mn(III)(6)Cr(III)](3+) complexes, as evidenced by the angle between the approximate molecular C(3) axes taking no specific values in the range of 2°-69°. AC magnetic measurements on freshly isolated crystals (1a and 3a-6a), air-dried crystals (3b-6b), and vacuum-dried powder samples (3c-6c) indicate single-molecule magnet (SMM) behavior for all samples with U(eff) values up to 28 K. The DC magnetic data are analyzed by a full-matrix diagonalization of the appropriate spin-Hamiltonian including isotropic exchange, zero-field splitting, and Zeeman interaction, taking into account the relative orientation of the D-tensors. Simulations for 3a-6a and 3c-6c indicate a weak antiferromagnetic exchange between the Mn(III) ions in the trinuclear subunits (J(Mn-Mn) = -0.70 to -0.85 cm(-1), Ĥ(ex) = -2∑(iCr-C≡N-Mn pathway

  6. Microstructural observations in rapidly-solidified and heat-treated Ni3Al-Cr alloys

    NASA Technical Reports Server (NTRS)

    Carro, G.; Flanagan, W. F.

    1992-01-01

    The microstructural development following heat treatments of several rapidly-solidified Ni3Al-Cr and Ni3Al-Cr-B alloys is presented. Depending on composition, the as-solidified samples were either 100 percent gamma-prime phase - in the form of fine antiphase domains (APD) - or a mixture of gamma-prime (APDs) and beta phases. Upon annealing, the as-solidified microstructures transform to either APD-free gamma-prime or mixtures of gamma and gamma-prime phases. For those compositions where the quenched microstructures were 100 percent gamma-prime it was observed that APD coarsening followed conventional grain-growth kinetics, but when gamma phase precipitated on the APD boundaries the rate constant changed abruptly while the time exponent remained unaffected. It was also found that alloys containing critical amounts of chromium and boron are susceptible to precipitation of the boride Cr5B3.

  7. The effect of heat treatments on the microstructure and properties of FeAl+Cr

    SciTech Connect

    Munroe, P.R.; Kong, C.H.

    1997-12-31

    Microstructural studies were performed on an alloy of composition Fe{sub 45}Cr{sub 5}Al{sub 50} heat treated at 950 C and oil-quenched and then given isothermal annealing treatments for times up to 200 hours at either 400 C or 500 C. The observed microstructures were correlated with variations in hardness during isothermal annealing. It was deduced that the thermal vacancies retained following the initial heat treatment are removed relatively rapidly from the lattice, which leads to an initial drop in hardness. However, during prolonged annealing, the coarsening of both FeAl{sub 2} particles and a disordered {alpha}(Fe,Cr) phase leads to further softening. It was also deduced that the chromium atoms, which remain in solution, are effective solute strengtheners. The {alpha}(Fe,Cr) phase, which is coherent with the B2 matrix, appears to coarsen by a ledge growth mechanism.

  8. Photoluminescence of the Cr 3+ ions in α-ZnAl 2S 4:Cr single crystals

    NASA Astrophysics Data System (ADS)

    Broussell, Isabelle; Fortin, Emery; Kulyuk, Leonid; Popov, Sergei

    1996-09-01

    Photoluminescence measurements have been performed on chromium doped α-ZnAl 2S 4 spinel-type crystals in the temperature range 2-540 K. a single configuration coordinate diagram for the Cr 3+ ions in the α-ZnAl 2S 4 host is constructed to interpret the absorption and emission spectra and to allow a determination of the energy gaps between the 2E g - 2T 1g and 2E g - 4T 2g states. A fit of the measured temperature dependence of the luminescence decay, using a simplified four level model gave the lifetimes of the 2Eg, 2T1 g and 4T2 g excited levels and confirmed the gap values obtained from steady state measurements.

  9. The oxidation behavior of Ni-Cr-Al-2ThO2 alloys at 1093 and 1204 C.

    NASA Technical Reports Server (NTRS)

    Seltzer, M. S.; Wilcox, B. A.; Stringer, J.

    1972-01-01

    A pack diffusion process has been developed which permits the introduction of nearly 6 wt % Al into solid solution in the near surface region of TDNiCr (Ni-20 wt % Cr-2 vol % ThO2) and Ni-20Cr. Alumina scales, adherent under cyclic heating and cooling conditions, were produced on TDNiCr-5.86Al upon exposure to an environment of 1330 N/sq m (10 torr) or 101,000 N/sq m (760 torr) air at temperatures of 1093 and 1204 C. While the same oxidation kinetics were observed in isothermal tests for Ni-14.6Cr-5.86Al as were obtained for the TDNiCr-5.86Al, the dispersion-strengthened alloy exhibited superior oxide scale adhesion during cyclic testing. At 1204 C, continuous weight gains were observed under all test conditions for TDNiCr-5.86Al, in contrast to the weight loss with time which occurred several hours after exposure of TDNiCr to an oxidizing environment. TDNiCr with an initial aluminum surface concentration of 4.95 wt % has nearly comparable oxidation resistance to the TDNiCr-5.86Al alloy.

  10. Formation of (Cr, Al)UO4 from doped UO2 and its influence on partition of soluble fission products

    NASA Astrophysics Data System (ADS)

    Cooper, M. W. D.; Gregg, D. J.; Zhang, Y.; Thorogood, G. J.; Lumpkin, G. R.; Grimes, R. W.; Middleburgh, S. C.

    2013-11-01

    CrUO4 and (Cr, Al)UO4 have been fabricated by a sol-gel method, studied using diffraction techniques and modelled using empirical pair potentials. Cr2O3 was predicted to preferentially form CrUO4 over entering solution into hyper-stoichiometric UO2+x by atomic scale simulation. Further, it was predicted that the formation of CrUO4 can proceed by removing excess oxygen from the UO2 lattice. Attempts to synthesise AlUO4 failed, instead forming U3O8 and Al2O3. X-ray diffraction confirmed the structure of CrUO4 and identifies the existence of a (Cr, Al)UO4 phase for the first time (with a maximum Al to Cr mole ratio of 1:3). Simulation was subsequently used to predict the partition energies for the removal of fission products or fuel additives from hyper-stoichiometric UO2+x and their incorporation into the secondary phase. The partition energies are consistent only with smaller cations (e.g. Zr4+, Mo4+ and Fe3+) residing in CrUO4, while all divalent cations are predicted to remain in UO2+x. Additions of Al had little effect on partition behaviour. The reduction of UO2+x due to the formation of CrUO4 has important implications for the solution limits of other fission products as many species are less soluble in UO2 than UO2+x.

  11. Characterization of La2/3Ca1/3xMnO3 with Low Doping of Fe and Cr (abstract)

    NASA Astrophysics Data System (ADS)

    Giratá, D.; Quintero, D. L.; Arnache, O.; Hoffmann, A.

    2009-04-01

    We have characterized magnetization, transport, and structure of La2/3Ca1/3MnO3 thin films and bulk powder samples undoped and with low doping of 57Fe (1% and 3%) and Cr (6%, 7%, and 8%). The powder samples were synthesized by solid-state reaction and thin films grown on (100)-SrTiO3 STO, and (100)-LaAlO3 LAO single-crystal substrates by high O2 pressure (500 mTorr) using dc magnetron sputtering. We found changes in the values of the magnetoresistance and metal-insulator transition temperatures, as well as the magnetization and Curie temperatures. These behaviors are dependent of the composition of the samples. However, we observed from the hysteresis loops that the coercitive field did not change significantly with Cr or Fe addition at different temperatures. Doping decreased the double exchange and the ferromagnetic order, possibly due to the competing influences from the strain relaxation.

  12. Low-temperature structure of ξ'-Al-Pd-Mn optimized by ab initio methods

    NASA Astrophysics Data System (ADS)

    Frigan, Benjamin; Santana, Alejandro; Engel, Michael; Schopf, Daniel; Trebin, Hans-Rainer; Mihalkovič, Marek

    2011-11-01

    We have studied and resolved occupancy correlations in the existing average structure model of the complex metallic alloy ξ'-Al-Pd-Mn [Boudard , Philos. Mag. APMAADG0141-861010.1080/01418619608242169 74, 939 (1996)], which has approximately 320 atoms in the unit cell and many fractionally occupied sites. Model variants were constructed systematically in a tiling-decoration approach and subjected to simulated annealing by use of both density functional theory and molecular dynamics with empirical potentials. To obtain a measure for thermodynamic stability, we reproduce the Al-Pd-Mn phase diagram at T=0 K, and derive an enthalpy of formation for each structure. Our optimal structure resolves a cloud of fractionally occupied sites in pseudo-Mackay clusters. In particular, we demonstrate the presence of rotational degrees of freedom of an Al9 inner shell, which is caged within two icosahedrally symmetric outer shells Al30 and Pd12. Outside these clusters, the chemical ordering on a chain of three nearby sites surprisingly breaks the inversion symmetry of the surrounding structure, and couples to an Al/vacancy site nearby. Our refined tiling-decoration model applies to any structure within the ɛ-phases family, including the metastable decagonal quasicrystalline phase.

  13. Thermal stability of TiAlN/CrN multilayer coatings studied by atom probe tomography.

    PubMed

    Choi, Pyuck-Pa; Povstugar, Ivan; Ahn, Jae-Pyeong; Kostka, Aleksander; Raabe, Dierk

    2011-05-01

    This study is about the microstructural evolution of TiAlN/CrN multilayers (with a Ti:Al ratio of 0.75:0.25 and average bilayer period of 9 nm) upon thermal treatment. Pulsed laser atom probe analyses were performed in conjunction with transmission electron microscopy and X-ray diffraction. The layers are found to be thermally stable up to 600 °C. At 700 °C TiAlN layers begin to decompose into Ti- and Al-rich nitride layers in the out-of-plane direction. Further increase in temperature to 1000 °C leads to a strong decomposition of the multilayer structure as well as grain coarsening. Layer dissolution and grain coarsening appear to begin at the surface. Domains of AlN and TiCrN larger than 100 nm are found, together with smaller nano-sized AlN precipitates within the TiCrN matrix. Fe and V impurities are detected in the multilayers as well, which diffuse from the steel substrate into the coating along columnar grain boundaries. PMID:21146308

  14. Solute transport during the cyclic oxidation of Ni-Cr-Al alloys. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Nesbitt, J. A.

    1982-01-01

    Important requirements for protective coatings of Ni-Cr-Al alloys for gas turbine superalloys are resistance to oxidation accompanied by thermal cycling, resistance to thermal fatigue cracking. The resistance to oxidation accompanied by thermal cycling is discussed. The resistance to thermal fatigue cracking is also considered.

  15. Understanding phase stability of Al-Co-Cr-Fe-Ni high entropy alloys

    DOE PAGESBeta

    Zhang, Chuan; Zhang, Fan; Diao, Haoyan; Gao, Michael C.; Tang, Zhi; Poplawsky, Jonathan D.; Liaw, Peter K.

    2016-07-19

    The concept of high entropy alloy (HEA) opens a vast unexplored composition range for alloy design. As a well-studied system, Al-Co-Cr-Fe-Ni has attracted tremendous amount of attention to develop new-generation low-density structural materials for automobile and aerospace applications. In spite of intensive investigations in the past few years, the phase stability within this HEA system is still poorly understood and needs to be clarified, which poses obstacles to the discovery of promising Al-Co-Cr-Fe-Ni HEAs. In the present work, the CALPHAD approach is employed to understand the phase stability and explore the phase transformation within the Al-Co-Cr-Fe-Ni system. As a result,more » the phase-stability mapping coupled with density contours is then constructed within the composition - temperature space, which provides useful guidelines for the design of low-density Al-Co-Cr-Fe-Ni HEAs with desirable properties.« less

  16. The effect of Al and Cr additions on pack cementation zinc coatings

    NASA Astrophysics Data System (ADS)

    Chaliampalias, D.; Papazoglou, M.; Tsipas, S.; Pavlidou, E.; Skolianos, S.; Stergioudis, G.; Vourlias, G.

    2010-03-01

    Zinc is widely used as a protective coating material due to its corrosion resistant properties. The structure and oxidation resistance of Al and Cr mixed zinc coatings, deposited by pack cementation process, is thoroughly examined in this work. The morphology and chemical composition of the as-deposited and oxidized samples was accomplished by electron microscopy while the phase identification was performed by XRD diffraction analysis. The experimental results showed that the addition of aluminum or chromium in the pack mixture forms only Al and Cr rich phases on the surface of the specimens without affecting significantly the phase composition of the rest zinc coatings. In the case of Zn-Al coatings, the overlying layer contains high concentrations of Al together with lower amounts of zinc and iron and in Zn-Cr coatings this layer contains Cr, Fe and Zn atoms and has much smaller thickness. The presence of these additional layers promotes significantly the oxidation resistance of the zinc pack coatings and they preserve most of their initial thickness and chemical content when exposed to an aggressive environment while their oxidation mass gain was measured at low levels during the oxidation tests.

  17. Investigation of heat-resistant layered coating of Al-Cr-Ni

    NASA Astrophysics Data System (ADS)

    Shmorgun, V. G.; Trykov, Y. P.; Bogdanov, A. I.; Taube, A. O.

    2016-02-01

    The paper shows the transformation of the structure and phase composition of the layered coating system Al-Cr-Ni, obtained by the heat treatment of multilayered composite H20N80+AD1, welded by explosion, in the time range 1-300 hours. The cyclic heat resistance of the coating at 1150 ° C is studied.

  18. Gain measurements and average power capabilities of Cr(3+): LiSrAlF6

    NASA Astrophysics Data System (ADS)

    Hanson, F.; Bendall, C.; Poirier, P.

    1993-09-01

    Long wavelength operation of Cr:LiSrAlF6 is reported. The problem of thermal fracture effectively limits flash-lamp-pumped rod geometries to lower repetition rates. Thin face-pumped slabs allow higher average power capability, but peak gain could be limited by upconversion losses.

  19. Ion irradiation testing and characterization of FeCrAl candidate alloys

    SciTech Connect

    Anderoglu, Osman; Aydogan, Eda; Maloy, Stuart Andrew; Wang, Yongqiang

    2014-10-29

    The Fuel Cycle Research and Development program’s Advanced Fuels Campaign has initiated a multifold effort aimed at facilitating development of accident tolerant fuels. This effort involves development of fuel cladding materials that will be resistant to oxidizing environments for extended period of time such as loss of coolant accident. Ferritic FeCrAl alloys are among the promising candidates due to formation of a stable Al₂O₃ oxide scale. In addition to being oxidation resistant, these promising alloys need to be radiation tolerant under LWR conditions (maximum dose of 10-15 dpa at 250 – 350°C). Thus, in addition to a number of commercially available alloys, nuclear grade FeCrAl alloys developed at ORNL were tested using high energy proton irradiations and subsequent characterization of irradiation hardening and damage microstructure. This report summarizes ion irradiation testing and characterization of three nuclear grade FeCrAl cladding materials developed at ORNL and four commercially available Kanthal series FeCrAl alloys in FY14 toward satisfying FCRD campaign goals.

  20. Study of the effects of implantation on the high Fe-Ni-Cr and Ni-Cr-Al alloys

    NASA Technical Reports Server (NTRS)

    Ribarsky, M. W.

    1985-01-01

    A theoretical study of the effects of implantation on the corrosion resistance of Fe-Ni-Cr and Ni-Cr-Al alloys was undertaken. The purpose was to elucidate the process by which corrosion scales form on alloy surfaces. The experiments dealt with Ni implanted with Al, exposed to S at high temperatures, and then analyzed using scanning electron microscopy, scanning Auger spectroscopy and X-ray fluorescence spectroscopy. Pair bonding and tight-binding models were developed to study the compositions of the alloys and as a result, a new surface ordering effect was found which may exist in certain real alloys. With these models, the behavior of alloy constituents in the presence of surface concentrations of O or S was also studied. Improvements of the models to take into account the important effects of long- and short-range ordering were considered. The diffusion kinetics of implant profiles at various temperatures were investigated, and it was found that significant non-equilibrium changes in the profiles can take place which may affect the implants' performance in the presence of surface contaminants.

  1. Nano-twin Mediated Plasticity in Carbon-containing FeNiCoCrMn High Entropy Alloys

    SciTech Connect

    Wu, Zhenggang; Bei, Hongbin; Parish, Chad M

    2015-06-14

    Equiatomic FeNiCoCrMn alloy has been reported to exhibit promising strength and ductility at cryogenic temperature and deformation mediated by nano-twining appeared to be one of the main reasons. We use the FeNiCoCrMn alloy as a base alloy to seek further improvement of its mechanical properties by alloying additional elements, i.e., interstitial carbon. Moreover, the effects of carbon on microstructures, mechanical properties and twinning activities were investigated in two different temperatures (77 and 293 K). With addition of 0.5 at% C, the high entropy alloy still remains entirely single phase face-centered cubic (FCC) crystal structure. We found that these materials can be cold rolled and recrystallized to produce a microstructure with equiaxed grains. Both strain hardening rate and strength are enhanced while high uniform elongations to fracture (~70% at 77 K and ~40% at 293 K) are still maintained. The increased strain hardening and strength could be caused by the promptness of deformation twinning in C-containing high entropy alloys.

  2. Electronic, optical and thermal properties of TiCr2 and TiMn2 by ab initio simulations

    NASA Astrophysics Data System (ADS)

    Ali, M. S.; Roknuzzaman, M.; Parvin, R.; Islam, A. K. M. A.; Ostrikov, K.

    2015-10-01

    A theoretical study of TiX2 (X = Cr, Mn) with C14 Laves phase compounds has been performed by using the first-principles pseudopotential plane-wave method within the generalized gradient approximation (GGA). The electronic properties (Fermi surface and charge density) have been calculated and analyzed. The optical characteristics (dielectric functions, absorption spectrum, conductivity, energy-loss spectrum and reflectivity) are calculated and discussed. The calculated large positive static dielectric constant indicates good dielectric properties. The reflectivity of TiX2 (X = Cr, Mn) is high in the IR-Visible-UV region up to ˜13 eV showing promise as a good solar heating barrier material. The temperature and pressure dependence of bulk modulus, Debye temperature, specific heats and thermal expansion coefficient are obtained for T = 1200 K and P = 50 GPa through quasi-harmonic Debye model with phononic effects. Fermi surface, optical and thermodynamic properties are very important for practical applications of the materials in optical and other devices.

  3. Nano-twin Mediated Plasticity in Carbon-containing FeNiCoCrMn High Entropy Alloys

    DOE PAGESBeta

    Wu, Zhenggang; Bei, Hongbin; Parish, Chad M

    2015-06-14

    Equiatomic FeNiCoCrMn alloy has been reported to exhibit promising strength and ductility at cryogenic temperature and deformation mediated by nano-twining appeared to be one of the main reasons. We use the FeNiCoCrMn alloy as a base alloy to seek further improvement of its mechanical properties by alloying additional elements, i.e., interstitial carbon. Moreover, the effects of carbon on microstructures, mechanical properties and twinning activities were investigated in two different temperatures (77 and 293 K). With addition of 0.5 at% C, the high entropy alloy still remains entirely single phase face-centered cubic (FCC) crystal structure. We found that these materials canmore » be cold rolled and recrystallized to produce a microstructure with equiaxed grains. Both strain hardening rate and strength are enhanced while high uniform elongations to fracture (~70% at 77 K and ~40% at 293 K) are still maintained. The increased strain hardening and strength could be caused by the promptness of deformation twinning in C-containing high entropy alloys.« less

  4. Influence of Plasma Remelting on the Microstructure and Cavitation Resistance of Arc-Sprayed Fe-Mn-Cr-Si Alloy

    NASA Astrophysics Data System (ADS)

    Pukasiewicz, A. G. M.; Alcover, P. R. C.; Capra, A. R.; Paredes, R. S. C.

    2014-01-01

    Surface remelting is an important technique for modifying the microstructure of thermally sprayed coatings as it reduces the porosity and promotes a metallurgical bond between substrate and coating. Many studies have been carried out in the field of materials selection and surface engineering in an attempt to reduce cavitation damage. In this work, an Fe-Mn-Cr-Si alloy was deposited by arc spraying and then remelted by a plasma-transferred arc process. The base metal was a soft martensitic stainless steel. The influence of remelting current on coating and base metal microstructure and cavitation resistance was studied. The use of a lower mean current and a pulsed arc reduced the thickness of the heat-affected zone. In specimens remelted with constant arc current, dendrites were aligned parallel to the path followed by the plasma torch; while in those remelted with a pulsed plasma arc, the alignment of the microstructure was disrupted. The use of a higher peak current in pulsed-current plasma transferred arc remelting reduced mass loss due to cavitation. Fe-Mn-Cr-Si coatings exhibited cavitation-induced hardening, with martensite formation during cavitation tests. This transformation helps to increase the cavitation resistance of the remelted coating compared with the soft martensitic stainless steel base metal.

