Science.gov

Sample records for 17-4 precipitation hardening

  1. Microstructure and Mechanical Behavior of 17-4 Precipitation Hardenable Steel Processed by Selective Laser Melting

    NASA Astrophysics Data System (ADS)

    Rafi, H. Khalid; Pal, Deepankar; Patil, Nachiket; Starr, Thomas L.; Stucker, Brent E.

    2014-12-01

    The mechanical behavior and the microstructural evolution of 17-4 precipitation hardenable (PH) stainless steel processed using selective laser melting have been studied. Test coupons were produced from 17-4 PH stainless steel powder in argon and nitrogen atmospheres. Characterization studies were carried out using mechanical testing, optical microscopy, scanning electron microscopy, and x-ray diffraction. The results show that post-process heat treatment is required to obtain typically desired tensile properties. Columnar grains of smaller diameters (<2 µm) emerged within the melt pool with a mixture of martensite and retained austenite phases. It was found that the phase content of the samples is greatly influenced by the powder chemistry, processing environment, and grain diameter.

  2. Microstructure and Mechanical Behavior of 17-4 Precipitation Hardenable Steel Processed by Selective Laser Melting

    NASA Astrophysics Data System (ADS)

    Rafi, H. Khalid; Pal, Deepankar; Patil, Nachiket; Starr, Thomas L.; Stucker, Brent E.

    2014-09-01

    The mechanical behavior and the microstructural evolution of 17-4 precipitation hardenable (PH) stainless steel processed using selective laser melting have been studied. Test coupons were produced from 17-4 PH stainless steel powder in argon and nitrogen atmospheres. Characterization studies were carried out using mechanical testing, optical microscopy, scanning electron microscopy, and x-ray diffraction. The results show that post-process heat treatment is required to obtain typically desired tensile properties. Columnar grains of smaller diameters (<2 µm) emerged within the melt pool with a mixture of martensite and retained austenite phases. It was found that the phase content of the samples is greatly influenced by the powder chemistry, processing environment, and grain diameter.

  3. Precipitation hardening austenitic superalloys

    DOEpatents

    Korenko, Michael K.

    1985-01-01

    Precipitation hardening, austenitic type superalloys are described. These alloys contain 0.5 to 1.5 weight percent silicon in combination with about 0.05 to 0.5 weight percent of a post irradiation ductility enhancing agent selected from the group of hafnium, yttrium, lanthanum and scandium, alone or in combination with each other. In addition, when hafnium or yttrium are selected, reductions in irradiation induced swelling have been noted.

  4. Nonlinear ultrasonic characterization of precipitation in 17-4PH stainless steel

    SciTech Connect

    Matlack, Kathryn; Bradley, Harrison A.; Thiele, Sebastian; Kim, Jin-Yeon; Wall, James J.; Jung, Hee Joon; Qu, Jianmin; Jacobs, Laurence J.

    2015-04-01

    The extension of operational lifetime of most US nuclear reactors will cause reactor pressure vessel to be exposed to increased levels of neutron radiation damage. This research is part of a broader effort to develop a nondestructive evaluation technique to monitor radiation damage in reactor pressure vessel steels. The main contributor to radiation embrittlement in these steels is the formation of copper-rich precipitates. In this work, a precipitate hardenable martensitic alloy, 17-4PH stainless steel is exposed to thermal aging treatments, and used as a surrogate material to study the effects of copper precipitates on the measured acoustic nonlinearity parameter. Previous work has demonstrated the effectiveness of these nonlinear ultrasonic (NLU) measurements in the characterization of radiation-induced microstructural changes in neutron irradiated reactor pressure vessel steels. NLU measurements using Rayleigh surface waves are performed on 17-4PH samples subjected to isothermal aging. NLU measurements are interpreted with hardness, thermo-electric power, TEM, and atom probe tomography measurements. The Rayleigh wave measurements showed a decrease in the acoustic nonlinearity parameter with increasing aging time, consistent with evidence of increasing number density of nucleated precipitates.

  5. Precipitation hardening in 350 grade maraging steel

    SciTech Connect

    Viswanathan, U.K. . Radiometallurgy Div.); Dey, G.K. . Metallurgy Division); Asundi, M.K. )

    1993-11-01

    Evolution of microstructure in 350 grade commercial maraging steel has been examined. In the earlier stages of aging, the strengthening phases are formed by the heterogeneous precipitation, and these phases have been identified as intermetallic compounds of the Ni[sub 3] (Ti, Mo) and Fe[sub 2]Mo types. The kinetics of precipitation are studied in terms of the activation energy by carrying out isothermal hardness measurements of aged material. The mechanical properties in the peak-aged and overaged conditions were evaluated and the flow behavior examined. The overaging behavior of the steel has been studied and the formation of austenite of different morphologies identified. The crystallography of the austenite has been examined in detail. From the microstructural examination of peak-aged and deformed samples, it could be inferred that the dislocation-precipitate interaction is by precipitate shearing. Increased work hardening of the material in the overaged condition was suggestive of looping of precipitates by dislocations.

  6. Stress corrosion cracking evaluation of martensitic precipitation hardening stainless steels

    NASA Technical Reports Server (NTRS)

    Humphries, T. S.; Nelson, E. E.

    1980-01-01

    The resistance of the martensitic precipitation hardening stainless steels PH13-8Mo, 15-5PH, and 17-4PH to stress corrosion cracking was investigated. Round tensile and c-ring type specimens taken from several heats of the three alloys were stressed up to 100 percent of their yield strengths and exposed to alternate immersion in salt water, to salt spray, and to a seacoast environment. The results indicate that 15-5PH is highly resistant to stress corrosion cracking in conditions H1000 and H1050 and is moderately resistant in condition H900. The stress corrosion cracking resistance of PH13-8Mo and 17-4PH stainless steels in conditions H1000 and H1050 was sensitive to mill heats and ranged from low to high among the several heats included in the tests. Based on a comparison with data from seacoast environmental tests, it is apparent that alternate immersion in 3.5 percent salt water is not a suitable medium for accelerated stress corrosion testing of these pH stainless steels.

  7. Stress corrosion cracking evaluation of precipitation-hardening stainless steel

    NASA Technical Reports Server (NTRS)

    Humphries, T. S.; Nelson, E. E.

    1970-01-01

    Accelerated test program results show which precipitation hardening stainless steels are resistant to stress corrosion cracking. In certain cases stress corrosion susceptibility was found to be associated with the process procedure.

  8. Precipitation-Induced Changes in Microstrain and Its Relation with Hardness and Tempering Parameter in 17-4 PH Stainless Steel

    NASA Astrophysics Data System (ADS)

    Mahadevan, S.; Manojkumar, R.; Jayakumar, T.; Das, C. R.; Rao, B. P. C.

    2016-06-01

    17-4 PH (precipitation hardening) stainless steel is a soft martensitic stainless steel strengthened by aging at appropriate temperature for sufficient duration. Precipitation of copper particles in the martensitic matrix during aging causes coherency strains which improves the mechanical properties, namely hardness and strength of the matrix. The contributions to X-ray diffraction (XRD) profile broadening due to coherency strains caused by precipitation and crystallite size changes due to aging are separated and quantified using the modified Williamson-Hall approach. The estimated normalized mean square strain and crystallite size are used to explain the observed changes in hardness. Microstructural changes observed in secondary electron images are in qualitative agreement with crystallite size changes estimated from XRD profile analysis. The precipitation kinetics in the age-hardening regime and overaged regime are studied from hardness changes and they follow the Avrami kinetics and Wilson's model, respectively. In overaged condition, the hardness changes are linearly correlated to the tempering parameter (also known as Larson-Miller parameter). Similar linear variation is observed between the normalized mean square strain (determined from XRD line profile analysis) and the tempering parameter, in the incoherent regime which is beyond peak microstrain conditions.

  9. Method and apparatus for welding precipitation hardenable materials

    DOEpatents

    Murray, Jr., Holt; Harris, Ian D.; Ratka, John O.; Spiegelberg, William D.

    1994-01-01

    A method for welding together members consisting of precipitation age hardened materials includes the steps of selecting a weld filler material that has substantially the same composition as the materials being joined, and an age hardening characteristic temperature age threshold below that of the aging kinetic temperature range of the materials being joined, whereby after welding the members together, the resulting weld and heat affected zone (HAZ) are heat treated at a temperature below that of the kinetic temperature range of the materials joined, for obtaining substantially the same mechanical characteristics for the weld and HAZ, as for the parent material of the members joined.

  10. Method and apparatus for welding precipitation hardenable materials

    DOEpatents

    Murray, H. Jr.; Harris, I.D.; Ratka, J.O.; Spiegelberg, W.D.

    1994-06-28

    A method for welding together members consisting of precipitation age hardened materials includes the steps of selecting a weld filler material that has substantially the same composition as the materials being joined, and an age hardening characteristic temperature age threshold below that of the aging kinetic temperature range of the materials being joined, whereby after welding the members together, the resulting weld and heat affected zone (HAZ) are heat treated at a temperature below that of the kinetic temperature range of the materials joined, for obtaining substantially the same mechanical characteristics for the weld and HAZ, as for the parent material of the members joined. 5 figures.

  11. Precipitation hardening in a dental low-gold alloy.

    PubMed

    Kim, Hyung-Il; Park, Young-Hwan; Lee, Hee-Kyung; Seol, Hyo-Joung; Shiraishi, Takanobu; Hisatsune, Kunihiro

    2003-03-01

    Age-hardening characteristics in a dental low-gold alloy composed of 40.0 wt% Au-35.0 wt% Ag-7.9 wt% Pd-7.0 wt% Cu-5.0 wt% In-3.5 wt% Zn-1.5 wt% Sn, were investigated by means of the hardness test, XRD study, SEM observations and EPMA. The following results were obtained. The age-hardening was characterized by a precipitation of Cu-rich alpha2 phase in the a phase. The softening that occurred following prolonged ageing was due to the heterogeneous formation of the fine nodular precipitates composed of the Ag-rich alpha1 phase and the Cu-rich alpha2 phase at the grain boundaries of the a phase. PMID:12790292

  12. Theoretical Study of the Oxidation Behavior of Precipitation Hardening Steel

    SciTech Connect

    Pistofidis, N.; Vourlias, G.; Chrissafis, K.; Psyllaki, P.

    2010-01-21

    The oxidation of precipitation hardening (PH) steels is a rather unexplored area. In the present work an attempt is made is made to estimate the kinetics of a PH steel. For this purpose specimens of the material under examination were isothermally heated at 850, 900 and 950 deg. C for 15 hr. Kinetics was based on TGA results. During heating a thick scale is formed on the substrate surface, which is composed by different oxides. The layer close to the substrate is compact and as a result it impedes corrosion. The mathematical analysis of the collected data shows that the change of the mass of the substrate per unit area versus time is described by a parabolic law.

  13. Sulfide Stress Cracking and Electrochemical Corrosion of Precipitation Hardening Steel After Plasma Oxy-Nitriding

    NASA Astrophysics Data System (ADS)

    Granda-Gutiérrez, E. E.; Díaz-Guillén, J. C.; Díaz-Guillén, J. A.; González, M. A.; García-Vázquez, F.; Muñóz, R.

    2014-11-01

    In this paper, we present the results of a duplex plasma nitriding followed by an oxidizing stage process (which is also referred as oxy-nitriding) on the corrosion behavior of a 17-4PH precipitation hardening stainless steel. The formation of both, expanded martensite (b.c.t. α'N-phase) and chromium oxide (type Cr2O3) in the subsurface of oxy-nitrided samples at specific controlled conditions, leads in a noticeable increasing in the time-to-rupture during the sulfide stress cracking test, in comparison with an untreated reference sample. Oxy-nitriding improves the corrosion performance of the alloy when it is immersed in solutions saturated by sour gas, which extends the application potential of this type of steel in the oil and gas extraction and processing industry. The presence of the oxy-nitrided layer inhibits the corrosion process that occurs in the near-surface region, where hydrogen is liberated after the formation of iron sulfides, which finally produces a fragile fracture by micro-crack propagation; the obtained results suggest that oxy-nitriding slows this process, thus delaying the rupture of the specimen. Moreover, oxy-nitriding produces a hard, sour gas-resistant surface, but do not significantly affect the original chloride ion solution resistance of the material.

  14. Sulfide Stress Cracking and Electrochemical Corrosion of Precipitation Hardening Steel After Plasma Oxy-Nitriding

    NASA Astrophysics Data System (ADS)

    Granda-Gutiérrez, E. E.; Díaz-Guillén, J. C.; Díaz-Guillén, J. A.; González, M. A.; García-Vázquez, F.; Muñóz, R.

    2014-09-01

    In this paper, we present the results of a duplex plasma nitriding followed by an oxidizing stage process (which is also referred as oxy-nitriding) on the corrosion behavior of a 17-4PH precipitation hardening stainless steel. The formation of both, expanded martensite (b.c.t. α'N-phase) and chromium oxide (type Cr2O3) in the subsurface of oxy-nitrided samples at specific controlled conditions, leads in a noticeable increasing in the time-to-rupture during the sulfide stress cracking test, in comparison with an untreated reference sample. Oxy-nitriding improves the corrosion performance of the alloy when it is immersed in solutions saturated by sour gas, which extends the application potential of this type of steel in the oil and gas extraction and processing industry. The presence of the oxy-nitrided layer inhibits the corrosion process that occurs in the near-surface region, where hydrogen is liberated after the formation of iron sulfides, which finally produces a fragile fracture by micro-crack propagation; the obtained results suggest that oxy-nitriding slows this process, thus delaying the rupture of the specimen. Moreover, oxy-nitriding produces a hard, sour gas-resistant surface, but do not significantly affect the original chloride ion solution resistance of the material.

  15. 17-4 PH and 15-5 PH

    NASA Technical Reports Server (NTRS)

    Johnson, Howard T.

    1995-01-01

    17-4 PH and 15-5 PH are extremely useful and versatile precipitation-hardening stainless steels. Armco 17-4 PH is well suited for the magnetic particle inspection requirements of Aerospace Material Specification. Armco 15-5 PH and 17-4 PH are produced in billet, plate, bar, and wire. Also, 15-5 PH is able to meet the stringent mechanical properties required in the aerospace and nuclear industries. Both products are easy to heat treat and machine, making them very useful in many applications.

  16. Continuous Hardening During Isothermal Aging at 723 K (450 °C) of a Precipitation Hardening Stainless Steel

    NASA Astrophysics Data System (ADS)

    Celada-Casero, Carola; Chao, Jesús; Urones-Garrote, Esteban; San Martin, David

    2016-06-01

    The isothermal aging behavior of a cold-rolled precipitation hardening stainless steel has been studied at 723 K (450 °C) for holding times up to 72 hours. The precipitation hardening has been investigated using microhardness Vickers (Hv), thermoelectric power (TEP) measurements, and tensile testing. Microhardness compared to TEP measurements is more sensitive to detect the initial stages of aging. Two precipitation regimes have been observed: the first one related to the formation of Cu-clusters for aging times below 1 hour and a second one associated with formation of Ni-rich precipitates. The results show that the material exhibits an outstanding continuous age strengthening response over the aging time investigated, reaching a hardness of 710 ± 4 HV1 and an ultimate tensile strength (σ UTS) of 2.65 ± 0.02 GPa after 72 hours. Engineering stress-plastic strain curves reveal that the strength increases and the ductility decreases as the aging time increases. However, after prolonged holding times (24-72 hours) and, although small, a rise in both the strength and the total elongation is observed. The precipitation kinetics can be well predicted over the entire range of aging times by the Johnson-Mehl-Avrami-Kolmogorov (JMAK) equation. Finally, a reliable linear hardness-yield strength correlation has been found, which enables a rapid evaluation of the strength from bulk hardness measurements.

  17. On the Precipitation Hardening of Selective Laser Melted AlSi10Mg

    NASA Astrophysics Data System (ADS)

    Aboulkhair, Nesma T.; Tuck, Chris; Ashcroft, Ian; Maskery, Ian; Everitt, Nicola M.

    2015-08-01

    Precipitation hardening of selective laser melted AlSi10Mg was investigated in terms of solution heat treatment and aging duration. The influence on the microstructure and hardness was established, as was the effect on the size and density of Si particles. Although the hardness changes according to the treatment duration, the maximum hardening effect falls short of the hardness of the as-built parts with their characteristic fine microstructure. This is due to the difference in strengthening mechanisms.

  18. Group precipitation and age hardening of nanostructured Fe-based alloys with ultra-high strengths

    PubMed Central

    Jiao, Z. B.; Luan, J. H.; Miller, M. K.; Yu, C. Y.; Liu, C. T.

    2016-01-01

    The precipitation of nanoparticles plays a key role in determining the properties of many structural materials, and the understanding of their formation and stabilization mechanisms has been a long standing interest in the material field. However, the critical issues involving the group precipitation of various nanoparticles and their cooperative hardening mechanism remain elusive in the newly discovered Fe-based alloys with nanostructures. Here we quantitatively elucidate the nucleation mechanism, evolution kinetics and hardening effects of the group-precipitated nanoparticles in the Fe-Cu-Ni-Al-based alloys by atom probe tomography together with both first-principles and thermodynamic calculations. Our results provide the compelling evidence for two interesting but complex group precipitation pathways of nanoparticles, i.e., the Cu-rich and NiAl-based precipitations. The co-existence of the two precipitation pathways plays a key role in age hardening kinetics and ultimately enhances the hardening response, as compared to the single particle type of strengthening, therefore providing an effective new approach for strengthening materials for structural applications. PMID:26892834

  19. Group precipitation and age hardening of nanostructured Fe-based alloys with ultra-high strengths.

    PubMed

    Jiao, Z B; Luan, J H; Miller, M K; Yu, C Y; Liu, C T

    2016-01-01

    The precipitation of nanoparticles plays a key role in determining the properties of many structural materials, and the understanding of their formation and stabilization mechanisms has been a long standing interest in the material field. However, the critical issues involving the group precipitation of various nanoparticles and their cooperative hardening mechanism remain elusive in the newly discovered Fe-based alloys with nanostructures. Here we quantitatively elucidate the nucleation mechanism, evolution kinetics and hardening effects of the group-precipitated nanoparticles in the Fe-Cu-Ni-Al-based alloys by atom probe tomography together with both first-principles and thermodynamic calculations. Our results provide the compelling evidence for two interesting but complex group precipitation pathways of nanoparticles, i.e., the Cu-rich and NiAl-based precipitations. The co-existence of the two precipitation pathways plays a key role in age hardening kinetics and ultimately enhances the hardening response, as compared to the single particle type of strengthening, therefore providing an effective new approach for strengthening materials for structural applications. PMID:26892834

  20. Group precipitation and age hardening of nanostructured Fe-based alloys with ultra-high strengths

    NASA Astrophysics Data System (ADS)

    Jiao, Z. B.; Luan, J. H.; Miller, M. K.; Yu, C. Y.; Liu, C. T.

    2016-02-01

    The precipitation of nanoparticles plays a key role in determining the properties of many structural materials, and the understanding of their formation and stabilization mechanisms has been a long standing interest in the material field. However, the critical issues involving the group precipitation of various nanoparticles and their cooperative hardening mechanism remain elusive in the newly discovered Fe-based alloys with nanostructures. Here we quantitatively elucidate the nucleation mechanism, evolution kinetics and hardening effects of the group-precipitated nanoparticles in the Fe-Cu-Ni-Al-based alloys by atom probe tomography together with both first-principles and thermodynamic calculations. Our results provide the compelling evidence for two interesting but complex group precipitation pathways of nanoparticles, i.e., the Cu-rich and NiAl-based precipitations. The co-existence of the two precipitation pathways plays a key role in age hardening kinetics and ultimately enhances the hardening response, as compared to the single particle type of strengthening, therefore providing an effective new approach for strengthening materials for structural applications.

  1. Group precipitation and age hardening of nanostructured Fe-based alloys with ultra-high strengths

    DOE PAGESBeta

    Jiao, Z. B.; Luan, J. H.; Miller, M. K.; Yu, C. Y.; Liu, C. T.

    2016-02-19

    The precipitation of nanoparticles plays a key role in determining the properties of many structural materials, and the understanding of their formation and stabilization mechanisms has been a long standing interest in the material field. However, the critical issues involving the group precipitation of various nanoparticles and their cooperative hardening mechanism remain elusive in the newly discovered Fe-based alloys with nanostructures. Here we quantitatively elucidate the nucleation mechanism, evolution kinetics and hardening effects of the group-precipitated nanoparticles in the Fe-Cu-Ni-Al-based alloys by atom probe tomography together with both first-principles and thermodynamic calculations. Our results provide the compelling evidence for twomore » interesting but complex group precipitation pathways of nanoparticles, i.e., the Cu-rich and NiAl-based precipitations. Lastly, the co-existence of the two precipitation pathways plays a key role in age hardening kinetics and ultimately enhances the hardening response, as compared to the single particle type of strengthening, therefore providing an effective new approach for strengthening materials for structural applications.« less

  2. A mathematical model to predict the strength of aluminum alloys subjected to precipitation hardening

    SciTech Connect

    Qureshi, F.S.; Sheikh, A.K.; Rashid, M.

    1999-06-01

    A number of alloys, notably most of the aluminum alloys, can be heat treated by aging. This aging due to time-dependent precipitation hardening increases the strength and hardness as well as modifying other mechanical properties. Precipitation hardening has been a popular strengthening mechanism for many decades; therefore, extensive information is available in literature about the precipitation-hardening response of various series of aluminum alloys. The age-hardening response of these alloys is usually represented in graphical form as plotted between property changes and aging time for different temperatures. In designing a suitable precipitation-hardening strategy, one can refer to these graphs. However, for automatic control of aging furnaces, as well as for decision making regarding optimal selection of aging conditions (time/temperature combination), it is desirable to express these relationships in a formal mathematical structure. A mathematical model is developed in this article for widely used heat treatable aluminum alloys used in the extrusion industry. This model is a condensed representation of all {sigma} = f(T,t) curves in different series of aluminum alloys, and the parameters of this model characterize the various compositions of the alloys in the series.

  3. Precipitation Reactions in Age-Hardenable Alloys During Laser Additive Manufacturing

    NASA Astrophysics Data System (ADS)

    Jägle, Eric A.; Sheng, Zhendong; Wu, Liang; Lu, Lin; Risse, Jeroen; Weisheit, Andreas; Raabe, Dierk

    2016-03-01

    We describe and study the thermal profiles experienced by various age-hardenable alloys during laser additive manufacturing (LAM), employing two different manufacturing techniques: selective laser melting and laser metal deposition. Using scanning electron microscopy and atom probe tomography, we reveal at which stages during the manufacturing process desired and undesired precipitation reactions can occur in age-hardenable alloys. Using examples from a maraging steel, a nickel-base superalloy and a scandium-containing aluminium alloy, we demonstrate that precipitation can already occur during the production of the powders used as starting material, during the deposition of material (i.e. during solidification and subsequent cooling), during the intrinsic heat treatment effected by LAM (i.e. in the heat affected zones) and, naturally, during an ageing post-heat treatment. These examples demonstrate the importance of understanding and controlling the thermal profile during the entire additive manufacturing cycle of age-hardenable materials including powder synthesis.

  4. Joining precipitation-hardened nickel-base alloys by friction welding

    NASA Technical Reports Server (NTRS)

    Moore, T. J.

    1972-01-01

    Solid state deformation welding process, friction welding, has been developed for joining precipitation hardened nickel-base alloys and other gamma prime-strengthened materials which heretofore have been virtually unweldable. Method requires rotation of one of the parts to be welded, but where applicable, it is an ideal process for high volume production jobs.

  5. Microstructural evolution and the variation of tensile behavior after aging heat treatment of precipitation hardened martensitic steel

    SciTech Connect

    Shin, Jong-Ho; Jeong, JaeSuk; Lee, Jong-Wook

    2015-01-15

    The effects of aging temperature on the microstructural evolution and the tensile behavior of precipitation hardened martensitic steel were investigated. Microscopic analysis using transmission electron microscope (TEM) was combined with the microstructural analysis using the synchrotron X-ray diffraction (XRD) to characterize the microstructural evolution with aging temperature. Peak hardness was obtained by precipitation of the Ni{sub 3}Al ordered phase. After aging at temperature range from 420 to 590 °C, spherical Ni{sub 3}Al precipitates and ellipsoidal M{sub 23}C{sub 6} carbides were observed within laths and at lath boundaries, respectively. Strain hardening behavior was analyzed with Ludwik equation. It is observed that the plastic strain regimes can be divided into two different stages by a rapid increase in strain hardening followed by a comparatively lower increase. At the first strain hardening stage, the aged specimen exhibited higher strain hardening exponent than the as-quenched specimen, and the exponent in the aged specimen was not changed considerably with increasing aging temperature. It is revealed that the strain hardening exponents at the first and the second stages were associated with the Ni{sub 3}Al precipitates and the domain size representing the coherent scattering area, respectively. - Highlights: • All of aged specimen exhibited higher strain hardening exponent than the as-quenched specimen at the first stage. • The value of strain hardening exponent in the aged specimen was nearly constant with aging temperature. • Ni{sub 3}Al precipitation dominantly influenced to the increase of strain hardening exponent at the first strain hardening stage. • Domain size was associated with strain hardening exponent at the second strain hardening stage.

  6. Intergranular fracture in some precipitation-hardened aluminum alloys at low temperatures

    SciTech Connect

    Kuramoto, S.; Itoh, G.; Kanno, M.

    1996-10-01

    Intergranular fracture at low temperatures from room temperature down to 4.2 K has been studied in some precipitation-hardened aluminum alloys. Microscopic appearance of intergranular facets is revealed to be greatly affected by the microstructure adjacent to the grain boundaries (GBs). When large precipitates on GBs and wide precipitation-free zones (PFZs) are present, coalescence of microvoids initiated at the GB precipitates causes the intergranular fracture with dimples. This fracture process is found to be unaffected by deformation temperature. On the other hand, in the presence of fine precipitates on GBs and narrow PFZs, matrix slip localization exerts significant influence on the fracture behavior. At low temperatures, large stress concentration at GBs leads to intergranular fracture, forming sharp ledges on the fracture surfaces, while at room temperature, the dynamic recovery process is thought to relax such stress concentration, resulting in a transgranular ductile rupture.

  7. The combination of precipitation and dispersion hardening in powder metallurgy produced Cu-Ti-Si alloy

    SciTech Connect

    Bozic, D.; Dimcic, O.; Dimcic, B. Cvijovic, I.; Rajkovic, V.

    2008-08-15

    Microstructure and microhardness properties of precipitation hardened Cu-Ti and precipitation/dispersion hardened Cu-Ti-Si alloys have been analyzed. Cu-1.2Ti and Cu-1.2Ti-3TiSi{sub 2} (wt.%) atomized powders were characterized before and after consolidation by HIP (Hot Isostatic Pressing). Rapidly solidified powders and HIP-ed compacts were subsequently subjected to thermal treatment in hydrogen at temperatures between 300 and 600 deg. C. Compared to Cu-Ti powder particles and compacts, obtained by the same procedure, the strengthening effect in Cu-1.2Ti-3TiSi{sub 2} powder particles and compacts was much greater. The binary and ternary powders both reveal properties superior to those of Cu-1.2Ti and Cu-1.2Ti-3TiSi{sub 2} compacts. Microhardness analysis as a function of the aging temperature of Cu-1.2Ti-3TiSi{sub 2} alloy shows an interaction between precipitation and dispersion hardening which offers possibilities for an application at elevated temperatures.

  8. Age-hardening associated with grain boundary precipitation in a commercial dental gold alloy.

    PubMed

    Kim, H I; Jang, M I; Kim, M S

    1999-03-01

    The aim of this study was to make clear the age-hardening mechanism in a dental high carat gold alloy. For this purpose, age-hardening behaviour of a commercial dental high carat gold alloy, 65.5 wt% Au-14.0 wt% Ag-10.0 wt% Cu-8.9 wt% Pt, was investigated by means of hardness testing, X-ray diffraction study and scanning electron microscopy. Age-hardening was generated by the coherency strain resulting from the transformation of the alpha single phase to the Ag-rich alpha 1 phase and the AuCu I type ordered phase. The coherency strain seemed to be associated with the nucleation of the AuCu ordered structure initially, and then was brought about with the simultaneous formation of the Ag-rich alpha 1 phase and the AuCu I type ordered phase. Hardening was attributed mainly to the very fine coherent precipitates of a lamellar structure composed of the Ag-rich alpha 1 phase and the AuCu I type ordered phase at grain boundaries, and softening, which occurred following prolonged ageing, was due to the coarsening of the fine lamellar structure by releasing the strain at the interfaces of the adjacent lamellae. PMID:10194730

  9. Pulsed-laser atom probe studies of a precipitation hardened maraging TRIP steel.

    PubMed

    Dmitrieva, O; Choi, P; Gerstl, S S A; Ponge, D; Raabe, D

    2011-05-01

    A precipitation hardened maraging TRIP steel was analyzed using a pulsed laser atom probe. The laser pulse energy was varied from 0.3 to 1.9 nJ to study its effect on the measured chemical compositions and spatial resolution. Compositional analyses using proximity histograms did not show any significant variations in the average matrix and precipitate compositions. The only remarkable change in the atom probe data was a decrease in the ++/+ charge state ratios of the elements. The values of the evaporation field used for the reconstructions exhibit a linear dependence on the laser pulse energy. The adjustment of the evaporation fields used in the reconstructions for different laser pulse energies was based on the correlation of the obtained cluster shapes to the TEM observations. No influence of laser pulse energy on chemical composition of the precipitates and on the chemical sharpness of their interfaces was detected. PMID:21215524

  10. Influence of Precipitation Hardening in Mg-Y-Nd on Mechanical and Corrosion Properties

    NASA Astrophysics Data System (ADS)

    Maier, P.; Peters, R.; Mendis, C. L.; Müller, S.; Hort, N.

    2016-04-01

    Precipitation hardening is an effective strengthening mechanism to achieve high strength at moderate ductility in Mg-RE alloys. However, improved mechanical properties by precipitates that strengthen the alloy can affect corrosion rates as the finely dispersed particles are often more noble than the matrix. Biodegradable implant material should show a certain corrosion rate, but should be free of pitting, because wide and deep pits are notches that can cause higher stress concentration. WE43 has generally shown an acceptable biological response. In this study, a Mg-Y-Nd-Gd-Dy (WE32) alloy in extruded, solution and precipitation heat-treated conditions has been investigated. Solution heat treatment causes grain growth and strength loss. A rather short ageing response to peak hardness was observed, where peak hardening causes hardness values to exceed that of the initial extruded condition. Grain growth during ageing is not significant. Corrosion was evaluated with potentiodynamic polarization in Ringer Acetate solution. The highest corrosion rate was observed in the T4 condition. The peak aged alloy showed the most homogenous form of corrosion.

  11. Processing, Microstructures and Properties of a Dual Phase Precipitation-Hardening PM Stainless Steel

    NASA Astrophysics Data System (ADS)

    Schade, Christopher

    To improve the mechanical properties of PM stainless steels in comparison with their wrought counterparts, a PM stainless steel alloy was developed which combines a dual-phase microstructure with precipitation-hardening. The use of a mixed microstructure of martensite and ferrite results in an alloy with a combination of the optimum properties of each phase, namely strength and ductility. The use of precipitation hardening via the addition of copper results in additional strength and hardness. A range of compositions was studied in combination with various sintering conditions to determine the optimal thermal processing to achieve the desired microstructure. The microstructure could be varied from predominately ferrite to one containing a high percentage of martensite by additions of copper and a variation of the sintering temperature before rapid cooling. Mechanical properties (transverse rupture strength (TRS), yield strength, tensile strength, ductility and impact toughness) were measured as a function of the v/o ferrite in the microstructure. A dual phase alloy with the optimal combination of properties served as the base for introducing precipitation hardening. Copper was added to the base alloy at various levels and its effect on the microstructure and mechanical properties was quantified. Processing at various sintering temperatures led to a range of microstructures; dilatometry was used utilized to monitor and understand the transformations and the formation of the two phases. The aging process was studied as a function of temperature and time by measuring TRS, yield strength, tensile strength, ductility, impact toughness and apparent hardness. It was determined that optimum aging was achieved at 538°C for 1h. Aging at slightly lower temperatures led to the formation of carbides, which contributed to reduced hardness and tensile strength. As expected, at the peak aging temperature, an increase in yield strength and ultimate tensile strength as well as

  12. Mechanical Properties Anisotropy of Isothermally Forged and Precipitation Hardened Inconel 718 Disk

    NASA Astrophysics Data System (ADS)

    Khaja, Shaik; Mehta, K. K.; Veera Babu, R.; Sri Rama Devi, R.; Singh, A. K.

    2015-03-01

    The present work describes the tensile and cyclic flow behavior of the as-received disk of Inconel 718 in solution treated and precipitation hardened condition at different locations and orientations. The disk shows moderately high values of anisotropy index indicating significant difference in uniform true strain along radial and tangential orientations. The tensile true stress-plastic strain curves exhibit two slopes defined by Ludwigson relation []. The low-strain regime during tensile test is associated with low-strain localization between broad annealing twins and slips, while high-strain regime is related to the presence of large volume fraction of deformation twins and high-strain localization between narrow deformation twins. It appears that both the γ' and γ″ play a critical role during low deformation regime while the role of γ″ precipitates becomes significant in high-strain regime. The stabilized cyclic true stress-plastic strain curves follow Ludwik relationship ( σ = Kɛ n ) similar to that of high-strain regime of two-slope tensile curves. The true stress-strain curves show softening during cyclic test in comparison to that of monotonic condition and are independent of sample orientations and locations. The lower degree of cyclic softening associated with radial-oriented sample can be attributed to the alignment of δ-phase precipitates normal to the loading direction. The low ductility and low work-hardening exponent of radial-oriented sample in web region have been explained based on the dislocation storage capacity and dynamic recovery coefficient using Kock-Mecking-Estrin analysis.

  13. Thermal Management in Friction-Stir Welding of Precipitation-Hardened Aluminum Alloys

    NASA Astrophysics Data System (ADS)

    Upadhyay, Piyush; Reynolds, Anthony P.

    2015-05-01

    Process design and implementation in friction-stir welding (FSW) is mostly dependent on empirical information. Basic science of FSW and processing can only be complete when fundamental interrelationships between the process control parameters and response variables and the resulting weld microstructure and properties are established to a reasonable extent. It is known that primary process control parameters such as tool rotation, translation rates, and forge axis force have complicated and interactive relationships to process-response variables such as peak temperature and time at temperature. Of primary influence on the other process-response parameters are temperature and its gradient in the deformation and heat-affected zones. Through a review of pertinent works in the literature and results from boundary condition experiments performed in precipitation-hardening aluminum alloys, this article partially elucidates the nature and effects of temperature transients caused by variation of thermal boundaries in FSW.

  14. Thermal Management in Friction-Stir Welding of Precipitation-Hardening Aluminum Alloys

    SciTech Connect

    Upadhyay, Piyush; Reynolds, Anthony

    2015-05-25

    Process design and implementation in FSW is mostly dependent on empirical information gathered through experience. Basic science of friction stir welding and processing can only be complete when fundamental interrelationships between process control parameters and response variables and resulting weld microstructure and properties are established to a reasonable extent. It is known that primary process control parameters like tool rotation and translation rate and forge axis force have complicated and interactive relationships to the process response variables such as peak temperature, time at temperature etc. Of primary influence to the other process response parameters are temperature and its gradient at the deformation and heat affected zones. Through review of pertinent works in the literature and some experimental results from boundary condition work performed in precipitation hardening aluminum alloys this paper will partially elucidate the nature and effects of temperature transients caused by variation of thermal boundaries in Friction Stir Welding.

  15. The development of high strength corrosion resistant precipitation hardening cast steels

    NASA Astrophysics Data System (ADS)

    Abrahams, Rachel A.

    Precipitation Hardened Cast Stainless Steels (PHCSS) are a corrosion resistant class of materials which derive their properties from secondary aging after a normalizing heat treatment step. While PHCSS materials are available in austenitic and semi-austenitic forms, the martensitic PHCSS are most widely used due to a combination of high strength, good toughness, and corrosion resistance. If higher strength levels can be achieved in these alloys, these materials can be used as a lower-cost alternative to titanium for high specific strength applications where corrosion resistance is a factor. Although wrought precipitation hardened materials have been in use and specified for more than half a century, the specification and use of PHCSS has only been recent. The effects of composition and processing on performance have received little attention in the cast steel literature. The work presented in these investigations is concerned with the experimental study and modeling of microstructural development in cast martensitic precipitation hardened steels at high strength levels. Particular attention is focused on improving the performance of the high strength CB7Cu alloy by control of detrimental secondary phases, notably delta ferrite and retained austenite, which is detrimental to strength, but potentially beneficial in terms of fracture and impact toughness. The relationship between age processing and mechanical properties is also investigated, and a new age hardening model based on simultaneous precipitation hardening and tempering has been modified for use with these steels. Because the CB7Cu system has limited strength even with improved processing, a higher strength prototype Fe-Ni-Cr-Mo-Ti system has been designed and adapted for use in casting. This prototype is expected to develop high strengths matching or exceed that of cast Ti-6Al-4V alloys. Traditional multicomponent constitution phase diagrams widely used for phase estimation in conventional stainless steels

  16. Influence of cold rolling degree and ageing treatments on the precipitation hardening of 2024 and 7075 alloys

    NASA Astrophysics Data System (ADS)

    Naimi, A.; Yousfi, H.; Trari, M.

    2013-08-01

    In the present work, the precipitation hardening of 2024 and 7075 aluminum alloys is investigated as a function of cold rolling degree, ageing time and temperature using Vickers microhardness measurements and differential scanning calorimetry (DSC). It is found that a variation in such parameters can improve the hardness and plays an important role in the precipitation hardening process. At specific ageing temperature, the large cold rolled 7075 alloy exhibits two peaks of hardness. Moreover, for both alloys, the increment of hardness during ageing decreases with increasing the cold rolling degree. While in some cases microhardness measurements give impression that the precipitation reaction is slowed down by deformation, DSC analysis indicates that the precipitation is much accelerated since only a slight deformation decreases strongly the temperatures of reactions. However, the degree of cold rolling does not play a crucial role.

  17. Mechanisms of formation of hardening precipitates and hardening in aging of Al-Li-Cu-Mg model alloys with silver additions

    NASA Astrophysics Data System (ADS)

    Alekseev, A. A.; Zhuravleva, P. L.; Onuchina, M. R.; Klochkova, Yu. Yu.

    2015-11-01

    The mechanisms of the influence of silver additions on the phase transformations that occur in aging are revealed. The contribution of Ω'-phase particles to the deformation stress in Al alloys is estimated. The mechanisms of the effect of low (up to 0.5 wt %) silver additions and the copper content on the structure of the Ω'-phase precipitates in Al alloys are found. According to the proposed model, silver atoms remain immobile during the decomposition of a solid solution and nucleation centers of the Ω' phase form near them in low-temperature aging. Upon hardening aging, fragmented Ω'-phase particles intersect with each other, and the contribution of the intersection regions to the hardening of alloys by Ω'-phase particles is principal.

  18. Precipitation hardening and microstructure evolution of the Ti-7Nb-10Mo alloy during aging.

    PubMed

    Yi, Ruowei; Liu, Huiqun; Yi, Danqing; Wan, Weifeng; Wang, Bin; Jiang, Yong; Yang, Qi; Wang, Dingchun; Gao, Qi; Xu, Yanfei; Tang, Qian

    2016-06-01

    A biomedical β titanium alloy (Ti-7Nb-10Mo) was designed and prepared by vacuum arc self-consumable melting. The ingot was forged and rolled to plates, followed by quenching and aging. Age-hardening behavior, microstructure evolution and its influence on mechanical properties of the alloy during aging were investigated, using X-ray diffraction, transmission electron microscopy, tensile and hardness measurements. The electrochemical behavior of the alloy was investigated in Ringer's solution. The microstructure of solution-treated (ST) alloy consists of the supersaturated solid solution β phase and the ωath formed during athermal process. The ST alloy exhibits Young's modulus of 80 GPa, tensile strength of 774 MPa and elongation of 20%. The precipitation sequences during isothermal aging at different temperatures were determined as β+ωath→β+ωiso (144 h) at Taging=350-400 °C, β+ωath→β+ωiso+α→β+α at Taging=500°C, and β+ωath→β+α at Taging=600-650 °C, where ωiso forms during isothermal process. The mechanical properties of the alloy can be tailored easily through controlling the phase transition during aging. Comparing with the conventional Ti-6Al-4V alloy, the Ti-7Nb-10Mo alloy is more resistant to corrosion in Ringer's solution. Results show that the Ti-7Nb-10Mo alloy is promising for biomedical applications. PMID:27040253

  19. Measurement of irradiation effects in precipitate hardened aluminum using nonlinear ultrasonic principles (in-situ)

    NASA Astrophysics Data System (ADS)

    Reinhardt, B. T.; Parks, D. A.; Tittmann, B. R.

    2012-05-01

    Currently nuclear power plants are reaching the end of their initial design life. Yet, in order to meet the energy demands, twenty year extensions have been granted to many nuclear reactor facilities. These extensions will be ending by the year 2035, leaving a large gap in the available energy supply. In order to extend the life of these facilities it will imperative to develop techniques capable detecting damage in the aging nuclear facilities. However, the high temperature and high neutron flux environment limits the materials available for use in the nuclear reactor. Because of this limitation little NDE based inspection has been implemented in high radiation environments. Yet recent developments in the understanding of Aluminum Nitride (AlN) piezoelectric sensors high temperature and radiation dependent behavior have opened the door for in-situ experimentation. An experiment was designed to monitor the propagation of an ultrasonic wave in a precipitate hardened aluminum specimen while being subjected to radiation at the Pennsylvania State Universities Breazeale Reactor. Measurements of harmonic generation were made up to 1.85×1018 fluence with significant spectral difference between the pre-irradiated state and the post irradiated state. The connection between micro-structural material changes and harmonic measurements are addressed.

  20. Linear Friction Welding Process Model for Carpenter Custom 465 Precipitation-Hardened Martensitic Stainless Steel

    NASA Astrophysics Data System (ADS)

    Grujicic, M.; Yavari, R.; Snipes, J. S.; Ramaswami, S.; Yen, C.-F.; Cheeseman, B. A.

    2014-06-01

    An Arbitrary Lagrangian-Eulerian finite-element analysis is combined with thermo-mechanical material constitutive models for Carpenter Custom 465 precipitation-hardened martensitic stainless steel to develop a linear friction welding (LFW) process model for this material. The main effort was directed toward developing reliable material constitutive models for Carpenter Custom 465 and toward improving functional relations and parameterization of the workpiece/workpiece contact-interaction models. The LFW process model is then used to predict thermo-mechanical response of Carpenter Custom 465 during LFW. Specifically, temporal evolutions and spatial distribution of temperature within, and expulsion of the workpiece material from, the weld region are examined as a function of the basic LFW process parameters, i.e., (a) contact-pressure history, (b) reciprocation frequency, and (c) reciprocation amplitude. Examination of the results obtained clearly revealed the presence of three zones within the weld, i.e., (a) Contact-interface region, (b) Thermo-mechanically affected zone, and (c) heat-affected zone. While there are no publicly available reports related to Carpenter Custom 465 LFW behavior, to allow an experiment/computation comparison, these findings are consistent with the results of our ongoing companion experimental investigation.

  1. Formation quality optimization of laser hot wire cladding for repairing martensite precipitation hardening stainless steel

    NASA Astrophysics Data System (ADS)

    Wen, Peng; Feng, Zhenhua; Zheng, Shiqing

    2015-01-01

    Laser cladding is an advantaged repairing technology due to its low heat input and high flexibility. With preheating wire by resistance heat, laser hot wire cladding shows better process stability and higher deposition efficiency compared to laser cold wire/powder cladding. Multi-pass layer were cladded on the surface of martensite precipitation hardening stainless steel FV520B by fiber laser with ER410NiMo wire. Wire feed rate and preheat current were optimized to obtain stable wire transfer, which guaranteed good formation quality of single pass cladding. Response surface methodology (RSM) was used to optimize processing parameters and predict formation quality of multi-pass cladding. Laser power P, scanning speed Vs, wire feed rate Vf and overlap ratio η were selected as the input variables, while flatness ratio, dilution and incomplete fusion value as the responses. Optimal clad layer with flat surface, low dilution and no incomplete fusion was obtained by appropriately reducing Vf, and increasing P, Vs and η. No defect like pore or crack was found. The tensile strength and impact toughness of the clad layer is respectively 96% and 86% of those of the substrate. The clad layer showed nonuniform microstructure and was divided into quenched areas with coarse lath martensite and tempered areas with tempered martensite due to different thermal cycles in adjacent areas. The tempered areas showed similar hardness to the substrate.

  2. Properties of precipitation hardened steel irradiated at 323 K in the Japan materials testing reactor

    NASA Astrophysics Data System (ADS)

    Niimi, M.; Matsui, Y.; Jitsukawa, S.; Hoshiya, T.; Tsukada, T.; Ohmi, M.; Mimura, H.; Ooka, N.; Hide, K.

    A precipitation hardening type 630 stainless steel was irradiated in the Japan Materials Testing Reactor (JMTR) in contact with the reactor primary coolant. The temperature of the irradiated specimens was about 330 K. The fast neutron ( E > 1 MeV) fluence for the specimens ranged from 10 24 to 10 26 m -2. Tension tests and fracture toughness tests were carried out at room temperature, while Charpy impact tests were done at temperatures of 273-453 K. Tensile strength data showed a peak of 1600 MPa at around 7 × 10 24 m -2, then gradually decreased to about 1500 MPa at 1.2 × 10 26 m -2. The elongation decreased with irradiation from 12% for unirradiated material to 6% at 1.2 × 10 26 m -2. The fractography after the tension test revealed that the fracture was ductile. Fracture toughness decreased to about a half of the value for unirradiated material with irradiation. The cleavage fracture was dominant on the fractured surface. Charpy impact tests showed an increase of ductile-brittle transition temperature (DBTT) by 60 K with irradiation.

  3. Age-hardening behaviors and grain boundary discontinuous precipitation in a Pd-free gold alloy for porcelain bonding.

    PubMed

    Shiraishi, Takanobu; Ohta, Michio

    2002-10-01

    Isothermal age-hardening behaviors at 400 degrees and 450 degrees C and discontinuous precipitation reaction at 450 degrees C in a commercial Pd-free gold alloy for porcelain bonding were investigated by hardness testing, X-ray powder diffraction, and light microscopy. Variations of electrical resistivity during continuous heating and cooling processes were also measured. The alloy exhibited pronounced age-hardening in the early stage of aging and the maximum hardness exceeded twice that of the solution-treated sample. Precise lattice parameter measurements and investigations of full width at half maximum values for the X-ray Bragg reflections implied that nonuniform strains due to the pre-precipitation or zone formation was responsible for the quick and pronounced age-hardening at 450 degrees C. Discontinuous precipitation reaction, producing a mixture of a small amount of Pt(3)In-phase with the L1(2)-type superstructure and a large amount of (Pt, In)-depleted solid solution, started at grain boundaries in the late stage of aging process at 450 degrees C. The growth of the grain boundary discontinuous precipitates toward the intragrain area led to a gradual decrease in hardness of the alloy. PMID:15348193

  4. Modelling of the effect of precipitates on work-hardening, ductility and impact behaviour of ferritic-martensitic Cr steels

    NASA Astrophysics Data System (ADS)

    Preininger, D.

    2002-12-01

    The effect of precipitates on work-hardening, tensile ductility and impact behaviour of carbon and high nitrogen martensitic 7-12Cr as well as particle strengthened ODS-(9-13)Cr steels have been analysed by models. A minimum of work-hardening and uniform strain generally appears around 600 °C at onset of dislocation recovery. Pronounced precipitation by increasing nitrogen and carbon content or additionally of fine Y 2O 3-particles distinctly increases work-hardening and uniform ductility. These, however, decrease with increasing strengthening but do not reach a visible level above 1500 MPa for ODS-steels at 20 °C. Minima of total elongation and fracture strain additionally appear in carbon and nitrogen martensitic steels around 300 °C where dynamic strain ageing occurs. Fracture strain and ductile upper shelf energy of Charpy tests in accordance with model predictions also decrease with increasing yield strength more strongly for ODS-steels due to their enhanced work-hardening and localized deformation. The strength-induced increase of ductile-to-brittle transition temperatures of ODS-steels is comparable to that observed by irradiation defect strengthening.

  5. Production and Precipitation Hardening of Beta-Type Ti-35Nb-10Cu Alloy Foam for Implant Applications

    NASA Astrophysics Data System (ADS)

    Mutlu, Ilven; Yeniyol, Sinem; Oktay, Enver

    2016-04-01

    In this study, beta-type Ti-35Nb-10Cu alloy foams were produced by powder metallurgy method for dental implant applications. 35% Nb was added to stabilize the beta-Ti phase with low Young's modulus. Cu addition enhanced sinterability and gave precipitation hardening capacity to the alloy. Sintered specimens were precipitation hardened in order to enhance the mechanical properties. Electrochemical corrosion behavior of the specimens was examined by electrochemical impedance spectroscopy in artificial saliva. Electrochemical impedance spectroscopy results indicated that the oxide film on the surface of foam is a bi-layer structure consisting of outer porous layer and inner barrier layer. Impedance values of barrier layer were higher than porous layer. Corrosion resistance of specimens decreased at high fluoride concentrations and at low pH of artificial saliva. Corrosion resistance of alloys was slightly decreased with aging. Mechanical properties, microstructure, and surface roughness of the specimens were also examined.

  6. Effect of Al Addition on ω Precipitation and Age Hardening of Ti-Al-Mo-Fe Alloys

    NASA Astrophysics Data System (ADS)

    Li, Chenglin; Lee, Dong-Geun; Mi, Xujun; Ye, Wenjun; Hui, Songxiao; Lee, Yongtai

    2016-05-01

    The effect of Al addition on ω precipitation and age-hardening behavior of Ti-9.2Mo-2Fe and Ti-2Al-9.2Mo-2Fe alloy during aging treatment was investigated. The results showed that athermal and isothermal ω phase formation in Ti-2Al-9.2Mo-2Fe alloy was suppressed to a certain extent due to Al addition. In addition, a small amount of athermal ω phase was observed in the β matrix with a size of about ~5 nm during water quenching from above the β transus temperature for both alloys. Isothermal ω formation was also found during aging at temperatures ranging from 573 K to 773 K (300 °C to 500 °C) in both alloys, although it had a limited time of stability at 773 K (500 °C). The hardening due to isothermal ω precipitation exhibited no over-aging as long as ω phase existed in both alloys, and ω phase played a more important role in hardening than α phase. And the ω phase in 50 to 100 nm size exhibited the best hardening effect in Ti-9.2Mo-2Fe alloy. Similarly, α phase with 100 to 200 nm in length showed better hardening effects in Ti-2Al-9.2Mo-2Fe alloy. Both the alloys showed stronger age hardening at an intermediate temperature of 673 K (400 °C) and in the first aging stage at a higher temperature of 773 K (500 °C) due to the sufficiently fine size (50 nm), while they exhibited weaker age hardening at a lower temperature of 573 K (300 °C) and long period aging at a higher temperature of 773 K (500 °C) due to incomplete ω formation and/or coarsening of α phase. No over or peak aging stage was found at 573 K and 673 K (300 °C and 400 °C) during the aging for 72 hours, while the peak hardness values of both alloys aged at 773 K (500 °C) were obtained in the first stage of aging. The hardness of the alloys was very sensitive to size and volume fraction of ω phase, which depends on aging temperature, time, and composition of the involved alloys.

  7. Biocompatibility of 17-4 PH stainless steel foam for implant applications.

    PubMed

    Mutlu, Ilven; Oktay, Enver

    2011-01-01

    In this study, biocompatibility of 17-4 PH stainless steel foam for biomedical implant applications was investigated. 17-4 PH stainless steel foams having porosities in the range of 40-82% with an average pore size of around 600 μm were produced by space holder-sintering technique. Sintered foams were precipitation hardened for times of 1-6 h at temperatures between 450-570 °C. Compressive yield strength and Young's modulus of aged stainless steel foams were observed to vary between 80-130 MPa and 0.73-1.54 GPa, respectively. Pore morphology, pore size and the mechanical properties of the 17-4 PH stainless steel foams were close to cancellous bone. In vitro evaluations of cytotoxicity of the foams were investigated by XTT and MTT assays and showed sufficient biocompatibility. Surface roughness parameters of the stainless steel foams were also determined to characterize the foams. PMID:22182790

  8. Surface Hardening and Nitride Precipitation in the Nitriding of Fe-M1-M2 Ternary Alloys Containing Al, V, or Cr

    NASA Astrophysics Data System (ADS)

    Miyamoto, Goro; Suetsugu, Shotaro; Shinbo, Kunio; Furuhara, Tadashi

    2015-11-01

    Nitride precipitation and resultant surface hardening in nitrided Fe-M1-M2 ternary alloys containing Cr, Al, or V were investigated using transmission electron microscopy and three-dimensional atom probe tomography. The (Al, Cr) and (Cr, V) mixed nitrides are formed by the co-precipitation of these elements during the nitriding of Fe-Al-Cr or Fe-Cr-V alloys. However, the precipitation of V nitrides precedes Al nitride precipitation during the nitriding of the Fe-Al-V alloy, which results in two-step hardening behavior. The addition of Cr or V to the Fe-Al alloy accelerates the precipitation kinetics of Al nitrides by promoting the nucleation of Al nitrides, which leads to substantial surface hardening.

  9. The influence of copper precipitation and plastic deformation hardening on the impact-transition temperature of rolled structural steels

    NASA Astrophysics Data System (ADS)

    Aróztegui, Juan J.; Urcola, José J.; Fuentes, Manuel

    1989-09-01

    Commercial electric arc melted low-carbon steels, provided as I beams, were characterized both microstructurally and mechanically in the as-rolled, copper precipitation, and plastically pre-deformed conditions. Inclusion size distribution, ferrite grain size, pearlite volume fraction, precipitated volume fraction of copper, and size distribution of these precipitates were deter-mined by conventional quantitative optical and electron metallographic techniques. From the tensile tests conducted at a strain rate of 10-3 s-1 and impact Charpy V-notched tests carried out, stress/strain curves, yield stress, and impact-transition temperature were obtained. The spe-cific fractographic features of the fracture surfaces also were quantitatively characterized. The increases in yield stress and transition temperature experienced upon either aging or work hard-ening were related through empirical relationships. These dependences were analyzed semi-quantitatively by combining microscopic and macroscopic fracture criteria based on measured fundamental properties (fracture stress and yield stress) and observed fractographic parameters (crack nucleation distance and nuclei size). The rationale developed from these fracture criteria allows the semiquantitative prediction of the temperature transition shifts produced upon aging and work hardening. The values obtained are of the right order of magnitude.

  10. Initial precipitation and hardening mechanism during non-isothermal aging in an Al–Mg–Si–Cu 6005A alloy

    SciTech Connect

    Yang, Wenchao; Ji, Shouxun; Huang, Lanping; Sheng, Xiaofei; Li, Zhou; Wang, Mingpu

    2014-08-15

    The characterization of precipitation and hardening mechanism during non-isothermal aging had been investigated using high resolution transmission electron microscopy for an Al–Mg–Si–Cu 6005A alloy. It was proposed that the needle-shaped β″ precipitates with a three-dimension coherency strain-field and an increased number density in the Al matrix provided the maximum strengthening effect for the Al–Mg–Si–Cu 6005A alloy. Simultaneously, it was also found that the formation and evolution of clusters in the early precipitation were associated with the vacancy binding energy, during which Si atoms played an important role in controlling the numbers density of Mg/Si co-clusters, and the excess Si atoms provided the increased number of nucleation sites for the subsequent precipitates to strengthen and improve the precipitation rate. Finally, based on the experimental observation and theoretical analysis, the precipitation sequence during the early precipitation in the Al–Mg–Si–Cu 6005A alloy was proposed as: supersaturated solid solution → Si-vacancy pairs, Mg-vacancy pairs and Mg clusters → Si clusters, and dissolution of Mg clusters → Mg atoms diffusion into the existing Si clusters → Mg/Si co-clusters → GP zone. - Highlights: • β″ precipitates provide the maximum strengthening effect for the 6005A alloy. • Si atoms play an important role in controlling the numbers of Mg/Si co-clusters. • The early aging sequence is deduced based on the solute-vacancy binding energy.

  11. Solution and precipitation hardening in carbon-doped two-phase {gamma}-titanium aluminides

    SciTech Connect

    Appel, F.; Christoph, U.; Wagner, R.

    1997-12-31

    A two-phase titanium aluminide alloy was systematically doped with carbon to improve its high temperature strength. Solid solutions and precipitates of carbon were formed by different thermal treatments. A fine dispersion of perovskite precipitates was found to be very effective for improving the high temperature strength and creep resistance of the material. The strengthening mechanisms were characterized by flow stresses and activation parameters. The investigations were accompanied by electron microscope observation of the defect structure which was generated during deformation. Special attention was paid on the interaction mechanisms of perfect and twinning dislocations with the carbide precipitates.

  12. Influence of Pre-straining and Heat Treatment on the Yield Surface of Precipitation Hardenable Aluminum Alloys

    NASA Astrophysics Data System (ADS)

    Lechner, Michael; Johannes, Maren; Kuppert, Andreas; Merklein, Marion

    Precipitation hardenable aluminum alloys are some of the most important lightweight materials. However, their range of applications in comparison to conventional deep drawing steels is limited by the low formability. Therefore, a new and innovative approach to enhance the formability of aluminum alloys in multistage forming operations was invented at the Institute of Manufacturing Technology, called intermediate heat treatment (IHT). Based on a short-term, laser-assisted heat treatment between two forming steps, it is possible to locally adapt the mechanical properties and realize an optimized strength distribution. For the successful application of the technology, the influence of the heat treatment on the mechanical properties has to be analyzed. Concerning the simulation of a multistage forming process, in particular, the yield surface of the material is very important. Within this paper, the influence of a combined pre-straining and a subsequent short-term, laser-assisted heat treatment on the yield surface will be presented.

  13. Precipitation hardenable iron-nickel-chromium alloy having good swelling resistance and low neutron absorbence

    DOEpatents

    Korenko, Michael K.; Merrick, Howard F.; Gibson, Robert C.

    1980-01-01

    An iron-nickel-chromium age-hardenable alloy suitable for use in fast breeder reactor ducts and cladding which utilizes the gamma-double prime strengthening phase and characterized in having a morphology of the gamma-double prime phase enveloping the gamma-prime phase and delta phase distributed at or near the grain boundaries. The alloy consists essentially of about 40-50% nickel, 7.5-14% chromium, 1.5-4% niobium, 0.25-0.75% silicon, 1-3% titanium, 0.1-0.5% aluminum, 0.02-0.1% carbon, 0.002-0.015% boron, and the balance iron. Up to 2% manganese and up to 0.01% magnesium may be added to inhibit trace element effects; up to 0.1% zirconium may be added to increase radiation swelling resistance; and up to 3% molybdenum may be added to increase strength.

  14. Microstructure and Crystallographic Texture Evolution During the Friction-Stir Processing of a Precipitation-Hardenable Aluminum Alloy

    NASA Astrophysics Data System (ADS)

    Nadammal, Naresh; Kailas, Satish V.; Szpunar, Jerzy; Suwas, Satyam

    2015-05-01

    Friction-stir processing (FSP) has been proven as a successful method for the grain refinement of high-strength aluminum alloys. The most important attributes of this process are the fine-grain microstructure and characteristic texture, which impart suitable properties in the as-processed material. In the current work, FSP of the precipitation-hardenable aluminum alloy 2219 has been carried out and the consequent evolution of microstructure and texture has been studied. The as-processed materials were characterized using electron back-scattered diffraction, x-ray diffraction, and electron probe microanalysis. Onion-ring formation was observed in the nugget zone, which has been found to be related to the precipitation response and crystallographic texture of the alloy. Texture development in the alloy has been attributed to the combined effect of shear deformation and dynamic recrystallization. The texture was found heterogeneous even within the nugget zone. A microtexture analysis revealed the dominance of shear texture components, with C component at the top of nugget zone and the B and A2* components in the middle and bottom. The bulk texture measurement in the nugget zone revealed a dominant C component. The development of a weaker texture along with the presence of some large particles in the nugget zone indicates particle-stimulated nucleation as the dominant nucleation mechanism during FSP. Grain growth follows the Burke and Turnbull mechanism and geometrical coalescence.

