Local Structure and Short-Range Order in a NiCoCr Solid Solution Alloy

DOE PAGES

Zhang, F. X.; Zhao, Shijun; Jin, Ke; ...

2017-05-19

Multi-element solid solution alloys are intrinsically disordered on the atomic scale, and many of their advanced properties originate from the unique local structural characteristics. We measured the local structure of a NiCoCr solid solution alloy with X-ray/neutron total scattering and extended X-ray absorption fine structure (EXAFS) techniques. The atomic pair distribution function analysis (PDF) did not exhibit distinct structural distortion. But, EXAFS analysis suggested that the Cr atoms are favorably bonded with Ni and Co in the solid solution alloys. This short-range order (SRO) plays a role in the distinct low values of electrical and thermal conductivities in Ni-based solidmore » solution alloys when Cr is incorporated. Both the long-range and local structures of the NiCoCr alloy upon Ni ion irradiation were studied and an irradiation-induced enhancement of SRO was found.« less

Down-selection of candidate alloys for further testing of advanced replacement materials for LWR core internals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Was, Gary; Leonard, Keith J.; Tan, Lizhen

Life extension of the existing nuclear reactors imposes irradiation of high fluences to structural materials, resulting in significant challenges to the traditional reactor materials such as type 304 and 316 stainless steels. Advanced alloys with superior radiation resistance will increase safety margins, design flexibility, and economics for not only the life extension of the existing fleet but also new builds with advanced reactor designs. The Electric Power Research Institute (EPRI) teamed up with Department of Energy (DOE) Light Water Reactor Sustainability Program to initiate the Advanced Radiation Resistant Materials (ARRM) program, aiming to identify and develop advanced alloys with superiormore » degradation resistance in light water reactor (LWR)-relevant environments by 2024.« less

Evaluation of advanced austenitic alloys relative to alloy design criteria for steam service

DOE Office of Scientific and Technical Information (OSTI.GOV)

Swindeman, R.W.; Maziasz, P.J.; Bolling, E.

1990-05-01

The results are summarized for a 6-year activity on advanced austenitic stainless steels for heat recovery systems. Commercial, near-commercial, and developmental alloys were evaluated relative to criteria for metallurgical stability, fabricability, weldability, and mechanical strength. Fireside and steamside corrosion were also considered, but no test data were collected. Lean stainless steel alloys that were given special attention in the study were type 316 stainless steel, fine-grained type 347 stainless steel, 17-14CuMo stainless steel, Esshete 1250, Sumitomo ST3Cu{reg sign} stainless steel, and a group of alloys identified as HT-UPS (high-temperature, ultrafine-precipitation strengthened) steels that were basically 14Cr--16Ni--Mo steels modified by variousmore » additions of MC-forming elements. It was found that, by solution treating the MC-forming alloys to temperatures above 1150{degree}C and subsequently cold or warm working, excellent metallurgical stability and creep strength could be achieved. Test data to beyond 35,000 h were collected. The ability to clad the steels for improved fireside corrosion resistance was demonstrated. Weldability of the alloys was of concern, and hot cracking was found to be a problem in the HT-UPS alloys. By reducing the phosphorous content and selecting either CRE 16-8-2 stainless steel or alloy 556 filler metal, weldments were produced that had excellent strength and ductility. The major issues related to the development of the advanced alloys were identified and ways to resolve the issues suggested. 89 refs., 45 figs., 8 tabs.« less

NASA-UVA Light Aerospace Alloy and Structures Technology Program (LA2ST)

NASA Technical Reports Server (NTRS)

Gangloff, Richard P.; Scully, John R.; Stoner, Glenn E.; Thornton, Earl A.; Wawner, Franklin E., Jr.; Wert, John A.

1993-01-01

The NASA-UVA Light Aerospace Alloy and Structures Technology (LA2ST) Program continues a high level of activity. Progress achieved between 1 Jan. and 30 Jun. 1993 is reported. The objective of the LA2ST Program is to conduct interdisciplinary graduate student research on the performance of next generation, light weight aerospace alloys, composites, and thermal gradient structures in collaboration with NASA-Langley researchers. The following projects are addressed: environmental fatigue of Al-Li-Cu alloys; mechanisms of localized corrosion and environmental fracture in Al-Cu-Li-Mg-Ag alloy X2095 and compositional variations; the effect of zinc additions on the precipitation and stress corrosion cracking behavior of alloy 8090; hydrogen interactions with Al-Li-Cu alloy 2090 and model alloys; metastable pitting of aluminum alloys; cryogenic fracture toughness of Al-Cu-Li + In alloys; the fracture toughness of Weldalite (TM); elevated temperature cracking of advanced I/M aluminum alloys; response of Ti-1100/SCS-6 composites to thermal exposure; superplastic forming of Weldalite (TM); research to incorporate environmental effects into fracture mechanics fatigue life prediction codes such as NASA FLAGRO; and thermoviscoplastic behavior.

Advanced Class of FML on the Base Al-Li Alloy 1441 with Lower Density

NASA Astrophysics Data System (ADS)

Antipov, V. V.; Senatorova, O. G.; Lukina, N. F.

Structure, composition, properties combination of specimens and components, a number of technological parameters for production of advanced FML based on high-modulus Al-Li 1441 alloy (E 79 GPa) with reduced density (d 2.6 g/m3) and optimized adhesive prepreg reinforced with high-strength high-modulus VMP glass fibres are described. Service life 1441 alloy provides the possibility of manufacture of thin sheets (up to 0.3 mm), clad and unclad. Moreover, some experience on the usage of 1441 T1, T11 sheets and shapes in Be 200 and Be 103 aircraft was accumulated. The class of FML materials based on Al-Li alloy provide an 5% improvement in weight efficiency and stiffness of skin structures as compared with those made from FML with conventional Al-Cu-Mg (2024T3 a.o.) and Al-Zn-Mg-Cu (7475T76 a.o.) alloys.

NASA-UVA light aerospace alloy and structures technology program (LA2ST)

NASA Technical Reports Server (NTRS)

Starke, Edgar A., Jr.; Gangloff, Richard P.; Herakovich, Carl T.; Scully, John R.; Shiflet, Gary J.; Stoner, Glenn E.; Wert, John A.

1995-01-01

The NASA-UVa Light Aerospace Alloy and Structures Technology (LA2ST) Program was initiated in 1986 and continues with a high level of activity. Projects are being conducted by graduate students and faculty advisors in the Department of Materials Science and Engineering, as well as in the Department of Civil Engineering and Applied Mechanics, at the University of Virginia. Here, we report on progress achieved between July 1 and December 31, 1994. The objective of the LA2ST Program is to conduct interdisciplinary graduate student research on the performance of next generation, light-weight aerospace alloys, composites and thermal gradient structures in collaboration with NASA-Langley researchers. Specific technical objectives are presented for each research project. We generally aim to produce relevant data and basic understanding of material mechanical response, environmental/corrosion behavior, and microstructure; new monolithic and composite alloys; advanced processing methods; new solid and fluid mechanics analyses; measurement and modeling advances; and a pool of educated graduate students for aerospace technologies.

FY 2017-Influence of Sodium Environment on the Tensile Properties of Advanced Alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Natesan, K.; Li, Meimei; Chen, Wei-Ying

This report provides an update on the understanding of the effects of sodium exposures on tensile properties of advanced alloy 709 in support of the design and operation of structural components in sodium-cooled fast reactors (SFRs). The report is a Level 3 deliverable in FY17 (M3AT-17AN1602093), under the Work Package AT-17AN160209, “Sodium Compatibility” performed by Argonne National Laboratory (ANL), as part of Advanced Reactor Technologies Program. Three laboratory-size heats of Alloy 709 austenitic steel were investigated in liquid sodium environments at 550-650°C to understand its corrosion behaviour, microstructural evolution, and tensile properties. In addition, a commercial scale heat has beenmore » produced and hot-rolled into plates.« less

NASA-UVA Light Aerospace Alloy and Structures Technology Program: LA(2)ST

NASA Technical Reports Server (NTRS)

Gangloff, Richard P.; Haviland, John K.; Herakovich, Carl T.; Pilkey, Walter D.; Pindera, Marek-Jerzy; Scully, John R.; Stoner, Glenn E.; Thornton, Earl A.; Wawner, Franklin E., Jr.; Wert, John A.

1993-01-01

The NASA-UVA Light Aerospace Alloy and Structures Technology (LA(2)ST) Program continues a high level of activity, with projects being conducted by graduate students and faculty advisors in the Departments of Materials Science and Engineering, Civil Engineering and Applied Mechanics, and Mechanical and Aerospace Engineering at the University of Virginia. This work is funded by the NASA-Langley Research Center under Grant NAG-1-745. We report on progress achieved between July 1 and December 31, 1992. The objective of the LA(2)ST Program is to conduct interdisciplinary graduate student research on the performance of next generation, light weight aerospace alloys, composites and thermal gradient structures in collaboration with NASA-Langley researchers. Specific technical objectives are presented for each research project. We generally aim to produce relevant data and basic understanding of material mechanical response, corrosion behavior, and microstructure; new monolithic and composite alloys; advanced processing methods; new solid and fluid mechanics analyses; measurement advances; and critically, a pool of educated graduate students for aerospace technologies.

NASA-UVA light aerospace alloy and structures technology program (LA2ST)

NASA Technical Reports Server (NTRS)

Gangloff, Richard P.; Scully, John R.; Starke, Edgar A., Jr.; Stoner, Glenn E.; Thornton, Earl A.; Wawner, Franklin E., Jr.; Wert, John A.

1994-01-01

The NASA-UVA Light Aerospace Alloy and Structures Technology (LA2ST) Program was initiated in 1986, and continues a high level of activity, with projects being conducted by graduate students and faculty advisors in the Departments of Materials Science and Engineering, and Mechanical and Aerospace Engineering at the University of Virginia. This work is funded by the NASA-Langley Research Center under Grant NAG-1-745. Here, we report on progress achieved between July 1 and December 31, 1993. The objective of the LA2ST Program is to conduct interdisciplinary graduate student research on the performance of next generation, light weight aerospace alloys, composites and thermal gradient structures in collaboration with NASA-Langley researchers. Specific technical objectives are presented for each research project. We generally aim to produce relevant data and basic understanding of material mechanical response, environmental/corrosion behavior, and microstructure; new monolithic and composite alloys; advanced processing methods; new solid and fluid mechanics analyses; measurement and modeling advances; and critically, a pool of educated graduate students for aerospace technologies.

NASA-UVA light aerospace alloy and structures technology program (LA2ST)

NASA Astrophysics Data System (ADS)

Gangloff, Richard P.; Scully, John R.; Starke, Edgar A., Jr.; Stoner, Glenn E.; Thornton, Earl A.; Wawner, Franklin E., Jr.; Wert, John A.

1994-03-01

The NASA-UVA Light Aerospace Alloy and Structures Technology (LA2ST) Program was initiated in 1986, and continues a high level of activity, with projects being conducted by graduate students and faculty advisors in the Departments of Materials Science and Engineering, and Mechanical and Aerospace Engineering at the University of Virginia. This work is funded by the NASA-Langley Research Center under Grant NAG-1-745. Here, we report on progress achieved between July 1 and December 31, 1993. The objective of the LA2ST Program is to conduct interdisciplinary graduate student research on the performance of next generation, light weight aerospace alloys, composites and thermal gradient structures in collaboration with NASA-Langley researchers. Specific technical objectives are presented for each research project. We generally aim to produce relevant data and basic understanding of material mechanical response, environmental/corrosion behavior, and microstructure; new monolithic and composite alloys; advanced processing methods; new solid and fluid mechanics analyses; measurement and modeling advances; and critically, a pool of educated graduate students for aerospace technologies.

Oxidation-Reduction Resistance of Advanced Copper Alloys

NASA Technical Reports Server (NTRS)

Greenbauer-Seng, L. (Technical Monitor); Thomas-Ogbuji, L.; Humphrey, D. L.; Setlock, J. A.

2003-01-01

Resistance to oxidation and blanching is a key issue for advanced copper alloys under development for NASA's next generation of reusable launch vehicles. Candidate alloys, including dispersion-strengthened Cu-Cr-Nb, solution-strengthened Cu-Ag-Zr, and ODS Cu-Al2O3, are being evaluated for oxidation resistance by static TGA exposures in low-p(O2) and cyclic oxidation in air, and by cyclic oxidation-reduction exposures (using air for oxidation and CO/CO2 or H2/Ar for reduction) to simulate expected service environments. The test protocol and results are presented.

Code qualification of structural materials for AFCI advanced recycling reactors.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Natesan, K.; Li, M.; Majumdar, S.

2012-05-31

This report summarizes the further findings from the assessments of current status and future needs in code qualification and licensing of reference structural materials and new advanced alloys for advanced recycling reactors (ARRs) in support of Advanced Fuel Cycle Initiative (AFCI). The work is a combined effort between Argonne National Laboratory (ANL) and Oak Ridge National Laboratory (ORNL) with ANL as the technical lead, as part of Advanced Structural Materials Program for AFCI Reactor Campaign. The report is the second deliverable in FY08 (M505011401) under the work package 'Advanced Materials Code Qualification'. The overall objective of the Advanced Materials Codemore » Qualification project is to evaluate key requirements for the ASME Code qualification and the Nuclear Regulatory Commission (NRC) approval of structural materials in support of the design and licensing of the ARR. Advanced materials are a critical element in the development of sodium reactor technologies. Enhanced materials performance not only improves safety margins and provides design flexibility, but also is essential for the economics of future advanced sodium reactors. Code qualification and licensing of advanced materials are prominent needs for developing and implementing advanced sodium reactor technologies. Nuclear structural component design in the U.S. must comply with the ASME Boiler and Pressure Vessel Code Section III (Rules for Construction of Nuclear Facility Components) and the NRC grants the operational license. As the ARR will operate at higher temperatures than the current light water reactors (LWRs), the design of elevated-temperature components must comply with ASME Subsection NH (Class 1 Components in Elevated Temperature Service). However, the NRC has not approved the use of Subsection NH for reactor components, and this puts additional burdens on materials qualification of the ARR. In the past licensing review for the Clinch River Breeder Reactor Project (CRBRP

The Effect of Solution Heat Treatment on an Advanced Nickel-Base Disk Alloy

NASA Technical Reports Server (NTRS)

Gayda, J.; Gabb, T. P.; Kantzos, P. T.

2004-01-01

Five heat treat options for an advanced nickel-base disk alloy, LSHR, have been investigated. These included two conventional solution heat treat cycles, subsolvus/oil quench and supersolvus/fan cool, which yield fine grain and coarse grain microstructure disks respectively, as well as three advanced dual microstructure heat treat (DMHT) options. The DMHT options produce disks with a fine grain bore and a coarse grain rim. Based on an overall evaluation of the mechanical property data, it was evident that the three DMHT options achieved a desirable balance of properties in comparison to the conventional solution heat treatments for the LSHR alloy. However, one of the DMHT options, SUB/DMHT, produced the best set of properties, largely based on dwell crack growth data. Further evaluation of the SUB/DMHT option in spin pit experiments on a generic disk shape demonstrated the advantages and reliability of a dual grain structure at the component level.

Superplastic forming of Al-Li alloys for lightweight, low-cost structures

NASA Technical Reports Server (NTRS)

Hales, Stephen J.; Wagner, John A.

1991-01-01

Superplastic forming of advanced aluminum alloys is being evaluated as an approach for fabricating low-cost, light-weight, cryogenic propellant tanks. Built-up structure concepts (with inherent reduced scrap rate) are under investigation to offset the additional raw material expenses incurred by using aluminum lithium alloys. This approach to fabrication offers the potential for significant improvements in both structural efficiency and overall manufacturing costs. Superplasticity is the ability of specially processed material to sustain very large forming strains without failure at elevated temperatures under controlled deformation conditions. It was demonstrated that superplastic forming technology can be used to fabricate complex structural components in a single operation and increase structural efficiency by as much as 60 percent compared to conventional configurations in skin-stiffened structures. Details involved in the application of this technology to commercial grade superplastic aluminum lithium material are presented. Included are identification of optimum forming parameters, development of forming procedures, and assessment of final part quality in terms of cavitation volume and thickness variation.

Advancement of Compositional and Microstructural Design of Intermetallic γ-TiAl Based Alloys Determined by Atom Probe Tomography

PubMed Central

Klein, Thomas; Clemens, Helmut; Mayer, Svea

2016-01-01

Advanced intermetallic alloys based on the γ-TiAl phase have become widely regarded as most promising candidates to replace heavier Ni-base superalloys as materials for high-temperature structural components, due to their facilitating properties of high creep and oxidation resistance in combination with a low density. Particularly, recently developed alloying concepts based on a β-solidification pathway, such as the so-called TNM alloy, which are already incorporated in aircraft engines, have emerged offering the advantage of being processible using near-conventional methods and the option to attain balanced mechanical properties via subsequent heat-treatment. Development trends for the improvement of alloying concepts, especially dealing with issues regarding alloying element distribution, nano-scale phase characterization, phase stability, and phase formation mechanisms demand the utilization of high-resolution techniques, mainly due to the multi-phase nature of advanced TiAl alloys. Atom probe tomography (APT) offers unique possibilities of characterizing chemical compositions with a high spatial resolution and has, therefore, been widely used in recent years with the aim of understanding the materials constitution and appearing basic phenomena on the atomic scale and applying these findings to alloy development. This review, thus, aims at summarizing scientific works regarding the application of atom probe tomography towards the understanding and further development of intermetallic TiAl alloys. PMID:28773880

Advancement of Compositional and Microstructural Design of Intermetallic γ-TiAl Based Alloys Determined by Atom Probe Tomography.

PubMed

Klein, Thomas; Clemens, Helmut; Mayer, Svea

2016-09-06

Advanced intermetallic alloys based on the γ-TiAl phase have become widely regarded as most promising candidates to replace heavier Ni-base superalloys as materials for high-temperature structural components, due to their facilitating properties of high creep and oxidation resistance in combination with a low density. Particularly, recently developed alloying concepts based on a β-solidification pathway, such as the so-called TNM alloy, which are already incorporated in aircraft engines, have emerged offering the advantage of being processible using near-conventional methods and the option to attain balanced mechanical properties via subsequent heat-treatment. Development trends for the improvement of alloying concepts, especially dealing with issues regarding alloying element distribution, nano-scale phase characterization, phase stability, and phase formation mechanisms demand the utilization of high-resolution techniques, mainly due to the multi-phase nature of advanced TiAl alloys. Atom probe tomography (APT) offers unique possibilities of characterizing chemical compositions with a high spatial resolution and has, therefore, been widely used in recent years with the aim of understanding the materials constitution and appearing basic phenomena on the atomic scale and applying these findings to alloy development. This review, thus, aims at summarizing scientific works regarding the application of atom probe tomography towards the understanding and further development of intermetallic TiAl alloys.

NASA-UVA Light Aerospace Alloy and Structures Technology Program (LA2ST)

NASA Technical Reports Server (NTRS)

Gangloff, Richard P.

1994-01-01

The NASA-UVA Light Aerospace Alloy and Structures Technology (LA2ST) Program was initiated in 1986 and continues with a high level of activity. Projects are being conducted by graduate students and faculty advisors in the Department of Materials Science and Engineering, as well as in the Department of Civil Engineering and Applied Mechanics, at the University of Virginia. This work is funded by the NASA-Langley Research Center under Grant NAG-1-745. Here, we report on progress achieved between January 1 and June 30, 1994. These results were presented at the Fifth Annual NASA LA2ST Grant Review Meeting held at the Langley Research Center in July of 1994. The objective of the LA2ST Program is to conduct interdisciplinary graduate student research on the performance of next generation, lightweight aerospace alloys, composites, and thermal gradient structures in collaboration with NASA-Langley researchers. Specific technical objectives are presented for each research project. We generally aim to produce relevant data and basic understanding of material mechanical response, environmental/corrosion behavior, and microstructure; new monolithic and composite alloys; advanced processing methods; new solid and fluid mechanics analyses; measurement and modeling advances; and a pool of educated graduate students for aerospace technologies.