  5. Thermodynamic Stability of Transition-Metal-Substituted LiMn2-x Mx O4 (M=Cr, Fe, Co, and Ni) Spinels.

    PubMed

    Lai, Chenying; Chen, Jiewei; Knight, James C; Manthiram, Arumugam; Navrotsky, Alexandra

    2016-07-01

    The formation enthalpies from binary oxides of LiMn2 O4 , LiMn2-x Crx O4 (x=0.25, 0.5, 0.75 and 1), LiMn2-x Fex O4 (x=0.25 and 0.5), LiMn2-x Cox O4 (x=0.25, 0.5, and 0.75) and LiMn1.75 Ni0.25 O4 at 25 °C were measured by high temperature oxide melt solution calorimetry and were found to be strongly exothermic. Increasing the Cr, Co, and Ni content leads to more thermodynamically stable spinels, but increasing the Fe content does not significantly affect the stability. The formation enthalpies from oxides of the fully substituted spinels, LiMnMO4 (M=Cr, Fe and Co), become more exothermic (implying increasing stability) with decreasing ionic radius of the metal and lattice parameters of the spinel. The trend in enthalpy versus metal content is roughly linear, suggesting a close-to-zero heat of mixing in LiMn2 O4 -LiMnMO4 solid solutions. These data confirm that transition-metal doping is beneficial for stabilizing these potential cathode materials for lithium-ion batteries. PMID:27017448

  6. IBA analysis and corrosion resistance of TiAlPtN/TiAlN/TiAl multilayer films deposited over a CoCrMo using magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Canto, C. E.; Andrade, E.; de Lucio, O.; Cruz, J.; Solís, C.; Rocha, M. F.; Alemón, B.; Flores, M.; Huegel, J. C.

    2016-03-01

    The corrosion resistance and the elemental profile of multilayer coatings of TiAlPtN/TiAlN/TiAl synthesized by Physical Vapor Deposition (PVD) reactive magnetron sputtering over a CoCrMo alloy substrate in 10 periods of 30 min each were analyzed and compared to those of the substrate alone and to that of a TiAlPtN single layer coating of the same thickness. The objective of the present work was to create multilayers with different amounts of Pt to enhance the corrosion resistance of a biomedical alloy of CoCrMo. Corrosion tests were performed using Simulated Body Fluid (SBF) using potentiodynamic polarization tests at typical body temperature. The elemental composition and thickness of the coatings were evaluated with the combination of two ion beam analysis (IBA) techniques: a Rutherford Backscattering Spectroscopy (RBS) with alpha beam and a Nuclear Reaction Analysis with a deuteron beam.

  7. Phase-Specific Elastic/Plastic Interface Interactions in Layered Cr-NiAl Structures

    SciTech Connect

    Barabash, Rozaliya; Liu, W.; Tischler, Jonathan Zachary; Bei, Hongbin; Budai, John D

    2012-01-01

    The depth-dependent, as-grown and deformation-induced strain and dislocations partitioned through the interfaces in a two-phase layered NiAl-Cr(Mo) structure are directly measured at the mesoscale using 3-D X-ray microdiffraction. It is demonstrated that in the as-grown, undeformed state, neighboring submicron Cr solid solution and NiAl eutectic lamellae (doped with {approx}3% Mo) form a heterointerface with 180{sup o} rotation around a <1 1 2> pole. It is shown that the mechanical response to the indentation of a layered composite with alternating Cr(Mo)-NiAl lamellae is distinct from the response of single-phase materials. In the center of the indent, after the load is released, the NiAl lamellae are under compressive forward stresses (with the same sign as the indentation-induced compression) while Cr solid solution lamellae are under tensile back stresses (with opposite sign from the indentation load). The depth-dependent alternation of compressive/tensile residual strains in the neighboring Cr solid solution and NiAl lamellae is understood in the framework of the Mughrabi's composite model considering two types of structure elements: harder and softer regions. Under indentation, both kinds of lamellae are assumed to deform compatibly. After the load is released, residual forward stresses are formed in the harder lamellae, and back stresses are formed in the mechanically softer lamellae. Line-broadening analysis of the intensity distribution along the diffraction vector reveals a 15-times increase in dislocation density in the near-surface zone in the center of the indent. Such a large increase is typical for severe deformation.

  8. Microstructures, mechanical properties, and electrical resistivity of rapidly quenched Fe-Cr-Al alloys

    NASA Astrophysics Data System (ADS)

    Naohara, T.; Inoue, A.; Minemura, T.; Masumoto, T.; Kumada, K.

    1982-03-01

    By the rapid quenching technique, ductile supersaturated ferrite solid solution with high hardness and strength as well as unusual electrical properties has been found in Fe-Cr-Al ternary system. This formation range is limited to less than about 35 at. pct Cr and 23 at. pct Al. The ferrite phase has fine grains of about 10 μm in diameter. Their hardness, yield strength, and tensile fracture strength increase with increase in the amounts of chromium and aluminum, and the highest values reach about 290 DPN, 720 MPa, and 740 MPa. These alloys are so ductile that no cracks are observed even after closely contacted bending test. The good strength and ductility remain almost unchanged on tempering for one hour until heated to about 923 K where a large amount of Cr2Al compound begins to precipitate preferentially along the grain boundaries of the ferrite phase. The room-temperature resistivity increases with increasing chromium and aluminum contents and reaches as high as 1.86 μ Ώ m for Fe50Cr30Al20 alloy. Also, the temperature coefficient of resistivity in the temperature range between room temperature and 773 K decreases with increasing chromium and aluminum contents and becomes zero in the vicinity of 20 to 30 at. pct Cr and 15 at. pct Al. Thus, the present alloys may be attractive as fine gauge high-resistance and/or standard-resistance wires and plates because of the unusual electrical properties combined with high strength and good ductility.

  9. Advanced ODS FeCrAl alloys for accident-tolerant fuel cladding

    SciTech Connect

    Dryepondt, Sebastien N; Unocic, Kinga A; Hoelzer, David T; Pint, Bruce A

    2014-09-01

    ODS FeCrAl alloys are being developed with optimum composition and properties for accident tolerant fuel cladding. Two oxide dispersion strengthened (ODS) Fe-15Cr-5Al+Y2O3 alloys were fabricated by ball milling and extrusion of gas atomized metallic powder mixed with Y2O3 powder. To assess the impact of Mo on the alloy mechanical properties, one alloy contained 1%Mo. The hardness and tensile properties of the two alloys were close and higher than the values reported for fine grain PM2000 alloy. This is likely due to the combination of a very fine grain structure and the presence of nano oxide precipitates. The nano oxide dispersion was however not sufficient to prevent grain boundary sliding at 800 C and the creep properties of the alloys were similar or only slightly superior to fine grain PM2000 alloy. Both alloys formed a protective alumina scale at 1200 C in air and steam and the mass gain curves were similar to curves generated with 12Cr-5Al+Y2O3 (+Hf or Zr) ODS alloys fabricated for a different project. To estimate the maximum temperature limit of use for the two alloys in steam, ramp tests at a rate of 5 C/min were carried out in steam. Like other ODS alloys, the two alloys showed a significant increase of the mas gains at T~ 1380 C compared with ~1480 C for wrought alloys of similar composition. The beneficial effect of Yttrium for wrought FeCrAl does not seem effective for most ODS FeCrAl alloys. Characterization of the hardness of annealed specimens revealed that the microstructure of the two alloys was not stable above 1000 C. Concurrent radiation results suggested that Cr levels <15wt% are desirable and the creep and oxidation results from the 12Cr ODS alloys indicate that a lower Cr, high strength ODS alloy with a higher maximum use temperature could be achieved.

  10. High-Temperature Thermometer Using Cr-Doped GdAlO3 Broadband Luminescence

    NASA Technical Reports Server (NTRS)

    Eldridge, Jeffrey; Chambers, Matthew

    2011-01-01

    A new concept has been developed for a high-temperature luminescence-based optical thermometer that both shows the desired temperature sensitivity in the upper temperature range of present state-of-the-art luminescence thermometers (above 1,300 C), while maintaining substantial stronger luminescence signal intensity that will allow these optical thermometers to operate in the presence of the high thermal background radiation typical of industrial applications. This objective is attained by using a Cr-doped GdAlO3 (Cr:GdAlO3) sensor with an orthorhombic perovskite structure, resulting in broadband luminescence that remains strong at high temperature due to the favorable electron energy level spacing of Cr:GdAlO3. The Cr:GdAlO3 temperature (and pressure) sensor can be incorporated into, or applied onto, a component s surface when a non-contact surface temperature measurement is desired, or alternatively, the temperature sensor can be attached to the end of a fiber-optic probe that can then be positioned at the location where the temperature measurement is desired. In the case of the fiber-optic probe, both the pulsed excitation and the luminescence emission travel through the fiber-optic light guide. In either case, a pulsed light source provides excitation of the luminescence, and the broadband luminescence emission is collected. Real-time temperature measurements are obtain ed using a least-squares fitting algorithm that determines the luminescence decay time, which has a known temperature dependence established by calibration. Due to the broad absorption and emission bands for Cr:GdAlO3, there is considerable flexibility in the choice of excitation wavelength and emission wavelength detection bands. The strategic choice of the GdAlO3 host is based on its high crystal field, phase stability, and distorted symmetry at the Cr3+ occupation sites. The use of the broadband emission for temperature sensing at high temperatures is a key feature of the invention and is

  11. Fretting corrosion of CoCrMo and Ti6Al4V interfaces.

    PubMed

    Swaminathan, Viswanathan; Gilbert, Jeremy L

    2012-08-01

    Mechanically assisted corrosion (fretting corrosion, tribocorrosion etc.,) of metallic biomaterials is a primary concern for numerous implant applications, particularly in the performance of highly-loaded medical devices. While the basic underlying concepts of fretting corrosion or tribocorrosion and fretting crevice corrosion are well known, there remains a need to develop an integrated systematic method for the analysis of fretting corrosion involving metal-on-metal contacts. Such a method can provide detailed and quantitative information on the processes present and explore variations in surfaces, alloys, voltages, loadings, motion and solution conditions. This study reports on development of a fretting corrosion test system and presents elements of an in-depth theoretical fretting corrosion model that incorporates both the mechanical and the electrochemical aspects of fretting corrosion. To demonstrate the capabilities of the new system and validate the proposed model, experiments were performed to understand the effect of applied normal load on fretting corrosion performance of Ti6Al4V/Ti6Al4V, CoCrMo/Ti6Al4V, and CoCrMo/CoCrMo material couples under potentiostatic conditions with a fixed starting surface roughness. The results of this study show that fretting corrosion is affected by material couples, normal load and the motion conditions at the interface. In particular, fretting currents and coefficient of friction (COF) vary with load and are higher for Ti6Al4V/Ti6Al4V couple reaching 3 mA/cm(2) and 0.63 at about 73 MPa nominal contact stress, respectively. Ti6Al4V coupled with CoCrMo displayed lower currents (0.6 mA/cm(2)) and COF (0.3), and the fretting corrosion behavior was comparable to CoCrMo/CoCrMo couple (1.2 mA/cm(2) and 0.3, respectively). Information on the mechanical energy dissipated at the interface, the sticking behavior, and the load dependence of the inter-asperity distance calculated using the model elucidated the influence of

  12. Serration Behavior and Pop-in Phenomena in AlxCrCuFeMnNi High Entropy Alloys

    NASA Astrophysics Data System (ADS)

    Diao, Haoyan; Xie, Xie; Chen, Shuying; Wang, Gongyao; Yang, Fuqian; Dahmen, Karin; Liaw, Peter

    2015-03-01

    Recently, high-entropy alloys (HEAs), based on achieving a high configuration entropy of mixing among alloying elements, have been developed. Many of these alloys contain expensive elements, such as Co. Substituting these elements for less expensive elements, such as Mn, without compromising the mechanical performance is crucial to make HEAs commercially viable. The AlxCrCuFeMnNi (x = 0.1, 0.3, and 0.8) system is one such alloy that displays encouraging mechanical results in both compression and nanoindentation experiments. Discrete, jerky stress-drop bursts (serrations) are even found at room temperature. The mean-field-interaction model predicts the scaling behavior of the distribution, D(S), of avalanche sizes in the experiments. D(S) follows a power law multiplied by an exponentially-decaying scaling function. The size of the largest observed avalanche depends on experimental parameters, such as aluminum content, strain rate, or temperature. In nanoindentation, a strain burst is manifested by a sudden displacement excursion or `pop-in', following the initial elastic Hertzian contact. The pop-in phenomena becomes more frequent and regular, as the indentation load is greater than 35 mN. A quantitative theory for the serration behavior and pop-in phenomena is a critical issue for understanding the deformation characteristics of HEAs. This work was supported by the Department of Energy No. DE-FE-0008855 and DE-FE-0011194.

  13. Oxide scales formed on Fe-Cr-Al-based model alloys exposed to oxygen containing molten lead

    NASA Astrophysics Data System (ADS)

    Weisenburger, A.; Jianu, A.; Doyle, S.; Bruns, M.; Fetzer, R.; Heinzel, A.; DelGiacco, M.; An, W.; Müller, G.

    2013-06-01

    Based on the state of the art oxide maps concerning oxidation behavior of Fe-Cr-Al model alloys at 800 and 1000 °C in oxygen atmosphere, ten compositions, belonging to this alloy system, were designed in order to tap the borders of the alumina stability domain, during their exposure to oxygen (10-6 wt.%) containing lead, at 400, 500 and 600 °C. Eight alloys, Fe-6Cr-6Al, Fe-8Cr-6Al, Fe-10Cr-5Al, Fe-14Cr-4Al, Fe-16Cr-4Al, Fe-6Cr-8Al, Fe-10Cr-7Al and Fe-12Cr-5Al, were found to be protected against corrosion in oxygen containing lead, either by a duplex layer (Fe3O4 + (Fe1-x-yCrxAly)3O4) or by (Fe1-x-yCrxAly)3O4, depending on the temperature at which they were exposed. Two alloys namely Fe-12Cr-7Al and Fe-16Cr-6Al were found to form transient aluminas, κ-Al2O3 (at 400 and 500 °C) and θ-Al2O3 (at 600 °C), as protective oxide scale against corrosion in oxygen containing lead. An oxide map illustrating the stability domain of alumina, grown on Fe-Cr-Al alloys when exposed to molten, oxygen containing lead, was drawn. The map includes also additional points, extracted from literature and corresponding to alumina forming alloys, when exposed to HLMs, which fit very well with our findings. Chromium and aluminium contents of 12.5-17 wt.% and 6-7.5 wt.%, respectively, are high enough to obtain thin, stable and protective alumina scales on Fe-Cr-Al-based alloys exposed to oxygen containing lead at 400, 500 and 600 °C. For the temperature range and exposure times used during the current evaluation, the growth rate of the alumina scale was low. No area with detached scale was observed and no trace of α-Al2O3 was detected.

  14. Deformation and fracture of a directionally solidified NiAl-28Cr-6Mo eutectic alloy

    NASA Technical Reports Server (NTRS)

    Chen, X. F.; Johnson, D. R.; Noebe, R. D.; Oliver, B. F.

    1995-01-01

    A directionally solidified alloy based on the NiAl-(Cr, Mo) eutectic was examined by transmission and scanning electron microscopy to characterize the microstructure and room temperature deformation and fracture behavior. The microstructure consisted of a lamellar morphology with a group of zone axes (111) growth direction for both the NiAl and (Cr, Mo) phases. The interphase boundary between the eutectic phases was semicoherent and composed of a well-defined dislocation network. In addition, a fine array of coherent NiAl precipitates was dispersed throughout the (Cr, Mo) phase. The eutectic morphology was stable at 1300 K with only coarsening of the NiAl precipitates occurring after heat treatment for 1.8 ks (500 h). Fracture of the aligned eutectic is characterized primarily by a crack bridging/renucleation mechanism and is controlled by the strength of the semicoherent interface between the two phases. However, contributions to the toughness of the eutectic may arise from plastic deformation of the NiAl phase and the geometry associated with the fracture surface.

  15. Experimental study and thermodynamic modeling of the Al-Co-Cr-Ni system

    NASA Astrophysics Data System (ADS)

    Gheno, Thomas; Liu, Xuan L.; Lindwall, Greta; Liu, Zi-Kui; Gleeson, Brian

    2015-10-01

    A thermodynamic database for the Al-Co-Cr-Ni system is built via the Calphad method by extrapolating re-assessed ternary subsystems. A minimum number of quaternary parameters are included, which are optimized using experimental phase equilibrium data obtained by electron probe micro-analysis and x-ray diffraction analysis of NiCoCrAlY alloys spanning a wide compositional range, after annealing at 900 °C, 1100 °C and 1200 °C, and water quenching. These temperatures are relevant to oxidation and corrosion resistant MCrAlY coatings, where M corresponds to some combination of nickel and cobalt. Comparisons of calculated and measured phase compositions show excellent agreement for the β-γ equilibrium, and good agreement for three-phase β-γ-σ and β-γ-α equilibria. An extensive comparison with existing Ni-base databases (TCNI6, TTNI8, NIST) is presented in terms of phase compositions.

  16. Environmental Fatigue-Crack Surface Crystallography for Al-Zn-Cu-Mg-Mn/Zr

    NASA Astrophysics Data System (ADS)

    Ro, Yunjo; Agnew, Sean R.; Gangloff, Richard P.

    2008-06-01

    The scanning electron microscope (SEM)-based electron backscattered diffraction (EBSD)/stereology technique quantitatively establishes distributions of the crystallographic characteristics of environmental-fatigue crack features for slightly overaged Al-Zn-Cu-Mg-X (X = Zr or Mn) alloys stressed in the low-growth-rate regime. Results for these homogeneous slip alloys conform to a substantial companion study of planar slip-prone Al-Cu-Mg/Li. Transgranular-crack characteristics are similar for the Mn and Zr variants, independent of grain size and recrystallization. Two morphologies of facetlike features exhibit a wide range of crystallographic orientations, change character at grain boundaries indicating an important role of grain orientation, and form in highly tensile-stressed spatial orientations about a crack tip. Similar characteristics for Al-Zn and Al-Cu suggest a common damage mechanism, speculatively attributed to hydrogen-environment embrittlement by decohesion. Slip-deformation band cracking resulting in facets near {111}, stimulated by H-enhanced localized plasticity, is not a viable mechanism for environmental fatigue. Repetitively stepped facets with surface curvature may involve H-enhanced cleavage along {100} or {110} planes subsequently distorted by plasticity. Broad-flat facets speculatively result from tensile stress-based cracking through dislocation cell structure, evolved by cyclic plasticity and containing trapped H.

  17. Influence of Zr alloying on the mechanical properties, thermal stability and oxidation resistance of Cr-Al-N coatings

    NASA Astrophysics Data System (ADS)

    Li, W. Z.; Chen, Q. Z.; Polcar, T.; Serra, R.; Cavaleiro, A.

    2014-10-01

    Cr-Al-N coatings with Zr alloying (Zr contents from 0 to 29.5 at.%) were deposited by d.c. reactive magnetron sputtering. The chemical composition and the morphology of as-deposited coatings were characterized, and the phase structure, mechanical properties and wear resistance of the coatings before and after thermal annealing were analyzed and evaluated. With the increase of Zr content, both Cr and N contents decrease whereas Al shows a growing trend. Low Zr (<26.9 at.%) coatings are stoichiometric and present a fcc NaCl-type B1 structure with columnar morphology, while high Zr (≥26.9 at.%) coatings are in N deficiency and have low crystallinity degree. The alloying of low contents of Zr improves the coating hardness and H/E ratio; however, for low ordered coatings these properties decrease significantly. After thermal annealing, fcc structure is kept in low Zr films whereas the crystalline degree is improved in the high Zr ones and their mechanical properties were slightly improved. Two coatings were selected for further testing, representatives of low (CrAlZr5N) and high (CrAlZr27N) Zr contents. The onset oxidation temperature is ∼900 °C and 600 °C for CrAlZr5N and CrAlZr27N coatings, respectively. Mainly Cr2O3 is formed on low Zr coatings whereas mixed oxides of ZrO2 and Cr2O3 are detected on CrAlZr27N sample after thermal exposure. In all tribological tests, low Zr coating presents lower wear rate than the CrAlZr27N coating. In general, the addition of very high Zr contents (>20 at.%) with N deficiency markedly weakens the mechanical properties and the oxidation resistance of Cr-Al-Zr-N coatings.

  18. Phase diagram and magnetocaloric effects in Ni{sub 50}Mn{sub 35}(In{sub 1−x}Cr{sub x}){sub 15} and (Mn{sub 1−x}Cr{sub x})NiGe{sub 1.05} alloys

    SciTech Connect

    Quetz, Abdiel Muchharla, Baleeswaraiah; Dubenko, Igor; Talapatra, Saikat; Ali, Naushad; Samanta, Tapas; Stadler, Shane

    2014-05-07

    The magnetocaloric and thermomagnetic properties of Ni{sub 50}Mn{sub 35}(In{sub 1−x}Cr{sub x}){sub 15} and (Mn{sub 1−x}Cr{sub x}) NiGe{sub 1.05} systems for 0 ≤ x ≤ 0.105 and 0 ≤ x ≤ 0.1, respectively, have been studied by x-ray diffraction, differential scanning calorimetry, and magnetization measurements. Partial substitution of Cr for Mn in (Mn{sub 1−x}Cr{sub x})NiGe{sub 1.05} results in a first order magnetostructural transition from a hexagonal paramagnetic to an orthorhombic paramagnetic phase near T{sub M} ∼ 380 K (for x = 0.07). Partial substitution of Cr for In in Ni{sub 50}Mn{sub 35}(In{sub 1−x}Cr{sub x}){sub 15} shifts the magnetostructural transition to a higher temperature (T = T{sub M} ∼ 450 K) for x = 0.1. Large magnetic entropy changes of ΔS = −12 (J/(kgK)) and ΔS = −11 (J/(kgK)), both for a magnetic field change of 5 T, were observed in the vicinity of T{sub M} for (Mn{sub 1−x}Cr{sub x})NiGe{sub 1.05} and Ni{sub 50}Mn{sub 35}(In{sub 1−x}Cr{sub x}){sub 15}, respectively.