  15. Liquation Microfissuring in the Weld Heat-Affected Zone of an Overaged Precipitation-Hardened Nickel-Base Superalloy

    NASA Astrophysics Data System (ADS)

    Ojo, O. A.; Chaturvedi, M. C.

    2007-02-01

    The effect of preweld overaging heat treatment on the microstructural response in the heat-affected zone (HAZ) of a precipitation-hardened nickel-base superalloy INCONEL 738LC subjected to the welding thermal cycle ( i.e., rapid) was investigated. The overaging heat treatment resulted in the formation of an interfacial microconstituent containing M23X6 particles and coarsening of primary and secondary γ' precipitates. The HAZ microstructures around welds in the overaged alloy were simulated using the Gleeble thermomechanical simulation system. Microstructural examination of simulated HAZs and those present in tungsten inert gas (TIG) welded specimens showed the occurrence of extensive grain boundary liquation involving liquation reaction of the interfacial microconstituents containing M23X6 particles and MC-type carbides. In addition, the coarsened γ' precipitate particles present in the overaged alloy persisted well above their solvus temperature to temperatures where they constitutionally liquated and contributed to considerable liquation of grain boundaries, during continuous rapid heating. Intergranular HAZ microfissuring, with resolidified product formed mostly on one side of the microfissures, was observed in welded specimens. This suggested that the HAZ microfissuring generally occurred by decohesion across one of the solid-liquid interfaces during the grain boundary liquation stage of the weld thermal cycle. Correlation of simulated HAZ microstructures with hot ductility properties of the alloy revealed that the temperature at which the alloy exhibited zero ductility during heating was within the temperature range at which grain boundary liquation was observed. The on-cooling ductility of the alloy was significantly damaged by the on-heating liquation reaction, as reflected by the considerably low ductility recovery temperature (DRT). Important characteristics of the intergranular liquid that could influence HAZ microfissuring of the alloy in overaged

  16. Additive Manufacturing of 17-4 PH Stainless Steel: Post-processing Heat Treatment to Achieve Uniform Reproducible Microstructure

    NASA Astrophysics Data System (ADS)

    Cheruvathur, Sudha; Lass, Eric A.; Campbell, Carelyn E.

    2016-03-01

    17-4 precipitation hardenable (PH) stainless steel is a useful material when a combination of high strength and good corrosion resistance up to about 315°C is required. In the wrought form, this steel has a fully martensitic structure that can be strengthened by precipitation of fine Cu-rich face-centered cubic phase upon aging. When fabricated via additive manufacturing (AM), specifically laser powder-bed fusion, 17-4 PH steel exhibits a dendritic structure containing a substantial fraction of nearly 50% of retained austenite along with body centered cubic/martensite and fine niobium carbides preferentially aligned along interdendritic boundaries. The effect of post-build thermal processing on the material microstructure is studied in comparison to that of conventionally produced wrought 17-4 PH with the intention of creating a more uniform, fully martensitic microstructure. The recommended stress relief heat treatment currently employed in industry for post-processing of AM 17-4 PH steel is found to have little effect on the as-built dendritic microstructure. It is found that, by implementing the recommended homogenization heat treatment regimen of Aerospace Materials Specification 5355 for CB7Cu-1, a casting alloy analog to 17-4 PH, the dendritic solidification structure is eliminated, resulting in a microstructure containing about 90% martensite with 10% retained austenite.

  17. Microstructure and mechanical properties of hot wire laser clad layers for repairing precipitation hardening martensitic stainless steel

    NASA Astrophysics Data System (ADS)

    Wen, Peng; Cai, Zhipeng; Feng, Zhenhua; Wang, Gang

    2015-12-01

    Precipitation hardening martensitic stainless steel (PH-MSS) is widely used as load-bearing parts because of its excellent overall properties. It is economical and flexible to repair the failure parts instead of changing new ones. However, it is difficult to keep properties of repaired part as good as those of the substrate. With preheating wire by resistance heat, hot wire laser cladding owns both merits of low heat input and high deposition efficiency, thus is regarded as an advantaged repairing technology for damaged parts of high value. Multi-pass layers were cladded on the surface of FV520B by hot wire laser cladding. The microstructure and mechanical properties were compared and analyzed for the substrate and the clad layer. For the as-cladded layer, microstructure was found non-uniform and divided into quenched and tempered regions. Tensile strength was almost equivalent to that of the substrate, while ductility and impact toughness deteriorated much. With using laser scanning layer by layer during laser cladding, microstructure of the clad layers was tempered to fine martensite uniformly. The ductility and toughness of the clad layer were improved to be equivalent to those of the substrate, while the tensile strength was a little lower than that of the substrate. By adding TiC nanoparticles as well as laser scanning, the precipitation strengthening effect was improved and the structure was refined in the clad layer. The strength, ductility and toughness were all improved further. Finally, high quality clad layers were obtained with equivalent or even superior mechanical properties to the substrate, offering a valuable technique to repair PH-MSS.

  18. Failure Maps for Rectangular 17-4PH Stainless Steel Sandwiched Foam Panels

    NASA Technical Reports Server (NTRS)

    Raj, S. V.; Ghosn, L. J.

    2007-01-01

    A new and innovative concept is proposed for designing lightweight fan blades for aircraft engines using commercially available 17-4PH precipitation hardened stainless steel. Rotating fan blades in aircraft engines experience a complex loading state consisting of combinations of centrifugal, distributed pressure and torsional loads. Theoretical failure plastic collapse maps, showing plots of the foam relative density versus face sheet thickness, t, normalized by the fan blade span length, L, have been generated for rectangular 17-4PH sandwiched foam panels under these three loading modes assuming three failure plastic collapse modes. These maps show that the 17-4PH sandwiched foam panels can fail by either the yielding of the face sheets, yielding of the foam core or wrinkling of the face sheets depending on foam relative density, the magnitude of t/L and the loading mode. The design envelop of a generic fan blade is superimposed on the maps to provide valuable insights on the probable failure modes in a sandwiched foam fan blade.

  19. Ageing behaviour of an Fe-20Ni-1.8Mn-1.6Ti-0.59Al (wt%) maraging alloy: clustering, precipitation and hardening

    SciTech Connect

    Pereloma, E.V. . E-mail: elena.pereloma@spme.monash.edu.au; Shekhter, A.; Miller, M.K.; Ringer, S.P.

    2004-11-08

    Changes in the solute distribution as well as the evolution of precipitation, microstructure and mechanical properties have been studied in an experimental maraging Fe-20Ni-1.8Mn-1.5Ti-0.59Al (wt%) alloy during ageing at 550 deg C. An initial hardening reaction within 5 s is reported, which is remarkable in terms of extent and rapidity. This strengthening was caused by the formation of complex multi-component atomic co-clusters containing primarily Ni-Ti-Al as well as some Mn. This cluster strengthened condition produced the optimum toughness observed throughout the ageing sequence. After 60 s ageing, the appearance of discrete precipitation of needle-shaped {eta}-Ni{sub 3}Ti particles was associated with a second rise in hardness towards an eventual peak at 600 s. This precipitation hardening was accompanied by an increase in tensile strength and a decrease in ductility. A reverse transformation of martensite to austenite occurs progressively during ageing and this contributes to the initial and secondary softening.

  20. Evaluation of Solid-Solution Hardening of Fe-27 at. pct Al by Vanadium and Comparison to Precipitation Strengthening by Vanadium Carbides

    NASA Astrophysics Data System (ADS)

    Kratochvíl, Petr; Pešička, Josef; Král, Robert; Švec, Martin; Palm, Martin

    2015-11-01

    The compressive yield stress of Fe-27Al- xV(-C) ( x = 0 to 4 at. pct) at 1073 K (800 °C) has been determined. The increase of the yield stress of Fe-Al by increasing vanadium content is explained by solid-solution hardening. The experimentally observed values of the yield stress at 1073 K (800 °C) are compared with the strengthening given by theories evaluating the interaction between solute atoms and dislocations. The experimental results fit well the increase of the yield stress by the interaction of the solute atoms with screw dislocations. Further increase in yield strength in similar alloys due to vanadium carbides is documented. Precipitated carbides were identified by transmission electron microscopy and Kikuchi patterns. Although precipitation of vanadium carbides increases the compressive yield stress, they also could result in premature failure in tension as their highly anisotropic shape may facilitate crack nucleation.

  1. Influence of Thermal Aging on the Microstructure and Mechanical Behavior of Dual-Phase, Precipitation-Hardened, Powder Metallurgy Stainless Steels

    NASA Astrophysics Data System (ADS)

    Stewart, J. L.; Williams, J. J.; Chawla, N.

    2012-01-01

    The effects of thermal aging on the microstructure and mechanical behavior of dual-phase, precipitation-hardened, powder metallurgy (PM) stainless steels of varying ferrite-martensite content were examined. Quantitative analyses of the inherent porosity and phase fractions were conducted on the steels, and no significant differences were noted with respect to aging temperature. Tensile strength, yield strength, and elongation to fracture all increased with increasing aging temperature reaching maxima at 811 K (538 °C) in most cases. Increased strength and decreased ductility were observed in steels of higher martensite content. Nanoindentation of the individual microconstituents was employed to obtain a fundamental understanding of the strengthening contributions. Both the ferrite and martensite nanohardness values increased with aging temperature and exhibited similar maxima to the bulk tensile properties.

  2. 32 CFR 17.4 - Interlocutory questions.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... trial by military commission. In accordance with 32 CFR 9.4(a)(5)(iv), however, the Presiding Officer... 32 National Defense 1 2010-07-01 2010-07-01 false Interlocutory questions. 17.4 Section 17.4... ADMINISTRATIVE PROCEDURES § 17.4 Interlocutory questions. (a) Certification of interlocutory questions....

  3. 32 CFR 17.4 - Interlocutory questions.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... trial by military commission. In accordance with 32 CFR 9.4(a)(5)(iv), however, the Presiding Officer... 32 National Defense 1 2011-07-01 2011-07-01 false Interlocutory questions. 17.4 Section 17.4... ADMINISTRATIVE PROCEDURES § 17.4 Interlocutory questions. (a) Certification of interlocutory questions....

  4. Radiation-Induced Phase Instabilities and Their Effects on Hardening and Solute Segregation in Precipitation-Strengthened Alloy 718

    SciTech Connect

    Thomas, Larry E.; Sencer, Bulent H.; Bruemmer, Stephen M.

    2001-03-31

    A classic example of radiation-induced phase instability and degraded mechanical properties occurs in g'-g" (gamma prime - gamma double prime) -strengthened alloy 718. During neutron irradiation at 288 degrees C, the Ni3Nb g" particles at grain boundaries and in the matrix disappear after a few dpa. At higher doses, the g' (present only in the matrix) also dissolves and reprecipitates. Hardness is unaffected by disappearance of the g", but decreases as the original g' particles dissolve. Fine-probe compositional measurements in a TEM show that the softening coincides with solute redistribution rather than with the phase disappearance. Compositional changes at grain boundaries included leveling of the thermally segregated Mo as well as strong Ni enrichment and loss of Nb after higher doses. Radiation-induced softening is also observed after irradiations at low temperatures (30-60 degrees C) in a mixed spectrum of protons and spallation neutrons. In this case, both g' and g" completely disappear by 0.6 dpa as the alloy becomes hardened and embrittled. Minor softening occurs at higher doses after the g' and g" have disappeared. The complex phase stability and solute redistribution behavior reflects mainly ballistic mixing at 30-70 degrees C irradiation temperatures and the influence of significant thermal diffusivities at the higher temperatures.

  5. Dispersion strengthening of precipitation hardened Al-Cu-Mg alloys prepared by rapid solidification and mechanical alloying

    NASA Technical Reports Server (NTRS)

    Gilman, P. S.; Sankaran, K. K.

    1988-01-01

    Several Al-4Cu-1Mg-1.5Fe-0.75Ce alloys have been processed from either rapidly solidified or mechanically alloyed powder using various vacuum degassing parameters and consolidation techniques. Strengthening by the fine subgrains, grains, and the dispersoids individually or in combination is more effective when the alloys contain shearable precipitates; consequently, the strength of the alloys is higher in the naturally aged rather than the artificially aged condition. The strengths of the mechanically alloyed variants are greater than those produced from prealloyed powder. Properties and microstructural features of these dispersion strengthened alloys are discussed in regards to their processing histories.

  6. Precipitation Kinetics of M2C Carbide in Severely Ausformed 13Co-8Ni Secondary Hardening Steels

    NASA Astrophysics Data System (ADS)

    Cho, Ki Sub; Park, Sung Soo; Kim, Hong Kyu; Song, Young Beum; Kwon, Hoon

    2015-04-01

    With continuous heating calorimetric data as a basis, the kinetics of M2C formation during isothermal aging was modeled in severely ausformed 13Co-8Ni steels using the Johnson-Mehl-Avrami theory coupled with a variation of effective activation energy with respect to the degree of transformation. These results were compared with small-angle neutron scattering measurements and discussed in terms of variations in the thermodynamic and kinetic behavior of M2C precipitation. In particular, the M2C carbides in the deformed samples contained more Fe content compared with the non-deformed samples. As this can be ascribed to the ausforming effect increasing the driving force for M2C nucleation, it consequently leads to the decrease of the growth/coarsening rate for M2C carbides at over-aged conditions.

  7. Precipitation Hardening and Statistical Modeling of the Aging Parameters and Alloy Compositions in Al-Cu-Mg-Ag Alloys

    NASA Astrophysics Data System (ADS)

    Al-Obaisi, A. M.; El-Danaf, E. A.; Ragab, A. E.; Soliman, M. S.

    2016-04-01

    The addition of Ag to Al-Cu-Mg systems has been proposed to replace the existing high-strength 2xxx and 7xxx Al alloys. The aged Al-Cu-Mg-Ag alloys exhibited promising properties, due to special type of precipitates named Ω, which cooperate with other precipitates to enhance the mechanical properties significantly. In the present investigation, the effect of changing percentages of alloying elements, aging time, and aging temperature on the hardness values was studied based on a factorial design. According to this design of experiments (DOE)—23 factorial design, eight alloys were cast and hot rolled, where (Cu, Mg, and Ag) were added to aluminum with two different levels for each alloying element. These alloys were aged at different temperatures (160, 190, and 220 °C) over a wide range of time intervals from 10 min. to 64 h. The resulting hardness data were used as an input for Minitab software to model and relate the process variables with hardness through a regression analysis. Modifying the alloying elements' weight percentages to the high level enhanced the hardness of the alloy with about 40% as compared to the alloy containing the low level of all alloying elements. Through analysis of variance (ANOVA), it was figured out that altering the fraction of Cu had the greatest effect on the hardness values with a contribution of about 49%. Also, second-level interaction terms had about 21% of impact on the hardness values. Aging time, quadratic terms, and third-level interaction terms had almost the same level of influence on hardness values (about 10% contribution). Furthermore, the results have shown that small addition of Mg and Ag was enough to improve the mechanical properties of the alloy significantly. The statistical model formulated interpreted about 80% of the variation in hardness values.

  8. Precipitation Hardening and Statistical Modeling of the Aging Parameters and Alloy Compositions in Al-Cu-Mg-Ag Alloys

    NASA Astrophysics Data System (ADS)

    Al-Obaisi, A. M.; El-Danaf, E. A.; Ragab, A. E.; Soliman, M. S.

    2016-06-01

    The addition of Ag to Al-Cu-Mg systems has been proposed to replace the existing high-strength 2xxx and 7xxx Al alloys. The aged Al-Cu-Mg-Ag alloys exhibited promising properties, due to special type of precipitates named Ω, which cooperate with other precipitates to enhance the mechanical properties significantly. In the present investigation, the effect of changing percentages of alloying elements, aging time, and aging temperature on the hardness values was studied based on a factorial design. According to this design of experiments (DOE)—23 factorial design, eight alloys were cast and hot rolled, where (Cu, Mg, and Ag) were added to aluminum with two different levels for each alloying element. These alloys were aged at different temperatures (160, 190, and 220 °C) over a wide range of time intervals from 10 min. to 64 h. The resulting hardness data were used as an input for Minitab software to model and relate the process variables with hardness through a regression analysis. Modifying the alloying elements' weight percentages to the high level enhanced the hardness of the alloy with about 40% as compared to the alloy containing the low level of all alloying elements. Through analysis of variance (ANOVA), it was figured out that altering the fraction of Cu had the greatest effect on the hardness values with a contribution of about 49%. Also, second-level interaction terms had about 21% of impact on the hardness values. Aging time, quadratic terms, and third-level interaction terms had almost the same level of influence on hardness values (about 10% contribution). Furthermore, the results have shown that small addition of Mg and Ag was enough to improve the mechanical properties of the alloy significantly. The statistical model formulated interpreted about 80% of the variation in hardness values.

  9. Progress in the R and D Project on Oxide Dispersion Strengthened and Precipitation Hardened Ferritic Steels for Sodium Cooled Fast Breeder Reactor Fuels

    SciTech Connect

    Kaito, Takeji; Ohtsuka, Satoshi; Inoue, Masaki

    2007-07-01

    High burnup capability of sodium cooled fast breeder reactor (SFR) fuels depends significantly on irradiation performance of their component materials. Japan Atomic Energy Agency (JAEA) has been developing oxide dispersion strengthened (ODS) ferritic steels and a precipitation hardened (PH) ferritic steel as the most prospective materials for fuel pin cladding and duct tubes, respectively. Technology for small-scale manufacturing is already established, and several hundreds of ODS steel cladding tubes and dozens of PH steel duct tubes were successfully produced. We will step forward to develop manufacturing technology for mass production to supply these steels for future SFR fuels. Mechanical properties of the products were examined by out-of-pile and in-pile tests including material irradiation tests in the experimental fast reactor JOYO and foreign fast reactors. The material strength standards (MSSs) were tentatively compiled in 2005 for ODS steels and in 1993 for PH steel. In order to upgrade the MSSs and to demonstrate high burnup capability of the materials, we will perform a series of irradiation tests in BOR-60 and JOYO until 2015 and contribute to design study for a demonstration SFR of which operation is expected after 2025. (authors)

  10. 43 CFR 17.4 - Assurances required.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 43 Public Lands: Interior 1 2010-10-01 2010-10-01 false Assurances required. 17.4 Section 17.4 Public Lands: Interior Office of the Secretary of the Interior NONDISCRIMINATION IN FEDERALLY ASSISTED PROGRAMS OF THE DEPARTMENT OF THE INTERIOR Nondiscrimination on the Basis of Race, Color, or...

  11. 43 CFR 17.4 - Assurances required.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 43 Public Lands: Interior 1 2014-10-01 2014-10-01 false Assurances required. 17.4 Section 17.4 Public Lands: Interior Office of the Secretary of the Interior NONDISCRIMINATION IN FEDERALLY ASSISTED PROGRAMS OF THE DEPARTMENT OF THE INTERIOR Nondiscrimination on the Basis of Race, Color, or...

  12. 43 CFR 17.4 - Assurances required.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 43 Public Lands: Interior 1 2011-10-01 2011-10-01 false Assurances required. 17.4 Section 17.4 Public Lands: Interior Office of the Secretary of the Interior NONDISCRIMINATION IN FEDERALLY ASSISTED PROGRAMS OF THE DEPARTMENT OF THE INTERIOR Nondiscrimination on the Basis of Race, Color, or...

  13. 43 CFR 17.4 - Assurances required.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 43 Public Lands: Interior 1 2012-10-01 2011-10-01 true Assurances required. 17.4 Section 17.4 Public Lands: Interior Office of the Secretary of the Interior NONDISCRIMINATION IN FEDERALLY ASSISTED PROGRAMS OF THE DEPARTMENT OF THE INTERIOR Nondiscrimination on the Basis of Race, Color, or...

  14. 43 CFR 17.4 - Assurances required.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 43 Public Lands: Interior 1 2013-10-01 2013-10-01 false Assurances required. 17.4 Section 17.4 Public Lands: Interior Office of the Secretary of the Interior NONDISCRIMINATION IN FEDERALLY ASSISTED PROGRAMS OF THE DEPARTMENT OF THE INTERIOR Nondiscrimination on the Basis of Race, Color, or...

  15. Effect of porosity on ductility variation in investment cast 17-4PH.

    SciTech Connect

    Wright, Robert D.; Kilgo, Alice C.; Grant, Richard P.; Crenshaw, Thomas B.; Susan, Donald Francis

    2005-02-01

    The stainless steel alloy 17-4PH contains a martensitic microstructure and second phase delta ({delta}) ferrite. Strengthening of 17-4PH is attributed to Cu-rich precipitates produced during age hardening treatments at 900-1150 F (H900-H1150). For wrought 17-4PH, the effects of heat treatment and microstructure on mechanical properties are well-documented [for example, Ref. 1]. Fewer studies are available on cast 17-4PH, although it has been a popular casting alloy for high strength applications where moderate corrosion resistance is needed. Microstructural features and defects particular to castings may have adverse effects on properties, especially when the alloy is heat treated to high strength. The objective of this work was to outline the effects of microstructural features specific to castings, such as shrinkage/solidification porosity, on the mechanical behavior of investment cast 17-4PH. Besides heat treatment effects, the results of metallography and SEM studies showed that the largest effect on mechanical properties is from shrinkage/solidification porosity. Figure 1a shows stress-strain curves obtained from samples machined from castings in the H925 condition. The strength levels were fairly similar but the ductility varied significantly. Figure 1b shows an example of porosity on a fracture surface from a room-temperature, quasi-static tensile test. The rounded features represent the surfaces of dendrites which did not fuse or only partially fused together during solidification. Some evidence of local areas of fracture is found on some dendrite surfaces. The shrinkage pores are due to inadequate backfilling of liquid metal and simultaneous solidification shrinkage during casting. A summary of percent elongation results is displayed in Figure 2a. It was found that higher amounts of porosity generally result in lower ductility. Note that the porosity content was measured on the fracture surfaces. The results are qualitatively similar to those found by

  16. Hot Ductility of the 17-4 PH Stainless Steels

    NASA Astrophysics Data System (ADS)

    Herrera Lara, V.; Guerra Fuentes, L.; Covarrubias Alvarado, O.; Salinas Rodriguez, A.; Garcia Sanchez, E.

    2016-03-01

    The mechanisms of loss of hot ductility and the mechanical behavior of 17-4 PH alloys were investigated using hot tensile testing at temperatures between 700 and 1100 °C and strain rates of 10-4, 10-2, and 10-1 s-1. Scanning electron microscopy was used in conjunction with the results of the tensile tests to find the temperature region of loss of ductility and correlate it with cracking observed during processing by hot upsetting prior to ring rolling. It is reported that 17-4 PH alloys lose ductility in a temperature range around 900 °C near to the duplex austenite + ferrite phase field. Furthermore, it is found that niobium carbides precipitated at austenite/ferrite interfaces and grain boundaries have a pronounced effect on the mechanical behavior of the alloy during high-temperature deformation.

  17. Laser-based welding of 17-4 PH martensitic stainless steel in a tubular butt joint configuration with a built-in backing bar

    NASA Astrophysics Data System (ADS)

    Ma, Junjie; Atabaki, Mehdi Mazar; Liu, Wei; Pillai, Raju; Kumar, Biju; Vasudevan, Unnikrishnan; Kovacevic, Radovan

    2016-08-01

    Laser-based welding of thick 17-4 precipitation hardening (PH) martensitic stainless steel (SS) plates in a tubular butt joint configuration with a built-in backing bar is very challenging because the porosity and cracks are easily generated in the welds. The backing bar blocked the keyhole opening at the bottom surface through which the entrapped gas could escape, and the keyhole was unstable and collapsed overtime in a deep partially penetrated welding conditions resulting in the formation of pores easily. Moreover, the fast cooling rate prompted the ferrite transform to austenite which induced cracking. Two-pass welding procedure was developed to join 17-4 PH martensitic SS. The laser welding assisted by a filler wire, as the first pass, was used to weld the groove shoulder. The added filler wire could absorb a part of the laser beam energy; resulting in the decreased weld depth-to-width ratio and relieved intensive restraint at the weld root. A hybrid laser-arc welding or a gas metal arc welding (GMAW) was used to fill the groove as the second pass. Nitrogen was introduced to stabilize the keyhole and mitigate the porosity. Preheating was used to decrease the cooling rate and mitigate the cracking during laser-based welding of 17-4 PH martensitic SS plates.

  18. Role of alloy additions on strengthening in 17-4 PH stainless steel

    NASA Astrophysics Data System (ADS)

    Murthy, Arpana Sudershan

    Alloy modifications by addition of niobium (Nb), vanadium (V), nitrogen (N) and cobalt (Co) to cast 17-4 PH steel were investigated to determine the effect on mechanical properties. Additions of Nb, V, and N increased the yield strength from 1120 MPa to 1310 MPa while decreased the room temperature charpy V notch (CVN) toughness from 20 J to four Joules. The addition of Co to cast 17-4 PH steel enhanced the yield strength and CVN toughness from 1140 MPa to 1290 MPa and from 3.7 J to 5.5 J, respectively. In the base 17-4 PH steel, an increase in block width from 2.27 ± 0.10 μm in the solution treated condition to 3.06 ± 0.17 μm upon aging at 755 K was measured using orientation image microscopy. Cobalt inhibited recrystallization and block boundary migration during aging resulting in a finer martensitic block structure. The influence of Co on copper (Cu) precipitation in steels was studied using atom probe tomography. A narrower precipitate size distribution was observed in the steels with Co addition. The concentration profile across the matrix / precipitate interface indicated rejection of Co atoms from the copper precipitates. This behavior was observed to be energetically favorable using first principle calculations. The activation energies for Cu precipitation increased from 205 kJ/ mol in the non-cobalt containing alloy, to 243 kJ/ mol, and 272 kJ/ mol in alloys with 3 wt. %Co, and 7 wt. % Co, respectively. The role of Co on Cu precipitation in cast 17-4 PH steel is proposed as follows: (i) Co is rejected out of the Cu precipitate and sets up a barrier to the growth of the Cu precipitate; (ii) results in Cu precipitates of smaller size and narrower distribution; (iii) the coarsening of Cu precipitates is inhibited; and (iv) the activation energy for Cu precipitation increases.

  19. 22 CFR 17.4 - Equity and good conscience.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 22 Foreign Relations 1 2011-04-01 2011-04-01 false Equity and good conscience. 17.4 Section 17.4 Foreign Relations DEPARTMENT OF STATE PERSONNEL OVERPAYMENTS FROM THE FOREIGN SERVICE RETIREMENT AND... PENSION SYSTEM (FSPS) § 17.4 Equity and good conscience. (a) Defined. Recovery is against equity and...

  20. 22 CFR 17.4 - Equity and good conscience.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 22 Foreign Relations 1 2014-04-01 2014-04-01 false Equity and good conscience. 17.4 Section 17.4 Foreign Relations DEPARTMENT OF STATE PERSONNEL OVERPAYMENTS FROM THE FOREIGN SERVICE RETIREMENT AND... PENSION SYSTEM (FSPS) § 17.4 Equity and good conscience. (a) Defined. Recovery is against equity and...

  1. 22 CFR 17.4 - Equity and good conscience.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 22 Foreign Relations 1 2012-04-01 2012-04-01 false Equity and good conscience. 17.4 Section 17.4 Foreign Relations DEPARTMENT OF STATE PERSONNEL OVERPAYMENTS FROM THE FOREIGN SERVICE RETIREMENT AND... PENSION SYSTEM (FSPS) § 17.4 Equity and good conscience. (a) Defined. Recovery is against equity and...

  2. 22 CFR 17.4 - Equity and good conscience.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 22 Foreign Relations 1 2013-04-01 2013-04-01 false Equity and good conscience. 17.4 Section 17.4 Foreign Relations DEPARTMENT OF STATE PERSONNEL OVERPAYMENTS FROM THE FOREIGN SERVICE RETIREMENT AND... PENSION SYSTEM (FSPS) § 17.4 Equity and good conscience. (a) Defined. Recovery is against equity and...

  3. 22 CFR 17.4 - Equity and good conscience.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 22 Foreign Relations 1 2010-04-01 2010-04-01 false Equity and good conscience. 17.4 Section 17.4 Foreign Relations DEPARTMENT OF STATE PERSONNEL OVERPAYMENTS FROM THE FOREIGN SERVICE RETIREMENT AND... PENSION SYSTEM (FSPS) § 17.4 Equity and good conscience. (a) Defined. Recovery is against equity and...

  4. 40 CFR 17.4 - Applicability to EPA proceedings.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 1 2013-07-01 2013-07-01 false Applicability to EPA proceedings. 17.4 Section 17.4 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY GENERAL IMPLEMENTATION OF THE EQUAL ACCESS TO JUSTICE ACT IN EPA ADMINISTRATIVE PROCEEDINGS General Provisions § 17.4 Applicability to...

  5. 40 CFR 17.4 - Applicability to EPA proceedings.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 1 2012-07-01 2012-07-01 false Applicability to EPA proceedings. 17.4 Section 17.4 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY GENERAL IMPLEMENTATION OF THE EQUAL ACCESS TO JUSTICE ACT IN EPA ADMINISTRATIVE PROCEEDINGS General Provisions § 17.4 Applicability to...

  6. 40 CFR 17.4 - Applicability to EPA proceedings.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 1 2011-07-01 2011-07-01 false Applicability to EPA proceedings. 17.4 Section 17.4 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY GENERAL IMPLEMENTATION OF THE EQUAL ACCESS TO JUSTICE ACT IN EPA ADMINISTRATIVE PROCEEDINGS General Provisions § 17.4 Applicability to...

  7. 40 CFR 17.4 - Applicability to EPA proceedings.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 1 2010-07-01 2010-07-01 false Applicability to EPA proceedings. 17.4 Section 17.4 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY GENERAL IMPLEMENTATION OF THE EQUAL ACCESS TO JUSTICE ACT IN EPA ADMINISTRATIVE PROCEEDINGS General Provisions § 17.4 Applicability to...

  8. 40 CFR 17.4 - Applicability to EPA proceedings.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 1 2014-07-01 2014-07-01 false Applicability to EPA proceedings. 17.4 Section 17.4 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY GENERAL IMPLEMENTATION OF THE EQUAL ACCESS TO JUSTICE ACT IN EPA ADMINISTRATIVE PROCEEDINGS General Provisions § 17.4 Applicability to...

  9. 47 CFR 17.4 - Antenna structure registration.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... Bureau shall resolve all environmental issues, in accordance with the environmental regulations (47 CFR 1... 47 Telecommunication 1 2013-10-01 2013-10-01 false Antenna structure registration. 17.4 Section 17... ANTENNA STRUCTURES General Information § 17.4 Antenna structure registration. (a) Effective July 1,...

  10. 47 CFR 17.4 - Antenna structure registration.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... Bureau shall resolve all environmental issues, in accordance with the environmental regulations (47 CFR 1... 47 Telecommunication 1 2012-10-01 2012-10-01 false Antenna structure registration. 17.4 Section 17... ANTENNA STRUCTURES General Information § 17.4 Antenna structure registration. (a) Effective July 1,...

  11. 47 CFR 17.4 - Antenna structure registration.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 1 2010-10-01 2010-10-01 false Antenna structure registration. 17.4 Section 17... ANTENNA STRUCTURES General Information § 17.4 Antenna structure registration. (a) Effective July 1, 1996, the owner of any proposed or existing antenna structure that requires notice of proposed...

  12. 47 CFR 17.4 - Antenna structure registration.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... issues, in accordance with the environmental regulations (47 CFR 1.1301 through 1.1319) specified in part... 47 Telecommunication 1 2014-10-01 2014-10-01 false Antenna structure registration. 17.4 Section 17... ANTENNA STRUCTURES General Information § 17.4 Antenna structure registration. Link to an...

  13. 47 CFR 17.4 - Antenna structure registration.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 1 2011-10-01 2011-10-01 false Antenna structure registration. 17.4 Section 17... ANTENNA STRUCTURES General Information § 17.4 Antenna structure registration. (a) Effective July 1, 1996, the owner of any proposed or existing antenna structure that requires notice of proposed...

  14. Microstructure of Precipitation Hardenable Powder Metallurgical Ni Alloys Containing 35 to 45 pct Cr and 3.5 to 6 pct Nb

    NASA Astrophysics Data System (ADS)

    Bihlet, Uffe D.; Dahl, Kristian V.; Somers, Marcel A. J.

    2014-10-01

    Ni-based alloys with high Cr contents are not only known for their excellent high temperature and hot corrosion resistance, but are also known for poor mechanical properties and difficult workability. Powder metallurgical (PM) manufacturing of alloys may overcome several of the shortcomings encountered in materials manufacturing involving solidification. In the present work, six PM Ni-based alloys containing 35 to 45 wt pct Cr and 3.5 to 6 wt pct Nb were produced and compacted via hot isostatic pressing. Samples were heat treated for up to 1656 hours at either 923 K or 973 K (650 °C or 700 °C), and the microstructures and mechanical properties were quantified and compared to thermodynamic calculations. For the majority of the investigated alloys, the high Cr and Nb contents caused development of primary populations of globular α-Cr and δ (Ni3Nb). Transmission electron microscopy of selected alloys confirmed the additional presence of metastable γ″ (Ni3Nb). A co-dependent growth morphology was found, where the preferred growth direction of γ″, the {001} planes of γ-Ni, caused precipitates of both α-Cr and δ to appear in the form of mutually perpendicular oriented disks or plates. Solution heat treatment at 1373 K (1100 °C) followed by aging at 973 K (700 °C) produced a significant strength increase for all alloys, and an aged yield strength of 990 MPa combined with an elongation of 21 pct is documented for Ni 40 wt pct Cr 3.5 wt pct Nb.

  15. [Hardening of dental instruments].

    PubMed

    Gerasev, G P

    1981-01-01

    The possibility of prolonging the service life of stomatological instruments by the local hardening of their working parts is discussed. Such hardening should be achieved by using hard and wear-resistant materials. The examples of hardening dental elevators and hard-alloy dental drills are given. New trends in the local hardening of instruments are the treatment of their working parts with laser beams, the application of coating on their surface by the gas-detonation method. The results of research work and trials are presented. PMID:7300627

  16. Be-Cu precipitation hardening experiment

    NASA Technical Reports Server (NTRS)

    Cowan, Richard L.

    1992-01-01

    The following is a laboratory experiment designed to further a student's understanding of materials science. The student performing this experiment should have a knowledge of binary phase diagrams. The objectives of this experiment are as follows: (1) to give the student a hands-on approach to changing materials properties through heat treatment of a specimen; (2) to quantify the amount of strengthening obtained in the specimen; and (3) to encourage the student to speculate about the structural changes that have occurred in the material to cause the changes in strength.

  17. Precipitation Hardenable High Temperature Shape Memory Alloy

    NASA Technical Reports Server (NTRS)

    Noebe, Ronald Dean (Inventor); Draper, Susan L. (Inventor); Nathal, Michael V. (Inventor); Crombie, Edwin A. (Inventor)

    2010-01-01

    A composition of the invention is a high temperature shape memory alloy having high work output, and is made from (Ni+Pt+Y),Ti(100-x) wherein x is present in a total amount of 49-55 atomic % Pt is present in a total amount of 10-30 atomic %, Y is one or more of Au, Pd. and Cu and is present in a total amount of 0 to 10 atomic %. The alloy has a matrix phase wherein the total concentration of Ni, Pt, and the one or more of Pd. Au, and Cu is greater than 50 atomic %.

  18. Laser hardening techniques on steam turbine blade and application

    NASA Astrophysics Data System (ADS)

    Yao, Jianhua; Zhang, Qunli; Kong, Fanzhi; Ding, Qingming

    Different laser surface hardening techniques, such as laser alloying and laser solution strengthening were adopted to perform modification treatment on the local region of inset edge for 2Cr13 and 17-4PH steam turbine blades to prolong the life of the blades. The microstructures, microhardness and anti-cavitation properties were investigated on the blades after laser treatment. The hardening mechanism and technique adaptability were researched. Large scale installation practices confirmed that the laser surface modification techniques are safe and reliable, which can improve the properties of blades greatly with advantages of high automation, high quality, little distortion and simple procedure.

  19. Influence of slip system hardening assumptions on modeling stress dependence of work hardening

    NASA Astrophysics Data System (ADS)

    Miller, Matthew; Dawson, Paul

    1997-11-01

    Due to the discrete directional nature of processes such as crystallographic slip, the orientation of slip planes relative to a fixed set of loading axes has a direct effect on the magnitude of the external load necessary to induce dislocation motion (yielding). The effect such geometric or textural hardening has on the macroscopic flow stress can be quantified in a polycrystal by the average Taylor factor M¯. Sources of resistance to dislocation motion such as interaction with dislocation structures, precipitates, and grain boundaries, contribute to the elevation of the critically resolved shear strength τcrss. In continuum slip polycrystal formulations, material hardening phenomena are reflected in the slip system hardness equations. Depending on the model, the hardening equations and the mean field assumption can both affect geometric hardening through texture evolution. In this paper, we examine continuum slip models and focus on how the slip system hardening model and the mean field assumption affect the stress-strain response. Texture results are also presented within the context of how the texture affects geometric hardening. We explore the effect of employing slip system hardnesses averaged over different size scales. We first compare a polycrystal simulation employing a single hardness per crystal to one using a latent hardening formulation producing distinct slip system hardnesses. We find little difference between the amplitude of the single hardness and a crystal-average of the latent hardening values. The geometric hardening is different due to the differences in the textures predicted by each model. We also find that due to the high degree of symmetry in an fcc crystal, macroscopic stress-strain predictions using simulations employing crystal- and aggregateaveraged hardnesses are nearly identical. We find this to be true for several different mean field assumptions. An aggregate-averaged hardness may be preferred in light of the difficulty

  20. Hardening of the arteries

    MedlinePlus

    Atherosclerosis; Arteriosclerosis; Plaque buildup - arteries; Hyperlipidemia - atherosclerosis; Cholesterol - atherosclerosis ... Hardening of the arteries often occurs with aging. As you grow older, ... narrows your arteries and makes them stiffer. These changes ...

  1. Microstructural evolution in a 17-4 PH stainless steel after aging at 400 C

    SciTech Connect

    Murayama, M.; Hono, K.; Katayama, Y.

    1999-02-01

    The microstructure of 17-4 PH stainless steel at various stages of heat treatment, i.e., after solution heat treatment, tempering at 580 C, and long-term aging at 400 C, have been studied by atom probe field ion microscopy (APFIM) and transmission electron microscopy (TEM). The solution-treated specimen consists largely of martensite with a small fraction of {delta}-ferrite. No precipitates are present in the martensite phase, while spherical fcc-Cu particles are present in the {delta}-ferrite. No precipitates are present in the martensite phase, while spherical fcc-Cu particles are present in the {delta}-ferrite. After tempering for 4 hours as 580 C, coherent Cu particles precipitate in the martensite phase. At this stage, the Cr concentration in the martensite phase is still uniform. After 5000 hours aging at 400 C, the martensite spinodaly decomposes into Fe-rich {alpha} and Cr-enriched {alpha}{prime}. In addition, fine particles of the G-phase (structure type D8{sub a}, space group Fm{bar 3}m) enriched in Si, Ni, and Mn have been found in intimate contact with the Cu precipitates. Following spinodal decomposition of the martensite phase, G-phase precipitation occurs after long-term aging.

  2. Deformation in metals after low temperature irradiation: Part II - Irradiation hardening, strain hardening, and stress ratios

    SciTech Connect

    Byun, Thak Sang; Li, Meimei

    2008-03-01

    Effects of irradiation at temperatures 200oC on tensile stress parameters are analyzed for dozens of bcc, fcc, and hcp pure metals and alloys, focusing on irradiation hardening, strain hardening, and relationships between the true stress parameters. Similar irradiation-hardening rates are observed for all the metals irrespective of crystal type; typically, the irradiation-hardening rates are large, in the range 100 - 1000 GPa/dpa, at the lowest dose of <0.0001 dpa and decrease with dose to a few tens of MPa/dpa or less at about 10 dpa. However, average irradiation-hardening rates over the dose range of 0 dpa − (the dose to plastic instability at yield) are considerably lower for stainless steels due to their high uniform ductility. It is shown that whereas low temperature irradiation increases the yield stress, it does not significantly change the strain-hardening rate of metallic materials; it decreases the fracture stress only when non-ductile failure occurs. Such dose independence in strain hardening behavior results in strong linear relationships between the true stress parameters. Average ratios of plastic instability stress to unirradiated yield stress are about 1.4, 3.9, and 1.3 for bcc metals (and precipitation hardened IN718 alloy), annealed fcc metals (and pure Zr), and Zr-4 alloy, respectively. Ratios of fracture stress to plastic instability stress are calculated to be 2.2, 1.7, and 2.1, respectively. Comparison of these values confirms that the annealed fcc metals and other soft metals have larger uniform ductility but smaller necking ductility when compared to other materials.

  3. 42. INTERIOR VIEW OF THE NAIL HARDENER USED TO HARDEN ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    42. INTERIOR VIEW OF THE NAIL HARDENER USED TO HARDEN AND TEMPER THE NAILS; WEST TUBES IN FOREGRPUND AND DRAWBACK TUBE IN THE CENTER - LaBelle Iron Works, Thirtieth & Wood Streets, Wheeling, Ohio County, WV

  4. Irradiation hardening of reduced activation martensitic steels

    NASA Astrophysics Data System (ADS)

    Kimura, A.; Morimura, T.; Narui, M.; Matsui, H.

    1996-10-01

    Irradiation response on the tensile properties of 9Cr2W steels has been investigated following FFTF/MOTA irradiations at temperatures between 646 and 873 K up to doses between 10 and 59 dpa. The largest irradiation hardening accompanied by the largest decrease in the elongation is observed for the specimens irradiated at 646 K at doses between 10 and 15 dpa. The irradiation hardening appears to saturate at a dose of around 10 dpa at the irradiation temperature. No hardening but softening was observed in the specimens irradiated at above 703 K to doses of 40 and 59 dpa. Microstructural observation by transmission electron microscope (TEM) revealed that the dislocation loops with the a<100> type Burgers vector and small precipitates which were identified to be M 6C type carbides existed after the irradiation at below 703 K. As for the void formation, the average size of voids increased with increasing irradiation temperature from 646 to 703 K. No voids were observed above 703 K. Irradiation softening was attributed to the enhanced recovery of martensitic structure under the irradiation. Post-irradiation annealing resulted in hardening by the annealing at 673 K and softening by the annealing at 873 K.

  5. RHOBOT: Radiation hardened robotics

    SciTech Connect

    Bennett, P.C.; Posey, L.D.

    1997-10-01

    A survey of robotic applications in radioactive environments has been conducted, and analysis of robotic system components and their response to the varying types and strengths of radiation has been completed. Two specific robotic systems for accident recovery and nuclear fuel movement have been analyzed in detail for radiation hardness. Finally, a general design approach for radiation-hardened robotics systems has been developed and is presented. This report completes this project which was funded under the Laboratory Directed Research and Development program.

  6. Nuclear effects hardened shelters

    NASA Astrophysics Data System (ADS)

    Lindke, Paul

    1990-11-01

    The Houston Fearless 76 Government Projects Group has been actively engaged for more than twenty-five years as a sub-contractor and currently as a prime contractor in the design, manufacture, repair and logistics support of custom mobile ground stations and their equipment accommodations. Other associated products include environmental control units (ECU's), mobilizers for shelters and a variety of mobile power generation units (MPU's). Since 1984, Houston Fearless 76 has designed and manufactured four 8' x 8' x 22' nuclear hardened mobile shelters. These shelters were designed to contain electronic data processing/reduction equipment. One shelter is currently being operated by the Air Force as a Defense Intelligence Agency (DIA) approved and certified Special Corrpartmented Information Facility (SCIF). During the development and manufacturing process of the shelters, we received continual technical assistance and design concept evaluations from Science Applications International Corporation (SAIC) Operations Analysis and Logistics Engineering Division and the Nondestructive Inspection Lab at McClellan AFB. SAIC was originally employed by the Air Force to design the nuclear hardening specifications applied to these shelters. The specific levels of hardening to which the shelters were designed are classified and will not be mentioned during this presentation.

  7. Microstructure and properties of 17-4PH steel plasma nitrocarburized with a carrier gas containing rare earth elements

    SciTech Connect

    Liu, R.L.; Yan, M.F.; Wu, Y.Q.; Zhao, C.Z.

    2010-01-15

    The effect of rare earth addition in the carrier gas on plasma nitrocarburizing of 17-4PH steel was studied. The microstructure and crystallographically of the phases in the surface layer as well as surface morphology of the nitrocarburized specimens were characterized by optical microscope, X-ray diffraction and scanning tunneling microscope, respectively. The hardness of the surface layer was measured by using a Vickers hardness test. The results show that the incorporation of rare earth elements in the carrier gas can increase the nitrocarburized layer thickness up to 55%, change the phase proportion in the nitrocarburized layer, refine the nitrides in surface layer, and increase the layer hardness above 100HV. The higher surface hardening effect after rare earth addition is caused by improvement in microstructure and change in the phase proportion of the nitrocarburized layer.

  8. Oxide dispersion hardened mechanically alloyed materials for high temperatures

    NASA Technical Reports Server (NTRS)

    Benjamin, J. S.; Strassburg, F. W.

    1982-01-01

    The procedure of mechanical alloying makes it possible to obtain, with the aid of powder-metallurgy techniques, alloys that consist of a metallic matrix in which very fine oxide particles are dispersed. Mechanically alloyed compound powders can be used for making either forged or hot-rolled semifinished products. For these products, dispersion strengthening and precipitation hardening has been combined. At high temperatures, the strength characteristics of the alloy are determined by both dispersion hardening and by precipitation hardening processes. The effect produced by each process is independent of that due to the other. Attention is given to the principle of mechanical alloying developed by Benjamin (1970, 1976), the strength characteristics of mechanically alloyed materials, the corrosion resistance of mechanically alloyed material at high temperatures, and the preparation and characteristics of the alloy MA 6000 E.

  9. Practical aspects of systems hardening

    SciTech Connect

    Shepherd, W.J.

    1989-01-01

    Applications of hardening technology in a practical system require a balance between the factors governing affordability, producibility, and survivability of the finished design. Without careful consideration of the top-level system operating constraints, a design engineer may find himself with a survivable but overweight, unproductive, expensive design. This paper explores some lessons learned in applying hardening techniques to several laser communications programs and is intended as an introductory guide to novice designers faced with the task of hardening a space system.

  10. Hardening mechanisms in a dynamic strain aging alloy, Hastelloy X, during isothermal and thermomechanical cyclic deformation

    NASA Technical Reports Server (NTRS)

    Miner, R. V.; Castelli, M. G.

    1992-01-01

    The relative contributions of the hardening mechanisms in Hastelloy X during cyclic deformation were investigated by conducting isothermal cyclic deformation tests within a total strain range of +/-0.3 pct and at several temperatures and strain rates, and thermomechanical tests within several different temperature limits. The results of the TEM examinations and special constant structure tests showed that the precipitation on dislocations of Cr23C6 contributed to hardening, but only after sufficient time above 500 C. Solute drag alone produced very considerable cyclic hardening. Heat dislocation densities, peaking around 10 exp 11 per sq cm, were found to develop at temperatures producing the greatest cyclic hardening.

  11. Multipurpose hardened spacecraft insulation

    NASA Technical Reports Server (NTRS)

    Steimer, Carlos H.

    1990-01-01

    A Multipurpose Hardened Spacecraft Multilayer Insulation (MLI) system was developed and implemented to meet diverse survivability and performance requirements. Within the definition and confines of a MLI assembly (blanket), the design: (1) provides environmental protection from natural and induced nuclear, thermal, and electromagnetic radiation; (2) provides adequate electrostatic discharge protection for a geosynchronous satellite; (3) provides adequate shielding to meet radiated emission needs; and (4) will survive ascent differential pressure loads between enclosed volume and space. The MLI design is described which meets these requirements and design evolution and verification is discussed. The application is for MLI blankets which closeout the area between the laser crosslink subsystem (LCS) equipment and the DSP spacecraft cabin. Ancillary needs were implemented to ease installation at launch facility and to survive ascent acoustic and vibration loads. Directional venting accommodations were also incorporated to avoid contamination of LCS telescope, spacecraft sensors, and second surface mirrors (SSMs).

  12. Effects of Ce additions on the age hardening response of Mg–Zn alloys

    SciTech Connect

    Langelier, Brian Esmaeili, Shahrzad

    2015-03-15

    The effects of Ce additions on the precipitation hardening behaviour of Mg–Zn are examined for a series of alloys, with Ce additions at both alloying and microalloying levels. The alloys are artificially aged, and studied using hardness measurement and X-ray diffraction, as well as optical and transmission electron microscopy. It is found that the age-hardening effect is driven by the formation of fine precipitates, the number density of which is related to the Zn content of the alloy. Conversely, the Ce content is found to slightly reduce hardening. When the alloy content of Ce is high, large secondary phase particles containing both Ce and Zn are present, and remain stable during solutionizing. These particles effectively reduce the amount of Zn available as solute for precipitation, and thereby reduce hardening. Combining hardness results with thermodynamic analysis of alloy solute levels also suggests that Ce can have a negative effect on hardening when present as solutes at the onset of ageing. This effect is confirmed by designing a pre-ageing heat treatment to preferentially remove Ce solutes, which is found to restore the hardening capability of an Mg–Zn–Ce alloy to the level of the Ce-free alloy. - Highlights: • The effects of Ce additions on precipitation in Mg–Zn alloys are examined. • Additions of Ce to Mg–Zn slightly reduce the age-hardening response. • Ce-rich secondary phase particles deplete the matrix of Zn solute. • Hardening is also decreased when Ce is present in solution. • Pre-ageing to preferentially precipitate out Ce restores hardening capabilities.

  13. System-Level Radiation Hardening

    NASA Technical Reports Server (NTRS)

    Ladbury, Ray

    2014-01-01

    Although system-level radiation hardening can enable the use of high-performance components and enhance the capabilities of a spacecraft, hardening techniques can be costly and can compromise the very performance designers sought from the high-performance components. Moreover, such techniques often result in a complicated design, especially if several complex commercial microcircuits are used, each posing its own hardening challenges. The latter risk is particularly acute for Commercial-Off-The-Shelf components since high-performance parts (e.g. double-data-rate synchronous dynamic random access memories - DDR SDRAMs) may require other high-performance commercial parts (e.g. processors) to support their operation. For these reasons, it is essential that system-level radiation hardening be a coordinated effort, from setting requirements through testing up to and including validation.

  14. Explosive Surface Hardening of Austenitic Stainless Steel

    NASA Astrophysics Data System (ADS)

    Kovacs-Coskun, T.

    2016-04-01

    In this study, the effects of explosion hardening on the microstructure and the hardness of austenitic stainless steel have been studied. The optimum explosion hardening technology of austenitic stainless steel was researched. In case of the explosive hardening used new idea mean indirect hardening setup. Austenitic stainless steels have high plasticity and can be easily cold formed. However, during cold processing the hardening phenomena always occurs. Upon the explosion impact, the deformation mechanism indicates a plastic deformation and this deformation induces a phase transformation (martensite). The explosion hardening enhances the mechanical properties of the material, includes the wear resistance and hardness. In case of indirect hardening as function of the setup parameters specifically the flayer plate position the hardening increased differently. It was find a relationship between the explosion hardening setup and the hardening level.

  15. 24 CFR 17.4 - Administrative claim; evidence and information to be submitted.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 24 Housing and Urban Development 1 2010-04-01 2010-04-01 false Administrative claim; evidence and information to be submitted. 17.4 Section 17.4 Housing and Urban Development Office of the Secretary, Department of Housing and Urban Development ADMINISTRATIVE CLAIMS Claims Against Government Under...

  16. 24 CFR 17.4 - Administrative claim; evidence and information to be submitted.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 24 Housing and Urban Development 1 2014-04-01 2014-04-01 false Administrative claim; evidence and information to be submitted. 17.4 Section 17.4 Housing and Urban Development Office of the Secretary, Department of Housing and Urban Development ADMINISTRATIVE CLAIMS Claims Against Government Under Federal Tort Claims Act Procedures §...

  17. Forming an age hardenable aluminum alloy with intermediate annealing

    NASA Astrophysics Data System (ADS)

    Wang, Kaifeng; Carsley, John E.; Stoughton, Thomas B.; Li, Jingjing; Zhang, Lianhong; He, Baiyan

    2013-12-01

    A method to improve formability of aluminum sheet alloys by a two-stage stamping process with intermediate annealing was developed for a non-age hardenable Al-Mg alloy where the annealing heat treatment provided recovery of cold work from the initial stamping and recrystallization of the microstructure to enhance the forming limits of the material. This method was extended to an age hardenable, Al-Mg-Si alloy, which is complicated by the competing metallurgical effects during heat treatment including recovery (softening effect) vs. precipitation (hardening effect). An annealing heat treatment process condition was discovered wherein the stored strain energy from an initial plastic deformation can be sufficiently recovered to enhance formability in a second deformation; however, there is a deleterious effect on subsequent precipitation hardening. The improvement in formability was quantified with uniaxial tensile tests as well as with the forming limit diagram. Since strain-based forming limit curves (FLC) are sensitive to pre-strain history, both stress-based FLCs and polar-effective-plastic-strain (PEPS) FLCs, which are path-independent, were used to evaluate the forming limits after preform annealing. A technique was developed to calculate the stress-based FLC in which a residual-effective-plastic-strain (REPS) was determined by overlapping the hardening curve of the pre-strained and annealed material with that of the simply-annealed- material. After converting the strain-based FLCs using the constant REPS method, it was found that the stress-based FLCs and the PEPS FLCs of the post-annealed materials were quite similar and both tools are applicable for evaluating the forming limits of Al-Mg-Si alloys for a two-step stamping process with intermediate annealing.

  18. On the correlation between irradiation-induced microstructural features and the hardening of reactor pressure vessel steels

    NASA Astrophysics Data System (ADS)

    Lambrecht, M.; Meslin, E.; Malerba, L.; Hernández-Mayoral, M.; Bergner, F.; Pareige, P.; Radiguet, B.; Almazouzi, A.

    2010-11-01

    A correlation is attempted between microstructural observations by various complementary techniques, which have been implemented within the PERFECT project and the hardening measured by tensile tests of reactor pressure vessel steel and model alloys after irradiation to a dose of ˜7 × 10 19 n cm -2. This is done, using the simple hardening model embodied by the Orowan equation and applying the most suitable superposition law, as suggested by a parametric study using the DUPAIR line tension code. It is found that loops are very strong obstacles to dislocation motion, but due to their low concentration, they only play a minor role in the hardening itself. For the precipitates, the contrary is found, although they are quite soft (due to their very small sizes and their coherent nature), they still play the dominant role in the hardening. Vacancy clusters are important for the formation of both loops and precipitates, but they will play almost no role in the hardening by themselves.

  19. 17. 4th floor roof, view south, 4th and 5th floor ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    17. 4th floor roof, view south, 4th and 5th floor setback to left and atrium structure to right - Sheffield Farms Milk Plant, 1075 Webster Avenue (southwest corner of 166th Street), Bronx, Bronx County, NY

  20. Life on the Hardened Border

    ERIC Educational Resources Information Center

    Miller, Bruce Granville

    2012-01-01

    The many Coast Salish groups distributed on both sides of the United States-Canada border on the Pacific coast today face significant obstacles to cross the international border, and in some cases are denied passage or intimidated into not attempting to cross. The current situation regarding travel by Aboriginal people reflects the "hardening" of…

  1. Onycholysis induced by nail hardener.

    PubMed

    Helsing, Per; Austad, Joar; Talberg, Hans Jørgen

    2007-10-01

    Nail hardeners appeared in the market during the 1960s. They were basically solutions of formaldehyde. The first adverse effects were published in 1966 (1). Reactions were onycholysis, chromonychia, subungual haemorrhage, and hyperkeratosis. Onycholysis may be non-inflammatory or inflammatory, and is accompanied by throbbing pain. Inflammatory reactions are followed by paronychia and occasional dermatitis on the digital pulpa. PMID:17868227

  2. Age Hardening Kinetics in 7xxx Type (Al-Mg-Zn) Alloys

    SciTech Connect

    Vevecka-Priftaj, A.; Lamani, E.; Fjerdingen, J.; Langsrud, Y.; Gjoennes, J.; Hansen, V.

    2007-04-23

    Age hardening in industrial 7xxx alloys at the temperature 100 deg. and 150 deg. C up to 144 hrs, after solid solution treatments at 450 deg. and 550 deg. C, has been followed by measurements of Vickers hardness, scanning and transmission electron microscopy. The influence of silicon on phase and kinetic of age hardening zones and precipitates has been studied. High iron and silicon content increase the number of primary particle in the alloy. Size distribution of {eta}'-precipitates has been determined.

  3. Model Fitting for Predicted Precipitation in Darwin: Some Issues with Model Choice

    ERIC Educational Resources Information Center

    Farmer, Jim

    2010-01-01

    In Volume 23(2) of the "Australian Senior Mathematics Journal," Boncek and Harden present an exercise in fitting a Markov chain model to rainfall data for Darwin Airport (Boncek & Harden, 2009). Days are subdivided into those with precipitation and precipitation-free days. The author abbreviates these labels to wet days and dry days. It is…

  4. Scintillation-Hardened GPS Receiver

    NASA Technical Reports Server (NTRS)

    Stephens, Donald R.

    2015-01-01

    CommLargo, Inc., has developed a scintillation-hardened Global Positioning System (GPS) receiver that improves reliability for low-orbit missions and complies with NASA's Space Telecommunications Radio System (STRS) architecture standards. A software-defined radio (SDR) implementation allows a single hardware element to function as either a conventional radio or as a GPS receiver, providing backup and redundancy for platforms such as the International Space Station (ISS) and high-value remote sensing platforms. The innovation's flexible SDR implementation reduces cost, weight, and power requirements. Scintillation hardening improves mission reliability and variability. In Phase I, CommLargo refactored an open-source GPS software package with Kalman filter-based tracking loops to improve performance during scintillation and also demonstrated improved navigation during a geomagnetic storm. In Phase II, the company generated a new field-programmable gate array (FPGA)-based GPS waveform to demonstrate on NASA's Space Communication and Navigation (SCaN) test bed.

  5. Surface Fatigue Resistance with Induction Hardening

    NASA Technical Reports Server (NTRS)

    Townsend, Dennis; Turza, Alan; Chapman, Mike

    1996-01-01

    Induction hardening has been used for some years to harden the surface and improve the strength and service life of gears and other components. Many applications that employ induction hardening require a relatively long time to finish the hardening process and controlling the hardness of the surface layer and its depth often was a problem. Other surface hardening methods, ie., carbonizing, take a very long time and tend to cause deformations of the toothing, whose elimination requires supplementary finishing work. In double-frequency induction hardening, one uses a low frequency for the preheating of the toothed wheel and a much higher frequency for the purpose of rapidly heating the surface by way of surface hardening.

  6. Hybrid Laser-arc Welding of 17-4 PH Martensitic Stainless Steel

    NASA Astrophysics Data System (ADS)

    Liu, Wei; Ma, Junjie; Atabaki, Mehdi Mazar; Pillai, Raju; Kumar, Biju; Vasudevan, Unnikrishnan; Sreshta, Harold; Kovacevic, Radovan

    2015-06-01

    17-4 PH stainless steel has wide applications in severe working conditions due to its combination of good corrosion resistance and high strength. The weldability of 17-4 PH stainless steel is challenging. In this work, hybrid laser-arc welding was developed to weld 17-4 PH stainless steel. This method was chosen based on its advantages, such as deep weld penetration, less filler materials, and high welding speed. The 17-4 PH stainless steel plates with a thickness of 19 mm were successfully welded in a single pass. During the hybrid welding, the 17-4 PH stainless steel was immensely susceptible to porosity and solidification cracking. The porosity was avoided by using nitrogen as the shielding gas. The nitrogen stabilized the keyhole and inhibited the formation of bubbles during welding. Solidification cracking easily occurred along the weld centerline at the root of the hybrid laser-arc welds. The microstructural evolution and the cracking susceptibility of 17-4 PH stainless steel were investigated to remove these centerline cracks. The results showed that the solidification mode of the material changed due to high cooling rate at the root of the weld. The rapid cooling rate caused the transformation from ferrite to austenite during the solidification stage. The solidification cracking was likely formed as a result of this cracking-susceptible microstructure and a high depth/width ratio that led to a high tensile stress concentration. Furthermore, the solidification cracking was prevented by preheating the base metal. It was found that the preheating slowed the cooling rate at the root of the weld, and the ferrite-to-austenite transformation during the solidification stage was suppressed. Delta ferrite formation was observed in the weld bead as well no solidification cracking occurred by optimizing the preheating temperature.