NASA-UVA light aerospace alloy and structures technology program (LA2ST)

NASA Technical Reports Server (NTRS)

Gangloff, Richard P.; Starke, Edger A., Jr.

1996-01-01

This progress report covers achievements made between January 1 and June 30, 1966 on the NASA-UVA Light Aerospace Alloy and Structures Technology (LA2ST) Program. The objective of the LA2ST Program is to conduct interdisciplinary graduate student research on the performance of next generation, light-weight aerospace alloys, composites and thermal gradient structures in collaboration with NASA-Langley researchers. Specific technical objectives are presented for each research project. . The accomplishments presented in this report are: (1) Mechanical and Environmental Degradation Mechanisms in Advanced Light Metals, (2) Aerospace Materials Science, and (3) Mechanics of Materials for Light Aerospace Structures. Collective accomplishments between January and June of 1996 include: 4 journal or proceedings publications, 1 NASA progress report, 4 presentations at national technical meetings, and 2 PhD dissertations published.

Neutron Absorbing Alloys

DOEpatents

Mizia, Ronald E.; Shaber, Eric L.; DuPont, John N.; Robino, Charles V.; Williams, David B.

2004-05-04

The present invention is drawn to new classes of advanced neutron absorbing structural materials for use in spent nuclear fuel applications requiring structural strength, weldability, and long term corrosion resistance. Particularly, an austenitic stainless steel alloy containing gadolinium and less than 5% of a ferrite content is disclosed. Additionally, a nickel-based alloy containing gadolinium and greater than 50% nickel is also disclosed.

NASA-UVA Light Aerospace Alloy and Structures Technology Program (LA2ST). Research on Materials for the High Speed Civil Transport

NASA Technical Reports Server (NTRS)

Gangloff, Richard P.; Starke, Edgar A., Jr.; Kelly, Robert G.; Scully, John R.; Stoner, Glenn E.; Wert, John A.

1997-01-01

Since 1986, the NASA-Langley Research Center has sponsored the NASA-UVa Light Alloy and Structures Technology (LA2ST) Program at the University of Virginia (UVa). The fundamental objective of the LA2ST program is to conduct interdisciplinary graduate student research on the performance of next generation, light-weight aerospace alloys, composites and thermal gradient structures. The LA2ST program has aimed to product relevant data and basic understanding of material mechanical response, environmental/corrosion behavior, and microstructure; new monolithic and composite alloys; advanced processing methods; measurement and modeling advances; and a pool of educated graduate students for aerospace technologies. The scope of the LA2ST Program is broad. Research areas include: (1) Mechanical and Environmental Degradation Mechanisms in Advanced Light Metals and Composites, (2) Aerospace Materials Science, (3) Mechanics of materials for Aerospace Structures, and (4) Thermal Gradient Structures. A substantial series of semi-annual progress reports issued since 1987 documents the technical objectives, experimental or analytical procedures, and detailed results of graduate student research in these topical areas.

Characterization of the Temperature Capabilities of Advanced Disk Alloy ME3

NASA Technical Reports Server (NTRS)

Gabb, Timothy P.; Telesman, Jack; Kantzos, Peter T.; OConnor, Kenneth

2002-01-01

The successful development of an advanced powder metallurgy disk alloy, ME3, was initiated in the NASA High Speed Research/Enabling Propulsion Materials (HSR/EPM) Compressor/Turbine Disk program in cooperation with General Electric Engine Company and Pratt & Whitney Aircraft Engines. This alloy was designed using statistical screening and optimization of composition and processing variables to have extended durability at 1200 F in large disks. Disks of this alloy were produced at the conclusion of the program using a realistic scaled-up disk shape and processing to enable demonstration of these properties. The objective of the Ultra-Efficient Engine Technologies disk program was to assess the mechanical properties of these ME3 disks as functions of temperature in order to estimate the maximum temperature capabilities of this advanced alloy. These disks were sectioned, machined into specimens, and extensively tested. Additional sub-scale disks and blanks were processed and selectively tested to explore the effects of several processing variations on mechanical properties. Results indicate the baseline ME3 alloy and process can produce 1300 to 1350 F temperature capabilities, dependent on detailed disk and engine design property requirements.

Alloy and structural optimization of a directionally solidified lamellar eutectic alloy

NASA Technical Reports Server (NTRS)

Sheffler, K. D.

1976-01-01

Mechanical property characterization tests of a directionally solidified Ni-20 percent Cb-2.5 percent Al-6 percent Cr cellular eutectic turbine blade alloy demonstrated excellent long time creep stability and indicated intermediate temperature transverse tensile ductility and shear strength to be somewhat low for turbine blade applications. Alloy and structural optimization significantly improves these off-axis properties with no loss of longitudinal creep strength or stability. The optimized alloy-structure combination is a carbon modified Ni-20.1 percent Cb-2.5 percent Al-6.0 percent Cr-0.06 percent C composition processed under conditions producing plane front solidification and a fully-lamellar microstructure. With current processing technology, this alloy exhibits a creep-rupture advantage of 39 C over the best available nickel base superalloy, directionally solidified MAR M200+ Hf. While improved by about 20 percent, shear strength of the optimized alloy remains well below typical superalloy values.

Welding of unique and advanced alloys for space and high-temperature applications: welding and weldability of iridium and platinum alloys

DOE PAGES

David, Stan A.; Miller, Roger G.; Feng, Zhili

2016-08-31

Advances have been made in developing alloys for space power systems for spacecraft that travel long distances to various planets. The spacecraft are powered by radioisotope thermoelectric generators (RTGs) and the fuel element in RTGs is plutonia. For safety and containment of the radioactive fuel element, the heat source is encapsulated in iridium or platinum alloys. Ir and Pt alloys are the alloys of choice for encapsulating radioisotope fuel pellets. Ir and Pt alloys were chosen because of their high-temperature properties and compatibility with the oxide fuel element and the graphite impact shells. This review addresses the alloy design andmore » welding and weldability of Ir and Pt alloys for use in RTGs.« less

Welding of unique and advanced alloys for space and high-temperature applications: welding and weldability of iridium and platinum alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

David, Stan A.; Miller, Roger G.; Feng, Zhili

Advances have been made in developing alloys for space power systems for spacecraft that travel long distances to various planets. The spacecraft are powered by radioisotope thermoelectric generators (RTGs) and the fuel element in RTGs is plutonia. For safety and containment of the radioactive fuel element, the heat source is encapsulated in iridium or platinum alloys. Ir and Pt alloys are the alloys of choice for encapsulating radioisotope fuel pellets. Ir and Pt alloys were chosen because of their high-temperature properties and compatibility with the oxide fuel element and the graphite impact shells. This review addresses the alloy design andmore » welding and weldability of Ir and Pt alloys for use in RTGs.« less

Development of Creep-Resistant, Alumina-Forming Ferrous Alloys for High-Temperature Structural Use

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yamamoto, Yukinori; Brady, Michael P.; Muralidharan, Govindarajan

This paper overviews recent advances in developing novel alloy design concepts of creep-resistant, alumina-forming Fe-base alloys, including both ferritic and austenitic steels, for high-temperature structural applications in fossil-fired power generation systems. Protective, external alumina-scales offer improved oxidation resistance compared to chromia-scales in steam-containing environments at elevated temperatures. Alloy design utilizes computational thermodynamic tools with compositional guidelines based on experimental results accumulated in the last decade, along with design and control of the second-phase precipitates to maximize high-temperature strengths. The alloys developed to date, including ferritic (Fe-Cr-Al-Nb-W base) and austenitic (Fe-Cr-Ni-Al-Nb base) alloys, successfully incorporated the balanced properties of steam/water vapor-oxidationmore » and/or ash-corrosion resistance and improved creep strength. Development of cast alumina-forming austenitic (AFA) stainless steel alloys is also in progress with successful improvement of higher temperature capability targeting up to ~1100°C. Current alloy design approach and developmental efforts with guidance of computational tools were found to be beneficial for further development of the new heat resistant steel alloys for various extreme environments.« less

Steam Oxidation Behavior of Advanced Steels and Ni-Based Alloys at 800 °C

NASA Astrophysics Data System (ADS)

Dudziak, T.; Boroń, L.; Deodeshmukh, V.; Sobczak, J.; Sobczak, N.; Witkowska, M.; Ratuszek, W.; Chruściel, K.

2017-03-01

This publication studies the steam oxidation behavior of advanced steels (309S, 310S and HR3C) and Ni-based alloys (Haynes® 230®, alloy 263, alloy 617 and Haynes® 282®) exposed at 800 °C for 2000 h under 1 bar pressure, in a pure water steam system. The results revealed that all exposed materials showed relatively low weight gain, with no spallation of the oxide scale within the 2000 h of exposure. XRD analysis showed that Ni-based alloys developed an oxide scale consisting of four main phases: Cr2O3 (alloy 617, Haynes® 282®, alloy 263 and Haynes® 230®), MnCr2O4 (alloy 617, Haynes® 282® and Haynes® 230®), NiCr2O4 (alloy 617) and TiO2 (alloy 263, Haynes® 282®). In contrast, advanced steels showed the development of Cr2O3, MnCr2O4, Mn7SiO12, FeMn(SiO4) and SiO2 phases. The steel with the highest Cr content showed the formation of Fe3O4 and the thickest oxide scale.

Structure of dental gallium alloys.

PubMed

Herø, H; Simensen, C J; Jørgensen, R B

1996-07-01

The interest in gallium alloys as a replacement for amalgam has increased in recent years due to the risk of environmental pollution from amalgam. Alloy powders with compositions close to those for alloys of amalgam are mixed with a liquid gallium alloy. The mix is condensed into a prepared cavity in much the same way as for amalgam. The aim of the present work was to study the structure of: (1) two commercial alloy powders containing mainly silver, tin and copper, and (2) the phases formed by mixing these powders with a liquid alloy of gallium, indium and tin. One of the alloy powders contained 9 wt% palladium. Cross-sections of cylindrical specimens made by these gallium mixes were investigated by scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction. Discrete grains of the following phases were found to be present in both gallium alloys: hexagonal Ag2Ga, tetragonal Cu(Pd)Ga2, cubic Ag9In4 and tetragonal beta-Sn. Indications of hexagonal or orthorhombic Ag2Sn were found in the remaining, unreacted alloy particles. In the palladium-containing alloy the X-ray reflections indicate a minor fraction of cubic Cu9Ga4 in addition to the Cu(Pd)Ga2 phase. Particles of beta-Sn are probably precipitated because Sn-Ga phases cannot be formed according to the binary phase diagram.

Advanced smart tungsten alloys for a future fusion power plant

NASA Astrophysics Data System (ADS)

Litnovsky, A.; Wegener, T.; Klein, F.; Linsmeier, Ch; Rasinski, M.; Kreter, A.; Tan, X.; Schmitz, J.; Mao, Y.; Coenen, J. W.; Bram, M.; Gonzalez-Julian, J.

2017-06-01

The severe particle, radiation and neutron environment in a future fusion power plant requires the development of advanced plasma-facing materials. At the same time, the highest level of safety needs to be ensured. The so-called loss-of-coolant accident combined with air ingress in the vacuum vessel represents a severe safety challenge. In the absence of a coolant the temperature of the tungsten first wall may reach 1200 °C. At such a temperature, the neutron-activated radioactive tungsten forms volatile oxide which can be mobilized into atmosphere. Smart tungsten alloys are being developed to address this safety issue. Smart alloys should combine an acceptable plasma performance with the suppressed oxidation during an accident. New thin film tungsten-chromium-yttrium smart alloys feature an impressive 105 fold suppression of oxidation compared to that of pure tungsten at temperatures of up to 1000 °C. Oxidation behavior at temperatures up to 1200 °C, and reactivity of alloys in humid atmosphere along with a manufacturing of reactor-relevant bulk samples, impose an additional challenge in smart alloy development. First exposures of smart alloys in steady-state deuterium plasma were made. Smart tungsten-chroimium-titanium alloys demonstrated a sputtering resistance which is similar to that of pure tungsten. Expected preferential sputtering of alloying elements by plasma ions was confirmed experimentally. The subsequent isothermal oxidation of exposed samples did not reveal any influence of plasma exposure on the passivation of alloys.

FAA/NASA International Symposium on Advanced Structural Integrity Methods for Airframe Durability and Damage Tolerance

NASA Technical Reports Server (NTRS)

Harris, Charles E. (Editor)

1994-01-01

International technical experts in durability and damage tolerance of metallic airframe structures were assembled to present and discuss recent research findings and the development of advanced design and analysis methods, structural concepts, and advanced materials. The symposium focused on the dissemination of new knowledge and the peer-review of progress on the development of advanced methodologies. Papers were presented on: structural concepts for enhanced durability, damage tolerance, and maintainability; new metallic alloys and processing technology; fatigue crack initiation and small crack effects; fatigue crack growth models; fracture mechanics failure, criteria for ductile materials; structural mechanics methodology for residual strength and life prediction; development of flight load spectra for design and testing; and advanced approaches to resist corrosion and environmentally assisted fatigue.

Structure-property relationship of cast Ti-Nb alloys.

PubMed

Lee, C M; Ju, C P; Chern Lin, J H

2002-04-01

The present work is a study of the microstructure, mechanical properties and corrosion behaviour of a series of binary Ti-Nb alloys with Nb contents up to 35 wt%, with emphasis placed on the structure-property relationship of the alloys. The results indicate that crystal structure and morphology of the Ti-Nb alloys are sensitive to the Nb content. The cast c.p. Ti has a hexagonal alpha phase with a lath type morphology. The alloys containing 15 wt% or less Nb are dominated by a hexagonal alpha' phase with an acicular, martensitic structure. When containing 17.5-25 wt% Nb, the alloys are primarily comprised of an orthorhombic alpha" phase. With 27.5 wt% Nb, metastable beta phase starts to be retained. With Nb contents higher than 30 wt%, the equi-axed beta phase is almost entirely retained. Small amounts of omega phase are detected in alloys containing 27.5 and 30 wt% Nb. Among all present alloys, Ti-10Nb and Ti-27.5Nb exhibit the highest strengths, while the alpha"-dominated (17.5 and 20Nb) and beta-dominated (> 30Nb) alloys have the lowest moduli. All Ti-Nb alloys show excellent corrosion resistance in Hank's solution at 37 degrees C. From the present data, the microhardness, bending strength and modulus of the various phases in Ti-Nb alloys are compared and tentatively summarized as follows: Microhardness: omega > alpha' > alpha" > beta > alpha (c.p. Ti) Bending strength: omega > alpha' > alpha" > beta > alpha (c.p. Ti) Bending modulus: omega > alpha (c.p. Ti) > alpha' > alpha" > beta

Cryogenic Fracture Toughness Evaluation of an Investment Cast Al-Be Alloy for Structural Applications

NASA Technical Reports Server (NTRS)

Gamwell, W. R.; McGill, P. B.

2006-01-01

Aluminum-Beryllium metal matrix composite materials are useful due to their desirable performance characteristics for aerospace applications. Desirable characteristics of this material includes light-weight, dimensional stability, stiffness, good vibration damping characteristics, low coefficient of thermal expansion, and workability, This material is 3.5 times stiffer and 22% lighter than conventional aluminum alloys. electro-optical systems, advanced sensor and guidance components for flight and satellite systems, components for light-weight high-performance aircraft engines, and structural components for helicopters. Aluminum-beryllium materials are now available in the form of near net shape investment castings. In this materials properties characterization study, the cryogenic tensile and fracture properties of an investment casting alloy, Beralcast 363, were determined. Tensile testing was performed at 21 C (70 F), -73.3 C (-100 F), -195.5 C (-320 F) and -252.8 C (-423 F), and fracture (K(sub lc) and da/dN) testing was performed at -73.3 C (-100 F), -195.5 C (-320 F) and -252.8 C (-423 F). Their use is attractive for weight critical structural applications such as advanced

Nickel aluminide alloy suitable for structural applications

DOEpatents

Liu, Chain T.

1998-01-01

Alloys for use in structural applications based upon NiAl to which are added selected elements to enhance room temperature ductility and high temperature strength. Specifically, small additions of molybdenum produce a beneficial alloy, while further additions of boron, carbon, iron, niobium, tantalum, zirconium and hafnium further improve performance of alloys at both room temperature and high temperatures. A preferred alloy system composition is Ni--(49.1.+-.0.8%)Al--(1.0.+-.0.8%)Mo--(0.7.+-.0.5%)Nb/Ta/Zr/Hf--(nearly zero to 0.03%)B/C, where the % is at. % in each of the concentrations. All alloys demonstrated good oxidation resistance at the elevated temperatures. The alloys can be fabricated into components using conventional techniques.

Electron beam welding of aircraft structures. [joining of titanium alloy wing structures on F-14 aircraft

NASA Technical Reports Server (NTRS)

Witt, R. H.

1972-01-01

Requirements for advanced aircraft have led to more extensive use of titanium alloys and the resultant search for joining processes which can produce lightweight, high strength airframe structures efficiently. As a result, electron beam welding has been investigated. The following F-14A components are now being EB welded in production and are mainly annealed Ti-6Al-4V except for the upper wing cover which is annealed Ti-6Al-6V-2Sn: F-14A wing center section box, and F-14A lower and upper wing covers joined to wing pivot fitting assemblies. Criteria for selection of welding processes, the EB welding facility, development work on EB welding titanium alloys, and F-14A production and sliding seal electron beam welding are reported.

Advanced Cast Aluminum Alloys

DTIC Science & Technology

2009-02-01

This production route has demonstrated that aluminum alloys with yield strengths in excess of 690 MPa with good elongation (reportedly 8%) are...series of aluminum alloys have poor-to-fair general corrosion resistance and poor-to-good stress corrosion cracking resistance. Wrought 2519...aluminum alloy has good strength, good ballistic performance, good stress corrosion cracking resistance but only fair general corrosion resistance

Nickel aluminide alloy suitable for structural applications

DOEpatents

Liu, C.T.

1998-03-10

Alloys are disclosed for use in structural applications based upon NiAl to which are added selected elements to enhance room temperature ductility and high temperature strength. Specifically, small additions of molybdenum produce a beneficial alloy, while further additions of boron, carbon, iron, niobium, tantalum, zirconium and hafnium further improve performance of alloys at both room temperature and high temperatures. A preferred alloy system composition is Ni--(49.1{+-}0.8%)Al--(1.0{+-}0.8%)Mo--(0.7 + 0.5%)Nb/Ta/Zr/Hf--(nearly zero to 0.03%)B/C, where the % is at. % in each of the concentrations. All alloys demonstrated good oxidation resistance at the elevated temperatures. The alloys can be fabricated into components using conventional techniques. 4 figs.

Computing elastic anisotropy to discover gum-metal-like structural alloys

NASA Astrophysics Data System (ADS)

Winter, I. S.; de Jong, M.; Asta, M.; Chrzan, D. C.

2017-08-01

The computer aided discovery of structural alloys is a burgeoning but still challenging area of research. A primary challenge in the field is to identify computable screening parameters that embody key structural alloy properties. Here, an elastic anisotropy parameter that captures a material's susceptibility to solute solution strengthening is identified. The parameter has many applications in the discovery and optimization of structural materials. As a first example, the parameter is used to identify alloys that might display the super elasticity, super strength, and high ductility of the class of TiNb alloys known as gum metals. In addition, it is noted that the parameter can be used to screen candidate alloys for shape memory response, and potentially aid in the optimization of the mechanical properties of high-entropy alloys.

Structural transformations of heat treated Co-less high entropy alloys

NASA Astrophysics Data System (ADS)

Mitrica, D.; Tudor, A.; Rinaldi, A.; Soare, V.; Predescu, C.; Berbecaru, A.; Stoiciu, F.; Badilita, V.