  19. Preparation and characterization of α-Al2O3 film by low temperature thermal oxidation of Al8Cr5 coating

    NASA Astrophysics Data System (ADS)

    Zhang, Min; Xu, Bajin; Ling, Guoping

    2015-03-01

    In this paper, α-Al2O3 film was prepared by low temperature thermal oxidation of Al8Cr5 coating. The Al8Cr5 alloy coating was prepared on SUS430 stainless steel through a two-step approach including electrodepositing Cr/Al composite coating and subsequent heat treatment at 740 °C for 16 h. After mechanical polishing removal of voids on the surface, the Al8Cr5 coating was thermal oxidized at 720 °C in argon for 100 h. The samples were characterized by SEM, EDX, XRD, XPS and TEM. XPS detection on the surface of oxidized Al8Cr5 coating showed that the oxide film mainly consisted of Al2O3. TEM characterization of the oxide film showed that it was α-Al2O3 films ca. 110 nm. The formation of α-Al2O3 films at low temperature can be attributed to the formation of Cr2O3 nuclei at the initial stage of oxidation which lowers the nucleation energy barrier of α-Al2O3.

  20. YZ (Y = V, Cr; Z = Al, Ga) under pressure: a DFT study

    NASA Astrophysics Data System (ADS)

    Seema, K.; Kumar, Ranjan

    2014-09-01

    The structural, electronic and magnetic properties of Co-based Heusler compounds Co2YZ (Y = V, Cr; Z = Al, Ga) under pressure are studied using first principles density functional theory. The calculations are performed within generalized gradient approximation. The total magnetic moment decreases slightly on compression. Under application of external pressure, the valence band and conduction band are shifted downward which leads to the modification of electronic structure. There exists an indirect band gap along Г- X for all the alloys studied. Co2CrAl shows half-metallic nature up to 85 GPa. After this pressure transition from true half-metallic behavior to nearly half-metallic behavior is observed and at 90 GPa it shows metallic behavior. Co2CrGa shows nearly half-metallic behavior at ambient pressure, but true half-metallic behavior is observed as pressure is increased to 100 GPa. For Co2VGa, true half-metallic to nearly half-metallic transition is observed at 40 GPa and around 100 GPa, Co2VGa shows metallic behavior. For Co2VAl, true half-metallic behavior is not observed at ambient as well as higher pressures. The half metal-to-metal transition in Co2VAl and Co2CrAl is accompanied by quenching of magnetic moment.

  1. Nanostructured Ternary FeCrAl Oxide Photocathodes for Water Photoelectrolysis.

    PubMed

    Kondofersky, Ilina; Müller, Alexander; Dunn, Halina K; Ivanova, Alesja; Štefanić, Goran; Ehrensperger, Martin; Scheu, Christina; Parkinson, Bruce A; Fattakhova-Rohlfing, Dina; Bein, Thomas

    2016-02-17

    A sol-gel method for the synthesis of semiconducting FeCrAl oxide photocathodes for solar-driven hydrogen production was developed and applied for the production of meso- and macroporous layers with the overall stoichiometry Fe0.84Cr1.0Al0.16O3. Using transmission electron microscopy and energy-dispersive X-ray spectroscopy, phase separation into Fe- and Cr-rich phases was observed for both morphologies. Compared to prior work and to the mesoporous layer, the macroporous FeCrAl oxide photocathode had a significantly enhanced photoelectrolysis performance, even at a very early onset potential of 1.1 V vs RHE. By optimizing the macroporous electrodes, the device reached current densities of up to 0.68 mA cm(-2) at 0.5 V vs RHE under AM 1.5 with an incident photon-to-current efficiency (IPCE) of 28% at 400 nm without the use of catalysts. Based on transient measurements, this performance increase could be attributed to an improved collection efficiency. At a potential of 0.75 V vs RHE, an electron transfer efficiency of 48.5% was determined. PMID:26743183

  2. Magnetic properties of Sm2(Fe0.95M0.05)17Nx (M=Cr and Mn) anisotropic coarse powders with high coercivity

    NASA Astrophysics Data System (ADS)

    Ito, Mikio; Majima, Kazuhiko; Shimuta, Toru; Katsuyama, Shigeru; Nagai, Hiroshi

    2002-09-01

    Sm2(Fe0.95Cr0.05)17Nx and Sm2(Fe0.95Mn0.05)17Nx coarse powders 10-70 mum in size were synthesized by crushing mother alloy ingots into 32-74 mum in particle size and subsequent nitrogenation at 748 K in a flowing mixed gas of 60 vol % H2+40 vol % NH3. The effects of Cr or Mn substitution for Fe on the nitrogenation rate, magnetic properties, and microstructure of the Sm2Fe17Nx hard magnetic material were investigated. Cr and Mn substitution was quite effective for accelerating nitrogenation. When the powders were nitrogenated beyond x=3, amorphous phase formation was observed as the x value increased. The magnetic properties of the nitrogenated powders were significantly improved by Cr and Mn substitution, and these powders also possessed a satisfactory magnetic anisotropy. The maximum coercivity in this study, 0.59 MA/m, was obtained for the Sm2(Fe0.95Mn0.05)17N5.0 powder in spite of its large particle size. The high coercivity of the coarse powders was caused by a cell-like microstructure composed of fine 2-17 crystalline grains 20-30 nm in size surrounded by an amorphous phase.

  3. Electrical transport and magnetic behaviors of La0.67Sr0.33Mn1-xBxO3 (B = Cr, Ru)

    NASA Astrophysics Data System (ADS)

    Acharya, Deepshikha; Bhargav, Abhinav; Tank, Tejas M.; Sanyal, Sankar P.

    2016-05-01

    Polycrystalline samples of La0.67Sr0.33Mn1-xCrxO3 (with x=0, 0.05 and 0.1) and La0.67Sr0.33Mn1-xRuxO3 (with x = 0.05 and 0.1) were synthesized using the conventional solid state reaction route and found single phase in nature. Electrical resistivity measurements as a function of temperature in range 5 K-400 K and as a function of magnetic field up to 5 Tesla were performed using d.c. four-probe method. Magnetization data were acquired as a function of temperature in a range 10 K-400 K with an applied magnetic field of 500 Oe. When Mn is partially substituted by Cr and Ru the system displays dramatic changes in the electrical transport behavior and shows double-peaked feature in resistivity curve. Both Cr and Ru substitutions effectively reduce insulator-metal transition (TP) and paramagnetic-ferromagnetic transition (TC) temperatures implying that there might exist FM interaction between Mn+3 and Cr+3 as well Mn+3 and Ru+4. The largest low-temperature magnetoresistance (MR%) is attributed to grain boundary effects and difference in size disorder for Cr and Ru substituted compounds.

  4. Exact ab initio transport coefficients in bcc Fe-X (X=Cr, Cu, Mn, Ni, P, Si) dilute alloys

    NASA Astrophysics Data System (ADS)

    Messina, Luca; Nastar, Maylise; Garnier, Thomas; Domain, Christophe; Olsson, Pär

    2014-09-01

    Defect-driven diffusion of impurities is the major phenomenon leading to formation of embrittling nanoscopic precipitates in irradiated reactor pressure vessel (RPV) steels. Diffusion depends strongly on the kinetic correlations that may lead to flux coupling between solute atoms and point defects. In this work, flux coupling phenomena such as solute drag by vacancies and radiation-induced segregation at defect sinks are systematically investigated for six bcc iron-based dilute binary alloys, containing Cr, Cu, Mn, Ni, P, and Si impurities, respectively. First, solute-vacancy interactions and migration energies are obtained by means of ab initio calculations; subsequently, self-consistent mean field theory is employed in order to determine the exact Onsager matrix of the alloys. This innovative multiscale approach provides a more complete treatment of the solute-defect interaction than previous multifrequency models. Solute drag is found to be a widespread phenomenon that occurs systematically in ferritic alloys and is enhanced at low temperatures (as for instance RPV operational temperature), as long as an attractive solute-vacancy interaction is present, and that the kinetic modeling of bcc alloys requires the extension of the interaction shell to the second-nearest neighbors. Drag occurs in all alloys except Fe(Cr); the transition from dragging to nondragging regime takes place for the other alloys around (Cu, Mn, Ni) or above (P, Si) the Curie temperature. As far as only the vacancy-mediated solute migration is concerned, Cr depletion at sinks is foreseen by the model, as opposed to the other impurities which are expected to enrich up to no less than 1000 K. The results of this study confirm the current interpretation of the hardening processes in ferritic-martensitic steels under irradiation.

  5. Annealing texture of a cold-rolled Fe-Mn-Al-Si-C alloy

    NASA Astrophysics Data System (ADS)

    Bhattacharya, Basudev; Ray, Ranjit Kumar

    2015-09-01

    The study of recrystallization texture of a cold deformed Fe-Mn-Al-Si-C alloy, with about 30% Mn, has been discussed in this paper. The alloy is fully austenitic at room temperature, and therefore, principal FCC rolling textures were developed in this material at different stages of cold rolling. The present study was undertaken to observe the transformation of FCC rolling texture during recrystallization of a heavily cold deformed specimen. It was observed that isothermal annealing at 750 °C led to a weak recrystallisation texture, which was quite similar to the deformation texture developed at the early stage of cold rolling. During recovery stage, a strong Bs/Goss-type texture was developed, which was identified as a new observation in this work.

  6. Effect of surface roughness on the development of protective Al 2O 3 on Fe-10Al (at.%) alloys containing 0-10 at.% Cr

    NASA Astrophysics Data System (ADS)

    Zhang, Z. G.; Hou, P. Y.; Gesmundo, F.; Niu, Y.

    2006-11-01

    The effect of alloy surface roughness, achieved by different degrees of surface polishing, on the development of protective alumina layer on Fe-10 at.% Al alloys containing 0, 5, and 10 at.% Cr was investigated during oxidation at 1000 °C in 0.1 MPa oxygen. For alloys that are not strong Al 2O 3 formers (Fe-10Al and Fe-5Cr-10Al), the rougher surfaces increased Fe incorporation into the overall surface layer. On the Fe-10Al, more iron oxides were formed in a uniform layer of mixed aluminum- and iron-oxides since the layer was thicker. On the Fe-5Cr-10Al, more iron-rich nodules developed on an otherwise thin Al 2O 3 surface layer. These nodules nucleated preferentially along surface scratch marks but not on alloy grain boundaries. For the strong Al 2O 3-forming Fe-10Cr-10Al alloy, protective alumina surface layers were observed regardless of the surface roughness. These results indicate that the formation of a protective Al 2O 3 layer on Fe-Cr-Al surfaces is not dictated by Al diffusion to the surface. More cold-worked surfaces caused an enhanced Fe diffusion, hence produced more Fe-rich oxides during the early stage of oxidation.

  7. Comparison of the Isothermal Oxidation Behavior of As-Cast Cu-17%Cr and Cu-17%Cr-5%Al. Part 1; Oxidation Kinetics

    NASA Technical Reports Server (NTRS)

    Raj. Sai V.

    2008-01-01

    The isothermal oxidation kinetics of as-cast Cu-17%Cr and Cu-17%Cr-5%Al in air were studied between 773 and 1173 K under atmospheric pressure. These observations reveal that Cu- 17%Cr-5%Al oxidizes at significantly slower rates than Cu-17%Cr. The rate constants for the alloys were determined from generalized analyses of the data without an a priori assumption of the nature of the oxidation kinetics. Detailed analyses of the isothermal thermogravimetric weight change data revealed that Cu-17%Cr exhibited parabolic oxidation kinetics with an activation energy of 165.9 9.5 kJ mol-1. In contrast, the oxidation kinetics for the Cu-17%Cr- 5%Al alloy exhibited a parabolic oxidation kinetics during the initial stages followed by a quartic relationship in the later stages of oxidation. Alternatively, the oxidation behavior of Cu-17%CR- 5%Al could be better represented by a logarithmic relationship. The parabolic rate constants and activation energy data for the two alloys are compared with literature data to gain insights on the nature of the oxidation mechanisms dominant in these alloys.

  8. Comparison of the Isothermal Oxidation Behavior of As-Cast Cu-17 Percent Cr and Cu-17 Percent Cr-5 Percent Al. Part 1; Oxidation Kinetics

    NASA Technical Reports Server (NTRS)

    Raj, S. V.

    2008-01-01

    The isothermal oxidation kinetics of as-cast Cu-17%Cr and Cu-17%Cr-5%Al in air were studied between 773 and 1173 K under atmospheric pressure. These observations reveal that Cu-17%Cr-5%Al oxidizes at significantly slower rates than Cu-17%Cr. The rate constants for the alloys were determined from generalized analyses of the data without an a priori assumption of the nature of the oxidation kinetics. Detailed analyses of the isothermal thermogravimetric weight change data revealed that Cu-17%Cr exhibited parabolic oxidation kinetics with an activation energy of 165.9+/-9.5 kJ/mol. In contrast, the oxidation kinetics for the Cu-17%Cr-5%Al alloy exhibited a parabolic oxidation kinetics during the initial stages followed by a quartic relationship in the later stages of oxidation. Alternatively, the oxidation behavior of Cu-17%CR-5%Al could be better represented by a logarithmic relationship. The parabolic rate constants and activation energy data for the two alloys are compared with literature data to gain insights on the nature of the oxidation mechanisms dominant in these alloys.

  9. Comparison of the Isothermal Oxidation Behavior of As-Cast Cu-17%Cr and Cu-17%Cr-5%Al. Part 1; Oxidation Kinetics

    NASA Technical Reports Server (NTRS)

    Raj. Sai V.

    2008-01-01

    The isothermal oxidation kinetics of as-cast Cu-17%Cr and Cu-17%Cr-5%Al in air were studied between 773 and 1173 K under atmospheric pressure. These observations reveal that Cu- 17%Cr-5%Al oxidizes at significantly slower rates than Cu-17%Cr. The rate constants for the alloys were determined from generalized analyses of the data without an a priori assumption of the nature of the oxidation kinetics. Detailed analyses of the isothermal thermogravimetric weight change data revealed that Cu-17%Cr exhibited parabolic oxidation kinetics with an activation energy of 165.9 +/- 9.5 kJ/mol. In contrast, the oxidation kinetics for the Cu-17%Cr- 5%Al alloy exhibited a parabolic oxidation kinetics during the initial stages followed by a quartic relationship in the later stages of oxidation. Alternatively, the oxidation behavior of Cu-17%CR- 5%Al could be better represented by a logarithmic relationship. The parabolic rate constants and activation energy data for the two alloys are compared with literature data to gain insights on the nature of the oxidation mechanisms dominant in these alloys.

  10. Structural phase transition, Néel temperature enhancement, and persistent magneto-dielectric coupling in Cr-substituted Mn3O4

    NASA Astrophysics Data System (ADS)

    Dwivedi, G. D.; Kumar, Abhishek; Yang, K. S.; Chen, B. Y.; Liu, K. W.; Chatterjee, Sandip; Yang, H. D.; Chou, H.

    2016-05-01

    Structural phase transition and Néel temperature (TN) enhancement were observed in Cr-substituted Mn3O4 spinels. Structural, magnetic, and dielectric properties of (Mn1-xCrx)3O4 (where x = 0.00, 0.10, 0.20, 0.25, 0.30, 0.40, and 0.50) were investigated. Cr-substitution induces room temperature structural phase transition from tetragonally distorted I41/amd (x = 0.00) to cubic Fd 3 ¯ m (x = 0.50). TN is found to increase from 43 K (x = 0.00) to 58 K (x = 0.50) with Cr-substitution. The spin ordering-induced dielectric anomaly near TN ensures that magneto-dielectric coupling persists in the cubic x = 0.50 system. X-ray absorption spectra reveal that Cr exists in a trivalent oxidation state and prefers the octahedral (Oh)-site, replacing Mn3+. Due to a reduction in the Jahn-Teller active Mn3+ cation and an increase in the smaller Cr3+ cation, the system begins to release the geometrical frustration by lowering its degeneracy. Consequently, a phase transition, from distorted tetragonal structure to the more symmetric cubic phase, occurs.

  11. Effect of vanadium and chromium on the microstructural features of V-Cr-Mn-Ni spheroidal carbide cast irons

    NASA Astrophysics Data System (ADS)

    Efremenko, V. G.; Shimizu, K.; Cheiliakh, A. P.; Kozarevskaya, T. V.; Kusumoto, K.; Yamamoto, K.

    2014-11-01

    The objective of this investigation is to study the influence of vanadium (5.0wt%-10.0wt%) and chromium (0-9.0wt%) on the microstructure and hardness of Cr-V-Mn-Ni white cast irons with spheroidal vanadium carbides. The alloys' microstructural features are presented and discussed with regard to the distribution of phase elements. The structural constituents of the alloys are spheroidal VC, proeutectoid cementite, ledeburite eutectic, rosette-shaped carbide eutectic (based on M7C3), pearlite, martensite, and austenite. Their combinations and area fraction (AF) ratios are reported to be influenced by the alloys' chemical composition. Spheroidized VC particles are found to be sites for the nucleation of carbide eutectics. Cr and V are shown to substitute each other in the VC and M7C3 carbides, respectively. Chromium alloying leads to the formation of a eutectic (γ-Fe + M7C3), preventing the appearance of proeutectoid cementite in the structure. Vanadium and chromium are revealed to increase the total carbide fraction and the amount of austenite in the matrix. Cr is observed to play a key role in controlling the metallic matrix microstructure.

  12. Immobilization of heavy metals (Pb, Cu, Cr, Zn, Cd, Mn) in the mineral additions containing concrete composites.

    PubMed

    Giergiczny, Zbigniew; Król, Anna

    2008-12-30

    The presented work determines the level of heavy metals (Pb+2, Cu+2, Zn+2, Cr+6, Cd+2, Mn+2) immobilization in the composites produced using Ordinary Portland Cement (OPC) as well as of binders containing large amount of mineral additives in its composition-siliceous fly ash (FA), fluidized bed combustion ash (FFA) and ground granulated blast furnace slag (GGBFS). Heavy metals were introduced to cementitious materials in the form of soluble salts as well as components of hazardous wastes (medical ash, metallurgical dust). It has been stated, that the level of heavy metals immobilization is combined with composites composition. Majority of analyzed heavy metals, added to binders' composition in the form of heavy metal salts achieves high level of immobilization, in mortar based on binder with 85% GGBFS and 15% OPC. The lowest immobilization level was reached for chromium Cr+6 added to hardening mortars as Na2Cr2O72H2O. The level ranges from 85.97% in mortars made on blended binder (20% OPC, 30% FFA and 50% GGBFS) to 93.33% in mortar produced on OPC. The increase of the so-called immobilization degree with time of hardened material maturing was found. This should be attributed to the pozzolanic or pozzolanic/hydraulic properties of components used; their effect on microstructure of hardened material is also important. Mineral additions enter the hydration reactions in the mixtures and favor the formation of specific microstructure promoting the immobilization of hazardous elements. PMID:18423859

  13. The role of magnetism in the formation of the two-phase miscibility gap in β Cu-Al-Mn

    NASA Astrophysics Data System (ADS)

    Lanzini, Fernando; Alés, Alejandro

    2015-12-01

    A theoretical study of the ground state properties of alloys with compositions along the pseudobinary line Cu3Al-Cu2AlMn is presented. Cohesive energies, lattice parameters and magnetic moments of the two limiting compounds and three intermediate compositions are calculated by means of density functional theory. In order to evaluate the role of magnetism, both the spin-polarized (SP) and the non spin-polarized (NSP) cases have been considered. It is shown that magnetism plays a central role on the stabilization of the L21 crystal structure in Cu2AlMn, and in the formation of the miscibility gap in Cu3Al-Cu2AlMn. The considerable lattice mismatch between the end compounds can be attributed also to magnetic effects.

  14. Comparative study of hydrogen sulfide adsorption in the MIL-53(Al, Cr, Fe), MIL-47(V), MIL-100(Cr), and MIL-101(Cr) metal-organic frameworks at room temperature.

    PubMed

    Hamon, Lomig; Serre, Christian; Devic, Thomas; Loiseau, Thierry; Millange, Franck; Férey, Gérard; De Weireld, Guy

    2009-07-01

    Hydrogen sulfide gravimetric isotherm adsorption measurements were carried out on MIL-53(Al, Cr, Fe), MIL-47(V), MIL-100(Cr), and MIL-101(Cr) metal-organic frameworks (MOFs). A two-step adsorption mechanism related to a breathing effect was observed for MIL-53 terephthalate-based MOFs. Methane adsorption measurements highlighted the regenerability of MIL-53(Al, Cr) and MIL-47(V) MOFs after H(2)S treatment, whereas MIL-100 and MIL-101 CH(4) adsorption capacities were significantly decreased. PMID:19505146

  15. Hot Ductility Behaviors in the Weld Heat-Affected Zone of Nitrogen-Alloyed Fe-18Cr-10Mn Austenitic Stainless Steels

    NASA Astrophysics Data System (ADS)

    Moon, Joonoh; Lee, Tae-Ho; Hong, Hyun-Uk

    2015-04-01

    Hot ductility behaviors in the weld heat-affected zone (HAZ) of nitrogen-alloyed Fe-18Cr-10Mn austenitic stainless steels with different nitrogen contents were evaluated through hot tension tests using Gleeble simulator. The results of Gleeble simulations indicated that hot ductility in the HAZs deteriorated due to the formation of δ-ferrite and intergranular Cr2N particles. In addition, the amount of hot ductility degradation was strongly affected by the fraction of δ-ferrite.