  7. Quantification of age hardening in maraging steels and an Ni-base superalloy

    SciTech Connect

    Sha, W.

    2000-02-01

    Age hardening process in metallic alloys due to precipitation can be quantified using phase transformation theories. Two ageing stages are of particular interest, for both theory and practice. The early stage of precipitation hardening is under the description of the Johnson-Mehl-Avrami equation. Wilson has recently provided a detailed theoretical analysis for early stages of ageing. Wilson successfully used equations in the quantification of early and over-ageing stages of hardening in an Fe-12Ni-6Mn maraging-type alloy. In the present work, these were applied to further alloys. All the hardness data were taken from published literature. Original references should be consulted for details of materials, testing and characterization.

  8. Isothermal age-hardening behaviour in a Au-1.6 wt% Ti alloy.

    PubMed

    Kim, H I; Seol, H J; Bae, D H; Shim, J Y; Takada, Y; Okuno, O

    1999-03-01

    This study describes research with a view to developing a new age-hardenable, high-carat dental gold alloy with better biocompatibility by addition of a small quantity of titanium to gold. The relationship between isothermal age-hardening and phase transformation of the Au-1.6 wt% Ti alloy was investigated by means of hardness testing, X-ray diffraction study, scanning electron microscopic observation and energy dispersive spectroscopy. The hardening in the initial stage of ageing seemed to be attributable to the continuous precipitation of the Au4Ti ordered phase in the supersaturated alpha solid solution matrix. The overaging with softening was attributed mainly to the formation of precipitates at the grain boundaries, which grew to bright lamellae and seemed to be composed of the Au4Ti phase. PMID:10786146

  9. Characteristics of laser beam welds of age-hardenable 6061-T6 aluminum alloy

    NASA Astrophysics Data System (ADS)

    Hirose, Akio; Kobayashi, Kojiro F.

    2003-03-01

    Laser beam welding is attractive for joining age-hardenable aluminum alloys, because its low over-all heat input results in a narrow weld heat affected zone (HAZ), where softening caused by dissolution of age precipitates occurs. In the present work, 1mm-thick 6061-T6 aluminum alloy plates were welded using a 2.5 kW CO2 laser and it was experimentally proved that the width of the softened region in the laser beam weld was less than 1/7 that of a TIG weld. Moreover the hardness in the softened region of the laser beam weld was found to be almost fully recovered to the base metal hardness by applying a post-weld aging treatment at 443 K for 28.8 ks without solution annealing unlike the TIG weld. These results characterize the advantage of laser beam welding in joining of the age-hardenable aluminum alloy as compared with the conventional arc welding. The hardness distributions in the HAZ were theoretically evaluated based on kinetic equations describing the dissolution of hardening β' (Mg2Si) precipitates and the precipitation of non-hardening β' (Mg2Si) precipitates during the weld thermal cycles to quantitatively prove above mentioned advantageous characteristics of laser beam welding.

  10. 45 CFR 17.4 - Regulatory investigations and trial-type proceedings.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... RELEASE OF ADVERSE INFORMATION TO NEWS MEDIA § 17.4 Regulatory investigations and trial-type proceedings... economic harm may occur unless the public is notified immediately, it may release information to news media... operating component shall rely on the news media to the extent necessary to provide such notice even...

  11. 45 CFR 17.4 - Regulatory investigations and trial-type proceedings.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... RELEASE OF ADVERSE INFORMATION TO NEWS MEDIA § 17.4 Regulatory investigations and trial-type proceedings... economic harm may occur unless the public is notified immediately, it may release information to news media... operating component shall rely on the news media to the extent necessary to provide such notice even...

  12. 45 CFR 17.4 - Regulatory investigations and trial-type proceedings.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... RELEASE OF ADVERSE INFORMATION TO NEWS MEDIA § 17.4 Regulatory investigations and trial-type proceedings... economic harm may occur unless the public is notified immediately, it may release information to news media... operating component shall rely on the news media to the extent necessary to provide such notice even...

  13. 17. (4"X5" image enlarged from 2 1/4" negative) Sam Fowler, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    17. (4"X5" image enlarged from 2 1/4" negative) Sam Fowler, Photographer, February 1998 VIEW OF GEORGIA DOT BRIDGE NO. 051-00025D-01986N (JAMES P. HOULIHAN BRIDGE) APPROACH SPAN FENDER - Georgia DOT Bridge No. 051-00025D-01986N, US 17 & State Route 25 Spanning Savannah River, Port Wentworth, Chatham County, GA

  14. 7 CFR 17.4 - Agents of the participant or importer.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ....4 Agriculture Office of the Secretary of Agriculture SALES OF AGRICULTURAL COMMODITIES MADE AVAILABLE UNDER TITLE I OF THE AGRICULTURAL TRADE DEVELOPMENT AND ASSISTANCE ACT OF 1954, AS AMENDED § 17.4..., or other representative (hereafter “agent”) in connection with arranging the purchase of...

  15. 7 CFR 17.4 - Agents of the participant or importer.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ....4 Agriculture Office of the Secretary of Agriculture SALES OF AGRICULTURAL COMMODITIES MADE AVAILABLE UNDER TITLE I OF THE AGRICULTURAL TRADE DEVELOPMENT AND ASSISTANCE ACT OF 1954, AS AMENDED § 17.4..., or other representative (hereafter “agent”) in connection with arranging the purchase of...

  16. 45 CFR 17.4 - Regulatory investigations and trial-type proceedings.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... RELEASE OF ADVERSE INFORMATION TO NEWS MEDIA § 17.4 Regulatory investigations and trial-type proceedings... economic harm may occur unless the public is notified immediately, it may release information to news media... operating component shall rely on the news media to the extent necessary to provide such notice even...

  17. 45 CFR 17.4 - Regulatory investigations and trial-type proceedings.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... RELEASE OF ADVERSE INFORMATION TO NEWS MEDIA § 17.4 Regulatory investigations and trial-type proceedings... economic harm may occur unless the public is notified immediately, it may release information to news media... operating component shall rely on the news media to the extent necessary to provide such notice even...

  18. DISPERSION HARDENING OF URANIUM METAL

    DOEpatents

    Arbiter, W.

    1963-01-15

    A method of hardening U metal involves the forming of a fine dispersion of UO/sub 2/. This method consists of first hydriding the U to form a finely divided powder and then exposing the powder to a very dilute O gas in an inert atmosphere under such pressure and temperature conditions as to cause a thin oxide film to coat each particle of the U hydride, The oxide skin prevents agglomeration of the particles as the remaining H is removed, thus preserving the small particle size. The oxide skin coatings remain as an oxide dispersion. The resulting product may be workhardened to improve its physical characteristics. (AEC)

  19. High-throughput study of crystal structures and stability of strengthening precipitates in Mg alloys

    NASA Astrophysics Data System (ADS)

    Wang, Dongshu; Amsler, Maxmilian; Hegde, Vinay; Saal, James; Issa, Ahmed; Zeng, Xiaoqin; Wolverton, Christopher

    Age hardening, in which precipitates form and impede the movement of dislocations, can be applied to magnesium alloys in order to increase their limited strengthening behavior. To help clarify the energetics of precipitation hardening of Mg alloys, we employed first principles density functional theory calculations to elucidate both crystal structures and energetics of a very large set of precipitates in Mg alloys. We find the enthalpy changes of (stable and metastable) observed precipitates during the age hardening process are consistent with the experimental sequence of formation for many Mg binary alloys (Mg- {Nd, Gd, Y, Sn, Al, Zn}). For cases where the metastable precipitate crystal structure is unavailable, we search over several prototypes and predict structures/stoichiometries for several ternary precipitates. In addition, high-throughput calculations are performed to construct hcp-based based convex hulls, which assist the identification of coherent GP zones and new metastable phases in age-hardened hcp systems.

  20. Energy-Efficient Thermomagnetic and Induction Hardening

    SciTech Connect

    2009-02-01

    This factsheet describes a research project that will develop and test a hybrid thermomagnetic and induction hardening technology to replace conventional heat treatment processes in forging applications.

  1. Radiation Hardened Electronics for Extreme Environments

    NASA Technical Reports Server (NTRS)

    Keys, Andrew S.; Watson, Michael D.

    2007-01-01

    The Radiation Hardened Electronics for Space Environments (RHESE) project consists of a series of tasks designed to develop and mature a broad spectrum of radiation hardened and low temperature electronics technologies. Three approaches are being taken to address radiation hardening: improved material hardness, design techniques to improve radiation tolerance, and software methods to improve radiation tolerance. Within these approaches various technology products are being addressed including Field Programmable Gate Arrays (FPGA), Field Programmable Analog Arrays (FPAA), MEMS Serial Processors, Reconfigurable Processors, and Parallel Processors. In addition to radiation hardening, low temperature extremes are addressed with a focus on material and design approaches.

  2. Obtaining strong zirconia ceramic by hardening and tempering

    SciTech Connect

    Pliner, S.Y.; Dabizha, A.A.; Komolikov, Y.I.; Rutman, D.S.; Toropov, Y.S.

    1985-07-01

    To determine whether it is possible to strengthen ceramics by means of hardening and tempering, the authors selected a solid solution pf 3.4% of Y/sub 2/O/sub 3/ (molar fraction) in ZrO/sub 2/. The solution was synthesized by combined precipitation of the compounds from an aqueous solution of chlorides. The filtered residue of hydroxides was dried and calcined at about 900/sup 0/C. The calcined material was milled for 80 h in an iron ball mill by the wet method with a ratio of materials: balls: water of 1:2:1. The material was then purified to remove tramp iron by treatment with HC1 with an addition of hydrogen peroxide, followed by decantation with distilled water. The specimens were heated to 2250-2300/sup 0/C in a furnace with a straight-through vertical channel of diameter 20 mm, a heating element made of stabilized zirconia, and high-temperature heat insulation made of porous ceramic-concrete based on ZrO/sub 2/. The hardening of the specimens at this temperature was done at a rate ensuring practically complete preservation of the cubic phase of ZrO/sub 2/. The tempering of the hardened specimens was done by the furnace with a silit heaters at 1400/sup 0/C over different times (0-85 h).

  3. COSMIC-RAY HELIUM HARDENING

    SciTech Connect

    Ohira, Yutaka; Ioka, Kunihito

    2011-03-01

    Recent observations by the CREAM and ATIC-2 experiments suggest that (1) the spectrum of cosmic-ray (CR) helium is harder than that of CR protons below the knee energy, 10{sup 15}eV, and (2) all CR spectra become hard at {approx}>10{sup 11}eV nucleon{sup -1}. We propose a new idea, that higher energy CRs are generated in a more helium-rich region, to explain the hardening without introducing different sources for CR helium. The helium-to-proton ratio at {approx}100 TeV exceeds the Big Bang abundance Y = 0.25 by several times, and the different spectrum is not reproduced within the diffusive shock acceleration theory. We argue that CRs are produced in a chemically enriched region, such as a superbubble, and the outward-decreasing abundance naturally leads to the hard spectrum of CR helium if CRs escape from the supernova remnant shock in an energy-dependent way. We provide a simple analytical spectrum that also fits well the hardening due to the decreasing Mach number in the hot superbubble with {approx}10{sup 6} K. Our model predicts hard and concave spectra for heavier CR elements.

  4. Adaptive Changes in ATPase Activity in the Cells of Winter Wheat Seedlings during Cold Hardening

    PubMed Central

    Jian, Ling-Cheng; Sun, Long-Hua; Dong, He-Zhu

    1982-01-01

    A cytochemical study of ATPase activity in the cells of cold hardened and nonhardened winter wheat (Triticum aestivum L. cv. Nongke No. 1) seedlings was carried out by electron microscopic observation of lead phosphate precipitation. ATPase activity associated with various cellular organelles was altered during cold hardening. (a) At 22°C, high plasmalemma ATPase activity was observed in both cold hardened and nonhardened tissues; at 5°C, high activity of plasmalemma ATPase was observed in hardened tissues, but not in unhardened tissues. (b) In nonhardened tissues, tonoplast and vacuoles did not exhibit high ATPase activity at either 22 or 5°C, while in hardened tissues high activity was observed at both temperatures. (c) At 5°C, ATPase activity of nucleoli and chromatin was decreased in hardened tissues, but not in nonhardened tissues. It is suggested that adaptive changes in ATPase activity associated with a particular cellular organelle or membrane may be associated with the development of frost resistance of winter wheat seedlings. Images Fig. 1 Fig. 2 Fig. 3 PMID:16662432

  5. A phenomenological model for bake hardening in minimal carbon steels

    NASA Astrophysics Data System (ADS)

    Das, Sourav; Nath Mohanty, Omkar; Brat Singh, Shiv

    2014-06-01

    The essence of bake hardening is to exploit the classical strain ageing in a positive way to increase the strength of the formed steel sheets used in outer body panel of a passenger car during the paint-baking operation. A new model that takes into account the strengthening contributions from Cottrell atmosphere and precipitate formation has been developed in the present work. The model predicts the increase in strength as a function of the amount of free solute C (calculated as a function of the annealing temperature), the amount of deformation, ageing temperature and time. The model predictions have been found to agree quite well with the experimental results; the individual contributions of Cottrell atmosphere and precipitation strengthening have been quantified.

  6. Improved hardening theory for cyclic plasticity.

    NASA Technical Reports Server (NTRS)

    Vos, R. G.; Armstrong, W. H.

    1973-01-01

    A temperature-dependent version of a combined hardening theory, including isotropic and kinematic hardening, is presented within the framework of recent plasticity formulations. This theory has been found to be especially useful in finite-element analysis of aerospace vehicle engines under conditions of large plastic strain and low-cycle fatigue.

  7. Kinematic hardening of a porous limestone

    NASA Astrophysics Data System (ADS)

    Cheatham, J. B.; Allen, M. B.; Celle, C. C.

    1984-10-01

    A concept for a kinematic hardening yield surface in stress space for Cordova Cream limestone (Austin Chalk) developed by Celle and Cheatham (1981) has been improved using Ziegler's modification of Prager's hardening rule (Ziegler, 1959). Data to date agree with the formulated concepts. It is shown how kinematic hardening can be used to approximate the yield surface for a wide range of stress states past the initial yield surface. The particular difficulty of identifying the yield surface under conditions of unloading or extension is noted. A yield condition and hardening rule which account for the strain induced anisotropy in Cordova Cream Limestone were developed. Although the actual yield surface appears to involve some change of size and shape, it is concluded that true kinematic hardening provides a basis for engineering calculations.

  8. Challenges in hardening technologies using shallow-trench isolation

    SciTech Connect

    Shaneyfelt, M.R.; Dodd, P.E.; Draper, B.L.; Flores, R.S.

    1998-02-01

    Challenges related to radiation hardening CMOS technologies with shallow-trench isolation are explored. Results show that trench hardening can be more difficult than simply replacing the trench isolation oxide with a hardened field oxide.

  9. Cyclic hardening mechanisms in Nimonic 80A

    NASA Technical Reports Server (NTRS)

    Lerch, B. A.; Gerold, V.

    1987-01-01

    A nickel base superalloy was fatigued under constant plastic strain range control. The hardening response was investigated as a function of plastic strain range and particle size of the gamma prime phase. Hardening was found to be a function of the slip band spacing. Numerous measurements of the slip band spacing and other statistical data on the slip band structures were obtained. Interactions between intersecting slip systems were shown to influence hardening. A Petch-Hall model was found to describe best this relationship between the response stress and the slip band spacing.

  10. Predicting Coherency Loss of γ^'' Precipitates in IN718 Superalloy

    NASA Astrophysics Data System (ADS)

    Ji, Yanzhou; Lou, Yucun; Qu, Meng; Rowatt, John David; Zhang, Fan; Simpson, Timothy W.; Chen, Long-Qing

    2016-04-01

    Precipitate hardening through coherent particles is an important strengthening mechanism in Ni-based IN718 superalloy. The change of coherency state, e.g., loss of coherency, can affect the precipitation kinetics and the efficacy of precipitate hardening. In this work, we predict the critical size of γ^'' -Ni3Nb precipitates in IN718 to trigger coherency loss using the phase-field approach with available materials parameters from first-principles calculations and from the literature. The predicted critical size lies within the range of experimentally reported values. The effect of coherency loss on precipitate morphology and kinetics, as well as the aging time to reach this critical size during heat treatment, is also predicted and discussed. These predictions provide guidance in controlling the size of γ^'' precipitates and optimizing the strength of IN718 alloys.

  11. Predicting Coherency Loss of γ^'' Precipitates in IN718 Superalloy

    NASA Astrophysics Data System (ADS)

    Ji, Yanzhou; Lou, Yucun; Qu, Meng; Rowatt, John David; Zhang, Fan; Simpson, Timothy W.; Chen, Long-Qing

    2016-06-01

    Precipitate hardening through coherent particles is an important strengthening mechanism in Ni-based IN718 superalloy. The change of coherency state, e.g., loss of coherency, can affect the precipitation kinetics and the efficacy of precipitate hardening. In this work, we predict the critical size of γ^'' -Ni3Nb precipitates in IN718 to trigger coherency loss using the phase-field approach with available materials parameters from first-principles calculations and from the literature. The predicted critical size lies within the range of experimentally reported values. The effect of coherency loss on precipitate morphology and kinetics, as well as the aging time to reach this critical size during heat treatment, is also predicted and discussed. These predictions provide guidance in controlling the size of γ^'' precipitates and optimizing the strength of IN718 alloys.

  12. Fatigue hardening in niobium single crystals.

    NASA Technical Reports Server (NTRS)

    Doner, M.; Diprimio, J. C.; Salkovitz, E. I.

    1973-01-01

    Nb single crystals of various orientations were cyclically deformed in tension-compression under strain control. At low strain amplitudes all crystals oriented for single slip and some oriented for multiple slip showed a two stage hardening. When present, the first stage was characterized with almost no cyclic work hardening. The rate of hardening in the second stage increased with strain amplitude and the amount of secondary slip. In crystals oriented for single slip kink bands developed on their side faces during rapid hardening stage which resulted in considerable amount of asterism in Laue spots. A cyclic stress-strain curve independent of prior history was found to exist which was also independent of crystal orientation. Furthermore, this curve differed only slightly from that of polycrystalline Nb obtained from data in literature.

  13. Alloy solution hardening with solute pairs

    DOEpatents

    Mitchell, John W.

    1976-08-24

    Solution hardened alloys are formed by using at least two solutes which form associated solute pairs in the solvent metal lattice. Copper containing equal atomic percentages of aluminum and palladium is an example.

  14. Process for hardening the surface of polymers

    DOEpatents

    Mansur, L.K.; Lee, E.H.

    1992-07-14

    Hard surfaced polymers and the method for making them is generally described. Polymers are subjected to simultaneous multiple ion beam bombardment, that results in a hardening of the surface and improved wear resistance. 1 figure.

  15. Process for hardening the surface of polymers

    DOEpatents

    Mansur, Louis K.; Lee, Eal H.

    1992-01-01

    Hard surfaced polymers and the method for making them is generally described. Polymers are subjected to simultaneous multiple ion beam bombardment, that results in a hardening of the surface and improved wear resistance.

  16. Decline in Radiation Hardened Microcircuit Infrastructure

    NASA Technical Reports Server (NTRS)

    LaBel, Kenneth A.

    2015-01-01

    Two areas of radiation hardened microcircuit infrastructure will be discussed: 1) The availability and performance of radiation hardened microcircuits, and, and 2) The access to radiation test facilities primarily for proton single event effects (SEE) testing. Other areas not discussed, but are a concern include: The challenge for maintaining radiation effects tool access for assurance purposes, and, the access to radiation test facilities primarily for heavy ion single event effects (SEE) testing. Status and implications will be discussed for each area.

  17. Alloy Shrinkage factors for the investment casting of 17-4PH stainless steel parts

    SciTech Connect

    Sabau, Adrian S; Porter, Wallace D

    2008-01-01

    In this study, the alloy shrinkage factors were obtained for the investment casting of 17-4PH stainless steel parts. For the investment casting process, unfilled wax and fused silica with a zircon prime coat were used for patterns and shell molds, respectively. Dimensions of the die tooling, wax pattern, and casting were measured using a Coordinate Measurement Machine. For all the properties, the experimental data available in the literature did not cover the entire temperature range necessary for process simulation. A comparison between the predicted material property data measured property data is made. It was found that most material properties were accurately predicted over the most of the temperature range of the process. Several assumptions were made in order to obtain a complete set of mechanical property data at high temperatures. Thermal expansion measurements for the 17-4PH alloy were conducted at heating and cooling. As a function of temperature, the thermal expansion for both the alloy and shell mold materials showed different evolution at heating and cooling. Thus, one generic simulation were performed with thermal expansion obtained at heating and another one with thermal expansion obtained at cooling. The alloy dimensions were obtained from numerical simulation results of solidification, heat transfer, and deformation phenomena. As compared with experimental results, the numerical simulation results for the shrinkage factors were slightly over-predicted.

  18. 7 CFR 58.641 - Hardening and storage.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 3 2014-01-01 2014-01-01 false Hardening and storage. 58.641 Section 58.641... Procedures § 58.641 Hardening and storage. Immediately after the semifrozen product is placed in its intended container it shall be placed in a hardening tunnel or hardening room to continue the freezing process....

  19. 7 CFR 58.641 - Hardening and storage.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 3 2012-01-01 2012-01-01 false Hardening and storage. 58.641 Section 58.641... Procedures § 58.641 Hardening and storage. Immediately after the semifrozen product is placed in its intended container it shall be placed in a hardening tunnel or hardening room to continue the freezing process....

  20. 7 CFR 58.641 - Hardening and storage.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 3 2013-01-01 2013-01-01 false Hardening and storage. 58.641 Section 58.641... Procedures § 58.641 Hardening and storage. Immediately after the semifrozen product is placed in its intended container it shall be placed in a hardening tunnel or hardening room to continue the freezing process....

  1. 7 CFR 58.641 - Hardening and storage.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 3 2010-01-01 2010-01-01 false Hardening and storage. 58.641 Section 58.641... Procedures § 58.641 Hardening and storage. Immediately after the semifrozen product is placed in its intended container it shall be placed in a hardening tunnel or hardening room to continue the freezing process....

  2. 7 CFR 58.641 - Hardening and storage.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 3 2011-01-01 2011-01-01 false Hardening and storage. 58.641 Section 58.641... Procedures § 58.641 Hardening and storage. Immediately after the semifrozen product is placed in its intended container it shall be placed in a hardening tunnel or hardening room to continue the freezing process....

  3. Laser Surface Hardening of AISI 1045 Steel

    NASA Astrophysics Data System (ADS)

    Li, Ruifeng; Jin, Yajuan; Li, Zhuguo; Qi, Kai

    2014-09-01

    The study investigates laser surface hardening in the AISI 1045 steel using two different types of industrial laser: a high-power diode laser (HPDL) and a CO2 laser, respectively. The effect of process parameters such as beam power, travel speed on structure, case depth, and microhardness was examined. In most cases, a heat-affected zone (HAZ) formed below the surface; a substantial increase in surface hardness was achieved. In addition, big differences were found between the hardened specimens after HPDL surface hardening and CO2 laser surface hardening. For HPDL, depths of the HAZ were almost equal in total HAZ o, without surface melting. For CO2 laser, the depths changed a lot in the HAZ, with surface melting in the center. To better understand the difference of laser hardening results when use these two types of laser, numerical (ANSYS) analysis of the heat conduction involved in the process was also studied. For HPDL method, a rectangular beam spot and uniform energy distribution across the spot were assumed, while for CO2 laser, a circular beam spot and Gaussian energy distribution were assumed. The results showed that the energy distribution variety altered the thermal cycles of the HAZ dramatically. The rectangular HPDL laser beam spot with uniform energy distribution is much more feasible for laser surface hardening.

  4. Embrittlernent of irradiated F82H in the absence of irradiation hardening

    SciTech Connect

    Klueh, Ronald L; Shiba, Kiyoyuki; Sokolov, Mikhail A

    2009-01-01

    Neutron irradiation of 7-12% Cr ferritic/martensitic steels below 425-450 C produces microstructural defects and precipitation that cause an increase in yield stress. This irradiation hardening causes embrittlement, which is observed in a Charpy impact or fracture toughness test as an increase in the ductile-brittle transition temperature. Based on observations that show little change in strength in steels irradiated above 425-450 C, the general conclusion has been that no embrittlement occurs above these temperatures. In a recent study of F82H steel, significant embrittlement was observed after irradiation at 500 C. This embrittlement is apparently due to irradiation-accelerated Laves-phase precipitation. Observations of the embrittlement in the absence of hardening has been examined and analyzed with thermal-aging studies and computational thermodynamics calculations to illuminate and understand the effect.

  5. The microstructure of neutron irradiated type-348 stainless steel and its relation to creep and hardening

    NASA Astrophysics Data System (ADS)

    Thomas, L. E.; Beeston, J. M.

    1982-06-01

    Annealed type-348 stainless steel specimens irradiated to 33 to 39 dpa at 350°C were examined by transmission electron microscopy to determine the cause of pronounced irradiation creep and hardening. The irradiation produced very high densities of 1-2 nm diameter helium bubbles, 2-20 nm diameter faulted (Frank) dislocation loops and 10 nm diameter precipitate particles. These defects account for the observed irradiation hardening but do not explain the creep strains. Too few point defects survive as faulted dislocation loops for significant creep by the stress-induced preferential absorption (SIPA) mechanism and there are not enough unfaulted dislocations for creep by climb-induced glide. Also, the irradiation-induced precipitates are face-centred cubic G-phase (a niobium nickel suicide), and cannot cause creep. It is suggested that the irradiation creep occurs by a grain-boundary movement mechanism such as diffusion accomodated grain-boundary sliding.

  6. Shot Peening and Thermal Stress Relaxation in 17-4 PH Stainless Steel

    NASA Astrophysics Data System (ADS)

    Qin, Enwei; Chen, Guoxing; Tan, Ziming; Wu, Shuhui

    2015-11-01

    Shot peening is an effective process to enhance the fatigue performance of turbine blades. In this study, the effect of peening pressures was discussed in terms of the residual stress distribution and the surface morphology. Shot peening processes were designed at varying pressures on a 17-4 PH martensitic stainless steel. The profiles of hardness and residual stress were characterized in the cross section. The thermal stress relaxation was further carried out to evaluate the stability of the compressive residual stress under service temperatures of turbine blades. Results show that a maximum stress depth is obtained with peening pressure of 0.40 MPa, and the residual stress can be maintained up to 400 °C, which ensures the service in low-pressure turbine blades.

  7. Mechanical Properties of 17-4PH Stainless Steel Foam Panels

    NASA Technical Reports Server (NTRS)

    Raj, S. V.; Ghosn, L. J.; Lerch, B. a.; Hebsur, M.; Cosgriff, L. M.; Fedor, J.

    2007-01-01

    Rectangular 17-4PH stainless steel sandwiched foam panels were fabricated using a commercial manufacturing technique by brazing two sheets to a foam core. Microstructural observations and ultrasonic nondestructive evaluation of the panels revealed large variations in the quality of the brazed areas from one panel to the next as well as within the same panel. Shear tests conducted on specimens machined from the panels exhibited failures either in the brazed region or in the foam core for the poorly brazed and well-brazed samples, respectively. Compression tests were conducted on the foam cores to evaluate their elastic and plastic deformation behavior. These data were compared with published data on polymeric and metallic foams, and with theoretical deformation models proposed for open cell foams.

  8. Microstructure evolution in age-hardenable aluminium alloy during processing by hydrostatic extrusion.

    PubMed

    Lewandowska, M

    2006-10-01

    In the present work, scanning and transmission electron microscopy were used to investigate the microstructural evolution occurring during the hydrostatic extrusion of an age-hardenable aluminium alloy. It was shown that processing by hydrostatic extrusion leads to grain refinement to 95 nm in equivalent diameter. Hydrostatic extrusion also influences the geometrical parameters of two different types of particle: intermetallic inclusions and precipitates. The intermetallic inclusions slightly decrease in mean equivalent diameter, but their size remains at the micrometre level. The precipitates are fragmented to nanoscale spherical particles, and their evolution delays the process of grain refinement. PMID:17100901

  9. Modeling of Irradiation Hardening of Polycrystalline Materials

    SciTech Connect

    Li, Dongsheng; Zbib, Hussein M.; Garmestani, Hamid; Sun, Xin; Khaleel, Mohammad A.

    2011-09-14

    High energy particle irradiation of structural polycrystalline materials usually produces irradiation hardening and embrittlement. The development of predict capability for the influence of irradiation on mechanical behavior is very important in materials design for next generation reactors. In this work a multiscale approach was implemented to predict irradiation hardening of body centered cubic (bcc) alpha-iron. The effect of defect density, texture and grain boundary was investigated. In the microscale, dislocation dynamics models were used to predict the critical resolved shear stress from the evolution of local dislocation and defects. In the macroscale, a viscoplastic self-consistent model was applied to predict the irradiation hardening in samples with changes in texture and grain boundary. This multiscale modeling can guide performance evaluation of structural materials used in next generation nuclear reactors.

  10. Modeling of anisotropic hardening of sheet metals

    NASA Astrophysics Data System (ADS)

    Yoshida, Fusahito; Hamasaki, Hiroshi; Uemori, Takeshi

    2013-12-01

    To describe the evolution of anisotropy of sheet metals, in terms of both r-values and stresses, the present paper proposes anisotropic hardening models, where the shape of yield surface changes with increasing plastic strain. In this framework of modeling, any types of yield functions are able to be used. The evolution of anisotropy is expressed by updating the yield function as an interpolation between two yield functions defined at two different effective plastic strains. In this paper, two types of interpolation models, i.e., nonlinear interpolation model and piecewise interpolation model are presented. These models are validated by comparing the experimental data on 3003-O aluminum sheet (after Hu, Int J Plasticity 23, 620-639, 2007). To describe the Bauschinger effect, the combined anisotropic-kinematic hardening model is formulated based on Yoshida-Uemori kinematic hardening model.

  11. Phenomenological modeling of hardening and thermal recovery in metals

    NASA Technical Reports Server (NTRS)

    Chan, K. S.; Lindholm, U. S.; Bodner, S. R.

    1988-01-01

    Modeling of hardening and thermal recovery in metals is considered within the context of unified elastic-viscoplastic theories. Specifically, the choices of internal variables and hardening measures, and the resulting hardening response obtained by incorporating saturation-type evolution equations into two general forms of the flow law are examined. Based on the analytical considerations, a procedure for delineating directional and isotropic hardening from uniaxial hardening data has been developed for the Bodner-Partom model and applied to a nickel-base superalloy, B1900 + Hf. Predictions based on the directional hardening properties deduced from the monotonic loading data are shown to be in good agreement with results of cyclic tests.

  12. Thermoelastic constitutive equations for chemically hardening materials

    NASA Technical Reports Server (NTRS)

    Shaffer, B. W.; Levitsky, M.

    1974-01-01

    Thermoelastic constitutive equations are derived for a material undergoing solidification or hardening as the result of a chemical reaction. The derivation is based upon a two component model whose composition is determined by the degree of hardening, and makes use of strain-energy considerations. Constitutive equations take the form of stress rate-strain rate relations, in which the coefficients are time-dependent functions of the composition. Specific results are developed for the case of a material of constant bulk modulus which undergoes a transition from an initial liquidlike state into an isotropic elastic solid. Potential applications are discussed.

  13. 'Work-Hardenable' Ductile Bulk Metallic Glass

    SciTech Connect

    Das, Jayanta; Eckert, Juergen; Tang Meibo; Wang Weihua; Kim, Ki Buem; Baier, Falko; Theissmann, Ralf

    2005-05-27

    Usually, monolithic bulk metallic glasses undergo inhomogeneous plastic deformation and exhibit poor ductility (<1%) at room temperature. We present a new class of bulk metallic glass, which exhibits high strength of up to 2265 MPa together with extensive 'work hardening' and large ductility of 18%. Significant increase in the flow stress was observed during deformation. The 'work-hardening' capability and ductility of this class of metallic glass is attributed to a unique structure correlated with atomic-scale inhomogeneity, leading to an inherent capability of extensive shear band formation, interactions, and multiplication of shear bands.

  14. Radiation Hardened Electronics for Space Environments (RHESE)

    NASA Technical Reports Server (NTRS)

    Keys, Andrew S.; Adams, James H.; Frazier, Donald O.; Patrick, Marshall C.; Watson, Michael D.; Johnson, Michael A.; Cressler, John D.; Kolawa, Elizabeth A.

    2007-01-01

    Radiation Environmental Modeling is crucial to proper predictive modeling and electronic response to the radiation environment. When compared to on-orbit data, CREME96 has been shown to be inaccurate in predicting the radiation environment. The NEDD bases much of its radiation environment data on CREME96 output. Close coordination and partnership with DoD radiation-hardened efforts will result in leveraged - not duplicated or independently developed - technology capabilities of: a) Radiation-hardened, reconfigurable FPGA-based electronics; and b) High Performance Processors (NOT duplication or independent development).

  15. Did Lake Bonneville Experience A Major Water-Budget Shift At 17.4 cal ka?

    NASA Astrophysics Data System (ADS)

    Oviatt, C.

    2009-12-01

    Lake Bonneville, in western Utah, had transgressed to its highest level by 18.3 cal ka, overflowed into the Snake River drainage basin until 17.4 cal ka, then catastrophically dropped 100 m as its overflow threshold was washed out. This event, which is referred to as the “Bonneville flood,” is well documented geomorphically, stratigraphically, and geochronologically. At the same time the Bonneville flood was occurring, the level of Lake Estancia in central New Mexico dropped over 30 m then returned to its previous high level in an event caused by climate change in that basin. The question is: “did Lake Bonneville experience a correlative climate-induced shift in its water budget (a decrease in the ratio of input to output), even while it continuously overflowed before, during, and after the Bonneville flood?” The answer to this question has a bearing on the global effects of the climate change that is well documented in the Estancia basin. Data from sediment cores from the Bonneville basin are providing a means to address the question. Data include: ostracode faunal changes, total inorganic carbon, stable isotopes, detrital sand, and mineralogy. The challenge is to identify the measurable characteristics of the sediment core that can be used to clearly separate the effects of water-budget change from those caused by the catastrophic (essentially instantaneous) 100-m lowering of Lake Bonneville.

  16. Precipitates and Grain Boundary Strength of an Fe-Mn-Ni Alloy

    NASA Astrophysics Data System (ADS)

    Heo, Yoon-Uk; Jang, Jae Hoon; Lee, Hu-Chul

    2012-11-01

    The effect of grain boundary (GB) precipitates on the GB strength of an age-hardened Fe-7.8Mn-8.2Ni alloy was investigated. Premature intergranular fracture was observed after age hardening due to the precipitation of θ-MnNi precipitates at prior austenite grain boundaries. However, the conversion of GB θ precipitates to austenite by a short second aging at 793 K (520 °C) after peak aging at 713 K (440 °C) resulted in a remarkable improvement of GB strength. The result strongly supports the proposition that the weak bonding of GB θ precipitates to the matrix is the main reason for GB embrittlement in age-hardened Fe-Mn-Ni alloys.

  17. Precipitation Recycling

    NASA Technical Reports Server (NTRS)

    Eltahir, Elfatih A. B.; Bras, Rafael L.

    1996-01-01

    The water cycle regulates and reflects natural variability in climate at the regional and global scales. Large-scale human activities that involve changes in land cover, such as tropical deforestation, are likely to modify climate through changes in the water cycle. In order to understand, and hopefully be able to predict, the extent of these potential global and regional changes, we need first to understand how the water cycle works. In the past, most of the research in hydrology focused on the land branch of the water cycle, with little attention given to the atmospheric branch. The study of precipitation recycling which is defined as the contribution of local evaporation to local precipitation, aims at understanding hydrologic processes in the atmospheric branch of the water cycle. Simply stated, any study on precipitation recycling is about how the atmospheric branch of the water cycle works, namely, what happens to water vapor molecules after they evaporate from the surface, and where will they precipitate?

  18. STRONTIUM PRECIPITATION

    DOEpatents

    McKenzie, T.R.

    1960-09-13

    A process is given for improving the precipitation of strontium from an aqueous phosphoric-acid-containing solution with nickel or cobalt ferrocyanide by simultaneously precipitating strontium or calcium phosphate. This is accomplished by adding to the ferrocyanide-containing solution calcium or strontium nitrate in a quantity to yield a concentration of from 0.004 to 0.03 and adjusting the pH of the solution to a value of above 8.

  19. SEU hardening of CMOS memory circuit

    NASA Technical Reports Server (NTRS)

    Whitaker, S.; Canaris, J.; Liu, K.

    1990-01-01

    This paper reports a design technique to harden CMOS memory circuits against Single Event Upset (SEU) in the space environment. A RAM cell and Flip Flop design are presented to demonstrate the method. The Flip Flop was used in the control circuitry for a Reed Solomon encoder designed for the Space Station.

  20. Extraordinary strain hardening by gradient structure

    PubMed Central

    Wu, XiaoLei; Jiang, Ping; Chen, Liu; Yuan, Fuping; Zhu, Yuntian T.

    2014-01-01

    Gradient structures have evolved over millions of years through natural selection and optimization in many biological systems such as bones and plant stems, where the structures change gradually from the surface to interior. The advantage of gradient structures is their maximization of physical and mechanical performance while minimizing material cost. Here we report that the gradient structure in engineering materials such as metals renders a unique extra strain hardening, which leads to high ductility. The grain-size gradient under uniaxial tension induces a macroscopic strain gradient and converts the applied uniaxial stress to multiaxial stresses due to the evolution of incompatible deformation along the gradient depth. Thereby the accumulation and interaction of dislocations are promoted, resulting in an extra strain hardening and an obvious strain hardening rate up-turn. Such extraordinary strain hardening, which is inherent to gradient structures and does not exist in homogeneous materials, provides a hitherto unknown strategy to develop strong and ductile materials by architecting heterogeneous nanostructures. PMID:24799688

  1. Modifications of the Response of Materials to Shock Loading by Age Hardening

    NASA Astrophysics Data System (ADS)

    Millett, Jeremy C. F.

    2015-10-01

    The shock response of two age-hardened alloys, aluminum 6061 and copper-2 wt pct beryllium (CuBe), has been investigated in terms of their microstructual state; either solution treated or age hardened. While age hardening induces large increases in strength at quasi-static strain rates, age hardening does not produce the same magnitude of strength increase during shock loading. Examination of the shocked microstructures (of 6061) indicates that the presence of a fine distribution of precipitates throughout the microstructure hinders the motion and generation of dislocations and hence reduces the strain-rate sensitivity of the aged material, thus allowing the properties of the solution-treated state to approach those of the aged. It has also been observed that the shear strength of solution-treated CuBe is near identical to that of pure copper. It is suggested that this is the result of two competing processes; large lattice strains as beryllium substitutes onto the copper lattice inducing a high degree of solution strengthening acting against a reduction in shear strength caused by twinning in the alloy.

  2. 'Fire hardening' spear wood does slightly harden it, but makes it much weaker and more brittle.

    PubMed

    Ennos, Antony Roland; Chan, Tak Lok

    2016-05-01

    It is usually assumed that 'fire hardening' the tips of spears, as practised by hunter-gatherers and early Homo spp., makes them harder and better suited for hunting. This suggestion was tested by subjecting coppiced poles of hazel to a fire-hardening process and comparing their mechanical properties to those of naturally seasoned poles. A Shore D hardness test showed that fire treatment slightly increased the hardness of the wood, but flexural and impact tests showed that it reduced the strength and work of fracture by 30% and 36%, respectively. These results suggest that though potentially slightly sharper and more durable, fire-hardened tips would actually be more likely to break off when used, as may have been the case with the earliest known wooden tool, the Clacton spear. Fire might first have been used to help sharpen the tips of spears, and fire-hardening would have been a mostly negative side effect, not its primary purpose. PMID:27194289

  3. 7 CFR 58.622 - Hardening and storage rooms.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 3 2012-01-01 2012-01-01 false Hardening and storage rooms. 58.622 Section 58.622 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Standards....622 Hardening and storage rooms. Hardening and storage rooms for frozen desserts shall be...

  4. 7 CFR 58.622 - Hardening and storage rooms.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 3 2013-01-01 2013-01-01 false Hardening and storage rooms. 58.622 Section 58.622 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Standards....622 Hardening and storage rooms. Hardening and storage rooms for frozen desserts shall be...

  5. 7 CFR 58.622 - Hardening and storage rooms.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 3 2014-01-01 2014-01-01 false Hardening and storage rooms. 58.622 Section 58.622 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Standards....622 Hardening and storage rooms. Hardening and storage rooms for frozen desserts shall be...

  6. 7 CFR 58.622 - Hardening and storage rooms.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 3 2010-01-01 2010-01-01 false Hardening and storage rooms. 58.622 Section 58.622 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Standards....622 Hardening and storage rooms. Hardening and storage rooms for frozen desserts shall be...

  7. 7 CFR 58.622 - Hardening and storage rooms.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 3 2011-01-01 2011-01-01 false Hardening and storage rooms. 58.622 Section 58.622 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Standards....622 Hardening and storage rooms. Hardening and storage rooms for frozen desserts shall be...

  8. Neutron energy spectrum influence on irradiation hardening and microstructural development of tungsten

    DOE PAGESBeta

    Fukuda, Makoto; Kiran Kumar, N. A. P.; Koyanagi, Takaaki; Garrison, Lauren M.; Snead, Lance L.; Katoh, Yutai; Hasegawa, Akira

    2016-07-02

    We performed a neutron irradiation to single crystal pure tungsten in the mixed spectrum High Flux Isotope Reactor (HFIR). In order to investigate the influences of neutron energy spectrum, the microstructure and irradiation hardening were compared with previous data obtained from the irradiation campaigns in the mixed spectrum Japan Material Testing Reactor (JMTR) and the sodium-cooled fast reactor Joyo. The irradiation temperatures were in the range of ~90–~800 °C and fast neutron fluences were 0.02–9.00 × 1025 n/m2 (E > 0.1 MeV). Post irradiation evaluation included Vickers hardness measurements and transmission electron microscopy. Moreover, the hardness and microstructure changes exhibitedmore » a clear dependence on the neutron energy spectrum. The hardness appeared to increase with increasing thermal neutron flux when fast fluence exceeds 1 × 1025 n/m2 (E > 0.1 MeV). Finally, irradiation induced precipitates considered to be χ- and σ-phases were observed in samples irradiated to >1 × 1025 n/m2 (E > 0.1 MeV), which were pronounced at high dose and due to the very high thermal neutron flux of HFIR. Although the irradiation hardening mainly caused by defects clusters in a low dose regime, the transmutation-induced precipitation appeared to impose additional significant hardening of the tungsten.« less

  9. Effectiveness of hardening threaded parts by plastic deformation

    SciTech Connect

    Pyshkin, V.A.; Belai, S.V.; Dyad'kova, I.G.

    1983-03-01

    The rules of hardening threaded parts by roller burning the root of the inner diameter of a thread are studied. The effectiveness of hardening increases where the allowance for the inner diameter increases. By equations, a change in the inner diameter can be used to determine the depth of work hardening residual compressive stress, fatigue limit, and the mechanical properties of the threaded part. The effective stress concentration factor, increase in transmission load, and average tensile stress in cyclic loading, are also calculated. Equations help to determine the depth of hardening necessary; the optimum conditions of burnishing; and the maximum increase in fatigue strength, with optimum hardening conditions.

  10. A nanoscale co-precipitation approach for property enhancement of Fe-base alloys

    PubMed Central

    Zhang, Zhongwu; Liu, Chain Tsuan; Miller, Michael K.; Wang, Xun-Li; Wen, Yuren; Fujita, Takeshi; Hirata, Akihiko; Chen, Mingwei; Chen, Guang; Chin, Bryan A.

    2013-01-01

    Precipitate size and number density are two key factors for tailoring the mechanical behavior of nanoscale precipitate-hardened alloys. However, during thermal aging, the precipitate size and number density change, leading to either poor strength or high strength but significantly reduced ductility. Here we demonstrate, by producing nanoscale co-precipitates in composition-optimized multicomponent precipitation-hardened alloys, a unique approach to improve the stability of the alloy against thermal aging and hence the mechanical properties. Our study provides compelling experimental evidence that these nanoscale co-precipitates consist of a Cu-enriched bcc core partially encased by a B2-ordered Ni(Mn, Al) phase. This co-precipitate provides a more complex obstacle for dislocation movement due to atomic ordering together with interphases, resulting in a high yield strength alloy without sacrificing alloy ductility. PMID:23429646

  11. YIELD STRENGTH PREDICTION FOR RAPID AGE-HARDENING HEAT TREATMENT OF ALUMINUM ALLOYS

    SciTech Connect

    Yin, Hebi; Sabau, Adrian S; Ludtka, Gerard Michael; Skszek, Timothy; Niu, X

    2013-01-01

    A constitutive model has been developed to predict the yield strength aging curves for aluminum casting alloys during non-isothermal age-hardening processes. The model provides the specific relationship between the process variables and yield strength. Several aging heat treatment scenarios have been investigated using the proposed model, including two-step aging recipes. Two-step aging heat treatments involve a low temperature regime to promote nucleation of secondary phases and a second step at higher temperature for the growth of the secondary phases. The predicted results show that yield strength of approximately 300MPa might be obtained in shorter aging time, of approximately 30 minutes. Thus, better mechanical properties can be obtained by optimizing the time-temperature schedules for the precipitation hardening process of heat treatable aluminum alloys.

  12. Precipitation Matters

    ERIC Educational Resources Information Center

    McDuffie, Thomas

    2007-01-01

    Although weather, including its role in the water cycle, is included in most elementary science programs, any further examination of raindrops and snowflakes is rare. Together rain and snow make up most of the precipitation that replenishes Earth's life-sustaining fresh water supply. When viewed individually, raindrops and snowflakes are quite…

  13. Construction procedures using self hardening fly ash

    NASA Astrophysics Data System (ADS)

    Thornton, S. I.; Parker, D. G.

    1980-07-01

    Fly ash produced in Arkansas from burning Wyoming low sulfur coal is self-hardening and can be effective as a soil stabilizing agent for clays and sands. The strength of soil-self hardening fly ash develops rapidly when compacted immediately after mixing. Seven day unconfined compressive strengths up to 1800 psi were obtained from 20% fly ash and 80% sand mixtures. A time delay between mixing the fly ash with the soil and compaction of the mixture reduced the strength. With two hours delay, over a third of the strength was lost and with four hours delay, the loss was over half. Gypsum and some commercial concrete retarders were effective in reducing the detrimental effect of delayed compaction. Adequate mixing of the soil and fly ash and rapid compaction of the mixtures were found to be important parameters in field construction of stabilized bases.

  14. Modeling the Case Hardening of Automotive Components

    NASA Astrophysics Data System (ADS)

    Munikamal, Tiruttani; Sundarraj, Suresh

    2013-04-01

    A generalized framework has been developed within ABAQUS to model the surface hardening heat treatment processes for automotive steel components. The macro-scale heat transfer and stress calculations during the heating and quenching are coupled with the microstructural phase calculations, defined through a user routine, to estimate key process parameters such as case depth and surface hardness. This model has been applied to predict these parameters in two key industrial processes, i.e., case hardening of crankshafts and case carburization of gears. The results of the case depth and hardness calculations have been validated with the literature and in-house plant data. The effect of varying quench conditions on the overall stress distribution changes within the component has been outlined.

  15. Radiation-hardened transistor and integrated circuit

    DOEpatents

    Ma, Kwok K.

    2007-11-20

    A composite transistor is disclosed for use in radiation hardening a CMOS IC formed on an SOI or bulk semiconductor substrate. The composite transistor has a circuit transistor and a blocking transistor connected in series with a common gate connection. A body terminal of the blocking transistor is connected only to a source terminal thereof, and to no other connection point. The blocking transistor acts to prevent a single-event transient (SET) occurring in the circuit transistor from being coupled outside the composite transistor. Similarly, when a SET occurs in the blocking transistor, the circuit transistor prevents the SET from being coupled outside the composite transistor. N-type and P-type composite transistors can be used for each and every transistor in the CMOS IC to radiation harden the IC, and can be used to form inverters and transmission gates which are the building blocks of CMOS ICs.

  16. Work hardening: occupational therapy in industrial rehabilitation.

    PubMed

    Matheson, L N; Ogden, L D; Violette, K; Schultz, K

    1985-05-01

    Work hardening, presented in this paper as a "new" service for the industrially injured, is actually well grounded in the traditional models and practices of occupational therapy. From the profession's early roots in industrial therapy to the development of a variety of programs for the industrially injured through the 1950s and 1960s, the historical and philosophical bases of occupational therapy support the use of work as an evaluative and therapeutic medium. What is actually new is the adoption of terminology, technology, and a program format that fits in with the needs of consumers in the 1980s. Recent developments that created the need for the specialized services that occupational therapists are uniquely qualified to provide include growth of private sector vocational rehabilitation, changes in workers' compensation laws, and increasing costs of vocational rehabilitation. This paper describes work hardening in its present form. A case example is given that demonstrates how work hardening can be a cost-effective and time-saving bridge which spans the gap between curative medicine and the return to work. PMID:4014411

  17. Dislocation Multi-junctions and Strain Hardening

    SciTech Connect

    Bulatov, V; Hsiung, L; Tang, M; Arsenlis, A; Bartelt, M; Cai, W; Florando, J; Hiratani, M; Rhee, M; Hommes, G; Pierce, T; Diaz de la Rubia, T

    2006-06-20

    At the microscopic scale, the strength of a crystal derives from the motion, multiplication and interaction of distinctive line defects--dislocations. First theorized in 1934 to explain low magnitudes of crystal strength observed experimentally, the existence of dislocations was confirmed only two decades later. Much of the research in dislocation physics has since focused on dislocation interactions and their role in strain hardening: a common phenomenon in which continued deformation increases a crystal's strength. The existing theory relates strain hardening to pair-wise dislocation reactions in which two intersecting dislocations form junctions tying dislocations together. Here we report that interactions among three dislocations result in the formation of unusual elements of dislocation network topology, termed hereafter multi-junctions. The existence of multi-junctions is first predicted by Dislocation Dynamics (DD) and atomistic simulations and then confirmed by the transmission electron microscopy (TEM) experiments in single crystal molybdenum. In large-scale Dislocation Dynamics simulations, multi-junctions present very strong, nearly indestructible, obstacles to dislocation motion and furnish new sources for dislocation multiplication thereby playing an essential role in the evolution of dislocation microstructure and strength of deforming crystals. Simulation analyses conclude that multi-junctions are responsible for the strong orientation dependence of strain hardening in BCC crystals.

  18. Stage IV work hardening in cubic metals

    SciTech Connect

    Rollett, A.D.; Kocks, U.F.; Doherty, R.D.

    1986-01-01

    The work hardening of fcc metals at large strains is discussed with reference to the linear stress-strain behavior often observed at large strains and known as Stage IV. The experimental evidence shows that Stage IV is a work hardening phenomenon that is found quite generally, even in pure fcc metals subjected to homogeneous deformation. A simple model for Stage IV in pure metals is presented, based on the accumulation of dislocation debris. Experiments are described for large strain torsion tests on four aluminum alloys. The level and extent of Stage IV scaled with the saturation stress that would represent the end of Stage III in the absence of a Stage IV. Reversing the torsion after large prestrains produced transient reductions in the work hardening. The strain rate sensitivity was also measured before and during the transient and found not to vary significantly. The microstructure observed at large strains in an Mg alloy suggest that Stage IV can occur in the absence of microband formation. Previous proposals for the cause of Stage IV are reviewed and found to be not supported by recent experimental data.

  19. Pulsed laser surface hardening of ferrous alloys.

    SciTech Connect

    Xu, Z.; Reed, C. B.; Leong, K. H.; Hunter, B. V.

    1999-09-30

    A high power pulsed Nd:YAG laser and special optics were used to produce surface hardening on 1045 steel and gray cast iron by varying the process parameters. Unlike CO{sub 2} lasers, where absorptive coatings are required, the higher absorptivity of ferrous alloys at the Nd:YAG laser wavelength eliminates the necessity of applying a coating before processing. Metallurgical analysis of the treated tracks showed that very fine and hard martensitic microstructure (1045 steel) or inhomogeneous martensite (gray cast iron) were obtained without surface melting, giving maximum hardness of HRC 61 and HRC 40 for 1045 steel and gray cast iron respectively. The corresponding maximum case depths for both alloys at the above hardness are 0.6 mm. Gray cast iron was more difficult to harden without surface melting because of its lower melting temperature and a significantly longer time-at-temperature required to diffuse carbon atoms from the graphite flakes into the austenite matrix during laser heating. The thermal distortion was characterized in term of flatness changes after surface hardening.

  20. Study of a synthetic human olfactory receptor 17-4: expression and purification from an inducible mammalian cell line.

    PubMed

    Cook, Brian L; Ernberg, Karin E; Chung, Hyeyoun; Zhang, Shuguang

    2008-01-01

    In order to begin to study the structural and functional mechanisms of olfactory receptors, methods for milligram-scale purification are required. Here we demonstrate the production and expression of a synthetically engineered human olfactory receptor hOR17-4 gene in a stable tetracycline-inducible mammalian cell line (HEK293S). The olfactory receptor gene was fabricated from scratch using PCR-based gene-assembly, which facilitated codon optimization and attachment of a 9-residue bovine rhodopsin affinity tag for detection and purification. Induction of adherent cultures with tetracycline together with sodium butyrate led to hOR17-4 expression levels of approximately 30 microg per 150 mm tissue culture plate. Fos-choline-based detergents proved highly capable of extracting the receptors, and fos-choline-14 (N-tetradecylphosphocholine) was selected for optimal solubilization and subsequent purification. Analysis by SDS-PAGE revealed both monomeric and dimeric receptor forms, as well as higher MW oligomeric species. A two-step purification method of immunoaffinity and size exclusion chromatography was optimized which enabled 0.13 milligrams of hOR17-4 monomer to be obtained at >90% purity. This high purity of hOR17-4 is not only suitable for secondary structural and functional analyses but also for subsequent crystallization trials. Thus, this system demonstrates the feasibility of purifying milligram quantities of the GPCR membrane protein hOR17-4 for fabrication of olfactory receptor-based bionic sensing device. PMID:18682799

  1. Large Scale 3-D Dislocation Dynamics and Atomistic Simulations of Flow and Strain-Hardening Behavior of Metallic Micropillars

    NASA Astrophysics Data System (ADS)

    Rao, Satish

    2015-03-01

    Experimental studies show strong strengthening effects for micrometer-scale FCC as well as two-phase superalloy crystals, even at high initial dislocation densities. This talk shows results from large-scale 3-D discrete dislocation simulations (DDS) used to explicitly model the deformation behavior of FCC Ni (flow stress and strain-hardening) as well as superalloy microcrystals for diameters ranging from 1 - 20 microns. The work shows that two size-sensitive athermal hardening processes, beyond forest and precipitation hardening, are sufficient to develop the dimensional scaling of the flow stress, stochastic stress variation, flow intermittency and, high initial strain-hardening rates, similar to experimental observations for various materials. In addition, 3D dislocation dynamics simulations are used to investigate strain-hardening characteristics and dislocation microstructure evolution with strain in large 20 micron size Ni microcrystals (bulk-like) under three different loading axes: 111, 001 and 110. Three different multi-slip loading axes, < 111 > , < 001 > and < 110 > , are explored for shear strains of ~0.03 and final dislocation densities of ~1013/m2. The orientation dependence of initial strain hardening rates and dislocation microstructure evolution with strain are discussed. The simulated strain hardening results are compared with experimental data under similar loading conditions from bulk single-crystal Ni. Finally, atomistic simulation results on the operation of single arm sources in Ni bipillars with a large angle grain boundary is discussed. The atomistic simulation results are compared with experimental mechanical behavior data on Cu bipillars with a similar large angle grain boundary. This work was supported by AFOSR (Dr. David Stargel), and by a grant of computer time from the DOD High Performance Computing Modernization Program, at the Aeronautical Systems Center/Major Shared Resource Center.

  2. Anomalous temperature dependence of yield stress and work hardening coefficient of B2-stabilized NiTi alloys

    SciTech Connect

    Hosoda, Hideki; Mishima, Yoshinao; Suzuki, Tomoo

    1997-12-31

    Yield stress and work hardening coefficient of B2-stabilized NiTi alloys are investigated using compression tests. Compositions of NiTi alloys are based on Ni-49mol.%Ti, to which Cr, Co and Al are chosen as ternary elements which reduce martensitic transformation temperatures of the B2 phase. Mechanical tests are carried out in liquid nitrogen at 77 K, air at room temperature (R.T.) and in an argon atmosphere between 473 K and 873 K. Only at 77 K, some alloys show characteristic stress-strain curves which indicate stress induced martensitic transformation (SIMT), but the others do not. Work hardening coefficient is found to be between 2 and 11GPa in all the test temperature range. The values are extremely high compared with Young`s modulus of B2 NiTi. Yield stress and work hardening coefficient increase with test temperature between R.T. and about 650 K in most alloys. The anomalous temperature dependence of mechanical properties is not related to SIMT but to precipitation hardening and/or anomalous dislocation motion similar to B2-type CoTi. Solution hardening by adding ternary elements is evaluated to be small for Cr and Co additions, and large for Al addition, depending on difference in atomic size of the ternary element with respect to Ni or Ti.

  3. Duplex precipitates and their effects on the room-temperature fracture behaviour of a NiAl-strengthened ferritic alloy

    DOE PAGESBeta

    Sun, Zhiqian; Song, Gian; Ilavsky, Jan; Liaw, Peter K.

    2015-03-23

    Duplex precipitates are presented in a NiAl-strengthened ferritic alloy. They were characterized by the ultra-small angle X-ray scattering and transmission electron microscope. Fine cooling precipitates with the size of several to tens of nanometres harden the matrix considerably at room temperature. Cracks are likely to initiate from precipitates, and coalesce and propagate quickly through the matrix due to the excessive hardening effect of cooling precipitates, which lead to the premature fracture of NiAl-strengthened ferritic alloys.

  4. Empirical beam hardening correction (EBHC) for CT

    SciTech Connect

    Kyriakou, Yiannis; Meyer, Esther; Prell, Daniel; Kachelriess, Marc

    2010-10-15

    Purpose: Due to x-ray beam polychromaticity and scattered radiation, attenuation measurements tend to be underestimated. Cupping and beam hardening artifacts become apparent in the reconstructed CT images. If only one material such as water, for example, is present, these artifacts can be reduced by precorrecting the rawdata. Higher order beam hardening artifacts, as they result when a mixture of materials such as water and bone, or water and bone and iodine is present, require an iterative beam hardening correction where the image is segmented into different materials and those are forward projected to obtain new rawdata. Typically, the forward projection must correctly model the beam polychromaticity and account for all physical effects, including the energy dependence of the assumed materials in the patient, the detector response, and others. We propose a new algorithm that does not require any knowledge about spectra or attenuation coefficients and that does not need to be calibrated. The proposed method corrects beam hardening in single energy CT data. Methods: The only a priori knowledge entering EBHC is the segmentation of the object into different materials. Materials other than water are segmented from the original image, e.g., by using simple thresholding. Then, a (monochromatic) forward projection of these other materials is performed. The measured rawdata and the forward projected material-specific rawdata are monomially combined (e.g., multiplied or squared) and reconstructed to yield a set of correction volumes. These are then linearly combined and added to the original volume. The combination weights are determined to maximize the flatness of the new and corrected volume. EBHC is evaluated using data acquired with a modern cone-beam dual-source spiral CT scanner (Somatom Definition Flash, Siemens Healthcare, Forchheim, Germany), with a modern dual-source micro-CT scanner (TomoScope Synergy Twin, CT Imaging GmbH, Erlangen, Germany), and with a modern

  5. Acidic precipitation

    SciTech Connect

    Martin, H.C.