2018-03-01

Co is considered to be one of the main ingredients in superalloys. Co is considered a critical element and its substitution is difficult due to its unique ability to form high temperature stable structures with high mechanical and corrosion/oxidation resistance. High entropy alloys (HEA) represent a relatively new concept in material design. HEA are characterised by a high number of alloying elements, in unusually high proportion. Due to their specific particularities, high entropy alloys tend to form predominant solid solution structures that develop potentially high chemical, physical and mechanical properties. Present paper is studying Co-less high entropy alloys with high potential in severe environment applications. The high entropy alloys based on Al-Cr-Fe-Mn-Ni system were prepared by induction melting and casting under protective atmosphere. The as-cast specimens were heat treated at various temperatures to determine the structure and property behaviour. Samples taken before and after heat treatment were investigated for chemical, physical, structural and mechanical characteristics. Sigma phase composition and heat treatment parameters had major influence over the resulted alloy structure and properties.

Development of hydrogen resistant structural alloy NASA-23

NASA Technical Reports Server (NTRS)

Bhat, B. N.; Mcpherson, W. B.; Kuruvilla, A. K.; Chen, P. S.; Panda, B.

1993-01-01

Hydrogen-resistant alloy NASA-23 was developed specifically as a structural alloy for application in liquid propulsion systems that use hydrogen fuel. NASA-23 was designed to be similar to Alloy 718 in strength, ductility, and corrosion resistance, but with superior resistance to hydrogen environment embrittlement. The alloy is readily processed; it can be both hot and cold worked and is castable and weldable. A material property data base is being generated for both cast and wrought NASA-23. This paper will present the status of alloy development and discuss potential applications in propulsion systems.

Mechanistic Studies Of Combustion And Structure Formation During Combustion Synthesis Of Advanced Materials: Phase Separation Mechanism For Bio-Alloys

NASA Technical Reports Server (NTRS)

Varma, A.; Lau, C.; Mukasyan, A.

2003-01-01

Among all implant materials, Co-Cr-Mo alloys demonstrate perhaps the most useful balance of resistance to corrosion, fatigue and wear, along with strength and biocompatibility [1]. Currently, these widely used alloys are produced by conventional furnace technology. Owing to high melting points of the main alloy elements (e.g. Tm.p.(Co) 1768 K), high-temperature furnaces and long process times (several hours) are required. Therefore, attempts to develop more efficient and flexible methods for production of such alloys with superior properties are of great interest. The synthesis of materials using combustion phenomena is an advanced approach in powder metallurgy [2]. The process is characterized by unique conditions involving extremely fast heating rates (up to 10(exp 6 K/s), high temperatures (up to 3500 K), and short reaction times (on the order of seconds). As a result, combustion synthesis (CS) offers several attractive advantages over conventional metallurgical processing and alloy development technologies. The foremost is that solely the heat of chemical reaction (instead of an external source) supplies the energy for the synthesis. Also, simple equipment, rather than energy-intensive high-temperature furnaces, is sufficient. This work was devoted to experiments on CS of Co-based alloys by utilizing thermite (metal oxide-reducing metal) reactions, where phase separation subsequently produces materials with tailored compositions and properties. Owing to high reaction exothermicity, the CS process results in a significant increase of temperature (up to 3000 C), which is higher than melting points of all products. Since the products differ in density, phase separation may be a gravitydriven process: the heavy (metallic phase) settles while the light (slag) phase floats. The goal was to determine if buoyancy is indeed the major mechanism that controls phase segregation.

Highly mismatched GaN1-x Sb x alloys: synthesis, structure and electronic properties

NASA Astrophysics Data System (ADS)

Yu, K. M.; Sarney, W. L.; Novikov, S. V.; Segercrantz, N.; Ting, M.; Shaw, M.; Svensson, S. P.; Martin, R. W.; Walukiewicz, W.; Foxon, C. T.

2016-08-01

Highly mismatched alloys (HMAs) is a class of semiconductor alloys whose constituents are distinctly different in terms of size, ionicity and/or electronegativity. Electronic properties of the alloys deviate significantly from an interpolation scheme based on small deviations from the virtual crystal approximation. Most of the HMAs were only studied in a dilute composition limit. Recent advances in understanding of the semiconductor synthesis processes allowed growth of thin films of HMAs under non-equilibrium conditions. Thus reducing the growth temperature allowed synthesis of group III-N-V HMAs over almost the entire composition range. This paper focuses on the GaN x Sb1-x HMA which has been suggested as a potential material for solar water dissociation devices. Here we review our recent work on the synthesis, structural and optical characterization of GaN1-x Sb x HMA. Theoretical modeling studies on its electronic structure based on the band anticrossing (BAC) model are also reviewed. In particular we discuss the effects of growth temperature, Ga flux and Sb flux on the incorporation of Sb, film microstructure and optical properties of the alloys. Results obtained from two separate MBE growths are directly compared. Our work demonstrates that a large range of direct bandgap energies from 3.4 eV to below 1.0 eV can be achieved for this alloy grown at low temperature. We show that the electronic band structure of GaN1-x Sb x HMA over the entire composition range is well described by a modified BAC model which includes the dependence of the host matrix band edges as well as the BAC model coupling parameters on composition. We emphasize that the modified BAC model of the electronic band structure developed for the full composition of GaN x Sb1-x is general and is applicable to any HMA.

Advances in joining newer structural materials; Proceedings of the International Conference, Montreal, Canada, July 23-25, 1990

NASA Astrophysics Data System (ADS)

The present conference on advances in joining novel structural materials encompasses such material types as ceramics, plastics and composites, and new metallic materials. Specific issues addressed include the use of conductor electric explosion to join ceramics, the effects of brazing temperature on joint properties of SiC-fiber-reinforced Al-alloy-matrix composites, the in situ structure control of composite materials, and the weldability of polymeric materials that are heterogeneous as to chemical nature from the standpoint of morphology. Also addressed are the joining of the Al-Li alloy 8090, diffusion bonding of a creep-resistant Fe-ODS alloy, the adhesive bonding of zinc-coated steel sheets, welds in thermoplastic composite materials, and hot-melt joints for carbon-fiber-reinforced composites.

Effective band structure of random III-V alloys

NASA Astrophysics Data System (ADS)

Popescu, Voicu; Zunger, Alex

2010-03-01

Random substitutional alloys have no long range order (LRO) or translational symmetry so rigorously speaking they have no E(k) band structure or manifestations thereof. Yet, many experiments on alloys are interpreted using the language of band theory, e.g. inferring Van Hove singularities, band dispersion and effective masses. Many standard alloy theories (VCA- or CPA-based) have the LRO imposed on the alloy Hamiltonian, assuming only on-site disorder, so they can not be used to judge the extent of LRO that really exists. We adopt the opposite way, by using large (thousand atom) randomly generated supercells in which chemically identical alloy atoms are allowed to have different local environments (a polymorphous representation). This then drives site-dependent atomic relaxation as well as potential fluctuations. The eigenstates from such supercells are then mapped onto the Brillouin zone (BZ) of the primitive cell, producing effective band dispersion. Results for (In,Ga)X show band-like behaviour only near the centre and faces of the BZ but rapidly lose such characteristics away from γ or for higher bands. We further analyse the effects of stoichiometry variation, internal relaxation, and short-range order on the alloy band structure.

Electron Beam Freeform Fabrication of Titanium Alloy Gradient Structures

NASA Technical Reports Server (NTRS)

Brice, Craig A.; Newman, John A.; Bird, Richard Keith; Shenoy, Ravi N.; Baughman, James M.; Gupta, Vipul K.

2014-01-01

Historically, the structural optimization of aerospace components has been done through geometric methods. A monolithic material is chosen based on the best compromise between the competing design limiting criteria. Then the structure is geometrically optimized to give the best overall performance using the single material chosen. Functionally graded materials offer the potential to further improve structural efficiency by allowing the material composition and/or microstructural features to spatially vary within a single structure. Thus, local properties could be tailored to the local design limiting criteria. Additive manufacturing techniques enable the fabrication of such graded materials and structures. This paper presents the results of a graded material study using two titanium alloys processed using electron beam freeform fabrication, an additive manufacturing process. The results show that the two alloys uniformly mix at various ratios and the resultant static tensile properties of the mixed alloys behave according to rule-of-mixtures. Additionally, the crack growth behavior across an abrupt change from one alloy to the other shows no discontinuity and the crack smoothly transitions from one crack growth regime into another.

Aeronautical Industry Requirements for Titanium Alloys

NASA Astrophysics Data System (ADS)

Bran, D. T.; Elefterie, C. F.; Ghiban, B.

2017-06-01

The project presents the requirements imposed for aviation components made from Titanium based alloys. A significant portion of the aircraft pylons are manufactured from Titanium alloys. Strength, weight, and reliability are the primary factors to consider in aircraft structures. These factors determine the requirements to be met by any material used to construct or repair the aircraft. Many forces and structural stresses act on an aircraft when it is flying and when it is static and this thesis describes environmental factors, conditions of external aggression, mechanical characteristics and loadings that must be satisfied simultaneously by a Ti-based alloy, compared to other classes of aviation alloys (as egg. Inconel super alloys, Aluminum alloys).For this alloy class, the requirements are regarding strength to weight ratio, reliability, corrosion resistance, thermal expansion and so on. These characteristics additionally continue to provide new opportunities for advanced manufacturing methods.

Advanced oxide dispersion strengthened sheet alloys for improved combustor durability

NASA Technical Reports Server (NTRS)

Henricks, R. J.

1981-01-01

Burner design modifications that will take advantage of the improved creep and cyclic oxidation resistance of oxide dispersion strengthened (ODS) alloys while accommodating the reduced fatigue properties of these materials were evaluated based on preliminary analysis and life predictions, on construction and repair feasibility, and on maintenance and direct operating costs. Two designs - the film cooled, segmented louver and the transpiration cooled, segmented twin Wall - were selected for low cycle fatigue (LCF) component testing. Detailed thermal and structural analysis of these designs established the strain range and temprature at critical locations resulting in predicted lives of 10,000 cycles for MA 956 alloy. The ODs alloys, MA 956 and HDA 8077, demonstrated a 167 C (300 F) temperature advantage over Hastelloy X alloy in creep strength and oxidation resistance. The MA 956 alloy was selected for mechanical property and component test evaluations. The MA 956 alloy was superior to Hastelloy X in LCF component testing of the film cooled, segmented louver design.

Advanced composite alloys for constructional parts of robots

NASA Astrophysics Data System (ADS)

Issin, D. K.; Zholdubayeva, Zh D.; Neshina, Y. G.; Alkina, A. D.; Khuangan, N.; Rahimova, G. M.

2018-05-01

In recent years all over the world special attention has been paid to the development and implementation of nanostructured materials possessing unique properties and opening fascinating prospects for the development of technical progress in various fields of human activities. A special place can be given to the development of service robots, the market of which is actively developing. There is problem associated mainly with the lack of heat-strengthened alloys which consists in low thermal stability of the alloy properties under the conditions of elevated variable temperatures and loads. The article presents studies to assess the effect of composition, the amounts of refractory nanoscale particles and methods for their introduction into the melt on the structure and properties in nanostructured composite aluminum alloys. The powders of metals, alloys, as well as silicon carbide and aluminum oxide were used to produce the nanostructured powder composite materials. As a result of the research, NPCM compositions containing micro-size particles of transition metals that are carriers of nanosized reinforcing particles and initiators of the formation of an intermetallide of endogenous origin in a melt.

Structural studies of liquid Co–Sn alloys

PubMed Central

Yakymovych, A.; Shtablavyi, I.; Mudry, S.

2014-01-01

An analysis of the structure features of liquid Co–Sn alloys has been performed by means of X-ray diffraction method, viscosity coefficient analysis and computer simulation method. The X-ray diffraction investigations were carried out over a wide concentration range at the temperature 1473 K. It was found that the structure of these alloys can be described in the frame of independent X-ray scattering model. The viscosity coefficient was calculated by an excess entropy scaling and compared with experimental data. PMID:25328282

Vacuum Plasma Spray of CuCrNb Alloy for Advanced Liquid - Fuel Combustion Chambers

NASA Technical Reports Server (NTRS)

Zimmerman, Frank

2000-01-01

The copper-8 atomic percent chromium-4 atomic percent niobium (CuCrNb) alloy was developed by Glenn Research Center (formally Lewis Research Center) as an improved alloy for combustion chamber liners. In comparison to NARloy-Z, the baseline (as in Space Shuttle Main Engine) alloy for such liners, CuCrNb demonstrates mechanical and thermophysical properties equivalent to NARloy-Z, but at temperatures 100 C to 150 C (180 F to 270 F) higher. Anticipated materials related benefits include decreasing the thrust cell liner weight 5% to 20%, increasing the service life at least two fold over current combustion chamber design, and increasing the safety margins available to designers. By adding an oxidation and thermal barrier coating to the liner, the combustion chamber can operate at even higher temperatures. For all these benefits, however, this alloy cannot be formed using conventional casting and forging methods because of the levels of chromium and niobium, which exceed their solubility limit in copper. Until recently, the only forming process that maintains the required microstructure of CrNb intermetallics is powder metallurgy formation of a billet from powder stock, followed by extrusion. This severely limits its usefulness in structural applications, particularly the complex shapes required for combustion chamber liners. Vacuum plasma spray (VPS) has been demonstrated as a method to form structural articles including small combustion chambers from the CuCrNb alloy. In addition, an oxidation and thermal barrier layer can be formed integrally on the hot wall of the liner that improve performance and extend service life. This paper discusses the metallurgy and thermomechanical properties of VPS formed CuCrNb versus the baseline powder metallurgy process, and the manufacturing of small combustion chamber liners at Marshall Space Flight Center using the VPS process. The benefits to advanced propulsion initiatives of using VPS to fabricate combustion chamber liners

Structure-Property Relationships in Aluminum-Copper alloys using Transmission X-Ray Microscopy (TXM) and Micromechanical Testing

NASA Astrophysics Data System (ADS)

Kaira, Chandrashekara Shashank

Aluminum alloys are ubiquitously used in almost all structural applications due to their high strength-to-weight ratio. Their superior mechanical performance can be attributed to complex dispersions of nanoscale intermetallic particles that precipitate out from the alloy's solid solution and offer resistance to deformation. Although they have been extensively investigated in the last century, the traditional approaches employed in the past haven't rendered an authoritative microstructural understanding in such materials. The effect of the precipitates' inherent complex morphology and their three-dimensional (3D) spatial distribution on evolution and deformation behavior have often been precluded. In this study, for the first time, synchrotron-based hard X-ray nano-tomography has been implemented in Al-Cu alloys to measure growth kinetics of different nanoscale phases in 3D and reveal mechanistic insights behind some of the observed novel phase transformation reactions occurring at high temperatures. The experimental results were reconciled with coarsening models from the LSW theory to an unprecedented extent, thereby establishing a new paradigm for thermodynamic analysis of precipitate assemblies. By using a unique correlative approach, a non-destructive means of estimating precipitation-strengthening in such alloys has been introduced. Limitations of using existing mechanical strengthening models in such alloys have been discussed and a means to quantify individual contributions from different strengthening mechanisms has been established. The current rapid pace of technological progress necessitates the demand for more resilient and high-performance alloys. To achieve this, a thorough understanding of the relationships between material properties and its structure is indispensable. To establish this correlation and achieve desired properties from structural alloys, microstructural response to mechanical stimuli needs to be understood in three-dimensions (3D). To

Fatigue and Creep-Fatigue Deformation of an Ultra-Fine Precipitate Strengthened Advanced Austenitic Alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

M.C. Carroll; L.J. Carroll

An advanced austenitic alloy, HT-UPS (high-temperature ultrafine-precipitation-strengthened), has been identified as an ideal candidate material for the structural components of fast reactors and energy-conversion systems. HT-UPS alloys demonstrate improved creep resistance relative to 316 stainless steel (SS) through additions of Ti and Nb, which precipitate to form a widespread dispersion of stable nanoscale metallic carbide (MC) particles in the austenitic matrix. The low-cycle fatigue and creep-fatigue behavior of an HT-UPS alloy have been investigated at 650 °C and a 1.0% total strain, with an R-ratio of -1 and hold times at peak tensile strain as long as 150 min. Themore » cyclic deformation response of HT-UPS is directly compared to that of standard 316 SS. The measured values for total cycles to failure are similar, despite differences in peak stress profiles and in qualitative observations of the deformed microstructures. Crack propagation is primarily transgranular in fatigue and creep-fatigue of both alloys at the investigated conditions. Internal grain boundary damage in the form of fine cracks resulting from the tensile hold is present for hold times of 60 min and longer, and substantially more internal cracks are quantifiable in 316 SS than in HT-UPS. The dislocation substructures observed in the deformed material differ significantly; an equiaxed cellular structure is observed in 316 SS, whereas in HT-UPS the microstructure takes the form of widespread and relatively homogenous tangles of dislocations pinned by the nanoscale MC precipitates. The significant effect of the fine distribution of precipitates on observed fatigue and creep-fatigue response is described in three distinct behavioral regions as it evolves with continued cycling.« less

Evolution of Nano-structured Quasicrystals from Amorphous alloys

NASA Astrophysics Data System (ADS)

Xing, L. Q.; Kelton, K. F.

2002-03-01

Ta shows a significant effect on the precipitation of quasicrystals in (Zr_1-xTa_x)_64Cu_18Ni_8Al_10 amorphous alloys. The amorphous alloy made without Ta forms precipitates of tetragonal Zr_2Cu primary phases upon annealing. The addition of a small amount of Ta ( ~ 3 at%) to the alloy initiates the precipitation of primary icosahedral quasicrystal phases. Moreover, as the Ta concentration increases, the size of the precipitates decreases dramatically. To study the effect of Ta in this alloy system and to understand the mechanism for the precipitation of nano-structured quasicrystals, we have investigated the crystallization characteristics of the alloys made with different Ta concentration using DSC, checked the structures of the annealed samples with TEM and X-ray diffraction, and analyzed the kinetics of the crystallization processes. The kinetic parameter and the measured crystal size distribution will be compared with theoretical predictions from conventional nucleation and growth model and from a new model for nucleation that couples the long-range diffusion flux with the interfacial attachment processes.

Structural phase transition, electronic structure and optical properties of half Heusler alloys LiBeZ (Z = As, Sb)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Amudhavalli, A.; Rajeswarapalanichamy, R., E-mail: rajeswarapalanichamy@gmail.com

2016-05-23

Ab initio calculations are performed to investigate the structural stability, electronic structure, mechanical properties and optical properties of half Heusler alloys (LiBeAs and LiBeSb) for three different phases of zinc blende crystal structure. Among the considered phases, α- phase is found to be the most stable phase for these alloys at normal pressure. A pressure induced structural phase transition from α-phase to β- phase is observed for LiBeAs. The electronic structure reveals that these alloys are semiconductors. The optical properties confirm that these alloys are semiconductor in nature.

FAA/NASA International Symposium on Advanced Structural Integrity Methods for Airframe Durability and Damage Tolerance, part 2

NASA Technical Reports Server (NTRS)

Harris, Charles E. (Editor)

1994-01-01

The international technical experts in the areas of durability and damage tolerance of metallic airframe structures were assembled to present and discuss recent research findings and the development of advanced design and analysis methods, structural concepts, and advanced materials. The principal focus of the symposium was on the dissemination of new knowledge and the peer-review of progress on the development of advanced methodologies. Papers were presented on the following topics: structural concepts for enhanced durability, damage tolerance, and maintainability; new metallic alloys and processing technology; fatigue crack initiation and small crack effects; fatigue crack growth models; fracture mechanics failure criteria for ductile materials; structural mechanics methodology for residual strength and life prediction; development of flight load spectra for design and testing; and corrosion resistance.

Rare-earth metals in nickel aluminide-based alloys: III. Structure and properties of multicomponent Ni3Al-based alloys

NASA Astrophysics Data System (ADS)

Bazyleva, O. A.; Povarova, K. B.; Kazanskaya, N. K.; Drozdov, A. A.