  16. Thermoelectric properties of Fe and Al double substituted MnSi{sub γ} (γ~1.73)

    SciTech Connect

    Barczak, S.A.; Downie, R.A.; Popuri, S.R.; Decourt, R.; Pollet, M.; Bos, J.W.G.

    2015-07-15

    Two series of Fe and Al double substituted MnSi{sub γ} chimney ladders with a nominal valence electron count, VEC=14 per transition metal were prepared (γ=1.75). Simultaneous replacement of Mn with Fe and Si with Al yielded the Mn{sub 1−x}Fe{sub x}Si{sub 1.75−x}Al{sub x} series while the second Mn{sub 1−x}Fe{sub x}Si{sub 1.75–1.75x}Al{sub 2x} series follows the pseudo-binary between MnSi{sub 1.75} and FeAl{sub 2}. Scanning electron microscopy and elemental mapping revealed that ~60% of the nominal Al content ends up in the product with the remainder lost to sublimation, and that up to 7% Al can be substituted in the main group sublattice. Profile analysis of X-ray powder diffraction data revealed gradual changes in the cell metrics, consistent with the simultaneous substitution of Fe and Al in a fixed ratio. All samples are p-type with VEC≈13.95 from the structural data and ~1×10{sup 21} holes cm{sup −3} from variable temperature Seebeck measurements. The substituted samples have lower electrical resistivities (ρ{sub 300} {sub K}=2–5 mΩ cm) due to an improved microstructure. This leads to increased thermoelectric power factors (largest S{sup 2}/ρ=1.95 mW m{sup −1} K{sup −2}) compared to MnSi{sub γ}. The thermal conductivity for the Mn{sub 0.95}Fe{sub 0.05}Si{sub 1.66}Al{sub 0.1} sample is 2.7 W m{sup −1} K{sup −1} between 300 and 800 K, and is comparable to literature data for the parent material. - Graphical abstract: The crystal structure, microstructure and thermoelectric properties of Fe and Al double substituted MnSi{sub γ} (γ~1.73) have been investigated. - Highlights: • Up to 7% Al can be substituted in MnSi{sub γ} when co-doped with Fe. • Improved microstructure and reduced electrical resistivities for Al substituted samples. • Largest power factor 1.95 mW m{sup −1} K{sup −2} and best estimated ZT=0.5.

  17. Cr diffusion in MgAl2O4 synthetic spinels: preliminary results

    NASA Astrophysics Data System (ADS)

    Freda, C.; Celata, B.; Andreozzi, G.; Perinelli, C.; Misiti, V.

    2012-04-01

    Chromian spinel is an accessory phase common in crustal and mantle rocks, including peridotites, gabbros and basalts. Spinel, it has been identified as one of the most effective, sensible, and versatile petrogenetic indicator in mafic and ultramafic rock systems due to the strict interdependence between its physico-chemical properties (chemical composition, cation configuration etc.) and genetic conditions (temperature, pressure, and chemical characteristics of the system). In particular, studies on intra- and inter-crystalline Mg-Fe2+, Cr-Al exchange demonstrated the close relationship between spinel composition and both degree of partial melting and equilibrium temperature of spinel-peridotites. Moreover, studies focused on the chemical zoning of Mg-Fe2+ and/or Cr-Al components in spinel have been used, combined with a diffusion model, to provide quantitative information on peridotites and gabbros pressure-temperature paths and on deformation mechanisms. Although these potentials, most of the experimental studies have been performed on spinels hosting a limited content of divalent iron (sensu stricto, MgAl2O4), whereas the scarce studies on Cr-Al inter-diffusion coefficient have been performed at 3-7 GPa as pressure boundary condition. In order to contribute to the understanding of processes occurring in the lithospheric mantle, we have initiated an experimental research project aiming at determining the Cr-Al inter-diffusion in spinel at 2 GPa pressure and temperature ranging from 1100 to 1250 °C. The experiments were performed in a end-loaded piston cylinder by using a 19 mm assembly and graphite-Pt double capsules. As starting materials we used synthetic Mg-Al spinel (200-300 μm in size) and Cr2O3 powder. Microanalyses of experimental charge were performed on polished carbon-coated mounts by electronic microprobe. Line elemental analyses were made perpendicular to the contact surface between Cr2O3 powder and spinel, at interval of 2 μm. By processing these

  18. Thermodynamic stability, magnetism and half metallicity of Mn2CoAl/GaAs(0 0 1) interface

    NASA Astrophysics Data System (ADS)

    Feng, Yu; Zhou, Ting; Chen, Xiaorui; Yuan, Hongkuan; Chen, Hong

    2015-07-01

    Interface properties of the heterojunction which is composed of the inverse Heusler alloy Mn2 CoAl and semiconductor GaAs are investigated by employing the first-principles density functional simulations. Two kinds of interface structures, namely the top-type and bridge-type structure by connecting termination of nine Mn2 CoAl layers to the top of the As-terminated GaAs layer and bridge site between interface As atoms are respectively built. Our calculations reveal that, as for the structure with the same interface atoms, different atoms sitting directly on top of the interface As atom will lead to different interface magnetism and electronic structures. The calculated phase diagram reveals that the top-type structure including natural MnCo or MnAl termination is stable only when the interface Mn or interface Al atom directly locates on top of the As atom. Besides, bridge-type and top-type structures containing a pure Mn interface are always thermodynamically accessible regardless of values of the chemical potential of Mn and Co. The atom-resolved spin magnetic moments of most interface magnetic atoms are enhanced due to the rehybridization caused by symmetry breaking at the interface. Further analyses on electronic structures indicate that, owing to the interface effect, the interface half metallicity of all structures are completely destroyed. However, the top-type structure with MnAl termination where the interface Al atom directly sits on top of the As atom preserves the highest interface spin polarization of 80%, indicating that it has more advantages in spintronics application than other atomic terminations.

  19. New type of Al-based decagonal quasicrystal in Al60Cr20Fe10Si10 alloy

    NASA Astrophysics Data System (ADS)

    He, Zhanbing; Ma, Haikun; Li, Hua; Li, Xingzhong; Ma, Xiuliang

    2016-03-01

    A new kind of decagonal quasicrystal (DQC) with a periodicity of 1.23 nm was observed in the as-cast quaternary Al60Cr20Fe10Si10 alloy. The intensity distribution of some spots in the selected-area electron diffraction pattern along the tenfold zone axis was found to be different from other Al-based DQCs. High-angle annular dark-field scanning transmission electron microscopy was adopted to reveal the structural features at an atomic level. Both the tenfold symmetry and symmetry-broken decagonal (D) clusters of 1.91 nm in diameter were found, but with structural characteristics different from the corresponding D clusters in the other Al-based DQCs. The neighboring D clusters are connected by sharing one edge rather than covering, suggesting the tiling model is better than the covering model for structural description.

  20. New type of Al-based decagonal quasicrystal in Al60Cr20Fe10Si10 alloy

    PubMed Central

    He, Zhanbing; Ma, Haikun; Li, Hua; Li, Xingzhong; Ma, Xiuliang

    2016-01-01

    A new kind of decagonal quasicrystal (DQC) with a periodicity of 1.23 nm was observed in the as-cast quaternary Al60Cr20Fe10Si10 alloy. The intensity distribution of some spots in the selected-area electron diffraction pattern along the tenfold zone axis was found to be different from other Al-based DQCs. High-angle annular dark-field scanning transmission electron microscopy was adopted to reveal the structural features at an atomic level. Both the tenfold symmetry and symmetry-broken decagonal (D) clusters of 1.91 nm in diameter were found, but with structural characteristics different from the corresponding D clusters in the other Al-based DQCs. The neighboring D clusters are connected by sharing one edge rather than covering, suggesting the tiling model is better than the covering model for structural description. PMID:26928759

  1. Luminescence of photoactivated pristine and Cr-doped MgAl2O4 spinel

    NASA Astrophysics Data System (ADS)

    Artemyeva, E. S.; Barinov, D. S.; Atitar, F. M.; Murashkina, A. A.; Emeline, A. V.; Serpone, N.

    2015-04-01

    This Letter reports a comparative study of the luminescence from pristine and Cr-doped MgAl2O4 spinel induced by different excitation mechanisms: photoluminescence (PhL), thermoluminescence (ThL) and Photo-Induced Chemisorption Luminescence (the PhICL phenomenon) to understand the mechanism of PhICL emission. Cr-doping alters the major pathway of physical relaxation through a luminescence pathway: quenching of the luminescence associated with intrinsic defects and appearance of the luminescence from Cr3+-states. The similarity between ThL and PhICL spectra suggest the mechanism of the PhICL phenomenon is due to electron transfer from the surface to the emission centers of luminescence; an energy transfer pathway is not precluded.

  2. Properties of Cr:LiSrAlF[sub 6] crystals for laser operation

    SciTech Connect

    Chai, B.H.T. ); Payne, S.A.; Smith, L.K.; Beach, R.J.; Tassano, J.H.; DeLoach, L.D.; Kway, W.L.; Solarz, R.W.; Krupke, W.F. )

    1994-08-20

    We have performed several physical and optical measurements on the Cr:LiSAF (LiSrAlF[sub 6]) laser material that are relevant to its laser performance, including thermal and mechanical properties, water durabilities, and Auger upconversion constants. The expansion coefficient, Young's modulus, fracture toughness, thermal conductivity, and heat capacity are all used to determine an overall thermomechanical figure of merit for the crystal. An investigation of the water durability suggests that the cooling solution should be maintained at pH = 7 to ameliorate problems associated with water dissolution. The Auger constant was found to become much more significant at higher Cr doping, in which excited-state migration leads to a substantial increase in the upconversion rate. We propose a design for a 50-W Cr:LiSAF laser system that is based on a detailed knowledge of all the relevant material parameters.

  3. Optical and physical properties of the LiSrAlF[sub 6]:Cr laser crystal

    SciTech Connect

    Smith, L.K.; Payne, S.A.; Tassano, J.B.; DeLoach, L.D.; Kway, W.L.; Krupke, W.F.

    1993-05-18

    We have measured several of the physical and optical parameters of the LiSrAlF[sub 6]:Cr or Cr:LiSAF laser material that are important to its laser performance, including the thermomechanical properties, water durabilities and Auger upconversion constants. A thermomechanical figure-of-merit has been determined from measurements of the fracture toughness, expansion coefficient, thermal conductivity, Young's modulus, and heat capacity. Tests of water durability suggest that a neutral pH of 7 is optimum to minimize water dissolution. The Auger effect was found to be a significant factor at higher Cr concentration, where excited-state migration leads to an increase in the upconversion rate. 17 refs, 1 fig, 4 tabs.

  4. Optical and physical properties of the LiSrAlF{sub 6}:Cr laser crystal

    SciTech Connect

    Smith, L.K.; Payne, S.A.; Tassano, J.B.; DeLoach, L.D.; Kway, W.L.; Krupke, W.F.

    1993-05-18

    We have measured several of the physical and optical parameters of the LiSrAlF{sub 6}:Cr or Cr:LiSAF laser material that are important to its laser performance, including the thermomechanical properties, water durabilities and Auger upconversion constants. A thermomechanical figure-of-merit has been determined from measurements of the fracture toughness, expansion coefficient, thermal conductivity, Young`s modulus, and heat capacity. Tests of water durability suggest that a neutral pH of 7 is optimum to minimize water dissolution. The Auger effect was found to be a significant factor at higher Cr concentration, where excited-state migration leads to an increase in the upconversion rate. 17 refs, 1 fig, 4 tabs.

  5. Microstructure and microhardness of nanostructured Al-4.6Cu-Mn alloy ribbons

    NASA Astrophysics Data System (ADS)

    Chen, Zhong-wei; Fan, Qin-ying; Zhao, Kai

    2015-08-01

    The microstructural characteristics and microhardness of nanostructured Al-4.6Cu-Mn ribbons produced by melt spinning were investigated using field-emission gun scanning electron microscopy, transmission electron microscopy, and hardness testing, and the results were compared to those of similar ribbons manufactured by direct-chill casting. It is shown that the nanostructure of the as-melt-spun ribbons consists of α-Al dendrites with a secondary dendrite arm spacing of approximately 0.55-0.80 μm and ultrafine eutectic crystals of a nanosized scale of approximately 100-200 nm on dendritic boundaries. The solidification time and cooling rate of 46-μm-thick ribbons were estimated to be 1.3 × 10-6 s and 4.04 × 106 K·s-1, respectively. At an aging temperature of 190°C, the coherent θ″ phase in aged ribbons gradually transforms into nanoscale θ'-phase platelets as the aging time is extended from 2 to 8 h; the rod-like morphology of the T (Al20Cu2Mn3) dispersoid with 120-160-nm diameter also forms, which results in peak aging hardness. The precipitation behaviors of aged ribbons cannot be changed at the high cooling rates of as-cast ribbons. However, a finer and more uniformly distributed microstructure and a supersaturated solid solution at a high cooling rate can shorten the time required to obtain a certain aging hardness before peak hardness.

  6. Numerical Study of Microstructural Evolution During Homogenization of Al-Si-Mg-Fe-Mn Alloys

    NASA Astrophysics Data System (ADS)

    Priya, Pikee; Johnson, David R.; Krane, Matthew J. M.

    2016-09-01

    Microstructural evolution during homogenization of Al-Si-Mg-Fe-Mn alloys occurs in two stages at different length scales: while holding at the homogenization temperature (diffusion on the scale of the secondary dendrite arm spacing (SDAS) in micrometers) and during quenching to room temperature (dispersoid precipitation at the nanometer to submicron scale). Here a numerical study estimates microstructural changes during both stages. A diffusion-based model developed to simulate evolution at the SDAS length scale predicts homogenization times and microstructures matching experiments. That model is coupled with a Kampmann Wagner Neumann-based precipitate nucleation and growth model to study the effect of temperature, composition, as-cast microstructure, and cooling rates during posthomogenization quenching on microstructural evolution. A homogenization schedule of 853 K (580 °C) for 8 hours, followed by cooling at 250 K/h, is suggested to optimize microstructures for easier extrusion, consisting of minimal α-Al(FeMn)Si, no β-AlFeSi, and Mg2Si dispersoids <1 μm size.

  7. Microstructural Developments and Tensile Properties of Lean Fe-Mn-Al-C Lightweight Steels

    NASA Astrophysics Data System (ADS)

    Sohn, S. S.; Lee, S.; Lee, B.-J.; Kwak, J.-H.

    2014-09-01

    Concepts of Fe-Al-Mn-C-based lightweight steels are fairly simple, but primary metallurgical issues are complicated. In this study, recent studies on lean-composition lightweight steels were reviewed, summarized, and emphasized by their microstructural development and mechanical properties. The lightweight steels containing a low-density element of Al were designed by thermodynamic calculation and were manufactured by conventional industrial processes. Their microstructures consisted of various secondary phases as κ-carbide, martensite, and austenite in the ferrite matrix according to manufacturing and annealing procedures. The solidification microstructure containing segregations of C, Mn, and Al produced a banded structure during the hot rolling. The (ferrite + austenite) duplex microstructure was formed after the annealing, and the austenite was retained at room temperature. It was because the thermal stability of austenite nucleated from fine κ-carbide was quite high due to fine grain size of austenite. Because these lightweight steels have outstanding properties of strength and ductility as well as reduced density, they give a promise for automotive applications requiring excellent properties.

  8. Numerical Study of Microstructural Evolution During Homogenization of Al-Si-Mg-Fe-Mn Alloys

    NASA Astrophysics Data System (ADS)

    Priya, Pikee; Johnson, David R.; Krane, Matthew J. M.

    2016-06-01

    Microstructural evolution during homogenization of Al-Si-Mg-Fe-Mn alloys occurs in two stages at different length scales: while holding at the homogenization temperature (diffusion on the scale of the secondary dendrite arm spacing (SDAS) in micrometers) and during quenching to room temperature (dispersoid precipitation at the nanometer to submicron scale). Here a numerical study estimates microstructural changes during both stages. A diffusion-based model developed to simulate evolution at the SDAS length scale predicts homogenization times and microstructures matching experiments. That model is coupled with a Kampmann Wagner Neumann-based precipitate nucleation and growth model to study the effect of temperature, composition, as-cast microstructure, and cooling rates during posthomogenization quenching on microstructural evolution. A homogenization schedule of 853 K (580 °C) for 8 hours, followed by cooling at 250 K/h, is suggested to optimize microstructures for easier extrusion, consisting of minimal α-Al(FeMn)Si, no β-AlFeSi, and Mg2Si dispersoids <1 μm size.

  9. Major differences between the binuclear manganese boronyl carbonyl Mn2(BO)2(CO)9 and its isoelectronic chromium carbonyl analogue Cr2(CO)11.

    PubMed

    Chang, Yu; Li, Qian-Shu; Xie, Yaoming; King, R Bruce

    2013-03-14

    The lowest energy structures of the manganese boronyl carbonyl Mn2(BO)2(CO)9 by more than 8 kcal/mol are found to have a single end-to-end bridging BO group bonding to one manganese atom through its boron atom and to the other manganese atom through its oxygen atom. The long Mn···Mn distances in these structures indicate the lack of direct manganese-manganese bonding as confirmed by essentially zero Wiberg bond indices. These Mn2(BO)2(CO)9 structures are favored thermochemically by more than 25 kcal/mol over dissociation into mononuclear fragments and thus appear to be viable synthetic objectives. This contrasts with the isoelectronic Cr2(CO)11 system, which is predicted to be disfavored relative to the mononuclear fragments Cr(CO)6 + Cr(CO)5. Analogous Mn2(BO)2(CO)9 structures with an end-to-end bridging CO group lie ∼17 kcal/mol in energy above the corresponding structures with end-to-end bridging BO groups. The lowest energy Mn2(BO)2(CO)9 structures without an end-to-end bridging BO group provide unprecedented examples of the coupling of two terminal BO groups to form a terminal dioxodiborene (B2O2) ligand with a B-B distance of ∼1.9 Å. Still higher energy Mn2(BO)2(CO)9 structures include singly bridged and doubly semibridged structures analogous to the previously optimized lowest energy Cr2(CO)11 structures. PMID:23402266

  10. First-principles study of molecular hydrogen adsorption and dissociation on Al(n)Cr (n = 1-13) clusters.

    PubMed

    Guo, Ling

    2013-04-25

    Hydrogen adsorption dissociation on clusters is a widely studied subject that provides the opportunity to gain a basic understanding of the complicated nature of many interesting problems, such as hydrogen embrittlement of metals, catalytic processes, hydrogen storage, etc. In this study, I present density functional calculations of H2 adsorption and dissociation on small-sized Al(n)Cr clusters for n = 1-13. My results show that H2 is easily physically absorbed on the top Cr atom of AlnCr clusters with a side-on orientation rather than an end-on orientation. In addition, I investigate a possible dissociation mechanism and dissociation pathway of H2 on selected Al2Cr and Al7Cr. My findings suggest that the hydrogen dissociation behavior on Al(n)Cr clusters characterized by the activation barrier and reaction energy can be tuned by controllable doping. Thus, Al2Cr and Al7Cr clusters might serve as highly efficient and low-cost catalysts for hydrogen dissociation. PMID:23581518

  11. The effect of ion implantation on the oxidation resistance of vacuum plasma sprayed CoNiCrAlY coatings

    NASA Astrophysics Data System (ADS)

    Jiang, Jie; Zhao, Huayu; Zhou, Xiaming; Tao, Shunyan; Ding, Chuanxian

    2012-11-01

    CoNiCrAlY coatings prepared by vacuum plasma spraying (VPS) were implanted with Nb and Al ions at a fluence of 1017 atoms/cm2. The effects of ion implantation on the oxidation resistance of CoNiCrAlY coatings were investigated. The thermally grown oxide (TGO) formed on each specimen was characterized by XRD, SEM and EDS, respectively. The results showed that the oxidation process of CoNiCrAlY coatings could be divided into four stages and the key to obtaining good oxidation resistance was to remain high enough amount of Al and promote the lateral growth of TGO. The implantation of Nb resulted in the formation of continuous and dense Al2O3 scale to improve the oxidation resistance. The Al implanted coating could form Al2O3 scale at the initial stage, however, the scale was soon broken and TGO transformed to non-protective spinel.

  12. TEM and Moessbauer Study of Nano Sized Fe{sub 2}MnAl Flakes

    SciTech Connect

    Vinesh, A.; Sudheesh, V. D.; Lakshmi, N.; Venugopalan, K.