    1987-01-01

    At the International Symposium on Acidic Precipitation, over 400 papers were presented, and nearly 200 of them are included here. They provide an overview of the present state of the art of acid rain research. The Conference focused on atmospheric science (monitoring, source-receptor relationships), aquatic effects (marine eutrophication, lake acidification, impacts on plant and fish populations), and terrestrial effects (forest decline, soil acidification, etc.).

  6. [Study on the age-hardenable silver alloy (3 rd report). III. On the ageing process of dental Ag-Pd-Cu-Au alloy (author's transl)].

    PubMed

    Ota, M; Hisatsune, K; Yamane, M

    1975-05-01

    The precipitation hardening process of a dental silver base alloy, Ag-28 Pd-10 Cu-12 wt % Au, was studied by means of X-ray diffraction, hardness measurement and metallographic observations. After solution treatment at 900 degrees C for 30 min, specimens were subjected to anisothermal annealing at the rate of 1 degrees C/min. PdCu ordered phase and alpha2 solid solution (Ag rich phase) precipitated hetelogeneously at the grain boundaries and then grew up into each grain. Drastic increase in hardness was recognized with the spread of nodular region. Electron microscopic observation of these precipitates showed very fine lamellar structure. It is concluded that the age hardening of this alloy could be attributed to this grain boundary precipitation and the softening at the overaged stage to the second grain boundary reaction which produced very coarse lamellar structure. PMID:1058263

  7. Microbiologically Induced Calcite Precipitation Mediated by Sporosarcina pasteurii.

    PubMed

    Bhaduri, Swayamdipta; Debnath, Nandini; Mitra, Sushanta; Liu, Yang; Kumar, Aloke

    2016-01-01

    The particular bacterium under investigation here (S. pasteurii) is unique in its ability, under the right conditions, to induce the hydrolysis of urea (ureolysis) in naturally occurring environments through secretion of an enzyme urease. This process of ureolysis, through a chain of chemical reactions, leads to the formation of calcium carbonate precipitates. This is known as Microbiologically Induced Calcite Precipitation (MICP). The proper culture protocols for MICP are detailed here. Finally, visualization experiments under different modes of microscopy were performed to understand various aspects of the precipitation process. Techniques like optical microscopy, Scanning Electron Microscopy (SEM) and X-Ray Photo-electron Spectroscopy (XPS) were employed to chemically characterize the end-product. Further, the ability of these precipitates to clog pores inside a natural porous medium was demonstrated through a qualitative experiment where sponge bars were used to mimic a pore-network with a range of length scales. A sponge bar dipped in the culture medium containing the bacterial cells hardens due to the clogging of its pores resulting from the continuous process of chemical precipitation. This hardened sponge bar exhibits superior strength when compared to a control sponge bar which becomes compressed and squeezed under the action of an applied external load, while the hardened bar is able to support the same weight with little deformation. PMID:27167458

  8. Hardening by bubbles in He-implanted Ni

    SciTech Connect

    Knapp, J. A.; Follstaedt, D. M.; Myers, S. M.

    2008-01-01

    Detailed finite-element modeling of nanoindentation data is used to obtain the mechanical properties of Ni implanted with 1-10 at. % He. The mechanical properties of this material elucidate the fundamental materials science of dislocation pinning by nanometer-size gas bubbles and also have implications for radiation damage of materials. Cross-section transmission electron microscopy showed that implantation of 1-5 at. % He at room temperature or at 200 deg. C produced a highly damaged layer extending to a depth of 700-800 nm and containing a fine dispersion of He bubbles with diameters of 1.1{+-}0.2 nm. Implantation at 500 deg. C enlarged the bubble sizes. By fitting the nanoindentation data with a finite-element model that includes the responses of both the implanted layer and the unimplanted substrate in the deformation, the Ni(He) layers are shown to have hardnesses as much as approximately seven times that of untreated Ni, up to 8.3{+-}0.6 GPa. Examination of the dependence of yield strength on He concentration, bubble size, and bubble density reveals that an Orowan hardening mechanism is likely to be in operation, indicating that the bubbles pin dislocation motion as strongly as hard second-phase precipitates do. This strong pinning of dislocations by bubbles is also supported by our numerical simulations, which show that substantial applied shear stress is required to move a dislocation through an empty cavity.

  9. Strain hardening mechanisms in a Ni-Mo-Cr alloy

    SciTech Connect

    Dymek, S. ); Dollar, M. ); Klarstrom, D.L. )

    1991-01-01

    HAYNES 242 alloy has been recently developed for gas turbine components applications. This age-hardenable alloy, consisting essentially of Ni-25%Mo-8%Cr, utilizes a long-range-ordering reaction to form uniformly sized and distributed, extremely small (on the order of 10nm), ordered particles. Excellent strength and ductility at elevated temperatures, low thermal expansion characteristics and good oxidation resistance of Haynes 242 alloy has encouraged a number of studies designed to characterize its properties. What is lacking is an attempt to understand the fundamentals of the deformation and strengthening mechanisms in this alloy. This on-going research has been undertaken to explore deformation mechanisms in unaged and aged Haynes 242 alloy. The emphasis has been put on the effects of initial precipitation structure on the development of deformation structure and how it controls selected mechanical properties. This paper presents selected results and reports a change in the deformation mode from crystallographic glide in an unaged alloy into twinning in the presence of ordered particles. Deformation twinning in Ni-Mo and Ni-Mo-Cr alloys was reported earlier but was not discussed in detail. This research sheds light on possible origins of particle-induced twinning in alloys strengthened by small ordered particles.

  10. Phenomenological Analysis of the Kinematic Hardening of HSLA and IF Steels Using Reverse Simple Shear Tests

    SciTech Connect

    Aouafi, A.; Bouvier, S.; Gasperini, M.; Lemoine, X.; Bouaziz, O.

    2007-04-07

    Reverse simple shear tests are used to analyse the Bauschinger effect and the evolution of the kinematic hardening for a wide range of equivalent von Mises strain [0.025 - 0.3]. This work is carried out on two high strength low-alloyed steels. In order to investigate the effect of the precipitates on the macroscopic behaviour, a ferritic mild steel is used as a reference. Different phenomenological descriptions of the back-stress tensor are examined in order to analyse their ability to describe the experimental behaviour.

  11. Phenomenological Analysis of the Kinematic Hardening of HSLA and IF Steels Using Reverse Simple Shear Tests

    NASA Astrophysics Data System (ADS)

    Aouafi, A.; Bouvier, S.; Gaspérini, M.; Lemoine, X.; Bouaziz, O.

    2007-04-01

    Reverse simple shear tests are used to analyse the Bauschinger effect and the evolution of the kinematic hardening for a wide range of equivalent von Mises strain [0.025 - 0.3]. This work is carried out on two high strength low-alloyed steels. In order to investigate the effect of the precipitates on the macroscopic behaviour, a ferritic mild steel is used as a reference. Different phenomenological descriptions of the back-stress tensor are examined in order to analyse their ability to describe the experimental behaviour.

  12. Reverse-Martensitic Hardening of Austenitic Stainless Steel upon Up-quenching

    NASA Astrophysics Data System (ADS)

    Sato, Kiminori; Guo, Defeng; Li, Xiaohong; Zhang, Xiangyi

    2016-08-01

    Reverse-martensitic transformation utilizing up-quenching was demonstrated for austenitic stainless steel. Up-quenching was done following the stress-induced phase modification to martensite and then enrichment of the body-centered-cubic ferrite. Transmission-electron-microscopy observation and Vickers hardness test revealed that the reverse-martensitic transformation yields quench hardening owing to an introduction of highly-concentrated dislocation. It is furthermore found that Cr precipitation on grain boundaries caused by isothermal aging is largely suppressed in the present approach.

  13. Constitutive modelling of evolving flow anisotropy including distortional hardening

    SciTech Connect

    Pietryga, Michael P.; Vladimirov, Ivaylo N.; Reese, Stefanie

    2011-05-04

    The paper presents a new constitutive model for anisotropic metal plasticity that takes into account the expansion or contraction (isotropic hardening), translation (kinematic hardening) and change of shape (distortional hardening) of the yield surface. The experimentally observed region of high curvature ('nose') on the yield surface in the loading direction and flattened shape in the reverse loading direction are modelled here by means of the concept of directional distortional hardening. The modelling of directional distortional hardening is accomplished by means of an evolving fourth-order tensor. The applicability of the model is illustrated by fitting experimental subsequent yield surfaces at finite plastic deformation. Comparisons with test data for aluminium low and high work hardening alloys display a good agreement between the simulation results and the experimental data.

  14. Irradiation-induced precipitation modelling of ferritic steels

    NASA Astrophysics Data System (ADS)

    Yin, You Fa; Faulkner, Roy G.; Lu, Zheng

    2009-06-01

    In high strength low alloy (HSLA) steels typically used in reactor pressure vessels (RPV), irradiation-induced microstructure changes affect the performance of the components. One such change is precipitation hardening due to the formation of solute clusters and/or precipitates which form as a result of irradiation-enhanced solute diffusion and thermodynamic stability changes. The other is irradiation-enhanced tempering which is a result of carbide coarsening due to irradiation-enhanced carbon diffusion. Both effects have been studied using a recently developed Monte Carlo based precipitation kinetics simulation technique and modelling results are compared with experimental measurements. Good agreements have been achieved.

  15. Radiation hardening of diagnostics for fusion reactors

    SciTech Connect

    Baur, J.F.; Engholm, B.A.; Hacker, M.P.; Maya, I.; Miller, P.H.; Toffolo, W.E.; Wojtowicz, S.S.

    1981-12-01

    A list of the diagnostic systems presently used in magnetic confinement fusion experiments is compiled herein. The radiation-sensitive components are identified, and their locations in zones around the machine are indicated. A table of radiation sensitivities of components is included to indicate the data available from previous work in fission reactor, space probe, and defense-related programs. Extrapolation and application to hardening of fusion diagnostic systems requires additional data that are more specific to the fusion radiation environment and fusion components. A list is also given of present radiation-producing facilities where near-term screening tests of materials and components can be performed.

  16. Expecting the Unexpected: Radiation Hardened Software

    NASA Technical Reports Server (NTRS)

    Penix, John; Mehlitz, Peter C.

    2005-01-01

    Radiation induced Single Event Effects (SEEs) are a serious problem for spacecraft flight software, potentially leading to a complete loss of mission. Conventional risk mitigation has been focused on hardware, leading to slow, expensive and outdated on-board computing devices, increased power consumption and launch mass. Our approach is to look at SEEs from a software perspective, and to explicitly design flight software so that it can detect and correct the majority of SEES. Radiation hardened flight software will reduce the significant residual residual risk for critical missions and flight phases, and enable more use of inexpensive and fast COTS hardware.

  17. Strain hardening of steel EP836

    SciTech Connect

    Lyadskaya, A.A.; Lappa, R.M.; Spuskanyuk, V.Z.

    1986-03-01

    The authors investigate the effect of different combinations of cold hydraulic pressing and heat treatment on the physical and mechanical properties of steel EP836 (03N17K10V10MT), containing 0.03% C, 16-17% Ni, 10-11.5% Co, 9.5-11.5% W, 1% Ti, 1% Mo, and 0.15% A1. Deformation of the unaged steel resulted in insignificant hardening without a decrease in plasticity; this agrees with the results of investigations of other steels of this class.

  18. Synthesis, crystal growth and structure of Mg containing {beta}-rhombohedral boron: MgB{sub 17.4}

    SciTech Connect

    Adasch, Volker; Hess, Kai-Uwe; Vojteer, Natascha; Hillebrecht, Harald . E-mail: harald.hillebrecht@ac.uni-freiburg.de

    2006-09-15

    For the first time, single crystals of Mg containing {beta}-rhombohedral boron MgB{sub 17.4} were synthesised from the elements in a Mg/Cu melt at 1600deg. C. The crystal structure determined by the refinement of single crystal data (space group R-3m, a=10.991(2)A, c=24.161(4)A, 890 reflections, 123 variables, R{sub 1}(F)=0.049, wR{sub 2}(I)=0.122) improves and modifies the former structure model derived from earlier investigations on powder samples. Mg is located on four different positions with partial occupation. While the occupation of the sites D (53.3%), E (91%) and F (7.2%) is already known from other boron-rich borides related to {beta}-rhombohedral boron, the occupation of the fourth position (18h, 6.7%) is observed for the first time. Two boron positions show partial occupation. The summation reveals the composition MgB{sub 17.4} and Mg{sub 5.85}B{sub 101.9}, respectively, confirmed by WDX measurements. The single crystals of MgB{sub 17.4} show the highest Mg content ever found. Preliminary measurements indicate no superconductivity.

  19. On massive carbide precipitation during high temperature low cycle fatigue in alloy 800H

    NASA Technical Reports Server (NTRS)

    Sankararao, K. Bhanu; Schuster, H.; Halford, G. R.

    1994-01-01

    The effect of strain rate on massive precipitation and the mechanism for the occurrence of massive precipitation of M23C6 in alloy 800H is investigated during elevated temperature low cycle fatigue testing. It was observed that large M23C6 platelets were in the vicinity of grain and incoherent twin boundaries. The strain controlled fatigue testing at higher strain rates that promoted cyclic hardening enabled massive precipitation to occur more easily.

  20. Phase decomposition in an Fe-40 at.% Cr alloy after isothermal aging and its effect on hardening

    SciTech Connect

    Lopez-Hirata, Victor M. Soriano-Vargas, Orlando; Rosales-Dorantes, Hector J.; Saucedo Munoz, Maribel L.

    2011-08-15

    The phase decomposition process of an Fe-40 at.% Cr alloy was studied after isothermal aging at 475 and 500 deg. C using a high-resolution transmission electron microscope, as well as hardness measurements. High-resolution transmission electron microscope observations showed that the hardening behavior is associated with the formation of the nanometric coherent decomposed Cr-rich and Fe-rich phases with irregular shape and interconnected as expected for a spinodally-decomposed alloy. As the aging progressed, coherent rounded Cr-rich phase precipitates were observed in the Fe-rich phase matrix. The coarsening process of the Cr-rich phase was observed for aging times up to 750 h. Nevertheless, no decrease in hardness with time was observed because of the nanometric size of the Cr-rich phase, less than 10 nm. Aging hardening was higher at 500 deg. C because of the higher decomposition kinetics. - Research Highlights: {yields} Spinodally-decomposed phases showed an interconnected and irregular shape in aged Fe-Cr alloy. {yields} Further aging promoted the formation of nanometric coherent rounded Cr-rich precipitates. {yields} Nanometric Cr-rich phases are responsible for the age hardening. {yields} Coarsening process of these nanometric Cr-rich precipitates caused no decrease in hardness.

  1. Technology Developments in Radiation-Hardened Electronics for Space Environments

    NASA Technical Reports Server (NTRS)

    Keys, Andrew S.; Howell, Joe T.

    2008-01-01

    The Radiation Hardened Electronics for Space Environments (RHESE) project consists of a series of tasks designed to develop and mature a broad spectrum of radiation hardened and low temperature electronics technologies. Three approaches are being taken to address radiation hardening: improved material hardness, design techniques to improve radiation tolerance, and software methods to improve radiation tolerance. Within these approaches various technology products are being addressed including Field Programmable Gate Arrays (FPGA), Field Programmable Analog Arrays (FPAA), MEMS, Serial Processors, Reconfigurable Processors, and Parallel Processors. In addition to radiation hardening, low temperature extremes are addressed with a focus on material and design approaches. System level applications for the RHESE technology products are discussed.

  2. The effect of voids on the hardening of body-centered cubic Fe

    NASA Astrophysics Data System (ADS)

    Nakai, Ryosuke; Yabuuchi, Kiyohiro; Nogami, Shuhei; Hasegawa, Akira

    2016-04-01

    The mechanical properties of metals are affected by various types of defects. Hardening is usually described through the interaction between dislocations and obstacles, in the so-called line tension theory. The strength factor in the line tension theory represents the resistance of a defect against the dislocation motion. In order to understand hardening from the viewpoint of the microstructure, an accurate determination of the strength factor of different types of defects is essential. In the present study, the strength factor of voids in body-centered cubic (BCC) Fe was investigated by two different approaches: one based on the Orowan equation to link the measured hardness with the average size and density of voids, and the other involving direct observation of the interaction between dislocations and voids by transmission electron microscope (TEM). The strength factor of voids induced by ion irradiation estimated by the Orowan equation was 0.6, whereas the strength factor estimated by the direct TEM approach was 0.8. The difference in the strength factors measured by the two approaches is due to the positional relationship between dislocations and voids: the central region of a void is stronger than the tip. Moreover, the gliding plane and the direction of dislocation may also affect the strength factor of voids. This study determined the strength factor of voids in BCC Fe accurately, and suggested that the contribution of voids to the irradiation hardening is larger than that of dislocation loops and Cu-rich precipitates.

  3. Hardened Client Platforms for Secure Internet Banking

    NASA Astrophysics Data System (ADS)

    Ronchi, C.; Zakhidov, S.

    We review the security of e-banking platforms with particular attention to the exploitable attack vectors of three main attack categories: Man-in-the-Middle, Man-in-the-PC and Man-in-the-Browser. It will be shown that the most serious threats come from combination attacks capable of hacking any transaction without the need to control the authentication process. Using this approach, the security of any authentication system can be bypassed, including those using SecureID Tokens, OTP Tokens, Biometric Sensors and Smart Cards. We will describe and compare two recently proposed e-banking platforms, the ZTIC and the USPD, both of which are based on the use of dedicated client devices, but with diverging approaches with respect to the need of hardening the Web client application. It will be shown that the use of a Hardened Browser (or H-Browser) component is critical to force attackers to employ complex and expensive techniques and to reduce the strength and variety of social engineering attacks down to physiological fraud levels.

  4. Hardness variability in commercial and hardened technologies

    SciTech Connect

    Shaneyfelt, M.R.; Winokur, P.S.; Meisenheimer, T.L.; Sexton, F.W.; Roeske, S.B.; Knoll, M.G.

    1994-03-01

    Over the past 10 years, there have been a number of advances in methods to assess and assure the radiation hardness of microelectronics in military and space applications. At the forefront of these is the Qualified Manufacturers List (QML) methodology, in which the hardness of product is ``built-in`` through statistical process control (SPC) of technology parameters relevant to the radiation response, test structure to integrated circuit (IC) correlations, and techniques for extrapolating laboratory test results to varying radiation scenarios. At the same time, there has been renewed interest in the use of commercial technology -- with its enhanced performance, reduced cost, and higher reliability -- in military and space systems. In this paper, we initially demonstrate the application of QML techniques to assure and control the radiation response of hardened technologies. Through several examples, we demonstrate intra-die, wafer-to-wafer, and lot-to-lot variations in a hardened technology. We observe 10 to 30% variations in key technology parameters that result from variability in geometry, process, and design layout. Radiation-induced degradation is seen to mirror preirradiation characteristics. We then evaluate commercial technologies and report considerably higher variability in radiation hardness, i.e., variations by a factor of two to five. This variability is shown to arise from a lack of control of technology parameters relevant to the radiation response, which a commercial manufacturer has no interest in controlling in a normal process flow.

  5. Hardness variability in commercial and hardened technologies

    NASA Astrophysics Data System (ADS)

    Shaneyfelt, M. R.; Winokur, P. S.; Meisenheimer, T. L.; Sexton, F. W.; Roeske, S. B.; Knoll, M. G.

    1994-01-01

    Over the past 10 years, there have been a number of advances in methods to assess and assure the radiation hardness of microelectronics in military and space applications. At the forefront of these is the Qualified Manufacturers List (QML) methodology, in which the hardness of product is 'built-in' through statistical process control (SPC) of technology parameters relevant to the radiation response, test structure to integrated circuit (IC) correlations, and techniques for extrapolating laboratory test results to varying radiation scenarios. At the same time, there has been renewed interest in the use of commercial technology -- with its enhanced performance, reduced cost, and higher reliability -- in military and space systems. In this paper, we initially demonstrate the application of QML techniques to assure and control the radiation response of hardened technologies. Through several examples, we demonstrate intra-die, wafer-to-wafer, and lot-to-lot variations in a hardened technology. We observe 10 to 30% variations in key technology parameters that result from variability in geometry, process, and design layout. Radiation-induced degradation is seen to mirror preirradiation characteristics. We then evaluate commercial technologies and report considerably higher variability in radiation hardness, i.e., variations by a factor of two to five. This variability is shown to arise from a lack of control of technology parameters relevant to the radiation response, which a commercial manufacturer has no interest in controlling in a normal process flow.

  6. Flow and fracture of particle hardened copper-titanium alloys: Interplay of slip and twinning

    NASA Astrophysics Data System (ADS)

    Radetic, Tamara

    The flow and fracture behavior of Cu-rich Cu-Ti alloys hardened by ordered, metastable, coherent betasp' precipitates (Cusb4Ti,\\ D1sb{a} superstructure) are particularly interesting because these alloys show an unusual propensity to twin profusely after small amounts of plastic flow by slip. The mechanical behavior was studied using standard tensile testing along with modern electron optical techniques including CTEM, SEM and HREM. The deformation substructure in the early stages of aging and in samples aged for longer times is characterized by the coupled motion of five dislocations of the same Burgers vector (superdislocations in the D1sb{a} structure) after small degrees of deformation. Characterization of the fine-scale structure of the mechanical twins which form in the particle hardened Cu-Ti alloys is also reported in this study. The growth of deformation twins occurs via the motion of so-called G-ledges at twin/matrix interfaces and via a coalescence of fine twins. The atomic structure of the coherent twin/matrix interfaces and associated single and multiple layer ledges are also elucidated. Incoherent interfaces at the tip of deformation twins generated by 90sp° and 30sp° twinning dislocations have been investigated. The twin/twin and slip/twin interactions have been studied and analyzed as well as the effect of grain boundaries on deformation twinning. Deformation twins appear to nucleate at dislocation pile-ups serving as a stress relaxation mechanism. Shear transfer through obstacle twins is effected by slip and twining. The dominant strengthening mechanism is concluded to be coherency strain hardening and the interplay of particle strengthening and grain size hardening is analyzed. The particle dispersion was found to influence the Hall-Petch factor but a detailed understanding of these synergetic effects was not established. The fracture mode of the underaged Cu-Ti alloys was found to be dimpled ductile tearing.

  7. Radiation-Hardened Electronics for Space Environments (RHESE)

    NASA Technical Reports Server (NTRS)

    Keys, Andrew S.; Adams, James H.; Patrick, Marshall C.; Johnson, Michael; Cressler, John D.

    2008-01-01

    This conference poster explores NASA's Radiation-Hardened Electronics for Space Environments project. This project aims to advance the state of the art in high performance, radiation-hardened electronics that enable the long-term, reliable operation of a spacecraft in extreme radiation and temperature of space and the lunar surface.

  8. Hardening treatment of friction surfaces of ball journal bearings

    NASA Astrophysics Data System (ADS)

    Gorlenko, A. O.; Davidov, S. V.

    2016-04-01

    The article presents the technology of finishing plasma hardening by the application of the multi-layer nanocoating Si-O-C-N system to harden the friction surfaces of the ball journal bearings. The authors of the paper have studied the applied wear-resistant anti-friction coating tribological characteristics, which determine the increase in wear resistance of the ball journal bearings.

  9. Radiation-Hardened Electronics for the Space Environment

    NASA Technical Reports Server (NTRS)

    Keys, Andrew S.; Watson, Michael D.

    2007-01-01

    RHESE covers a broad range of technology areas and products. - Radiation Hardened Electronics - High Performance Processing - Reconfigurable Computing - Radiation Environmental Effects Modeling - Low Temperature Radiation Hardened Electronics. RHESE has aligned with currently defined customer needs. RHESE is leveraging/advancing SOA space electronics, not duplicating. - Awareness of radiation-related activities through out government and industry allow advancement rather than duplication of capabilities.

  10. The Effects of Casting Porosity on the Tensile Behavior of Investment Cast 17-4PH Stainless Steel

    NASA Astrophysics Data System (ADS)

    Susan, D. F.; Crenshaw, T. B.; Gearhart, J. S.

    2015-08-01

    The effect of casting porosity on the mechanical behavior of investment cast 17-4PH stainless steel was studied as well as the effect of heat treatment on the alloy's sensitivity to casting defects. Interdendritic porosity, formed during solidification and shrinkage of the alloy, reduces the yield strength and ultimate tensile strength roughly in proportion to the reduction in load bearing cross-section. The effects of casting porosity on ductility (% strain, % reduction in area) are more severe, in agreement with research on other alloy systems. In this study, 10% porosity reduced the ductility of 17-4PH stainless steel by almost 80% for the high-strength H925 condition. Tensile testing at -10°C (263 K) further reduces the alloy ductility with and without pores present. In the lower strength H1100 condition, the ductility is higher than the H925 condition, as expected, and somewhat less sensitive to porosity. By measuring the area % porosity on the fracture surface of tensile specimens, the trend in failure strain versus area % porosity was obtained and analyzed using two methods: an empirical approach to determine an index of defect susceptibility with a logarithmic fit and an analytical approach based on the constitutive stress-strain behavior and critical strain concentration in the vicinity of the casting voids. The applicability of the second method depends on the amount of non-uniform strain (necking) and, as such, the softer H1100 material did not correlate well to the model. The behavior of 17-4PH was compared to previous work on cast Al alloys, Mg alloys, and other cast materials.

  11. Hardening anisotropy of {gamma}/{gamma}{prime} superalloy single crystals. 2: Numerical analysis of heterogeneity effects

    SciTech Connect

    Estevez, R.; Hoinard, G.; Franciosi, P.

    1997-04-01

    In the first part of this study, the {gamma}/{gamma}{prime} superalloy single crystals yield stress and hardening anisotropy were experimentally estimated at 650 C, assuming homogeneous plasticity, G. Hoinard, R. Estevez and P. Franciosi, Acta Metall. 43, 1593 (1995). Here alloy morphology is regarded in two different ways: first as a two-phase anisotropic material with a uniform {gamma} matrix, describing the {gamma}{prime} precipitates arrangement with the help of an elementary pattern of inclusions; then treating the {gamma} matrix as a three (geometrical) phase medium, i.e., the three families of orthogonal {gamma} layers separating the precipitates, to estimate the matrix behavior heterogeneity in a 4-phase modelling of the alloy. Both {gamma} and {gamma}{prime} phases are treated as elastic-plastic crystalline media deforming by octahedral and cubic slip, and the models are based on the self consistent approximation. The alloy elasticity limit, internal stresses and hardening anisotropy are discussed with regard to the chosen behavior description for each phase, and behavior simulations are compared to experimental information.

  12. New analytical approach for neutron beam-hardening correction.

    PubMed

    Hachouf, N; Kharfi, F; Hachouf, M; Boucenna, A

    2016-01-01

    In neutron imaging, the beam-hardening effect has a significant effect on quantitative and qualitative image interpretation. This study aims to propose a linearization method for beam-hardening correction. The proposed method is based on a new analytical approach establishing the attenuation coefficient as a function of neutron energy. Spectrum energy shift due to beam hardening is studied on the basis of Monte Carlo N-Particle (MCNP) simulated data and the analytical data. Good agreement between MCNP and analytical values has been found. Indeed, the beam-hardening effect is well supported in the proposed method. A correction procedure is developed to correct the errors of beam-hardening effect in neutron transmission, and therefore for projection data correction. The effectiveness of this procedure is determined by its application in correcting reconstructed images. PMID:26609685

  13. Hardening and yielding in colloidal gels

    NASA Astrophysics Data System (ADS)

    Del Gado, Emanuela; Colombo, Jader; Bouzid, Mehdi

    Attractive colloidal gel networks are disordered elastic solids that can form even in extremely dilute particle suspensions. With interaction strengths comparable to the thermal energy, their stress-bearing network can locally restructure via breaking and reforming inter-particle bonds. We use molecular dynamics simulations of a model system to investigate the strain hardening and the yielding process. During shear start up protocol, the system exhibits strong localization of tensile stresses that may be released through the breaking and formation of new bonds. In this regime, the small amplitude oscillatory shear analysis shows that the storage and the loss modulus follow a power law behavior that are closely reminiscent of experimental observations. At large accumulated strains, the strain-induced reorganization of the gel may trigger flow heterogeneities and eventually lead to the yielding of the gel via a quasi brittle damage of its structure.

  14. Keystroke Dynamics-Based Credential Hardening Systems

    NASA Astrophysics Data System (ADS)

    Bartlow, Nick; Cukic, Bojan

    abstract Keystroke dynamics are becoming a well-known method for strengthening username- and password-based credential sets. The familiarity and ease of use of these traditional authentication schemes combined with the increased trustworthiness associated with biometrics makes them prime candidates for application in many web-based scenarios. Our keystroke dynamics system uses Breiman’s random forests algorithm to classify keystroke input sequences as genuine or imposter. The system is capable of operating at various points on a traditional ROC curve depending on application-specific security needs. As a username/password authentication scheme, our approach decreases the system penetration rate associated with compromised passwords up to 99.15%. Beyond presenting results demonstrating the credential hardening effect of our scheme, we look into the notion that a user’s familiarity to components of a credential set can non-trivially impact error rates.

  15. Laser hardening process simulation for mechanical parts

    NASA Astrophysics Data System (ADS)

    Tani, G.; Orazi, L.; Fortunato, A.; Campana, G.; Cuccolini, G.

    2007-02-01

    In this paper a numerical simulation of laser hardening process is presented. The Finite Difference Method (FDM) was used to solve the heat transfer and the carbon diffusion equations for a defined workpiece geometry. The model is able to predict the thermal cycle into the target material, the phase transformations and the resulting micro-structures according to the laser parameters, the workpiece dimensions and the physical properties of the workpiece. The effects of the overlapping tracks of the laser beam on the resulting micro-structures is also considered. The initial workpiece micro-structure is taken into account in the simulation by a digitized photomicrograph of the ferrite perlite distribution before the thermal cycle. Experimental tests were realized on a C43 plate and the good agreement between the theoretical and experimental results is shown.

  16. Jerky loads on surface-hardened gears

    NASA Technical Reports Server (NTRS)

    Rettig, H.; Wirth, X.

    1978-01-01

    Damage occurs again and again in practice in the form of transmissions with surface hardened gears which break after a very long operating time (explained by seldom occurring jerky loads). Gear drives are frequently exposed to jerky stresses which are greater than their fatigue limit. These stresses are considered in gear calculations, first, by shock factors when the transmission is to be designed as high endurance with regard to overloads and, second, in the form of operating ratios when the design is to be time enduring with regard to overloads. The size of the operating ratio depends not only on torque characteristics, drive and processing machine, but also on the material and heat treatment.

  17. Dilatant hardening of fluid-saturated sandstone

    NASA Astrophysics Data System (ADS)

    Makhnenko, Roman Y.; Labuz, Joseph F.

    2015-02-01

    The presence of pore fluid in rock affects both the elastic and inelastic deformation processes, yet laboratory testing is typically performed on dry material even though in situ the rock is often saturated. Techniques were developed for testing fluid-saturated porous rock under the limiting conditions of drained, undrained, and unjacketed response. Confined compression experiments, both conventional triaxial and plane strain, were performed on water-saturated Berea sandstone to investigate poroelastic and inelastic behavior. Measured drained response was used to calibrate an elasto-plastic constitutive model that predicts undrained inelastic deformation. The experimental data show good agreement with the model: dilatant hardening in undrained triaxial and plane strain compression tests under constant mean stress was predicted and observed.

  18. Correlation of Fe/Cr phase decomposition process and age-hardening in Fe-15Cr ferritic alloys

    NASA Astrophysics Data System (ADS)

    Chen, Dongsheng; Kimura, Akihiko; Han, Wentuo

    2014-12-01

    The effects of thermal aging on the microstructure and mechanical properties of Fe-15Cr ferritic model alloys were investigated by TEM examinations, micro-hardness measurements and tensile tests. The materials used in this work were Fe-15Cr, Fe-15Cr-C and Fe-15Cr-X alloys, where X refers to Si, Mn and Ni to simulate a pressure vessel steel. Specimens were isothermally aged at 475 °C up to 5000 h. Thermal aging causes a significant increase in the hardness and strength. An almost twice larger hardening is required for embrittlement of Fe-15Cr-X relative to Fe-15Cr. The age-hardening is mainly due to the formation of Cr-rich α‧ precipitates, while the addition of minor elements has a small effect on the saturation level of age-hardening. The correlation of phase decomposition process and age-hardening in Fe-15Cr alloy was interpreted by dispersion strengthened models.

  19. Hardening by cooling rate control and post-firing heat treatment in Pd-Ag-Sn alloy for bonding porcelain.

    PubMed

    Yu, Young-Jun; Seol, Hyo-Joung; Cho, Mi-Hyang; Kim, Hyung-Il; Kwon, Yong Hoon

    2016-01-01

    The aim of this study was to determine the hardening effect by controlling the cooling rate during the porcelain firing process and performing an additional post-firing heat treatment in a Pd-Ag-Sn alloy. The most effective cooling rate for alloy hardening was determined by cooling the specimens at various cooling rates after oxidation treatment. A subsequent porcelain firing simulation followed by cooling at the selected cooling rate was performed. A post-firing heat treatment was then done at 600°C in a porcelain furnace. The hardening mechanism was characterized by a hardness test, X-ray diffraction, field emission scanning electron microscopy and energy dispersive X-ray spectroscopy. Alloy softening occurred during the porcelain firing process followed by cooling at a controlled cooling rate. A post-firing heat treatment allowed apparent precipitation hardening. It is advisable to perform a postfiring heat treatment at 600°C in a porcelain furnace by annealing metal substructure after porcelain fusing. PMID:27041022

  20. A microstructure-based yield stress and work-hardening model for textured 6xxx aluminium alloys

    NASA Astrophysics Data System (ADS)

    Khadyko, M.; Myhr, O. R.; Dumoulin, S.; Hopperstad, O. S.

    2016-04-01

    The plastic properties of an aluminium alloy are defined by its microstructure. The most important factors are the presence of alloying elements in the form of solid solution and precipitates of various sizes, and the crystallographic texture. A nanoscale model that predicts the work-hardening curves of 6xxx aluminium alloys was proposed by Myhr et al. The model predicts the solid solution concentration and the particle size distributions of different types of metastable precipitates from the chemical composition and thermal history of the alloy. The yield stress and the work hardening of the alloy are then determined from dislocation mechanics. The model was largely used for non-textured materials in previous studies. In this work, a crystal plasticity-based approach is proposed for the work hardening part of the nanoscale model, which allows including the influence of the crystallographic texture. The model is evaluated by comparison with experimental data from uniaxial tensile tests on two textured 6xxx alloys in five temper conditions.

  1. Properties of modified anhydride hardener and its cured resin

    NASA Astrophysics Data System (ADS)

    Qiang, Chen; Bingjun, Gao; Jinglin, Chen; Tongzhao, Xu

    2000-01-01

    Methyl-nadic-tetrahydric-methylanhydride (MNA), nadic-tetrahydric-methylanhydride (NA), anhydride hardener was modified by solid diol molecule to improve the impregnation resin fracture toughness in cryogenic temperature. The lap-shear strength, transverse tension as well as the thermal shock test showed that the resin cured by the modified anhydride hardener had higher bond strength and more toughness at 77 K. After the experiment of vacuum pressure impregnation (VPI) processing, it was found that this resin had a longer usable life, better impregnating properties, but higher initial viscosity than the resin hybrid HY925 as hardener.

  2. Strain hardening of metal parts with use of impulse wave

    NASA Astrophysics Data System (ADS)

    Kirichek, A. V.; Soloviev, D. L.

    2016-04-01

    This work describes a strain hardening method with the use of impulse waves. This method increases energy transfer to the strained material extending its technological capabilities with development of a deep strengthened layer and allowing formation of a heterogeneous hardened structure using plastic deformation. This structure has specified distribution of the hard and soft (visco-plastic) areas. Due to development of the heterogeneous structure in the surface layer created by strain hardening with impulse wave, durability of parts that suffer contact fatigue loading is significantly increased.

  3. Observational Evidences for the Existence of 17.4 keV Decaying Degenerate Sterile Neutrinos Near the Galactic Center

    NASA Astrophysics Data System (ADS)

    Chan, M. H.; Chu, M.-C.

    2011-02-01

    We show that the existence of a degenerate halo of sterile neutrinos with rest mass of 17.4 keV near the Galactic center (GC) can account for both the excess 8.7 keV emission observed by the Suzaku mission and the power needed (1040 erg s-1) to maintain the high temperature of the hot gas (8 keV) near the GC. The required decay rate and mixing angle of the sterile neutrinos are Γ >= 10-19 s-1 and sin22θ ~ 10-3, respectively. These values are consistent with a low reheating temperature, which suppresses the production of sterile neutrinos, resulting in a small sterile neutrino density parameter (Ω s < 10-8). They are also allowed by X-ray background data and the isotope experiment. The large mixing angle leads to the exciting possibility that a sterile-active neutrino oscillation may be visible in near future experiments.

  4. Beam Hardening Corrections in Quantitative Computed Tomography

    SciTech Connect

    Vedula, Venumadhav; Venugopal, Manoharan; Raghu, C.; Pandey, Pramod

    2007-03-21

    Volumetric computed tomography (VCT) is the emerging 3D NDE inspection technique that gives highest throughput and better image quality. Industrial components in general demands higher x-ray energy for inspection for which polychromatic x-ray sources are used in common. Polychromatic nature of the x-rays gives rise to non-linear effects in the VCT projection data measurements called to be the beam hardening (BH) effects. BH produces prominent artifacts in the reconstructed images thereby deteriorating the image quality. Quantitative analysis such as density quantification, dimensional analysis etc., becomes difficult with the presence of these artifacts. This paper describes the BH correction using preprocessing technique for the homogeneous materials. Selection of effective energy at which the monoenergetic linear attenuation coefficient of a particular material equals to that of the polyenergetic beam is critical for BH correction. Various methods to determine the effective energy and their consequence in the quantitative measurements have been investigated in the present study. In this paper, BH corrections for heterogeneous materials have also been explored.

  5. Design concepts for hardened communications structures

    NASA Astrophysics Data System (ADS)

    Flathau, William J.; Smith, William G.

    1990-03-01

    An important component of any hardened command and control structure is the antenna system that provides communication with the outside world. Two types of antennae were considered; i.e., the whip type and the directional. The whip type is for short range communication and the directional is for use primarily with satellites. In the super high frequency range, the use of directional antennae having parabolic dishes greater than 8 feet in diameter are common. In the very extra high frequency range, dishes that are 2 to 3 feet in diameter are used. The whip type antenna should extend up to, say, 60 feet in the air. Based on this background, a family of structures was designed that can protect whip and directional antennae from the blast and shock effects from a 1-MT device for ground surface overpressure ranging from 15,000 to 500 psi. As the antennae, transmitters, receivers, power supplies, and lifting mechanisms will be located within such structures, appropriate shock spectra plots were developed to determine if the fragility level of pertinent equipment will be exceeded and for use in designing shock isolation systems. Button up periods of 1 and 4 weeks were considered.

  6. Weldable, age hardenable, austenitic stainless steel

    DOEpatents

    Brooks, J.A.; Krenzer, R.W.

    1975-07-22

    An age hardenable, austenitic stainless steel having superior weldability properties as well as resistance to degradation of properties in a hydrogen atmosphere is described. It has a composition of from about 24.0 to about 34.0 weight percent (w/o) nickel, from about 13.5 to about 16.0 w/o chromium, from about 1.9 to about 2.3 w/o titanium, from about 1.0 to about 1.5 w/ o molybdenum, from about 0.01 to about 0.05 w/o carbon, from about 0 to about 0.25 w/o manganese, from about 0 to about 0.01 w/o phosphorous and preferably about 0.005 w/o maximum, from about 0 to about 0.010 w/o sulfur and preferably about 0.005 w/o maximum, from about 0 to about 0.25 w/o silicon, from about 0.1 to about 0.35 w/o aluminum, from about 0.10 to about 0.50 w/o vanadium, from about 0 to about 0.0015 w/o boron, and the balance essentially iron. (auth)

  7. Cyber situational awareness and differential hardening

    NASA Astrophysics Data System (ADS)

    Dwivedi, Anurag; Tebben, Dan

    2012-06-01

    The advent of cyber threats has created a need for a new network planning, design, architecture, operations, control, situational awareness, management, and maintenance paradigms. Primary considerations include the ability to assess cyber attack resiliency of the network, and rapidly detect, isolate, and operate during deliberate simultaneous attacks against the network nodes and links. Legacy network planning relied on automatic protection of a network in the event of a single fault or a very few simultaneous faults in mesh networks, but in the future it must be augmented to include improved network resiliency and vulnerability awareness to cyber attacks. Ability to design a resilient network requires the development of methods to define, and quantify the network resiliency to attacks, and to be able to develop new optimization strategies for maintaining operations in the midst of these newly emerging cyber threats. Ways to quantify resiliency, and its use in visualizing cyber vulnerability awareness and in identifying node or link criticality, are presented in the current work, as well as a methodology of differential network hardening based on the criticality profile of cyber network components.

  8. A STUDY OF PRECIPITATION IN INTERSTITIAL ALLOYS. I. PRECIPITATION SEQUENCE IN Ta-C ALLOYS

    SciTech Connect

    Dahmen, U.; Westmacott, K.H.; Thomas, G.

    1980-08-01

    A systematic transmission electron microscopy study of carbide precipitation in quenched-aged tantalum-carbon alloys has clarified the mechanism of precipitation in refractory BCC metal-carbon alloys. Diffraction contrast analysis shows that the precipitate platelets lie on {l_brace}310{r_brace} planes of the matrix, are interstitial in nature, and fully coherent before they thicken further and lose coherency. The precipitation sequence is continuous and involves no renucleation during the formation of the non-coherent phase. Thus, the final orientation relationship of the precipitate with the matrix already is found at the earliest stage at which it is possible to detect it. The interpretation of the results indicates that, as in FCC alloys, vacancies play an important role in the precipitation process during the nucleation and early growth stages and permit the formation of the hexagonal equilibrium M{sub 2}C structure early in the sequence. The model proposed to explain the observations is also consistent with the multistage hardening observed in quenched-aged refractory metal interstitial alloys.

  9. Microscopic Origin of Strain Hardening in Methane Hydrate

    PubMed Central

    Jia, Jihui; Liang, Yunfeng; Tsuji, Takeshi; Murata, Sumihiko; Matsuoka, Toshifumi

    2016-01-01

    It has been reported for a long time that methane hydrate presents strain hardening, whereas the strength of normal ice weakens with increasing strain after an ultimate strength. However, the microscopic origin of these differences is not known. Here, we investigated the mechanical characteristics of methane hydrate and normal ice by compressive deformation test using molecular dynamics simulations. It is shown that methane hydrate exhibits strain hardening only if the hydrate is confined to a certain finite cross-sectional area that is normal to the compression direction. For normal ice, it does not present strain hardening under the same conditions. We show that hydrate guest methane molecules exhibit no long-distance diffusion when confined to a finite-size area. They appear to serve as non-deformable units that prevent hydrate structure failure, and thus are responsible for the strain-hardening phenomenon. PMID:27009239

  10. Possible correlation between work-hardening and fatigue-failure

    NASA Technical Reports Server (NTRS)

    Kettunen, P. O.; Kocks, U. F.

    1969-01-01

    Conceptual theory proposes that cyclic hardening due to non-uniform strain and stress amplitudes during testing, especially during the initial application of stress to a specimen, may correlate positively with the ultimate strength of the specimen under test.

  11. Microscopic Origin of Strain Hardening in Methane Hydrate.

    PubMed

    Jia, Jihui; Liang, Yunfeng; Tsuji, Takeshi; Murata, Sumihiko; Matsuoka, Toshifumi

    2016-01-01

    It has been reported for a long time that methane hydrate presents strain hardening, whereas the strength of normal ice weakens with increasing strain after an ultimate strength. However, the microscopic origin of these differences is not known. Here, we investigated the mechanical characteristics of methane hydrate and normal ice by compressive deformation test using molecular dynamics simulations. It is shown that methane hydrate exhibits strain hardening only if the hydrate is confined to a certain finite cross-sectional area that is normal to the compression direction. For normal ice, it does not present strain hardening under the same conditions. We show that hydrate guest methane molecules exhibit no long-distance diffusion when confined to a finite-size area. They appear to serve as non-deformable units that prevent hydrate structure failure, and thus are responsible for the strain-hardening phenomenon. PMID:27009239

  12. Ultimate bending capacity of strain hardening steel pipes

    NASA Astrophysics Data System (ADS)

    Chen, Yan-fei; Zhang, Juan; Zhang, Hong; Li, Xin; Zhou, Jing; Cao, Jing

    2016-04-01

    Based on Hencky's total strain theory of plasticity, ultimate bending capacity of steel pipes can be determined analytically assuming an elastic-linear strain hardening material, the simplified analytical solution is proposed as well. Good agreement is observed when ultimate bending capacities obtained from analytical solutions are compared with experimental results from full-size tests of steel pipes. Parametric study conducted as part of this paper indicates that the strain hardening effect has significant influence on the ultimate bending capacity of steel pipes. It is shown that pipe considering strain hardening yields higher bending capacity than that of pipe assumed as elastic-perfectly plastic material. Thus, the ignorance of strain hardening effect, as commonly assumed in current codes, may underestimate the ultimate bending capacity of steel pipes. The solutions proposed in this paper are applicable in the design of offshore/onshore steel pipes, supports of offshore platforms and other tubular structural steel members.

  13. Computed tomographic beam-hardening artefacts: mathematical characterization and analysis

    PubMed Central

    Park, Hyoung Suk; Chung, Yong Eun; Seo, Jin Keun

    2015-01-01

    This paper presents a mathematical characterization and analysis of beam-hardening artefacts in X-ray computed tomography (CT). In the field of dental and medical radiography, metal artefact reduction in CT is becoming increasingly important as artificial prostheses and metallic implants become more widespread in ageing populations. Metal artefacts are mainly caused by the beam-hardening of polychromatic X-ray photon beams, which causes mismatch between the actual sinogram data and the data model being the Radon transform of the unknown attenuation distribution in the CT reconstruction algorithm. We investigate the beam-hardening factor through a mathematical analysis of the discrepancy between the data and the Radon transform of the attenuation distribution at a fixed energy level. Separation of cupping artefacts from beam-hardening artefacts allows causes and effects of streaking artefacts to be analysed. Various computer simulations and experiments are performed to support our mathematical analysis. PMID:25939628

  14. Computed tomographic beam-hardening artefacts: mathematical characterization and analysis.

    PubMed

    Park, Hyoung Suk; Chung, Yong Eun; Seo, Jin Keun

    2015-06-13

    This paper presents a mathematical characterization and analysis of beam-hardening artefacts in X-ray computed tomography (CT). In the field of dental and medical radiography, metal artefact reduction in CT is becoming increasingly important as artificial prostheses and metallic implants become more widespread in ageing populations. Metal artefacts are mainly caused by the beam-hardening of polychromatic X-ray photon beams, which causes mismatch between the actual sinogram data and the data model being the Radon transform of the unknown attenuation distribution in the CT reconstruction algorithm. We investigate the beam-hardening factor through a mathematical analysis of the discrepancy between the data and the Radon transform of the attenuation distribution at a fixed energy level. Separation of cupping artefacts from beam-hardening artefacts allows causes and effects of streaking artefacts to be analysed. Various computer simulations and experiments are performed to support our mathematical analysis. PMID:25939628

  15. Quantitative TEM analysis of precipitation and grain boundary segregation in neutron irradiated EUROFER 97

    NASA Astrophysics Data System (ADS)

    Dethloff, Christian; Gaganidze, Ermile; Aktaa, Jarir

    2014-11-01

    Characterization of irradiation induced microstructural defects is essential for assessing the applicability of structural steels like the Reduced Activation Ferritic/Martensitic steel EUROFER 97 in upcoming fusion reactors. In this work Transmission Electron Microscopy (TEM) is used to analyze the types and structure of precipitates, and the evolution of their size distributions and densities caused by neutron irradiation to a dose of 32 displacements per atom (dpa) at 330-340 °C in the irradiation experiment ARBOR 1. A significant growth of MX and M23C6 type precipitates is observed after neutron irradiation, while the precipitate density remains unchanged. Hardening caused by MX and M23C6 precipitate growth is assessed by applying the Dispersed Barrier Hardening (DBH) model, and shown to be of minor importance when compared to other irradiation effects like dislocation loop formation. Additionally, grain boundary segregation of chromium induced by neutron irradiation was investigated and detected in irradiated specimens.

  16. Strain hardening of fcc metal surfaces induced by microploughing

    SciTech Connect

    Day, R.D.; Dickerson, R.M.; Russell, P.E.

    1998-12-01

    Microploughing experiments were used as a method for better understanding the ploughing mechanism in gold and iridium single crystals. The plough depths ranged from 20 nm in iridium to 1,600 nm in gold. Yield stress profiles and TEM analyses indicate that both materials strain harden even when very small volumes of material are involved. Strain hardening theory, as applied to bulk material, is useful in analyzing the results.

  17. Fine precipitation scenarios of AlZnMg(Cu) alloys revealed by advanced atomic-resolution electron microscopy study Part I: Structure determination of the precipitates in AlZnMg(Cu) alloys

    SciTech Connect

    Liu, J.Z.; Chen, J.H.; Yuan, D.W.; Wu, C.L.; Zhu, J.; Cheng, Z.Y.

    2015-01-15

    Although they are among the most important precipitation-hardened materials for industry applications, the high-strength AlZnMg(Cu) alloys have thus far not yet been understood adequately about their underlying precipitation scenarios in relation with the properties. This is partly due to the fact that the structures of a number of different precipitates involved in electron microscopy in association with quantitative image simulations have to be employed; a systematic study of these hardening precipitates in different alloys is also necessary. In Part I of the present study, it is shown that there are five types of structurally different precipitates including the equilibrium η-phase precipitate. Using two state-of-the-art atomic-resolution imaging techniques in electron microscopy in association with quantitative image simulations, we have determined and clarified all the unknown precipitate structures. It is demonstrated that atomic-resolution imaging can directly suggest approximate structure models, whereas quantitative image analysis can refine the structure details that are much smaller than the resolution of the microscope. This combination is crucially important for solving the difficult structure problems of the strengthening precipitates in AlZnMg(Cu) alloys. - Highlights: Part I: • We determine and verify all the key precipitate structures in AlMgZn(Cu) alloys. • We employ aberration-corrected scanning transmission electron microscopy (STEM). • We use aberration-corrected high-resolution TEM (HRTEM) for the investigations. • We obtain atomic-resolution images of the precipitates and model their structures. • We refine all precipitate structures with quantitative image simulation analysis. Part II: • The hardening precipitates in AlZnMg alloys shall be classified into two groups. • Two precipitation scenarios coexist in the alloys. • The precipitation behavior of such an alloy depends on the alloy's composition. • Very detailed phase

  18. Crystallography of Fatigue Crack Propagation in Precipitation-Hardened Al-Cu-Mg/Li

    NASA Astrophysics Data System (ADS)

    Ro, Yunjo; Agnew, Sean R.; Gangloff, Richard P.

    2007-12-01

    A combined electron backscatter diffraction (EBSD)/stereology method successfully quantifies the orientation of fatigue crack surfaces for Al-Li-Cu and Al-Cu-Mg alloys stressed at low Δ K, in which deformation is localized in slip bands and cracking is highly faceted. The method orients features as small as ˜1 μm in complex microstructures. Vacuum fatigue facets align within 15 deg of up to four variants of {111} slip planes, governed by the distribution of crack tip resolved shear stress. The small fraction of precisely oriented {111} facets suggests that cracking involves complex intraband and multiple-band interface paths. Water vapor and NaCl solution affect a similar dramatic change in the crack path; near-{111} facets are never observed, at odds with mechanisms for H-enhanced slip localization and associated slip band cracking. Rather, two environmental crack facet morphologies, broad flat and repeating step, exhibit a wide range of orientations between {001} and {110}, as governed by crack tip resolved normal stresses. The repetitive stepped facets appear to contain areas parallel to {100}/{110} on the ˜1- μm scale, coupled with surface curvature consistent with a mechanism of discontinuous fatigue crack growth involving H-enhanced {100}/{110} cleavage and intermingled crack tip plasticity. Broad-flat faceted regions are parallel to a variety of planes, consistent with a mechanism combining high crack tip tensile stresses and H trapped at the dislocation structure from cyclic deformation, within 1 μm of the crack tip.

  19. Precipitation-hardening stainless steels with a shape-memory effect

    NASA Astrophysics Data System (ADS)

    Sagaradze, V. V.; Afanasiev, S. V.; Volkova, E. G.; Zavalishin, V. A.

    2016-02-01

    The possibility of obtaining the shape-memory effect as a result of the γ → ɛ → γ transformations in aging stainless steels strengthened by VC carbides has been investigated. Regimes are given for strengthening aging (at 650 and 720°C) for stainless steels that predominantly contain (in wt %) 0.06-0.45C, 1-2V, 2-5Si, 9 and 13-14Cr. The values of reversible deformation e (amount of shape-memory effect) determined after heating to 400°C in samples preliminarily deformed to 3.5-4% vary from 0.15 to 2.7%, depending on the composition of the steels and regimes of stabilizing and destabilizing aging.

  20. Mechanical behavior of precipitation hardenable steels exposed to highly corrosive environment

    NASA Technical Reports Server (NTRS)

    Rosa, Ferdinand

    1994-01-01

    Unexpected occurrences of failures, due to stress corrosion cracking (SCC) of structural components, indicate a need for improved characterization of materials and more advanced analytical procedures for reliably predicting structures performance. Accordingly, the purpose of this study was to determine the stress corrosion susceptibility of 15 - 5 PH steel over a wide range of applied strain rates in a highly corrosive environment. The selected environment for this investigation was a 3.5 percent NaCl aqueous solution. The material selected for the study was 15 - 5 PH steel in the H 900 condition. The Slow Strain Rate technique was used to test the metallic specimens.

  1. Zinc coated sheet steel for press hardening

    NASA Astrophysics Data System (ADS)

    Ghanbari, Zahra N.

    Galvanized steels are of interest to enhance corrosion resistance of press-hardened steels, but concerns related to liquid metal embrittlement have been raised. The objective of this study was to assess the soak time and temperature conditions relevant to the hot-stamping process during which Zn penetration did or did not occur in galvanized 22MnB5 press-hardening steel. A GleebleRTM 3500 was used to heat treat samples using hold times and temperatures similar to those used in industrial hot-stamping. Deformation at both elevated temperature and room temperature were conducted to assess the coating and substrate behavior related to forming (at high temperature) and service (at room temperature). The extent of alloying between the coating and substrate was assessed on undeformed samples heat treated under similar conditions to the deformed samples. The coating transitioned from an α + Gamma1 composition to an α (bcc Fe-Zn) phase with increased soak time. This transition likely corresponded to a decrease in availability of Zn-rich liquid in the coating during elevated temperature deformation. Penetration of Zn into the substrate sheet in the undeformed condition was not observed for any of the processing conditions examined. The number and depth of cracks in the coating and substrate steel was also measured in the hot-ductility samples. The number of cracks appeared to increase, while the depth of cracks appeared to decrease, with increasing soak time and increasing soak temperature. The crack depth appeared to be minimized in the sample soaked at the highest soak temperature (900 °C) for intermediate and extended soak times (300 s or 600 s). Zn penetration into the substrate steel was observed in the hot-ductility samples soaked at each hold temperature for the shortest soak time (10 s) before being deformed at elevated temperature. Reduction of area and elongation measurements showed that the coated sample soaked at the highest temperature and longest soak time

  2. High post-irradiation ductility thermomechanical treatment for precipitation strengthened austenitic alloys

    DOEpatents

    Laidler, James J.; Borisch, Ronald R.; Korenko, Michael K.

    1982-01-01

    A method for improving the post-irradiation ductility is described which prises a solution heat treatment following which the materials are cold worked. They are included to demonstrate the beneficial effect of this treatment on the swelling resistance and the ductility of these austenitic precipitation hardenable alloys.

  3. Extracting material response from simple mechanical tests on hardening-softening-hardening viscoplastic solids

    NASA Astrophysics Data System (ADS)

    Mohan, Nisha

    Compliant foams are usually characterized by a wide range of desirable mechanical properties. These properties include viscoelasticity at different temperatures, energy absorption, recoverability under cyclic loading, impact resistance, and thermal, electrical, acoustic and radiation-resistance. Some foams contain nano-sized features and are used in small-scale devices. This implies that the characteristic dimensions of foams span multiple length scales, rendering modeling their mechanical properties difficult. Continuum mechanics-based models capture some salient experimental features like the linear elastic regime, followed by non-linear plateau stress regime. However, they lack mesostructural physical details. This makes them incapable of accurately predicting local peaks in stress and strain distributions, which significantly affect the deformation paths. Atomistic methods are capable of capturing the physical origins of deformation at smaller scales, but suffer from impractical computational intensity. Capturing deformation at the so-called meso-scale, which is capable of describing the phenomenon at a continuum level, but with some physical insights, requires developing new theoretical approaches. A fundamental question that motivates the modeling of foams is `how to extract the intrinsic material response from simple mechanical test data, such as stress vs. strain response?' A 3D model was developed to simulate the mechanical response of foam-type materials. The novelty of this model includes unique features such as the hardening-softening-hardening material response, strain rate-dependence, and plastically compressible solids with plastic non-normality. Suggestive links from atomistic simulations of foams were borrowed to formulate a physically informed hardening material input function. Motivated by a model that qualitatively captured the response of foam-type vertically aligned carbon nanotube (VACNT) pillars under uniaxial compression [2011,"Analysis of

  4. PRECIPITATION OF PLUTONOUS PEROXIDE

    DOEpatents

    Barrick, J.G.; Manion, J.P.

    1961-08-15

    A precipitation process for recovering plutonium values contained in an aqueous solution is described. In the process for precipitating plutonium as plutonous peroxide, hydroxylamine or hydrazine is added to the plutoniumcontaining solution prior to the addition of peroxide to precipitate plutonium. The addition of hydroxylamine or hydrazine increases the amount of plutonium precipitated as plutonous peroxide. (AEC)

  5. High-Performance, Radiation-Hardened Electronics for Space Environments

    NASA Technical Reports Server (NTRS)

    Keys, Andrew S.; Watson, Michael D.; Frazier, Donald O.; Adams, James H.; Johnson, Michael A.; Kolawa, Elizabeth A.

    2007-01-01

    The Radiation Hardened Electronics for Space Environments (RHESE) project endeavors to advance the current state-of-the-art in high-performance, radiation-hardened electronics and processors, ensuring successful performance of space systems required to operate within extreme radiation and temperature environments. Because RHESE is a project within the Exploration Technology Development Program (ETDP), RHESE's primary customers will be the human and robotic missions being developed by NASA's Exploration Systems Mission Directorate (ESMD) in partial fulfillment of the Vision for Space Exploration. Benefits are also anticipated for NASA's science missions to planetary and deep-space destinations. As a technology development effort, RHESE provides a broad-scoped, full spectrum of approaches to environmentally harden space electronics, including new materials, advanced design processes, reconfigurable hardware techniques, and software modeling of the radiation environment. The RHESE sub-project tasks are: SelfReconfigurable Electronics for Extreme Environments, Radiation Effects Predictive Modeling, Radiation Hardened Memory, Single Event Effects (SEE) Immune Reconfigurable Field Programmable Gate Array (FPGA) (SIRF), Radiation Hardening by Software, Radiation Hardened High Performance Processors (HPP), Reconfigurable Computing, Low Temperature Tolerant MEMS by Design, and Silicon-Germanium (SiGe) Integrated Electronics for Extreme Environments. These nine sub-project tasks are managed by technical leads as located across five different NASA field centers, including Ames Research Center, Goddard Space Flight Center, the Jet Propulsion Laboratory, Langley Research Center, and Marshall Space Flight Center. The overall RHESE integrated project management responsibility resides with NASA's Marshall Space Flight Center (MSFC). Initial technology development emphasis within RHESE focuses on the hardening of Field Programmable Gate Arrays (FPGA)s and Field Programmable Analog

  6. Property investigation and sputter deposition of dispersion-hardened copper for fatigue specimen fabrication

    NASA Technical Reports Server (NTRS)

    Mcclanahan, E. D.; Busch, R.; Moss, R. W.