2009-04-01

The possibility of increasing the life of heterophase cast light Ni3Al-based superalloys at temperatures higher than 0.8 T m of Ni3Al is studied when their directional structure is additionally stabilized by nanoprecipitates, which form upon additional alloying of these alloys by refractory and active metals, and using special methods for preparing and melting of an alloy charge. The effect of the method of introducing the main components and refractory reaction-active and surface-active alloying elements into Ni3Al-based cast superalloys, which are thermally stable natural composite materials of the eutectic type, on the structure-phase state and the life of these alloys is studied. When these alloys are melted, it is necessary to perform a set of measures to form particles of refractory oxide cores covered with the β-NiAl phase and, then, γ'prim-Ni3Al phase precipitates during solidification. The latter phase forms the outer shell of grain nuclei, which provides high thermal stability and hot strength of an intermetallic compound-based alloy. As a result, a modified structure that is stabilized by the nanoprecipitates of nickel and aluminum lanthanides and the nanoprecipitates of phases containing refractory metals is formed. This structure enhances the life of the alloy at 1000 °C by a factor of 1.8-2.5.

The structural phases and vibrational properties of Mo1-xWxTe2 alloys

NASA Astrophysics Data System (ADS)

Oliver, Sean M.; Beams, Ryan; Krylyuk, Sergiy; Kalish, Irina; Singh, Arunima K.; Bruma, Alina; Tavazza, Francesca; Joshi, Jaydeep; Stone, Iris R.; Stranick, Stephan J.; Davydov, Albert V.; Vora, Patrick M.

2017-12-01

The structural polymorphism in transition metal dichalcogenides (TMDs) provides exciting opportunities for developing advanced electronics. For example, MoTe2 crystallizes in the 2H semiconducting phase at ambient temperature and pressure, but transitions into the 1T‧ semimetallic phase at high temperatures. Alloying MoTe2 with WTe2 reduces the energy barrier between these two phases, while also allowing access to the T d Weyl semimetal phase. The \\text{M}{{\\text{o}}1-\\text{x}} WxTe2 alloy system is therefore promising for developing phase change memory technology. However, achieving this goal necessitates a detailed understanding of the phase composition in the MoTe2-WTe2 system. We combine polarization-resolved Raman spectroscopy with x-ray diffraction (XRD) and scanning transmission electron microscopy (STEM) to study bulk \\text{M}{{\\text{o}}1-\\text{x}} WxTe2 alloys over the full compositional range x from 0 to 1. We identify Raman and XRD signatures characteristic of the 2H, 1T‧, and T d structural phases that agree with density-functional theory (DFT) calculations, and use them to identify phase fields in the MoTe2-WTe2 system, including single-phase 2H, 1T‧, and T d regions, as well as a two-phase 1T‧  +  T d region. Disorder arising from compositional fluctuations in \\text{M}{{\\text{o}}1-\\text{x}} WxTe2 alloys breaks inversion and translational symmetry, leading to the activation of an infrared 1T‧-MoTe2 mode and the enhancement of a double-resonance Raman process in \\text{2H-M}{{\\text{o}}1-\\text{x}} WxTe2 alloys. Compositional fluctuations limit the phonon correlation length, which we estimate by fitting the observed asymmetric Raman lineshapes with a phonon confinement model. These observations reveal the important role of disorder in \\text{M}{{\\text{o}}1-\\text{x}} WxTe2 alloys, clarify the structural phase boundaries, and provide a foundation for future explorations of phase transitions and electronic phenomena in this

Requirements of titanium alloys for aeronautical industry

NASA Astrophysics Data System (ADS)

Ghiban, Brânduşa; Bran, Dragoş-Teodor; Elefterie, Cornelia Florina

2018-02-01

The project presents the requirements imposed for aeronatical components made from Titanium based alloys. Asignificant portion of the aircraft pylons are manufactured from Titanium alloys. Strength, weight, and reliability are the primary factors to consider in aircraft structures. These factors determine the requirements to be met by any material used to construct or repair the aircraft. Many forces and structural stresses act on an aircraft when it is flying and when it is static and this thesis describes environmental factors, conditions of external aggression, mechanical characteristics and loadings that must be satisfied simultaneously by a Ti-based alloy, compared to other classes of aviation alloys (as egg. Inconel super alloys, Aluminum alloys). For this alloy class, the requirements are regarding strength to weight ratio, reliability, corrosion resistance, thermal expansion and so on. These characteristics additionally continue to provide new opportunities for advanced manufacturing methods.

Dual-phase Cr-Ta alloys for structural applications

DOEpatents

Liu, Chain T.; Brady, Michael P.; Zhu, Jiahong; Tortorelli, Peter F.

2001-01-01

Dual phase alloys of chromium containing 2 to 11 atomic percent tantalum with minor amounts of Mo, Cr, Ti, Y, La, Cr, Si and Ge are disclosed. These alloys contain two phases including Laves phase and Cr-rich solid solution in either eutectic structures or dispersed Laves phase particles in the Cr-rich solid solution matrix. The alloys have superior mechanical properties at high temperature and good oxidation resistance when heated to above 1000.degree. C. in air.

Atomic scale modelling of hexagonal structured metallic fission product alloys

PubMed Central

Middleburgh, S. C.; King, D. M.; Lumpkin, G. R.

2015-01-01

Noble metal particles in the Mo-Pd-Rh-Ru-Tc system have been simulated on the atomic scale using density functional theory techniques for the first time. The composition and behaviour of the epsilon phases are consistent with high-entropy alloys (or multi-principal component alloys)—making the epsilon phase the only hexagonally close packed high-entropy alloy currently described. Configurational entropy effects were considered to predict the stability of the alloys with increasing temperatures. The variation of Mo content was modelled to understand the change in alloy structure and behaviour with fuel burnup (Mo molar content decreases in these alloys as burnup increases). The predicted structures compare extremely well with experimentally ascertained values. Vacancy formation energies and the behaviour of extrinsic defects (including iodine and xenon) in the epsilon phase were also investigated to further understand the impact that the metallic precipitates have on fuel performance. PMID:26064629

Protection of Advanced Copper Alloys With Lean Cu-Cr Coatings

NASA Technical Reports Server (NTRS)

Greenbauer-Seng, L. (Technical Monitor); Thomas-Ogbuji, L.

2003-01-01

Advanced copper alloys are used as liners of rocket thrusters and nozzle ramps to ensure dissipation of the high thermal load generated during launch, and Cr-lean coatings are preferred for the protection of these liners from the aggressive ambient environment. It is shown that adequate protection can be achieved with thin Cu-Cr coatings containing as little as 17 percent Cr.

Metal Amorphous Nanocomposite (MANC) Alloy Cores with Spatially Tuned Permeability for Advanced Power Magnetics Applications

NASA Astrophysics Data System (ADS)

Byerly, K.; Ohodnicki, P. R.; Moon, S. R.; Leary, A. M.; Keylin, V.; McHenry, M. E.; Simizu, S.; Beddingfield, R.; Yu, Y.; Feichter, G.; Noebe, R.; Bowman, R.; Bhattacharya, S.

2018-04-01

Metal amorphous nanocomposite (MANC) alloys are an emerging class of soft magnetic materials showing promise for a range of inductive components targeted for higher power density and higher efficiency power conversion applications including inductors, transformers, and rotating electrical machinery. Magnetization reversal mechanisms within these alloys are typically determined by composition optimization as well as controlled annealing treatments to generate a nanocomposite structure composed of nanocrystals embedded in an amorphous precursor. Here we demonstrate the concept of spatially varying the permeability within a given component for optimization of performance by using the strain annealing process. The concept is realized experimentally through the smoothing of the flux profile from the inner to outer core radius achieved by a monotonic variation in tension during the strain annealing process. Great potential exists for an extension of this concept to a wide range of other power magnetic components and more complex spatially varying permeability profiles through advances in strain annealing techniques and controls.

Metal Amorphous Nanocomposite (MANC) Alloy Cores with Spatially Tuned Permeability for Advanced Power Magnetics Applications

NASA Astrophysics Data System (ADS)

Byerly, K.; Ohodnicki, P. R.; Moon, S. R.; Leary, A. M.; Keylin, V.; McHenry, M. E.; Simizu, S.; Beddingfield, R.; Yu, Y.; Feichter, G.; Noebe, R.; Bowman, R.; Bhattacharya, S.

2018-06-01

Metal amorphous nanocomposite (MANC) alloys are an emerging class of soft magnetic materials showing promise for a range of inductive components targeted for higher power density and higher efficiency power conversion applications including inductors, transformers, and rotating electrical machinery. Magnetization reversal mechanisms within these alloys are typically determined by composition optimization as well as controlled annealing treatments to generate a nanocomposite structure composed of nanocrystals embedded in an amorphous precursor. Here we demonstrate the concept of spatially varying the permeability within a given component for optimization of performance by using the strain annealing process. The concept is realized experimentally through the smoothing of the flux profile from the inner to outer core radius achieved by a monotonic variation in tension during the strain annealing process. Great potential exists for an extension of this concept to a wide range of other power magnetic components and more complex spatially varying permeability profiles through advances in strain annealing techniques and controls.

Characterization of rodlike structures in Si-Ge-GaP alloys

NASA Astrophysics Data System (ADS)

Srikant, V.; Jesser, W. A.; Rosi, F. D.

1996-07-01

High-temperature microstructure of Si-Ge alloys containing 10-15 mole % GaP were studied. Quenching the 80/20 Si-Ge alloy (80 at. % Si) from above 1125 °C and the 50/50 Si-Ge alloy (50 at. % Si) from above 1025 °C resulted in a duplex microstructure. The two-phase regions consisted of a regular array of rodlike structures (GaP) in a Si-Ge matrix whereas the monophase regions were pure Si-Ge. These rodlike structures were found to lie along the [001] direction and result in {002} spots in a [100] electron diffraction pattern. The ``rods'' were about 35 and 45 nm in diameter in the case of the 80/20 and 50/50 alloy, respectively. These structures are not stable on annealing and do not form when the solidification rate is decreased.

Design, properties, and weldability of advanced oxidation-resistant FeCrAl alloys

DOE PAGES

Gussev, M. N.; Field, K. G.; Yamamoto, Y.

2017-05-05

FeCrAl alloys are promising as corrosion- and oxidation-resistance materials for extreme high-temperature applications. However, further alloy design and improvement requires a delicate balance between workability, weldability, propensity for '-phase formation, among other factors. Here, a series of advanced oxidant resistant FeCrAl alloys were produced and investigated. Variants with Al (+2%), Nb (+1%), and TiC (0.1, 0.3, and 1%) additions over the reference alloy (Fe-13%Cr-5%Al) were characterized in detail before and after controlled laser beam welding using tensile tests with digital image correlation, SEM-EBSD analysis, and fractography. All investigated alloys demonstrated yield stress in the weldment over 500 MPa; no welding-inducedmore » cracking was observed. However, it was shown that the increase in the Al-content over 5% was detrimental leading to a brittle fracture mechanism and decreased ductility in the weldment. At the same time, Nb and TiC additions were beneficial for preventing grain growth and reducing local softening (yield stress reduction) in the heat-affected zone. The 1% TiC addition also effectively refined grain size in the weldment.« less

Design, properties, and weldability of advanced oxidation-resistant FeCrAl alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gussev, M. N.; Field, K. G.; Yamamoto, Y.

FeCrAl alloys are promising as corrosion- and oxidation-resistance materials for extreme high-temperature applications. However, further alloy design and improvement requires a delicate balance between workability, weldability, propensity for '-phase formation, among other factors. Here, a series of advanced oxidant resistant FeCrAl alloys were produced and investigated. Variants with Al (+2%), Nb (+1%), and TiC (0.1, 0.3, and 1%) additions over the reference alloy (Fe-13%Cr-5%Al) were characterized in detail before and after controlled laser beam welding using tensile tests with digital image correlation, SEM-EBSD analysis, and fractography. All investigated alloys demonstrated yield stress in the weldment over 500 MPa; no welding-inducedmore » cracking was observed. However, it was shown that the increase in the Al-content over 5% was detrimental leading to a brittle fracture mechanism and decreased ductility in the weldment. At the same time, Nb and TiC additions were beneficial for preventing grain growth and reducing local softening (yield stress reduction) in the heat-affected zone. The 1% TiC addition also effectively refined grain size in the weldment.« less

FY 2017 – Thermal Aging Effects on Advanced Structural Materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Meimei; Natesan, K; Chen, Wei-Ying

This report provides an update on the evaluation of the effect of thermal aging on tensile properties of existing laboratory-sized heats of Alloy 709 austenitic stainless steel and the completion of effort on the thermal aging effect on the tensile properties of optimized G92 ferritic-martensitic steel. The report is a Level 3 deliverable in FY17 (M3AT-17AN1602081), under the Work Package AT-17AN160208, “Advanced Alloy Testing - ANL” performed by the Argonne National Laboratory (ANL), as part of the Advanced Reactor Technologies Program.

Manufacture and engine test of advanced oxide dispersion strengthened alloy turbine vanes. [for space shuttle thermal protection

NASA Technical Reports Server (NTRS)

Bailey, P. G.

1977-01-01

Oxide-Dispersion-strengthened (ODS) Ni-Cr-Al alloy systems were exploited for turbine engine vanes which would be used for the space shuttle thermal protection system. Available commercial and developmental advanced ODS alloys were evaluated, and three were selected based on established vane property goals and manufacturing criteria. The selected alloys were evaluated in an engine test. Candidate alloys were screened by strength, thermal fatigue resistance, oxidation and sulfidation resistance. The Ni-16Cr (3 to 5)Al-ThO2 system was identified as having attractive high temperature oxidation resistance. Subsequent work also indicated exceptional sulfidation resistance for these alloys.

Advanced ODS FeCrAl alloys for accident-tolerant fuel cladding

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dryepondt, Sebastien N; Unocic, Kinga A; Hoelzer, David T

2014-09-01

ODS FeCrAl alloys are being developed with optimum composition and properties for accident tolerant fuel cladding. Two oxide dispersion strengthened (ODS) Fe-15Cr-5Al+Y2O3 alloys were fabricated by ball milling and extrusion of gas atomized metallic powder mixed with Y2O3 powder. To assess the impact of Mo on the alloy mechanical properties, one alloy contained 1%Mo. The hardness and tensile properties of the two alloys were close and higher than the values reported for fine grain PM2000 alloy. This is likely due to the combination of a very fine grain structure and the presence of nano oxide precipitates. The nano oxide dispersionmore » was however not sufficient to prevent grain boundary sliding at 800 C and the creep properties of the alloys were similar or only slightly superior to fine grain PM2000 alloy. Both alloys formed a protective alumina scale at 1200 C in air and steam and the mass gain curves were similar to curves generated with 12Cr-5Al+Y2O3 (+Hf or Zr) ODS alloys fabricated for a different project. To estimate the maximum temperature limit of use for the two alloys in steam, ramp tests at a rate of 5 C/min were carried out in steam. Like other ODS alloys, the two alloys showed a significant increase of the mas gains at T~ 1380 C compared with ~1480 C for wrought alloys of similar composition. The beneficial effect of Yttrium for wrought FeCrAl does not seem effective for most ODS FeCrAl alloys. Characterization of the hardness of annealed specimens revealed that the microstructure of the two alloys was not stable above 1000 C. Concurrent radiation results suggested that Cr levels <15wt% are desirable and the creep and oxidation results from the 12Cr ODS alloys indicate that a lower Cr, high strength ODS alloy with a higher maximum use temperature could be achieved.« less

Fabrication and evaluation of advanced titanium structural panels for supersonic cruise aircraft

NASA Technical Reports Server (NTRS)

Payne, L.

1977-01-01

Flightworthy primary structural panels were designed, fabricated, and tested to investigate two advanced fabrication methods for titanium alloys. Skin-stringer panels fabricated using the weldbraze process, and honeycomb-core sandwich panels fabricated using a diffusion bonding process, were designed to replace an existing integrally stiffened shear panel on the upper wing surface of the NASA YF-12 research aircraft. The investigation included ground testing and Mach 3 flight testing of full-scale panels, and laboratory testing of representative structural element specimens. Test results obtained on full-scale panels and structural element specimens indicate that both of the fabrication methods investigated are suitable for primary structural applications on future civil and military supersonic cruise aircraft.

High pressure/temperature equation of state of gold-silver alloys

NASA Astrophysics Data System (ADS)

Evans, W. J.; Jenei, Zs.; Sinogeikin, S. V.; Yang, W.; Shebanova, O.

2010-03-01

It has been reported previously (McKeehan Phys.Rev. 20 p424) that gold-silver alloys crystallize in face centered cubic structures, like their constituant pure elements and the cell parameter of the alloy has a linear relationship with the ratios of Ag/Au in the alloy. We investigate the high-pressure/temperature behavior of gold-silver alloys with different Au/Ag ratios. Powder x-ray diffraction experiments performed at HPCAT/Advanced Photon Source confirm the stability of the alloy's fcc structure to pressures/temperatures exceeding 100 GPa/1000 K. We will present isothermal EOS of the alloys from ambient temperature up to 1000 K, discuss the thermal expansion and its variation with pressure.

High Temperature, Slow Strain Rate Forging of Advanced Disk Alloy ME3

NASA Technical Reports Server (NTRS)

Gabb, Timothy P.; OConnor, Kenneth

2001-01-01

The advanced disk alloy ME3 was designed in the HSR/EPM disk program to have extended durability at 1150 to 1250 F in large disks. This was achieved by designing a disk alloy and process producing balanced monotonic, cyclic, and time-dependent mechanical properties. combined with robust processing and manufacturing characteristics. The resulting baseline alloy, processing, and supersolvus heat treatment produces a uniform, relatively fine mean grain size of about ASTM 7, with as-large-as (ALA) grain size of about ASTM 3. There is a long term need for disks with higher rim temperature capabilities than 1250 F. This would allow higher compressor exit (T3) temperatures and allow the full utilization of advanced combustor and airfoil concepts under development. Several approaches are being studied that modify the processing and chemistry of ME3, to possibly improve high temperature properties. Promising approaches would be applied to subscale material, for screening the resulting mechanical properties at these high temperatures. n obvious path traditionally employed to improve the high temperature and time-dependent capabilities of disk alloys is to coarsen the grain size. A coarser grain size than ASTM 7 could potentially be achieved by varying the forging conditions and supersolvus heat treatment. The objective of this study was to perform forging and heat treatment experiments ("thermomechanical processing experiments") on small compression test specimens of the baseline ME3 composition, to identify a viable forging process allowing significantly coarser grain size targeted at ASTM 3-5, than that of the baseline, ASTM 7.

High pressure/temperature equation of state of gold silver alloys

NASA Astrophysics Data System (ADS)

Jenei, Zsolt; Lipp, Magnus J.; Klepeis, Jae-Hyun P.; Cynn, Hyunchae; Evans, William J.; Park, Changyong

2012-02-01

Gold-silver alloys crystallize in face centered cubic structures, like their constituent pure elements [McKeehan -- Phys.Rev. 20, 424 (1922)]. The cell parameter of the alloys does not scale linearly with the ratio of Ag/Au. In this work we investigate the high-pressure/temperature behavior of gold-silver alloys with different Au/Ag ratios. Powder x-ray diffraction experiments performed at HPCAT/Advanced Photon Source confirm the stability of the alloy's fcc structure to pressures/temperatures exceeding 100 GPa/1000 K. We will present isothermal EOS of the alloys from ambient temperature up to 1000 K, discuss the thermal expansion and its variation with pressure.

Thermal and Mechanical Property Characterization of the Advanced Disk Alloy LSHR

NASA Technical Reports Server (NTRS)

Gabb, Timothy P.; Gayda, John; Telesman, Jack; Kantzos, Peter T.

2005-01-01

A low solvus, high refractory (LSHR) powder metallurgy disk alloy was recently designed using experimental screening and statistical modeling of composition and processing variables on sub-scale disks to have versatile processing-property capabilities for advanced disk applications. The objective of the present study was to produce a scaled-up disk and apply varied heat treat processes to enable full-scale demonstration of LSHR properties. Scaled-up disks were produced, heat treated, sectioned, and then machined into specimens for mechanical testing. Results indicate the LSHR alloy can be processed to produce fine and coarse grain microstructures with differing combinations of strength and time-dependent mechanical properties, for application at temperatures exceeding 1300 F.