    2011-07-15

    Magnetic and structural properties of L21 ordered Fe{sub 2}MnAl Heusler alloy have been studied by X-ray diffraction, Transmission electron microscopy (TEM), Moessbauer spectroscopy and DC magnetization. Structural texturing induced by ball milling is destroyed on heating while Moessbauer and DC magnetization studies show magnetic texturing persists after thermal treatment. TEM shows large distribution in particle size with an average size of 27 nm. Thermal annealing of ball milled sample results L2{sub 1} ordering and the needle shaped particle contributes spin texturing.

  13. Effect of Cr on Microstructure and Properties of a Series of AlTiCr x FeCoNiCu High-Entropy Alloys

    NASA Astrophysics Data System (ADS)

    Li, Anmin; Ma, Ding; Zheng, Qifeng

    2014-04-01

    A series of AlTiCr x FeCoNiCu ( x: molar ratio, x = 0.5, 1.0, 1.5, 2.0, 2.5) high-entropy alloys (HEAs) were prepared by vacuum arc furnace. These alloys consist of α-phase, β-phase, and γ-phase. These phases are solid solutions. The structure of α-phase and γ-phase is face-centered cubic structure and that of β-phase is body-centered cubic (BCC) structure. There are four typical cast organizations in these alloys such as petal organization (α-phase), chrysanthemum organization (α-phase + β-phase), dendrite (β-phase), and inter-dendrite (γ-phase). The solidification mode of these alloys is affected by Chromium. If γ-phase is not considered, AlTiCr0.5FeCoNiCu and AlTiCrFeCoNiCu belong to hypoeutectic alloys; AlTiCr1.5FeCoNiCu, AlTiCr2.0FeCoNiCu, and AlTiCr2.5FeCoNiCu belong to hypereutectic alloys. The cast organizations of these alloys consist of pro-eutectic phase and eutectic structure (α + β). Compact eutectic structure and a certain amount of fine β-phase with uniform distribution are useful to improve the microhardness of the HEAs. More γ-phase and the microstructure with similar volume ratio values of α-phase and β-phase improve the compressive strength and toughness of these alloys. The compressive fracture of the series of AlTiCr x FeCoNiCu HEAs shows brittle characteristics, suggesting that these HEAs are brittle materials.

  14. Characterization of Cold Sprayed CuCrAl Coated GRCop-84 Substrates for Reusable Launch Vehicles

    NASA Technical Reports Server (NTRS)

    Raj, S . V.; Barrett, C. A.; Lerch, B. A.; Karthikeyan, J.; Ghosn, L. J.; Haynes, J.

    2005-01-01

    An advanced Cu-8(at.%)Cr-4%Nb alloy developed at NASA's Glenn Research Center, and designated as GRCop-84, is currently being considered for use as combustor liners and nozzles in NASA's future generations of reusable launch vehicles (RLVs). Despite the fact that this alloy has superior mechanical and oxidation properties compared to many commercially available copper alloys, it is felt that its high temperature and environmental resistance capabilities can be further enhanced with the development and use of suitable coatings. Several coatings and processes are currently being evaluated for their suitability and future down selection. A newly developed CuCrAl has shown excellent oxidation resistance compared to current generation Cu-Cr coating alloys. Cold spray technology for depositing the CuCrAl coating on a GRCop-84 substrate is currently being developed under NASA's Next Generation Launch Technology (NGLT) Propulsion Research and Technology (PR&T) project. The microstructures, mechanical and thermophysical properties of overlay coated GRCop-84 substrates are discussed.

  15. The Temporal Evolution of the Nanostructure of a Model Ni-Al-Cr Superalloy

    NASA Technical Reports Server (NTRS)

    Sudbrack, Chantal K.; Yoon, Kevin E.; Noebe, Ronald D.; Seidman, David N.

    2004-01-01

    The early to the later stages of precipitation of ordered gamma'-precipitates (L1(sub 2)) in Ni-5.2 Al-14.2 Cr (at.%) are studied at 873 K. Precipitates with radii as small as 0.45 nm are characterized fully by three-dimensional atom-probe (3DAP) microscopy. Contrary to what is often assumed by theory or in models, the average precipitate composition is shown to evolve with time, such that solute concentrations decrease toward an equilibrium value given by the solvus lines. Power-law time dependencies of the number density, mean radius, and supersaturations of Al and Cr are discussed in light of theoretical predictions for Ostwald ripening.

  16. Fuel Performance Calculations for FeCrAl Cladding in BWRs

    SciTech Connect

    George, Nathan; Sweet, Ryan; Maldonado, G. Ivan; Wirth, Brian D.; Powers, Jeffrey J.; Worrall, Andrew

    2015-01-01

    This study expands upon previous neutronics analyses of the reactivity impact of alternate cladding concepts in boiling water reactor (BWR) cores and directs focus toward contrasting fuel performance characteristics of FeCrAl cladding against those of traditional Zircaloy. Using neutronics results from a modern version of the 3D nodal simulator NESTLE, linear power histories were generated and supplied to the BISON-CASL code for fuel performance evaluations. BISON-CASL (formerly Peregrine) expands on material libraries implemented in the BISON fuel performance code and the MOOSE framework by providing proprietary material data. By creating material libraries for Zircaloy and FeCrAl cladding, the thermomechanical behavior of the fuel rod (e.g., strains, centerline fuel temperature, and time to gap closure) were investigated and contrasted.

  17. 1300 K Compressive Properties of Directionally Solidified Ni-33Al-33Cr-1Mo

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. Daniel; Raj, S. V.; Locci, Ivan E.

    2000-01-01

    The Ni-33Al-33Cr-1Mo eutectic has been directionally solidified by a modified Bridgeman technique at growth rates ranging from 7.6 to 508 mm/h to produce grain/cellular microstructures, containing alternating plates of NiAl and Cr alloyed with Mo. The grains had sharp boundaries for slower growth rates (< 12.7 mm/h), while faster growth rates (> 25.4 mm/h) lead to cells bounded by intercellular regions. Compressive testing at 1300 K indicated that alloys DS'ed at rates between 25.4 to 254 mm/h possessed the best strengths which exceed that for the as-cast alloy.

  18. Synthesis and characterization of lamellar and fibre-reinforced NiAl-Mo and NiAl-Cr

    NASA Astrophysics Data System (ADS)

    Haenschke, T.; Gali, A.; Heilmaier, M.; Krüger, M.; Bei, H.; George, E. P.

    2010-07-01

    Directionally solidified (DS) alloys of the eutectic systems NiAl-10Mo and NiAl-34Cr (at.%) are potential candidates for high-temperature structural applications. Here, these alloys were first arc-melted and drop-cast. Thereafter, they were directionally solidified (DS) at growth rates of 20 and 80 mm/h while rotating at a fixed rotation speed of 60 revolutions per minute. Specimens of the DS alloys were tested in three-point-bending and uniaxial compression to obtain mechanical properties, including the ductile to brittle transition temperature (DBTT). For the NiAl-Cr system DBTT was found to be around 300 °C. Microstructural observations revealed that in the section perpendicular to the growth direction a uniform distribution of fibres was observed. The expected decrease of the fibre diameter with increasing growth rate was not observed. Instead, the fibre diameter slightly increased with increasing crystal growth rates. First compression tests were performed to get insights into the creep behaviour of these fibre-reinforced microstructures.

  19. Analysis of the FeCrAl Accident Tolerant Fuel Concept Benefits during BWR Station Blackout Accidents

    SciTech Connect

    Robb, Kevin R

    2015-01-01

    Iron-chromium-aluminum (FeCrAl) alloys are being considered for fuel concepts with enhanced accident tolerance. FeCrAl alloys have very slow oxidation kinetics and good strength at high temperatures. FeCrAl could be used for fuel cladding in light water reactors and/or as channel box material in boiling water reactors (BWRs). To estimate the potential safety gains afforded by the FeCrAl concept, the MELCOR code was used to analyze a range of postulated station blackout severe accident scenarios in a BWR/4 reactor employing FeCrAl. The simulations utilize the most recently known thermophysical properties and oxidation kinetics for FeCrAl. Overall, when compared to the traditional Zircaloy-based cladding and channel box, the FeCrAl concept provides a few extra hours of time for operators to take mitigating actions and/or for evacuations to take place. A coolable core geometry is retained longer, enhancing the ability to stabilize an accident. Finally, due to the slower oxidation kinetics, substantially less hydrogen is generated, and the generation is delayed in time. This decreases the amount of non-condensable gases in containment and the potential for deflagrations to inhibit the accident response.

  20. The effect of zirconium on the cyclic oxidation of NiCrAl alloys

    NASA Technical Reports Server (NTRS)

    Barrett, C. A.; Khan, A. S.; Lowell, C. E.

    1981-01-01

    This paper examines results with cyclic oxidation tests of Ni(9-20) Cr(15-30) Al-(x)Zr alloys carried out at 1100 C and 1200 C in static air. The concentration of zirconium varies from 0 to 0.63 atomic percent. Significant aluminum penetration is found in metallographic and electron microscopic examination of oxidized surfaces. Small amounts of zirconium lead to minimal penetration, and with increased zirconium content pronounced oxide penetration is observed.

  1. Effects of ruthenium on phase separation in a model Ni-Al-Cr-Ru superalloy

    NASA Astrophysics Data System (ADS)

    Zhou, Yang; Isheim, Dieter; Hsieh, Gillian; Noebe, Ronald D.; Seidman, David N.

    2013-04-01

    The temporal evolution of a Ni-10.0Al-8.5Cr-2.0Ru (at.%) alloy aged at 1073 K was investigated using transmission electron microscopy (TEM) and atom-probe tomography. The γ‧(L12)-precipitate morphology is spheroidal through 256 h of ageing as a result of adding Ru, which decreases the lattice parameter misfit between the γ‧(L12)- and γ(f.c.c.)-phases. The addition of Ru accelerates the compositional evolution of the γ‧(L12)- and γ(f.c.c.)-phases, which achieve their equilibrium compositions after 0.25 h. Initially, Ru accelerates the partitioning of Ni and Cr to the γ(f.c.c.)-phase, and the partitioning of Al to the γ‧(L12)-phase, but after 0.25 h, Ru, which partitions to the γ(f.c.c.)-phase, decreases the partitioning of Ni and increases the partitioning of Al and Cr. The temporal evolution of the average radius, ⟨R(t)⟩, number density, volume fraction of the γ‧(L12)-precipitates, and the supersaturations of Ni, Al, Cr, and Ru in the γ(f.c.c.)- and γ‧(L12)-phases are compared in detail with predictions of coarsening models and PrecipiCalc simulations. Based on a spline function fitting procedure of the concentration profiles between the γ‧(L12)- and γ(f.c.c.)-phases, it is demonstrated that the temporal evolution of the normalized interfacial width, δ/⟨R(t)⟩ vs. ⟨R(t)⟩, of each element, decreases with increasing ageing time: δ is the interfacial width.

  2. Vibrational structure of luminiscence spectrum of Cr3+ in MgAl2O4

    NASA Astrophysics Data System (ADS)

    Czaja, M.; Mazurak, Z.

    1993-07-01

    The optical absorption and luminescence spectra of MgAl2O4:Cr3+ natural spinel (from Ural) have been measured at 77 K and 293 K. The luminescent emission from 4 T 2 g , 2 E g covers wide region of 600 750 nm. The emission spectrum at 77 K shows a very rich vibrational structure which can be mainly explained through the vibrational modes of the oxygen octahedron.

  3. Tribological Properties of CrN/AlN Films Produced by Reactive Magnetron Sputtering

    NASA Astrophysics Data System (ADS)

    Rojo, A.; Solís, J.; Oseguera, J.; Salas, O.; Reichelt, R.

    2010-04-01

    The microstructure of CrN/AlN films, prepared by reactive magnetron sputtering under various conditions, was analyzed and related to the wear behavior of the films. One set of films was prepared by conventional reactive magnetron sputtering, a second set adding an extra amount of reactive gas to the initial Ar + N2 mixture and a third set adding an extra source of nitrogen near the substrate during sputtering. The samples were analyzed by scanning electron microscopy + energy dispersive microanalysis, high resolution scanning electron microscopy, atomic force microscopy, and x-ray diffraction. The results of the microstructural analysis revealed a clear difference in the morphology growth of the films when extra nitrogen was used compared to the conventionally prepared films. Formation of CrN was significantly faster than that of AlN. The most effective method to produce AlN was to introduce extra nitrogen. Pin-on-disk wear experiments were carried out in ambient air, to investigate the tribological behavior of the CrN/AlN system against a steel ball under dry conditions for various loads and a constant sliding speed. The results revealed that tribological properties of the layers improved unlike those of the untreated H13 steel. The friction behavior is closely related to the structure of the deposited films. The thicker CrN layer contributed to the higher load capacity of the coated steel when compared to the unmodified steel. However, wear life for the coating system was very short, denoted by the fairly poor adhesion of the film system to the steel substrate.

  4. Reactivity of Ti-B, Cr-S, and Mn-S powder systems during explosively-driven collapse

    NASA Astrophysics Data System (ADS)

    Serge, Matthew; Nabavi, Atefeh; Chiu, Po-Hsun; Higgins, Andrew; Nesterenko, Vitali

    2013-06-01

    Metal-metal and metal-sulfur reactive powder mixtures have been previously tested for initiation of reaction via planar, normal-shock loading. In addition to reacting under shock, such powder mixtures may undergo exothermic reaction under other types of mechanical loading. The thick-walled cylinder (TWC) technique was performed on samples of Ti-B (1:2 molar ratio), Cr-S (1.15:1 molar ratio), and Mn-S (1:1 molar ratio). These experiments were performed to determine the effect of large shear strains exerted on reactive metal powder mixtures and to establish the relative effectiveness of shear loading in comparison to shock loading in initiating reaction. Recovered samples were analyzed via SEM and XRD to determine the degree of reaction. Funding was provided in part by ONR MURI N00014-07-1-0740 (Program Officer Dr. Clifford Bedford).

  5. Reactivity of Ti-B, Cr-S, and Mn-S powder systems during explosively-driven collapse

    NASA Astrophysics Data System (ADS)

    Serge, M.; Chiu, P. H.; Higgins, A. J.; Nesterenko, V. F.

    2014-05-01

    Metal-metal and metal-sulfur reactive powder mixtures have been previously tested for initiation of reaction via planar, normal-shock loading. In addition to reacting under shock, such powder mixtures may undergo exothermic reaction from other types of mechanical loading. The thick-walled cylinder technique was performed on samples of Ti-B (1:2 molar ratio), Cr-S (1.15:1 molar ratio), and Mn-S (1:1 molar ratio). These experiments were aimed to determine the effect of large shear strains exerted on reactive metal powder mixtures and to establish the relative effectiveness of shear loading in comparison to shock loading for initiating reaction. Recovered samples were analyzed via SEM and XRD to determine the degree of reaction.

  6. Magnetism, structures and stabilities of cluster assembled TM@Si nanotubes (TM = Cr, Mn and Fe): a density functional study.

    PubMed

    Dhaka, Kapil; Bandyopadhyay, Debashis

    2016-08-01

    The present study reports transition metal (TM = Cr, Mn and Fe) doped silicon nanotubes with tunable band structures and magnetic properties by careful selection of cluster assemblies as building blocks using the first-principles density functional theory. We found that the transition metal doping and in addition, the hydrogen termination process can stabilize the pure silicon nanoclusters or cluster assemblies and then it could be extended as magnetic nanotubes with finite magnetic moments. Study of the band structures and density of states (DOS) of different empty and TM doped nanotubes (Type 1 to Type 4) show that these nanotubes are useful as metals, semiconductors, semi-metals and half-metals. These designer magnetic materials could be useful in spintronics and magnetic devices of nanoscale order. PMID:27430742

  7. Magnetic anisotropy of Fe1-yXyPt-L10 [X = Cr, Mn, Co, Ni, Cu] bulk alloys

    NASA Astrophysics Data System (ADS)

    Cuadrado, R.; Klemmer, Timothy J.; Chantrell, R. W.

    2014-10-01

    We demonstrate by means of fully relativistic first principles calculations that, by substitution of Fe by Cr, Mn, Co, Ni, or Cu in FePt-L10 bulk alloys, with fixed Pt content, it is possible to tune the magnetocrystalline anisotropy energy by adjusting the content of the non-magnetic species in the material. The changes in the geometry due to the inclusion of each element induces different values of the tetragonality and hence changes in the magnetic anisotropy and in the net magnetic moment. The site resolved magnetic moments of Fe increase with the X content while those of Pt and X are simultaneously reduced. The calculations are in good quantitative agreement with experimental data and demonstrate that models with fixed band structure but varying numbers of electrons per unit cell are insufficient to describe the experimental data for doped FePt-L10 alloys.

  8. Oxidation and Hot Corrosion Behavior of Plasma-Sprayed MCrAlY-Cr2O3 Coatings

    NASA Astrophysics Data System (ADS)

    Zhang, Tiantian; Huang, Chuanbing; Lan, Hao; Du, Lingzhong; Zhang, Weigang

    2016-08-01

    The oxidation and hot corrosion behavior of two atmospheric plasma-sprayed NiCoCrAlY-Cr2O3 and CoNiCrAlY-Cr2O3 coatings, which are primarily designed for wear applications at high temperature, were investigated in this study. The two coatings were exposed to air and molten salt (75%Na2SO4-25%NaCl) environment at 800 °C under cyclic conditions. Oxidation and hot corrosion kinetic curves were obtained by thermogravimetric technique. X-ray diffraction analysis and scanning electron microscopy with energy-dispersive x-ray spectrometry were employed to characterize the coatings' microstructure, surface oxides, and composition. The results showed that both coatings provided the necessary oxidation resistance with oxidation rates of about 1.03 × 10-2 and 1.36 × 10-2 mg/cm2 h, respectively. The excellent oxidation behavior of these two coatings is attributed to formation of protective (Ni,Co)Cr2O4 spinel on the surface, while as-deposited Cr2O3 in the coatings also acted as a barrier to diffusion of oxidative and corrosive substances. The greater presence of Co in the CoNiCrAlY-Cr2O3 coating restrained internal diffusion of sulfur and slowed down the coating's degradation. Thus, the CoNiCrAlY-Cr2O3 coating was found to be more protective than the NiCoCrAlY-Cr2O3 coating under hot corrosion condition.

  9. TEM and SNMS studies of protective alumina scales on NiCrAlY-alloys.

    PubMed

    Clemens, D; Vosberg, V; Hobbs, W; Breuer, U; Quadakkers, W J; Nickel, H

    1996-06-01

    The effect of Si addition on the oxidation behaviour of NiCrAlY alloys in the temperature range 950 bis 1100 degrees C has been investigated. During isothermal oxidation oxide growth rates were practically independent of the Si-content. However during cyclic oxidation Si additions were beneficial. Si additions of 1-2(m)/(0) appeared to shift the onset for spallation to longer times. It was found that Si stabilizes the beta-phase and probably it suppresses the formation of metastable Al(2)O(3) modifications. PMID:15045347

  10. Effects of Solute Concentrations on Kinetic Pathways in Ni-Al-Cr Alloys

    NASA Technical Reports Server (NTRS)

    Booth-Morrison, Christopher; Weninger, Jessica; Sudbrack, Chantal K.; Mao, Zugang; Seidman, David N.; Noebe, Ronald D.

    2008-01-01

    The kinetic pathways resulting from the formation of coherent gamma'-precipitates from the gamma-matrix are studied for two Ni-Al-Cr alloys with similar gamma'-precipitate volume fractions at 873 K. The details of the phase decompositions of Ni-7.5Al-8.5Cr at.% and Ni-5.2Al-14.2Cr at.% for aging times from 1/6 to 1024 h are investigated by atom-probe tomography, and are found to differ significantly from a mean-field description of coarsening. The morphologies of the gamma'-precipitates of the alloys are similar, though the degrees of gamma'-precipitate coagulation and coalescence differ. Quantification within the framework of classical nucleation theory reveals that differences in the chemical driving forces for phase decomposition result in differences in the nucleation behavior of the two alloys. The temporal evolution of the gamma'-precipitate average radii and the gamma-matrix supersaturations follow the predictions of classical coarsening models. The compositional trajectories of the gamma-matrix phases of the alloys are found to follow approximately the equilibrium tie-lines, while the trajectories of the gamma'-precipitates do not, resulting in significant differences in the partitioning ratios of the solute elements.

  11. Fe-Cr-Al containing oxide semiconductors as potential solar water-splitting materials.

    PubMed

    Sliozberg, Kirill; Stein, Helge S; Khare, Chinmay; Parkinson, Bruce A; Ludwig, Alfred; Schuhmann, Wolfgang

    2015-03-01

    A high-throughput thin film materials library for Fe-Cr-Al-O was obtained by reactive magnetron cosputtering and analyzed with automated EDX and XRD to elucidate compositional and structural properties. An automated optical scanning droplet cell was then used to perform photoelectrochemical measurements of 289 compositions on the library, including electrochemical stability, potentiodynamic photocurrents and photocurrent spectroscopy. The photocurrent onset and open circuit potentials of two semiconductor compositions (n-type semiconducting: Fe51Cr47Al2Ox, p-type semiconducting Fe36.5Cr55.5Al8Ox) are favorable for water splitting. Cathodic photocurrents are observed at 1.0 V vs RHE for the p-type material exhibiting an open circuit potential of 0.85 V vs RHE. The n-type material shows an onset of photocurrents at 0.75 V and an open circuit potential of 0.6 V. The p-type material showed a bandgap of 1.55 eV, while the n-type material showed a bandgap of 1.97 eV. PMID:25650842

  12. Studies of a Large Odd‐Numbered Odd‐Electron Metal Ring: Inelastic Neutron Scattering and Muon Spin Relaxation Spectroscopy of Cr8Mn

    PubMed Central

    Lancaster, Tom; Chiesa, Alessandro; Amoretti, Giuseppe; Baker, Peter J.; Barker, Claire; Carretta, Stefano; Collison, David; Güdel, Hans U.; Guidi, Tatiana; McInnes, Eric J. L.; Möller, Johannes S.; Mutka, Hannu; Ollivier, Jacques; Pratt, Francis L.; Santini, Paolo; Tuna, Floriana; Tregenna‐Piggott, Philip L. W.; Vitorica‐Yrezabal, Iñigo J.; Timco, Grigore A.