    1973-01-01

    Sputter-deposited alloys of dispersion-hardenable Cu-0.25 vol% SiC and Cu-0.50 vol% SiC and precipitation-hardenable Cu-0.15 wt% Zr and Cu-0.05 wt% Mg-0.15 wt% Zr-0.40 wt% Cr were investigated for selection to evaluate fatigue specimen performance with potential application in fabricating regeneratively cooled rocket thrust chambers. Yield strengths in the 700 to 1000-MN/sq m range were observed with uniform elongation ranging from 0.5 to 1.5% and necking indicative of greater ductility. Electrical conductivity measured as an analog to thermal conductivity gave values 90% IACS for Cu-0.15 wt% Zr and Cu-0.05 wt% Mg-0.15 wt% Zr-0.40 wt% Cr. A 5500-g sputtered deposit of Cu-0.15 wt% Zr alloy, 12.29 mm (0.484 in.) average thickness in the fatigue specimen gage length, was provided to NASA on one of their substrates.

  7. Precipitation under cyclic strain in solution-treated Al4wt%Cu I: mechanical behavior

    SciTech Connect

    Farrow, Adam M; Laird, Campbell

    2008-01-01

    Solution-treated AL-4wt%Cu was strain-cycled at ambient temperature and above, and the precipitation and deformation behaviors investigated by TEM. Anomalously rapid growth of precipitates appears to have been facilitated by a vacancy super-saturation generated by cyclic strain and the presence of a continually refreshed dislocation density to provide heterogeneous nucleation sites. Texture effects as characterized by Orientation Imaging Microscopy appear to be responsible for latent hardening in specimens tested at room temperature, with increasing temperatures leading to a gradual hardening throughout life due to precipitation. Specimens exhibiting rapid precipitation hardening appear to show a greater effect of texture due to the increased stress required to cut precipitates in specimens machined from rolled plate at an angle corresponding to a lower average Schmid factor. The accelerated formation of grain boundary precipitates appears to be partially responsible for rapid inter-granular fatigue failure at elevated temperatures, producing fatigue striations and ductile dimples coexistent on the fracture surface.

  8. Process design of press hardening with gradient material property influence

    SciTech Connect

    Neugebauer, R.; Schieck, F.; Rautenstrauch, A.

    2011-05-04

    Press hardening is currently used in the production of automotive structures that require very high strength and controlled deformation during crash tests. Press hardening can achieve significant reductions of sheet thickness at constant strength and is therefore a promising technology for the production of lightweight and energy-efficient automobiles. The manganese-boron steel 22MnB5 have been implemented in sheet press hardening owing to their excellent hot formability, high hardenability, and good temperability even at low cooling rates. However, press-hardened components have shown poor ductility and cracking at relatively small strains. A possible solution to this problem is a selective increase of steel sheet ductility by press hardening process design in areas where the component is required to deform plastically during crash tests. To this end, process designers require information about microstructure and mechanical properties as a function of the wide spectrum of cooling rates and sequences and austenitizing treatment conditions that can be encountered in production environments. In the present work, a Continuous Cooling Transformation (CCT) diagram with corresponding material properties of sheet steel 22MnB5 was determined for a wide spectrum of cooling rates. Heating and cooling programs were conducted in a quenching dilatometer. Motivated by the importance of residual elasticity in crash test performance, this property was measured using a micro-bending test and the results were integrated into the CCT diagrams to complement the hardness testing results. This information is essential for the process design of press hardening of sheet components with gradient material properties.

  9. Process design of press hardening with gradient material property influence

    NASA Astrophysics Data System (ADS)

    Neugebauer, R.; Schieck, F.; Rautenstrauch, A.

    2011-05-01

    Press hardening is currently used in the production of automotive structures that require very high strength and controlled deformation during crash tests. Press hardening can achieve significant reductions of sheet thickness at constant strength and is therefore a promising technology for the production of lightweight and energy-efficient automobiles. The manganese-boron steel 22MnB5 have been implemented in sheet press hardening owing to their excellent hot formability, high hardenability, and good temperability even at low cooling rates. However, press-hardened components have shown poor ductility and cracking at relatively small strains. A possible solution to this problem is a selective increase of steel sheet ductility by press hardening process design in areas where the component is required to deform plastically during crash tests. To this end, process designers require information about microstructure and mechanical properties as a function of the wide spectrum of cooling rates and sequences and austenitizing treatment conditions that can be encountered in production environments. In the present work, a Continuous Cooling Transformation (CCT) diagram with corresponding material properties of sheet steel 22MnB5 was determined for a wide spectrum of cooling rates. Heating and cooling programs were conducted in a quenching dilatometer. Motivated by the importance of residual elasticity in crash test performance, this property was measured using a micro-bending test and the results were integrated into the CCT diagrams to complement the hardness testing results. This information is essential for the process design of press hardening of sheet components with gradient material properties.

  10. OBSERVATIONAL EVIDENCES FOR THE EXISTENCE OF 17.4 keV DECAYING DEGENERATE STERILE NEUTRINOS NEAR THE GALACTIC CENTER

    SciTech Connect

    Chan, M. H.; Chu, M.-C. E-mail: mcchu@phy.cuhk.edu.h

    2011-02-01

    We show that the existence of a degenerate halo of sterile neutrinos with rest mass of 17.4 keV near the Galactic center (GC) can account for both the excess 8.7 keV emission observed by the Suzaku mission and the power needed (10{sup 40} erg s{sup -1}) to maintain the high temperature of the hot gas (8 keV) near the GC. The required decay rate and mixing angle of the sterile neutrinos are {Gamma} {>=} 10{sup -19} s{sup -1} and sin{sup 2}2{theta} {approx} 10{sup -3}, respectively. These values are consistent with a low reheating temperature, which suppresses the production of sterile neutrinos, resulting in a small sterile neutrino density parameter ({Omega}{sub s} < 10{sup -8}). They are also allowed by X-ray background data and the isotope experiment. The large mixing angle leads to the exciting possibility that a sterile-active neutrino oscillation may be visible in near future experiments.

  11. Influence of Heat Treatment on Mercury Cavitation Resistance of Surface Hardened 316LN Stainless Steel

    SciTech Connect

    Pawel, Steven J; Hsu, Julia

    2010-11-01

    The cavitation-erosion resistance of carburized 316LN stainless steel was significantly degraded but not destroyed by heat treatment in the temperature range 500-800 C. The heat treatments caused rejection of some carbon from the carburized layer into an amorphous film that formed on each specimen surface. Further, the heat treatments encouraged carbide precipitation and reduced hardness within the carburized layer, but the overall change did not reduce surface hardness fully to the level of untreated material. Heat treatments as short as 10 min at 650 C substantially reduced cavitation-erosion resistance in mercury, while heat treatments at 500 and 800 C were found to be somewhat less detrimental. Overall, the results suggest that modest thermal excursions perhaps the result of a weld made at some distance to the carburized material or a brief stress relief treatment will not render the hardened layer completely ineffective but should be avoided to the greatest extent possible.

  12. Low beryllium content Zr-based bulk metallic glass composite with plasticity and work hardenability

    SciTech Connect

    Zheng, Q. E-mail: dujuan@nimte.ac.cn; Du, J. E-mail: dujuan@nimte.ac.cn

    2014-01-28

    A modified Zr-based bulk metallic glass matrix composite Zr{sub 47.67}Cu{sub 40}Ti{sub 3.66}Ni{sub 2.66}Be{sub 6} has been produced by increasing the contents of elements of Zr and Cu with higher Poisson ratio and reducing the contents of Ti, Ni, and Be elements with lower Poisson ratio based on famous metallic glass former Vitreloy 1. A compressive yielding strength of 1804 MPa, fracture strength of 1938 MPa and 3.5% plastic strain was obtained for obtained metallic glass composite. Also, work-hardening behavior was observed during compressive experiment which was ascribed to the interaction of the in situ precipitated CuZr phase and shear bands.

  13. Effects of age hardening on magnetic and transport properties of Mg-1.3 wt% Ce alloys

    SciTech Connect

    Yamashita, T.; Cavallaro, P.; Kelly, P.M.; Hisa, M.

    1998-05-22

    Magnesium is the lightest structural metal. It has advantages over many other materials in terms of specific strength, machinability and shock absorption. Improvements in magnesium alloy design and more stringent requirements to reduce fuel consumption and air pollution, have recently focused attention on the use of magnesium alloys for automotive components. Here, a Mg-1.3 wt% Ce alloy has been isothermally heat treated at 423 K and the transport and magnetic properties are investigated. This alloy is known to have distinct age hardening behavior and its age hardened microstructure has been studied in detail. The transport properties depend on the early stage of precipitation which is difficult to define by transmission electron microscopy. The scattering sites of electrons are not identical to precipitates, but consist of strain fields induced by the precipitates, solute atoms, dislocations and vacancies. The resistivity was found to increase initially with aging time and then decrease. The highest resistivity was obtained from a specimen aged for 3.6 ks. This aging time is far less than that of 1,800 ks which gives the maximum hardness. On the other hand, magnetic properties correlate with the later stages of the precipitation. In particular, the imaginary part of the magnetic susceptibility is related to macroscopic formation of precipitates. The imaginary part of the magnetic susceptibility of the alloys seems to be generated by eddy current loss. The imaginary part of the magnetic susceptibility increases monotonically with aging time but it may decrease for extensive aging treatments beyond 3,600 ks.

  14. Anisotropic hardening model based on non-associated flow rule and combined nonlinear kinematic hardening for sheet materials

    NASA Astrophysics Data System (ADS)

    Taherizadeh, Aboozar; Green, Daniel E.; Yoon, Jeong W.

    2013-12-01

    A material model for more effective analysis of plastic deformation of sheet materials is presented in this paper. The model is capable of considering the following aspects of plastic deformation behavior of sheet materials: the anisotropy in yielding stresses in different directions by using a quadratic yield function (based on Hill's 1948 model and stress ratios), the anisotropy in work hardening by introducing non-constant flow stress hardening in different directions, the anisotropy in plastic strains in different directions by using a quadratic plastic potential function and non-associated flow rule (based on Hill's 1948 model and plastic strain ratios, r-values), and finally some of the cyclic hardening phenomena such as Bauschinger's effect and transient behavior for reverse loading by using a coupled nonlinear kinematic hardening (so-called Armstrong-Frederick-Chaboche model). Basic fundamentals of the plasticity of the model are presented in a general framework. Then, the model adjustment procedure is derived for the plasticity formulations. Also, a generic numerical stress integration procedure is developed based on backward-Euler method (so-called multi-stage return mapping algorithm). Different aspects of the model are verified for DP600 steel sheet. Results show that the new model is able to predict the sheet material behavior in both anisotropic hardening and cyclic hardening regimes more accurately. By featuring the above-mentioned facts in the presented constitutive model, it is expected that more accurate results can be obtained by implementing this model in computational simulations of sheet material forming processes. For instance, more precise results of springback prediction of the parts formed from highly anisotropic hardened materials or that of determining the forming limit diagrams is highly expected by using the developed material model.

  15. Solute hardening and softening effects in B2 nickel aluminides

    SciTech Connect

    Pike, L.M.; Liu, C.T.; Anderson, I.M.; Chang, Y.A.

    1998-11-01

    The effect of substitutional solute additions including Fe, Mn, and Pd on the hardness of B2-ordered NiAl alloys was investigated. The solid solution hardening behavior of intermetallics is more complex than that of typical metallic solid solutions because of complications arising from the site preference of the solute as well as the effects of the solute on the concentrations of other point defects, e.g., vacancies and anti-site defects. For this reason, care was taken to experimentally establish solute site preferences and point defect concentrations in the NiAl alloys before analyzing the hardness data. By taking these factors into account it was possible to rationalize the observed unusual hardening effects. Three distinct categories of solid solution hardening behavior were encountered. The first was hardening by the solute addition itself. This was observed in the case of Pd additions to Al-poor NiAl. However, when fe or Mn is added to Al-poor NiAl a second category is observed; these elements are seen to soften the material. The third category of behavior is observed when Fe is added to NiAl with a constant Al concentration of 50 at. %. In this case it is vacancies, rather than solute atoms, which harden the material.

  16. Dynamic bake hardening of interstitial-free steels

    SciTech Connect

    Dehghani, K.; Jonas, J.J.

    2000-05-01

    Two types of dynamic strain aging (DSA) strengthening methods were investigated to determine their potentials for industrial use. They are referred to here as dynamic-static bake hardening (DSBH) and dynamic bake hardening (DBH). For this purpose, a 0.06 pct Ti interstitial-free (IF) steel was reheated to 900 C and cooled at 12 C/s to room temperature. It was then dynamically bake hardened in the temperature range 100 C to 250 C to strains of 2 to 8 pct at a strain rate of 10{sup {minus}3} s{sup {minus}1}. The tensile properties were determined before and after these treatments. It was found that the occurrence of DSA during dynamic baking led to significant increases in work-hardening rate as well as in the final strength. The results indicate that, for a given solute carbon level, the dynamically and then statically aged samples have higher strengths than those that are bake hardened in the conventional way.

  17. General analytical shakedown solution for structures with kinematic hardening materials

    NASA Astrophysics Data System (ADS)

    Guo, Baofeng; Zou, Zongyuan; Jin, Miao

    2016-04-01

    The effect of kinematic hardening behavior on the shakedown behaviors of structure has been investigated by performing shakedown analysis for some specific problems. The results obtained only show that the shakedown limit loads of structures with kinematic hardening model are larger than or equal to those with perfectly plastic model of the same initial yield stress. To further investigate the rules governing the different shakedown behaviors of kinematic hardening structures, the extended shakedown theorem for limited kinematic hardening is applied, the shakedown condition is then proposed, and a general analytical solution for the structural shakedown limit load is thus derived. The analytical shakedown limit loads for fully reversed cyclic loading and non-fully reversed cyclic loading are then given based on the general solution. The resulting analytical solution is applied to some specific problems: a hollow specimen subjected to tension and torsion, a flanged pipe subjected to pressure and axial force and a square plate with small central hole subjected to biaxial tension. The results obtained are compared with those in literatures, they are consistent with each other. Based on the resulting general analytical solution, rules governing the general effects of kinematic hardening behavior on the shakedown behavior of structure are clearly.

  18. O-Demethylation and Successive Oxidative Dechlorination of Methoxychlor by Bradyrhizobium sp. Strain 17-4, Isolated from River Sediment

    PubMed Central

    Masuda, Minoru; Sato, Kiyoshi

    2012-01-01

    O-Demethylation of insecticide methoxychlor is well known as a phase I metabolic reaction in various eukaryotic organisms. Regarding prokaryotic organisms, however, no individual species involved in such reaction have been specified and characterized so far. Here we successfully isolated a bacterium that mediates oxidative transformation of methoxychlor, including O-demethylation and dechlorination, from river sediment. The isolate was found to be closely related to Bradyrhizobium elkanii at the 16S rRNA gene sequence level (100% identical). However, based on some differences in the physiological properties of this bacterium, we determined that it was actually a different species, Bradyrhizobium sp. strain 17-4. The isolate mediated O-demethylation of methoxychlor to yield a monophenolic derivative [Mono-OH; 1,1,1-trichloro-2-(4-hydroxyphenyl)-2-(4-methoxyphenyl)ethane] as the primary degradation product. The chiral high-performance liquid chromatography (HPLC) analysis revealed that the isolate possesses high enantioselectivity favoring the formation of (S)-Mono-OH (nearly 100%). Accompanied by the sequential O-demethylation to form the bis-phenolic derivative Bis-OH [1,1,1-trichloro-2,2-bis(4-hydroxyphenyl)ethane], oxidative dechlorination of the side chain proceeded, and monophenolic carboxylic acid accumulated, followed by the formation of multiple unidentified polar degradation products. The breakdown proceeded more rapidly when reductively dechlorinated (dichloro-form) methoxychlor was applied as the initial substrate. The resultant carboxylic acids and polar degradation products are likely further biodegraded by ubiquitous bacteria. The isolate possibly plays an important role for complete degradation (mineralization) of methoxychlor by providing the readily biodegradable substrates. PMID:22635993

  19. Precipitation Climate Data Records

    NASA Astrophysics Data System (ADS)

    Nelson, B. R.; Prat, O.; Vasquez, L.

    2015-12-01

    Five precipitation CDRs are now or soon will be transitioned to NOAA's CDR program. These include the PERSIANN data set, which is a 30-year record of daily adjusted global precipitation based on retrievals from satellite microwave data using artificial neural networks. The AMSU-A/B/Hydrobundle is an 11-year record of precipitable water, cloud water, ice water, and other variables. CMORPH (the NOAA Climate Prediction Center Morphing Technique) is a 17-year record of daily and sub-daily adjusted global precipitation measured from passive microwave and infrared data at high spatial and temporal resolution. GPCP (the Global Precipitation Climatology Project) is an approximately 30-year record of monthly and pentad adjusted global precipitation and a 17-year record of daily adjusted global precipitation. The NEXRAD Reanalysis is a 10-year record of high resolution NEXRAD radar based adjusted CONUS-wide hourly and daily precipitation. This study provides an assessment of the existing and transitioned long term precipitation CDRs and includes the verification of the five precipitation CDRs using various methods including comparison with in-situ data sets and trend analysis. As all of the precipitation related CDRs are transitioned, long term analyses can be performed. Comparisons at varying scales (hourly, daily and longer) of the precipitation CDRs with in-situ data sets are provided as well as a first look at what could be an ensemble long term precipitation data record.

  20. Secondary hardening steel having improved combination of hardness and toughness

    DOEpatents

    Parker, Earl R.; Zackay, Victor F.; Bhat, Manjeshwar S.; Garrison, Jr., Warren M.

    1979-01-01

    A secondary hardening alloy steel composition consisting essentially of about 0.25-0.5% carbon, about 0.5-1.0% manganese, about 1.5-3.0% nickel, about 0-1.0% chromium, about 1.75-2.5% molybdenum, about 0-0.4% vanadium, and an additive selected from about 1-3% aluminum and a combination of at least about 1% aluminum and at least about 1% silicon for a combined Al+Si content of about 2-4%, the balance being iron and impurity elements. The present steel composition has the following characteristics: it exhibits a flat tempering response, it is hardenable upon tempering to a Rockwell C hardness of at least 50, and it has an improved combination of hardness vs. toughness properties after tempering in the secondary hardening range. A method of preparation is also described.

  1. Crack resistance of tungsten hardened by dispersed refractory oxides

    SciTech Connect

    Babak, A.V.; Uskov, E.I.

    1985-05-01

    The authors present the results of an investigation of the crack resistance in a wide temperature range of the production types of tungsten VMP-S (conditionally designated technical purity tungsten with a higher degree of deformation than type VMP tungsten), VMP-3 (hardened with refractory oxides), and VMP-4 (with the addition of copper and hardened with refractory oxides) produced using the same method. It is reported that hardening of technical purity tungsten with refractory oxides increases the resistance of the material to crack development in the 20-2000C range, but the upper boundary of the temperature area of the ductile-to-brittle transition is shifted in the direction of higher temperatures, which must be taken into consideration in the use of the investigated alloys as structural materials for objects of new technology.

  2. Engineering design guidelines for electromagnetic pulse hardening of naval equipment

    NASA Astrophysics Data System (ADS)

    Rogers, S. R.; Perala, R. A.; Rosich, R. K.; Cook, R. B.; Rudolph, T. H.

    1981-07-01

    This document is intended to be used by engineers who design and manufacture shipboard equipment. It is complete in the sense that both the EMP hazard and the means of mitigating the hazard (hardening) are presented. The hazard is described, which not only discusses EMP generation in a general sense, but it also presents specific threat levels for EMP fields and transient currents and voltages included on cables and antennas which are connected to electronic equipment. This specific threat constitutes an EMP survivability criteria which must be met by the mission critical equipment. The necessary hardening technology areas include volume shielding, cable shielding and connectors, interface susceptibility analysis, terminal protective devices, upset and upset hardening, common mode rejection techniques, optical isolation, and grounding/bonding techniques. Test techniques which can verify equipment hardness are presented along with methods to observe the equipment's hardness and maintain the hardness.

  3. Data demonstrating the effects of build orientation and heat treatment on fatigue behavior of selective laser melted 17-4 PH stainless steel.

    PubMed

    Yadollahi, Aref; Simsiriwong, Jutima; Thompson, Scott M; Shamsaei, Nima

    2016-06-01

    Axial fully-reversed strain-controlled ([Formula: see text]) fatigue experiments were performed to obtain data demonstrating the effects of building orientation (i.e. vertical versus horizontal) and heat treatment on the fatigue behavior of 17-4 PH stainless steel (SS) fabricated via Selective Laser Melting (SLM) (Yadollahi et al., submitted for publication [1]). This data article provides detailed experimental data including cyclic stress-strain responses, variations of peak stresses during cyclic deformation, and fractography of post-mortem specimens for SLM 17-4 PH SS. PMID:26955653

  4. Photon and η production in p + Pb and p + C collisions at √{sNN}=17.4 GeV

    NASA Astrophysics Data System (ADS)

    Aggarwal, M. M.; Ahammed, Z.; Angelis, A. L. S.; Antonenko, V.; Arefiev, V.; Astakhov, V.; Avdeitchikov, V.; Awes, T. C.; Baba, P. V. K. S.; Badyal, S. K.; Bathe, S.; Batiounia, B.; Baumann, C.; Bernier, T.; Bhalla, K. B.; Bhatia, V. S.; Blume, C.; Bucher, D.; Büsching, H.; Carlén, L.; Chattopadhyay, S.; Decowski, M. P.; Delagrange, H.; Donni, P.; Dutta Majumdar, M. R.; El Chenawi, K.; Dubey, A. K.; Enosawa, K.; Fokin, S.; Frolov, V.; Ganti, M. S.; Garpman, S.; Gavrishchuk, O.; Geurts, F. J. M.; Ghosh, T. K.; Glasow, R.; Guskov, B.; Gustafsson, H. Å.; Gutbrod, H. H.; Hrivnacova, I.; Ippolitov, M.; Kalechofsky, H.; Kamermans, R.; Karadjev, K.; Karpio, K.; Kolb, B. W.; Kosarev, I.; Koutcheryaev, I.; Kugler, A.; Kulinich, P.; Kurata, M.; Lebedev, A.; Löhner, H.; Luquin, L.; Mahapatra, D. P.; Manko, V.; Martin, M.; Martínez, G.; Maximov, A.; Miake, Y.; Mishra, G. C.; Mohanty, B.; Mora, M.-J.; Morrison, D.; Mukhanova, T.; Mukhopadhyay, D. S.; Naef, H.; Nandi, B. K.; Nayak, S. K.; Nayak, T. K.; Nianine, A.; Nikitine, V.; Nikolaev, S.; Nilsson, P.; Nishimura, S.; Nomokonov, P.; Nystrand, J.; Oskarsson, A.; Otterlund, I.; Pavliouk, S.; Peitzmann, T.; Peressounko, D.; Petracek, V.; Phatak, S. C.; Pinganaud, W.; Plasil, F.; Purschke, M. L.; Rak, J.; Rammler, M.; Raniwala, R.; Raniwala, S.; Rao, N. K.; Retiere, F.; Reygers, K.; Roland, G.; Rosselet, L.; Roufanov, I.; Roy, C.; Rubio, J. M.; Sambyal, S. S.; Santo, R.; Sato, S.; Schlagheck, H.; Schmidt, H.-R.; Schutz, Y.; Shabratova, G.; Shah, T. H.; Sibiriak, I.; Siemiarczuk, T.; Silvermyr, D.; Sinha, B. C.; Slavine, N.; Söderström, K.; Sood, G.; Sørensen, S. P.; Stankus, P.; Stefanek, G.; Steinberg, P.; Stenlund, E.; Sumbera, M.; Svensson, T.; Tsvetkov, A.; Tykarski, L.; Pijll, E. C. v. d.; v. Eijndhoven, N.; v. Nieuwenhuizen, G. J.; Vinogradov, A.; Viyogi, Y. P.; Vodopianov, A.; Vörös, S.; Wysłouch, B.; Young, G. R.

    2013-01-01

    Measurements of direct photon production in p + Pb and p + C collisions at √{sNN}=17.4 GeV are presented. Upper limits on the direct photon yield as a function of pT are derived and compared to the results for Pb + Pb collisions at √{sNN}=17.3 GeV. The production of the η meson, which is an important input to the direct photon signal extraction, has been determined in the η→2γ channel for p + C collisions at √{sNN}=17.4 GeV.

  5. Hardenability of austenite in a dual-phase steel

    SciTech Connect

    Sarwar, M.; Priestner, R.

    1999-06-01

    A low-carbon, low-alloy steel was intercritically heat treated and thermomechanically processed to study the martensitic hardenability of austenite present. Rolling of the two-phase ({alpha} + {gamma}) microstructure elongated austenite particles and reduced their martensitic hardenability because the {alpha}/{gamma} interface where new ferrite forms during cooling was increased by the particle elongation. The martensite particles obtained in rolled material were also elongated or fibered in the rolling direction. Therefore, the thermomechanical processing of a two-phase ({alpha} + {gamma}) mixture has the detrimental effect of increasing the quenching power needed to yield a specific amount of martensite.

  6. Temperature influence on water transport in hardened cement pastes

    SciTech Connect

    Drouet, Emeline; Poyet, Stéphane; Torrenti, Jean-Michel

    2015-10-15

    Describing water transport in concrete is an important issue for the durability assessment of radioactive waste management reinforced concrete structures. Due to the waste thermal output such structures would be submitted to moderate temperatures (up to 80 °C). We have then studied the influence of temperature on water transport within hardened cement pastes of four different formulations. Using a simplified approach (describing only the permeation of liquid water) we characterized the properties needed to describe water transport (up to 80 °C) using dedicated experiments. For each hardened cement paste the results are presented and discussed.

  7. Statistical thermodynamics of strain hardening in polycrystalline solids

    SciTech Connect

    Langer, James S.

    2015-09-18

    This paper starts with a systematic rederivation of the statistical thermodynamic equations of motion for dislocation-mediated plasticity proposed in 2010 by Langer, Bouchbinder, and Lookman. The paper then uses that theory to explain the anomalous rate-hardening behavior reported in 1988 by Follansbee and Kocks and to explore the relation between hardening rate and grain size reported in 1995 by Meyers et al. A central theme is the need for physics-based, nonequilibrium analyses in developing predictive theories of the strength of polycrystalline materials.

  8. Impact of Scaled Technology on Radiation Testing and Hardening

    NASA Technical Reports Server (NTRS)

    LaBel, Kenneth A.; Cohn, Lewis M.

    2005-01-01

    This presentation gives a brief overview of some of the radiation challenges facing emerging scaled digital technologies with implications on using consumer grade electronics and next generation hardening schemes. Commercial semiconductor manufacturers are recognizing some of these issues as issues for terrestrial performance. Looking at means of dealing with soft errors. The thinned oxide has indicated improved TID tolerance of commercial products hardened by "serendipity" which does not guarantee hardness or say if the trend will continue. This presentation also focuses one reliability implications of thinned oxides.

  9. Statistical thermodynamics of strain hardening in polycrystalline solids

    SciTech Connect

    Langer, James S.

    2015-01-01

    This paper starts with a systematic rederivation of the statistical thermodynamic equations of motion for dislocation-mediated plasticity proposed in 2010 by Langer, Bouchbinder, and Lookman. The paper then uses that theory to explain the anomalous rate-hardening behavior reported in 1988 by Follansbee and Kocks and to explore the relation between hardening rate and grain size reported in 1995 by Meyers et al. A central theme is the need for physics-based, nonequilibrium analyses in developing predictive theories of the strength of polycrystalline materials.

  10. Why semiconductors must be hardened when used in space

    SciTech Connect

    Winokur, P. S.

    2000-01-04

    The natural space radiation environment presents a great challenge to present and future satellite systems with significant assets in space. Defining requirements for such systems demands knowledge about the space radiation environment and its effects on electronics and optoelectronics technologies, as well as suitable risk assessment of the uncertainties involved. For mission of high radiation levels, radiation-hardened integrated circuits will be required to preform critical mission functions. The most successful systems in space will be those that are best able to blend standard commercial electronics with custom radiation-hardened electronics in a mix that is suitable for the system of interest.

  11. Statistical thermodynamics of strain hardening in polycrystalline solids

    NASA Astrophysics Data System (ADS)

    Langer, J. S.

    2015-09-01

    This paper starts with a systematic rederivation of the statistical thermodynamic equations of motion for dislocation-mediated plasticity proposed in 2010 by Langer, Bouchbinder, and Lookman [Acta Mat. 58, 3718 (2010), 10.1016/j.actamat.2010.03.009]. It then uses that theory to explain the anomalous rate-hardening behavior reported in 1988 by Follansbee and Kocks and to explore the relation between hardening rate and grain size reported in 1995 by Meyers et al. A central theme is the need for physics-based, nonequilibrium analyses in developing predictive theories of the strength of polycrystalline materials.

  12. Modelling work hardening of aluminium alloys containing dispersoids

    NASA Astrophysics Data System (ADS)

    Zhao, Qinglong; Holmedal, Bjørn

    2013-08-01

    The influence of dispersoids on tensile deformation behaviour has been studied by comparison of aluminium alloys containing different dispersoid densities. It was found that a fine dispersion of non-shearable particles led to an increased work hardening at the initial plastic deformation, but the effect was opposite at higher strains. The reason has been attributed to the generation of geometrically necessary dislocations (GNDs). A new model has been proposed for the evolution of GNDs based on a balance of storage and dynamic recovery of GNDs. The model predicts a rapid saturation of GNDs and a reduced work hardening at small strains, consistent with the experimental results.

  13. On the hardening and softening of nanocrystalline materials

    SciTech Connect

    Fougere, G.E.; Weertman, J.R. . Dept. of Materials Science and Engineering); Siegel, R.W. . Materials Science Div.)

    1993-04-01

    Nanocrystalline Pd and Cu samples have been thermally treated to determine whether the relation between hardness and grain size depend on the method used to vary the grain sizes. Previous reports indicate that hardening with decreasing grain size resulted from data obtained using individual samples, while softening with decreasing grain size resulted from data from a given sample that had been thermally treated. Hardening and softening regimes were evident for the nanocrystalline cu, and the hardness improvements over the original as-consolidated state were maintained throughout the thermal treatments. This review examines our hardness results for Cu and Pd and those for other nanocrystalline materials.

  14. Fine precipitation scenarios of AlZnMg(Cu) alloys revealed by advanced atomic-resolution electron microscopy study Part II: Fine precipitation scenarios in AlZnMg(Cu) alloys

    SciTech Connect

    Liu, J.Z.; Chen, J.H.; Liu, Z.R.; Wu, C.L.

    2015-01-15

    Although they are among the most important precipitation-hardened materials for industry applications, the high-strength AlZnMg(Cu) alloys have thus far not yet been understood adequately about their underlying precipitation scenarios in relation with the properties. This is partly due to the fact that the structures of a number of different precipitates involved in the alloys are unknown, and partly due to the complexity that the precipitation behaviors of the alloys may be closely related to the alloy's composition. In Part I of the present study, we have determined all the unknown precipitate structures in the alloys. Here in Part II, using atomic-resolution electron microscopy in association with the first principles energy calculations, we further studied and correlated the phase/structure transformation/evolution among these hardening precipitates in relation with the alloy's composition. It is shown that there are actually two coexisting classes of hardening precipitates in these alloys: the first class includes the η′-precipitates and their early-stage Guinier–Preston (GP-η′) zones; the second class includes the precursors of the equilibrium η-phase (referred to η{sub p}, or η-precursor) and their early-stage Guinier–Preston (GP-η{sub p}) zones. The two coexisting classes of precipitates correspond to two precipitation scenarios. - Highlights: • We determine and verify all the key precipitate structures in AlMgZn(Cu) alloys. • We employ aberration-corrected scanning transmission electron microscopy (STEM). • We use aberration-corrected high-resolution TEM (HRTEM) for the investigations. • We obtain atomic-resolution images of the precipitates and model their structures. • We refine all precipitate structures with quantitative image simulation analysis. • The hardening precipitates in AlZnMg alloys shall be classified into two groups. • Two precipitation scenarios coexist in the alloys. • The precipitation behavior of such an

  15. Influence of Si Addition on Quenching Sensitivity and Formation of Nano-Precipitate in Al-Mg-Si Alloys.

    PubMed

    Kim, JaeHwang; Hayashi, Minoru; Kobayashi, Equo; Sato, Tatsuo

    2016-02-01

    The age-hardening is enhanced with the high cooling rate since more vacancies are formed during quenching, whereas the stable beta phase is formed with the slow cooling rate just after solid solution treatment resulting in lower increase of hardness during aging. Meanwhile, the nanoclusters are formed during natural aging in Al-Mg-Si alloys. The formation of nanoclusters is enhanced with increasing the Si amount. High quench sensitivity based on mechanical property changes was confirmed with increasing the Si amount. Moreover, the nano-size beta" phase, main hardening phase, is more formed by the Si addition resulting in enhancement of the age-hardening. The quench sensitivity and the formation behavior of precipitates are discussed based on the age-hardening phenomena. PMID:27433677

  16. Mesoscale modeling of solute precipitation and radiation damage

    SciTech Connect

    Zhang, Yongfeng; Schwen, Daniel; Ke, Huibin; Bai, Xianming; Hales, Jason

    2015-09-01

    This report summarizes the low length scale effort during FY 2014 in developing mesoscale capabilities for microstructure evolution in reactor pressure vessels. During operation, reactor pressure vessels are subject to hardening and embrittlement caused by irradiation-induced defect accumulation and irradiation-enhanced solute precipitation. Both defect production and solute precipitation start from the atomic scale, and manifest their eventual effects as degradation in engineering-scale properties. To predict the property degradation, multiscale modeling and simulation are needed to deal with the microstructure evolution, and to link the microstructure feature to material properties. In this report, the development of mesoscale capabilities for defect accumulation and solute precipitation are summarized. Atomic-scale efforts that supply information for the mesoscale capabilities are also included.

  17. Magnetic evaluation of irradiation hardening in A533B reactor pressure vessel steels: Magnetic hysteresis measurements and the model analysis

    NASA Astrophysics Data System (ADS)

    Kobayashi, S.; Yamamoto, T.; Klingensmith, D.; Odette, G. R.; Kikuchi, H.; Kamada, Y.

    2012-03-01

    We report results of measurements of magnetic minor hysteresis loops for neutron-irradiated A533B nuclear reactor pressure vessel steels varying alloy composition and irradiation condition. A minor-loop coefficient, which is obtained from a scaling power law between minor-loop parameters exhibits a steep decrease just after irradiation, followed by a maximum in the intermediate fluence regime for most alloys. A model analysis assuming Avrami-type growth for Cu-rich precipitates and an empirical logarithmic law for relaxation of residual stress demonstrates that an increment of the coefficient due to Cu-rich precipitates increases with Cu and Ni contents and is in proportion to a yield stress change, which is related to irradiation hardening.

  18. A radiation-hardened 16/32-bit microprocessor

    SciTech Connect

    Hass, K.J.; Treece, R.K.; Giddings, A.E.

    1989-01-01

    A radiation-hardened 16/32-bit microprocessor has been fabricated and tested. Our initial evaluation has demonstrated that it is functional after a total gamma dose of 5Mrad(Si) and is immune to SEU from Krypton ions. 3 refs., 2 figs.

  19. 49. INTERIOR VIEW OF HARDENER AREA SHOWING GAUGE THAT MEASURES ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    49. INTERIOR VIEW OF HARDENER AREA SHOWING GAUGE THAT MEASURES HARDNESS, THE NAIL MUST BREAK IN THE CENTER RANGE OF THE CURVED BAR TO HAVE THE CORRECT HARDNESS (THE NAIL WILL BREAK TOO EASILY IF TOO HARD AND WILL BEND TOO MUCH IF TOO SOFT) - LaBelle Iron Works, Thirtieth & Wood Streets, Wheeling, Ohio County, WV

  20. Iterative Beam Hardening Correction for Multi-Material Objects

    PubMed Central

    Zhao, Yunsong; Li, Mengfei

    2015-01-01

    In this paper, we propose an iterative beam hardening correction method that is applicable for the case with multiple materials. By assuming that the materials composing scanned object are known and that they are distinguishable by their linear attenuation coefficients at some given energy, the beam hardening correction problem is converted into a nonlinear system problem, which is then solved iteratively. The reconstructed image is the distribution of linear attenuation coefficient of the scanned object at a given energy. So there are no beam hardening artifacts in the image theoretically. The proposed iterative scheme combines an accurate polychromatic forward projection with a linearized backprojection. Both forward projection and backprojection have high degree of parallelism, and are suitable for acceleration on parallel systems. Numerical experiments with both simulated data and real data verifies the validity of the proposed method. The beam hardening artifacts are alleviated effectively. In addition, the proposed method has a good tolerance on the error of the estimated x-ray spectrum. PMID:26659554

  1. Iterative Beam Hardening Correction for Multi-Material Objects.

    PubMed

    Zhao, Yunsong; Li, Mengfei

    2015-01-01

    In this paper, we propose an iterative beam hardening correction method that is applicable for the case with multiple materials. By assuming that the materials composing scanned object are known and that they are distinguishable by their linear attenuation coefficients at some given energy, the beam hardening correction problem is converted into a nonlinear system problem, which is then solved iteratively. The reconstructed image is the distribution of linear attenuation coefficient of the scanned object at a given energy. So there are no beam hardening artifacts in the image theoretically. The proposed iterative scheme combines an accurate polychromatic forward projection with a linearized backprojection. Both forward projection and backprojection have high degree of parallelism, and are suitable for acceleration on parallel systems. Numerical experiments with both simulated data and real data verifies the validity of the proposed method. The beam hardening artifacts are alleviated effectively. In addition, the proposed method has a good tolerance on the error of the estimated x-ray spectrum. PMID:26659554

  2. An SEU-hardened CMOS data latch design

    SciTech Connect

    Rockett, L.R. Jr.

    1988-12-01

    A Single Event Upset (SEU)-hardened Complementary Metal-Oxide Semiconductor (CMOS) data latch design is described. The hardness is achieved by virtue of the latch design, thus no fabrication process or design groundrule development is required. Hardness is gained with comparatively little adverse impact on performance. Cyclotron tests provided hardness verification.

  3. SEU-hardened storage cell validation using a pulsed laser

    SciTech Connect

    Velazco, R.

    1996-12-01

    Laser tests performed on a prototype chip to validate new SEU-hardened storage cell designs revealed unexpected latch-up and single-event upset phenomena. The investigations that identified their location show the existence of a topology-dependent dual node upset mechanism. Design solutions are suggested to avoid its occurrence.

  4. Overcoming scaling concerns in a radiation-hardening CMOS technology

    SciTech Connect

    Maimon, J.; Haddad, N.

    1999-12-01

    Scaling efforts to develop an advanced radiation-hardened CMOS process to support a 4M SRAM are described. Issues encountered during scaling of transistor, isolation, and resistor elements are discussed, as well as the solutions used to overcome these issues. Transistor data, total dose radiation results, and the performance of novel resistors for prevention of single event upsets (SEU) are presented.

  5. Hardening digital systems with distributed functionality: robust networks

    NASA Astrophysics Data System (ADS)

    Vaskova, Anna; Portela-Garcia, Marta; Garcia-Valderas, Mario; López-Ongil, Celia; Portilla, Jorge; Valverde, Juan; de la Torre, Eduardo; Riesgo, Teresa

    2013-05-01

    Collaborative hardening and hardware redundancy are nowadays the most interesting solutions in terms of fault tolerance achieved and low extra cost imposed to the project budget. Thanks to the powerful and cheap digital devices that are available in the market, extra processing capabilities can be used for redundant tasks, not only in early data processing (sensed data) but also in routing and interfacing1

  6. Beam hardening correction for sparse-view CT reconstruction

    NASA Astrophysics Data System (ADS)

    Liu, Wenlei; Rong, Junyan; Gao, Peng; Liao, Qimei; Lu, HongBing

    2015-03-01

    Beam hardening, which is caused by spectrum polychromatism of the X-ray beam, may result in various artifacts in the reconstructed image and degrade image quality. The artifacts would be further aggravated for the sparse-view reconstruction due to insufficient sampling data. Considering the advantages of the total-variation (TV) minimization in CT reconstruction with sparse-view data, in this paper, we propose a beam hardening correction method for sparse-view CT reconstruction based on Brabant's modeling. In this correction model for beam hardening, the attenuation coefficient of each voxel at the effective energy is modeled and estimated linearly, and can be applied in an iterative framework, such as simultaneous algebraic reconstruction technique (SART). By integrating the correction model into the forward projector of the algebraic reconstruction technique (ART), the TV minimization can recover images when only a limited number of projections are available. The proposed method does not need prior information about the beam spectrum. Preliminary validation using Monte Carlo simulations indicates that the proposed method can provide better reconstructed images from sparse-view projection data, with effective suppression of artifacts caused by beam hardening. With appropriate modeling of other degrading effects such as photon scattering, the proposed framework may provide a new way for low-dose CT imaging.

  7. Review of radiation hardening techniques for EDFAs in space environment

    NASA Astrophysics Data System (ADS)

    Wang, Qian; Tian, CuiPing; Wang, YingYing; Wang, Pu

    2015-03-01

    The damage mechanism and test technology of space radiation environment to space equipment was classified and the radiation protection demand of active fiber for space application was analyzed. The radiation hardening techniques of Ce doping, hydrogen loading and pre-radiation exposure and thermal annealing for Er:Yb co-doped fiber was surveyed.

  8. Total dose performance of radiation hardened voltage regulators and references

    NASA Technical Reports Server (NTRS)

    McClure, S.; Gorelick, J.; Pease, R.; Rax, B.; Ladbury, R.

    2001-01-01

    Total dose test of commercially available radiation hardened bipolar voltage regulators and references show reduced sensitivity to dose rate and varying sensitivity to bias under pressure. Behavior of critical parameters in different dose rate and bias conditions is compared and the impact to hardness assurance methodology is discussed.

  9. SEGR response of a radiation-hardened power MOSFET technology

    SciTech Connect

    Wheatley, C.F.; Titus, J.L.; Burton, D.I.; Carley, D.R.

    1996-12-01

    SEGR response curves are presented for eighteen different device types of radiation-hardened power MOSFETs. Comparisons are made to demonstrate the technology`s insensitivity to die size, rated blocking voltage, channel conductivity, and temperature. From this data, SEGR cross-sectional area curves are inferred.

  10. Hardening due to dislocation loop damage in RPV model alloys: Role of Mn segregation

    NASA Astrophysics Data System (ADS)

    Terentyev, D.; He, X.; Bonny, G.; Bakaev, A.; Zhurkin, E.; Malerba, L.

    2015-02-01

    The exact nature of the radiation defects causing hardening in reactor vessel pressure steels at high doses is not yet clearly determined. While generally it is attributed to solute-rich clusters (precipitates) and point defects clusters (matrix damage), recent fine-scale experiments and atomistic simulations suggest that solute rich clusters, mainly containing Mn, Ni and Cu, might be the result of the segregation of these elements to small dislocation loops (heterogeneous nucleation), so that the distinction between precipitates and matrix damage becomes blurred. Here, we perform an atomistic study to investigate the interaction of a0/2<1 1 1> dislocation loops with moving dislocations and specifically address the effect of solute segregation on the loop's strength and interaction mechanism, focusing in particular on Mn, alone or with other crucial solute elements such as Cu and Ni. It is found that the enrichment of Mn in the core of dislocation loops causes significant increase of the unpinning stress, especially for small, invisible ones. At the same time, the solute segregation at the dislocation loops enhances their resistance against absorption by moving dislocations.

  11. Age hardening and creep resistance of cast Al–Cu alloy modified by praseodymium

    SciTech Connect

    Bai, Zhihao; Qiu, Feng; Wu, Xiaoxue; Liu, Yingying; Jiang, Qichuan

    2013-12-15

    The effects of praseodymium on age hardening behavior and creep resistance of cast Al–Cu alloy were investigated. The results indicated that praseodymium facilitated the formation of the θ′ precipitates during the age process and improved the hardness of the Al–Cu alloy. Besides, praseodymium resulted in the formation of the Al{sub 11}Pr{sub 3} phase in the grain boundaries and among the dendrites of the modified alloy. Because of the good thermal stability of Al{sub 11}Pr{sub 3} phase, it inhibits grain boundary migration and dislocation movement during the creep process, which contributes to the improvement in the creep resistance of the modified alloy at elevated temperatures. - Highlights: • Pr addition enhances the hardness and creep resistance of the Al–Cu alloy. • Pr addition facilitates the formation of the θ′ precipitates. • Pr addition results in the formation of the Al11Pr3 phase in the Al–Cu alloy.

  12. Development of a nanoscale precipitation-strengthened creep-resistant aluminum alloy containing trialuminide precipitates

    NASA Astrophysics Data System (ADS)

    Knipling, Keith Edward

    This research is toward developing a castable and heat-treatable precipitation-strengthened aluminum alloy exhibiting coarsening- and creep resistance at temperatures exceeding 400°C. Criteria for selecting alloying elements capable of producing such an alloy are established. Those systems forming Al3M trialuminide compounds with a cubic L12 crystal structure are favored, and based on a review of the existing literature, these are assessed in terms of solid-solubility and diffusivity in alpha-Al(satisfying the need for slow coarsening kinetics), and castability (which is discussed based on the binary phase diagrams). The first Group 3 element, Sc, and the second Group 4 element, Zr, are shown to be most promising. These expectations are confirmed by an initial study on the Al-Ti system, which demonstrates that conventionally-solidified alloys are not capable of precipitation strengthening. The Al-Zr system, by contrast, exhibits precipitation of nanometer-scale Al3Zr (L12) producing pronounced precipitation hardening when aged at 375, 400, or 425°C. The Al3 Zr precipitates are coarsening resistant and have the metastable L1 2 structure up to 500°C, a result of very sluggish diffusion of Zr in alpha-Al. Ternary additions of Ti are also investigated, forming Al 3(Zr1-xTix) (L12) precipitates with a reduced lattice parameter mismatch with alpha-Al, potentially improving the coarsening resistance. The composition of Al3(Zr1-xTi x) precipitates formed at 375 or 425°C are measured directly using 3-D atom-probe tomography. At these temperatures, the Zr:Ti atomic ratio in the precipitates is about 10 and 5, respectively, indicating that most of the available Ti fails to partition to the Al3(Zr1- xTix) phase. This is consistent with prior studies on Al-Sc alloys, where the slower-diffusing ternary solute species make up a small fraction of the Al3Sc-based precipitates. Despite the confirmed presence of Ti, Al3(Zr1- xTix) precipitates exhibit no improvement in terms of

  13. Nanoscale characterization of the biomechanical hardening of bovine zona pellucida.

    PubMed

    Boccaccio, Antonio; Frassanito, Maria Cristina; Lamberti, Luciano; Brunelli, Roberto; Maulucci, Giuseppe; Monaci, Maurizio; Papi, Massimiliano; Pappalettere, Carmine; Parasassi, Tiziana; Sylla, Lakamy; Ursini, Fulvio; De Spirito, Marco

    2012-11-01

    The zona pellucida (ZP) is an extracellular membrane surrounding mammalian oocytes. The so-called zona hardening plays a key role in fertilization process, as it blocks polyspermy, which may also be caused by an increase in the mechanical stiffness of the ZP membrane. However, structural reorganization mechanisms leading to ZP's biomechanical hardening are not fully understood yet. Furthermore, a correct estimate of the elastic properties of the ZP is still lacking. Therefore, the aim of the present study was to investigate the biomechanical behaviour of ZP membranes extracted from mature and fertilized bovine oocytes to better understand the mechanisms involved in the structural reorganization of the ZP that may lead to the biomechanical hardening of the ZP. For that purpose, a hybrid procedure is developed by combining atomic force microscopy nanoindentation measurements, nonlinear finite element analysis and nonlinear optimization. The proposed approach allows us to determine the biomechanical properties of the ZP more realistically than the classical analysis based on Hertz's contact theory, as it accounts for the nonlinearity of finite indentation process, hyperelastic behaviour and material heterogeneity. Experimental results show the presence of significant biomechanical hardening induced by the fertilization process. By comparing various hyperelastic constitutive models, it is found that the Arruda-Boyce eight-chain model best describes the biomechanical response of the ZP. Fertilization leads to an increase in the degree of heterogeneity of membrane elastic properties. The Young modulus changes sharply within a superficial layer whose thickness is related to the characteristic distance between cross-links in the ZP filamentous network. These findings support the hypothesis that biomechanical hardening of bovine ZP is caused by an increase in the number of inter-filaments cross-links whose density should be higher in the ZP inner side. PMID:22675161

  14. Cu-Precipitation Strengthening in Ultrahigh-Strength Carburizing Steels

    NASA Astrophysics Data System (ADS)

    Tiemens, Benjamin L.; Sachdev, Anil K.; Olson, Gregory B.

    2012-10-01

    Ultrahigh hardness levels greater than 700 VHN can be obtained in secondary hardening carburizing steels but depend on costly Co alloying additions to maximize hardness achieved through M2C-type carbide precipitation strengthening. This study aims to incorporate nanometer-scale bcc Cu precipitates to both provide strength as well as catalyze M2C nucleation in the absence of or with reduced Co. Cu additions of 1.0 and 3.7 wt pct were investigated, using a series of mechanistic models coupled with thermodynamic computational tools to derive final compositions. Thirty-pound experimental heats were cast of each designed alloy, samples of which were carburized and tempered to determine their hardness response. Characterization revealed the successful incorporation of Cu alloying additions into this family of steels, demonstrating a secondary hardening response even in the absence of Co. Matrix strength levels were close to those predicted by design models; however, all four alloys demonstrated a hardness deficit of approximately 200 VHN at the carburized surface, suggesting recalibration of the M2C precipitation strengthening model may be required in these alloys.

  15. Precipitation in 9Ni-12Cr-2Cu maraging steels

    SciTech Connect

    Stiller, K.; Haettestrand, M.; Danoix, F.

    1998-11-02

    Two maraging steels with the compositions 9Ni-12Cr-2Cu-4Mo (wt%) and 9Ni-12Cr-2Cu and with small additions of Al and Ti were investigated using atom probe field ion microscopy. Tomographic atom probe investigations were performed to clarify the spatial distribution of elements in and close to the precipitates. Materials heat treated at 475 C for 5, 25 min, 1, 2, 4 and 400 h were analyzed. Precipitates in the Mo-rich material were observed already after 5 min of aging, while in the material without MO, precipitation started later. In both materials precipitation begins with the formation of Cu-rich particles which work as nucleation sites for a Ni-rich phase of type Ni{sub 3}(Ti,Al). A Mo-rich phase was detected in the Mo-rich steel after 2 h of aging. The distribution of alloying elements in the precipitates, their role in the precipitation process, and the mechanism of hardening in the two materials are discussed.

  16. A micro-alloyed ferritic steel strengthened by nanoscale precipitates

    SciTech Connect

    Shen, Yongfeng; Wang, Chong M.; Sun, Xin

    2011-10-25

    A ferritic steel with finely dispersive precipitates was investigated to reveal the fundamental strengthening mechanisms. The steel has a yield strength of 760 MPa, approximately three times higher than that of conventional Ti-bearing high strength hot-rolled sheet steels, and its ultimate tensile strength reaches 850 MPa with an elongation-to-failure value of 18%. Using energy dispersive X-ray spectroscopy (EDXS) and transmission electron microscope (TEM), fine carbides TiC with an average diameter of 10 nm were observed in the ferrite matrix of the 0.08%Ti steel, and some cubic M23C6 precipitates were also observed at the grain boundaries and the interior of the grains. The finely dispersive TiC precipitates in the matrix provide matrix strengthening. The estimated magnitude of precipitation strengthening is around 458 MPa, depending on the average size of the nanoscale precipitates. Dislocation densities increased from 3.42×1013 m-2 to 1.69 × 1014 m-2, respectively, with increasing tensile strain from 5.5% to 22%. The measured work-hardening behavior can be related to the observed dislocation accumulations resulting from the dispersive nano-scale precipitates.

  17. Selective Precipitation of Proteins.

    PubMed

    Matulis, Daumantas

    2016-01-01

    Selective precipitation of proteins can be used as a bulk method to recover the majority of proteins from a crude lysate, as a selective method to fractionate a subset of proteins from a protein solution, or as a very specific method to recover a single protein of interest from a purification step. This unit describes a number of methods suitable for selective precipitation. In each of the protocols that are outlined, the physical or chemical basis of the precipitation process, the parameters that can be varied for optimization, and the basic steps for developing an optimized precipitation are described. PMID:26836410

  18. Global Precipitation Measurement

    NASA Technical Reports Server (NTRS)

    Hou, Arthur Y.; Skofronick-Jackson, Gail; Kummerow, Christian D.; Shepherd, James Marshall

    2008-01-01

    This chapter begins with a brief history and background of microwave precipitation sensors, with a discussion of the sensitivity of both passive and active instruments, to trace the evolution of satellite-based rainfall techniques from an era of inference to an era of physical measurement. Next, the highly successful Tropical Rainfall Measuring Mission will be described, followed by the goals and plans for the Global Precipitation Measurement (GPM) Mission and the status of precipitation retrieval algorithm development. The chapter concludes with a summary of the need for space-based precipitation measurement, current technological capabilities, near-term algorithm advancements and anticipated new sciences and societal benefits in the GPM era.

  19. The Structure and Properties of Diffusion Assisted Bonded Joints in 17-4 PH, Type 347, 15-5 PH and Nitronic 40 Stainless Steels

    NASA Technical Reports Server (NTRS)

    Wigley, D. A.

    1981-01-01

    Diffusion assisted bonds are formed in 17-4 PH, 15-5 PH, type 347 and Nitronic 40 stainless steels using electrodeposited copper as the bonding agent. The bonds are analyzed by conventional metallographic, electron microprobe analysis, and scanning electron microscopic techniques as well as Charpy V-notch impact tests at temperatures of 77 and 300 K. Results are discussed in terms of a postulated model for the bonding process.

  20. Age hardening of 6061/alumina-silica fiber composite

    SciTech Connect

    Khangaonkar, P.R.; Shamsul, J.B.; Azmi, R.

    1994-12-31

    Continuous alumina-silica fiber (Altex of Sumitomo) which yields high performance composites with some aluminium alloys was tried for squeeze cast 6061 based composites with volume fractions of 0.5 and 0.32, and the matrix microhardness and resistivity changes during age hardening were studied. The matrix in the composites hardened much more than the unreinforced alloy. Microhardness increases of up to 70 VPN above the solution treated condition at various aging temperatures were observed. The resistivity variation indicated an appreciable state of internal stress which continued to persist even when hardness fell by overaging. Energy dispersive X-ray analysis indicated that the regions close to the fibers had a higher silicon content than the matrix, and amorphous silica in the fiber may have a role in the formation of an enriched layer which may help the bonding and strength in the composite.

  1. ORIGIN OF THE COSMIC-RAY SPECTRAL HARDENING

    SciTech Connect

    Tomassetti, Nicola

    2012-06-10

    Recent data from ATIC, CREAM, and PAMELA indicate that the cosmic-ray energy spectra of protons and nuclei exhibit a remarkable hardening at energies above 100 GeV nucleon{sup -1}. We propose that the hardening is an interstellar propagation effect that originates from a spatial change of the cosmic-ray transport properties in different regions of the Galaxy. The key hypothesis is that the diffusion coefficient is not separable into energy and space variables as usually assumed. Under this scenario, we can reproduce the observational data well. Our model has several implications for cosmic-ray acceleration/propagation physics and can be tested by ongoing experiments such as the Alpha Magnetic Spectrometer or Fermi-LAT.

  2. Hardening electronic devices against very high total dose radiation environments

    NASA Technical Reports Server (NTRS)

    Buchanan, B.; Shedd, W.; Roosild, S.; Dolan, R.

    1972-01-01

    The possibilities and limitations of hardening silicon semiconductor devices to the high neutron and gamma radiation levels and greater than 10 to the eighth power rads required for the NERVA nuclear engine development are discussed. A comparison is made of the high dose neutron and gamma hardening potential of bipolar, metal insulator semiconductors and junction field effect transistors. Experimental data is presented on device degradation for the high neutron and gamma doses. Previous data and comparisons indicate that the JFET is much more immune to the combined neutron displacement and gamma ionizing effects than other transistor types. Experimental evidence is also presented which indicates that p channel MOS devices may be able to meet the requirements.

  3. Stress and Distortion Evolution During Induction Case Hardening of Tube

    NASA Astrophysics Data System (ADS)

    Nemkov, Valentin; Goldstein, Robert; Jackowski, John; Ferguson, Lynn; Li, Zhichao

    2013-07-01

    Simulation of stresses during heat treatment relates usually to furnace heating. Induction heating provides a very different evolution of temperature in the part and therefore different stresses. This may be positive for service properties or negative, reducing component strength or even causing cracks. A method of coupled simulation between electromagnetic, thermal, structural, stress, and deformation phenomena during induction tube hardening is described. Commercial software package ELTA is used to calculate the power density distribution in the load resulting from the induction heating process. The program DANTE is used to predict temperature distribution, phase transformations, stress state, and deformation during heating and quenching. Analyses of stress and deformation evolution were made on a simple case of induction hardening of external (1st case) and internal (2nd case) surfaces of a thick-walled tubular body.

  4. A Brief Discussion of Radiation Hardening of CMOS Microelectronics

    SciTech Connect

    Myers, D.R.

    1998-12-18

    Commercial microchips work well in their intended environments. However, generic microchips will not fimction correctly if exposed to sufficient amounts of ionizing radiation, the kind that satellites encounter in outer space. Modern CMOS circuits must overcome three specific concerns from ionizing radiation: total-dose, single-event, and dose-rate effects. Minority-carrier devices such as bipolar transistors, optical receivers, and solar cells must also deal with recombination-generation centers caused by displacement damage, which are not major concerns for majority-carrier CMOS devices. There are ways to make the chips themselves more resistant to radiation. This extra protection, called radiation hardening, has been called both a science and an art. Radiation hardening requires both changing the designs of the chips and altering the ways that the chips are manufactured.

  5. Segmentation-free empirical beam hardening correction for CT

    SciTech Connect

    Schüller, Sören; Sawall, Stefan; Stannigel, Kai; Hülsbusch, Markus; Ulrici, Johannes; Hell, Erich; Kachelrieß, Marc

    2015-02-15

    Purpose: The polychromatic nature of the x-ray beams and their effects on the reconstructed image are often disregarded during standard image reconstruction. This leads to cupping and beam hardening artifacts inside the reconstructed volume. To correct for a general cupping, methods like water precorrection exist. They correct the hardening of the spectrum during the penetration of the measured object only for the major tissue class. In contrast, more complex artifacts like streaks between dense objects need other techniques of correction. If using only the information of one single energy scan, there are two types of corrections. The first one is a physical approach. Thereby, artifacts can be reproduced and corrected within the original reconstruction by using assumptions in a polychromatic forward projector. These assumptions could be the used spectrum, the detector response, the physical attenuation and scatter properties of the intersected materials. A second method is an empirical approach, which does not rely on much prior knowledge. This so-called empirical beam hardening correction (EBHC) and the previously mentioned physical-based technique are both relying on a segmentation of the present tissues inside the patient. The difficulty thereby is that beam hardening by itself, scatter, and other effects, which diminish the image quality also disturb the correct tissue classification and thereby reduce the accuracy of the two known classes of correction techniques. The herein proposed method works similar to the empirical beam hardening correction but does not require a tissue segmentation and therefore shows improvements on image data, which are highly degraded by noise and artifacts. Furthermore, the new algorithm is designed in a way that no additional calibration or parameter fitting is needed. Methods: To overcome the segmentation of tissues, the authors propose a histogram deformation of their primary reconstructed CT image. This step is essential for the

  6. Magnetic hardening in FePt nanostructured films

    SciTech Connect

    Liu, J.P.; Liu, Y.; Luo, C.P.; Shan, Z.S.; Sellmyer, D.J.