Crystal Structural Effect of AuCu Alloy Nanoparticles on Catalytic CO Oxidation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhan, Wangcheng; Wang, Jinglin; Wang, Haifeng

2017-06-07

Controlling the physical and chemical properties of alloy nanoparticles (NPs) is an important approach to optimize NP catalysis. Unlike other tuning knobs, such as size, shape, and composition, crystal structure has received limited attention and not been well understood for its role in catalysis. This deficiency is mainly due to the difficulty in synthesis and fine-tuning of the NPs’ crystal structure. Here, Exemplifying by AuCu alloy NPs with face centered cubic (fcc) and face centered tetragonal (fct) structure, we demonstrate a remarkable difference in phase segregation and catalytic performance depending on the crystal structure. During the thermal treatment in air,more » the Cu component in fcc-AuCu alloy NPs segregates more easily onto the alloy surface as compared to that in fct-AuCu alloy NPs. As a result, after annealing at 250 °C in air for 1 h, the fcc- and fct-AuCu alloy NPs are phase transferred into Au/CuO and AuCu/CuO core/shell structures, respectively. More importantly, this variation in heterostructures introduces a significant difference in CO adsorption on two catalysts, leading to a largely enhanced catalytic activity of AuCu/CuO NP catalyst for CO oxidation. Furthermore, the same concept can be extended to other alloy NPs, making it possible to fine-tune NP catalysis for many different chemical reactions.« less

Research activities of biomedical magnesium alloys in China

NASA Astrophysics Data System (ADS)

Zheng, Yufeng; Gu, Xuenan

2011-04-01

The potential application of Mg alloys as bioabsorable/biodegradable implants have attracted much recent attention in China. Advances in the design and biocompatibility evaluation of bio-Mg alloys in China are reviewed in this paper. Bio-Mg alloys have been developed by alloying with the trace elements existing in human body, such as Mg-Ca, Mg-Zn and Mg-Si based systems. Additionally, novel structured Mg alloys such as porous, composited, nanocrystalline and bulk metallic glass alloys were tried. To control the biocorrosion rate of bio-Mg implant to match the self-healing/regeneration rate of the surrounding tissue in vivo, surface modification layers were coated with physical and chemical methods.

The effect of mechano-chemical treatment on structural properties of the drawn TiNi-based alloy wire

NASA Astrophysics Data System (ADS)

Anikeev, Sergey; Hodorenko, Valentina; Gunther, Victor; Chekalkin, Timofey; Kang, Ji-hoon; Kang, Seung-baik

2018-01-01

The rapid development of biomedical materials with the advanced functional characteristics is a challenging task because of the growing demands for better material properties in-clinically employed. Modern medical devices that can be implanted into humans have evolved steadily by replacing TiNi-based alloys for titanium and stainless steel. In this study, the effect of the mechano-chemical treatment on structural properties of the matrix and surface layer of the drawn TiNi-based alloy wire was assessed. A range of samples have been prepared using different drawing and etching procedures. It is clear from the results obtained that the fabricated samples show a composite structure comprising the complex matrix and textured oxycarbonitride spitted surface layer. The suggested method of surface treatment is a concept to increase the surface roughness for the enhanced bio-performance and better in vivo integration.

Structure formation of 5083 alloy during friction stir welding

NASA Astrophysics Data System (ADS)

Zaikina, A. A.; Kolubaev, A. V.; Sizova, O. V.; Ivanov, K. V.; Filippov, A. V.; Kolubaev, E. A.

2017-12-01

This paper provides a comparative study of structures obtained by friction stir welding and sliding friction of 5083 Al alloy. Optical and electron microscopy reveals identical fine-grained structures with a grain size of ˜5 µm both in the weld nugget zone and subsurface layer in friction independently of the initial grain size of the alloy. It has been suggested that the grain boundary sliding is responsible for the specific material flow pattern in both techniques considered.

Recent advances in the deformation processing of titanium alloys

NASA Astrophysics Data System (ADS)

Tamirisakandala, S.; Bhat, R. B.; Vedam, B. V.

2003-12-01

Titanium (Ti) alloys are special-purpose materials used for several critical applications in aerospace as well as non-aerospace industries, and extensive deformation processing is necessary to shape-form these materials, which poses many challenges due to the microstructural complexities. Some of the recent developments in the deformation processing of Ti alloys and usefulness of integrating the material behavior information with simulation schemes while designing and optimizing manufacturing process schedules are discussed in this paper. Discussions are primarily focused on the most important alloy, Ti-6Al-4V and on developing a clear understanding on the influence of key parameters (e.g., oxygen content, starting microstructure, temperature, and strain rate) on the deformation behavior during hot working. These studies are very useful not only for obtaining controlled microstructures but also to design complex multi-step processing sequences to produce defect-free components. Strain-induced porosity (SIP) has been a serious problem during titanium alloy processing, and improved scientific understanding helps in seeking elegant solutions to avoid SIP. A novel high-speed processing technique for microstructural conversion in titanium has been described, which provides several benefits over the conventional slow-speed practices. The hot working behavior of some of the affordable α+β and β titanium alloys being developed recently—namely, Ti-5.5Al-1Fe, Ti-10V-2Fe-3Al, Ti-6.8Mo-4.5Fe-1.5Al, and Ti-10V-4.5Fe-1.5Al—has been analyzed, and the usefulness of the processing maps in optimizing the process parameters and design of hot working schedules in these alloys is demonstrated. Titanium alloys modified with small additions of boron are emerging as potential candidates for replacing structural components requiring high specific strength and stiffness. Efforts to understand the microstructural mechanisms during deformation processing of Ti-B alloys and the issues

Structure and magnetic properties of nanostructured MnNi alloys fabricated by mechanical alloying and annealing treatments

NASA Astrophysics Data System (ADS)

Jalal, T.; Hossein Nedjad, S.; Khalili Molan, S.

2013-05-01

A nearly equiatomic MnNi alloy was fabricated from the elemental powders by means of mechanical alloying in a planetary ball milling apparatus. X-ray diffraction (XRD), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and measurements of magnetization were conducted to identify the structural states and properties of the prepared alloys. After ball milling for 20 h, a disordered face-centered cubic (f.c.c.) solid solution was formed which increased in lattice parameter by further milling up to 50 h. An exothermic reaction took place at around 300-400°C during continuous heating of the disordered f.c.c. solid solution. This reaction is attributed to a structural ordering leading to the formation of a face-centered tetragonal (f.c.t.) phase with L10 type ordering. Examination of the magnetic properties indicated that the structural ordering increases remnant magnetization and decreases coerecivity.

Structure and properties of stir-cast zinc alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

LeHuy, H.; Blain J.; Masounave, J.

Stir casting (or rheocasting) of ZA-27 zinc alloys was investigated experimentally. By vigorously agitating the alloys during cooling, the dendrites that were forming were fragmented giving a unique structure composed of spherical and rosette shaped particles suspended in the remaining liquid. Under high shear rates ({center dot}{gamma} = 300s{sup {minus}1} or more) the slurries with primary particle concentrations as high as 60% displayed viscosities as low as 20 poises and could easily be casted. The effects of processing variables such as shearing and cooling rates and casting temperatures were studied. Their relative importance on the rheological and microstructural behavior ofmore » the stir cast alloys are discussed. Results from viscosity measurements on slurries show that non-dendritical ZA-27 alloys obey a power law fluid model. Finally, results from mechanical and compressive studies carried out on solidified slurries are discussed and compared to conventional casted and wrought alloy properties.« less

Development and Processing Improvement of Aerospace Aluminum Alloys-Development of AL-Cu-Mg-Ag Alloy (2139)

NASA Technical Reports Server (NTRS)

Cho, Alex; Lisagor, W. Barry; Bales, Thomas T.

2007-01-01

This final report supplement in presentation format describes a comprehensive multi-tasked contract study to continue the development of the silver bearing alloy now registered as aluminum alloy 2139 by the Aluminum Association. Two commercial scale ingots were processed into nominal plate gauges of two, four and six inches, and were extensively characterized in terms of metallurgical and crystallographic structure, and resulting mechanical properties. This report includes comparisons of the property combinations for this alloy and 2XXX and 7XXX alloys more widely used in high performance applications. Alloy 2139 shows dramatic improvement in all combinations of properties, moreover, the properties of this alloy are retained in all gauge thicknesses, contrary to typical reductions observed in thicker gauges of the other alloys in the comparison. The advancements achieved in this study are expected to result in rapid, widespread use of this alloy in a broad range of ground based, aircraft, and spacecraft applications.

Advanced TEM characterization of oxide nanoparticles in ODS Fe–12Cr–5Al alloys

DOE PAGES

Unocic, Kinga A; Hoelzer, David T; Pint, Bruce A

2016-01-01

For oxide nanoparticles present in three oxide-dispersion-strengthened (ODS) Fe–12Cr–5Al alloys containing additions of (1) Y 2O 3 (125Y), (2) Y 2O 3 + ZrO 2 (125YZ), and (3) Y 2O 3 + HfO 2 (125YH), were investigated using transmission and scanning transmission electron microscopy. Furthermore, in all three alloys nano-sized (<3.5 nm) oxide particles distributed uniformly throughout the microstructure were characterized using advanced electron microscopy techniques. In the 125Y alloy, mainly Al 2O 3 and yttrium–aluminum garnet (YAG) phases (Y 3Al 5O 12) were present, while in the 125YZ alloy, additional Zr(C,N) precipitates were identified. The 125YH alloy had themore » most complex precipitation sequence whereby in addition to the YAG and Al 2O 3 phases, Hf(C,N), Y 2Hf 2O 7, and HfO 2 precipitates were also found. The presence of HfO 2 was mainly due to the incomplete incorporation of HfO 2 powder during mechanical alloying of the 125YH alloy. The alloy having the highest total number density of the oxides, the smallest grain size, and the highest Vickers hardness was the 125YZ alloy indicating, that Y 2O 3 + ZrO 2 additions had the strongest effect on grain size and tensile properties. Finally, high-temperature mechanical testing will be addressed in the near future, while irradiation studies are underway to investigate the irradiation resistance of these new ODS FeCrAl alloys.« less

Aluminum alloy material structure impact localization by using FBG sensors

NASA Astrophysics Data System (ADS)

Zhu, Xiubin

2014-12-01

The aluminum alloy structure impact localization system by using fiber Bragg grating (FBG) sensors and impact localization algorithm was investigated. A four-FBG sensing network was established. And the power intensity demodulation method was initialized employing the narrow-band tunable laser. The wavelet transform was used to weaken the impact signal noise. And the impact signal time difference was extracted to build the time difference localization algorithm. At last, a fiber Bragg grating impact localization system was established and experimentally verified. The experimental results showed that in the aluminum alloy plate with the 500 mm*500 mm*2 mm test area, the maximum and average impact abscissa localization errors were 11 mm and 6.25 mm, and the maximum and average impact ordinate localization errors were 9 mm and 4.25 mm, respectively. The fiber Bragg grating sensors and demodulation system are feasible to realize the aviation aluminum alloy material structure impact localization. The research results provide a reliable method for the aluminum alloy material structure impact localization.

Structural characteristics and elevated temperature mechanical properties of AJ62 Mg alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kubásek, J., E-mail: Jiri.Kubasek@vscht.cz; Vojtěch, D.; Martínek, M.

2013-12-15

Structure and mechanical properties of the novel casting AJ62 (Mg–6Al–2Sr) alloy developed for elevated temperature applications were studied. The AJ62 alloy was compared to commercial casting AZ91 (Mg–9Al–1Zn) and WE43 (Mg–4Y–3RE) alloys. The structure was examined by scanning electron microscopy, x-ray diffraction and energy dispersive spectrometry. Mechanical properties were characterized by Viskers hardness measurements in the as-cast state and after a long-term heat treatment at 250 °C/150 hours. Compressive mechanical tests were also carried out both at room and elevated temperatures. Compressive creep tests were conducted at a temperature of 250 °C and compressive stresses of 60, 100 and 140more » MPa. The structure of the AJ62 alloy consisted of primary α-Mg dendrites and interdendritic nework of the Al{sub 4}Sr and massive Al{sub 3}Mg{sub 13}Sr phases. By increasing the cooling rate during solidification from 10 and 120 K/s the average dendrite arm thickness decreased from 18 to 5 μm and the total volume fraction of the interdendritic phases from 20% to 30%. Both factors slightly increased hardness and compressive strength. The room temperature compressive strength and hardness of the alloy solidified at 30 K/s were 298 MPa and 50 HV 5, i.e. similar to those of the as-cast WE43 alloy and lower than those of the AZ91 alloy. At 250 °C the compressive strength of the AJ62 alloy decreased by 50 MPa, whereas those of the AZ91 and WE43 alloys by 100 and 20 MPa, respectively. The creep rate of the AJ62 alloy was higher than that of the WE43 alloy, but significantly lower in comparison with the AZ91 alloy. Different thermal stabilities of the alloys were discussed and related to structural changes during elevated temperature expositions. - Highlights: • Small effect of cooling rate on the compressive strength and hardness of AJ 62 • A bit lower compressive strength of AJ 62 compared to AZ91 at room temperature • Higher resistance of the AJ

Electronic structure of alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ehrenreich, H.; Schwartz, L.M.

1976-01-01

The description of electronic properties of binary substitutional alloys within the single particle approximation is reviewed. Emphasis is placed on a didactic exposition of the equilibrium properties of the transport and magnetic properties of such alloys. Topics covered include: multiple scattering theory; the single band alloy; formal extensions of the theory; the alloy potential; realistic model state densities; the s-d model; and the muffin tin model. 43 figures, 3 tables, 151 references. (GHT)

Structure and Mechanical Properties of Al-Cu-Fe-X Alloys with Excellent Thermal Stability.

PubMed

Školáková, Andrea; Novák, Pavel; Mejzlíková, Lucie; Průša, Filip; Salvetr, Pavel; Vojtěch, Dalibor

2017-11-05

In this work, the structure and mechanical properties of innovative Al-Cu-Fe based alloys were studied. We focused on preparation and characterization of rapidly solidified and hot extruded Al-Cu-Fe, Al-Cu-Fe-Ni and Al-Cu-Fe-Cr alloys. The content of transition metals affects mechanical properties and structure. For this reason, microstructure, phase composition, hardness and thermal stability have been investigated in this study. The results showed exceptional thermal stability of these alloys and very good values of mechanical properties. Alloying by chromium ensured the highest thermal stability, while nickel addition refined the structure of the consolidated alloy. High thermal stability of all tested alloys was described in context with the transformation of the quasicrystalline phases to other types of intermetallics.

Structure and Mechanical Properties of Al-Cu-Fe-X Alloys with Excellent Thermal Stability

PubMed Central

Školáková, Andrea; Novák, Pavel; Mejzlíková, Lucie; Průša, Filip; Salvetr, Pavel; Vojtěch, Dalibor

2017-01-01

In this work, the structure and mechanical properties of innovative Al-Cu-Fe based alloys were studied. We focused on preparation and characterization of rapidly solidified and hot extruded Al-Cu-Fe, Al-Cu-Fe-Ni and Al-Cu-Fe-Cr alloys. The content of transition metals affects mechanical properties and structure. For this reason, microstructure, phase composition, hardness and thermal stability have been investigated in this study. The results showed exceptional thermal stability of these alloys and very good values of mechanical properties. Alloying by chromium ensured the highest thermal stability, while nickel addition refined the structure of the consolidated alloy. High thermal stability of all tested alloys was described in context with the transformation of the quasicrystalline phases to other types of intermetallics. PMID:29113096

Mechanical Properties of Gradient Structure Mg Alloy

NASA Astrophysics Data System (ADS)

Chen, Hongliang; Yang, Jiang; Zhou, Hao; Moering, Jordan; Yin, Zhe; Gong, Yulan; Zhao, KunYu

2017-09-01

In this work, a surface mechanical attrition treatment (SMAT) process was applied to AZ31B magnesium alloy at room temperature. This method produced a gradient structure on the treated AZ31B, in which the grains of the topmost layer are refined to nanoscale sizes. A combination of nanocrystallites at the surface and coarse-grains in the center are the main features of this structure. This structure results in an excellent combination of both strength and ductility. The highest yield strength for the 30 minutes SMAT AZ31B samples increased to 249 ± 5 MPa and the uniform elongation decreased to 9.3 ± 0.8 pct, whereas the original yield strength was only 147 ± 4 MPa and the uniform elongation was 15.4 ± 1.1 pct. Microstructural observations, stress relaxation tests, and hardness tests were used to verify the results. Additionally, there is a specific volume fraction of gradient structure to achieve the best mechanical performance, which is shown to be in the range of 9.3 to 14 pct for the AZ31B alloy.

Advanced Mechanical Properties of a Powder Metallurgy Ti-Al-N Alloy Doped with Ultrahigh Nitrogen Concentration

NASA Astrophysics Data System (ADS)

Shen, J.; Chen, B.; Umeda, J.; Kondoh, K.

2018-03-01

Titanium and its alloys are recognized for their attractive properties. However, high-performance Ti alloys are often alloyed with rare or noble-metal elements. In the present study, Ti alloys doped with only ubiquitous elements were produced via powder metallurgy. The experimental results showed that pure Ti with 1.5 wt.% AlN incorporated exhibited excellent tensile properties, superior to similarly extruded Ti-6Al-4V. Further analysis revealed that its remarkably advanced strength could primarily be attributed to nitrogen solid-solution strengthening, accounting for nearly 80% of the strength increase of the material. In addition, despite the ultrahigh nitrogen concentration up to 0.809 wt.%, the Ti-1.5AlN sample showed elongation to failure of 10%. This result exceeds the well-known limitation for nitrogen (over 0.45 wt.%) that causes embrittlement of Ti alloys.

Low-Temperature Forming of Beta Titanium Alloys

NASA Technical Reports Server (NTRS)

Kaneko, R. S.; Woods, C. A.

1983-01-01

Low cost methods for titanium structural fabrication using advanced cold-formable beta alloys were investigated for application in a Mach 2.7 supersonic cruise vehicle. This work focuses on improving processing and structural efficiencies as compared with standard hot formed and riveted construction of alpha-beta alloy sheet structure. Mechanical property data and manufacturing parameters were developed for cold forming, brazing, welding, and processing Ti-15V-3Cr-3Sn-3Al sheet, and Ti-3Al-8V-6Cr-4Zr on a more limited basis. Cost and structural benefits were assessed through the fabrication and evaluation of large structural panels. The feasibility of increasing structural efficiency of beta titanium structure by selective reinforcement with metal matrix composite was also explored.

Analysis of the Defect Structure of B2 Feal Alloys

NASA Technical Reports Server (NTRS)

Bozzolo, Guillermo; Ferrante, John; Noebe, Ronald D.; Amador, Carlos

1995-01-01

The Bozzolo, Ferrante and Smith (BFS) method for alloys is applied to the study of the defect structure of B2 FeAI alloys. First-principles Linear Muffin Tin Orbital calculations are used to determine the input parameters to the BFS method used in this work. The calculations successfully determine the phase field of the B2 structure, as well as the dependence with composition of the lattice parameter. Finally, the method is used to perform 'static' simulations where instead of determining the ground state configuration of the alloy with a certain concentration of vacancies, a large number of candidate ordered structures are studied and compared, in order to determine not only the lowest energy configurations but other possible metastable states as well. The results provide a description of the defect structure consistent with available experimental data. The simplicity of the BFS method also allows for a simple explanation of some of the essential features found in the concentration dependence of the heat of formation, lattice parameter and the defect structure.

Materials and structural aspects of advanced gas-turbine helicopter engines

NASA Technical Reports Server (NTRS)

Freche, J. C.; Acurio, J.