    2016-01-01

    Abstract The spin dynamics of Cr8Mn, a nine‐membered antiferromagnetic (AF) molecular nanomagnet, are investigated. Cr8Mn is a rare example of a large odd‐membered AF ring, and has an odd‐number of 3d‐electrons present. Odd‐membered AF rings are unusual and of interest due to the presence of competing exchange interactions that result in frustrated‐spin ground states. The chemical synthesis and structures of two Cr8Mn variants that differ only in their crystal packing are reported. Evidence of spin frustration is investigated by inelastic neutron scattering (INS) and muon spin relaxation spectroscopy (μSR). From INS studies we accurately determine an appropriate microscopic spin Hamiltonian and we show that μSR is sensitive to the ground‐spin‐state crossing from S=1/2 to S=3/2 in Cr8Mn. The estimated width of the muon asymmetry resonance is consistent with the presence of an avoided crossing. The investigation of the internal spin structure of the ground state, through the analysis of spin‐pair correlations and scalar‐spin chirality, shows a non‐collinear spin structure that fluctuates between non‐planar states of opposite chiralities. PMID:26748964

  13. Studies of a Large Odd-Numbered Odd-Electron Metal Ring: Inelastic Neutron Scattering and Muon Spin Relaxation Spectroscopy of Cr8 Mn.

    PubMed

    Baker, Michael L; Lancaster, Tom; Chiesa, Alessandro; Amoretti, Giuseppe; Baker, Peter J; Barker, Claire; Blundell, Stephen J; Carretta, Stefano; Collison, David; Güdel, Hans U; Guidi, Tatiana; McInnes, Eric J L; Möller, Johannes S; Mutka, Hannu; Ollivier, Jacques; Pratt, Francis L; Santini, Paolo; Tuna, Floriana; Tregenna-Piggott, Philip L W; Vitorica-Yrezabal, Iñigo J; Timco, Grigore A; Winpenny, Richard E P

    2016-01-26

    The spin dynamics of Cr8 Mn, a nine-membered antiferromagnetic (AF) molecular nanomagnet, are investigated. Cr8 Mn is a rare example of a large odd-membered AF ring, and has an odd-number of 3d-electrons present. Odd-membered AF rings are unusual and of interest due to the presence of competing exchange interactions that result in frustrated-spin ground states. The chemical synthesis and structures of two Cr8 Mn variants that differ only in their crystal packing are reported. Evidence of spin frustration is investigated by inelastic neutron scattering (INS) and muon spin relaxation spectroscopy (μSR). From INS studies we accurately determine an appropriate microscopic spin Hamiltonian and we show that μSR is sensitive to the ground-spin-state crossing from S=1/2 to S=3/2 in Cr8 Mn. The estimated width of the muon asymmetry resonance is consistent with the presence of an avoided crossing. The investigation of the internal spin structure of the ground state, through the analysis of spin-pair correlations and scalar-spin chirality, shows a non-collinear spin structure that fluctuates between non-planar states of opposite chiralities. PMID:26748964

  14. Strong pressure dependences of the magnetization and Curie temperature for CrTe and MnAs with NiAs-type structure

    NASA Astrophysics Data System (ADS)

    Yamada, H.; Terao, K.; Kondo, K.; Goto, T.

    2002-11-01

    To study the strong magneto-volume effects observed in CrTe and MnAs with NiAs-type crystal structure, first-principle band calculations are carried out by a self-consistent linear muffin-tin orbital method within the atomic sphere approximation. The equilibrium volume of the unit cell is obtained as a function of the magnetization M, which gives the volume magnetostriction. The dependence on M of the bulk modulus is also estimated. The coefficients a0 and b0 in the Landau expansion, ΔE(M) = a0 M2 /2 + b 0 M4 /4, are estimated by the fixed-spin-moment method. The calculated results for CrTe and MnAs are compared with those for bcc Fe. It is shown that the values of |a0 | and b0 for CrTe and MnAs are so small that the correction term from the magneto-volume coupling constants becomes significant. This fact gives a strong pressure dependence of the spontaneous magnetization. The pressure dependence of the Curie temperature is also discussed by making use of the magneto-volume coupling constants estimated in the present paper. The large volume magnetostriction observed in CrTe and MnAs is explained by the present calculations.

  15. Dielectric relaxation and magnetodielectric response in DyMn{sub 0.5}Cr{sub 0.5}O{sub 3}

    SciTech Connect

    Yuan, B.; Yang, J. Zuo, X. Z.; Zhu, X. B.; Dai, J. M.; Song, W. H.; Kan, X. C.; Zu, L.; Sun, Y. P.

    2015-09-28

    We investigate the structural, magnetic, and magnetodielectric properties of DyMn{sub 0.5}Cr{sub 0.5}O{sub 3}. The sample can be indexed with an orthorhombic phase with B site disordered space group Pbnm. The valence state of both Mn and Cr ions are suggested to be +3 based on the results of x-ray photoelectron spectroscopy. Two thermally excited dielectric relaxation at temperatures T{sub N2} < T< 300 K and large magnetodielectric effect (MDC = 20%–30%) due to the disordered arrangement of Mn{sup 3+}/Cr{sup 3+} ions associated with electron hopping between them are observed. The absence of any noticeable magnetoresistance effect (MR < 0.5%) demonstrates that the observed magnetodielectric effect is an intrinsic behavior. These results suggest that DyMn{sub 0.5}Cr{sub 0.5}O{sub 3} is a magnetodielectric compound, whose dielectric properties are dependence of the applied magnetic field, which exhibits such effects near room temperature and holds great promise for future device applications.

  16. Effects of Oral Administration of CrCl3 on the Contents of Ca, Mg, Mn, Fe, Cu, and Zn in the Liver, Kidney, and Heart of Chicken.

    PubMed

    Liu, Yanhan; Zhao, Xiaona; Zhang, Xiao; Zhao, Xuejun; Liu, Yongxia; Liu, Jianzhu

    2016-06-01

    This study aimed to investigate the effects of oral administration of trivalent chromium on the contents of Ca, Mg, Mn, Fe, Cu, and Zn in the heart, liver, and kidney. Different levels of 1/8, 1/4, and 1/2 LD50 (LD50 = 5000 mg/kg body mass) CrCl3 milligrams per kilogram body mass daily were added into the water to establish the chronic poisoning model. Ca, Mg, Mn, Fe, Cu, and Zn were detected with the flame atomic absorption spectrometry in the organs exposed 14, 28, and 42 days to CrCl3, respectively. Results showed that Cr was accumulated in the heart, liver, and kidney significantly (P < 0.05) with extended time and dose. The contents of Ca and Fe increased, whereas those of Mg, Mn, Cu, and Zn decreased in the heart, liver, and kidney of each treated group, which had a dose- and time-dependent relationship, but the contents of Mg and Zn in the heart took on a fluctuated change. These particular observations were different from those in the control group. In conclusion, the oral administration of CrCl3 could change the contents of Ca, Mg, Mn, Fe, Cu, and Zn in the heart, liver, and kidney, which may cause disorders in the absorption and metabolism of the metal elements of chickens. PMID:26537118

  17. Electrical properties of ferromagnetic Ni{sub 2}MnGa and Co{sub 2}CrGa Heusler alloys

    SciTech Connect

    Kourov, N. I. Marchenkov, V. V.; Pushin, V. G.; Belozerova, K. A.

    2013-07-15

    The electrical properties of ferromagnetic Ni{sub 2}MnGa and Co{sub 2}CrGa Heusler alloys are measured in the temperature range 4-900 K. The effect of the energy gap near the Fermi level in the electronic spectrum on the behavior of electrical resistivity and absolute differential thermopower is discussed.

  18. Weathering and precipitation after meteorite impact of Ni, Cr, Fe, Ca and Mn in K-T boundary clays from Stevns Klint

    NASA Astrophysics Data System (ADS)

    Miyano, Yumiko; Yoshiasa, Akira; Tobase, Tsubasa; Isobe, Hiroshi; Hongu, Hidetomo; Okube, Maki; Nakatsuka, Akihiko; Sugiyama, Kazumasa

    2016-05-01

    Ni, Cr, Fe, Ca and Mn K-edge XANES and EXAFS spectra were measured on K-T boundary clays from Stevns Klint in Denmark. According to XANES spectra and EXAFS analyses, the local structures of Ni, Cr and Fe in K-T boundary clays is similar to Ni(OH)2, Cr2O3 and FeOOH, respectively. It is assumed that the Ni, Cr and Fe elements in impact related glasses is changing into stable hydrate and oxide by the weathering and diagenesis at the surface of the Earth. Ca in K-T boundary clays maintains the diopside-like structure. Local structure of Ca in K-T clays seems to keep information on the condition at meteorite impact. Mn has a local structure like MnCO3 with divalent state. It is assumed that the origin on low abundant of Mn in the Fe-group element in K-T clays was the consumption by life activity and the diffusion to other parts.

  19. Development of a focused ultrasound-assisted extraction method for the determination of trace concentrations of Cr and Mn in pharmaceutical formulations by ETAAS.

    PubMed

    de Paula, Carlos Eduardo R; Caldas, Luiz Fernando S; Brum, Daniel M; Cassella, Ricardo J

    2013-02-23

    This paper reports the development of a new method for the focused ultrasound extraction of Cr and Mn from pharmaceutical formulations and their determination by electrothermal atomic absorption spectrometry (ETAAS). The method was optimized by evaluating the influence of several variables such as the sonication power and time, concentration of HCl in the extractant solution and mass of sample employed in the extraction procedure. The curves of pyrolysis and atomization were constructed for both analytes in order to evaluate the effect of the matrix on the measurement of Cr and Mn. Quantitative extraction of both Cr and Mn was achieved when 25-150 mg of the sample were sonicated for 30 min at 50% power with 5 ml of a 1 moll(-1) HCl solution. The developed method was successfully applied in the determination of Cr and Mn in samples of pharmaceutical formulations containing different active principles such as ciprofloxacin, cephalexin, azithromycin, amlodipine and methionine. There was no statistical (95% confidence level, paired t-test) difference between the results obtained by the proposed method and the results obtained after total digestion of the samples. PMID:23245262

  20. Multiferroic approach for Cr,Mn,Fe,Co,Ni,Cu substituted BaTiO3 nanoparticles

    NASA Astrophysics Data System (ADS)

    Verma, Kuldeep Chand; Kotnala, R. K.

    2016-05-01

    Multiferroic magnetoelectric (ME) at room temperature is significant for new design nano-scale spintronic devices. We have given a comparative study to report multiferroicity in BaTM0.01Ti0.99O3 [TM = Cr,Mn,Fe,Co,Ni,Cu (1 mol% each) substituted BaTiO3 (BTO)] nanoparticles. The TM ions influenced both nano-size and lattice distortion of Ti–O6 octahedra to the BTO. X ray diffraction study indicates that the dopant TM could influence lattice constants, distortion, tetragonal splitting of diffraction peaks (002/200) as well as peak shifting of diffraction angle in the BTO lattice. This can induce lattice strain which responsible to oxygen defects formation to mediate ferromagnetism. Also, the lattice strain effect could responsible to reduce the depolarization field of ferroelectricity and provide piezoelectric and magnetostrictive strains to enhance ME coupling. The size of BTO nanoparticles is varied in 13–51 nm with TM doping. The room temperature magnetic measurement indicates antiferromagnetic exchange interactions in BTO lattice with TM ions. The zero-field cooling and field cooling magnetic measurement at 500 Oe indicates antiferromagnetic to ferromagnetic transition. It also confirms that the substitution of Cr, Fe and Co into BTO could induce strong antiferromagnetic behavior. However, the substitutions of Mn, Ni and Cu have weak antiferromagnetic character. The temperature dependent dielectric measurements indicates polarization enhancement that influenced with both nano-size as well TM ions and exhibits ferroelectric phase transition with relaxor-like characteristics. Dynamic ME coupling is investigated, and the longitudinal ME voltage coefficient, α ME is equivalent to linear ME coupling coefficient, α (={\\varepsilon }{{o}}{\\varepsilon }{{r}}{α }{{ME}}) is also calculated.

  1. Effect of Pre-straining on the Shape Recovery of Fe-Mn-Si-Cr-Ni Shape Memory Alloys

    NASA Astrophysics Data System (ADS)

    Maji, Bikas C.; Krishnan, Madangopal; Verma, Amit; Basu, R.; Samajdar, I.; Ray, Ranjit K.

    2015-02-01

    The effect of pre-straining on the shape recovery behavior of Fe-14Mn-6Si-9Cr-5Ni (wt pct) shape memory alloy (SMA) has been studied. The shape recovery associated with the reverse ɛ martensitic transformation, i.e., ɛ → γ, was characterized by dilatometry using specimens which were pre-strained to different extent (0 to 14 pct). Dilatometric studies revealed that in Fe-Mn-Si-Cr-Ni SMA, the shape recovery takes place in two stages: (i) in the first stage, the unpinned fraction of stress-induced ɛ martensite reverts back to parent phase γ in the temperature regime of 353 K to 653 K (80 °C to 380 °C) and (ii) in the second stage the remaining "pinned" ɛ martensite is unpinned by the decomposition of deformation-induced α' martensite in the temperature range of 743 K to 893 K (470 °C to 620 °C). The amount of recovery in the first stage decreases with pre-strain, whereas it increases in the second stage. The ɛ → γ transformation finish temperature, A f, increases with increase in pre-strain amount, though the reverse transformation start temperature, A S, remains unaffected. Microstructural characterization revealed that the amount of deformation-induced α' martensite depends on the mode of straining and the crystallographic texture of the starting material. The reversion of α' martensite is seen to occur by the precipitation of Fe5Ni3Si2-type intermetallic π-phase within these plates.

  2. Effect of hydrogen on internal friction and Young`s modulus of Fe-Cr-Mn austenitic stainless steel

    SciTech Connect

    Usui, Makoto; Asano, Shigeru

    1996-06-01

    The internal friction technique has so far been applied to studies on hydrogen behavior in iron and steel. The hydrogen cold-work peak is well known for pure iron and has also been observed in BCC iron alloys such as ferritic stainless steel and maraging steel. It provides important information about the hydrogen- dislocation interaction in the BCC iron lattice. Meanwhile, for FCC iron alloys such as austenitic stainless steel, another characteristic hydrogen internal friction peak has been found by authors` group and confirmed by several other investigators. In the present study, type 205 austenitic stainless steel (Fe-17Cr-15Mn) was chosen as a nickel-free FCC iron alloy, in which manganese is totally substituted for nickel in type 304 steel. This steel has an unstable FCC lattice as is the case of type 304 steel, in which hydrogen-induced phase transformation depends on the austenite stability. However, the present steel was confirmed to form the {var_epsilon}{sub H} phase after cathodic hydrogen charging in a similar manner to the stable FCC lattice of type 310 steel. In addition, the Fe-Cr-Mn alloy shows a marked anomaly in the temperature dependence of Young`s modulus: an abrupt drop near the Neel temperature T{sub N} and successive lowering below T{sub N}, as has been reported in the literature for some antiferromagnetic materials. The effect of hydrogen on Young`s modulus was studied by several investigators, but there was great inconsistency among their experimental results. The purpose of this paper is to confirm the hydrogen peak of internal friction in type 205 steel and to examine the effect of hydrogen on Young`s modulus of this steel.

  3. Grain-size control in Ti-48Al-2Cr-2Nb with yttrium additions

    NASA Astrophysics Data System (ADS)

    Trivedi, P. B.; Patankar, S. N.; (Sam) Froes, F. H.; Baburaj, E. G.; Genç, A.; Ovecoglu, L.

    2002-08-01

    A gas-atomized (GA) prealloyed powder of the Ti-48Al-2Cr-2Nb intermetallic and 1.6 wt pct Y were mechanically alloyed (MA) and hot isostatically pressed (hipped) to produce a fully dense nanocrystalline material. Mechanical alloying of the as-blended powder for 16 hours resulted in the formation of a disordered fcc phase. Hipping of the alloy powder produced a single-phase nanocrystalline TiAl intermetallic, containing a distribution of 20 to 35-nm-sized Al2Y4O9 particles. The formation of oxide particles occurred by the chemical combination of Al and Y with oxygen, which entered as a contaminant during milling. Oxide particles increased the hardness of the intermetallic compound and minimized grain growth even at 0.8 T m , where T m is the melting point of the compound.

  4. Analysis of the microstructure of Cr-Ni surface layers deposited on Fe{sub 3}Al by TIG

    SciTech Connect

    Ma Haijun . E-mail: hjma123@mail.sdu.edu.cn; Li Yajiang; Wang Juan

    2006-12-15

    A series of Cr-Ni alloys were overlaid on a Fe{sub 3}Al surface by tungsten inert gas arc welding (TIG) technology. The microstructure of the Cr-Ni surface layers were analysed by means of optical metallography, scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results indicated that when the appropriate TIG parameters were used and Cr25-Ni13 and Cr25-Ni20 alloys were used for the overlaid materials, the Cr-Ni surface layers were crack-free. The matrix of the surface layer was austenite (A), pro-eutectoid ferrite (PF), acicular ferrite (AF), carbide-free bainite (CFB) and lath martensite (LM), distributed on the austenitic grain boundaries as well as inside the grains. The phase constituents of the Cr25-Ni13 surface layer were {gamma}-Fe, Fe{sub 3}Al, FeAl, NiAl, an Fe-C compound and an Fe-C-Cr compound. The microhardness of the fusion zone was lower than that of the Fe{sub 3}Al base metal and Cr25-Ni13 surface layer.

  5. Effect of Ca addition on the corrosion behavior of Mg-Al-Mn alloy

    NASA Astrophysics Data System (ADS)

    Yang, Jiang; Peng, Jian; Nyberg, Eric A.; Pan, Fu-sheng

    2016-04-01

    The microstructures and corrosion resistance of magnesium-5 wt% aluminum-0.3 wt% manganese alloys (Mg-Al-Mn) with different Ca additions (0.2-4 wt%) were investigated. Results showed that with increasing Ca addition, the grain of the alloys became more refined, whereas the corrosion resistant ability of the alloys initially increased and then decreased. The alloy with 2 wt% Ca addition exhibited the best corrosion resistance, attributed to the effect of the oxide film and (Mg,Al)2Ca phases which were discontinuously distributed on the grain boundaries. These phases acted as micro-victims, they preferentially corroded to protect the α-Mg matrix. The oxide film formed on the alloy surface can hinder the solution further to protect the α-Mg matrix.

  6. Electron Paramagnetic Resonance and Photoluminescence Studies of LaMgAl11O19:Mn2+ Green Phosphors

    NASA Astrophysics Data System (ADS)

    Singh, Vijay; Chakradhar, R. P. S.; Rao, J. L.; Dhoble, S. J.; Kim, S. H.

    2014-09-01

    Manganese-doped LaMgAl11O19 powder has been prepared by an easy combustion method. Powder x-ray diffraction and scanning electron microscopy have been used to characterize the as-prepared phosphor. The electron paramagnetic resonance (EPR) spectrum of LaMgAl11O19:Mn2+ phosphor exhibits six-line hyperfine structure centered at g ≈ 1.973. The number of spins participating in resonance (N) and the paramagnetic susceptibility (χ) for the resonance signal at g ≈ 1.973 have been calculated as a function of temperature. The photoluminescence spectrum exhibits green emission at 516 nm, which is attributed to 4T1 → 6A1 transition of Mn2+ ions. From EPR and luminescence studies, it is observed that Mn2+ ions occupy Mg2+ sites and Mn2+ ions are located at tetrahedral sites in the prepared phosphors.

  7. Observation of the TWIP + TRIP Plasticity-Enhancement Mechanism in Al-Added 6 Wt Pct Medium Mn Steel

    NASA Astrophysics Data System (ADS)

    Lee, Seawoong; Lee, Kyooyoung; De Cooman, Bruno C.

    2015-06-01

    The intercritically annealed Fe-0.15 pctC-6.0 pctMn-1.5 pctSi-3.0 pctAl and Fe-0.30 pctC-6.0 pctMn-1.5 pctSi-3.0 pctAl medium Mn steels were found to have improved mechanical properties due to the TWIP and TRIP plasticity-enhancing mechanisms being activated in succession during tensile deformation. The increase of the C content from 0.15 to 0.30 pct resulted in ultra-high strength properties and a strength-ductility balance of approximately 65,000 MPa-pct, i.e., equivalent to the strength-ductility balance of high Mn TWIP steel with a fully austenitic microstructure.