    1997-04-01

    FePt films have been prepared by sputtering Fe/Pt multilayers onto glass or silicon substrates. The thickness of the Fe and Pt layers was adjusted with the Fe:Pt atomic ratio from about 1:1 to 2:1. Magnetic hardening is observed after heat treatment at elevated temperatures, which led to coercivity values exceeding 20 kOe in samples with an Fe:Pt ratio around 1.2:1. The hardening originates from the formation of the tetragonal FePt phase with high magnetocrystalline anisotropy and a favorable microstructure. Two-phase composite films containing hard and soft phases were obtained when the Fe:Pt ratio increased. Under optimized processing conditions, composite films with energy products larger than 30 MGOe at room temperature have been successfully produced. {copyright} {ital 1997 American Institute of Physics.}

  7. Magnetic hardening in FePt nanostructured films

    NASA Astrophysics Data System (ADS)

    Liu, J. P.; Liu, Y.; Luo, C. P.; Shan, Z. S.; Sellmyer, D. J.

    1997-04-01

    FePt films have been prepared by sputtering Fe/Pt multilayers onto glass or silicon substrates. The thickness of the Fe and Pt layers was adjusted with the Fe:Pt atomic ratio from about 1:1 to 2:1. Magnetic hardening is observed after heat treatment at elevated temperatures, which led to coercivity values exceeding 20 kOe in samples with an Fe:Pt ratio around 1.2:1. The hardening originates from the formation of the tetragonal FePt phase with high magnetocrystalline anisotropy and a favorable microstructure. Two-phase composite films containing hard and soft phases were obtained when the Fe:Pt ratio increased. Under optimized processing conditions, composite films with energy products larger than 30 MG Oe at room temperature have been successfully produced.

  8. CMOS inverter design-hardened to the total dose effect

    SciTech Connect

    Roche, F.M.; Salager, L.

    1996-12-01

    This paper reports and discusses the experimental behavior of two inverter structures Rad-Hardened by Design to {sup 60}Co irradiation. The authors use the results on a set of basic circuits and transistors exposed to the same total doses as these structures to establish the effective formation conditions of the parasitic channel. Then this leakage evolution is related to the gate voltage history under irradiation. Finally, they take advantage of this intrinsic degradation property to propose a new Design Rad Hardened (DRH) cell. This structure considerably limits the Low Noise Margin degradation, helps to maintain the logic functionality with a High Output level and improves both the rad-tolerance and the static power consumption.

  9. Springback After the Lateral Bending of T-Section Rails of Work-Hardening Materials

    NASA Astrophysics Data System (ADS)

    Song, Youshuo; Yu, Zhonghua

    2013-11-01

    This paper studies the springback after the lateral bending of T-section rails, considering the work-hardening materials. A linear-hardening model and an elastic-plastic power-exponent hardening model of the material are adopted and compared with the real experimental stress-strain curve obtained from the uniaxial tension tests. The analytical formulas for the springback and residual curvatures are given. The numerical results indicate that the material hardening directly affects the accuracy of springback prediction compared with the experimental results. Besides, springback prediction is not sensitive to hardening parameters in the beginning of elastic-plastic bending deformation. Although there is an apparent yield stage in the true stress-strain curve, the adopted hardening models can achieve an allowable relative error, if hardening parameters are properly selected.

  10. Surface hardening of titanium alloys with melting depth controlled by heat sink

    DOEpatents

    Oden, Laurance L.; Turner, Paul C.

    1995-01-01

    A process for forming a hard surface coating on titanium alloys includes providing a piece of material containing titanium having at least a portion of one surface to be hardened. The piece having a portion of a surface to be hardened is contacted on the backside by a suitable heat sink such that the melting depth of said surface to be hardened may be controlled. A hardening material is then deposited as a slurry. Alternate methods of deposition include flame, arc, or plasma spraying, electrodeposition, vapor deposition, or any other deposition method known by those skilled in the art. The surface to be hardened is then selectively melted to the desired depth, dependent on the desired coating thickness, such that a molten pool is formed of the piece surface and the deposited hardening material. Upon cooling a hardened surface is formed.

  11. Global Precipitation Measurement Poster

    NASA Technical Reports Server (NTRS)

    Azarbarzin, Art

    2010-01-01

    This poster presents an overview of the Global Precipitation Measurement (GPM) constellation of satellites which are designed to measure the Earth's precipitation. It includes the schedule of launches for the various satellites in the constellation, and the coverage of the constellation, It also reviews the mission capabilities, and the mission science objectives.

  12. PRECIPITATION OF PROTACTINIUM

    DOEpatents

    Moore, R.L.

    1958-07-15

    An lmprovement in the separation of protactinium from aqueous nitric acid solutions is described. 1t covers the use of lead dioxide and tin dioxide as carrier precipitates for the protactinium. In carrying out the process, divalent lead or divalent tin is addcd to the solution and oxidized, causing formation of a carrier precipitate of lead dioxide or stannic oxide, respectively.

  13. A beam hardening correction method based on HL consistency

    NASA Astrophysics Data System (ADS)

    Mou, Xuanqin; Tang, Shaojie; Yu, Hengyong

    2006-08-01

    XCT with polychromatic tube spectrum causes artifact called beam hardening effect. The current correction in CT device is carried by apriori polynomial from water phantom experiment. This paper proposes a new beam hardening correction algorithm that the correction polynomial depends on the relativity of projection data in angles, which obeys Helgasson-Ludwig Consistency (HL Consistency). Firstly, a bi-polynomial is constructed to characterize the beam hardening effect based on the physical model of medical x-ray imaging. In this bi-polynomial, a factor r(γ,β) represents the ratio of the attenuation contributions caused by high density mass (bone, etc.) to low density mass (muscle, vessel, blood, soft tissue, fat, etc.) respectively in the projection angle β and fan angle γ. Secondly, let r(γ,β)=0, the bi-polynomial is degraded as a sole-polynomial. The coefficient of this polynomial can be calculated based on HL Consistency. Then, the primary correction is reached, which is also more efficient in theoretical than the correction method in current CT devices. Thirdly, based on the result of a normal CT reconstruction from the corrected projection data, r(γ,β) can be estimated. Fourthly, the coefficient of bi-polynomial can also be calculated based HL Consistency and the final correction are achieved. Experiments of circular cone beam CT indicate this method an excellent property. Correcting beam hardening effect based on HL Consistency, not only achieving a self-adaptive and more precise correction, but also getting rid of regular inconvenient water phantom experiments, will renovate the correction technique of current CT devices.

  14. Mechanism and technological particular features of thermomagnetic hardening

    NASA Astrophysics Data System (ADS)

    Borovskij, S. M.; Mukhin, V. S.

    1993-10-01

    The particular features of mechanism associated with piece hardening of gas-turbine engines are analyzed. This mechanism is connected with the change of conditions for phase equilibrium and kinetics of transformations. It is important to estimate the nature of the formation of new ferromagnetic centers at phase transitions, when permanent, pulsed, or periodic magnetic fields act. Two factors should be taken into account: the power effect of the magnetic field and the increase of 'magnetic segregation' of a source nonferromagnetic matrix.

  15. Hardening of commercial CMOS PROMs with polysilicon fusible links

    NASA Technical Reports Server (NTRS)

    Newman, W. H.; Rauchfuss, J. E.

    1985-01-01

    The method by which a commercial 4K CMOS PROM with polysilicon fuses was hardened and the feasibility of applying this method to a 16K PROM are presented. A description of the process and the necessary minor modifications to the original layout are given. The PROM circuit and discrete device characteristics over radiation to 1000K rad-Si are summarized. The dose rate sensitivity of the 4K PROMs is also presented.

  16. Structural influences on the work hardening behavior of aluminum

    SciTech Connect

    Chu, D.

    1994-12-01

    Effects of various grain and subgrain morphologies on low temperature work hardening of pure Al is studied using tensile tests. Plotting the work hardening rate as a function of true stress, the work hardening is separable into two distinct regimes. Both regimes are approximated by a line {Theta} = {Theta}{sub 0} {minus} K{sub 2}{sigma}, where {Theta}{sub 0} is theoretical work hardening rate at zero stress and K{sub 2} is related to dynamic recovery rate. The first or early deformation regime exhibits greater values of {Theta}{sub 0} and K{sub 2} and can extend up to the first 10% strain of tensile deformation. This early deformation regime is contingent on the existence of a pre-existent dislocation substructure from previous straining. The {Theta}{sub 0} and K{sub 2} associated with the early deformation regime are dependent on the strength and orientation of the pre-existent dislocation substructure relative to the new strain path. At high enough temperatures, this pre-existent dislocation substructure is annealed out, resulting in the near elimination of the early deformation regime. In comparison, the latter regime is dominated by the initial grain and/or subgrain morphology and exhibit lower values of {Theta}{sub 0} and K{sub 2}. The actual value of K{sub 2} in the latter regime is strongly dependent on the existence of a subgrain morphology. Recrystallized or well-annealed microstructures exhibit greater values of K{sub 2} than microstructures that remain partially or fully unrecrystallized. The higher K{sub 2} value is indicative of a more rapid dynamic recovery rate and a greater degree of strain relaxation. The ability to achieve a more relaxed state produces a low-energy cellular dislocation substructure upon deformation. The introduction of subgrains hinders the evolution of a low-energy dislocation cell network, giving way to a more random distribution of the dislocation density.

  17. Sequential circuit design for radiation hardened multiple voltage integrated circuits

    DOEpatents

    Clark, Lawrence T.; McIver, III, John K.

    2009-11-24

    The present invention includes a radiation hardened sequential circuit, such as a bistable circuit, flip-flop or other suitable design that presents substantial immunity to ionizing radiation while simultaneously maintaining a low operating voltage. In one embodiment, the circuit includes a plurality of logic elements that operate on relatively low voltage, and a master and slave latches each having storage elements that operate on a relatively high voltage.

  18. Single cell mechanics: stress stiffening and kinematic hardening.

    PubMed

    Fernández, Pablo; Ott, Albrecht

    2008-06-13

    Cell mechanical properties are fundamental to the organism but remain poorly understood. We report a comprehensive phenomenological framework for the complex rheology of single fibroblast cells: a superposition of elastic stiffening and viscoplastic kinematic hardening. Despite the complexity of the living cell, its mechanical properties can be cast into simple, well-defined rules. Our results reveal the key role of crosslink slippage in determining mechanical cell strength and robustness. PMID:18643547

  19. The Technology of Mould Steel for Online Pre-hardening

    NASA Astrophysics Data System (ADS)

    Zhu, Dongmei; Liu, Guoyong; Li, Mouwei; Zhang, Shaojun; Bian, Xinxiao; Wanglin; Quan, Wang; Dai, Jinguo; Xubin; Wei, Chaocheng; Cai, Lijuan; Liu, Zuofeng; Gong, Shichuang; An, Zhengang

    This article describes a production method of mould steel pre-hardening, and focus on the advantage of this method, The technical core of method is the variable frequency and variable amplitude pulse uniform high-precision temperature control, which achieved by using strong-medium-weak water cooling, gas-water cooling and gas mist cooling composite cooling control technology. Optimizing the cooling rate path is a good method of optimizing quenched organization and structure.

  20. Reduction of metal artifacts: beam hardening and photon starvation effects

    NASA Astrophysics Data System (ADS)

    Yadava, Girijesh K.; Pal, Debashish; Hsieh, Jiang

    2014-03-01

    The presence of metal-artifacts in CT imaging can obscure relevant anatomy and interfere with disease diagnosis. The cause and occurrence of metal-artifacts are primarily due to beam hardening, scatter, partial volume and photon starvation; however, the contribution to the artifacts from each of them depends on the type of hardware. A comparison of CT images obtained with different metallic hardware in various applications, along with acquisition and reconstruction parameters, helps understand methods for reducing or overcoming such artifacts. In this work, a metal beam hardening correction (BHC) and a projection-completion based metal artifact reduction (MAR) algorithms were developed, and applied on phantom and clinical CT scans with various metallic implants. Stainless-steel and Titanium were used to model and correct for metal beam hardening effect. In the MAR algorithm, the corrupted projection samples are replaced by the combination of original projections and in-painted data obtained by forward projecting a prior image. The data included spine fixation screws, hip-implants, dental-filling, and body extremity fixations, covering range of clinically used metal implants. Comparison of BHC and MAR on different metallic implants was used to characterize dominant source of the artifacts, and conceivable methods to overcome those. Results of the study indicate that beam hardening could be a dominant source of artifact in many spine and extremity fixations, whereas dental and hip implants could be dominant source of photon starvation. The BHC algorithm could significantly improve image quality in CT scans with metallic screws, whereas MAR algorithm could alleviate artifacts in hip-implants and dentalfillings.

  1. Elastic constant versus temperature behavior of three hardened maraging steels

    NASA Technical Reports Server (NTRS)

    Ledbetter, H. M.; Austin, M. W.

    1985-01-01

    Elastic constants of three maraging steels were determined by measuring ultrasonic velocities. Annealed steels show slightly lower bulk moduli and considerably lower shear moduli than hardened steels. All the elastic constants (Young's modulus, shear modulus, bulk modulus and Poisson's ratio) show regular temperature behavior between 76 and 400 K. Young's modulus and the shear modulus increase with increasing yield strength, but the bulk modulus and Poisson's ratio are relatively unchanged. Elastic anisotropy is quite small.

  2. Control technology for surface treatment of materials using induction hardening

    SciTech Connect

    Kelley, J.B.; Skocypec, R.D.

    1997-04-01

    In the industrial and automotive industries, induction case hardening is widely used to provide enhanced strength, wear resistance, and toughness in components made from medium and high carbon steels. The process uses significantly less energy than competing batch process, is environmentally benign, and is a very flexible in-line manufacturing process. As such, it can directly contribute to improved component reliability, and the manufacture of high-performance lightweight parts. However, induction hardening is not as widely used as it could be. Input material and unexplained process variations produce significant variation in product case depth and quality. This necessitates frequent inspection of product quality by destructive examination, creates higher than desired scrap rates, and causes de-rating of load stress sensitive components. In addition, process and tooling development are experience-based activities, accomplished by trial and error. This inhibits the use of induction hardening for new applications, and the resultant increase in energy efficiency in the industrial sectors. In FY96, a Cooperative Research and Development Agreement under the auspices of the Technology Transfer Initiative and the Partnership for a New Generation of Vehicles was completed. A multidisciplinary team from Sandia National Labs and Delphi Saginaw Steering Systems investigated the induction hardening by conducting research in the areas of process characterization, computational modeling, materials characterization, and high speed data acquisition and controller development. The goal was to demonstrate the feasibility of closed-loop control for a specific material, geometry, and process. Delphi Steering estimated annual savings of $2-3 million per year due to reduced scrap losses, inspection costs, and machine down time if reliable closed-loop control could be achieved. A factor of five improvement in process precision was demonstrated and is now operational on the factory floor.

  3. The Thorbex precipitation experiment

    NASA Astrophysics Data System (ADS)

    Nína Petersen, Guðrún; Ágústsson, Hálfdán; Ólafsson, Haraldur; Arason, Þórður

    2016-04-01

    During the autumn of 2014, precipitation was observed by a dense network of automatic raingauges covering a 243 m high and steep mountain, Þorbjörn, in the Reykjanes peninsula in SW-Iceland. The experiment is backed by continuous radar observations of winds and precipitation, radiosondes every 12 hours at the nearby Keflavik airport and a number of automatic weather stations. Some of the key results are: -The observations indicate that the average maximum rain over or close to the mountain maybe ~1.7 times the background rain. -Although the precipitation is only liquid, there seems to be great observation errors, likely due to strong winds. This calls for revision of the climatology of precipitation in Iceland and in other windy places. -The maximum wind loss and the spatial variability are of a similar magnitude. This complicates mapping of true precipitation.

  4. Precipitation and floodiness

    NASA Astrophysics Data System (ADS)

    Stephens, E.; Day, J. J.; Pappenberger, F.; Cloke, H.

    2015-12-01

    There are a number of factors that lead to nonlinearity between precipitation anomalies and flood hazard; this nonlinearity is a pertinent issue for applications that use a precipitation forecast as a proxy for imminent flood hazard. We assessed the degree of this nonlinearity for the first time using a recently developed global-scale hydrological model driven by the ERA-Interim/Land precipitation reanalysis (1980-2010). We introduced new indices to assess large-scale flood hazard, or floodiness, and quantified the link between monthly precipitation, river discharge, and floodiness anomalies at the global and regional scales. The results show that monthly floodiness is not well correlated with precipitation, therefore demonstrating the value of hydrometeorological systems for providing floodiness forecasts for decision-makers. A method is described for forecasting floodiness using the Global Flood Awareness System, building a climatology of regional floodiness from which to forecast floodiness anomalies out to 2 weeks.

  5. Description of full-range strain hardening behavior of steels.

    PubMed

    Li, Tao; Zheng, Jinyang; Chen, Zhiwei

    2016-01-01

    Mathematical expression describing plastic behavior of steels allows the execution of parametric studies for many purposes. Various formulas have been developed to characterize stress strain curves of steels. However, most of those formulas failed to describe accurately the strain hardening behavior of steels in the full range which shows various distinct stages. For this purpose, a new formula is developed based on the well-known Ramberg-Osgood formula to describe the full range strain hardening behavior of steels. Test results of all the six types of steels show a three-stage strain hardening behavior. The proposed formula can describe such behavior accurately in the full range using a single expression. The parameters of the formula can be obtained directly and easily through linear regression analysis. Excellent agreements with the test data are observed for all the steels tested. Furthermore, other formulas such as Ludwigson formula, Gardner formula, UGent formula are also applied for comparison. Finally, the proposed formula is considered to have wide suitability and high accuracy for all the steels tested. PMID:27563511

  6. Study on boring hardened materials dryly by ultrasonic vibration cutter

    NASA Astrophysics Data System (ADS)

    Zhang, Jiangzhong; Zhang, Heng; Zhang, Yue

    2011-05-01

    It has been one of the difficulties that high-precision hole on hardened materials is machined. The supersonic vibration boring acoustic system in the lathe in which supersonic wave energy is applied on tool is introduced to create pulse power on the cutting process. The separation vibration cutting is achieved by the pulse force. The comparative tests on boring accuracy and surface quality are carried. The quality of surface machined by this method is compared to that by grinding. This cutting is the green cutting. The boring process system is stability. Under the condition that the cutting speed is less than or equal to 1/3 the tool vibration speed, the cutting force is pulse force and the Cutting energy is of high concentration in time, space and direction. The pulse energy effects on the cutting unit in less than one ten-thousandth second. Traditional cutting of irregular movement elastic compression are eliminated. The cutting force is greatly reduced. The cutting temperature is at room temperature. The tool life is greatly increased. Shape precision and surface quality is greatly improved. The regulations of the ultrasonic vibration boring dry cutting of hardened material are also summarized. The test results show that the ultrasonic vibration cutting tool boring is of very superior cutting mechanism and is a high-precision deep-hole machining of hardened materials, efficient cutting methods.

  7. Study on boring hardened materials dryly by ultrasonic vibration cutter

    NASA Astrophysics Data System (ADS)

    Zhang, Jiangzhong; Zhang, Heng; Zhang, Yue

    2010-12-01

    It has been one of the difficulties that high-precision hole on hardened materials is machined. The supersonic vibration boring acoustic system in the lathe in which supersonic wave energy is applied on tool is introduced to create pulse power on the cutting process. The separation vibration cutting is achieved by the pulse force. The comparative tests on boring accuracy and surface quality are carried. The quality of surface machined by this method is compared to that by grinding. This cutting is the green cutting. The boring process system is stability. Under the condition that the cutting speed is less than or equal to 1/3 the tool vibration speed, the cutting force is pulse force and the Cutting energy is of high concentration in time, space and direction. The pulse energy effects on the cutting unit in less than one ten-thousandth second. Traditional cutting of irregular movement elastic compression are eliminated. The cutting force is greatly reduced. The cutting temperature is at room temperature. The tool life is greatly increased. Shape precision and surface quality is greatly improved. The regulations of the ultrasonic vibration boring dry cutting of hardened material are also summarized. The test results show that the ultrasonic vibration cutting tool boring is of very superior cutting mechanism and is a high-precision deep-hole machining of hardened materials, efficient cutting methods.

  8. Hardening of smooth pulsed laser deposited PMMA films by heating

    NASA Astrophysics Data System (ADS)

    Fuchs, Britta; Schlenkrich, Felix; Seyffarth, Susanne; Meschede, Andreas; Rotzoll, Robert; Vana, Philipp; Großmann, Peter; Mann, Klaus; Krebs, Hans-Ulrich

    2010-03-01

    Smooth poly(methyl methacrylate) (PMMA) films without any droplets were pulsed laser deposited at a wavelength of 248 nm and a laser fluence of 125 mJ/cm2. After deposition at room temperature, the films possess low universal hardness of only 3 N/mm2. Thermal treatments up to 200°C, either during deposition or afterwards, lead to film hardening up to values of 200 N/mm2. Using a combination of complementary methods, two main mechanisms could be made responsible for this temperature induced hardening effect well above the glass transition temperature of 102°C. The first process is induced by the evaporation of chain fragments and low molecular mass material, which are present in the film due to the ablation process, leading to an increase of the average molecular mass and thus to hardening. The second mechanism can be seen in partial cross-linking of the polymer film as soon as chain scission occurs at higher temperatures and the mobility and reactivity of the polymer material is high enough.

  9. A nanoscale duplex precipitation approach for improving the properties of Fe-base alloys

    SciTech Connect

    Zhang, Zhongwu; Liu, C T; Wang, Xun-Li; Wen, Y. R.; Fujita, T.; Hirata, A.; Chen, M.W.; Miller, Michael K; Chen, Guang; Chin, Bryan

    2013-01-01

    The precipitate size and number density are important factors for tailoring the mechanical behaviors of nanoscale precipitate-hardened alloys. However during thermal aging, the precipitate size and number density change leading to either poor strength or high strength but significantly reduced ductility. Here we demonstrate, by producing nanoprecipitates with unusual duplex structures in a composition-optimized multicomponent precipitation-hardened alloy, a unique approach to improve the stability of the alloy against the effects of thermal aging and consequently change in the mechanical properties. Our study provides compelling experimental evidence that these nanoscale precipitates consist of a duplex structures with a Cu-enriched bcc core that is partially encased by a B2-ordered Ni(Mn,Al) phase. This duplex structure enables the precipitate size and number density to be independently optimized, provides a more complex obstacle for dislocation movement due to the ordering and an additional interphase interface, and yields a high yield strength alloy without sacrificing the ductility.

  10. Comparative study of structure formation and mechanical behavior of age-hardened Ti–Nb–Zr and Ti–Nb–Ta shape memory alloys

    SciTech Connect

    Inaekyan, K.; Brailovski, V.; Prokoshkin, S.; Pushin, V.; Dubinskiy, S.; Sheremetyev, V.

    2015-05-15

    This work sets out to study the peculiar effects of aging treatment on the structure and mechanical behavior of cold-rolled and annealed biomedical Ti–21.8Nb–6.0Zr (TNZ) and Ti–19.7Nb–5.8Ta (TNT) (at.%) shape memory alloys by means of transmission electron microscopy, X-ray diffractometry, functional fatigue and thermomechanical testing techniques. Dissimilar effects of aging treatment on the mechanical behavior of Zr- and Ta-doped alloys are explained by the differences in the ω-phase formation rate, precipitate size, fraction and distribution, and by their effect on the alloys' critical stresses and transformation temperatures. Even short-time aging of the TNZ alloy leads to its drastic embrittlement caused by “overaging”. On the contrary, during aging of the TNT alloy, formation of finely dispersed ω-phase precipitates is gradual and controllable, which makes it possible to finely adjust the TNT alloy functional properties using precipitation hardening mechanisms. To create in this alloy nanosubgrained dislocation substructure containing highly-dispersed coherent nanosized ω-phase precipitates, the following optimum thermomechanical treatment is recommended: cold rolling (true strain 0.37), followed by post-deformation annealing (600 °C, 15–30 min) and age-hardening (300 °C, 30 min) thermal treatments. It is shown that in TNT alloy, pre-transition diffraction effects (diffuse reflections) can “mask” the β-phase substructure and morphology of secondary phases. - Highlights: • TNZ alloy is characterized by much higher ω-phase precipitation rate than TNT alloy. • Difference in precipitation rates is linked to the difference in Zr and Ta diffusion mobility. • Aging of nanosubgrained TNZ alloy worsens its properties irrespective of the aging time. • Aging time of nanosubgrained TNT alloy can be optimized to improve its properties.

  11. 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.

  12. Cloud and Precipitation Radar

    NASA Astrophysics Data System (ADS)

    Hagen, Martin; Höller, Hartmut; Schmidt, Kersten

    Precipitation or weather radar is an essential tool for research, diagnosis, and nowcasting of precipitation events like fronts or thunderstorms. Only with weather radar is it possible to gain insights into the three-dimensional structure of thunderstorms and to investigate processes like hail formation or tornado genesis. A number of different radar products are available to analyze the structure, dynamics and microphysics of precipitation systems. Cloud radars use short wavelengths to enable detection of small ice particles or cloud droplets. Their applications differ from weather radar as they are mostly orientated vertically, where different retrieval techniques can be applied.

  13. An extension of the Kocks-Mecking model of work hardening to include kinematic hardening and its application to solutes in ferrite

    NASA Astrophysics Data System (ADS)

    Bouaziz, O.; Barbier, D.; Embury, J. D.; Badinier, G.

    2013-01-01

    It is well known that the addition of a solute can change both work-hardening characteristics and yield stress; however, there are few available models which describe the role of a solute in relation to both the isotropic and kinematic aspects of work hardening. The current work extends the well-established approach of Kocks and Mecking to include the occurrence of cross slip and its dependence on solute content. The proposed model is compared with experimental data for the system Fe-Al by reference both to the observed work hardening in monotonic loading and the Bauschinger effect measured in reverse shear tests. The agreement between the model and the experimental data is satisfactory and suggests a new description of work hardening which includes a prediction of the ratio of isotropic and kinematic hardening for a given solute content.

  14. An Evaluation of the Corrosion and Mechanical Performance of Interstitially Surface-Hardened Stainless Steel

    NASA Astrophysics Data System (ADS)

    Jones, Jennifer L.; Koul, Michelle G.; Schubbe, Joel J.

    2014-06-01

    A surface hardening technique called "interstitial hardening" is commercially available, whereby interstitial carbon atoms are introduced into stainless steel surfaces without the formation of carbides. Surface hardening of machine elements such as impellors or fasteners would improve performance regarding cavitation and galling resistance, and has intensified interest in this process. However, there remains a need to characterize and validate the specific performance characteristics of the hardened materials. This paper describes experimental testing conducted on 316L stainless steel that has been surface hardened using available commercial techniques, using carbon as the interstitial atom. The corrosion performance of the hardened surface is assessed using electrochemical potentiodynamic testing to determine the breakdown potential in 3.5 wt.% NaCl solution to identify the most promising method. The hardness and thickness of the surface-hardened layer is characterized and compared using metallography and microhardness profiling. Corrosion fatigue and slow strain rate testing of untreated, hardened, and damaged, hardened surfaces exposed to ASTM seawater is conducted. Finally, critical galling stresses are determined and compared. Post-test examination of damage attempts to identify mechanisms of material failure and characterize how corrosion-assisted cracks initiate and grow in surface-hardened materials.

  15. Chemisorption And Precipitation Reactions

    EPA Science Inventory

    The transport and bioavailability of chemical components within soils is, in part, controlled by partitioning between solids and solution. General terms used to describe these partitioning reactions include chemisorption and precipitation. Chemisorption is inclusive of the suit...

  16. Precipitation Estimates for Hydroelectricity

    NASA Technical Reports Server (NTRS)

    Tapiador, Francisco J.; Hou, Arthur Y.; de Castro, Manuel; Checa, Ramiro; Cuartero, Fernando; Barros, Ana P.

    2011-01-01

    Hydroelectric plants require precise and timely estimates of rain, snow and other hydrometeors for operations. However, it is far from being a trivial task to measure and predict precipitation. This paper presents the linkages between precipitation science and hydroelectricity, and in doing so it provides insight into current research directions that are relevant for this renewable energy. Methods described include radars, disdrometers, satellites and numerical models. Two recent advances that have the potential of being highly beneficial for hydropower operations are featured: the Global Precipitation Measuring (GPM) mission, which represents an important leap forward in precipitation observations from space, and high performance computing (HPC) and grid technology, that allows building ensembles of numerical weather and climate models.

  17. My NASA Data Precipitation

    NASA Video Gallery

    This lesson has two activities that help students develop a basic understanding of the relationship between cloud type and the form of precipitation and the relationship between the amount of water...

  18. IMERG Global Precipitation Rates

    NASA Video Gallery

    NASA's Global Precipitation Measurement mission has produced its first global map of rainfall and snowfall. The GPM Core Observatory launched one year ago on Feb. 27, 2014 as a collaboration betwee...

  19. Hydride precipitation in titanium

    SciTech Connect

    Numakura, H.; Kowia, M.

    1984-10-01

    The crystal structure and morphology of hydride (deuteride) precipitates are investigated on ..cap alpha..-titanium specimens containing 1-3 at.% H or D by transmission electron microscopy. The hydride is found to have a face-centered tetragonal structure (c/a = 1.09) with an ordered arrangement of hydrogen, being isomorphous to ..gamma..-zirconium hydride. Two types of precipitation mode are observed with the habit planes (0110) and near (0225).

  20. Effect of prior oxidation on the creep behavior of NiAl-hardened austenitic steel

    NASA Astrophysics Data System (ADS)

    Satyanarayana, D. V. V.; Malakondaiah, G.; Sarma, D. S.

    2003-11-01

    The effect of prior oxidation at 1473 K on the creep behavior of an Fe-Ni-Cr-Al alloy, hardened by ordered NiAl precipitates, has been investigated at 873 K over a stress range of 275 to 450 MPa. The alloy in the as-electroslag remelted (ESR) as well as the ESR-plus-hot-worked conditions was considered. Prior oxidation causes creep strengthening in the Fe-Ni-Cr-Al alloy, resulting in a decrease in minimum creep rate and increase in time to rupture, in contrast to the observations reported on nickel-based superalloys. Creep strengthening is, however, accompanied by a significant reduction in creep ductility. Oxidation-induced creep strengthening in the current alloy can be attributed to the improved adherence of surface oxide caused by the presence of yttrium. An effective stress that incorporates the contributions of load transfer as well as substructural strengthening is used to account for the observed oxidation-induced creep strengthening. While creep strengthening is more pronounced in the ESR cast alloy, the loss in creep ductility is more intense in the ESR wrought alloy. Increasing the oxidation time beyond 1 hour has a minimal effect on creep strengthening of both the alloys, though it lowers significantly the creep ductility of the wrought alloy. The observed differences in creep behavior of the alloy in the two different conditions could be attributed to the differences in grain size as well as morphology and related oxidation-induced damage.

  1. Ultrasonic measurement of elastic moduli of 17-4 pH stainless steel and uranium -2 molybdenum from -40/sup 0/C to 800/sup 0/C

    SciTech Connect

    Gieske, J. H.

    1980-10-01

    Young's Modulus, shear modulus, and Poisson's ratio for 17-4 pH stainless steel and uranium -2 molybdenum are calculated from ultrasonic longitudinal and shear velocities determined from -40/sup 0/C to 800/sup 0/C. The ultrasonic velocities were determined at elevated temperatures using a through-transmission buffer rod arrangement. An indium-gallium slurry bond was used as an ultrasonic couplant between Cupernickel 10 alloy buffer rods and the specimen. Microstructural changes and phase transitions in the specimens are evident from the temperature dependence of the ultrasonic data. 10 figures, 3 tables.

  2. Method for increasing the rate of compressive strength gain in hardenable mixtures containing fly ash

    DOEpatents

    Liskowitz, John W.; Wecharatana, Methi; Jaturapitakkul, Chai; Cerkanowicz, deceased, Anthony E.

    1997-01-01

    The present invention relates to concrete, mortar and other hardenable mixtures comprising cement and fly ash for use in construction. The invention provides a method for increasing the rate of strength gain of a hardenable mixture containing fly ash by exposing the fly ash to an aqueous slurry of calcium oxide (lime) prior to its incorporation into the hardenable mixture. The invention further relates to such hardenable mixtures, e.g., concrete and mortar, that contain fly ash pre-reacted with calcium oxide. In particular, the fly ash is added to a slurry of calcium oxide in water, prior to incorporating the fly ash in a hardenable mixture. The hardenable mixture may be concrete or mortar. In a specific embodiment, mortar containing fly ash treated by exposure to an aqueous lime slurry are prepared and tested for compressive strength at early time points.

  3. Method for increasing the rate of compressive strength gain in hardenable mixtures containing fly ash

    DOEpatents

    Liskowitz, J.W.; Wecharatana, M.; Jaturapitakkul, C.; Cerkanowicz, A.E.

    1997-10-28

    The present invention relates to concrete, mortar and other hardenable mixtures comprising cement and fly ash for use in construction. The invention provides a method for increasing the rate of strength gain of a hardenable mixture containing fly ash by exposing the fly ash to an aqueous slurry of calcium oxide (lime) prior to its incorporation into the hardenable mixture. The invention further relates to such hardenable mixtures, e.g., concrete and mortar, that contain fly ash pre-reacted with calcium oxide. In particular, the fly ash is added to a slurry of calcium oxide in water, prior to incorporating the fly ash in a hardenable mixture. The hardenable mixture may be concrete or mortar. In a specific embodiment, mortar containing fly ash treated by exposure to an aqueous lime slurry are prepared and tested for compressive strength at early time points. 2 figs.

  4. Fatigue resistance of titanium alloy VT3-1 connection with surface work-hardening

    SciTech Connect

    Stepnov, M.N.; Agamirov, L.V.; Giatsintov, E.V.; Gus'kova, L.N.; Veitsman, M.G.

    1985-11-01

    The authors describe how surface work-hardening increases the endurance limit of smooth specimens of titanium alloy VT3-1 cut from bars by 25-30%. The range of the efficiency of strain-hardening by vibrational treatment and burnishing is 3-7%, the exact percentage depending on processing factors in each form of work-hardening. Work-hardening reduces scatter of fatigue characteristics, which enhances the effectiveness of the resulting strain-hardening with a decrease in the probability of fracture. Surface strain-hardening is recommended for alloy VT3-1, since it increases resistance to fatigue and reduces scatter of fatigue characteristics used in design.

  5. Case depth verification of hardened samples with Barkhausen noise sweeps

    SciTech Connect

    Santa-aho, Suvi; Vippola, Minnamari; Lepistö, Toivo; Hakanen, Merja; Sorsa, Aki; Leiviskä, Kauko

    2014-02-18

    An interesting topic of recent Barkhausen noise (BN) method studies is the application of the method to case depth evaluation of hardened components. The utilization of BN method for this purpose is based on the difference in the magnetic properties between the hardened case and the soft core. Thus, the detection of case depth with BN can be achieved. The measurements typically have been carried out by using low magnetizing frequencies which have deeper penetration to the ferromagnetic samples than the conventional BN measurement. However, the penetration depth is limited due to eddy current damping of the signal. We introduce here a newly found sweep measurement concept for the case depth evaluation. In this study sweep measurements were carried out with various magnetizing frequencies and magnetizing voltages to detect the effect of different frequency and voltage and their correspondence to the actual case depth values verified from destructive characterization. Also a BN measurement device that has an implemented sweep analysis option was utilised. The samples were either induction or case-hardened samples and sample geometry contained both rod samples and gear axle samples with different case depth values. Samples were also further characterized with Xray diffraction to study the residual stress state of the surface. The detailed data processing revealed that also other calculated features than the maximum slope division of the 1st derivative of the BN signal could hold the information about the case depth value of the samples. The sweep method was able to arrange the axles into correct order according to the case depth value even though the axles were used.

  6. Case depth verification of hardened samples with Barkhausen noise sweeps

    NASA Astrophysics Data System (ADS)

    Santa-aho, Suvi; Hakanen, Merja; Sorsa, Aki; Vippola, Minnamari; Leiviskä, Kauko; Lepistö, Toivo

    2014-02-01

    An interesting topic of recent Barkhausen noise (BN) method studies is the application of the method to case depth evaluation of hardened components. The utilization of BN method for this purpose is based on the difference in the magnetic properties between the hardened case and the soft core. Thus, the detection of case depth with BN can be achieved. The measurements typically have been carried out by using low magnetizing frequencies which have deeper penetration to the ferromagnetic samples than the conventional BN measurement. However, the penetration depth is limited due to eddy current damping of the signal. We introduce here a newly found sweep measurement concept for the case depth evaluation. In this study sweep measurements were carried out with various magnetizing frequencies and magnetizing voltages to detect the effect of different frequency and voltage and their correspondence to the actual case depth values verified from destructive characterization. Also a BN measurement device that has an implemented sweep analysis option was utilised. The samples were either induction or case-hardened samples and sample geometry contained both rod samples and gear axle samples with different case depth values. Samples were also further characterized with Xray diffraction to study the residual stress state of the surface. The detailed data processing revealed that also other calculated features than the maximum slope division of the 1st derivative of the BN signal could hold the information about the case depth value of the samples. The sweep method was able to arrange the axles into correct order according to the case depth value even though the axles were used.

  7. Radiation-Hardened Software for Space Flight Science Applications

    NASA Astrophysics Data System (ADS)

    Mehlitz, P. C.; Penix, J. J.; Markosian, L. Z.

    2005-12-01

    Hardware faults caused by radiation-induced Single Event Effects (SEEs) are a serious issue in space flight, especially affecting scientific missions in earth orbits crossing the poles or the South Atlantic Anomaly. Traditionally, SEEs are treated as a hardware problem, for example mitigated by radiation-hardened processors and shielding. Rad-hardened processors are expensive, exhibit a decade performance gap compared to COTS technology, have a larger form factor and require more power. Shielding is ineffective for high energy particles and increases launch weight. Hardware approaches cannot dynamically adapt protection levels for different radiation scenarios depending on solar activity and flight phase. Future hardware will exacerbate the problem due to higher chip densities and lower power levels. An alternative approach is to use software to mitigate SEEs. This "Radiation Hardened Software" (RHS) approach has two components: (1) RHS library and application design guidelines To increase robustness, we combine SEE countermeasures in three areas: prevention and detection; recovery; and reconfiguration. Prevention and detection includes an application- and heap-aware memory scanner, and dynamically adapted software Error Correction Codes to handle cache and multi-bit errors. Recovery mechanisms include exception firewalls and transaction-based software design patterns, to minimize data loss. Reconfiguration includes a heap manager to avoid damaged memory areas. (2) Software-based SEE Simulation Probabilistic effects require extensive simulation, with test environments that do not require original flight hardware and can simulate various SEE profiles. We use processor emulation software, interfaced to a debugger, to analyze SEE propagation and optimize RHS mechanisms. The simulator runs unmodified binary flight code, enables injecting randomized transient and permanent memory errors, providing execution traces and precise failure reproduction. The goal of RHS is to

  8. Ductility and work hardening in nano-sized metallic glasses

    SciTech Connect

    Chen, D. Z.; Gu, X. W.; An, Q.; Goddard, W. A.; Greer, J. R.

    2015-02-09

    In-situ nano-tensile experiments on 70 nm-diameter free-standing electroplated NiP metallic glass nanostructures reveal tensile true strains of ∼18%, an amount comparable to compositionally identical 100 nm-diameter focused ion beam samples and ∼3 times greater than 100 nm-diameter electroplated samples. Simultaneous in-situ observations and stress-strain data during post-elastic deformation reveal necking and work hardening, features uncharacteristic for metallic glasses. The evolution of free volume within molecular dynamics-simulated samples suggests a free surface-mediated relaxation mechanism in nano-sized metallic glasses.

  9. Substorm effects in auroral spectra. [electron spectrum hardening

    NASA Technical Reports Server (NTRS)

    Eather, R. H.; Mende, S. B.

    1973-01-01

    A substorm time parameter is defined and used to order a large body of photometric data obtained on aircraft expeditions at high latitudes. The statistical analysis demonstrates hardening of the electron spectrum at the time of substorm, and it is consistent with the accepted picture of poleward expansion of aurora at the time of substorm and curvature drift of substorm-injected electrons. These features are not evident from a similar analysis in terms of magnetic time. We conclude that the substorm time concept is a useful ordering parameter for auroral data.

  10. Hardening communication ports for survival in electrical overstress environments

    NASA Technical Reports Server (NTRS)

    Clark, O. Melville

    1991-01-01

    Greater attention is being focused on the protection of data I/O ports since both experience and lab tests have shown that components at these locations are extremely vulnerable to electrical overstress (EOS) in the form of transient voltages. Lightning and electrostatic discharge (ESD) are the major contributors to these failures; however, these losses can be prevented. Hardening against transient voltages at both the board level and system level has a proven record of improving reliability by orders of magnitude. The EOS threats, typical failure modes, and transient voltage mitigation techniques are reviewed. Case histories are also reviewed.

  11. Action Of Cement Hardening On Artificial Hip Joint Components

    NASA Astrophysics Data System (ADS)

    Roder, U.; Niess, N.; Plitz, W.

    1981-05-01

    Artificial acetabular cups loose their original shape and undergo deformations during implantation, caused by the polymerization shrinkage of the bone cement. In laboratory experiments, two acetabula of different material - both common in clinical use - were studied by holographic real-time interferometry during cement hardening. This method picks up characteristic features in the transient behaviour of the form changes. It is shown, that temperature, porosity and shrinkage of the cement has a large influence on the form of a polyethylene acetabulum, whereas there is only little effect on an acetabulum, made of alumina ceramic.

  12. Surface hardening of cutting elements agricultural machinery vibro arc plasma

    NASA Astrophysics Data System (ADS)

    Sharifullin, S. N.; Adigamov, N. R.; Adigamov, N. N.; Solovev, R. Y.; Arakcheeva, K. S.

    2016-01-01

    At present, the state technical policy aimed at the modernization of worn equipment, including agriculture, based on the use of high-performance technology called nanotechnology. By upgrading worn-out equipment meant restoring it with the achievement of the above parameters passport. The existing traditional technologies are not suitable for the repair of worn-out equipment modernization. This is especially true of imported equipment. Out here alone - is the use of high-performance technologies. In this paper, we consider the use of vibro arc plasma for surface hardening of cutting elements of agricultural machinery.

  13. Active radiation hardening technology for fiber-optic source

    NASA Astrophysics Data System (ADS)

    Yang, Yuanhong; Suo, Xinxin; Yang, Mingwei

    2013-09-01

    We demonstrated an active radiation hardening technology for fiber optic source developed for high performance fiber optic gyroscope. The radiation characteristic of erbium-doped fiber was studied experimentally. The radiation induced attenuation (RIA) at 980nm pump light was identified to be the main reason for the degradation and there was photo-bleaching effect in EDF too. A variable parameters control technology was proposed and taken to keep the 980nm and 1550nm light energy stable and high stability and radiation-resistance fiber source with gauss profile spectrum was realized .The source can stand against more than 50 krad (Si) total radiation dose.

  14. Development of a Pressure-Dependent Constitutive Model with Combined Multilinear Kinematic and Isotropic Hardening

    NASA Technical Reports Server (NTRS)

    Allen Phillip A.; Wilson, Christopher D.

    2003-01-01

    The development of a pressure-dependent constitutive model with combined multilinear kinematic and isotropic hardening is presented. The constitutive model is developed using the ABAQUS user material subroutine (UMAT). First the pressure-dependent plasticity model is derived. Following this, the combined bilinear and combined multilinear hardening equations are developed for von Mises plasticity theory. The hardening rule equations are then modified to include pressure dependency. The method for implementing the new constitutive model into ABAQUS is given.

  15. Surface hardening of steel by laser and electron beam. (Latest citations from Metadex). Published Search

    SciTech Connect

    1996-08-01

    The bibliography contains citations concerning electron beam hardening of steels and alloys. Among the materials surface hardened are carbon and alloy steels, aircraft spur gears, nitrocarburized steel, turbine blades, titanium-carbon steel, titanium, and rolling bearings. Effect of transformation plasticity on residual stress fields in laser surface hardening treatment is also examined.(Contains 50-250 citations and includes a subject term index and title list.) (Copyright NERAC, Inc. 1995)

  16. Surface hardening of steel by laser and electron beam. (Latest citations from METADEX). Published Search

    SciTech Connect

    Not Available

    1994-09-01

    The bibliography contains citations concerning electron beam hardening of steels and alloys. Among the materials surface hardened are carbon and alloy steels, aircraft spur gears, nitrocarburized steel, turbine blades, titanium-carbon steel, titanium, and rolling bearings. Effect of transformation plasticity on residual stress fields in laser surface hardening treatment is also examined. (Contains a minimum of 93 citations and includes a subject term index and title list.)

  17. Precipitating factors of insomnia.

    PubMed

    Bastien, Célyne H; Vallières, Annie; Morin, Charles M

    2004-01-01

    Insomnia is a prevalent health complaint whose onset is precipitated by a variety of factors. There is an important need to identify and describe these factors to improve our understanding of risk factors and the natural history of insomnia. This article is aimed at identifying and describing the types of precipitating factors related to the onset of insomnia. A total of 345 patients evaluated for insomnia at a sleep-disorders clinic completed a sleep survey and underwent a semistructured clinical interview. As part of the evaluation, the specific precipitating events related to the onset of insomnia were identified. Subsequently, these factors were categorized (work-school, family, physical or psychological health, or indeterminate), and their affective valence (negative, positive, or indeterminate) was coded. The most common precipitating factors of insomnia were related to family, health, and work-school events. Sixty-five percent of precipitating events had a negative valence. These events differed with the age of onset of insomnia but not with the gender of participants. These findings are useful to identify potential risk factors for insomnia and improve our understanding of the natural history of insomnia. PMID:15600224

  18. Constituted oxides/nitrides on nitriding 304, 430 and 17-4 PH stainless steel in salt baths over the temperature range 723 to 923 K

    NASA Astrophysics Data System (ADS)

    Shih, Teng-Shih; Huang, Yung-Sen; Chen, Chi-Fan

    2011-10-01

    The progressively developed oxides and nitrides that form on nitriding 304, 430 and 17-4 PH stainless steel are analysed by X-ray Diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS) in this study. The experimental results show that the Cr contents and matrix structures (ferrite, austenite and martensite) play an important role in forming FeCr 2O 4, Cr 2O 3 and Fe 2O 3 oxides as well as nitrides. After a short immersion time, oxides of Cr 2O 3 and FeCr 2O 4 form in nitride films on 304 stainless steel samples. Fe 2O 3 oxide will subsequently form following an increasing immersion time. For the 430 stainless steel, Cr 2O 3 predominately forms after a short dipping time which hinders the growth of the nitride layer. As a result, this sample had the thinnest nitride film of the three for a given immersion time. After the formation of oxides, both CrN and Cr 2N were detected near the surface of the nitride films of three samples while Cr 2N phases formed in the deeper zone. The greatest amount of Fe 2O 3 oxide among the three samples was obtained on the nitriding 17-4 PH stainless steel which also had a high intensity count of N 1s.

  19. Effects of the Treating Time on Microstructure and Erosion Corrosion Behavior of Salt-Bath-Nitrided 17-4PH Stainless Steel

    NASA Astrophysics Data System (ADS)

    Wang, Jun; Lin, Yuanhua; Li, Mingxing; Fan, Hongyuan; Zeng, Dezhi; Xiong, Ji

    2013-08-01

    The effects of salt-bath nitriding time on the microstructure, microhardness, and erosion-corrosion behavior of nitrided 17-4PH stainless steel at 703 K (430 °C) were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and erosion-corrosion testing. The experimental results revealed that the microstructure and phase constituents of the nitrided surface alloy are highly process condition dependent. When 17-4PH stainless steel was subjected to complex salt-bathing nitriding, the main phase of the nitrided layer was expanded martensite ( α`), expanded austenite (S), CrN, Fe4N, and Fe2N. The thickness of nitrided layers increased with the treating time. The salt-bath nitriding improves effectively the surface hardness. The maximum values measured from the treated surface are observed to be 1100 HV0.1 for 40 hours approximately, which is about 3.5 times as hard as the untreated material (309 HV0.1). Low-temperature nitriding can improve the erosion-corrosion resistance against two-phase flow. The sample nitrided for 4 hours has the best corrosion resistance.

  20. A radiation-hardened, computer for satellite applications

    SciTech Connect

    Gaona, J.I. Jr.

    1996-08-01

    This paper describes high reliability radiation hardened computers built by Sandia for application aboard DOE satellite programs requiring 32 bit processing. The computers highlight a radiation hardened (10 kGy(Si)) R3000 executing up to 10 million reduced instruction set instructions (RISC) per second (MIPS), a dual purpose module control bus used for real-time default and power management which allows for extended mission operation on as little as 1.2 watts, and a local area network capable of 480 Mbits/s. The central processing unit (CPU) is the NASA Goddard R3000 nicknamed the ``Mongoose or Mongoose 1``. The Sandia Satellite Computer (SSC) uses Rational`s Ada compiler, debugger, operating system kernel, and enhanced floating point emulation library targeted at the Mongoose. The SSC gives Sandia the capability of processing complex types of spacecraft attitude determination and control algorithms and of modifying programmed control laws via ground command. And in general, SSC offers end users the ability to process data onboard the spacecraft that would normally have been sent to the ground which allows reconsideration of traditional space-grounded partitioning options.

  1. DISCREPANT HARDENING OBSERVED IN COSMIC-RAY ELEMENTAL SPECTRA

    SciTech Connect

    Ahn, H. S.; Ganel, O.; Han, J. H.; Kim, K. C.; Lee, M. H.; Lutz, L.; Malinin, A.; Allison, P.; Beatty, J. J.; Bagliesi, M. G.; Bigongiari, G.; Maestro, P.; Marrocchesi, P. S.; Childers, J. T.; DuVernois, M. A.; Conklin, N. B.; Coutu, S.; Mognet, S. I.; Jeon, J. A.; Minnick, S.

    2010-05-01

    The balloon-borne Cosmic Ray Energetics And Mass experiment launched five times from Antarctica has achieved a cumulative flight duration of about 156 days above 99.5% of the atmosphere. The instrument is configured with complementary and redundant particle detectors designed to extend direct measurements of cosmic-ray composition to the highest energies practical with balloon flights. All elements from protons to iron nuclei are separated with excellent charge resolution. Here, we report results from the first two flights of {approx}70 days, which indicate hardening of the elemental spectra above {approx}200 GeV/nucleon and a spectral difference between the two most abundant species, protons and helium nuclei. These results challenge the view that cosmic-ray spectra are simple power laws below the so-called knee at {approx}10{sup 15} eV. This discrepant hardening may result from a relatively nearby source, or it could represent spectral concavity caused by interactions of cosmic rays with the accelerating shock. Other possible explanations should also be investigated.

  2. Dislocation Starvation and Exhaustion Hardening in Mo-alloy Nanofibers

    SciTech Connect

    Chisholm, Claire; Bei, Hongbin; Lowry, M. B.; Oh, Jason; Asif, S.A. Syed; Warren, O.; Shan, Zhiwei; George, Easo P; Minor, Andrew

    2012-01-01

    The evolution of defects in Mo alloy nanofibers with initial dislocation densities ranging from 0 to 1.6 1014 m2 were studied using an in situ push-to-pull device in conjunction with a nanoindenter in a transmission electron microscope. Digital image correlation was used to determine stress and strain in local areas of deformation. When they had no initial dislocations the Mo alloy nanofibers suffered sudden catastrophic elongation following elastic deformation to ultrahigh stresses. At the other extreme fibers with a high dislocation density underwent sustained homogeneous deformation after yielding at much lower stresses. Between these two extremes nanofibers with intermediate dislocation densities demonstrated a clear exhaustion hardening behavior, where the progressive exhaustion of dislocations and dislocation sources increases the stress required to drive plasticity. This is consistent with the idea that mechanical size effects ( smaller is stronger ) are due to the fact that nanostructures usually have fewer defects that can operate at lower stresses. By monitoring the evolution of stress locally we find that exhaustion hardening causes the stress in the nanofibers to surpass the critical stress predicted for self-multiplication, supporting a plasticity mechanism that has been hypothesized to account for the rapid strain softening observed in nanoscale bcc materials at high stresses.

  3. Folding and faulting of strain-hardening sedimentary rocks

    USGS Publications Warehouse

    Johnson, A.M.

    1980-01-01

    The question of whether single- or multi-layers of sedimentary rocks will fault or fold when subjected to layer-parallel shortening is investigated by means of the theory of elastic-plastic, strain-hardening materials, which should closely describe the properties of sedimentary rocks at high levels in the Earth's crust. The most attractive feature of the theory is that folding and faulting, intimately related in nature, are different responses of the same idealized material to different conditions. When single-layers of sedimentary rock behave much as strain-hardening materials they are unlikely to fold, rather they tend to fault, because contrasts in elasticity and strength properties of sedimentary rocks are low. Amplifications of folds in such materials are negligible whether contacts between layer and media are bonded or free to slip for single layers of dolomite, limestone, sandstone, or siltstone in media of shale. Multilayers of these same rocks fault rather than fold if contacts are bonded, but they fold readily if contacts between layers are frictionless, or have low yield strengths, for example due to high pore-water pressure. Faults may accompany the folds, occurring where compression is increased in cores of folds. Where there is predominant reverse faulting in sedimentary sequences, there probably were few structural units. ?? 1980.

  4. Analysis on sheet cyclic plastic deformation using mixed hardening model

    NASA Astrophysics Data System (ADS)

    Li, Qun; Jin, Miao; Yuxin, Zhu

    2013-05-01

    Treating the cyclic deformation problem of sheet flowing through drawbead as the object of the research, using HILL anisotropy yield criterion and mixed hardening model, the cyclic plastic deformation mechanism of sheet was studied, the deformation characteristics of sheet subjected to cyclic loads were revealed, and the influence of Bauschinger effect on stress-strain circulating relationship and the influence of bending neutral layer migration on the stress of sheet's intermediate integral point were analyzed as well. The effectiveness of the model was verified by experiments. The results of analysis were showed that the stress values influenced by Bauschinger effect were different at the yield point of reverse loading and the point of unloading during the cyclic deformation. The stress rate at the yield point of reverse loading and the point of unloading in different loading branches was also different. The stress-strain circulating relationship in different loading branches can be approximately treated as bilinear. The tangent modulus of each loading branch showed a significant downward trend as the times of the reverse loading increased. The tangent modulus calculated by the mixed hardening model after the second loading branch reduced to less than 21% of the first loading tangent modulus. Effected by the neutral layer migration, the stress-strain curve of integral point of sheet's intermediate layer showed alternating transition phenomenon of the tensile stress and compressive stress.

  5. Effects of residual stress on irradiation hardening in stainless steels

    NASA Astrophysics Data System (ADS)

    Okubo, N.; Miwa, Y.; Kondo, K.; Kaji, Y.

    2009-04-01

    Effects of residual stress on irradiation hardening were studied in advance for predicting irradiation assisted stress corrosion cracking. The specimens of SUS316 and SUS316L with several % plastic strains, which correspond to weld residual stress, were prepared by bending and keeping deformation under irradiation. Ion irradiations of 12 MeV Ni 3+ were performed at 330, 400 and 550 oC to 45 dpa. No bended specimen was simultaneously irradiated with the bended specimen. The residual stress was estimated by X-ray residual stress measurements before and after the irradiation. The micro-hardness was measured by using nanoindenter. The residual stress did not relax even for the case of the higher temperature aging at 500 oC for the same time of irradiation. The residual stress after ion irradiation up to high dpa, however, relaxed at these experimental temperatures. The irradiation hardening of stressed specimen was obviously lower than that of un-stressed one in case of SUS316L irradiated at 300 oC to 12 dpa.

  6. idRHa+ProMod - Rail Hardening Control System

    NASA Astrophysics Data System (ADS)

    Ferro, L.

    2016-03-01

    idRHa+ProMod is the process control system developed by Primetals Technologies to foresee the thermo-mechanical evolution and micro-structural composition of rail steels subjected to slack quenching into idRHa+ Rail Hardening equipments in a simulation environment. This tool can be used both off-line or in-line, giving the user the chance to test and study the best cooling strategies or letting the automatic control system free to adjust the proper cooling recipe. Optimization criteria have been tailored in order to determine the best cooling conditions according to the metallurgical requirements imposed by the main rail standards and also taking into account the elastoplastic bending phenomena occurring during all stages of the head hardening process. The computational core of idRHa+ProMod is a thermal finite element procedure coupled with special algorithms developed to work out the main thermo-physical properties of steel, to predict the non-isothermal austenite decomposition into all the relevant phases and subsequently to evaluate the amount of latent heat of transformation released, the compound thermal expansion coefficient and the amount of plastic deformation in the material. Air mist and air blades boundary conditions have been carefully investigated by means of pilot plant tests aimed to study the jet impingement on rail surfaces and the cooling efficiency at all working conditions. Heat transfer coefficients have been further checked and adjusted directly on field during commissioning. idRHa+ is a trademark of Primetals Technologies Italy Srl

  7. URANIUM PRECIPITATION PROCESS

    DOEpatents

    Thunaes, A.; Brown, E.A.; Smith, H.W.; Simard, R.

    1957-12-01

    A method for the recovery of uranium from sulfuric acid solutions is described. In the present process, sulfuric acid is added to the uranium bearing solution to bring the pH to between 1 and 1.8, preferably to about 1.4, and aluminum metal is then used as a reducing agent to convert hexavalent uranium to the tetravalent state. As the reaction proceeds, the pH rises amd a selective precipitation of uranium occurs resulting in a high grade precipitate. This process is an improvement over the process using metallic iron, in that metallic aluminum reacts less readily than metallic iron with sulfuric acid, thus avoiding consumption of the reducing agent and a raising of the pH without accomplishing the desired reduction of the hexavalent uranium in the solution. Another disadvantage to the use of iron is that positive ferric ions will precipitate with negative phosphate and arsenate ions at the pH range employed.

  8. FORMATION OF URANIUM PRECIPITATES

    DOEpatents

    Googin, J.M. Jr.

    1959-03-17

    A method is described for precipitation of uranium peroxide from uranium- containing solutions so as to obtain larger aggregates which facilitates washings decantations filtrations centrifugations and the like. The desired larger aggregate form is obtained by maintaining the pH of the solution in the approximate range of 1 to 3 and the temperature at about 25 deg C or below while carrytng out the precipitation. Then prior to removal of the precipitate a surface active sulfonated bicarboxyacids such as di-octyl sodium sulfo-succinates is incorporated in an anount of the order of 0.01 to 0.05 percent by weights and the slurry is allowed to ripen for about one-half hour at a temperatare below 10 deg C.

  9. Precipitation-Regulated Feedback

    NASA Astrophysics Data System (ADS)

    Voit, Mark

    2016-07-01

    Star formation in the central galaxies of galaxy clusters appears to be fueled by precipitation of cold clouds out of hot circumgalactic gas via thermal instability. I will present both observational and theoretical support for the precipitation mode in large galaxies and discuss how it can be implemented in cosmological simulations of galaxy evolution. Galaxy cluster cores are unique laboratories for studying the astrophysics of thermal instability and may be teaching us valuable lessons about how feedback works in galaxies spanning the entire mass spectrum.

  10. EFFECTS OF ACID PRECIPITATION

    EPA Science Inventory

    Recent reviews of available data indicate that precipitation in a large region of North America is highly acidic when its pH is compared with the expected pH value of 5.65 for pure rain water in equilibrium with CO2. A growing body of evidence suggests that acid rain is responsib...

  11. Global precipitation measurement (GPM)

    NASA Astrophysics Data System (ADS)

    Neeck, Steven P.; Flaming, Gilbert M.; Adams, W. James; Smith, Eric A.