1979-01-01

Advances in materials, coatings, turbine cooling technology, structural and design concepts, and component-life prediction of helicopter gas-turbine-engine components are presented. Stationary parts including the inlet particle separator, the front frame, rotor tip seals, vanes and combustors and rotating components - compressor blades, disks, and turbine blades - are discussed. Advanced composite materials are considered for the front frame and compressor blades, prealloyed powder superalloys will increase strength and reduce costs of disks, the oxide dispersion strengthened alloys will have 100C higher use temperature in combustors and vanes than conventional superalloys, ceramics will provide the highest use temperature of 1400C for stator vanes and 1370C for turbine blades, and directionally solidified eutectics will afford up to 50C temperature advantage at turbine blade operating conditions. Coatings for surface protection at higher surface temperatures and design trends in turbine cooling technology are discussed. New analytical methods of life prediction such as strain gage partitioning for high temperature prediction, fatigue life, computerized prediction of oxidation resistance, and advanced techniques for estimating coating life are described.

Microscopic structural change in a liquid Fe-C alloy of ~5 GPa

DOE PAGES

Shibazaki, Yuki; Kono, Yoshio; Fei, Yingwei

2015-07-04

The structure of a liquid Fe-3.5 wt% C alloy is examined for up to 7.2 GPa via multiangle energy-dispersive X-ray diffraction using a Paris-Edinburgh type large-volume press. X-ray diffraction data show clear changes in the pressure-dependent peak positions of structure factor and reduced pair distribution function at 5GPa. These results suggest that the liquid Fe-3.5wt%C alloys change structurally at approximately 5GPa. This finding serves as a microscopic explanation for the alloy’s previously observed density change at the same pressure. The pressure dependencies of the nearest and second neighbor distances of the liquid Fe-3.5 wt% C alloy are similar to thosemore » of liquid Fe which exhibits a structural change near the bcc-fcc-liquid triple point (5.2GPa and 1991 K). Here, similarities between Fe-3.5wt% C and Fe suggest that a density change also occurs in liquid Fe and that this structural change extends to other Fe-light element alloys.« less

Effect of Minor Alloying Elements on Localized Corrosion Behavior of Aluminum-Copper-Magnesium based Solid Solution Alloys

NASA Astrophysics Data System (ADS)

Aburada, Tomohiro

2011-12-01

The effects and mechanistic roles of a minor alloying element, Ni, on the localized corrosion behavior were explored by studying (Al75Cu 17Mg8)97Ni3 and Al70Cu 18Mg12 amorphous alloys. To explore the minor alloying element limited to the outer surface layers, the corrosion behavior of Al70Cu 18Mg12 amorphous alloy in solutions with and without Ni 2+ was also studied. Both Ni alloying and Ni2+ in solution improved the localized corrosion resistance of the alloys by ennobling the pitting and repassivation potentials. Pit growth by the selective dissolution of Al and Mg was also suppressed by Ni alloying. Remaining Cu and Ni reorganized into a Cu-rich polycrystalline nanoporous structure with continuous ligaments in pits. The minor Ni alloying and Ni2+ in solution suppressed the coarsening of the ligaments in the dealloyed nanoporous structure. The presence of relatively immobile Ni atoms at the surface suppressed the surface diffusion of Cu, which reduced the coarsening of the nanoporous structure, resulting in the formation of 10 to 30 nm wide Cu ligaments. Two mechanistic roles of minor alloying elements in the improvement of the pitting corrosion resistance of the solid solution alloys are elucidated. The first role is the suppression of active dissolution by altering the atomic structure. Ni in solid solution formed stronger bonds with Al, and reduces the probability of weaker Al-Al bonds. The second role is to hinder dissolution by producing a greater negative shift of the true interfacial potential at the dissolution front under the dealloyed layer due to the greater Ohmic resistance through the finer porous structure. These effects contributed to the elevation of pitting potentials by ennobling the applied potential required to produce enough dissolution for the stabilization of pits. Scientifically, this thesis advances the state of understanding of alloy dissolution, particularly the role of minor alloying elements on preferential oxidation at the atomic

Environmental Studies on Titanium Aluminide Alloys

NASA Technical Reports Server (NTRS)

Brindley, William J.; Bartolotta, Paul A.; Smialek, James L.; Brady, Michael P.

2005-01-01

Titanium aluminides are attractive alternatives to superalloys in moderate temperature applications (600 to 850 C) by virtue of their high strength-to-density ratio (high specific strength). These alloys are also more ductile than competing intermetallic systems. However, most Ti-based alloys tend to degrade through interstitial embrittlement and rapid oxidation during exposure to elevated temperatures. Therefore, their environmental behavior must be thoroughly investigated before they can be developed further. The goals of titanium aluminide environmental studies at the NASA Lewis Research Center are twofold: characterize the degradation mechanisms for advanced structural alloys and determine what means are available to minimize degradation. The studies to date have covered the alpha 2 (Ti3Al), orthorhombic (Ti2AlNb), and gamma (TiAl) classes of alloys.

Detection of structural changes and mechanical properties of light alloys after severe plastic deformation

NASA Astrophysics Data System (ADS)

Krasnoveikin, V. A.; Kozulin, A. A.; Skripnyak, V. A.

2017-11-01

Severe plastic deformation by equal channel angular pressing has been performed to produce light aluminum and magnesium alloy billets with ultrafine-grained structure. The physical and mechanical properties of the processed alloys are examined by studying their microstructure, measuring microhardness, yield strength, and uniaxial tensile strength. A nondestructive testing technique using three-dimensional X-ray tomography is proposed for detecting internal structural defects and monitoring damage formation in the structure of alloys subjected to severe plastic deformation. The investigation results prove the efficiency of the chosen method and selected mode of producing ultrafine-grained light alloys.

Combined electron beam imaging and ab initio modeling of T1 precipitates in Al-Li-Cu alloys

NASA Astrophysics Data System (ADS)

Dwyer, C.; Weyland, M.; Chang, L. Y.; Muddle, B. C.

2011-05-01

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 T1 precipitates in precipitation-hardened Al-Li-Cu aerospace alloys. The results provide an accurate determination of the controversial T1 structure, and demonstrate how next-generation techniques permit the characterization of embedded nanostructures in alloys and other nanostructured materials.

On the atomic structure of liquid Ni-Si alloys: a neutron diffraction study

NASA Astrophysics Data System (ADS)

Gruner, S.; Marczinke, J.; Hennet, L.; Hoyer, W.; Cuello, G. J.

2009-09-01

The atomic structure of the liquid NiSi and NiSi2 alloys is investigated by means of neutron diffraction experiments with isotopic substitution. From experimental data-sets obtained using four Ni isotopes, partial structure factors and pair correlation functions are obtained by applying a reverse Monte Carlo modelling approach. Both alloys were found to exhibit a strong tendency to hetero-coordination within the first coordination shell. In particular, covalent Si-Si bonds with somewhat greater distances seem to influence the structure of the liquid NiSi alloy.

On the atomic structure of liquid Ni-Si alloys: a neutron diffraction study.

PubMed

Gruner, S; Marczinke, J; Hennet, L; Hoyer, W; Cuello, G J

2009-09-23

The atomic structure of the liquid NiSi and NiSi(2) alloys is investigated by means of neutron diffraction experiments with isotopic substitution. From experimental data-sets obtained using four Ni isotopes, partial structure factors and pair correlation functions are obtained by applying a reverse Monte Carlo modelling approach. Both alloys were found to exhibit a strong tendency to hetero-coordination within the first coordination shell. In particular, covalent Si-Si bonds with somewhat greater distances seem to influence the structure of the liquid NiSi alloy.

Structural and magnetic studies of half-metallic Heusler alloy Cr2CoSi nanoparticle synthesized by mechanical-alloying method

NASA Astrophysics Data System (ADS)

Saravanan, G.; Asvini, V.; Kalaiezhily, R. K.; Ravichandran, K.

2018-05-01

Heusler Alloy based Cr2CoSi nanoparticles were synthesized by using ball milling. X-ray diffractions studies were used to characterize the crystal structure of Cr2CoSi nanoparticles and magnetic properties were studied using VSM. XRD data analysis confirms the Heusler alloy phase showing the L21 structure. Magnetic properties are measured for synthesized samples having coercivity Hc = 389 Oe, with high saturation magnetization value Ms = 8.64 emu/g and remenance value Mr = 2.93 emu/g. Synthesized Heusler alloy Cr2CoSi nanoparticles can be potential materials for use in Spin polarized based spin sensors, spin devices, magnetic sensors and transducer applications.

Formation of the structure of thin-sheet rolled product from a high-strength sparingly alloyed aluminum alloy ``nikalin''

NASA Astrophysics Data System (ADS)

Shurkin, P. K.; Belov, N. A.; Akopyan, T. K.; Alabin, A. N.; Aleshchenko, A. S.; Avxentieva, N. N.

2017-09-01

The regime of thermomechanical treatment of flat ingots of a high-strength sparingly alloyed alloy based on the Al-Zn-Mg-Ni-Fe system upon the production of thin-sheet rolled products with a reduction of more than 97% has been substantiated. Using experimental and calculated methods, the structure and phase composition of the experimental alloy in the as cast and deformed state and after heat treatment including quenching with subsequent aging have been studied. It has been found that the structure of the wrought semi-finished products after aging according to T and T1 regimes consists of the precipitation-hardened aluminum matrix and uniformly distributed isolated particles of Al9FeNi with a size of 1-2 μm, which provides a combination of high strength and satisfactory plasticity at the level of standard high-strength aluminum alloys of the Al-Zn-Mg-Cu system. The fractographic analysis confirmed that the tested samples underwent a ductile fracture.

Effect of Iron and Magnesium on Alloy AL9M Structure and Properties

NASA Astrophysics Data System (ADS)

Bazhenov, V. E.; Koltygin, A. V.; Belov, V. D.

2017-09-01

The effect of iron impurity on the structure and properties of aluminum alloy AL9M, especially its action on magnesium distribution within the structure, is studied. The microstructure of a cast component of this alloy broken during operation is analyzed. It is shown that iron impurity has an unfavorable effect on structure and mechanical properties of a casting due to appearance of Al9Fe2Si and Al18Fe2Mg7Si10 intermetallics. Formation of these intermetallics consumes a considerable amount of magnesium and lowers the content of the Q(Al5Cu2Mg8Si6) strengthening phase in the alloy structure.

Structure of tetragonal martensite in the In95.42Cd4.58 cast alloy

NASA Astrophysics Data System (ADS)

Khlebnikova, Yu. V.; Egorova, L. Yu.; Rodionov, D. P.; Kazantsev, V. A.

2017-11-01

The structure of martensite in the In95.42Cd4.58 alloy has been studied by metallography, X-ray diffraction, dilatometry, and transmission electron microscopy. It has been shown that a massive structure built of colonies of tetragonal lamellar plates divided by a twin boundary {101}FCT is formed in the alloy under cooling below the martensite FCC → FCT transition temperature. The alloy recrystallizes after a cycle of FCT → FCC → FCT transitions with a decrease in the grain size by several times compared with the initial structure such fashion that the size of massifs and individual martensite lamella in the massif correlates with the change in the size of the alloy grain. Using thermal cycling, it has been revealed that the alloy tends to stabilize the high-temperature phase.

Production of FR Tubing from Advanced ODS Alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maloy, Stuart Andrew; Lavender, Curt; Omberg, Ron

2016-10-25

Significant research is underway to develop LWR nuclear fuels with improved accident tolerance. One of the leading candidate materials for cladding are the FeCrAl alloys. New alloys produced at ORNL called Gen I and Gen II FeCrAl alloys possess excellent oxidation resistance in steam up to 1400°C and in parallel methods are being developed to produce tubing from these alloys. Century tubing continues to produce excellent tubing from FeCrAl alloys. This memo reports receipt of ~21 feet of Gen I FeCrAl alloy tubing. This tubing will be used for future tests including burst testing, mechanical testing and irradiation testing.

Mo-Si-B alloys for ultrahigh-temperature structural applications.

PubMed

Lemberg, J A; Ritchie, R O

2012-07-10

A continuing quest in science is the development of materials capable of operating structurally at ever-increasing temperatures. Indeed, the development of gas-turbine engines for aircraft/aerospace, which has had a seminal impact on our ability to travel, has been controlled by the availability of materials capable of withstanding the higher-temperature hostile environments encountered in these engines. Nickel-base superalloys, particularly as single crystals, represent a crowning achievement here as they can operate in the combustors at ~1100 °C, with hot spots of ~1200 °C. As this represents ~90% of their melting temperature, if higher-temperature engines are ever to be a reality, alternative materials must be utilized. One such class of materials is Mo-Si-B alloys; they have higher density but could operate several hundred degrees hotter. Here we describe the processing and structure versus mechanical properties of Mo-Si-B alloys and further document ways to optimize their nano/microstructures to achieve an appropriate balance of properties to realistically compete with Ni-alloys for elevated-temperature structural applications. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

High-temperature oxidation of advanced FeCrNi alloy in steam environments

NASA Astrophysics Data System (ADS)

Elbakhshwan, Mohamed S.; Gill, Simerjeet K.; Rumaiz, Abdul K.; Bai, Jianming; Ghose, Sanjit; Rebak, Raul B.; Ecker, Lynne E.

2017-12-01

Alloys of iron-chromium-nickel are being explored as alternative cladding materials to improve safety margins under severe accident conditions. Our research focuses on non-destructively investigating the oxidation behavior of the FeCrNi alloy "Alloy 33" using synchrotron-based methods. The evolution and structure of oxide layer formed in steam environments were characterized using X-ray diffraction, hard X-ray photoelectron spectroscopy, X-ray fluorescence methods and scanning electron microscopy. Our results demonstrate that a compact and continuous oxide scale was formed consisting of two layers, chromium oxide and spinel phase (FeCr2O4) oxides, wherein the concentration of the FeCr2O4 phase decreased from the surface to the bulk-oxide interface.

Strength properties and structure of a submicrocrystalline Al-Mg-Mn alloy under shock compression

NASA Astrophysics Data System (ADS)

Petrova, A. N.; Brodova, I. G.; Razorenov, S. V.

2017-06-01

The results of studying the strength of a submicrocrystalline aluminum A5083 alloy (chemical composition was 4.4Mg-0.6Mn-0.11Si-0.23Fe-0.03Cr-0.02Cu-0.06Ti wt % and Al base) under shockwave compression are presented. The submicrocrystalline structure of the alloy was produced in the process of dynamic channel-angular pressing at a strain rate of 104 s-1. The average size of crystallites in the alloy was 180-460 nm. Hugoniot elastic limit σHEL, dynamic yield stress σy, and the spall strength σSP of the submicrocrystalline alloy were determined based on the free-surface velocity profiles of samples during shock compression. It has been established that upon shock compression, the σHEL and σy of the submicrocrystalline alloy are higher than those of the coarse-grained alloy and σsp does not depend on the grain size. The maximum value of σHEL reached for the submicrocrystalline alloy is 0.66 GPa, which is greater than that in the coarse-crystalline alloy by 78%. The dynamic yield stress is σy = 0.31 GPa, which is higher than that of the coarse-crystalline alloy by 63%. The spall strength is σsp = 1.49 GPa. The evolution of the submicrocrystalline structure of the alloy during shock compression was studied. It has been established that a mixed nonequilibrium grain-subgrain structure with a fragment size of about 400 nm is retained after shock compression, and the dislocation density and the hardness of the alloy are increased.

Trends in aerospace structures

NASA Technical Reports Server (NTRS)

Card, M. F.

1978-01-01

Recent developments indicate that there may soon be a revolution in aerospace structures. Increases in allowable operational stress levels, utilization of high-strength, high-toughness materials, and new structural concepts will highlight this advancement. Improved titanium and aluminum alloys and high-modulus, high-strength advanced composites, with higher specific properties than aluminum and high-strength nickel alloys, are expected to be the principal materials. Significant advances in computer technology will cause major changes in the preliminary design cycle and permit solutions of otherwise too-complex interactive structural problems and thus the development of vehicles and components of higher performance. The energy crisis will have an impact on material costs and choices and will spur the development of more weight-efficient structures. There will also be significant spinoffs of aerospace structures technology, particularly in composites and design/analysis software.

Database on Performance of Neutron Irradiated FeCrAl Alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Field, Kevin G.; Briggs, Samuel A.; Littrell, Ken

The present report summarizes and discusses the database on radiation tolerance for Generation I, Generation II, and commercial FeCrAl alloys. This database has been built upon mechanical testing and microstructural characterization on selected alloys irradiated within the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory (ORNL) up to doses of 13.8 dpa at temperatures ranging from 200°C to 550°C. The structure and performance of these irradiated alloys were characterized using advanced microstructural characterization techniques and mechanical testing. The primary objective of developing this database is to enhance the rapid development of a mechanistic understanding on the radiation tolerancemore » of FeCrAl alloys, thereby enabling informed decisions on the optimization of composition and microstructure of FeCrAl alloys for application as an accident tolerant fuel (ATF) cladding. This report is structured to provide a brief summary of critical results related to the database on radiation tolerance of FeCrAl alloys.« less

Structure and thermomechanical behavior of NiTiPt shape memory alloy wires.

PubMed

Lin, Brian; Gall, Ken; Maier, Hans J; Waldron, Robbie

2009-01-01

The objective of this work is to understand the structure-property relationships in polycrystalline NiTiPt (Ti 42.7 at.% Ni 7.5 at %Pt) with a composition showing pseudoelasticity at ambient temperatures. Structural characterization of the alloy includes grain size determination and texture analysis while the thermomechanical properties are explored using tensile testing. Variation in heat treatment is used as a vehicle to modify microstructure. The results are compared to experiments on Ni-rich NiTi alloy wires (Ti-51.0 at.% Ni), which are in commercial use in various biomedical applications. With regards to microstructure, both alloys exhibit a <111> fiber texture along the wire drawing axis; however, the NiTiPt alloy grain size is smaller than that of the Ni-rich NiTi wires, while the latter materials contain second-phase precipitates. Given the nanometer-scale grain size in NiTiPt and the dispersed, nanometer-scale precipitate size in NiTi, the overall strength and ductility of the alloys are essentially identical when given appropriate heat treatments. Property differences include a much smaller stress hysteresis and smaller temperature dependence of the transformation stress for NiTiPt alloys compared to NiTi alloys. Potential benefits and implications for use in vascular stent applications are discussed.

Improved Electroformed Structural Copper and Copper Alloys

NASA Technical Reports Server (NTRS)

Malone, G. A.; Hudson, W.; Babcock, B.; Edwards, R.

1998-01-01

Electroforming offers a superior means for fabricating internally cooled heat exchangers and structures subjected to thermal environments. Copper is deposited from many such applications because of the good thermal conductivity. It suffers from mediocre yield strength as a structural material and loses mechanical strength at intermediate temperatures. Mechanical properties similar to those of electroformed nickel are desired. Phase 1 examined innovative means to improve deposited copper structural performance. Yield strengths as high as 483 MPa (70 ksi) were obtained with useful ductility while retaining a high level of purity essential to good thermal conductivity. Phase 2 represents a program to explore new additive combinations in copper electrolytes to produce a more fine, equiaxed grain which can be thermally stabilized by other techniques such as alloying in modest degrees and dispersion strengthening. Evaluation of new technology - such as the codeposition of fullerness (diamond-like) particles were made to enhance thermal conductivity in low alloys. A test fire quality tube-bundle engine was fabricated using these copper property improvement concepts to show the superiority of the new coppers and fabrications methods over competitive technologies such as brazing and plasma deposition.

Size-confined fixed-composition and composition-dependent engineered band gap alloying induces different internal structures in L-cysteine-capped alloyed quaternary CdZnTeS quantum dots

NASA Astrophysics Data System (ADS)

Adegoke, Oluwasesan; Park, Enoch Y.