  8. Structural, magnetic and phonon properties of Cr(III)-doped perovskite metal formate framework [(CH3)2NH2][Mn(HCOO)3

    NASA Astrophysics Data System (ADS)

    Mączka, Mirosław; Gągor, Anna; Hermanowicz, Krzysztof; Sieradzki, Adam; Macalik, Lucyna; Pikul, Adam

    2016-05-01

    We have incorporated Cr(III) into [(CH3)2NH2][Mn(HCOO)3] (DMMn) multiferroic metal organic framework (MOF). The highest concentration of Cr(III) in the synthesized samples reached 15.9 mol%. The obtained samples were characterized by powder and single-crystal X-ray diffraction, DSC, magnetic susceptibility, dielectric, EPR, Raman and IR methods. These methods and the performed chemical analysis revealed that electrical charge neutrality after substitution of Cr(III) for Mn(II) is maintained by partial replacement of dimethylammonium (DMA+) cations by neutral HCOOH molecules. These changes in the chemical composition are responsible for weakening of the hydrogen bonds and decreased flexibility of the framework. This in turn leads to lowering of the ferroelectric phase transition temperature, observed around 185 K for undoped DMMn and around 155 K for the sample containing 3.1 mol% of Cr(III), and lack of macroscopic phase transition for the samples with Cr(III) content of 8.2 and 15.9 mol %. Another interesting effect observed for the studied samples is pronounced strengthening of the weak ferromagnetism of in Cr(III)-doped samples, associated with slight decrease of the ferromagnetic ordering temperature from 8.5 K for DMMn to 7.0 K for the sample with 15.9 mol % Cr(III) content.

  9. Origin of mechanoluminescence from Mn-activated ZnAl2 O4 : Triboelectricity-induced electroluminescence

    NASA Astrophysics Data System (ADS)

    Matsui, Hiroaki; Xu, Chao-Nan; Liu, Yun; Tateyama, Hiroshi

    2004-06-01

    Luminescence induced by friction, mechanoluminescence (ML) has been observed for ZnAl2 O4 : Mn2+ ( ZAO:Mn ) fabricated by systematically controlling the reducing temperature. The reducing treatment produced lattice defects under a reducing atmosphere. Those defects were associated with Zn and O vacancies through evaporation of ZnO in ZnAl2 O4 , which was trapped with a large amount of carrier in the spinel. Results of dependence of ML intensity and integrated intensity for thermoluminescence on the reducing temperature showed that the trapped carrier plays an important role in producing the ML for ZAO:Mn . In addition, the ML for ZAO:Mn was strongly dependent upon the friction rod material; it was closely related to the surface voltage generated in the vicinity of the frictional surface. These results suggest that the ML for ZAO:Mn was caused by the effect of triboelectrification, but not piezoelectricity because ZnAl2 O4 has a centrosymmetric structure (Fd3m) . Therefore, the carrier that is trapped in the spinel can be excited by the local electric field derived from friction between the two dissimilar materials, where the excited carrier is accelerated toward the luminescent center of the Mn2+ ions. Consequently, the Mn2+ ions are excited and release an emission band on the transition from 4T1 to 6A1 . Evidence for these physical processes was corroborated from the finding that reduced ZAO:Mn showed highly efficient electroluminescence (EL). Therefore, it is inferred that the ML for ZAO:Mn is caused by triboelectricity-induced EL .

  10. Ab Initio Characterization of the Electrostatic Complexes Formed by H2 Molecule and Cr(+), Mn(+), Cu(+), and Zn(+) Cations.

    PubMed

    Artiukhin, Denis G; Bieske, Evan J; Buchachenko, Alexei A

    2016-07-14

    Equilibrium structures, dissociation energies, and rovibrational energy levels of the electrostatic complexes formed by molecular hydrogen and first-row S-state transition metal cations Cr(+), Mn(+), Cu(+), and Zn(+) are investigated ab initio. Extensive testing of the CCSD(T)-based approaches for equilibrium structures provides an optimal scheme for the potential energy surface calculations. These surfaces are calculated in two dimensions by keeping the H-H internuclear distance fixed at its equilibrium value in the complex. Subsequent variational calculations of the rovibrational energy levels permits direct comparison with data obtained from equilibrium thermochemical and spectroscopic measurements. Overall accuracy within 2-3% is achieved. Theoretical results are used to examine trends in hydrogen activation, vibrational anharmonicity, and rotational structure along the sequence of four electrostatic complexes covering the range from a relatively floppy van der Waals system (Mn(+)···H2) to an almost a rigid molecular ion (Cu(+)···H2). PMID:26914616

  11. Hydrogen reduction of wustite single crystals doped with Mg, Mn, Ca, Al, and Si

    NASA Astrophysics Data System (ADS)

    Moukassi, M.; Gougeon, M.; Steinmetz, P.; Dupre, B.; Gleitzer, C.

    1984-06-01

    In order to investigate the reduction mechanism of wustite in the presence of impurities usually met in the ironmaking industry, single crystals have been prepared with Mg, Mn, Ca, Al, and Si as dopants. The amounts of dopant in the lattice is around 4,4,2.5,0.5, and 0.01 mol pct, respectively, at 800 ‡C. For reduction with pure hydrogen, from 600 to 950 ‡C, Ca is the most efficient for accelerating the process at high degrees of reduction (75 pct) Mg and Mn are also active in this respect. Al has only a slowing down effect. Si also slows down the reaction at temperatures between 600 < T < 850 ‡C, but it becomes accelerating at T > 850 ‡C. In the presence of 20 torrs of water vapor in the gas, Mg and Mn are less efficient and unable to prevent the same slowing down of reaction observed with pure wustite at around 850 ‡C and classically called the ‡rate minimum‡. Our interpretation of these results is mainly based upon the observations of microstructures of partly reduced crystals which show a change in the texture of the iron produced which can be correlated with the reduction rate. These observations lead to a possible explanation in terms of the role of inclusions of impurity oxides on the sintering process of the metal, correlated with their ability to dissolve into the wustite lattice. However, this suggestion cannot apply in the case of Si at low temperatures, and this element is therefore supposed to play a role in the stages of reaction associated with the surface of the crystals.

  12. Formation of α-alumina scales in the Fe-Al(Cr) diffusion coating on China low activation martensitic steel

    NASA Astrophysics Data System (ADS)

    Zhan, Qin; Zhao, Weiwei; Yang, Hongguang; Hatano, Yuji; Yuan, Xiaoming; Nozaki, Teo; Zhu, Xinxin

    2015-09-01

    To study the formation mechanism of stable α-Al2O3 scales, the oxidation behavior of Fe-Al(Cr) diffusion coating on China low activation martensitic steel has been investigated under the oxygen partial pressure ranging from 1 to 20,000 Pa at 1253 K. A single, continuous Al2O3 scale with the maximum thickness of about 2000 nm was formed on the Fe-Al(Cr) diffusion layer. The phase transformation of alumina scales on the surface of Fe-Al(Cr) layer was studied at different oxidation times ranging from 3 to 180 min. With the increase in oxygen partial pressure, the phase transformation time of α-Al2O3 is decreased. The metastable γ-Al2O3 and transition α-(Al0.948Cr0.052)2O3 phases were formed in the earlier oxidation process and finally transformed to the stable α-Al2O3 phase, which were detected by grazing incidence angle X-ray diffraction and confirmed by transmission electron microscopy. This implies that Cr shows the third element effect and serves as a template for the nucleation of the stable α-Al2O3.

  13. The Solidification Mode of Fe-Mn-Al-C Lightweight Steel

    NASA Astrophysics Data System (ADS)

    Lee, Chan-Young; Lee, Young-Kook

    2014-09-01

    Solidification behavior and solid-state transformation were investigated in Fe-Mn-Al-C lightweight steel. The solidification mode of the Fe-9.3Mn-5.6Al-0.2C (wt.%) lightweight steel was predicted to be the F mode (liquid → liquid + δ-ferrite → δ-ferrite → δ-ferrite + γ-austenite), according to the classification of the solidification modes of stainless steels. However, the microstructures of an ingot of the lightweight steel showed that the solidification occurred by the FA mode (liquid → liquid + δ-ferrite → liquid + δ-ferrite + γ-austenite → δ-ferrite + γ-austenite). To examine the difference between predicted and actual solidification modes, some specimens were annealed at various temperatures ranging from 1200°C to 1450°C for 10 min and then quenched. The microstructures of the annealed specimens exhibited that there were the narrow ranges of single δ-ferrite and solidification sections. This result indicates that the solidification mode of the present steel was the F mode, matching well with the predicted solidification mode. The reason for the FA mode, which was observed in the ingot, was because the liquid passed by a narrow solidification section and a single δ-ferrite region, and it directly entered the dual-phase region of δ-ferrite and γ-austenite during cooling.

  14. Application of Cu-Al-Mn superelastic alloy bars as reinforcement elements in concrete beams

    NASA Astrophysics Data System (ADS)

    Shrestha, Kshitij C.; Araki, Yoshikazu; Nagae, Takuya; Yano, Hayato; Koetaka, Yuji; Omori, Toshihiro; Sutou, Yuji; Kainuma, Ryosuke; Ishida, Kiyohito

    2012-04-01

    Experimental works are done to assess the seismic behavior of concrete beams reinforced with superelastic alloy (SEA) bars. Applicability of newly developed Cu-Al-Mn SEA bars, characterized by large recovery strain, low material cost, and high machinability, have been proposed as partial replacements for conventional steel bars in order to reduce residual deformations in structures during and after intense earthquakes. Four-point reverse-cyclic bending tests were done on 1/3 scale concrete beams comprising three different types of specimens - conventional steel reinforced concrete (ST-RC), SEA reinforced concrete (SEA-RC), and SEA reinforced concrete with pre-tensioning (SEA-PC). The results showed that SEA reinforced concrete beams demonstrated significant enhancement in crack recovery capacity in comparison to steel reinforced beam. Average recovery of cracks for each of the specimens was 21% for ST-RC, 84% for SEA-RC, and 86% for SEA-PC. In addition, SEA-RC and SEA-PC beams demonstrated strong capability of recentering with comparable normalized strength and ductility relative to conventional ST-RC beam specimen. ST-RC beam, on the other hand, showed large residual cracks due to progressive reduction in its re-centering capability with each cycle. Both the SEA-RC and SEA-PC specimens demonstrated superiority of Cu-Al-Mn SEA bars to conventional steel reinforcing bars as reinforcement elements.

  15. Accumulative Roll Bonding and Post-Deformation Annealing of Cu-Al-Mn Shape Memory Alloy

    NASA Astrophysics Data System (ADS)

    Moghaddam, Ahmad Ostovari; Ketabchi, Mostafa; Afrasiabi, Yaser

    2014-09-01

    Accumulative roll bonding is a severe plastic deformation process used for Cu-Al-Mn shape memory alloy. The main purpose of this study is to investigate the possibility of grain refinement of Cu-9.5Al-8.2Mn (in wt.%) shape memory alloy using accumulative roll bonding and post-deformation annealing. The alloy was successfully subjected to 5 passes of accumulative roll bonding at 600 °C. The microstructure, properties as well as post-deformation annealing of this alloy were investigated by optical microscopy, scanning electron microscopy, x-ray diffraction, differential scanning calorimeter, and bend and tensile testing. The results showed that after 5 passes of ARB at 600 °C, specimens possessed α + β microstructure with the refined grains, but martensite phases and consequently shape memory effect completely disappeared. Post-deformation annealing was carried out at 700 °C, and the martensite phase with the smallest grain size (less than 40 μm) was obtained after 150 s of annealing at 700 °C. It was found that after 5 passes of ARB and post-deformation annealing, the stability of SME during thermal cycling improved. Also, tensile properties of alloys significantly improved after post-deformation annealing.

  16. Accumulative Roll Bonding and Post-Deformation Annealing of Cu-Al-Mn Shape Memory Alloy

    NASA Astrophysics Data System (ADS)

    Moghaddam, Ahmad Ostovari; Ketabchi, Mostafa; Afrasiabi, Yaser

    2014-12-01

    Accumulative roll bonding is a severe plastic deformation process used for Cu-Al-Mn shape memory alloy. The main purpose of this study is to investigate the possibility of grain refinement of Cu-9.5Al-8.2Mn (in wt.%) shape memory alloy using accumulative roll bonding and post-deformation annealing. The alloy was successfully subjected to 5 passes of accumulative roll bonding at 600 °C. The microstructure, properties as well as post-deformation annealing of this alloy were investigated by optical microscopy, scanning electron microscopy, x-ray diffraction, differential scanning calorimeter, and bend and tensile testing. The results showed that after 5 passes of ARB at 600 °C, specimens possessed α + β microstructure with the refined grains, but martensite phases and consequently shape memory effect completely disappeared. Post-deformation annealing was carried out at 700 °C, and the martensite phase with the smallest grain size (less than 40 μm) was obtained after 150 s of annealing at 700 °C. It was found that after 5 passes of ARB and post-deformation annealing, the stability of SME during thermal cycling improved. Also, tensile properties of alloys significantly improved after post-deformation annealing.

  17. Bulk Mn-Al-C permanent magnets prepared by various techniques

    NASA Astrophysics Data System (ADS)

    Madugundo, Rajasekhar; Koylu-Alkan, Ozlem; Hadjipanayis, George C.

    2016-05-01

    Bulk Mn-Al-C magnets have been prepared by hot-compaction, microwave sintering and hot-deformation. Powders of Mn53.5Al44.5C2 alloy in the ɛ-phase produced by high energy ball milling have been used as precursor for the hot-compacted and microwave sintered magnets. Hot-deformed magnets were produced from alloy pieces in the τ-phase. The hot-compacted magnet exhibits magnetization, remanence and coercivity of 50 emu/g, 28 emu/g and 3.3 kOe, respectively. Microwave sintered magnet shows a maximum magnetization of 94 emu/g, remanence of 30 emu/g and coercivity of 1.1 kOe. The best magnetic properties are obtained in hot-deformed magnets with magnetization, remanence, coercivity and energy product of 82 emu/g, 50 emu/g, 2.2 kOe and 1.8 MGOe, respectively. Hot-deformed magnets exhibit texture with the highest degree of texture obtained 0.26. It is found that the pressure applied during compaction/deformation favors coercivity.

  18. Effects of Microalloying on the Microstructures and Mechanical Properties of Directionally Solidified Ni-33(at.%)Al-31Cr-3Mo Eutectic Alloys Investigated

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. Daniel; Raj, Sai V.; Locci, Ivan E.; Salem, Jonathan A.

    2002-01-01

    Despite nickel aluminide (NiAl) alloys' attractive combination of oxidation and thermophysical properties, their development as replacements for superalloy airfoils in gas turbine engines has been largely limited by difficulties in developing alloys with an optimum combination of elevated-temperature creep resistance and room-temperature fracture toughness. Alternatively, research has focused on developing directionally solidified NiAl-based in situ eutectic composites composed of NiAl and (Cr,Mo) phases in order to obtain a desirable combination of properties a systematic investigation was undertaken at the NASA Glenn Research Center to examine the effects of small additions of 11 alloying elements (Co, Cu, Fe, Hf, Mn, Nb, Re, Si, Ta, Ti, and Zr) in amounts varying from 0.25 to 1.0 at.% on the elevated-temperature strength and room-temperature fracture toughness of directionally solidified Ni-33Al-31Cr-3Mo eutectic alloy. The alloys were grown at 12.7 mm/hr, where the unalloyed eutectic base alloy exhibited a planar eutectic microstructure. The different microstructures that formed because of these fifth-element additions are included in the table. The additions of these elements even in small amounts resulted in the formation of cellular microstructures, and in some cases, dendrites and third phases were observed. Most of these elemental additions did not improve either the elevated-temperature strength or the room-temperature fracture toughness over that of the base alloy. However, small improvements in the compression strength were observed between 1200 and 1400 K when 0.5 at.% Hf and 0.25 at.% Ti were added to the base alloy. The results of this study suggest that the microalloying of Ni-33Al-31Cr-3Mo will not significantly improve either its elevatedtemperature strength or its room-temperature fracture toughness. Thus, any improvements in these properties must be acquired by changing the processing conditions.

  19. The effect of quaternary element on the thermodynamic parameters and structure of CuAlMn shape memory alloys

    NASA Astrophysics Data System (ADS)

    Aksu Canbay, C.; Karagoz, Z.

    2013-10-01

    In this study, the Cu-based shape memory alloys were produced by arc melting. We have investigated the effects of the alloying elements on the characteristic transformation temperatures, enthalpy, entropy values, and the structure of Cu-Al-Mn ternary system. The evolution of the transformation temperatures was studied by the differential scanning calorimetry. The characteristic transformation temperatures can be controlled by the variations in the aluminum and manganese content. Additionally, the effect of magnesium and iron on the transformation temperatures and thermodynamic parameters was investigated in the Cu-Al-Mn ternary system. The addition of the magnesium decreases the characteristic transformation temperatures of the Cu-Al-Mn system, but that of the iron increases. The structural changes of the samples were studied by X-ray diffraction measurements and optical microscope observations. Due to the low solubility of the magnesium, the magnesium addition into the Cu-Al-Mn system forms precipitates in the matrix. It is evaluated that the transformation parameters of the CuAlMn shape memory alloys can be controlled by the change of the alloying elements and the weight percentages of alloying elements.

  20. The effects of annealing on the microstructure and mechanical properties of Fe28Ni18Mn33Al21

    DOE PAGESBeta

    Meng, Fanling; Qiu, Jingwen; Baker, Ian; Bei, Hongbin

    2015-08-20

    In this paper, As-cast Fe28Ni18Mn33Al21, which consists of aligned, 50 nm, (Ni, Al)-rich B2, and (Fe, Mn)-rich f.c.c. phases, was annealed at a variety of temperatures up to 1423 K and the microstructure and mechanical properties were examined. It was shown that the as-cast microstructure arises from a eutectoid transformation at ~1300 K. Annealing at temperatures ≤1073 K produces β-Mn-structured precipitates and hardness values up to 816 HV, while annealing at temperatures >1073 K leads to dramatic coarsening of the two-phase B2/f.c.c. microstructure (up to 5.5 µm after 50 h at 1273 K), but does not lead to β-Mn precipitation.more » Interestingly, annealing at temperatures >1073 K delays the onset of β-Mn precipitation during subsequent anneals at lower temperatures. Coarsening the B2/f.c.c. lamellar structure by annealing at higher temperatures softens it and leads to increases in ductility from fracture before yield to ~8 % elongation. Finally, the presence of β-Mn precipitates makes the very fine, brittle B2/f.c.c. microstructures even more brittle, but significant ductility (8.4 % elongation) is possible even with β-Mn precipitates present if the B2/f.c.c. matrix is coarse and, hence, more ductile.« less

  1. High-performance giant-magnetoresistance junction with B2-disordered Heusler alloy based Co2MnAl/Ag/Co2MnAl trilayer

    NASA Astrophysics Data System (ADS)

    Li, Yang; Xia, Jihong; Wang, Guangzhao; Yuan, Hongkuan; Chen, Hong

    2015-08-01

    The current-perpendicular-to-plane giant magnetoresistance (MR) devices with full-Heulser Co2MnAl (CMA) electrodes and a Ag spacer have been simulated to investigate the relationship between the transport properties and the structural disordering of electrodes by performing first-principles electronic structure and ballistic transport calculations. The CMA electrode has nearly negligible interfacial roughness in both L21 and B2-types. The transmission coefficient T σ ( E , k → / / ) is found strongly dependent on the structures of the trilayers for different structural CMA electrodes. High majority-spin electron conductance in the magnetization parallel configuration turns up in the entire k → -plane and the MR ratio reaches as high as over 90% for the B2-based CMA/Ag/CMA magnetic trilayers. In contrast, the L21-based one has ˜60% MR ratio resulting from much lower bulk spin-asymmetry coefficient (β), which might be caused by the vibrational spin-polarization in each atomic layer adjacent to the interfaces in the corresponding model. The patterns of T σ ( E , k → / / ) indicates that B2-based CMA/Ag/CMA magnetic trilayers are promising giant magnetoresistance junctions with high performance.

  2. Perpendicularly magnetized ferrimagnetic [Mn50Ga50/Co2FeAl] superlattice and the utilization in magnetic tunnel junctions

    NASA Astrophysics Data System (ADS)

    Ma, Q. L.; Zhang, X. M.; Miyazaki, T.; Mizukami, S.

    2015-08-01

    The ferrimagnetic superlattice (SL) [MnGa/Co2FeAl]n exhibiting perpendicular magnetic anisotropy opened a new method for spintronics materials used in magnetic random access memory, because of the high anisotropy, small damping constant and tunable magnetization. In this work, we fabricated SLs with different MnGa composition and studied the MnGa composition dependence of the structure and magnetic properties of the SLs. Furthermore, we fabricated fully perpendicular magnetic tunnel junctions with SLs as both top and bottom electrodes. A clear tunnel magnetoresistance (TMR) effect with TMR ratio of 1.3% at room temperature was observed.

  3. Atomic moments in Mn2CoAl thin films analyzed by X-ray magnetic circular dichroism

    DOE PAGESBeta

    Jamer, M. E.; Assaf, B. A.; Sterbinsky, G. E.; Arena, D. A.; Heiman, D.