    2001-12-01

    The National Aeronautics and Space Administration (NASA) is studying options for future space-based missions for the EOS Follow-on Era (post 2003), building upon the measurements made by Pre-EOS and EOS First Series Missions. One mission under consideration is the Global Precipitation Measurement (GPM), a cooperative venture of NASA, Japan, and other international partners. GPM will capitalize on the experience of the highly successful Tropical Rainfall Measurement Mission (TRMM). Its goal is to extend the measurement of rainfall to high latitudes with high temporal frequency, providing a global data set every three hours. A reference concept has been developed consisting of an improved TRMM-like primary satellite with precipitation radar and microwave radiometer to make detailed and accurate estimates of the precipitation structure and a constellation of small satellites flying compact microwave radiometers to provide the required temporal sampling of highly variable precipitation systems. Considering that DMSP spacecraft equipped with SSMIS microwave radiometers, successor NPOESS spacecraft equipped with CMIS microwave radiometers, and other relevant international systems are expected to be in operation during the timeframe of the reference concept, the total number of small satellites required to complete the constellation will be reduced. A nominal plan is to begin implementation in FY'03 with launches in 2007. NASA is presently engaged in advanced mission studies and advanced instrument technology development related to the mission.

  12. The Global Precipitation Mission

    NASA Technical Reports Server (NTRS)

    Braun, Scott; Kummerow, Christian

    2000-01-01

    The Global Precipitation Mission (GPM), expected to begin around 2006, is a follow-up to the Tropical Rainfall Measuring Mission (TRMM). Unlike TRMM, which primarily samples the tropics, GPM will sample both the tropics and mid-latitudes. The primary, or core, satellite will be a single, enhanced TRMM satellite that can quantify the 3-D spatial distributions of precipitation and its associated latent heat release. The core satellite will be complemented by a constellation of very small and inexpensive drones with passive microwave instruments that will sample the rainfall with sufficient frequency to be not only of climate interest, but also have local, short-term impacts by providing global rainfall coverage at approx. 3 h intervals. The data is expected to have substantial impact upon quantitative precipitation estimation/forecasting and data assimilation into global and mesoscale numerical models. Based upon previous studies of rainfall data assimilation, GPM is expected to lead to significant improvements in forecasts of extratropical and tropical cyclones. For example, GPM rainfall data can provide improved initialization of frontal systems over the Pacific and Atlantic Oceans. The purpose of this talk is to provide information about GPM to the USWRP (U.S. Weather Research Program) community and to discuss impacts on quantitative precipitation estimation/forecasting and data assimilation.

  13. Total Precipitable Water

    SciTech Connect

    2012-01-01

    The simulation was performed on 64K cores of Intrepid, running at 0.25 simulated-years-per-day and taking 25 million core-hours. This is the first simulation using both the CAM5 physics and the highly scalable spectral element dynamical core. The animation of Total Precipitable Water clearly shows hurricanes developing in the Atlantic and Pacific.

  14. [Chemical characteristics of 3-year atmospheric precipitation in summer, Taiyuan].

    PubMed

    Guo, Xiao-fang; Cui, Yang; Wang, Kai-yang; He, Qiu-sheng; Wang, Xin-ming

    2015-02-01

    The chemical characteristics of the precipitation in Taiyuan in summer of 2011-2013 were investigated. The results showed that the pH of precipitation varied from 4.63 to 8.02 with a volume-weighted mean of 5.19. The frequency of acid rain was 37.0%, 31.2% and 17.4%, respectively, in 2011-2013. SO4(2-) and NO3(-) were dominant anions in the precipitation, which accounted for 67.2% and 22.0% of the total anions, respectively. While Ca2+ and NH4+ were dominant cations in the precipitation, which accounted for 55.1% and 29.0% of the total cations, respectively. There were evident declining trends in the concentration of SO4(2-), NO3-, Ca2+ and NH4+ in the precipitation over the study period. The mean ratio of SO4(2-) to NO3(-) in summer precipitation was 3.02, indicating that the acid rain was of sulfuric-nitrous mixed type, however, NO3- was very important for the acidity of rain water. Neutralization factors (NF) were calculated to show that Ca2+ and NH4+ were the predominant neutralizers in rainwater samples, but Mg2+ could also not be negligible. The correlation analysis revealed that coal combustion was the dominant source of chemical composition of rainwater in summer of Taiyuan. The back trajectory analysis demonstrated that the air pollutants of Taiyuan were from the local plants and the coal coking plants in the southern Taiyuan basin. However, to improve the air quality in this city, both industrial emissions from thermal power plants and coal coking plants in Taiyuan basin need to be controlled. PMID:26031061

  15. Experimental study of self-compacted concrete in hardened state

    NASA Astrophysics Data System (ADS)

    Parra Costa, Carlos Jose

    The main aim of this work is to investigate the hardened behaviour of Self-Compacting Concrete (SCC). Self compacting Concrete is a special concrete that can flow in its gravity and fill in the formwork alone to its self-weight, passing through the bars and congested sections without the need of any internal or external vibration, while maintaining adequate homogeneity. SCC avoids most of the materials defects due to bleeding or segregation. With regard to its composition, SCC consists of the same components as traditional vibrated concrete (TC), but in different proportions. Thus, the high amount of superplasticizer and high powder content have to taken into account. The high workability of SCC does not allow to use traditional methods for measuring the fresh state properties, so new tests has developed (slump-flow, V-funnel, L-box, and others). The properties of the hardened SCC, which depend on the mix design, should be different from traditional concrete. In order to study the possible modifications of SCC hardened state properties, a review of the bibliography was done. The state of art was focused on the mechanical behaviour (compressive strength, tension strength and elastic modulus), on bond strength of reinforcement steel, and on material durability. The experimental program consisted in the production of two types of concretes: Self-Compacting Concrete and Traditional Concrete. Four different dosages was made with three different water/cement ratio and two strength types of Portland cement, in order to cover the ordinary strength used in construction. Based on this study it can be concluded that compressive strength of SCC and TC are similar (the differences are lesser than 10%), whereas the tensile strength of TC are up to 18% higher. The values of elastic modulus of both concrete are similar. On the other hand, in the ultimate state the bond strength of SCC and TC is similar, although SCC shows higher bond stiffness in the serviceability state (initial

  16. Some new results on irradiation characteristics of synthetic quartz crystals and their application to radiation hardening

    NASA Technical Reports Server (NTRS)

    Bahadur, H.; Parshad, R.

    1983-01-01

    The paper reports some new results on irradiation characteristics of synthetic quartz crystals and their application to radiation hardening. The present results show how the frequency shift in quartz crystals can be influenced by heat processing prior to irradiation and how this procedure can lead to radiation hardening for obtaining precise frequencies and time intervals from quartz oscillators in space.

  17. Strain hardening during mechanical twining and dislocation channeling in irradiated 316 stainless steels

    SciTech Connect

    Byun, Thak Sang; Hashimoto, Naoyuki

    2007-01-01

    Localized deformation mechanisms and strain-hardening behaviors in irradiated 316 and 316LN stainless steels were investigated, and a theoretical model was proposed to explain the linear strain-hardening behavior during the localized deformation. After low temperature irradiation to significant doses the deformation microstructure changed from dislocation tangles to channels or to mechanical twins. It was also observed that irradiation hardening straightened gliding dislocations and increased the tendency for forming pileups. Regardless of these microstructural changes, the strain-hardening behavior was relatively insensitive to the irradiation. This dose-independent strain-hardening rate resulted in dose independence of the true stress parameters such as the plastic instability stress and true fracture stress. In the proposed model, the long-range back stress was formulated as a function of the number of pileup dislocations per slip band and the number of slip bands in a grain. The calculation results confirmed the experimental observation that strain-hardening rate was insensitive to the change in deformation mechanism because the long-range back stress hardening became as high as the hardening by tangled dislocations.

  18. The Effect of Hardenability Variation on Phase Transformation of Spiral Bevel Gear in Quenching Process

    NASA Astrophysics Data System (ADS)

    Zhang, Yingtao; Shi, Wankai; Yang, Lin; Gu, Zhifei; Li, Zhichao

    2016-05-01

    The hardenability of gear steel is dependent on the composition of alloying elements and is one of important criteria to assess process of phase transformation. The variation of hardenability has to be considered in control of the microstructures and distortion during gear quenching. In this paper, the quantitative effect of hardenability has been investigated on phase transformations of spiral bevel gears in die quenching. The hardenability deviation of 22CrMoH steel was assessed by using Jominy test. The dilatometry experiments were conducted to build phase transformation kinetic models for steels with low and high hardenability, respectively. The complete die quenching process of spiral bevel gear was modeled to reveal the significant difference on microstructures and temperature history with variation of hardenability. The final microstructures of the gear are martensite in surface layer after quenching process. There are bainite inside the gear tooth and the mixture of bainite and ferrite inside gear for the gear with low hardenability. The microstructure is bainite inside the gear with high hardenability.

  19. Consistency condition for isotropic-kinematic hardening of anisotropic yield functions

    NASA Astrophysics Data System (ADS)

    Chung, Kwansoo

    2013-05-01

    For the combined type isotropic-kinematic hardening law to account for the Bauschinger, transient and permanent softening behaviors observed in reverse loading, formulations have been initially developed for isotropic yield functions, mainly based on the von Mises criterion, and then later extended for anisotropic yield functions. Among the efforts to introduce anisotropic yield functions to the combined type hardening formulation, however, some inconsistency has been encountered in manipulating the kinematic hardening law, especially for the nonlinear type law, even though their von Mises yield function versions have been consistent. Therefore, theoretical clarification and clearance of such inconsistency were attempted in this work by imposing the following (consistency) condition: the combined type hardening law is expected to behave the same as the full isotropic hardening for monotonously proportional loading, regardless of (anisotropic) yield functions coupled with the combined type hardening law. An example to account for the anisotropic hardening of an anisotropic yield function utilizing the combined type hardening law, but for which the consistency condition was partially released, was also demonstrated.

  20. The Effect of Hardenability Variation on Phase Transformation of Spiral Bevel Gear in Quenching Process

    NASA Astrophysics Data System (ADS)

    Zhang, Yingtao; Shi, Wankai; Yang, Lin; Gu, Zhifei; Li, Zhichao

    2016-07-01

    The hardenability of gear steel is dependent on the composition of alloying elements and is one of important criteria to assess process of phase transformation. The variation of hardenability has to be considered in control of the microstructures and distortion during gear quenching. In this paper, the quantitative effect of hardenability has been investigated on phase transformations of spiral bevel gears in die quenching. The hardenability deviation of 22CrMoH steel was assessed by using Jominy test. The dilatometry experiments were conducted to build phase transformation kinetic models for steels with low and high hardenability, respectively. The complete die quenching process of spiral bevel gear was modeled to reveal the significant difference on microstructures and temperature history with variation of hardenability. The final microstructures of the gear are martensite in surface layer after quenching process. There are bainite inside the gear tooth and the mixture of bainite and ferrite inside gear for the gear with low hardenability. The microstructure is bainite inside the gear with high hardenability.

  1. Computational Kinetics Simulation of Precipitation and Dissolution of Gamma Prime ( γ') in Heat Treating and Welding of 718plus Superalloy

    NASA Astrophysics Data System (ADS)

    Wang, Bo; Zhang, Fan; Cao, Weisheng; Chen, Shuanglin; Kou, Sindo

    2015-01-01

    The evolution of the strengthening precipitate in a precipitation-hardening alloy, such as the gamma prime ( γ') phase in Ni-base superalloys, during heat treating and welding can affect the resultant mechanical properties significantly. Computational kinetics simulation can be a useful tool for understanding and controlling of such evolution. The present study was conducted to simulate the γ' precipitation and dissolution during aging and welding of the recently developed Ni-base superalloy 718plus using the PanPrecipitation module of the Pandat software along with available thermodynamic and kinetic databases. The purpose was to demonstrate the application of such software and databases to materials processing including heat treating and welding. The variations in the volume fraction, average precipitation size, and number density of γ' with time during aging and welding were calculated. The calculated results under aging condition agreed well with the available experimental data, while those under welding also predicted the correct trend.

  2. Precipitation Indices Low Countries

    NASA Astrophysics Data System (ADS)

    van Engelen, A. F. V.; Ynsen, F.; Buisman, J.; van der Schrier, G.

    2009-09-01

    Since 1995, KNMI published a series of books(1), presenting an annual reconstruction of weather and climate in the Low Countries, covering the period AD 763-present, or roughly, the last millennium. The reconstructions are based on the interpretation of documentary sources predominantly and comparison with other proxies and instrumental observations. The series also comprises a number of classifications. Amongst them annual classifications for winter and summer temperature and for winter and summer dryness-wetness. The classification of temperature have been reworked into peer reviewed (2) series (AD 1000-present) of seasonal temperatures and temperature indices, the so called LCT (Low Countries Temperature) series, now incorporated in the Millennium databases. Recently we started a study to convert the dryness-wetness classifications into a series of precipitation; the so called LCP (Low Countries Precipitation) series. A brief outline is given here of the applied methodology and preliminary results. The WMO definition for meteorological drought has been followed being that a period is called wet respectively dry when the amount of precipitation is considerable more respectively less than usual (normal). To gain a more quantitative insight for four locations, geographically spread over the Low Countries area (De Bilt, Vlissingen, Maastricht and Uccle), we analysed the statistics of daily precipitation series, covering the period 1900-present. This brought us to the following definition, valid for the Low Countries: A period is considered as (very) dry respectively (very) wet if over a continuous period of at least 60 days (~two months) cq 90 days (~three months) on at least two out of the four locations 50% less resp. 50% more than the normal amount for the location (based on the 1961-1990 normal period) has been measured. This results into the following classification into five drought classes hat could be applied to non instrumental observations: Very wet period

  3. New distortional hardening model capable of predicting eight ears for textured aluminum sheet

    SciTech Connect

    Yoon, J. H.; Cazacu, O.; Yoon, J. W.; Dick, R. E.

    2011-05-04

    The effects of the anisotropy evolution and of the directionality in hardening on the predictions of the earing profile of a strongly textured aluminum alloy are investigated using a new distortional hardening model that incorporates multiple hardening curves corresponding to uniaxial tension along several orientations with respect to the rolling direction, and to biaxial tension. Yielding is described using a form of CPB06ex2 yield function (Plunkett et al. (2008)) which is tailored for metals with no tension-compression asymmetry. It is shown that even if directional hardening and its evolution are neglected, this yield function predicts a cup with eight ears as was observed experimentally. However, directional hardening can be of considerable importance for improved accuracy in prediction of the non-uniformity of the cup height profile.

  4. Evaluation of Springback for DP980 S Rail Using Anisotropic Hardening Models

    NASA Astrophysics Data System (ADS)

    Choi, Jisik; Lee, Jinwoo; Bae, Gihyun; Barlat, Frederic; Lee, Myoung-Gyu

    2016-07-01

    The effect of anisotropic hardening models on springback of an S-rail part was investigated. Two advanced constitutive models based on distortional and kinematic hardening, which captured the Bauschinger effect, transient hardening, and permanent softening during strain path change, were implemented in a finite element (FE) code. In-plane compression-tension tests were performed to identify the model parameters. The springback of the S-rail after forming a 980 MPa dual-phase steel sheet sample was measured and analyzed using different hardening models. The comparison between experimental and FE results demonstrated that the advanced anisotropic hardening models, which are particularly suitable for non-proportional loading, significantly improved the springback prediction capability of an advanced high strength steel.

  5. A radiation-hardened 16/32-bit microprocessor

    SciTech Connect

    Hass, K.J.; Treece, R.K.; Giddings, A.E. )

    1989-12-01

    This paper reports on the development of single chip radiation-hardened 16/32-bit microprocessor. This device, the SA3300, is an emulation of National Semiconductor's NS32C016. The SA3300 is designed to withstand high levels of ionizing radiation and is resistant to single event upset (SEU) caused by heavy ions. New techniques were used to improve immunity to SEU effects in combinational logic. The authors' testing has demonstrated that the SA3300 is functional after a total gamma dose of 5 Mrad(Si). The device does not latch up from SEU, and parts without SEU resistors have an SEU linear energy transfer (LET) upset threshold greater than 28 MeV/mg/cm{sup 2}.

  6. Method of forming a hardened surface on a substrate

    DOEpatents

    Branagan, Daniel J.

    2010-08-31

    The invention includes a method of producing a hard metallic material by forming a mixture containing at least 55% iron and at least one of B, C, Si and P. The mixture is formed into an alloy and cooled to form a metallic material having a hardness of greater than about 9.2 GPa. The invention includes a method of forming a wire by combining a metal strip and a powder. The metal strip and the powder are rolled to form a wire containing at least 55% iron and from two to seven additional elements including at least one of C, Si and B. The invention also includes a method of forming a hardened surface on a substrate by processing a solid mass to form a powder, applying the powder to a surface to form a layer containing metallic glass, and converting the glass to a crystalline material having a nanocrystalline grain size.

  7. Hydrogen effects on the age hardening behavior of 2024 aluminum

    NASA Technical Reports Server (NTRS)

    Wagner, J. A.; Louthan, M. R., Jr.; Sisson, R. D., Jr.

    1986-01-01

    It has been found that the fatigue crack growth rate in aluminum alloys increases significantly in the presence of moisture. This phenomenon along with a moisture effect observed in another context has been attributed to 'embrittlement' of the aluminum by absorbed hydrogen generated by the reaction of moisture with freshly exposed aluminum. A description is given of a number of age hardening experiments involving 2024 aluminum. These experiments show that a mechanism related to the segregation of absorbed hydrogen to the coherent theta-double-prime interfaces may account for the observed reduction in fatigue life. It is pointed out that this segregation promotes a loss of coherency in the hydrogen rich region at a fatigue crack tip. Subsequently, the loss of coherency causes local softening and reduces fatigue life.

  8. Modelling of temperature evolution on metals during laser hardening process

    NASA Astrophysics Data System (ADS)

    Yánez, A.; Álvarez, J. C.; López, A. J.; Nicolás, G.; Pérez, J. A.; Ramil, A.; Saavedra, E.

    2002-01-01

    To achieve a precise and controlled laser process, an exhaustive analysis of the thermal behaviour of the material is necessary. In the present paper, a numerical simulation of the laser hardening process has been developed using both analytical solutions and the finite element code ANSYS™ to solve the heat transfer equation inside the treated material. The knowledge of the thermal cycles has enabled suitable processing parameters to be ascertained thus improving surface properties when metallic alloys have been irradiated. A simpler analytical method is also used to determine the mentioned parameters more quickly. This general purpose method has been applied to a specific experimental situation, namely the treatment of cylindrical pieces used in a multistage pump rotary jacket.

  9. Dislocation mean free paths and strain hardening of crystals.

    PubMed

    Devincre, B; Hoc, T; Kubin, L

    2008-06-27

    Predicting the strain hardening properties of crystals constitutes a long-standing challenge for dislocation theory. The main difficulty resides in the integration of dislocation processes through a wide range of time and length scales, up to macroscopic dimensions. In the present multiscale approach, dislocation dynamics simulations are used to establish a dislocation-based continuum model incorporating discrete and intermittent aspects of plastic flow. This is performed through the modeling of a key quantity, the mean free path of dislocations. The model is then integrated at the scale of bulk crystals, which allows for the detailed reproduction of the complex deformation curves of face-centered cubic crystals. Because of its predictive ability, the proposed framework has a large potential for further applications. PMID:18583605

  10. Experience in calibrating the double-hardening constitutive model Monot

    NASA Astrophysics Data System (ADS)

    Hicks, M. A.

    2003-11-01

    The Monot double-hardening soil model has previously been implemented within a general purpose finite element algorithm, and used in the analysis of numerous practical problems. This paper reviews experience gained in calibrating Monot to laboratory data and demonstrates how the calibration process may be simplified without detriment to the range of behaviours modelled. It describes Monot's principal features, important governing equations and various calibration methods, including strategies for overconsolidated, cemented and cohesive soils. Based on a critical review of over 30 previous Monot calibrations, for sands and other geomaterials, trends in parameter values have been identified, enabling parameters to be categorized according to their relative importance. It is shown that, for most practical purposes, a maximum of only 5 parameters is needed; for the remaining parameters, standard default values are suggested. Hence, the advanced stress-strain modelling offered by Monot is attainable with a similar number of parameters as would be needed for some simpler, less versatile, models. Copyright

  11. Topographies of plasma-hardened surfaces of poly(dimethylsiloxane)

    SciTech Connect

    Goerrn, Patrick; Wagner, Sigurd

    2010-11-15

    We studied the formation of surface layers hardened by plasma-enhanced oxidation of the silicone elastomer poly(dimethylsiloxane). We explored the largest parameter space surveyed to date. The surface layers may wrinkle, crack, or both, under conditions that at times are controlled by design, but more often have been discovered by trial-and-error. We find four distinct topographies: flat/wrinkled/cracked/cracked and wrinkled. Each topography is clearly separated in the space of plasma dose versus plasma pressure. We analyzed wrinkle amplitude and wavelength by atomic force microscopy in the tapping mode. From these dimensions we calculated the elastic modulus and thickness of the hard surface layer, and inferred a graded hardness, by employing a modified theoretical model. Our main result is the identification of the parameters under which the technologically important pure wrinkled, crack-free topography is obtained.

  12. Gamma prime hardened nickel-iron based superalloy

    DOEpatents

    Korenko, Michael K.

    1978-01-01

    A low swelling, gamma prime hardened nickel-iron base superalloy useful for fast reactor duct and cladding applications is described having from about 7.0 to about 10.5 weight percent (wt%) chromium, from about 24 to about 35 wt% nickel, from about 1.7 to about 2.5 wt% titanium, from about 0.3 to about 1.0 wt% aluminum, from about 2.0 to about 3.3 wt% molybdenum, from about 0.05 to about 1.0 wt% silicon, from about 0.03 to about 0.06 wt% carbon, a maximum of about 2 wt% manganese, and the balance iron.

  13. Analysis of fracture toughness of explosion-hardened martensitic steel

    NASA Astrophysics Data System (ADS)

    Moskvitina, L. V.

    2015-10-01

    In this work we study a shift of the following nonlinear states: tempering + abatement + 10 GPa shock loading + welding thermocycle. As a result the self-organized HAZ metal structure with elements of self-similarity on different scales is found. The fractal analysis shows how formed defects affect the HAZ metal hardness of 14H2GMR steel with the martensitic structure of static fracture. The statistical analysis of stereometric parameters of fracture shows a higher energy intensity of static fracture in specimens treated by explosion. The multifractal analysis reveals hardness of the grid dislocation structure induced by explosion in the air-hardening zone. The homogeneity of the dislocation structure related to carbides increases the resistance of HAZ metal of static fracture.

  14. Optical moments and the art of dispersion hardening

    NASA Astrophysics Data System (ADS)

    Sievers, A. J.; Noh, T. W.; Page, J. B.

    1994-06-01

    For many years composite structures have been the building blocks of materials with specialized mechanical properties, but only recently have related ideas been used successfully to develop new optical materials. A particularly simple example, hot pressed zinc sulfide dispersion hardened with diamond particles, has turned out to be extremely useful for identifying the important optical moments underlying the dynamical properties of all transparent composites and complex dielectrics. One result has been the discovery of a generalized Lyddane-Sachs-Teller relation for solids and liquids. When the characteristic frequencies of small disordered dielectric particles are described in terms of optical moments of the appropriate response functions, generalized Szigeti and Clausius-Mossotti expressions follow.

  15. Effective mineral coatings for hardening the surface of metallic materials

    NASA Astrophysics Data System (ADS)

    Kislov, S. V.; Kislov, V. G.; Skazochkin, A. V.; Bondarenko, G. G.; Tikhonov, A. N.

    2015-07-01

    The structural changes that occur in the surface and surface layers of steel 20Kh13 and titanium alloy PT-3V (Russian designation) samples after each stage of hardening due to a formed mineral surface layer are studied by optical microscopy, transmission electron microscopy, and scanning electron microscopy. Electric spark alloying, pressing, and ultrasonic processing are used to reach the effect of volume compression of the base metal and the mineral in the plastic deformation zone. As a result, applied mineral particles concentrate in preliminarily created microvoids in a thin surface layer. The surface layer thus modified acquires a high hardness and wear resistance. Durometry shows that the hardness of the processed sample surfaces increases more than twofold. Therefore, the developed technology of creating a mineral coating can be used to increase the tribological properties of the surfaces of the parts, units, and mechanisms of turbine, pump, and mining equipment, which undergo intense wear during operation.

  16. Irradiation-induced precipitation and mechanical properties of vanadium alloys at <430 C

    SciTech Connect

    Chung, H.M.; Gazda, J.; Smith, D.L.

    1998-09-01

    Recent attention to V-base alloys has focused on the effect of low-temperature (<430 C) irradiation on tensile and impact properties of V-4Cr-4Ti. In previous studies, dislocation channeling, which causes flow localization and severe loss of work-hardening capability, has been attributed to dense, irradiation-induced precipitation of very fine particles. However, efforts to identify the precipitates were unsuccessful until now. In this study, analysis by transmission electron microscopy (TEM) was conducted on unalloyed V, V-5Ti, V-3Ti-1Si, and V-4Cr-4Ti specimens that were irradiated at <430 C in conventional and dynamic helium charging experiments. By means of dark-field imaging and selected-area-diffraction analysis, the characteristic precipitates were identified to be (V,Ti{sub 1{minus}x})(C,O,N). In V-3Ti-1Si, precipitation of (V,Ti{sub 1{minus}x})(C,O,N) was negligible at <430 C, and as a result, dislocation channeling did not occur and work-hardening capability was high.

  17. Effects of SiC whiskers and particles on precipitation in aluminum matrix composites

    NASA Astrophysics Data System (ADS)

    Papazian, John M.

    1988-12-01

    The age-hardening precipitation reactions in aluminum matrix composites reinforced with discontinuous SiC were studied using a calorimetric technique. Composites fabricated with 2124, 2219, 6061, and 7475 alloy matrices were obtained from commercial sources along with unreinforced control materials fabricated in a similar manner. The 7475 materials were made by a casting process while the others were made by powder metallurgy: the SiC reinforcement was in the form of whiskers or particulate. It was found that the overall age-hardening sequence of the alloy was not changed by the addition of SiC, but that the volume fractions of various phases and the precipitation kinetics were substantially modified. Precipitation and dissolution kinetics were generally accelerated. A substantial portion of this acceleration was found to be due to the powder metallurgy process employed to make the composites, but the formation kinetics of some particular precipitate phases were also strongly affected by the presence of SiC. It was observed that the volume fraction of GP zones able to form in the SiC containing materials was significantly reduced. The presence of SiC particles also caused normally quench insensitive materials such as 6061 to become quench sensitive. The microstructural origins of these effects are discussed.

  18. [Hardened anodized aluminum as a replacement material for bracket manufacture].

    PubMed

    Fischer-Brandies, H; Bönhoff, M

    1994-12-01

    Attention has been repeatedly drawn to the problem of corrosion and the risk of allergic reaction to nickel resulting from the use of stainless steel brackets. In the search for a suitable alternative, manufacturers have turned to thin coating technology using hardened anodized aluminium. Applying resistance to corrosion and abrasion as the criteria to be met, they have selected aluminium alloy type 6082 as the material of choice. Purpose of this study is to examine the physical suitability of this material. Using the above noted alloy, 60 prototype brackets were made with a hardened anodized surface. They were then subjected to the following 3 stress tests: first an abrasion test using a tooth polishing machine, second, a deformation test using a device designed to simulate torque movement, and, third, a corrosion test. The effects on the brackets resulting from the three types of stress were evaluated by light microscopy. A quantitative analysis of the corrosion test was performed by ICP spectrometry. The control group consisted of conventional stainless steel brackets. The light microscopic analysis revealed no evidence of surface damage or signs of deformation in the prototype brackets. The steel brackets, on the other hand, showed clear signs of wear and corrosion. The quantitative analysis of the corrosion solution revealed metallic ion wear of 1.75 ng x mm-2 x h-1 for the prototypes subjected to abrasion. The steel brackets showed at a factor of around 104.6 metallic ion wear of 183 ng x mm-2 x h-1. In addition to this, no Ni ions were found in the corrosion solution of the prototype brackets.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7851828

  19. Radiation Effects and Hardening Techniques for Spacecraft Microelectronics

    NASA Astrophysics Data System (ADS)

    Gambles, J. W.; Maki, G. K.

    2002-01-01

    The natural radiation from the Van Allen belts, solar flares, and cosmic rays found outside of the protection of the earth's atmosphere can produce deleterious effects on microelectronics used in space systems. Historically civil space agencies and the commercial satellite industry have been able to utilize components produced in special radiation hardened fabrication process foundries that were developed during the 1970s and 1980s under sponsorship of the Departments of Defense (DoD) and Energy (DoE). In the post--cold war world the DoD and DoE push to advance the rad--hard processes has waned. Today the available rad--hard components lag two-plus technology node generations behind state- of-the-art commercial technologies. As a result space craft designers face a large performance gap when trying to utilize available rad--hard components. Compounding the performance gap problems, rad--hard components are becoming increasingly harder to get. Faced with the economic pitfalls associated with low demand versus the ever increasing investment required for integrated circuit manufacturing equipment most sources of rad--hard parts have simply exited this market in recent years, leaving only two domestic US suppliers of digital rad--hard components. This paper summarizes the radiation induced mechanisms that can cause digital microelectronics to fail in space, techniques that can be applied to mitigate these failure mechanisms, and ground based testing used to validate radiation hardness/tolerance. The radiation hardening techniques can be broken down into two classes, Hardness By Process (HBP) and Hardness By Design (HBD). Fortunately many HBD techniques can be applied to commercial fabrication processes providing space craft designer with radiation tolerant Application Specific Integrated Circuits (ASICs) that can bridge the performance gap between the special HBP foundries and the commercial state-of-the-art performance.

  20. Development of a Press-Hardened Steel Suitable for Thin Slab Direct Rolling Processing

    NASA Astrophysics Data System (ADS)

    Lee, Jewoong; De Cooman, Bruno C.

    2015-01-01

    The thin slab casting and direct rolling process is a hot-rolled strip production method which has maintained commercial quality steel grades as a major material in many industrial applications due to its low processing cost. Few innovative products have however been developed specifically for production by thin slab direct rolling. Press hardening or hot press forming steel grades which are now widely used to produce structural automotive steel parts requiring ultra-high strength and formability may however offer an opportunity for thin slab direct rolling-specific ultra-high strength products. In this work, a newly designed press hardening steel grade developed specifically for thin slab direct rolling processing is presented. The press hardening steel has a high nitrogen content compared with press hardening steel grades produced by conventional steelmaking routes. Boron and titanium which are key alloying additions in conventional press hardening steel such as the 22MnB5 press hardening steel grade are not utilized. Cr is added in the press hardening steel to obtain the required hardenability. The properties of the new thin slab direct rolling-specific 22MnCrN5 press hardening steel grade are reviewed. The evolution of the microstructure and mechanical properties with increasing amounts of Cr additions from 0.6 to 1.4 wt pct and the effect of the cooling rate during die-quenching were studied by means of laboratory simulations. The selection of the optimum chemical composition range for the thin slab direct rolling-specific 22MnCrN5 steel in press hardening heat treatment conditions is discussed.

  1. Potential role of strain hardening in the cessation of rifting at constant tectonic force

    NASA Astrophysics Data System (ADS)

    Yamasaki, Tadashi; Stephenson, Randell

    2009-01-01

    In this study the cessation of rifting at constant tectonic force is discussed from the viewpoint of lithospheric rheology using a simple one-dimensional numerical model. The behaviour of the conventionally adopted constant force model re-examined in this study contradicts some general features in the development of sedimentary basins. Strain hardening is implemented to explain the contradictions, in which the viscosity of the mantle is a function of not only the strain rate and temperature but also the total strain. The roles of various strain hardening parameters in rifting dynamics are examined, including the strain required for the onset of hardening, the strain interval required for the completion of hardening and the factor controlling the increase in mantle viscosity. It is shown that a model with strain hardening can explain many characteristic features of sedimentary basin formation better than the conventional constant force model. There are a variety of ways in which rifting can be terminated by the strain hardening model, depending on the initial lithospheric structure, magnitude of tectonic force and the hardening process. One possible strain hardening mechanism involves the switch from wet to dry rheology associated with decompressional melting, though the implemented strain hardening formula could be generally applicable to any hardening phenomenon and could therefore be physically interpreted as such. The results of this study also provide important insights into sedimentary basin subsidence in relation to rifting dynamics. The end of an initial rapid ("syn-rift" like) subsidence phase is not necessarily equivalent to the end of actual rifting as in the constant force model. The transition from initial rapid subsidence to long-term, more subdued ("post-rift" like), subsidence is actually marked by the onset of deceleration of rifting. Since significant extension still continues for some time thereafter, the subsequent long-term subsidence includes

  2. Tradeoffs in Flight Design Upset Mitigation in State of the Art FPGAs: Hardened by Design vs. Design Level Hardening

    NASA Technical Reports Server (NTRS)

    Swift, Gary M.; Roosta, Ramin

    2004-01-01

    This presentation compares and contrasts the effectiveness and the system/designer impacts of the two main approaches to upset hardening: the Actel approach (RTSX-S and RTAX-S) of low-level (inside each flip-flop) triplication and the Xilinx approach (Virtex and Virtex2) of design-level triplication of both functional blocks and voters. The effectiveness of these approaches is compared using measurements made in conjunction with each of the FPGAs' manufacturer: for Actel, published data [1] and for Xilinx, recent results from the Xilinx SEE Test Consortium (note that the author is an active and founding member). The impacts involve Actel advantages in the areas of transistor-utilization efficiency and minimizing designer involvement in the triplication while the Xilinx advantages relate to the ability to custom tailor upset hardness and the flexibility of re-configurability. Additionally, there are currently clear Xilinx advantages in available features such as the number of I/O's, logic cells, and RAM blocks as well as speed. However, the advantage of the Actel anti-fuses for configuration over the Xilinx SRAM cells is that the latter need additional functionality and external circuitry (PROMs and, at least a watchdog timer) for configuration and configuration scrubbing. Further, although effectively mitigated if done correctly, the proton upset-ability of the Xilinx FPGAs is a concern in severe proton-rich environments. Ultimately, both manufacturers' upset hardening is limited by SEFI (single-event functional interrupt) rates where it appears the Actel results are better although the Xilinx Virtex2-family result of about one SEFI in 65 device-years in solar-min GCR (the more intense part of the galactic cosmic-ray background) should be acceptable to most missions

  3. Development of intermetallic-hardened abrasion-resistant weld hardfacing alloys

    SciTech Connect

    School, M.R.

    1986-01-01

    Chromium and cobalt are strategic materials in the US and both are major constituents in many weld hardfacing alloys. Substitution for these materials or alternatives to their use was a primary direction of this investigation which was conducted in conjunction with the US Bureau of Mines. Minimization of the use of strategic materials was the criteria guiding the development of intermetallic-hardened abrasion resistant weld hardfacing materials. Other criteria were that the new alloy contain a hard intermetallic compound in an FCC matrix, and that these intermetallic compounds be stable at room temperature. A survey of ternary systems was made and the Fe-Mo-Ni system was selected to provide a basis for alloy development. Fe-Mo-Ni alloys synthesized by arc-melting and similar alloys made by welding possessed similar microstructures, a (Fe, Ni){sub 7}Mo{sub 6} intermetallic plus austenite eutectic in an austenitic matrix. These materials exhibited poor abrasive resistance. Silicon additions to the alloy promoted formation of a Laves phase FeMoSi intermetallic which helped increase the abrasive wear resistance. Through a series of alloy chemistry iterations a final composition of Fe-20Mo-15Ni-5Si was selected. Heat treatment of this alloy at 550 to 650 C caused second phase precipitation in the matrix and raised the hardness about 14 points HRC to 50 HRC. The alloy's wear rate, measured with the pin-on-drum abrasive wear test, was 6.3 to 6.5 mg/m. However this was twice the wear rate observed in commercial high-carbon high-chromium alloys. Based on examination of the alloy microstructures, their chemistry, and an analysis of the Fe-Mo-Si phase system; directions for further research are to increase the molybdenum and silicon content to produce a Fe-20Mo-10Ni-15Si composition.

  4. The influence of fly ash on obtaining quality plastic and hardened properties of portland cement concrete

    SciTech Connect

    Mohamad, A.B.

    1989-01-01

    An experimental test burn was done substituting coal with Refuse-Derived-Fuel(RDF) consisting mainly of waste paper and plastic with heating value of 6000 to 8000 BTU/lb. Twelve test burn days were run with 4 days of 5% RDF and 8 days of 10% RDF. The effect of RDF on the chemical and physical properties of fly ash and the effect of coal-RDF fly ash on the properties of plastic and hardened concrete were investigated. Coal fly ash from Merrimack Power Station was classified as an ASTM class F complying to the chemical and physical properties of ASTM C-618 specifications. Coal-RDF fly ash produced during the test burn showed chemical and physical properties comparable to coal fly ash. The average chemical and physical properties of coal-RDF fly ash complied to ASTM C-618 specifications. Concrete made with coal fly ash and coal-RDF fly ash showed increased slump in high paste mixes and decreased slump in low paste mixes. Air content decreased with increased fly ash at a constant dosage of air entrainment. Compressive strength the fly ash concrete at and beyond 28 days were comparable to ordinary portland cement concrete. Heavy metals were not leached from coal fly ash and coal-RDF fly ash concrete during a column test using a synthetic acid rain of pH 4.5 even though small quantities of cadmium and lead were found to leach from coal fly ash and coal-RDF fly ash during the beginning of the test. The volume of the acid rain was approximately equivalent to 7 years of precipitation, assuming 36 inches of rain per year. A microscopic investigation comparing the structure of pastes made with coal fly ash, coal-RDF fly ash, incinerator fly ash and incinerator bottom ash was conducted.

  5. Extreme Precipitation Strengthening in Ion-Implanted Nickel

    SciTech Connect

    Follstaedt, D.M.; Knapp, J.A.; Myers, S.M.; Petersen, G.A.

    1999-05-03

    Precipitation strengthening of nickel was investigated using ion-implantation alloying and nanoindentation testing for particle separations in the nanometer range and volume fractions extending above 10O/O. Ion implantation of either oxygen alone or oxygen plus aluminum at room temperature was shown to produce substantial strengthening in the ion-treated layer, with yield strengths near 5 GPa in both cases. After annealing to 550"C the oxygen-alone layer loses much of the benefit, with its yield strength reduced to 1.2 GP~ but the dual ion-implanted layer retains a substantially enhanced yield strength of over 4 GPa. Examination by transmission electron f microscopy showed very fine dispersions of 1-5 nm diameter NiO and y-A1203 precipitates in the implanted layers before annealing. The heat treatment at 550"C induced ripening of the NiO particles to sizes ranging from 7 to 20 nm, whereas the more stable ~-A1203 precipitates were little changed. The extreme strengthening we observe is in semiquantitative agreement with predictions based on the application of dispersion-hardening theory to these microstructure.

  6. Analysis of Obstacle Hardening Models Using Dislocation Dynamics: Application to Irradiation-Induced Defects

    NASA Astrophysics Data System (ADS)

    Sobie, Cameron; Bertin, Nicolas; Capolungo, Laurent

    2015-08-01

    Irradiation hardening in -iron represents a critical factor in nuclear reactor design and lifetime prediction. The dispersed barrier hardening, Friedel Kroupa Hirsch (FKH), and Bacon Kocks Scattergood (BKS) models have been proposed to predict hardening caused by dislocation obstacles in metals, but the limits of their applicability have never been investigated for varying defect types, sizes, and densities. In this work, dislocation dynamics calculations of irradiation-induced obstacle hardening in the athermal case were compared to these models for voids, self-interstitial atom (SIA) loops, and a combination of the two types. The BKS model was found to accurately predict hardening due to voids, whereas the FKH model was superior for SIA loops. For both loops and voids, the hardening from a normal distribution of defects was compared to that from the mean size, and was shown to have no statistically significant dependence on the distribution. A mean size approach was also shown to be valid for an asymmetric distribution of voids. A non-linear superposition principle was shown to predict the hardening from the simultaneous presence of voids and SIA loops.

  7. Precipitation Behavior During Aging in α Phase Titanium Supersaturated with Cu

    NASA Astrophysics Data System (ADS)

    Mitsuhara, Masatoshi; Masuda, Tomoya; Nishida, Minoru; Kunieda, Tomonori; Fujii, Hideki

    2016-04-01

    Age hardening of Ti-2.3 mass pct Cu (Ti-2.3Cu) at 673 K to 873 K (400 °C to 600 °C) after solution treatment at 1063 K (790 °C) was observed. The relationship between precipitates formed during aging and changes in hardness was investigated. During aging at 673 K (400 °C), the hardness increased rapidly up to 200 hours, and subsequently increased more slowly up to 1000 hours. At 873 K (600 °C), the hardness began to decrease immediately. Transmission electron microscopy showed that fine disk-shaped precipitates of 20 to 40 nm in diameter grew in the α phase. It is concluded that these precipitates interacted with dislocations and increased the hardness. At 873 K (600 °C), precipitates of 1 µm in length and Ti2Cu particles of 200 nm in length were observed. The decrease in hardness may have resulted from the precipitate formation decreasing the concentration of Cu in the α phase. Bright/dark contrast of the three atomic layers and small atomic shift of the hcp structure were observed in the atomic resolution imaging of the precipitates. This suggests that the precipitates are not just Cu-enriched zones and have structures with similar periodicity to the Ti2Cu phase, which is thermally stable at those aging temperatures.

  8. Precipitation Indices Low Countries

    NASA Astrophysics Data System (ADS)

    van Engelen, A. F. V.; Ynsen, F.; Buisman, J.; van der Schrier, G.

    2009-09-01

    Since 1995, KNMI published a series of books(1), presenting an annual reconstruction of weather and climate in the Low Countries, covering the period AD 763-present, or roughly, the last millennium. The reconstructions are based on the interpretation of documentary sources predominantly and comparison with other proxies and instrumental observations. The series also comprises a number of classifications. Amongst them annual classifications for winter and summer temperature and for winter and summer dryness-wetness. The classification of temperature have been reworked into peer reviewed (2) series (AD 1000-present) of seasonal temperatures and temperature indices, the so called LCT (Low Countries Temperature) series, now incorporated in the Millennium databases. Recently we started a study to convert the dryness-wetness classifications into a series of precipitation; the so called LCP (Low Countries Precipitation) series. A brief outline is given here of the applied methodology and preliminary results. The WMO definition for meteorological drought has been followed being that a period is called wet respectively dry when the amount of precipitation is considerable more respectively less than usual (normal). To gain a more quantitative insight for four locations, geographically spread over the Low Countries area (De Bilt, Vlissingen, Maastricht and Uccle), we analysed the statistics of daily precipitation series, covering the period 1900-present. This brought us to the following definition, valid for the Low Countries: A period is considered as (very) dry respectively (very) wet if over a continuous period of at least 60 days (~two months) cq 90 days (~three months) on at least two out of the four locations 50% less resp. 50% more than the normal amount for the location (based on the 1961-1990 normal period) has been measured. This results into the following classification into five drought classes hat could be applied to non instrumental observations: Very wet period

  9. Non Radiation Hardened Microprocessors in Spaced Based Remote Sensing Systems

    NASA Technical Reports Server (NTRS)

    Decoursey, Robert J.; Estes, Robert F.; Melton, Ryan

    2006-01-01

    The CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) mission is a comprehensive suite of active and passive sensors including a 20Hz 230mj Nd:YAG lidar, a visible wavelength Earth-looking camera and an imaging infrared radiometer. CALIPSO flies in formation with the Earth Observing System Post-Meridian (EOS PM) train, provides continuous, near-simultaneous measurements and is a planned 3 year mission. CALIPSO was launched into a 98 degree sun synchronous Earth orbit in April of 2006 to study clouds and aerosols and acquires over 5 gigabytes of data every 24 hours. The ground track of one CALIPSO orbit as well as high and low intensity South Atlantic Anomaly outlines is shown. CALIPSO passes through the SAA several times each day. Spaced based remote sensing systems that include multiple instruments and/or instruments such as lidar generate large volumes of data and require robust real-time hardware and software mechanisms and high throughput processors. Due to onboard storage restrictions and telemetry downlink limitations these systems must pre-process and reduce the data before sending it to the ground. This onboard processing and realtime requirement load may mean that newer more powerful processors are needed even though acceptable radiation-hardened versions have not yet been released. CALIPSO's single board computer payload controller processor is actually a set of four (4) voting non-radiation hardened COTS Power PC 603r's built on a single width VME card by General Dynamics Advanced Information Systems (GDAIS). Significant radiation concerns for CALIPSO and other Low Earth Orbit (LEO) satellites include the South Atlantic Anomaly (SAA), the north and south poles and strong solar events. Over much of South America and extending into the South Atlantic Ocean the Van Allen radiation belts dip to just 200-800km and spacecraft entering this area are subjected to high energy protons and experience higher than normal Single Event Upset

  10. NINJA: a noninvasive framework for internal computer security hardening

    NASA Astrophysics Data System (ADS)

    Allen, Thomas G.; Thomson, Steve

    2004-07-01

    Vulnerabilities are a growing problem in both the commercial and government sector. The latest vulnerability information compiled by CERT/CC, for the year ending Dec. 31, 2002 reported 4129 vulnerabilities representing a 100% increase over the 2001 [1] (the 2003 report has not been published at the time of this writing). It doesn"t take long to realize that the growth rate of vulnerabilities greatly exceeds the rate at which the vulnerabilities can be fixed. It also doesn"t take long to realize that our nation"s networks are growing less secure at an accelerating rate. As organizations become aware of vulnerabilities they may initiate efforts to resolve them, but quickly realize that the size of the remediation project is greater than their current resources can handle. In addition, many IT tools that suggest solutions to the problems in reality only address "some" of the vulnerabilities leaving the organization unsecured and back to square one in searching for solutions. This paper proposes an auditing framework called NINJA (acronym for Network Investigation Notification Joint Architecture) for noninvasive daily scanning/auditing based on common security vulnerabilities that repeatedly occur in a network environment. This framework is used for performing regular audits in order to harden an organizations security infrastructure. The framework is based on the results obtained by the Network Security Assessment Team (NSAT) which emulates adversarial computer network operations for US Air Force organizations. Auditing is the most time consuming factor involved in securing an organization's network infrastructure. The framework discussed in this paper uses existing scripting technologies to maintain a security hardened system at a defined level of performance as specified by the computer security audit team. Mobile agents which were under development at the time of this writing are used at a minimum to improve the noninvasiveness of our scans. In general, noninvasive

  11. Hardening/finishing treatment of compressor blades using a machine with planetary container motion

    NASA Astrophysics Data System (ADS)

    Shpatakovskii, A. F.

    A process for the hardening and finishing of high-pressure compressor blades for aircraft powerplants is described whereby the blades are placed in containers that move along a planetary path in a hardening medium consisting of steel balls. The extent of surface hardening, surface roughness, and residual stresses are determined for specimens of U8A steel and blades of EP718VD alloy treated under different conditions. The efficiency of the treatment in terms of increased blade durability and productivity is estimated.

  12. Developments in Radiation-Hardened Electronics Applicable to the Vision for Space Exploration

    NASA Technical Reports Server (NTRS)

    Keys, Andrew S.; Frazier, Donald O.; Patrick , Marshall C.; Watson, Michael D.; Johnson, Michael A.; Cressler, John D.; Kolawa, Elizabeth A.

    2007-01-01

    The Radiation Hardened Electronics for Space Exploration (RHESE) project develops the advanced technologies required to produce radiation hardened electronics, processors, and devices in support of the anticipated requirements of NASA's Constellation program. Methods of protecting and hardening electronics against the encountered space environment are discussed. Critical stages of a spaceflight mission that are vulnerable to radiation-induced interruptions or failures are identified. Solutions to mitigating the risk of radiation events are proposed through the infusion of RHESE technology products and deliverables into the Constellation program's spacecraft designs.

  13. Combined electron beam imaging and ab initio modeling of T{sub 1} precipitates in Al-Li-Cu alloys

    SciTech Connect

    Dwyer, C.; Weyland, M.; Chang, L. Y.; Muddle, B. C.

    2011-05-16

    Among the many considerable challenges faced in developing a rational basis for advanced alloy design, establishing accurate atomistic models is one of the most fundamental. Here we demonstrate how advanced imaging techniques in a double-aberration-corrected transmission electron microscope, combined with ab initio modeling, have been used to determine the atomic structure of embedded 1 nm thick T{sub 1} precipitates in precipitation-hardened Al-Li-Cu aerospace alloys. The results provide an accurate determination of the controversial T{sub 1} structure, and demonstrate how next-generation techniques permit the characterization of embedded nanostructures in alloys and other nanostructured materials.

  14. DISSOLUTION OF LANTHANUM FLUORIDE PRECIPITATES

    DOEpatents

    Fries, B.A.

    1959-11-10

    A plutonium separatory ore concentration procedure involving the use of a fluoride type of carrier is presented. An improvement is given in the derivation step in the process for plutonium recovery by carrier precipitation of plutonium values from solution with a lanthanum fluoride carrier precipitate and subsequent derivation from the resulting plutonium bearing carrier precipitate of an aqueous acidic plutonium-containing solution. The carrier precipitate is contacted with a concentrated aqueous solution of potassium carbonate to effect dissolution therein of at least a part of the precipitate, including the plutonium values. Any remaining precipitate is separated from the resulting solution and dissolves in an aqueous solution containing at least 20% by weight of potassium carbonate. The reacting solutions are combined, and an alkali metal hydroxide added to a concentration of at least 2N to precipitate lanthanum hydroxide concomitantly carrying plutonium values.

  15. Effects of Powder Attributes and Laser Powder Bed Fusion (L-PBF) Process Conditions on the Densification and Mechanical Properties of 17-4 PH Stainless Steel

    NASA Astrophysics Data System (ADS)

    Irrinki, Harish; Dexter, Michael; Barmore, Brenton; Enneti, Ravi; Pasebani, Somayeh; Badwe, Sunil; Stitzel, Jason; Malhotra, Rajiv; Atre, Sundar V.

    2016-03-01

    The effects of powders attributes (shape and size distribution) and critical processing conditions (energy density) on the densification and mechanical properties of laser powder bed fusion (L-PBF) 17-4 PH stainless steel were studied using four types of powders. The % theoretical density, ultimate tensile strength and hardness of both water- and gas-atomized powders increased with increased energy density. Gas-atomized powders showed superior densification and mechanical properties when processed at low energy densities. However, the % theoretical density and mechanical properties of water-atomized powders were comparable to gas-atomized powders when sintered at a high energy density of 104 J/mm3. An important result of this study was that, even at high % theoretical density (97% ± 1%), the properties of as-printed parts could vary over a relatively large range (UTS: 500-1100 MPa; hardness: 25-39 HRC; elongation: 10-25%) depending on powder characteristics and process conditions. The results also demonstrate the feasibility of using relatively inexpensive water-atomized powders as starting raw material instead of the typically used gas-atomized powders to fabricate parts using L-PBF techniques by sintering at high energy densities.

  16. Dynamic response of two strain-hardened aluminum alloys

    NASA Astrophysics Data System (ADS)

    Boteler, J. M.; Dandekar, D. P.

    2006-09-01

    Despite their common usage in armor applications such as lightweight armored vehicles, the dynamic material response of 5083-H131 and 5083-H32 strain-hardened aluminum alloys has not been previously reported in the open literature. Measurement of the dynamic material properties, including the shock Hugoniot equation of state (EOS), provides hydrocode modelers with critical information required for accurate modeling of material response to intense loading. In the work reported here we investigate the Hugoniot EOS and Hugoniot elastic limit over the stress range of 1.5-8.0GPa. All experiments were performed on the Army Research Laboratory 102mm bore single-stage light gas gun. Impact conditions were uniaxial and planar to within 1mrad of tilt. Both direct-impact- and shock-transmission-type experiments were performed using velocity interferometry diagnostics to record particle velocity histories with 0.5ns temporal resolution. The shock Hugoniot for 5083-H131 is extrapolated to 50GPa and compared to the previous high pressure results of Hauver and Melani (1973) [Ballistic Research Laboratory December Technical Report No. BRL 2345, 1973] and to prior shock studies of 5083-O aluminum alloy.

  17. Waste tyre rubberized concrete: properties at fresh and hardened state.

    PubMed

    Aiello, M A; Leuzzi, F

    2010-01-01

    The main objective of this paper is to investigate the properties of various concrete mixtures at fresh and hardened state, obtained by a partial substitution of coarse and fine aggregate with different volume percentages of waste tyres rubber particles, having the same dimensions of the replaced aggregate. Workability, unit weight, compressive and flexural strength and post-cracking behaviour were evaluated and a comparison of the results for the different rubcrete mixtures were proposed in order to define the better mix proportions in terms of mechanical properties of the rubberized concrete. Results showed in this paper were also compared to data reported in literature. Moreover, a preliminary geometrical, physical and mechanical characterization on scrap tyre rubber shreds was made. The rubberized concrete mixtures showed lower unit weight compared to plain concrete and good workability. The results of compressive and flexural tests indicated a larger reduction of mechanical properties of rubcrete when replacing coarse aggregate rather than fine aggregate. On the other hand, the post-cracking behaviour of rubberized concrete was positively affected by the substitution of coarse aggregate with rubber shreds, showing a good energy absorption and ductility indexes in the range observed for fibrous concrete, as suggested by standard (ASTM C1018-97, 1997). PMID:20207128

  18. Switchable hardening of a ferromagnet at fixed temperature.

    PubMed

    Silevitch, D M; Aeppli, G; Rosenbaum, T F

    2010-02-16

    The intended use of a magnetic material, from information storage to power conversion, depends crucially on its domain structure, traditionally crafted during materials synthesis. By contrast, we show that an external magnetic field, applied transverse to the preferred magnetization of a model disordered uniaxial ferromagnet, is an isothermal regulator of domain pinning. At elevated temperatures, near the transition into the paramagnet, modest transverse fields increase the pinning, stabilize the domain structure, and harden the magnet, until a point where the field induces quantum tunneling of the domain walls and softens the magnet. At low temperatures, tunneling completely dominates the domain dynamics and provides an interpretation of the quantum phase transition in highly disordered magnets as a localization/delocalization transition for domain walls. While the energy scales of the rare earth ferromagnet studied here restrict the effects to cryogenic temperatures, the principles discovered are general and should be applicable to existing classes of highly anisotropic ferromagnets with ordering at room temperature or above. PMID:20133728

  19. Yield Hardening of Electrorheological Fluids in Channel Flow

    NASA Astrophysics Data System (ADS)

    Helal, Ahmed; Qian, Bian; McKinley, Gareth H.; Hosoi, A. E.

    2016-06-01

    Electrorheological fluids offer potential for developing rapidly actuated hydraulic devices where shear forces or pressure-driven flow are present. In this study, the Bingham yield stress of electrorheological fluids with different particle volume fractions is investigated experimentally in wall-driven and pressure-driven flow modes using measurements in a parallel-plate rheometer and a microfluidic channel, respectively. A modified Krieger-Dougherty model can be used to describe the effects of the particle volume fraction on the yield stress and is in good agreement with the viscometric data. However, significant yield hardening in pressure-driven channel flow is observed and attributed to an increase and eventual saturation of the particle volume fraction in the channel. A phenomenological physical model linking the densification and consequent microstructure to the ratio of the particle aggregation time scale compared to the convective time scale is presented and used to predict the enhancement in yield stress in channel flow, enabling us to reconcile discrepancies in the literature between wall-driven and pressure-driven flows.

  20. Superconducting (radiation hardened) magnets for mirror fusion devices

    SciTech Connect

    Henning, C.D.; Dalder, E.N.C.; Miller, J.R.; Perkins, J.R.

    1983-12-07

    Superconducting magnets for mirror fusion have evolved considerably since the Baseball II magnet in 1970. Recently, the Mirror Fusion Test Facility (MFTF-B) yin-yang has been tested to a full field of 7.7 T with radial dimensions representative of a full scale reactor. Now the emphasis has turned to the manufacture of very high field solenoids (choke coils) that are placed between the tandem mirror central cell and the yin-yang anchor-plug set. For MFTF-B the choke coil field reaches 12 T, while in future devices like the MFTF-Upgrade, Fusion Power Demonstration and Mirror Advanced Reactor Study (MARS) reactor the fields are doubled. Besides developing high fields, the magnets must be radiation hardened. Otherwise, thick neutron shields increase the magnet size to an unacceptable weight and cost. Neutron fluences in superconducting magnets must be increased by an order of magnitude or more. Insulators must withstand 10/sup 10/ to 10/sup 11/ rads, while magnet stability must be retained after the copper has been exposed to fluence above 10/sup 19/ neutrons/cm/sup 2/.

  1. Switchable hardening of a ferromagnet at fixed temperature

    PubMed Central

    Silevitch, D. M.; Aeppli, G.; Rosenbaum, T. F.

    2010-01-01

    The intended use of a magnetic material, from information storage to power conversion, depends crucially on its domain structure, traditionally crafted during materials synthesis. By contrast, we show that an external magnetic field, applied transverse to the preferred magnetization of a model disordered uniaxial ferromagnet, is an isothermal regulator of domain pinning. At elevated temperatures, near the transition into the paramagnet, modest transverse fields increase the pinning, stabilize the domain structure, and harden the magnet, until a point where the field induces quantum tunneling of the domain walls and softens the magnet. At low temperatures, tunneling completely dominates the domain dynamics and provides an interpretation of the quantum phase transition in highly disordered magnets as a localization/delocalization transition for domain walls. While the energy scales of the rare earth ferromagnet studied here restrict the effects to cryogenic temperatures, the principles discovered are general and should be applicable to existing classes of highly anisotropic ferromagnets with ordering at room temperature or above. PMID:20133728

  2. Magnetic hardening of Fe30Co70 nanowires

    NASA Astrophysics Data System (ADS)

    Liébana Viñas, Sara; Salikhov, Ruslan; Bran, Cristina; Palmero, Ester M.; Vazquez, Manuel; Arvan, Behnaz; Yao, Xiang; Toson, Peter; Fidler, Josef; Spasova, Marina; Wiedwald, Ulf; Farle, Michael

    2015-10-01

    3d transition metal-based magnetic nanowires (NWs) are currently considered as potential candidates for alternative rare-earth-free alloys as novel permanent magnets. Here, we report on the magnetic hardening of Fe30Co70 nanowires in anodic aluminium oxide templates with diameters of 20 nm and 40 nm (length 6 μm and 7.5 μm, respectively) by means of magnetic pinning at the tips of the NWs. We observe that a 3-4 nm naturally formed ferrimagnetic FeCo oxide layer covering the tip of the FeCo NW increases the coercive field by 20%, indicating that domain wall nucleation starts at the tip of the magnetic NW. Ferromagnetic resonance (FMR) measurements were used to quantify the magnetic uniaxial anisotropy energy of the samples. Micromagnetic simulations support our experimental findings, showing that the increase of the coercive field can be achieved by controlling domain wall nucleation using magnetic materials with antiferromagnetic exchange coupling, i.e. antiferromagnets or ferrimagnets, as a capping layer at the nanowire tips.

  3. A Radiation Hardened by Design CMOS ASIC for Thermopile Readouts

    NASA Technical Reports Server (NTRS)

    Quilligan, G.; Aslam, S.; DuMonthier, J.

    2012-01-01

    A radiation hardened by design (RHBD) mixed-signal application specific integrated circuit (ASIC) has been designed for a thermopile readout for operation in the harsh Jovian orbital environment. The multi-channel digitizer (MCD) ASIC includes 18 low noise amplifier channels which have tunable gain/filtering coefficients, a 16-bit sigma-delta analog-digital converter (SDADC) and an on-chip controller. The 18 channels, SDADC and controller were designed to operate with immunity to single event latchup (SEL) and to at least 10 Mrad total ionizing dose (TID). The ASIC also contains a radiation tolerant 16-bit 20 MHz Nyquist ADC for general purpose instrumentation digitizer needs. The ASIC is currently undergoing fabrication in a commercial 180 nm CMOS process. Although this ASIC was designed specifically for the harsh radiation environment of the NASA led JEO mission it is suitable for integration into instrumentation payloads 011 the ESA JUICE mission where the radiation hardness requirements are slightly less stringent.