2016-06-01

The development of alloyed quantum dot (QD) nanocrystals with attractive optical properties for a wide array of chemical and biological applications is a growing research field. In this work, size-tunable engineered band gap composition-dependent alloying and fixed-composition alloying were employed to fabricate new L-cysteine-capped alloyed quaternary CdZnTeS QDs exhibiting different internal structures. Lattice parameters simulated based on powder X-ray diffraction (PXRD) revealed the internal structure of the composition-dependent alloyed CdxZnyTeS QDs to have a gradient nature, whereas the fixed-composition alloyed QDs exhibited a homogenous internal structure. Transmission electron microscopy (TEM) and dynamic light scattering (DLS) analysis confirmed the size-confined nature and monodispersity of the alloyed nanocrystals. The zeta potential values were within the accepted range of colloidal stability. Circular dichroism (CD) analysis showed that the surface-capped L-cysteine ligand induced electronic and conformational chiroptical changes in the alloyed nanocrystals. The photoluminescence (PL) quantum yield (QY) values of the gradient alloyed QDs were 27-61%, whereas for the homogenous alloyed QDs, the PL QY values were spectacularly high (72-93%). Our work demonstrates that engineered fixed alloying produces homogenous QD nanocrystals with higher PL QY than composition-dependent alloying.

Ab initio investigation of competing antiferromagnetic structures in low Si-content FeMn(PSi) alloy

NASA Astrophysics Data System (ADS)

Li, Guijiang; Eriksson, Olle; Johansson, Börje; Vitos, Levente

2016-06-01

The antiferromagnetic structures of a low Si-content FeMn(PSi) alloy were investigated by first principles calculations. One possible antiferromagnetic structure in supercell along the c-axis was revealed in FeMnP0.75Si0.25 alloy. It was found that atomic disorder occupation between Fe atom on 3f and Mn atoms on 3g sites is responsible for the formation of antiferromagnetic structures. Furthermore the magnetic competition and the coupling between possible AFM supercells along the c and a-axis can promote a non-collinear antiferromagnetic structure. These theoretical investigations help to deeply understand the magnetic order in FeMn(PSi) alloys and benefit to explore the potential magnetocaloric materials in Fe2P-type alloys.

Natural ageing responses of duplex structured Mg-Li based alloys

PubMed Central

Li, C. Q.; Xu, D. K.; Wang, B. J.; Sheng, L. Y.; Qiao, Y. X.; Han, E. H.

2017-01-01

Natural ageing responses of duplex structured Mg-6%Li and Mg-6%Li-6%Zn-1.2%Y alloys have been investigated. Microstructural analyses revealed that the precipitation and coarsening process of α-Mg particles could occur in β-Li phases of both two alloys during ageing process. Since a certain amount of Mg atoms in β-Li phases were consumed for the precipitation of abundant tiny MgLiZn particles, the size of α-Mg precipitates in Mg-6%Li-6%Zn-1.2%Y alloy was relatively smaller than that in Mg-6%Li alloy. Micro hardness measurements demonstrated that with the ageing time increasing, the α-Mg phases in Mg-6%Li alloy could have a constant hardness value of 41 HV, but the contained β-Li phases exhibited a slight age-softening response. Compared with the Mg-6%Li alloy, the age-softening response of β-Li phases in Mg-6%Li-6%Zn-1.2%Y alloy was much more profound. Meanwhile, a normal age-hardening response of α-Mg phases was maintained. Tensile results indicated that obvious ageing-softening phenomenon in terms of macro tensile strength occurred in both two alloys. Failure analysis demonstrated that for the Mg-6%Li alloy, cracks were preferentially initiated at α-Mg/β-Li interfaces. For the Mg-6%Li-6%Zn-1.2%Y alloy, cracks occurred at both α-Mg/β-Li interfaces and slip bands in α-Mg and β-Li phases. PMID:28053318

Structure, mechanical properties, and grindability of dental Ti-Zr alloys.

PubMed

Ho, Wen-Fu; Chen, Wei-Kai; Wu, Shih-Ching; Hsu, Hsueh-Chuan

2008-10-01

Structure, mechanical properties and grindability of a series of binary Ti-Zr alloys with zirconium contents ranging from 10 to 40 wt% have been investigated. Commercially pure titanium (c.p. Ti) was used as a control. Experimental results indicated that the diffraction peaks of all the Ti-Zr alloys matched those for alpha Ti. No beta-phase peaks were found. The hardness of the Ti-Zr alloys increased as the Zr contents increased, and ranged from 266 HV (Ti-10Zr) to 350 HV (Ti-40Zr). As the concentration of zirconium in the alloys increased, the strength, elastic recovery angles and hardness increased. Moreover, the elastically recoverable angle of Ti-40Zr was higher than of c.p. Ti by as much as 550%. The grindability of each metal was found to be largely dependent on the grinding conditions. The Ti-40Zr alloy had a higher grinding rate and grinding ratio than c.p. Ti at low speed. The grinding rate of the Ti-40Zr alloy at 500 m/min was about 1.8 times larger than that of c.p. Ti, and the grinding ratio was about 1.6 times larger than that of c.p. Ti. Our research suggested that the Ti-40Zr alloy has better mechanical properties, excellent elastic recovery capability and improved grindability at low grinding speed. The Ti-40Zr alloy has a great potential for use as a dental machining alloy.

Hydrogen embrittlement of structural alloys. A technology survey

NASA Technical Reports Server (NTRS)

Carpenter, J. L., Jr.; Stuhrke, W. F.

1976-01-01

Technical abstracts for about 90 significant documents relating to hydrogen embrittlement of structural metals and alloys are reviewed. Particular note was taken of documents regarding hydrogen effects in rocket propulsion, aircraft propulsion and hydrogen energy systems, including storage and transfer systems.

High-temperature oxidation of advanced FeCrNi alloy in steam environments

DOE PAGES

Elbakhshwan, Mohamed S.; Gill, Simerjeet K.; Rumaiz, Abdul K.; ...

2017-07-04

Alloys of iron-chromium-nickel are being explored as alternative cladding materials to improve safety margins under severe accident conditions. Here, our research focuses on non-destructively investigating the oxidation behavior of the FeCrNi alloy “Alloy 33” using synchrotron-based methods. The evolution and structure of oxide layer formed in steam environments were characterized using X-ray diffraction, hard X-ray photoelectron spectroscopy, X-ray fluorescence methods and scanning electron microscopy. In conclusion, our results demonstrate that a compact and continuous oxide scale was formed consisting of two layers, chromium oxide and spinel phase (FeCr 2O 4) oxides, wherein the concentration of the FeCr 2O 4 phasemore » decreased from the surface to the bulk-oxide interface.« less

Dual structural transition in small nanoparticles of Cu-Au alloy

NASA Astrophysics Data System (ADS)

Gafner, Yuri; Gafner, Svetlana; Redel, Larisa; Zamulin, Ivan

2018-02-01

Cu-Au alloy nanoparticles are known to be widely used in the catalysis of various chemical reactions as it was experimentally defined that in many cases the partial substitution of copper with gold increases catalytic activity. However, providing the reaction capacity of alloy nanoparticles the surface electronic structure strongly depends on their atomic ordering. Therefore, to theoretically determine catalytic properties, one needs to use a most real structural model complying with Cu-Au nanoparticles under various external influences. So, thermal stability limits were studied for the initial L12 phase in Cu3Au nanoalloy clusters up to 8.0 nm and Cu-Au clusters up to 3.0 nm at various degrees of Au atom concentration, with molecular dynamics method using a modified tight-binding TB-SMA potential. Dual structural transition L12 → FCC and further FCC → Ih is shown to be possible under the thermal factor in Cu3Au and Cu-Au clusters with the diameter up to 3.0 nm. The temperature of the structural transition FCC → Ih is established to decrease for small particles of Cu-Au alloy under the increase of Au atom concentration. For clusters with this structural transition, the melting point is found to be a linear increasing function of concentration, and for clusters without FCC → Ih structural transition, the melting point is a linear decreasing function of Au content. Thus, the article shows that doping Cu nanoclusters with Au atoms allows to control the forming structure as well as the melting point.

The physical and mechanical metallurgy of advanced O+BCC titanium alloys

NASA Astrophysics Data System (ADS)

Cowen, Christopher John

This thesis comprises a systematic study of the microstructural evolution, phase transformation behavior, elevated-temperature creep behavior, room-temperature and elevated-temperature tensile behavior, and room-temperature fatigue behavior of advanced titanium-aluminum-niobium (Ti-Al-Nb) alloys with and without boron additions. The specific alloys studied were: Ti-5A1-45Nb (at%), Ti-15Al-33Nb (at%), Ti-15Al-33Nb-0.5B (at%), Ti-15Al-33Nb-5B (at%), Ti-21Al-29Nb (at%), Ti-22Al-26Nb (at%), and Ti-22Al-26Nb-5B (at%). The only alloy composition that had been previously studied before this thesis work began was Ti-22Al-26Nb (at%). Publication in peer-reviewed material science journals of the work performed in this thesis has made data available in the scientific literature that was previously non-existent. The knowledge gap for Ti-Al-Nb phase equilibria over the compositional range of Ti-23Al-27Nb (at%) to Ti-12Al-38Nb (at%) that existed before this work began was successfully filled. The addition of 5 at% boron to the Ti-15Al-33Nb alloy produced 5-9 volume percent boride phase needles within the microstructure. The chemical composition of the boride phase measured by electron microprobe was determined to be approximately B 2TiNb. The lattice parameters of the boride phase were simulated through density functional theory calculations by collaborators at the Air Force Research Laboratory based on the measured composition. Using the simulated lattice parameters, electron backscatter diffraction kikuchi patterns and selected area electron diffraction patterns obtained from the boride phase were successfully indexed according to the space group and site occupancies of the B27 orthorhombic crystal structure. This suggests that half the Ti (c) Wyckoff positions are occupied by Ti atoms and the other half are occupied by Nb atoms in the boride phase lattice. Creep deformation behavior is the main focus of this thesis and in particular understanding the dominant creep

Advanced Conversion Coatings for Magnesium alloys

NASA Astrophysics Data System (ADS)

Nibhanupudi, Syam; Manavbasi, Alp

Magnesium and its alloys have excellent physical and mechanical properties due to their high strength-to-weight ratio and are ideal for various applications in automotive, aerospace and defense sectors. However, Mg alloys are also highly susceptible to corrosion under harsh environments. Owing to this carcinogenicity as well as environmental impact of hexavalent chromium fueled by stringent environmental regulations, an environmentally green alternative to the carcinogenic hexavalent chromium coatings on magnesium is due.

Ultrasonic Vibration and Rheocasting for Refinement of Mg-Zn-Y Alloy Reinforced with LPSO Structure

NASA Astrophysics Data System (ADS)

Lü, Shulin; Yang, Xiong; Hao, Liangyan; Wu, Shusen; Fang, Xiaogang; Wang, Jing

2018-05-01

In this work, ultrasonic vibration (UV) and rheo-squeeze casting was first applied on the Mg alloy reinforced with long period stacking ordered (LPSO) structure. The semisolid slurry of Mg-Zn-Y alloy was prepared by UV and processed by rheo-squeeze casting in succession. The effects of UV, Zr addition and squeeze pressure on microstructure of semisolid Mg-Zn-Y alloy were studied. The results revealed that the synergic effect of UV and Zr addition generated a finer microstructure than either one alone when preparing the slurries. Rheo-squeeze casting could significantly refine the LPSO structure and α-Mg matrix in Mg96.9Zn1Y2Zr0.1 alloy without changing the phase compositions or the type of LPSO structure. When the squeeze pressure increased from 0 to 400 MPa, the block LPSO structure was completely eliminated and the average thickness of LPSO structure decreased from 9.8 to 4.3 μm. Under 400 MPa squeeze pressure, the tensile strength and elongation of the rheocast Mg96.9Zn1Y2Zr0.1 alloy reached the maximum values, which were 234 MPa and 17.6%, respectively, due to its fine α-Mg matrix (α1-Mg and α2-Mg grains) and LPSO structure.

Crystal structure and equation of state of Fe-Si alloys at super-Earth core conditions

PubMed Central

Fratanduono, Dayne E.; Coppari, Federica; Newman, Matthew G.; Duffy, Thomas S.

2018-01-01

The high-pressure behavior of Fe alloys governs the interior structure and dynamics of super-Earths, rocky extrasolar planets that could be as much as 10 times more massive than Earth. In experiments reaching up to 1300 GPa, we combine laser-driven dynamic ramp compression with in situ x-ray diffraction to study the effect of composition on the crystal structure and density of Fe-Si alloys, a potential constituent of super-Earth cores. We find that Fe-Si alloy with 7 weight % (wt %) Si adopts the hexagonal close-packed structure over the measured pressure range, whereas Fe-15wt%Si is observed in a body-centered cubic structure. This study represents the first experimental determination of the density and crystal structure of Fe-Si alloys at pressures corresponding to the center of a ~3–Earth mass terrestrial planet. Our results allow for direct determination of the effects of light elements on core radius, density, and pressures for these planets. PMID:29707632

Evolution of twinning in extruded AZ31 alloy with bimodal grain structure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Garcés, G., E-mail: ggarces@cenim.csic.es

2017-04-15

Twinning in extruded AZ31 alloy with a bimodal grain structure is studied under compression along the extrusion direction. This study has combined in-situ measurements during the compression tests by Synchrotron Radiation Diffraction and Acoustic Emission techniques and the evaluation of the microstructure and texture in post-mortem compression samples deformed at different strains. The microstructure of the alloy is characterized by the coexistence of large areas of fine dynamic recrystallized grains and coarse non-recrystallized grains elongated along extrusion direction. Twinning occurs initially in large elongated grains before the macroscopic yield stress which is controlled by the twinning in equiaxed dynamically recrystallizedmore » grains. - Highlights: • The AZ31 extruded at low temperature exhibits a bimodal grains structure. • Twinning takes place before macroscopic yielding in coarse non-DRXed grains. • DRXed grains controls the beginning of plasticity in magnesium alloys with bimodal grain structure.« less

Ab initio calculations of the structural, electronic, thermodynamic and thermal properties of BaSe1-x Te x alloys

NASA Astrophysics Data System (ADS)

Drablia, S.; Boukhris, N.; Boulechfar, R.; Meradji, H.; Ghemid, S.; Ahmed, R.; Omran, S. Bin; El Haj Hassan, F.; Khenata, R.

2017-10-01

The alkaline earth metal chalcogenides are being intensively investigated because of their advanced technological applications, for example in photoluminescent devices. In this study, the structural, electronic, thermodynamic and thermal properties of the BaSe1-x Te x alloys at alloying composition x = 0, 0.25, 0.50, 0.75 and 1 are investigated. The full potential linearized augmented plane wave plus local orbital method designed within the density functional theory was used to perform the total energy calculations. In this research work the effect of the composition on the results of the parameters and bulk modulus as well as on the band gap energy is analyzed. From our results, we found a deviation of the obtained results for the lattice constants from Vegard’s law as well as a deviation of the value of the bulk modulus from the linear concentration dependence. We also carried out a microscopic analysis of the origin of the band gap energy bowing parameter. Furthermore, the thermodynamic stability of the considered alloys was explored through the measurement of the miscibility critical temperature. The quasi-harmonic Debye model, as implemented in the Gibbs code, was used to predict the thermal properties of the BaSe1-x Te x alloys, and these investigations comprise our first theoretical predictions concerning the BaSe1-x Te x alloys.

Advances in Solid State Joining of High Temperature Alloys

NASA Technical Reports Server (NTRS)

Ding, Jeff; Schneider, Judy

2011-01-01

Many of the metals used in the oil and gas industry are difficult to fusion weld including Titanium and its alloys. Solid state joining processes are being pursued as an alternative process to produce robust structures more amenable to high pressure applications. Various solid state joining processes include friction stir welding (FSW) and a patented modification termed thermal stir welding (TSW). The configuration of TSWing utilizes an induction coil to preheat the material minimizing the burden on the weld tool extending its life. This provides the ability to precisely select and control the temperature to avoid detrimental changes to the microstructure. The work presented in this presentation investigates the feasibility of joining various titanium alloys using the solid state welding processes of FSW and TSW. Process descriptions and attributes of each weld process will be presented. Weld process set ]up and welding techniques will be discussed leading to the challenges experienced. Mechanical property data will also be presented.

Ceramic Coatings for Clad (The C 3 Project): Advanced Accident-Tolerant Ceramic Coatings for Zr-Alloy Cladding

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sickafus, Kurt E.; Wirth, Brian; Miller, Larry

The goal of this NEUP-IRP project is to develop a fuel concept based on an advanced ceramic coating for Zr-alloy cladding. The coated cladding must exhibit demonstrably improved performance compared to conventional Zr-alloy clad in the following respects: During normal service, the ceramic coating should decrease cladding oxidation and hydrogen pickup (the latter leads to hydriding and embrittlement). During a reactor transient (e.g., a loss of coolant accident), the ceramic coating must minimize or at least significantly delay oxidation of the Zr-alloy cladding, thus reducing the amount of hydrogen generated and the oxygen ingress into the cladding. The specific objectivesmore » of this project are as follows: To produce durable ceramic coatings on Zr-alloy clad using two possible routes: (i) MAX phase ceramic coatings or similar nitride or carbide coatings; and (ii) graded interface architecture (multilayer) ceramic coatings, using, for instance, an oxide such as yttria-stabilized zirconia (YSZ) as the outer protective layer. To characterize the structural and physical properties of the coated clad samples produced in 1. above, especially the corrosion properties under simulated normal and transient reactor operating conditions. To perform computational analyses to assess the effects of such coatings on fuel performance and reactor neutronics, and to perform fuel cycle analyses to assess the economic viability of modifying conventional Zr-alloy cladding with ceramic coatings. This project meets a number of the goals outlined in the NEUP-IRP call for proposals, including: Improve the fuel/cladding system through innovative designs (e.g. coatings/liners for zirconium-based cladding) Reduce or eliminate hydrogen generation Increase resistance to bulk steam oxidation Achievement of our goals and objectives, as defined above, will lead to safer light-water reactor (LWR) nuclear fuel assemblies, due to improved cladding properties and built-in accident resistance, as

Mechanical properties and the electronic structure of transition of metal alloys

NASA Technical Reports Server (NTRS)

Arsenault, R. J.; Drew, H. D.

1977-01-01

This interdiscipline research program was undertaken in an effort to investigate the relationship between the mechanical strength of Mo based alloys with their electronic structure. Electronic properties of these alloys were examined through optical studies, and the classical solid solution strengthening mechanisms were considered, based on size and molecular differences to determine if these mechanisms could explain the hardness data.

Study of the Influence of Metallurgical Factors on Fatigue and Fracture of Aerospace Structural Materials

DTIC Science & Technology

1989-03-01

11 II. MICROSTRUCTURE/ PROPERTY RELATIONSHIPS IN ADVANCED 12 STRUCTURAL ALLOYS A. Research Objectives 12 B. Summary of Research Efforts 12 1. Fracture...relationship is needed. Figure 5. Correlation between crack growth rates and effective 7 AK for small and large fatigue cracks in a titanium aluminide ...Microstructural/ Property Relationships in Advanced Structural Alloys Table I. Tensile and Fracture Properties of A-Fe-X Alloys in the 13 LT

Influence of aerothermoacoustic treatment on the structure and the properties of a TS6 titanium alloy

NASA Astrophysics Data System (ADS)

Remshev, E. Yu.; Danilin, G. A.; Vorob'eva, G. A.; Kuznetsov, V. V.

2017-01-01

The influence of standard heat or aerothermoacoustic treatment on the structure and the properties of a TS6 titanium alloy is considered. The interrelation between variations in the structure, the grain size, and the properties of the alloy has been detected. The possibilities of aerothermoacoustic treatment to provide a simultaneous increase in the strength and the plasticity of a TS6 alloy upon refining of its grain structure in the course of microplastic deformation and recrystallization are demonstrated.

Structure and Mechanical Properties of As-Cast Ti-5Sn-xMo Alloys.