    2014-12-05

    Spin gapless semiconductors are known to be strongly affected by structural disorder when grown epitaxially as thin films. The magnetic properties of Mn2CoAl thin films grown on GaAs (001) substrates are investigated here as a function of annealing. This study investigates the atomic-specific magnetic moments of Mn and Co atoms measured through X-ray magnetic circular dichroism as a function of annealing and the consequent structural ordering. Results indicate that the structural distortion mainly affects the Mn atoms as seen by the reduction of the magnetic moment from its predicted value.

  4. Electronic structures of the ferrimagnetic double-perovskites Sr2XReO6 (X = Cr, Mn, Fe, Ni) with the modified Becke-Johnson potential

    NASA Astrophysics Data System (ADS)

    Guo, San-Dong

    2015-04-01

    We investigate the electronic structures and magnetic properties of the ferrimagnetic double-perovskites Sr2XReO6 (X = Cr, Mn, Fe, Ni) by using Tran and Blaha's modified Becke and Johnson exchange potential. The calculated results show that Sr2XReO6 (X = Cr, Fe) are half-metals, and Sr2XReO6 (X = Mn, Ni) are insulators, which is in accordance with the experimental results. By using the ionic picture, we explain the trend in the density of states and total magnetic moment with X changing from Cr to Ni. We find that the insulating property is associated with X2 +, while the metallic character is associated with X3 +. The Re t2g splitting in the minority channel leads to insulativity of Sr2XReO6 (X = Mn, Ni), and the Re t2g splitting of Sr2MnReO6 is caused by lattice distortion, while Sr2NiReO6's splitting is due to the heavier atomic mass of Ni. When spin-orbit coupling is included, the spin polarization of Sr2XReO6 (X = Cr, Fe) drifts off 100%, and the related gaps of Sr2XReO6 (X = Mn, Ni) become narrow. The spin-orbit coupling results in a significant increase in the total magnetic moment due to an unquenched Re orbital moment. Our calculated energy band structures show that Sr2MnReO6 is a spin gapless semiconductor, which can realize fully polarized spin-down electrons and spin-up holes.

  5. Microstructures and mechanical properties of compositionally complex Co-free FeNiMnCr18 FCC solid solution alloy

    SciTech Connect

    Wu, Z.; Bei, H.

    2015-07-01

    Recently, a structurally-simple but compositionally-complex FeNiCoMnCr high entropy alloy was found to have excellent mechanical properties (e.g., high strength and ductility). To understand the potential of using high entropy alloys as structural materials for advanced nuclear reactor and power plants, it is necessary to have a thorough understanding of their structural stability and mechanical properties degradation under neutron irradiation. Furthermore, this requires us to develop a similar model alloy without Co because material with Co will make post-neutron-irradiation testing difficult due to the production of the 60Co radioisotope. In order to achieve this goal, a FCC-structured single-phase alloy with a composition of FeNiMnCr18 was successfully developed. This near-equiatomic FeNiMnCr18 alloy has good malleability and its microstructure can be controlled by thermomechanical processing. By rolling and annealing, the as-cast elongated-grained-microstructure is replaced by homogeneous equiaxed grains. The mechanical properties (e.g., strength and ductility) of the FeNiMnCr18 alloy are comparable to those of the equiatomic FeNiCoMnCr high entropy alloy. Both strength and ductility increase with decreasing deformation temperature, with the largest difference occurring between 293 and 77 K. Extensive twin-bands which are bundles of numerous individual twins are observed when it is tensile-fractured at 77 K. No twin bands are detected by EBSD for materials deformed at 293 K and higher. Ultimately the unusual temperature-dependencies of UTS and uniform elongation could be caused by the development of the dense twin substructure, twin-dislocation interactions and the interactions between primary and secondary twinning systems which result in a microstructure refinement and hence cause enhanced strain hardening and postponed necking.

  6. Kinetic Parameters of Secondary Carbide Precipitation in High-Cr White Iron Alloyed by Mn-Ni-Mo-V Complex

    NASA Astrophysics Data System (ADS)

    Efremenko, V. G.; Chabak, Yu. G.; Brykov, M. N.

    2013-05-01

    This study presents kinetics of precipitation of secondary carbides in 14.55%Cr-Mn-Ni-Mo-V white cast iron during the destabilization heat treatment. The as-cast iron was heat treated at temperatures in the range of 800-1100 °C with soaking up to 6 h. Investigation was carried out by optical and electron microscopy, dilatometric analysis, Ms temperature measurement, and bulk hardness evaluation. TTT-curve of precipitation process of secondary carbides (M7C3, M23C6, M3C2) has been constructed in this study. It was determined that the precipitation occurs at the maximum rate at 950 °C where the process is started after 10 s and completed within 160 min further. The precipitation leads to significant increase of Ms temperature and bulk hardness; large soaking times at destabilization temperatures cause coarsening of secondary carbides and decrease in particles number, followed by decrease in hardness. The results obtained are discussed in terms of solubility of carbon in the austenite and diffusion activation of Cr atoms. The precipitation was found to consist of two stages with activation energies of 196.5 kJ/g-mole at the first stage and 47.1 kJ/g-mole at the second stage.

  7. Magnetic and electronic properties of Cr- and Mn-doped SnO2: ab initio calculations

    NASA Astrophysics Data System (ADS)

    Ziat, Y.; Benyoussef, A.; El Kenz, A.

    2014-06-01

    The ab initio calculations, based on the Korringa-Kohn-Rostoker (KKR) approximation method combined with the coherent potential approximation (CPA), indicated as KKR-CPA, have been used to study the stability of ferromagnetic and ferrimagnetic states, for systems that are SnO2 doped and co-doped with two transition metals, that is, chromium and manganese. Our results indicate that the ferromagnetic state is more stable than the spin-glass state for the (Sn1-xCrxO2; x = 0.07, 0.09, 0.12 and 0.15)-doped system, while the spin-glass state is more stable than the ferromagnetic state for the (Sn1-xMnxO2; x = 0.02 and 0.05)-doped system. However, the ferromagnetic and/or the ferrimagnetic states are stable for the (Sn0.98-xMn0.02CrxO2; x = 0.05, 0.09 and 0.13)-doped system depending on the Cr concentration. Moreover, we estimated the Curie temperature (Tc) for the Cr-doped tin dioxide (SnO2), and we explained the origin of magnetic behaviour through the total density of states for different doped and co-doped SnO2 systems.

  8. Luminescence property and emission enhancement of YbAlO3:Mn4+ red phosphor by Mg2+ or Li+ ions

    NASA Astrophysics Data System (ADS)

    Cao, Renping; Luo, Wenjie; Xu, Haidong; Luo, Zhiyang; Hu, Qianglin; Fu, Ting; Peng, Dedong

    2016-03-01

    YbAlO3:Mn4+, YbAlO3:Mn4+, Li+, and YbAlO3:Mn4+, Mg2+ phosphors are synthesized by high temperature solid-state reaction method in air. Their crystal structures and luminescence properties are investigated. Photoluminescence excitation (PLE) spectrum monitored at 677 nm contains broad PLE band with three PLE peaks located at ∼318, 395, and 470 nm within the range 220-600 nm. Emission spectra with excitation 318 and 470 nm exhibit three emission band peaks located at ∼645, 677, and 700 nm in the range of 610-800 nm and their corresponding chromaticity coordinates are about (x = 0.6942, y = 0.3057). The possible luminous mechanism of Mn4+ ion is analyzed by the simple energy level diagram of Mn4+ ion. The optimum Mn4+-doped concentration in YbAlO3:Mn4+ phosphor is about 0.4 mol% and the luminescence lifetime of YbAlO3:0.4%Mn4+ phosphor is ∼0.59 ms. Emission intensity of YbAlO3:0.4%Mn4+ phosphor can be enhanced ∼6 times after Mg2+ ion is co-doped and it is ∼2 times when Li+ ion is co-doped. The content in the paper is useful to research new Mn4+-doped luminescence materials and improve luminescence property of other Mn4+-doped phosphors.

  9. The formation mechanism of eutectic microstructures in NiAl-Cr composites.

    PubMed

    Tang, Bin; Cogswell, Daniel A; Xu, Guanglong; Milenkovic, Srdjan; Cui, Yuwen

    2016-07-20

    NiAl-based eutectic alloys, consisting of an ordered bcc matrix (B2) and disordered bcc fibers (A2), have been a subject of intensive efforts aimed at tailoring the properties of many of the currently used nickel-based superalloys. A thermodynamic phase field model was developed on a thermodynamic foundation and fully integrated with a thermo-kinetic database of the Ni-Al-Cr ternary system to elucidate the resulting peculiar eutectic microstructure. Invoking a variation of the liquid/solid interfacial thickness with temperature, we simulated the characteristic sunflower-like eutectic microstructures in the NiAl-Cr composites, consistent with experimental observations. The mechanism that governs the formation of the peculiar eutectic morphology was envisioned from the modeled evolutions associated with six sequential steps. Our calculations show that the conditional spinodal decomposition occurring in sequence could further trim and revise the microstructure of the eutectics by generating fine-domain structures, thereby providing an additional method to explore the novel NiAl-based eutectic composites with tunable properties at elevated temperatures. PMID:27385194

  10. Microscopic origin of the different colors displayed by MgAl2O4:Cr3+ and emerald

    NASA Astrophysics Data System (ADS)

    García-Lastra, J. M.; Barriuso, M. T.; Aramburu, J. A.; Moreno, M.

    2008-08-01

    The difference in color between emerald ( Be3Si6Al2O18:Cr3+ , green) and the Cr3+ -doped spinel MgAl2O4 (red) is striking, considering that in both systems color is due to CrO69- complexes with a close local symmetry ( D3 and the D3d , respectively) and that the measured Cr3+-O2- distance is practically the same ( 1.98±0.01 and 1.97±0.01Å , respectively). By means of density-functional calculations it is shown that this surprising difference can reasonably be explained once the electric field, ER , which all lattice ions lying outside the CrO69- complex exert on localized electrons, is taken into consideration. The origin of the different shape of ER in the two host lattices is analyzed in detail. It is shown that ER raises (decreases) the 2p(O) levels for Be3Si6Al2O18:Cr3+ (MgAl2O4:Cr3+) along the trigonal axis thus favoring a decrease (increase) of 10Dq . The present work demonstrates the key role played by ER (not considered in the traditional ligand field theory) for understanding the differences exhibited by the same complex embedded in host lattices which do not have the same crystal structure. Some remarks on the color of Cr2O3 pure compound are also reported.

  11. Materials with layered structures II; A new quaternary compound with ZnIn/sub 2/S/sub 4/(IIIa)-type structure in the system MnGa/sub 2/S/sub 4/-MnCr/sub 2/S/sub 4/

    SciTech Connect

    Haeuseler, H.; Kwarteng-Acheampong, W. )

    1989-08-01

    With the intention to prepare new compounds with layered structures the authors studied the quasibinary system MnGa/sub 2/S/sub 4/-MnCr/sub 2/S/sub 4/ by X-ray investigations on powdered samples. The parent compounds MnGa/sub 2/S/sub 4/ and MnCr/sub 2/S/sub 4/ have no detectable phase widths. A new compound MnGa/sub 2chi/Cr/sub 2-2chi/S/sub 4/ (0.75 < x < 0.9) crystallizing in the layered ZnIn/sub 2/S/sub 4/(IIIa) type structure is observed in the gallium rich part of the system. Magnetic measurements on MnGa/sub 1.5/Cr/sub 0.5/S/sub 4/ in the temperature range 77-300 {Kappa} show paramagnetic behaviour with {theta} = -88{Kappa} and C = 4.418.

  12. Effects of Cr, Zr, V, Mn, Fe, and Co to the hydride properties of Laves phase-related body-centered-cubic solid solution alloys

    NASA Astrophysics Data System (ADS)

    Young, K.; Ouchi, T.; Nei, J.; Meng, T.

    2015-05-01

    Chemical composition modifications of a Laves phase-related BCC solid solution base alloy, Ti15.6Zr2.1V44Cr11.2Mn6.9Fe2.7Co1.4Ni15.7Al0.3, were investigated in order to study the function of each constituent element on the structural, gaseous phase and electrochemical hydrogen storage properties of these alloys. In general, removal of Fe and decrease in V-content in exchange for higher Ni-content were found to improve both the electrochemical capacity and high-rate dischargeability, which are related to the decrease in C14-content and increase in TiNi-content. However, total elimination of the C14 phase by removal of Zr resulted in a reduced discharge capacity, a prolonged activation period, and a less catalytic surface for electrochemical reaction. Besides the BCC and C14 phases, the TiNi phase was also found in every alloy in this study, contributing positively to the bulk diffusion of hydrogen while hindering the surface electrochemical reaction.

  13. Correlation of acoustic emission generated during uniform biaxial loading to microstructural sources in 7075-T651 aluminum and 21Cr-6Ni-9Mn stainless steel. Final report

    SciTech Connect

    Leon, E.; Mukherjee, A.K.

    1981-12-01

    This paper reports on the effect on acoustic emission (AE) of uniform biaxial loading of a thin-walled tube designed by Hamstad, Patterson and Mukherjee. The AE generated during biaxial loading of 7075-T651 aluminum and 21Cr-6Ni-9Mn stainless steel had several anomalous features relative to tensile generated AE. The biaxial AE data was of a much higher level and peaked at a lower strain than the uniaxial AE response. A particle cracking model was proposed in which inclusions with the largest projected surface area perpendicular to the principal axis of applied loading will crack before smaller inclusions, and the resulting energy released per AE will be proportional to the crack surface area. The inclusion contents were studied with respect to size, shape, density, hardness, and fracture/decohesion behavior. The inclusions in both 7075-T651 and 21-6-9 display the preferred cracking orientation predicted in the Hamstad, et al. model and are shown to be associated with the generated AE. However, other factors appear to contribute to the total AE responses. There is evidence that for 7075-T651 subjected to biaxial loading, a grain boundary-related mechanism becomes a significant source of AE in the latter stages of strain hardening. Also, for both materials, the complex applied load during biaxial loading appears to amplify the level of AE.

  14. Antiferromagnetism in CaAl2Si2-type CaMn2As2 and SrMn2As2 single crystals

    NASA Astrophysics Data System (ADS)

    Sangeetha, N. S.; Pandey, Abhishek; Benson, Zackery A.; Johnston, D. C.

    Magnetic susceptibility versus temperature χ (T) measurements of CaMn2As2 and SrMn2As2 crystals show clear antiferromagnetic (AFM) transitions at TN ~ 65 K and 120 K,1 respectively. The anisotropic behaviors in χ (T <=TN) suggest that both compounds are noncollinear antiferromagnets which may result either from an intrinsic noncollinear structure or from multiple collinear AFM domains that are not aligned collinearly.2 The χ (T) data at T >TN reveal that both compounds exhibit strong short-range AFM ordering, evidently associated with quasi-two-dimensional spin lattices. The electrical resistivities show insulating ground states with activation energies of ~ 63 meV in CaMn2As2 and 44 meV in SrMn2As2 . The experimental results thus reveal that both (Ca , Sr) Mn2As2 materials are AFM insulators at low temperatures and in analogy with the high Tc cuprates, may be potential parent compounds for CaAl2Si2-type superconductors. Work was supported by the USDOE under Contract No. DE-AC02-07CH11358.

  15. MnOx-CeO2-Al2O3 mixed oxides for soot oxidation: activity and thermal stability.

    PubMed

    Wu, Xiaodong; Liu, Shuang; Weng, Duan; Lin, Fan; Ran, Rui

    2011-03-15

    MnO(x)-CeO(2)-Al(2)O(3) mixed oxides were prepared by impregnating manganese acetate and cerium nitrate on alumina powders using the sol-gel method. The thermal stabilities of MnO(x)-CeO(2) and Al(2)O(3)-modified mixed oxides were evaluated by treating at 800 °C in dry air flow for 20h. The introduction of Al(2)O(3) markedly increases the textural stability of the catalyst with a relatively high dispersion of MnO(x) and CeO(2), remaining a strong synergistic effect between these two oxides. The NO oxidation activity of the ternary oxides experiences a smaller loss after high-temperature calcination, and a low soot oxidation temperature is attained in the presence of NO. PMID:21276659

  16. Calculations of structural, elastic, electronic, magnetic and phonon properties of FeNiMnAl by the first principles

    SciTech Connect

    Uğur, Şule; İyigör, Ahmet

    2014-10-06

    The electronic, elastic and dynamical properties of the quaternary alloy FeNiMnAl have been investigated using a pseudopotential plane wave method within the generalized gradient approximation (GGA). We determined the lattice parameters and the bulk modulus B. In addition, the elastic properties such as elastic constans (C{sub 11}, C{sub 12} and C{sub 44}), the shear modulus G, the young modulus E, the poisson's ratio σ and the B/G ratio are also given. The FeNiMnAl Heusler alloy exhibit a ferromagnetic half-metallic behavior with the total magnetic moment of 4.02 μ{sub B}. The phonon dispersion of FeNiMnAl has been performed using the density functional theory and the direct method with 2×2×2 supercell.

  17. HIGH TEMPERATURE BRAZING ALLOY FOR JOINT Fe-Cr-Al MATERIALS AND AUSTENITIC AND FERRITIC STAINLESS STEELS

    DOEpatents

    Cost, R.C.

    1958-07-15

    A new high temperature brazing alloy is described that is particularly suitable for brazing iron-chromiumaluminum alloys. It consists of approximately 20% Cr, 6% Al, 10% Si, and from 1.5 to 5% phosphorus, the balance being iron.

  18. Optical Characterization and 2,525 micron Lasing of Cr(2+):Cd(0.85)Mn(0.15)Te

    NASA Technical Reports Server (NTRS)

    Davis, V. R.; Wu, X.; Hoemmerich, U.; Trivedi, S. B.; Grasza, K.; Yu, Z.

    1997-01-01

    static acentric electric crystal field or the coupling of asymmetric phonons can force electric-dipole transitions by the admixture of wave functions with opposite parity. Tetrahedral sites lack inversion symmetry which provides the odd-parity field necessary to relax the parity selection rule. Therefore, high absorption and emission cross sections are observed. An enhanced radiative emission rate is also expected to reduce the detrimental effect of non-radiative decay. Motivated by the initial results on Cr doped ZnS and ZnSe, we have started a comprehensive effort to study Cr(2+) doped II-VI semiconductors for solid-state laser applications. In this paper we present the optical properties and the demonstration of mid-infrared lasing from Cr doped Cd(0.85)Mn(0.15)Te.

  19. Temporal variability of bioavailable Cd, Hg, Zn, Mn and Al in an upwelling regime.

    PubMed

    Lares, M Lucila; Flores, Muñoz Gilberto; Lara-Lara, Ruben

    2002-01-01

    Monthly variability of Cd, Hg, Zn, Mn and Al concentrations in mussels (Mytilus californianus) soft tissue and brown seaweed (Macrocystis pyrifera) was studied at a pristine rocky shore off San Quintin Bay, Baja California, México. The results were related to climatic and hydrographic conditions and to the physiological state of the mussels (condition index) by correlation analysis and principal component analysis (PCA). A "normalization" to account for the variability induced by the physiological state of the mussel was performed. The PCA was performed in two ways to relate the environmental variables and the condition index to: (1) the metal concentrations in mussels, and (2) the "normalized" mussel concentrations. The association of the variability of Cd with the upwelling season was revealed in both PCAs. The temporal variability of this metal in mussels was highly correlated to that in seaweed, suggesting that the dissolved phase determined the variability of Cd in mussels. However, for Hg, Zn, Mn and Al the results from both PCAs were different. The first PCA showed the relationship of these metals to pluvial precipitation and to the condition index. The PCA for the normalized mussel concentrations showed that, after eliminating the effect of the condition index, only Al was related to pluvial precipitation. Manganese, and to a less degree Zn, were related to these metals in seaweed. Because zinc is an essential element in mussels, some regulation of their internal concentrations is likely. Mercury was not detected in seaweed, but because of its reactive nature, it is not expected that the dissolved fraction could be a significant pathway; therefore, it can be concluded that its temporal variability was determined by the variability in the condition index only. PMID:12442783

  20. Amorphous structure and properties in laser-clad Ni-Cr-Al coating on Al-Si alloy

    NASA Astrophysics Data System (ADS)

    Liang, Gongying; Wong, T. T.; Su, J. Y.; Woo, C. H.

    1999-09-01

    A Ni-Cr-Al coating was clad by a 5 kW CO2 laser with different laser power on Al-Si alloy. Using transmission electron microscopy, a mixing microstructure containing Ni- based amorphous structures was observed in the laser clad zones. As the uniformity of chemical composition and temperature is poor in the laser cladding, the amorphous structure with some Ni3Al crystals coexisted in the cladding. According to the morphologies of Ni-based amorphous structures, the amorphous structure existed not only in the net-like boundaries surrounding the granular structure but also in the granular structure. The microhardness of the mixture amorphous structure is between HV 600 - 800, which is lower than that of crystal phases in the coating. A differential thermal analysis showed that Ni- based amorphous structure exhibits a higher initial crystallizing temperature (about 588 degree(s)C), which is slightly higher than that of the eutectic temperature of Al- Si alloy. The wear experimental results showed that some amorphous structure exist in the laser cladding can reduce the peeling of the granular phases from matrix, and improve the its wear resistance.