  4. 'Age-hardened alloy' based on bulk polycrystalline oxide ceramic

    NASA Astrophysics Data System (ADS)

    Gurnani, Luv; Singh, Mahesh Kumar; Bhargava, Parag; Mukhopadhyay, Amartya

    2015-05-01

    We report here for the first time the development of 'age-hardened/toughened' ceramic alloy based on MgO in the bulk polycrystalline form. This route allows for the facile development of a 'near-ideal' microstructure characterized by the presence of nanosized and uniformly dispersed second-phase particles (MgFe2O4) within the matrix grains, as well as along the matrix grain boundaries, in a controlled manner. Furthermore, the intragranular second-phase particles are rendered coherent with the matrix (MgO). Development of such microstructural features for two-phase bulk polycrystalline ceramics is extremely challenging following the powder metallurgical route usually adopted for the development of bulk ceramic nanocomposites. Furthermore, unlike for the case of ceramic nanocomposites, the route adopted here does not necessitate the usage of nano-powder, pressure/electric field-assisted sintering techniques and inert/reducing atmosphere. The as-developed bulk polycrystalline MgO-MgFe2O4 alloys possess considerably improved hardness (by ~52%) and indentation toughness (by ~35%), as compared to phase pure MgO.

  5. Radiation Hardened, Modulator ASIC for High Data Rate Communications

    NASA Technical Reports Server (NTRS)

    McCallister, Ron; Putnam, Robert; Andro, Monty; Fujikawa, Gene

    2000-01-01

    Satellite-based telecommunication services are challenged by the need to generate down-link power levels adequate to support high quality (BER approx. equals 10(exp 12)) links required for modem broadband data services. Bandwidth-efficient Nyquist signaling, using low values of excess bandwidth (alpha), can exhibit large peak-to-average-power ratio (PAPR) values. High PAPR values necessitate high-power amplifier (HPA) backoff greater than the PAPR, resulting in unacceptably low HPA efficiency. Given the high cost of on-board prime power, this inefficiency represents both an economical burden, and a constraint on the rates and quality of data services supportable from satellite platforms. Constant-envelope signals offer improved power-efficiency, but only by imposing a severe bandwidth-efficiency penalty. This paper describes a radiation- hardened modulator which can improve satellite-based broadband data services by combining the bandwidth-efficiency of low-alpha Nyquist signals with high power-efficiency (negligible HPA backoff).

  6. Designing Security-Hardened Microkernels For Field Devices

    NASA Astrophysics Data System (ADS)

    Hieb, Jeffrey; Graham, James

    Distributed control systems (DCSs) play an essential role in the operation of critical infrastructures. Perimeter field devices are important DCS components that measure physical process parameters and perform control actions. Modern field devices are vulnerable to cyber attacks due to their increased adoption of commodity technologies and that fact that control networks are no longer isolated. This paper describes an approach for creating security-hardened field devices using operating system microkernels that isolate vital field device operations from untrusted network-accessible applications. The approach, which is influenced by the MILS and Nizza architectures, is implemented in a prototype field device. Whereas, previous microkernel-based implementations have been plagued by poor inter-process communication (IPC) performance, the prototype exhibits an average IPC overhead for protected device calls of 64.59 μs. The overall performance of field devices is influenced by several factors; nevertheless, the observed IPC overhead is low enough to encourage the continued development of the prototype.

  7. Improving the analysis of small precipitates in HSLA steels using a plasma cleaner and ELNES.

    PubMed

    Wilson, J A; Craven, A J

    2003-04-01

    The change from producing high strength low alloy (HSLA) steel sheet by conventional thick slab casting to producing it by direct charged thin slab casting causes a major change in the evolution of the precipitation. A key area of interest is the composition of the sub-10nm precipitates used to produce dispersion hardening. Carbon extraction replicas are frequently used to study precipitates in steels and other metals. When used with annular dark field imaging, this technique gives high contrast images of the precipitates while the thin carbon film adds little background or additional characteristic signals to either electron energy loss spectra or energy dispersive X-ray spectra. The method has the additional major advantage of removing the ferromagnetic matrix when studying HSLA steels. However, when the precipitates contain carbon, the C K-edge is dominated by the contribution from the amorphous carbon film. A plasma cleaner can be used to thin this carbon film to approximately 0.5 nm or less and then the contribution from the carbon in the precipitate can be separated from that in the carbon film using the electron energy loss near edge structure. A similar approach can be taken to separate the oxygen content of the precipitate from that of oxides formed from low-level impurities in the amorphous carbon during the plasma thinning process. In most cases, the precipitate studied here contained little or no oxygen even for the smallest sizes examined (approximately 4 nm). The precipitates contain mainly nitrogen with little carbon. For some compositions, the precipitates are clearly sub-stoichiometric. PMID:12524190

  8. The Global Precipitation Climatology Project (GPCP) Combined Precipitation Dataset

    NASA Technical Reports Server (NTRS)

    Huffman, George J.; Adler, Robert F.; Arkin, Philip; Chang, Alfred; Ferraro, Ralph; Gruber, Arnold; Janowiak, John; McNab, Alan; Rudolf, Bruno; Schneider, Udo

    1997-01-01

    The Global Precipitation Climatology Project (GPCP) has released the GPCP Version 1 Combined Precipitation Data Set, a global, monthly precipitation dataset covering the period July 1987 through December 1995. The primary product in the dataset is a merged analysis incorporating precipitation estimates from low-orbit-satellite microwave data, geosynchronous-orbit -satellite infrared data, and rain gauge observations. The dataset also contains the individual input fields, a combination of the microwave and infrared satellite estimates, and error estimates for each field. The data are provided on 2.5 deg x 2.5 deg latitude-longitude global grids. Preliminary analyses show general agreement with prior studies of global precipitation and extends prior studies of El Nino-Southern Oscillation precipitation patterns. At the regional scale there are systematic differences with standard climatologies.

  9. Model Identification and FE Simulations: Effect of Different Yield Loci and Hardening Laws in Sheet Forming

    NASA Astrophysics Data System (ADS)

    Flores, P.; Duchêne, L.; Lelotte, T.; Bouffioux, C.; El Houdaigui, F.; Van Bael, A.; He, S.; Duflou, J.; Habraken, A. M.

    2005-08-01

    The bi-axial experimental equipment developed by Flores enables to perform Baushinger shear tests and successive or simultaneous simple shear tests and plane-strain tests. Such experiments and classical tensile tests investigate the material behavior in order to identify the yield locus and the hardening models. With tests performed on two steel grades, the methods applied to identify classical yield surfaces such as Hill or Hosford ones as well as isotropic Swift type hardening or kinematic Armstrong-Frederick hardening models are explained. Comparison with the Taylor-Bishop-Hill yield locus is also provided. The effect of both yield locus and hardening model choice will be presented for two applications: Single Point Incremental Forming (SPIF) and a cup deep drawing.

  10. Interrelation of Steel Composition, Hardening Route, and Tempering Response of Medium Carbon Low-Alloy Steels

    NASA Astrophysics Data System (ADS)

    Hussein, Abdel-Hamid A.; Abdu, Mahmoud T.; El-Banna, El-Sayed M.; Soliman, Saied E.; Tash, Mahmoud M.

    2016-04-01

    Four medium carbon and low-alloy steels were hardened through oil and forced air cooling. Tempering was then performed in the temperature range 250-600 °C. The martensite content increased with an increased hardenability and/or the rate of cooling. Tempering at T > M s caused a gradual decline in both hardness and strength and an improvement in the Charpy V-notch impact toughness. The low-alloy steels underwent tempered martensite embrittlement (as a result of the formation of carbides at the martensite interlaths and prior austenite grain boundaries) and enhancement of phosphorus segregation (particularly in the presence of Ni). Higher hardenability steels were found to be better hardened via the more recent forced air quenching rather than the conventional oil quenching. In this work, a modest, novel attempt is presented to empirically correlate the impact toughness with the hardness measurements to enable future prediction of impact toughness from hardness measurements.

  11. Analysis of structure and phase composition of rails subjected to differential hardening at different regimes

    SciTech Connect

    Gromov, V. E. Morozov, K. V. Konovalov, S. V.; Alsaraeva, K. V.; Semina, O. A.; Ivanov, Yu. F.; Volkov, K. V.

    2014-11-14

    Differential hardening of rails by compressed air in different regimes is accompanied by formation of morphologically different structure, being formed according to the diffusion mechanism of γ↔α transformation and consisting of grains of lamellar pearlite, free ferrite and grains of ferrite-carbide mixture. By methods of transmission electron microscopy the layer by layer analysis of differentially hardened rails has been carried out, the quantitative parameters of the structure, phase composition and dislocation substructure have been established and their comparison has been made for different regimes of hardening. It has been found that the structure-phase states being formed have gradient character, defined by the hardening regime, direction of study from the surface of rolling and by depth of location of layer under study.

  12. Ramberg-Osgood strain-hardening characterization on an ASTM A302-B steel

    SciTech Connect

    James, L.A.

    1995-11-01

    Many elastic-plastic fracture mechanisms analysis procedures require knowledge of the true stress versus true strain response of the material being analyzed. The most common strain-hardening relationship employed is of the form first proposed by Ramberg and Osgood. Here, the Ramberg-Osgood strain-hardening exponents and coefficients are characterized for an unirradiated ASTM A302-B steel over a wide range of temperatures from {minus}129 to 260 C. The strain-hardening exponent increases only slightly with temperature over this range, while the coefficient decreases with increasing temperature. Tensile specimens irradiated to 0.002, 0.029, and 0.046 dpa exhibited significant increases in the strain-hardening exponent with increasing neutron irradiation level.

  13. The Use of a Simple Enzyme Assay in 'Seed-Hardening' Studies

    ERIC Educational Resources Information Center

    Ead, J.; Devonald, V. G.

    1975-01-01

    Describes a single technique for an enzyme assay of catalase. The method shows that vegetable seeds submitted to pre-sowing 'hardening' cycles of imbition and drying have greater catalase activity and more rapid germination than do the controls. (LS)

  14. Monitoring of hardening and hygroscopic induced strains in a calcium phosphate bone cement using FBG sensor.

    PubMed

    Bimis, A; Karalekas, D; Bouropoulos, N; Mouzakis, D; Zaoutsos, S

    2016-07-01

    This study initially deals with the investigation of the induced strains during hardening stage of a self-setting calcium phosphate bone cement using fiber-Bragg grating (FBG) optical sensors. A complementary Scanning Electron Microscopy (SEM) investigation was also conducted at different time intervals of the hardening period and its findings were related to the FBG recordings. From the obtained results, it is demonstrated that the FBG response is affected by the microstructural changes taking place when the bone cement is immersed into the hardening liquid media. Subsequently, the FBG sensor was used to monitor the absorption process and hygroscopic response of the hardened and dried biocement when exposed to a liquid/humid environment. From the FBG-based calculated hygric strains as a function of moisture concentration, the coefficient of moisture expansion (CME) of the examined bone cement was obtained, exhibiting two distinct linear regions. PMID:26807773

  15. The effect of twinning on the work hardening behavior in Hafnium

    SciTech Connect

    Cerreta, E. K.; Gray, G. T. , III; Yablinsky, C.

    2004-01-01

    In many HCP metals, both twinning and slip are known to be important modes of deformation. However, the interaction of the two mechanisms and their effect on work hardening is not well understood. In hafnium, twinning and work hardening rates increase with increasing strain, increasing strain rate, and decreasing temperature. At low strains and strain rates and at higher temperatures, slip dominates deformation and rates of work hardening are relatively lower. To characterize the interaction of slip and twinning, Hf specimens were prestrained quasi-statically in compression at 77K, creating specimens that were heavily twinned. These specimens were subsequently reloaded at room temperature. Twinning within the microstructures was characterized optically and using transmission electron microscopy. The interaction of slip with the twins was investigated as a function of prestrain and correlated with the observed rates of work hardening.

  16. Calculation of residual stresses induced during laser quench-hardening of steel

    SciTech Connect

    Shishkovskii, I.V.

    1992-06-01

    We present a theoretical and numerical analysis of the quasi-stationary uncoupled problem of thermoelastic-plasticity with the goal of estimating the amount of residual stress in steel after laser quench-hardening. 18 refs., 3 figs.

  17. Simulation study of mechanical properties of bulk metallic glass systems: martensitic inclusions and twinned precipitates

    NASA Astrophysics Data System (ADS)

    Zaheri, A.; Abdeljawad, F.; Haataja, M.

    2014-12-01

    Monolithic bulk metallic glasses (BMGs) exhibit a unique combination of mechanical properties, such as high strength and large elasticity limits, but the lack of ductility is considered the main Achilles' heel of BMG systems. To increase the competitiveness of BMGs vis-à-vis conventional structural materials, the problem of catastrophic failure via intense plastic strain localization (‘shear banding’) has to be addressed. Recent experimental observations suggest that the addition of structural heterogeneities, in the form of crystalline particles, to BMG systems hinders the catastrophic propagation of shear bands and leads to enhanced ductility. These structural heterogeneities can be introduced by either forming BMG composites, where second-phase crystalline particles accommodate applied loads via martensitic transformation mechanisms, or developing glassy alloys that precipitate crystalline particles under deformation, a process by which further deformation can be sustained by twinning mechanisms in the crystalline phase. In this work, we present a non-linear continuum model capable of capturing the structural heterogeneity in the glassy phase and accounting for intrinsic work hardening via martensitic transformations in second-phase reinforcements in BMG composites and deformation twinning in precipitated crystalline particles. Simulation results reveal that in addition to intrinsic work hardening in the crystalline phase, particle size greatly affects the overall mechanical behavior of these BMG systems. The precipitation of crystalline particles in monolithic BMGs yields two-phase microstructures that promote more homogeneous deformation, delay the propagation of incipient shear bands, and ultimately result in improved ductility characteristics.

  18. Effect of heat treatment on precipitation on V-5Cr-5Ti heat BL63

    SciTech Connect

    Gelles, D.S.; Li, H.

    1996-04-01

    The microstructures of V-5Cr-5Ti heat BL63 are compared following heat treatments at 1125{degrees}C for 1 h and 1125{degrees}C for 1 h followed by 890{degrees}C for 24 h. Following the 890{degrees}C treatment, precipitate density was increased due to the presence of a moderate density of highly elongated particles. Microchemical analysis showed that these particles often contained both Ti and V, some particles showed minor amounts of Si, S, and P, but it was also possible to show that these precipitates were enriched in O rather than C or N. Following the 1125{degrees}C heat treatment, only Si was found as a minor impurity in large particles, but S could be identified at grain boundaries, which were coated with a fine distribution of precipitates. The embrittlement observed is ascribed to a combination of interstitial solid solution hardening and grain boundary embrittlement, with interstitial hardening likely the dominant factor.

  19. Cellular Composites with Ambient and Autoclaved Type of Hardening with Application of Nanostructured Binder

    NASA Astrophysics Data System (ADS)

    Nelyubova, V.; Pavlenko, N.; Netsvet, D.

    2015-11-01

    The research presents the dimensional and structural characteristics of nonhydrational hardening binders - nanostructured binders. Rational areas of their use in composites for construction purposes are given. The paper presents the results of the development of natural hardening foam concrete and aerated autoclaved concrete for thermal insulating and construction and thermal insulating purposes. Thus nanostructured binder (NB) in the composites was used as a primary binder and a high reactive modifier.

  20. Strain-hardening in nano-structured single phase steels: mechanisms and control.

    PubMed

    Bouaziz, O; Barbier, D

    2012-11-01

    The detrimental effect of grain size refinement on the strain hardening is highlighted in single phase steels. A physical based approach for understanding the underlying mechanisms is presented. In order to overcome this limitation a promising metallurgical route exploiting the thermal stability of mechanically induced twins in austenitic steels has been successfully applied to a stainless grade confirming the opportunity to get nano-structured alloys exhibiting high yield stress with high strain-hardening. PMID:23421275

  1. Direct Resistance Joule Heating of Al-10 pct Si-Coated Press Hardening Steel

    NASA Astrophysics Data System (ADS)

    Lee, Chang Wook; Choi, Won Seok; Cho, Yeol Rae; De Cooman, Bruno C.

    2016-06-01

    Various rapid heating methods have been developed to increase the productivity of press hardening steel. One of these methods is direct resistance Joule heating. This heating method results in the melting of the surface coating and the formation of a persistent liquid trail as a result of the high thermal conductivity and low melting temperature of the Al-10 pct Si alloy coating. This can be addressed by an alloying preheating treatment prior to the press hardening process.

  2. Method for determining the hardness of strain hardening articles of tungsten-nickel-iron alloy

    DOEpatents

    Wallace, Steven A.

    1984-01-01

    The present invention is directed to a rapid nondestructive method for determining the extent of strain hardening in an article of tungsten-nickel-iron alloy. The method comprises saturating the article with a magnetic field from a permanent magnet, measuring the magnetic flux emanating from the article, comparing the measurements of the magnetic flux emanating from the article with measured magnetic fluxes from similarly shaped standards of the alloy with known amounts of strain hardening to determine the hardness.

  3. Direct Resistance Joule Heating of Al-10 pct Si-Coated Press Hardening Steel

    NASA Astrophysics Data System (ADS)

    Lee, Chang Wook; Choi, Won Seok; Cho, Yeol Rae; De Cooman, Bruno C.

    2016-03-01

    Various rapid heating methods have been developed to increase the productivity of press hardening steel. One of these methods is direct resistance Joule heating. This heating method results in the melting of the surface coating and the formation of a persistent liquid trail as a result of the high thermal conductivity and low melting temperature of the Al-10 pct Si alloy coating. This can be addressed by an alloying preheating treatment prior to the press hardening process.

  4. Hardening of the surface layers of a hollow billet formed by centrifugal casting

    NASA Astrophysics Data System (ADS)

    Chumanov, V. I.; Chumanov, I. V.; Anikeev, A. N.; Garifulin, R. R.

    2010-12-01

    One of the methods to increase the mechanical properties of steel is its hardening via the introduction of a refractory fine-grained phase into a melt. A method of fabrication of a tube blank by centrifugal casting accompanied by hardening with a refractory phase is considered. The introduction of fine tungsten and silicon carbides is shown to improve the structure of grade 15 steel and to increase the wear resistance of a tube blank made of this steel.

  5. A Review of NASA's Radiation-Hardened Electronics for Space Environments Project

    NASA Technical Reports Server (NTRS)

    Keys, Andrew S.; Adams, James H.; Patrick, Marshall C.; Johnson, Michael A.; Cressler, John D.

    2008-01-01

    NASA's Radiation Hardened Electronics for Space Exploration (RHESE) project develops the advanced technologies required to produce radiation hardened electronics, processors, and devices in support of the requirements of NASA's Constellation program. Over the past year, multiple advancements have been made within each of the RHESE technology development tasks that will facilitate the success of the Constellation program elements. This paper provides a brief review of these advancements, discusses their application to Constellation projects, and addresses the plans for the coming year.

  6. Investigation of Clusters in Medium Carbon Secondary Hardening Ultra-high-strength Steel After Hardening and Aging Treatments

    NASA Astrophysics Data System (ADS)

    Veerababu, R.; Balamuralikrishnan, R.; Muraleedharan, K.; Srinivas, M.

    2015-06-01

    Clusters, containing between 10 and 1000 atoms, have been investigated in a martensitic secondary hardening ultra-high-strength steel austenitized at 1173 K (900 °C) for 1 hour and tempered at either 768 K or 783 K (495 °C or 510 °C) for 4 or 8 hours using 3D atom probe. The presence of clusters was unambiguously established by comparing the observed spatial distribution of the different alloying elements against the corresponding distribution expected for a random solid solution. Maximum separation envelope method has been used for delineating the clusters from the surrounding "matrix." Statistical analysis was used extensively for size and composition analyses of the clusters. The clusters were found to constitute a significant fraction accounting for between 1.14 and 2.53 vol pct of the microstructure. On the average, the clusters in the 783 K (510 °C) tempered sample were coarser by ~65 pct, with an average diameter of 2.26 nm, relative to the other samples. In all samples, about 85 to 90 pct of the clusters have size less than 2 nm. The percentage frequency histograms for carbon content of the clusters in 768 K and 783 K (495 °C and 510 °C) tempered samples revealed that the distribution shifts toward higher carbon content when the tempering temperature is higher. It is likely that the presence of these clusters exerts considerable influence on the strength and fracture toughness of the steel.

  7. Deformation and strain hardening of different steels in impact dominated systems

    SciTech Connect

    Rojacz, H.; Mozdzen, G.; Winkelmann, H.

    2014-04-01

    Strain hardening is a common technique to exploit the full potential of materials in diverse applications. Single impact studies were performed to evaluate work hardening effects of different steels, correlated to their deformation at different energy and momentum levels. Three different steels were examined regarding their forming behavior and their tendency to strain harden in impact loading conditions, revealing different intensities of hardness increase, deformation and coinciding microstructural changes. Detailed studies in the deformed zone such as micro hardness mappings were performed to reveal the materials hardness increase in the deformed zones. Additionally high resolution scanning electron microscopy (HRSEM) supported by electron backscatter diffraction (EBSD) was used to determine microstructural changes. Results indicate, that the influence of different velocities/strain rates at constant energy levels cannot be neglected for the strain hardening behavior of steels and provide data for a better control of the hardness increase in impact dominated materials fabrication operations. - Highlights: • Deformation and strain hardening behaviour of three different steels. • Influence of impact energies and momenta on the strain hardening. • Hardness increase and depth controllable by momentum and energy.

  8. Microstructural Evolution of the 55 Wt Pct Al-Zn Coating During Press Hardening

    NASA Astrophysics Data System (ADS)

    Lee, Chang Wook; De Cooman, Bruno Charles

    2014-09-01

    Press hardening is increasingly being used to produce ultra-high strength steel parts for passenger cars. Al-Si, Zn, and Zn-alloy coatings have been used to provide corrosion protection to press hardening steel grades. The use of coatings has drawbacks such as coating delamination or liquid metal-induced embrittlement. In the present work, the microstructural evolution of Al-Zn coating during press hardening was studied. The 55 wt pct Al-Zn coating can in principle provide both Al barrier protection and Zn cathodic protection to press hardened steel. During the heat treatment associated with the press hardening, the 55 wt pct Al-Zn alloy coating is converted to an intermetallic surface layer of Fe2Al5 and a FeAl intermetallic diffusion layer. The Zn is separated from both intermetallic compounds and accumulates at grain boundaries and at the surface. This Zn separation process is beneficial in terms of providing cathodic protection to Al-Zn coated press hardening steel.

  9. Comparative Tensile Flow and Work-Hardening Behavior of 9 Pct Chromium Ferritic-Martensitic Steels in the Framework of the Estrin-Mecking Internal-Variable Approach

    NASA Astrophysics Data System (ADS)

    Choudhary, B. K.; Christopher, J.

    2016-06-01

    The comparative tensile flow and work-hardening behavior of P9 steel in two different product forms, normalized and tempered plate and thick section tube plate forging, and P91 steel were investigated in the framework of the dislocation dynamics based Estrin-Mecking (E-M) one-internal-variable approach. The analysis indicated that the flow behavior of P9 and P91 steels was adequately described by the E-M approach in a wide range of temperatures. It was suggested that dislocation dense martensite lath/cell boundaries and precipitates together act as effective barriers to dislocation motion in P9 and P91 steels. At room and intermediate temperatures, the evolution of the internal-state variable, i.e., the dislocation density with plastic strain, exhibited insignificant variations with respect to temperature. At high temperatures, a rapid evolution of dislocation density with plastic strain toward saturation with increasing temperature was observed. The softer P9 steel tube plate forging exhibited higher work hardening in terms of larger gains in the dislocation density and flow stress contribution from dislocations than the P9 steel plate and P91 steel at temperatures ranging from 300 K to 873 K (27 °C to 600 °C). The evaluation of activation energy suggests that the deformation is controlled by cross-slip of dislocations at room and intermediate temperatures, and climb of dislocations at high temperatures. The relative influence of initial microstructure on flow and work-hardening parameters associated with the E-M approach was discussed in the three temperature regimes displayed by P9 and P91 steels.

  10. Calibration free beam hardening correction for cardiac CT perfusion imaging

    NASA Astrophysics Data System (ADS)

    Levi, Jacob; Fahmi, Rachid; Eck, Brendan L.; Fares, Anas; Wu, Hao; Vembar, Mani; Dhanantwari, Amar; Bezerra, Hiram G.; Wilson, David L.

    2016-03-01

    Myocardial perfusion imaging using CT (MPI-CT) and coronary CTA have the potential to make CT an ideal noninvasive gate-keeper for invasive coronary angiography. However, beam hardening artifacts (BHA) prevent accurate blood flow calculation in MPI-CT. BH Correction (BHC) methods require either energy-sensitive CT, not widely available, or typically a calibration-based method. We developed a calibration-free, automatic BHC (ABHC) method suitable for MPI-CT. The algorithm works with any BHC method and iteratively determines model parameters using proposed BHA-specific cost function. In this work, we use the polynomial BHC extended to three materials. The image is segmented into soft tissue, bone, and iodine images, based on mean HU and temporal enhancement. Forward projections of bone and iodine images are obtained, and in each iteration polynomial correction is applied. Corrections are then back projected and combined to obtain the current iteration's BHC image. This process is iterated until cost is minimized. We evaluate the algorithm on simulated and physical phantom images and on preclinical MPI-CT data. The scans were obtained on a prototype spectral detector CT (SDCT) scanner (Philips Healthcare). Mono-energetic reconstructed images were used as the reference. In the simulated phantom, BH streak artifacts were reduced from 12+/-2HU to 1+/-1HU and cupping was reduced by 81%. Similarly, in physical phantom, BH streak artifacts were reduced from 48+/-6HU to 1+/-5HU and cupping was reduced by 86%. In preclinical MPI-CT images, BHA was reduced from 28+/-6 HU to less than 4+/-4HU at peak enhancement. Results suggest that the algorithm can be used to reduce BHA in conventional CT and improve MPI-CT accuracy.

  11. BAE Systems Radiation Hardened SpaceWire ASIC and Roadmap

    NASA Technical Reports Server (NTRS)

    Berger, Richard; Milliser, Myrna; Kapcio, Paul; Stanley, Dan; Moser, David; Koehler, Jennifer; Rakow, Glenn; Schnurr, Richard

    2006-01-01

    An Application Specific Integrated Circuit (ASIC) that implements the SpaceWire protocol has been developed in a radiation hardened 0.25 micron CMOS, technology. This effort began in March 2003 as a joint development between the NASA Goddard Space Flight Center (GSFC) and BAE Systems. The BAE Systems SpaceWire ASlC is comprised entirely of reusable core elements, many of which are already flight-proven. It incorporates a 4-port SpaceWire router with two local ports, dual PC1 bus interfaces, a microcontroller, 32KB of internal memory, -and a memory controller for additional external memory use. The SpaceWire ASlC is planned for use on both the Geostationary Operational Environmental Satellites (GOES)-R and the Lunar Reconnaissance Orbiter (LRO). Engineering parts have already been delivered to both programs. This paper discusses the SpaceWire protocol and those elements of it that have been built into the current SpaceWire reusable core. There are features within the core that go beyond the current standard that can be enabled or disabled by the user and these will be described. The adaptation of SpaceWire to BAE Systems' On Chip Bus (OCB) for compatibility with the other reusable cores will be discussed. Optional configurations within user systems will be shown. The physical imp!ementation of the design will be described and test results from the hardware will be discussed. Finally, the BAE Systems roadmap for SpaceWire developments will be discussed, including some products already in design as well as longer term plans.

  12. Microstructure of hardened and softened zirconia after xenon implantation

    SciTech Connect

    Fleischer, E.L.; Norton, M.G.; Zaleski, M.A. ); Hertl, W. ); Carter, C.B.; Mayer, J.W. )

    1991-09-01

    Ion-channeling and transmission electron microscopy (TEM) techniques were used to examine the microstructure of single-crystal Y{sub 2}O{sub 3} stabilized cubic zirconia (YSZ) after implantation with 240 keV Xe{sup +} ions. The observed microstructure was related to Knoop indentation hardness measurements. These measurements showed an increase in hardness for low ion-doses, reaching some maximum value, then a decrease in hardness at higher doses. In the hardening regime, below 7.5{times}10{sup 15} Xe{sup +}/cm{sup 2}, point defects and dislocation networks were observed by TEM. Ion-channeling showed a corresponding increase in damage as a function of ion-dose. For doses between 7.5{times}10{sup 15} and 3{times}10{sup 16} Xe{sup +}/cm{sup 2} the hardness falls, and the amount of damage, measured with ion-channeling, reaches a limiting value at less than complete damage. In this dose range the Xe concentration continues to increase beyond the dose where the amount of damage saturates. For high doses, greater than 3{times}10{sup 16} Xe{sup +}/cm{sup 2}, where softening of the zirconia occurs, additional reflections appear in the electron diffraction pattern that are consistent with the lattice parameter of solid Xe. A diffuse ring is also visible; this is believed to be due to the presence of fluid Xe. Both ion-channeling and TEM show that a significant amount of monocrystalline zirconia remains even up to doses of 1{times}10{sup 17} Xe{sup +}/cm{sup 2}. There is also evidence for the presence of recrystallized zirconia at the high doses. Since so much crystalline material remains, it seems that amorphization of the zirconia is not the dominant cause of the softening at high doses.

  13. Mechanical properties and strengthening of a Ni-25Mo-8Cr alloy containing Ni{sub 2}(Mo,Cr) precipitates

    SciTech Connect

    Kumar, M.; Vasudevan, V.K.

    1996-12-01

    The mechanical properties and mechanisms of deformation and strengthening of Haynes Alloy 242{sup tm}, a nominal Ni-25Mo-8Cr (in wt%) containing Ni{sub 2}(Mo,Cr) precipitates in a face-centered cubic matrix, are reported. Both solution treated, as well as aged samples (550--750 C, 1--1,200 h) were deformed to permanent strains of 1 and 6% in compression and to failure in tension. The deformation structures were observed by transmission electron microscopy. A two-fold increase in strength and tremendous strain hardening are observed as the short-range (SRO) to long-range ordering (LRO) transformation proceeds, although ductility remains high even in well-aged samples. Major contribution to strengthening and strain hardening comes from the precipitation of a high volume fraction of Ni{sub 2}(Mo,Cr) precipitates, with hardening in the solution treated samples and those aged for short periods being associated with the presence of SRO in the matrix. A transition in deformation mode, from glide of unit dislocations in planar arrays to profuse twinning, is observed as a function of aging time and imposed strain, twinning being observed in samples containing Ni{sub 2}(Mo,Cr) precipitates. A semi-quantitative model developed on the basis of precipitate size and mode of deformation (shearing, twinning, bypassing) is able to satisfactorily account for this transition. A presentation and discussion of these results, as well as those of the mechanisms of strengthening and strain hardening, are provided.

  14. Methodology for the evaluation of yield strength and hardening behavior of metallic materials by indentation with spherical tip

    NASA Astrophysics Data System (ADS)

    Ma, Dejun; Ong, Chung Wo; Lu, Jian; He, Jiawen

    2003-07-01

    This article presents a methodology for evaluating the yield strength and hardening behavior of metallic materials by spherical indentation. Two types of assumed material behaviors with a pure elastic-Hollomon's power law hardening and a pure elastic-linear hardening were considered separately in the models of spherical indentation. The numerical relationships between the material properties and indentation responses were established on the basis of dimensional and finite element analysis. As the first approximation to the real plastic flow properties, the yield strengths and hardening behaviors determined from the spherical indentation loading curve and the numerical relationships were used to derive the intersecting points between Hollomon's power law hardening curve and linear hardening line. Through proceeding the three parameter's regression analysis with Swift's power law function for the intersecting points determined at different maximum indentation depths, the final yield strength and hardening behavior of tested material can be obtained. The validation of this method was examined by investigating three groups of materials with near linear hardening behavior, near Hollomon's power law hardening behavior, and initial yield plateau. It is concluded that the proposed method is applicable to a wide variety of materials which exhibit separate hardening behaviors.

  15. Nucleation and Precipitation Strengthening in Dilute Al-Ti and Al-Zr Alloys

    NASA Astrophysics Data System (ADS)

    Knipling, Keith E.; Dunand, David C.; Seidman, David N.

    2007-10-01

    Two conventionally solidified Al-0.2Ti alloys (with 0.18 and 0.22 at. pct Ti) exhibit no hardening after aging up to 3200 hours at 375 °C or 425 °C. This is due to the absence of Al3Ti precipitation, as confirmed by electron microscopy and electrical conductivity measurements. By contrast, an Al-0.2Zr alloy (with 0.19 at. pct Zr) displays strong age hardening at both temperatures due to precipitation of Al3Zr (L12) within Zr-enriched dendritic regions. This discrepancy between the two alloys is explained within the context of the equilibrium phase diagrams: (1) the disparity in solid and liquid solubilities of Ti in α-Al is much greater than that of Zr in α-Al; and (2) the relatively small liquid solubility of Ti in α-Al limits the amount of solute retained in solid solution during solidification, while the comparatively high solid solubility reduces the supersaturation effecting precipitation during post-solidification aging. The lattice parameter mismatch of Al3Ti (L12) with α-Al is also larger than that of Al3Zr (L12), further hindering nucleation of Al3Ti. Classical nucleation theory indicates that the minimum solute supersaturation required to overcome the elastic strain energy of Al3Ti nuclei cannot be obtained during conventional solidification of Al-Ti alloys (unlike for Al-Zr alloys), thus explaining the absence of Al3Ti precipitation and the presence of Al3Zr precipitation.

  16. Atom probe study of the carbon distribution in a hardened martensitic hot-work tool steel X38CrMoV5-1.

    PubMed

    Lerchbacher, Christoph; Zinner, Silvia; Leitner, Harald

    2012-07-01

    The microstructure of the hardened common hot-work tool steel X38CrMoV5-1 has been characterized by atom probe tomography with the focus on the carbon distribution. Samples quenched with technically relevant cooling parameters λ from 0.1 (30 K/s) to 12 (0.25 K/s) have been investigated. The parameter λ is an industrially commonly used exponential cooling parameter, representing the cooling time from 800 to 500 °C in seconds divided with hundred. In all samples pronounced carbon segregation to dislocations and cluster formation could be observed after quenching. Carbon enriched interlath films with peak carbon levels of 6-10 at.%, which have been identified to be retained austenite by TEM, show a thickness increase with increasing λ. Therefore, the fraction of total carbon staying in the austenite grows. This carbon is not available for the tempering induced precipitation of secondary carbides in the bulk. Through all samples no segregation of any substitutional elements takes place. Charpy impact testing and fracture surface analysis of the hardened samples reveal the cooling rate induced microstructural distinctions. PMID:22391101

  17. An Extended Age-Hardening Model for Al-Mg-Si Alloys Incorporating the Room-Temperature Storage and Cold Deformation Process Stages

    NASA Astrophysics Data System (ADS)

    Myhr, Ole Runar; Grong, Øystein; Schäfer, Carmen

    2015-12-01

    In this article, a new age-hardening model for Al-Mg-Si alloys is presented (named NaMo-Version 2), which takes into account the combined effect of cold deformation and prolonged room-temperature storage on the subsequent response to artificial aging. As a starting point, the original physical framework of NaMo-Version 1 is revived and used as a basis for the extension. This is permissible, since a more in-depth analysis of the underlying particle-dislocation interactions confirms previous expectations that the simplifying assumption of spherical precipitates is not crucial for the final outcome of the calculations, provided that the yield strength model is calibrated against experimental data. At the same time, the implementation of the Kampmann-Wagner formalism means that the different microstructure models can be linked together in a manner that enforces solute partitioning and competition between the different hardening phases which form during aging ( e.g., clusters, β″ and β'). In a calibrated form, NaMo-Version 2 exhibits a high degree of predictive power, as documented by comparison with experiments, using both dedicated nanostructure and yield strength data as a basis for the validation. Hence, the model is deemed to be well-suited for simulation of thermomechanical processing of Al-Mg-Si alloys involving cold-working operations like sheet forming and stretch bending in combination with heat treatment and welding.

  18. Quantitative experimental determination of the solid solution hardening potential of rhenium, tungsten and molybdenum in single-crystal nickel-based superalloys

    DOE PAGESBeta

    Fleischmann, Ernst; Miller, Michael K.; Affeldt, Ernst; Glatzel, Uwe

    2015-01-31

    Here, the solid-solution hardening potential of the refractory elements rhenium, tungsten and molybdenum in the matrix of single-crystal nickel-based superalloys was experimentally quantified. Single-phase alloys with the composition of the nickel solid-solution matrix of superalloys were cast as single crystals, and tested in creep at 980 °C and 30–75 MPa. The use of single-phase single-crystalline material ensures very clean data because no grain boundary or particle strengthening effects interfere with the solid-solution hardening. This makes it possible to quantify the amount of rhenium, tungsten and molybdenum necessary to reduce the creep rate by a factor of 10. Rhenium is moremore » than two times more effective for matrix strengthening than either tungsten or molybdenum. The existence of rhenium clusters as a possible reason for the strong strengthening effect is excluded as a result of atom probe tomography measurements. If the partitioning coefficient of rhenium, tungsten and molybdenum between the γ matrix and the γ' precipitates is taken into account, the effectiveness of the alloying elements in two-phase superalloys can be calculated and the rhenium effect can be explained.« less

  19. Quantitative experimental determination of the solid solution hardening potential of rhenium, tungsten and molybdenum in single-crystal nickel-based superalloys

    SciTech Connect

    Fleischmann, Ernst; Miller, Michael K.; Affeldt, Ernst; Glatzel, Uwe

    2015-01-31

    Here, the solid-solution hardening potential of the refractory elements rhenium, tungsten and molybdenum in the matrix of single-crystal nickel-based superalloys was experimentally quantified. Single-phase alloys with the composition of the nickel solid-solution matrix of superalloys were cast as single crystals, and tested in creep at 980 °C and 30–75 MPa. The use of single-phase single-crystalline material ensures very clean data because no grain boundary or particle strengthening effects interfere with the solid-solution hardening. This makes it possible to quantify the amount of rhenium, tungsten and molybdenum necessary to reduce the creep rate by a factor of 10. Rhenium is more than two times more effective for matrix strengthening than either tungsten or molybdenum. The existence of rhenium clusters as a possible reason for the strong strengthening effect is excluded as a result of atom probe tomography measurements. If the partitioning coefficient of rhenium, tungsten and molybdenum between the γ matrix and the γ' precipitates is taken into account, the effectiveness of the alloying elements in two-phase superalloys can be calculated and the rhenium effect can be explained.

  20. Phase chemistry and precipitation reactions in maraging steels: Part 3. Model alloys

    SciTech Connect

    Sha, W. .Department of Materials Science and Metallurgy); Cerezo, A.; Smith, G.D.W. . Department of Materials)

    1993-06-01

    This article describes studies of phase transformations during aging in a variety of model maraging steels. Atom-probe field-ion microscopy (APFIM) was the main research technique employed. Thermochemical calculation was also used during the course of the work. The composition and morphology of precipitates were compared in several maraging systems aged at different temperatures for different times to investigate the aging sequence. The APFIM results are compared with studies by other workers using different experimental techniques. In Fe-Ni(-Co)-Mo model alloys, [omega] phase and Fe[sub 7]Mo[sub 6] [mu] phase have been found to contribute to age hardening at different stages of aging; no evidence was found for the existence of Mo-rich clusters in the as-quenched Fe-Ni-Co-Mo alloy. In a high-Si Cr-containing steel, Ti[sub 6]Si[sub 7]Ni[sub 16]G phase and Ni[sub 3]Ti have been found to contribute to age hardening; reverted austenite was found after aging for 5 hours at 520 [degree]C. In a Mn-containing steel, Fe[sub 2]Mo Laves phase and a structurally uncertain phase with a composition of Fe[sub 45]Mn[sub 32]Co[sub 5]Mo[sub 19] have been found to contribute to age hardening.

  1. Deformation twinning induced decomposition of lamellar LPSO structure and its re-precipitation in an Mg-Zn-Y alloy

    NASA Astrophysics Data System (ADS)

    Shao, X. H.; Zheng, S. J.; Chen, D.; Jin, Q. Q.; Peng, Z. Z.; Ma, X. L.

    2016-07-01

    The high hardness or yield strength of an alloy is known to benefit from the presence of small-scale precipitation, whose hardening effect is extensively applied in various engineering materials. Stability of the precipitates is of critical importance in maintaining the high performance of a material under mechanical loading. The long period stacking ordered (LPSO) structures play an important role in tuning the mechanical properties of an Mg-alloy. Here, we report deformation twinning induces decomposition of lamellar LPSO structures and their re-precipitation in an Mg-Zn-Y alloy. Using atomic resolution scanning transmission electron microscopy (STEM), we directly illustrate that the misfit dislocations at the interface between the lamellar LPSO structure and the deformation twin is corresponding to the decomposition and re-precipitation of LPSO structure, owing to dislocation effects on redistribution of Zn/Y atoms. This finding demonstrates that deformation twinning could destabilize complex precipitates. An occurrence of decomposition and re-precipitation, leading to a variant spatial distribution of the precipitates under plastic loading, may significantly affect the precipitation strengthening.

  2. Deformation twinning induced decomposition of lamellar LPSO structure and its re-precipitation in an Mg-Zn-Y alloy.

    PubMed

    Shao, X H; Zheng, S J; Chen, D; Jin, Q Q; Peng, Z Z; Ma, X L

    2016-01-01

    The high hardness or yield strength of an alloy is known to benefit from the presence of small-scale precipitation, whose hardening effect is extensively applied in various engineering materials. Stability of the precipitates is of critical importance in maintaining the high performance of a material under mechanical loading. The long period stacking ordered (LPSO) structures play an important role in tuning the mechanical properties of an Mg-alloy. Here, we report deformation twinning induces decomposition of lamellar LPSO structures and their re-precipitation in an Mg-Zn-Y alloy. Using atomic resolution scanning transmission electron microscopy (STEM), we directly illustrate that the misfit dislocations at the interface between the lamellar LPSO structure and the deformation twin is corresponding to the decomposition and re-precipitation of LPSO structure, owing to dislocation effects on redistribution of Zn/Y atoms. This finding demonstrates that deformation twinning could destabilize complex precipitates. An occurrence of decomposition and re-precipitation, leading to a variant spatial distribution of the precipitates under plastic loading, may significantly affect the precipitation strengthening. PMID:27435638

  3. Deformation twinning induced decomposition of lamellar LPSO structure and its re-precipitation in an Mg-Zn-Y alloy

    PubMed Central

    Shao, X. H.; Zheng, S. J.; Chen, D.; Jin, Q. Q.; Peng, Z. Z.; Ma, X. L.

    2016-01-01

    The high hardness or yield strength of an alloy is known to benefit from the presence of small-scale precipitation, whose hardening effect is extensively applied in various engineering materials. Stability of the precipitates is of critical importance in maintaining the high performance of a material under mechanical loading. The long period stacking ordered (LPSO) structures play an important role in tuning the mechanical properties of an Mg-alloy. Here, we report deformation twinning induces decomposition of lamellar LPSO structures and their re-precipitation in an Mg-Zn-Y alloy. Using atomic resolution scanning transmission electron microscopy (STEM), we directly illustrate that the misfit dislocations at the interface between the lamellar LPSO structure and the deformation twin is corresponding to the decomposition and re-precipitation of LPSO structure, owing to dislocation effects on redistribution of Zn/Y atoms. This finding demonstrates that deformation twinning could destabilize complex precipitates. An occurrence of decomposition and re-precipitation, leading to a variant spatial distribution of the precipitates under plastic loading, may significantly affect the precipitation strengthening. PMID:27435638

  4. Evaluation on the Effect of Composition on Radiation Hardening and Embrittlement in Model FeCrAl Alloys

    SciTech Connect

    Field, Kevin G.; Briggs, Samuel A.; Edmondson, Philip; Hu, Xunxiang; Littrell, Kenneth C.; Howard, Richard; Parish, Chad M.; Yamamoto, Yukinori

    2015-09-18

    networks acting as defect sinks, resulting in variations in the observed microstructures after irradiation. Dose trends were also observed, with increasing radiation dose promoting changes in the size and number density of the Cr-rich α' precipitates. Based on the microstructural analysis, performed tensile testing, and prior knowledge from FeCr literature it was hypothesized that the formation of the Cr-rich α' precipitates could lead to significant radiation-induced embrittlement in the alloys, and this could be composition dependent, a result which would mirror the trends observed for radiation-induced hardening. Due to the limited database on embrittlement in the FeCrAl alloy class after irradiation, a series of radiation experiments have been implemented. The overarching point of view within this report is the radiation tolerance of FeCrAl is complex, with many mechanisms and factors to be considered at once. Further development of the FeCrAl alloy class for enhanced accident tolerant applications requires detailed, single (or at least limited) variable experiments to fully comprehend and predict the performance of this alloy in LWRs. This report has been submitted as fulfillment of milestone M2FT-15OR0202321 titled, Summary report on the effect of composition on the irradiation embrittlement of Gen 1 ATF FeCrAl for the Department of Energy Office of Nuclear Energy, Advanced Fuel Campaign of the Fuel Cycle R&D program.

  5. The Strain-Hardening Behavior of TZAV-30 Alloy After Various Heat Treatments

    NASA Astrophysics Data System (ADS)

    Liang, S. X.; Yin, L. X.; Zheng, L. Y.; Ma, M. Z.; Liu, R. P.

    2016-02-01

    The Ti-Zr-Al-V series titanium alloys with excellent mechanical properties and low density exhibit tremendous application potential as structural materials in aviation, automotive, and navigation industries. The strain-hardening behavior of Ti-30Zr-5Al-3V (wt.%, TZAV-30) alloy with various heat treatments is investigated in this study. Experimental results show that strain-hardening behavior of the examined alloy depends on the heat treatment process. The average strain-hardening exponent, n, is approximately 0.061 for WA specimen (825 °C/0.5 h/water quenching + 600 °C/4 h/air cooling), 0.068 for FC (850 °C/0.5 h/furnace cooling), 0.121 for AC (850 °C/0.5 h/air cooling), and 0.412 for WQ (850 °C/0.5 h/water quenching). Analysis of strain-hardening rate versus true strain curves indicates that higher n of AC specimen results from the lower degradation rate of strain-hardening rate with strain, and the ultrahigh n of WQ specimen is attributed to the evident increase in strain-hardening rate at the true strain from 0.04 to 0.06. Phase constitution and microstructural analyses reveal that the n of the examined alloy with α + β phases increases with the increase in the relative content of the retained β phase but is independent of average thickness of α plates. The increase in strain-hardening rate in WQ specimen depends on metastable α″ martensite and martensitic transition induced by tensile stress.

  6. Determination of Constant Parameters of Copper as Power-Law Hardening Material at Different Test Conditions

    NASA Astrophysics Data System (ADS)

    Kowser, Md. A.; Mahiuddin, Md.

    2014-11-01

    In this paper a technique has been developed to determine constant parameters of copper as a power-law hardening material by tensile test approach. A work-hardening process is used to describe the increase of the stress level necessary to continue plastic deformation. A computer program is used to show the variation of the stress-strain relation for different values of stress hardening exponent, n and power-law hardening constant, α . Due to its close tolerances, excellent corrosion resistance and high material strength, in this analysis copper (Cu) has been selected as the material. As a power-law hardening material, Cu has been used to compute stress hardening exponent, n and power-law hardening constant, α from tensile test experiment without heat treatment and after heat treatment. A wealth of information about mechanical behavior of a material can be determined by conducting a simple tensile test in which a cylindrical specimen of a uniform cross-section is pulled until it ruptures or fractures into separate pieces. The original cross sectional area and gauge length are measured prior to conducting the test and the applied load and gauge deformation are continuously measured throughout the test. Based on the initial geometry of the sample, the engineering stress-strain behavior (stress-strain curve) can be easily generated from which numerous mechanical properties, such as the yield strength and elastic modulus, can be determined. A universal testing machine is utilized to apply the load in a continuously increasing (ramp) manner according to ASTM specifications. Finally, theoretical results are compared with these obtained from experiments where the nature of curves is found similar to each other. It is observed that there is a significant change of the value of n obtained with and without heat treatment it means the value of n should be determined for the heat treated condition of copper material for their applications in engineering fields.

  7. BOTANICAL ASPECTS OF ACIDIC PRECIPITATION

    EPA Science Inventory

    Acidic precipitation can be characterized as wet or frozen atmospheric deposition with a hydrogen ion concentration greater than 2.5 microequivalents liter-1. Acidic precipitation is perceived as a significant air pollution problem derived chiefly from combustion of fossil fuels,...

  8. Improved ethanol precipitation of DNA.

    PubMed

    Fregel, Rosa; González, Ana; Cabrera, Vicente M

    2010-04-01

    In this Short Communication, a shorter version of the standard DNA ethanol precipitation and purification protocol is described. It uses a mixture of 70% ethanol, 75 mM ammonium acetate and different concentrations of different carriers to perform DNA precipitation and washing in only one step. PMID:20336673

  9. Precipitation Process and Apparatus Therefor

    DOEpatents

    Stang, Jr, L C

    1950-12-05

    This invention concerns an apparatus for remotely-controlled precipitation and filtration operations. Liquid within a precipitation chamber is maintained above a porous member by introducing air beneath the member; pressure beneath the porous member is reduced to suck the liquid through the member and effect filtration.

  10. Acid precipitation in historical perspective

    SciTech Connect

    Cowling, E.B.

    1982-02-01

    The history of acid precipitation is traced from the first awareness of the problem in the mid-17th century to the present. An outline of the National Acid Precipitation Assessment program is also given, and the author makes recommendations for future research. (JMT)

  11. Precipitation in the Solar System

    ERIC Educational Resources Information Center

    McIntosh, Gordon

    2007-01-01

    As an astronomy instructor, I am always looking for commonly observed Earthly experiences to help my students and me understand and appreciate similar occurrences elsewhere in the solar system. Recently I wrote a short TPT article on frost. This paper is on the related phenomena of precipitation. Precipitation, so common on most of the Earth's…

  12. Resistivity Problems in Electrostatic Precipitation

    ERIC Educational Resources Information Center

    White, Harry J.

    1974-01-01

    The process of electrostatic precipitation has ever-increasing application in more efficient collection of fine particles from industrial air emissions. This article details a large number of new developments in the field. The emphasis is on high resistivity particles which are a common cause of poor precipitator performance. (LS)

  13. Innovative Structural Materials and Sections with Strain Hardening Cementitious Composites

    NASA Astrophysics Data System (ADS)

    Dey, Vikram

    The motivation of this work is based on development of new construction products with strain hardening cementitious composites (SHCC) geared towards sustainable residential applications. The proposed research has three main objectives: automation of existing manufacturing systems for SHCC laminates; multi-level characterization of mechanical properties of fiber, matrix, interface and composites phases using servo-hydraulic and digital image correlation techniques. Structural behavior of these systems were predicted using ductility based design procedures using classical laminate theory and structural mechanics. SHCC sections are made up of thin sections of matrix with Portland cement based binder and fine aggregates impregnating continuous one-dimensional fibers in individual or bundle form or two/three dimensional woven, bonded or knitted textiles. Traditional fiber reinforced concrete (FRC) use random dispersed chopped fibers in the matrix at a low volume fractions, typically 1-2% to avoid to avoid fiber agglomeration and balling. In conventional FRC, fracture localization occurs immediately after the first crack, resulting in only minor improvement in toughness and tensile strength. However in SHCC systems, distribution of cracking throughout the specimen is facilitated by the fiber bridging mechanism. Influence of material properties of yarn, composition, geometry and weave patterns of textile in the behavior of laminated SHCC skin composites were investigated. Contribution of the cementitious matrix in the early age and long-term performance of laminated composites was studied with supplementary cementitious materials such as fly ash, silica fume, and wollastonite. A closed form model with classical laminate theory and ply discount method, coupled with a damage evolution model was utilized to simulate the non-linear tensile response of these composite materials. A constitutive material model developed earlier in the group was utilized to characterize and

  14. Simulation and research on a 4T-cell based duplication redundancy SRAM for SEU radiation hardening

    NASA Astrophysics Data System (ADS)

    Xinhong, Hong; Liyang, Pan; Wendi, Zhang; Dongmei, Ji; Dong, Wu; Chen, Shen; Jun, Xu

    2015-11-01

    A novel 4T-cell based duplication redundancy SRAM is proposed for SEU radiation hardening applications. The memory cell is designed with a 65-nm low leakage process; the operation principle and the SEU radiation hardening mechanism are discussed in detail. The SEE characteristics and failure mechanism are also studied with a 3-D device simulator. The results show that the proposed SRAM structure exhibits high SEU hardening performance with a small cell size.

  15. Effect of strain rate on bake hardening response of BH220 steel

    NASA Astrophysics Data System (ADS)

    Das, Anindya; Tarafder, Soumitro; Sivaprasad, S.; Chakrabarti, Debalay

    2015-09-01

    This study aims at understanding the bake hardening ability of ultra low carbon BH220 steel at different strain rates. The as-received material has been pre-strained to four different levels and then deformed in tension under (a) as pre-strained state and (b) after baking at 170 ∘C for 20 minutes, at three different strain rates of 0.001, 0.1 and 100/s. In both the conditions, yield stress increased with pre-strain and strain rate, but bake hardening ability was found to decrease when strain rate was increased. The strain rate sensitivity of the material was also found to decrease with bake hardening. Generation of dislocation forests and their subsequent immobility during baking treatment enables them to act as long range obstacles during further deformation. At higher strain rates, less amount of dislocations are produced which can interact with themselves and produce hardening, because of which bake hardening ability and the strain rate drops. A dislocation based strengthening model, as proposed by Larour et al. 2011 [7], was used to predict the yield stress values obtained at different conditions. The equation produced excellent co-relation with the experimental data.

  16. Identifying Deformation and Strain Hardening Behaviors of Nanoscale Metallic Multilayers Through Nano-wear Testing

    DOE PAGESBeta

    Economy, David Ross; Mara, Nathan A.; Schoeppner, R.; Schultz, Bradley M.; Unocic, Raymond R.; Kennedy, Marian S.

    2016-01-13

    In complex loading conditions (e.g. sliding contact), mechanical properties, such as strain hardening and initial hardness, will dictate the long-term performance of materials systems. With this in mind, the strain hardening behaviors of Cu/Nb nanoscale metallic multilayer systems were examined by performing nanoindentation tests within nanoscratch wear boxes and undeformed, as-deposited regions. Both the architecture and substrate influence were examined by utilizing three different individual layer thicknesses (2, 20, and 100 nm) and two total film thicknesses (1 and 10 μm). After nano-wear deformation, multilayer systems with thinner layers showed less volume loss as measured by laser scanning microscopy. Additionally,more » the hardness of the deformed regions significantly rose with respect to the as-deposited measurements, which further increased with greater wear loads. Strain hardening exponents for multilayers with thinner layers (2 and 20 nm, n ≈ 0.018 and n ≈ 0.022 respectively) were less than was determined for 100 nm systems (n ≈ 0.041). These results suggest that singledislocation based deformation mechanisms observed for the thinner systems limit the extent of achievable strain hardening. This conclusion indicates that impacts of both architecture strengthening and strain hardening must be considered to accurately predict multilayer performance during sliding contact across varying length scales.« less

  17. ON THE SPECTRAL HARDENING AT {approx}>300 keV IN SOLAR FLARES

    SciTech Connect

    Li, G.; Kong, X.; Zank, G.; Chen, Y.

    2013-05-20

    It has long been noted that the spectra of observed continuum emissions in many solar flares are consistent with double power laws with a hardening at energies {approx}>300 keV. It is now widely believed that at least in electron-dominated events, the hardening in the photon spectrum reflects an intrinsic hardening in the source electron spectrum. In this paper, we point out that a power-law spectrum of electrons with a hardening at high energies can be explained by the diffusive shock acceleration of electrons at a termination shock with a finite width. Our suggestion is based on an early analytical work by Drury et al., where the steady-state transport equation at a shock with a tanh profile was solved for a p-independent diffusion coefficient. Numerical simulations with a p-dependent diffusion coefficient show hardenings in the accelerated electron spectrum that are comparable with observations. One necessary condition for our proposed scenario to work is that high-energy electrons resonate with the inertial range of the MHD turbulence and low-energy electrons resonate with the dissipation range of the MHD turbulence at the acceleration site, and the spectrum of the dissipation range {approx}k {sup -2.7}. A {approx}k {sup -2.7} dissipation range spectrum is consistent with recent solar wind observations.

  18. Beam hardening effects in grating-based x-ray phase-contrast imaging

    SciTech Connect

    Chabior, Michael; Donath, Tilman; David, Christian; Bunk, Oliver; Schuster, Manfred; Schroer, Christian; Pfeiffer, Franz

    2011-03-15

    Purpose: In this work, the authors investigate how beam hardening affects the image formation in x-ray phase-contrast imaging and consecutively develop a correction algorithm based on the results of the analysis. Methods: The authors' approach utilizes a recently developed x-ray imaging technique using a grating interferometer capable of visualizing the differential phase shift of a wave front traversing an object. An analytical description of beam hardening is given, highlighting differences between attenuation and phase-contrast imaging. The authors present exemplary beam hardening artifacts for a number of well-defined samples in measurements at a compact laboratory setup using a polychromatic source. Results: Despite the differences in image formation, the authors show that beam hardening leads to a similar reduction of image quality in phase-contrast imaging as in conventional attenuation-contrast imaging. Additionally, the authors demonstrate that for homogeneous objects, beam hardening artifacts can be corrected by a linearization technique, applicable to all kinds of phase-contrast methods using polychromatic sources. Conclusions: The evaluated correction algorithm is shown to yield good results for a number of simple test objects and can thus be advocated in medical imaging and nondestructive testing.

  19. New steels and methods for induction hardening of bearing rings and rollers

    SciTech Connect

    Ouchakov, B.K.; Shepeljakovsky, K.Z.

    1998-12-31

    The new method of through-surface hardening (TSH) of bearing rings and rollers was developed and used in Russia and former USSR. The principles of the method include the use of special steels of low or controlled hardenability, through-the-section induction of furnace heating and intense quenching of the parts by water stream in special devices. Due to the low hardenability of applied steels, the bearing rings and rollers have high-strength martensitic surface layer, combined with a core strengthened with a troostite and sorbite structure. High compressive residual stresses are formed in the martensitic surface layers. For a long time TSH has been successfully used for inner rings of bearings for railway car boxes, large rings and rollers of bearings for cement furnaces and rolling mills. Recently TSH was used for hollow rollers of railway bearings. For bearing rings made of SAE 52100 type high-carbon, chromium-alloyed steel a new method of low-deformation hardening was developed. The method is based on self-calibration of the rings during the quenching process and is intended for through hardening by induction heating and quenching by rapidly moved water stream.

  20. On the Spectral Hardening at gsim300 keV in Solar Flares

    NASA Astrophysics Data System (ADS)

    Li, G.; Kong, X.; Zank, G.; Chen, Y.

    2013-05-01

    It has long been noted that the spectra of observed continuum emissions in many solar flares are consistent with double power laws with a hardening at energies gsim300 keV. It is now widely believed that at least in electron-dominated events, the hardening in the photon spectrum reflects an intrinsic hardening in the source electron spectrum. In this paper, we point out that a power-law spectrum of electrons with a hardening at high energies can be explained by the diffusive shock acceleration of electrons at a termination shock with a finite width. Our suggestion is based on an early analytical work by Drury et al., where the steady-state transport equation at a shock with a tanh profile was solved for a p-independent diffusion coefficient. Numerical simulations with a p-dependent diffusion coefficient show hardenings in the accelerated electron spectrum that are comparable with observations. One necessary condition for our proposed scenario to work is that high-energy electrons resonate with the inertial range of the MHD turbulence and low-energy electrons resonate with the dissipation range of the MHD turbulence at the acceleration site, and the spectrum of the dissipation range ~k -2.7. A ~k -2.7 dissipation range spectrum is consistent with recent solar wind observations.