PubMed

Yu, Hsing-Ning; Hsu, Hsueh-Chuan; Wu, Shih-Ching; Hsu, Shih-Kuang; Ho, Wen-Fu

2017-04-27

Ti-5Sn- x Mo ( x = 0, 1, 3, 5, 7.5, 10, 12.5, 15, 17.5, and 20 wt %) alloys were designed and prepared for application as implant materials with superior mechanical properties. The results demonstrated that the crystal structure and mechanical properties of Ti-5Sn- x Mo alloys are highly affected by their Mo content. The as-cast microstructures of Ti-5Sn- x Mo alloys transformed in the sequence of phases α' → α″ → β, and the morphologies of the alloys changed from a lath structure to an equiaxed structure as the Mo content increased. The α″-phase Ti-5Sn-7.5Mo (80 GPa) and β-phase Ti-5Sn-10Mo (85 GPa) exhibited relatively low elastic moduli and had excellent elastic recovery angles of 27.4° and 37.8°, respectively. Furthermore, they exhibited high ductility and moderate strength, as evaluated using the three-point bending test. Search for a more suitable implant material by this study, Ti-5Sn- x Mo alloys with 7.5 and 10 wt % Mo appear to be promising candidates because they demonstrate the optimal combined properties of microhardness, ductility, elastic modulus, and elastic recovery capability.

Structure and Mechanical Properties of As-Cast Ti–5Sn–xMo Alloys

PubMed Central

Yu, Hsing-Ning; Hsu, Hsueh-Chuan; Wu, Shih-Ching; Hsu, Shih-Kuang; Ho, Wen-Fu

2017-01-01

Ti–5Sn–xMo (x = 0, 1, 3, 5, 7.5, 10, 12.5, 15, 17.5, and 20 wt %) alloys were designed and prepared for application as implant materials with superior mechanical properties. The results demonstrated that the crystal structure and mechanical properties of Ti–5Sn–xMo alloys are highly affected by their Mo content. The as-cast microstructures of Ti–5Sn–xMo alloys transformed in the sequence of phases α′ → α″ → β, and the morphologies of the alloys changed from a lath structure to an equiaxed structure as the Mo content increased. The α″-phase Ti–5Sn–7.5Mo (80 GPa) and β-phase Ti–5Sn–10Mo (85 GPa) exhibited relatively low elastic moduli and had excellent elastic recovery angles of 27.4° and 37.8°, respectively. Furthermore, they exhibited high ductility and moderate strength, as evaluated using the three-point bending test. Search for a more suitable implant material by this study, Ti–5Sn–xMo alloys with 7.5 and 10 wt % Mo appear to be promising candidates because they demonstrate the optimal combined properties of microhardness, ductility, elastic modulus, and elastic recovery capability. PMID:28772820

Structural Evolution of a Ni Alloy Surface During High-Temperature Oxidation

DOE PAGES

Oleksak, Richard P.; Carney, Casey S.; Holcomb, Gordon R.; ...

2017-11-20

We show that considerable structural transformations occur at a Ni alloy surface during the transient stages of high-temperature oxidation. This was demonstrated by exposing the alloy to high-temperature CO 2 for short times at both atmospheric and supercritical pressures. A protective Cr-rich oxide layer formed after only 5 min at 700 °C and persisted for longer exposures up to 500 h. Voids formed and grew over time by the condensation of metal vacancies generated during oxidation, while the alloy surface recrystallized after sufficient oxidation had occurred. The oxygen potential established at the oxide/alloy interface led to oxidation along the newlymore » formed grain boundaries as well as adjacent to and inside of the voids. Al, the most stable oxide-former and present at low concentration in the alloy, was preferentially oxidized in these regions. Furthermore, the results provide an improved understanding of the internal oxidation of Al and its role in enhancing scale adhesion for this class of Ni alloys.« less

Effect of gallium alloying on the structure, the phase composition, and the thermoelastic martensitic transformations in ternary Ni-Mn-Ga alloys

NASA Astrophysics Data System (ADS)

Belosludtseva, E. S.; Kuranova, N. N.; Marchenkova, E. B.; Popov, A. G.; Pushin, V. G.

2016-04-01

The effect of gallium alloying on the structure, the phase composition, and the properties of quasibinary Ni50Mn50- z Ga z (0 ⩽ z ⩽ 25 at %) alloys is studied over a wide temperature range. The influence of the alloy composition on the type of crystal structure in high-temperature austenite and martensite and the critical martensitic transformation temperatures is analyzed. A general phase diagram of the magnetic and structural transformations in the alloys is plotted. The temperature-concentration boundaries of the B2 and L21 superstructures in the austenite field, the tetragonal L10 (2 M) martensite, and the 10 M and 14 M martensite phases with complex multilayer crystal lattices are found. The predominant morphology of martensite is shown to be determined by the hierarchy of the packets of thin coherent lamellae of nano- and submicrocrystalline crystals with planar habit plane boundaries close to {011} B2. Martensite crystals are twinned along one of the 24 24{ {011} }{< {01bar 1} rangle _{B2}} "soft" twinning shear systems, which provides coherent accommodation of the martensitic transformation-induced elastic stresses.

Structural, optical, and spin properties of hydrogenated amorphous silicon-germanium alloys

NASA Astrophysics Data System (ADS)

Stutzmann, M.; Street, R. A.; Tsai, C. C.; Boyce, J. B.; Ready, S. E.

1989-07-01

We report on a detailed study of structural and electronic properties of hydrogenated amorphous silicon-germanium alloys deposited by rf glow discharge from SiH4 and GeH4 in a diode reactor. The chemical composition of the alloys is related to the deposition conditions, with special emphasis on preferential incorporation of Ge into the solid phase and on the role of inert dilutant gases. Hydrogen bonding in the alloys is investigated with nuclear magnetic resonance and vibrational (Raman and infrared) spectroscopy. The optical properties of a-SiGe:H samples deposited under optimal conditions are analyzed with the help of subgap absorption measurements and band-tail luminescence for the entire range of alloy composi-tions. A large part of the article describes an investigation of the electron-spin-resonance response of undoped alloys. The spin density associated with dangling bond defects localized on Si and Ge atoms has been measured as a function of alloy composition for optimized material. In addition, the dependence of the two defect densities on the detailed deposition conditions (rf power, substrate temperature, and dilution) has been determined in a systematic way for alloys deposited from a plasma with a fixed SiH4/GeH4ratio. The results of this study, especially the preferential creation of Ge dangling bonds, are discussed in the context of our structural data. Furthermore, spin resonance is employed to investigate the light-induced degradation (Staebler-Wronski effect) of a-SiGe:H. Finally, the changes of the spin-resonance spectra of a-Si0.7 Ge0.3 :H upon substitutional doping with phosphorus and boron have been obtained experimentally, and are used to construct a model for the electronic density of states in this material.

Advances and Achievements in In Situ Analysis of Corrosion and Structure–Property Relationship in Mg Alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Orlov, D.; Joshi, V.

Every year, TMS Magnesium Committee carefully selects a special topic in magnesium (Mg) related research and development not only having the hottest subject from both academic and industrial perspectives but also demonstrating major achievements within this subject. Following last year’s topic on Mg microallying [1], this year’s focus is on in-situ methods and associated techniques in their broad definition spanning from laboratory- to large- scale facilities to process monitoring. The applications of in-situ techniques have a wide spectrum from the analysis of melts and liquid-solid transitions to solid-state phenomena during thermo-mechanical processing and heat treatments to surface interactions with variousmore » environments. Therefore, such works are of significant interest to scientists working in the area of Mg alloy development as well as to a much broader audience from both academia and industry. This interest is primarily caused by challenges in the analysis of structure-property relationship in Mg alloys, and even cursory glance of literature reveals sharp increase of publications relevant to this topic recently. For instance, very high reactivity of Mg as well as its well-known propensity to substantially alter structure upon unloading in mechanical testing makes it difficult to understand and thus to simulate correlation between microstructures observed in post-mortem analysis and physical processes during testing or fabrication. However, recent advances in in-situ analysis based on large-scale research facilities such as neutron scattering and synchrotron radiation sources as well as microscopy-based, acoustic emission, and other more traditional techniques allowed significant achievements. Apart from apparent development of relevant experimental techniques, a significant part of this success should also be attributed to increasing accessibility of the facilities and simplification of their use from a user perspective. The selection of articles

Electronic structure studies of a clock-reconstructed Al/Pd(1 0 0) surface alloy

NASA Astrophysics Data System (ADS)

Kirsch, Janet E.; Tainter, Craig J.

We have employed solid-state Fenske-Hall band structure calculations to examine the electronic structure of Al/Pd(1 0 0), a surface alloy that undergoes a reconstruction, or rearrangement, of the atoms in the top few surface layers. Surface alloys are materials that consist primarily of a single elemental metal, but which have a bimetallic surface composition that is only a few atomic layers in thickness. The results of this study indicate that reconstruction into a clock configuration simultaneously optimizes the intralayer bonding within the surface plane and the bonding between the first and second atomic layers. These results also allow us to examine the fundamental relationship between the electronic and physical structures of this reconstructed surface alloy.

Recent advances in the development of aerospace materials

NASA Astrophysics Data System (ADS)

Zhang, Xuesong; Chen, Yongjun; Hu, Junling

2018-02-01

In recent years, much progress has been made on the development of aerospace materials for structural and engine applications. Alloys, such as Al-based alloys, Mg-based alloys, Ti-based alloys, and Ni-based alloys, are developed for aerospace industry with outstanding advantages. Composite materials, the innovative materials, are taking more and more important roles in aircrafts. However, recent aerospace materials still face some major challenges, such as insufficient mechanical properties, fretting wear, stress corrosion cracking, and corrosion. Consequently, extensive studies have been conducted to develop the next generation aerospace materials with superior mechanical performance and corrosion resistance to achieve improvements in both performance and life cycle cost. This review focuses on the following topics: (1) materials requirements in design of aircraft structures and engines, (2) recent advances in the development of aerospace materials, (3) challenges faced by recent aerospace materials, and (4) future trends in aerospace materials.

Computational modeling of high-entropy alloys: Structures, thermodynamics and elasticity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gao, Michael C.; Gao, Pan; Hawk, Jeffrey A.

This study provides a short review on computational modeling on the formation, thermodynamics, and elasticity of single-phase high-entropy alloys (HEAs). Hundreds of predicted single-phase HEAs were re-examined using various empirical thermo-physical parameters. Potential BCC HEAs (CrMoNbTaTiVW, CrMoNbReTaTiVW, and CrFeMoNbReRuTaVW) were suggested based on CALPHAD modeling. The calculated vibrational entropies of mixing are positive for FCC CoCrFeNi, negative for BCC MoNbTaW, and near-zero for HCP CoOsReRu. The total entropies of mixing were observed to trend in descending order: CoCrFeNi > CoOsReRu > MoNbTaW. Calculated lattice parameters agree extremely well with averaged values estimated from the rule of mixtures (ROM) if themore » same crystal structure is used for the elements and the alloy. The deviation in the calculated elastic properties from ROM for select alloys is small but is susceptible to the choice used for the structures of pure components.« less

Computational modeling of high-entropy alloys: Structures, thermodynamics and elasticity

DOE PAGES

Gao, Michael C.; Gao, Pan; Hawk, Jeffrey A.; ...

2017-10-12

This study provides a short review on computational modeling on the formation, thermodynamics, and elasticity of single-phase high-entropy alloys (HEAs). Hundreds of predicted single-phase HEAs were re-examined using various empirical thermo-physical parameters. Potential BCC HEAs (CrMoNbTaTiVW, CrMoNbReTaTiVW, and CrFeMoNbReRuTaVW) were suggested based on CALPHAD modeling. The calculated vibrational entropies of mixing are positive for FCC CoCrFeNi, negative for BCC MoNbTaW, and near-zero for HCP CoOsReRu. The total entropies of mixing were observed to trend in descending order: CoCrFeNi > CoOsReRu > MoNbTaW. Calculated lattice parameters agree extremely well with averaged values estimated from the rule of mixtures (ROM) if themore » same crystal structure is used for the elements and the alloy. The deviation in the calculated elastic properties from ROM for select alloys is small but is susceptible to the choice used for the structures of pure components.« less

Structure and Properties of Titanium Tantalum Alloys for Biocompatibility

NASA Astrophysics Data System (ADS)

Huber, Daniel E.

In this thesis, the phase stability and elastic modulus of Ti-Ta simple binary alloys as well as alloys with small additions of ternary elements have been studied. The binary alloy from a nominal 8 to 28 wt.% Ta was first explored using a combinatorial approach. This approach included Laser Engineered Net Shape (LENSTM) processing of materials and subsequent characterization by instrumented indentation and site specific Transmission Electron Microscopy (TEM). The composition range of 15 to 75 wt.% Ta was further explored by more traditional methods that included vacuum arc melting high purity elements, X-Ray Diffraction (XRD) and modulus measurements made by ultrasonic methods. Beyond the simple binary, alloys with low levels of ternary elements, oxygen, aluminum, zirconium and small additions of rare earth oxides were investigated. The crystal structure with space group Cmcm was chosen for it applicability with P63/mmc and Im-3¯m sub group / super group symmetry. This provides a consistent crystal structure framework for the purpose of studying the alpha to beta transformation pathway and associated alpha' and alpha'' martensitic phases. In this case, the pathway is defined by both the lattice parameters and the value of the parameter "y", where the parameter "y" describes the atomic positions of the [002]alpha plane. It was found that the lattice parameter changes in the Ti-Ta binary alloys are similar to structures reported for compositions in the Ti-Nb system of similar atomic percentages. Although samples produced by the LENSTM; process and characterized by instrumented indentation demonstrated the correct trends in modulus behavior, absolute agreement was not seen with modulus values published in literature. Alloys of the binary Ti-Ta system produced from high purity materials do indeed show close agreement with literature where there exist two minima of modulus near the compositions of Ti-28Ta wt.% and Ti-68Ta wt.%. These two minima occur at the discreet

Photoelectron spectroscopic study on the electronic structures of the dental gold alloys and their interaction with L-cysteine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ogawa, Koji; Takahashi, Kazutoshi; Azuma, Junpei

The valence electronic structures of the dental gold alloys, type 1, type 3, and K14, and their interaction with L-cysteine have been studied by ultraviolet photoelectron spectroscopy with synchrotron radiation. It was found that the electronic structures of the type-1 and type-3 dental alloys are similar to that of polycrystalline Au, while that of the K14 dental alloy is much affected by Cu. The peak shift and the change in shape due to alloying are observed in all the dental alloys. It is suggested that the new peak observed around 2 eV for the L-cysteine thin films on all themore » dental alloys may be due to the bonding of S 3sp orbitals with the dental alloy surfaces, and the Cu-S bond, as well as the Au-S and Au-O bonds, may cause the change in the electronic structure of the L-cysteine on the alloys.« less

ITER structural design criteria and their extension to advanced reactor blankets*1

NASA Astrophysics Data System (ADS)

Majumdar, S.; Kalinin, G.

2000-12-01

Applications of the recent ITER structural design criteria (ISDC) are illustrated by two components. First, the low-temperature-design rules are applied to copper alloys that are particularly prone to irradiation embrittlement at relatively low fluences at certain temperatures. Allowable stresses are derived and the impact of the embrittlement on allowable surface heat flux of a simple first-wall/limiter design is demonstrated. Next, the high-temperature-design rules of ISDC are applied to evaporation of lithium and vapor extraction (EVOLVE), a blanket design concept currently being investigated under the US Advanced Power Extraction (APEX) program. A single tungsten first-wall tube is considered for thermal and stress analyses by finite-element method.

Improvement of chemical composition, structure and mechanical properties of heat-resistant chromium-nickel alloy

NASA Astrophysics Data System (ADS)

Varlamova, S.; Trushnikova, A.; Rumyantsev, B.; Butrim, V.; Simonov, V.

2018-04-01

A thermodynamic analysis of a multicomponent system of the Cr-Ni alloy (Cr-32Ni-1,5W-0,25V-0,5Ti) with small additions of refractory metals was carried out. The microstructure and phase composition of the base alloy (I) and alloy with additional alloying (II) were studied. The effect of additives on the mechanical properties of the Cr-Ni alloy at 20, 900 and 1080 °C was shown. The microstructure of alloys I and II was studied in the fracture zone of samples after tensile tests at different temperatures. We studied the effect of small additives on the microstructure of alloys and changes in the morphology of the structural components (phases) as a function of temperature and degree of deformation.

Structural properties of medium-range order in CuNiZr alloy

NASA Astrophysics Data System (ADS)

Gao, Tinghong; Hu, Xuechen; Xie, Quan; Li, Yidan; Ren, Lei

2017-10-01

The evolution characteristics of icosahedral clusters during the rapid solidification of Cu50Ni10Zr40 alloy at cooling rate of 1011 K s-1 are investigated based on molecular dynamics simulations. The structural properties of the short-range order and medium-range order of Cu50Ni10Zr40 alloy are analyzed by several structural characterization methods. The results reveal that the icosahedral clusters are the dominant short-range order structure, and that they assemble themselves into medium-range order by interpenetrating connections. The different morphologies of medium-range order are found in the system and include chain, triangle, tetrahedral, and their combination structures. The tetrahedral morphologies of medium-range order have excellent structural stability with decreasing temperature. The Zr atoms are favorable to form longer chains, while the Cu atoms are favorable to form shorter chains in the system. Those chains interlocked with each other to improve the structural stability.

Fatigue properties of MA 6000E, a gamma-prime strengthened ODS alloy. [Oxide Dispersion Strengthened Ni-base alloy for gas turbine blade applications

NASA Technical Reports Server (NTRS)

Kim, Y. G.; Merrick, H. F.

1980-01-01

MA 6000E is a corrosion resistant, gamma-prime strengthened ODS alloy under development for advanced turbine blade applications. The high temperature, 1093 C, rupture strength is superior to conventional nickel-base alloys. This paper addresses the fatigue behavior of the alloy. Excellent properties are exhibited in low and high cycle fatigue and also thermal fatigue. This is attributed to a unique combination of microstructural features, i.e., a fine distribution of dispersed oxides and other nonmetallics, and the highly elongated grain structure which advantageously modify the deformation characteristics and crack initiation and propagation modes from that characteristic of conventional gamma-prime hardened superalloys.

Synthesis of Ti-Ta alloys with dual structure by incomplete diffusion between elemental powders.

PubMed

Liu, Yong; Li, Kaiyang; Wu, Hong; Song, Min; Wang, Wen; Li, Nianfeng; Tang, Huiping

2015-11-01

In this work, powder metallurgical (PM) Ti-Ta alloys were sintered using blended elemental powders. A dual structure, consisting of Ti-rich and Ta-rich zones, was formed due to the insufficient diffusion between Ti and Ta powders. The microstructure, mechanical properties and in vitro biological properties of the alloys were studied. Results indicated that the alloys have inhomogenous microstructures and compositions, but the grain structures were continuous from the Ti-rich zone to the Ta-rich zone. The Ta-rich zone exhibited a much finer grain size than the Ti-rich zone. The alloys had a high relative density in the range of 95-98%, with the porosity increasing with the content of Ta due to the increased difficulty in sintering and the formation of Kirkendall pores. The alloys had a good combination of low elastic modulus and high tensile strength. The strength of alloys was almost doubled compared to that of the ingot metallurgy alloys with the same compositions. The low elastic modulus was due to the residual pores and the alloying effect of Ta, while the high tensile strength resulted from the strengthening effects of solid solution, fine grain size and α phase. The alloys had a high biocompatibility due to the addition of Ta, and were suitable for the attachment of cells due to the surface porosity. It was also indicated that PM Ti-(20-30)Ta alloys are promising for biomedical applications after the evaluations of both the mechanical and the biological properties. Copyright © 2015 Elsevier Ltd. All rights reserved.

Computation material science of structural-phase transformation in casting aluminium alloys

NASA Astrophysics Data System (ADS)

Golod, V. M.; Dobosh, L. Yu

2017-04-01

Successive stages of computer simulation the formation of the casting microstructure under non-equilibrium conditions of crystallization of multicomponent aluminum alloys are presented. On the basis of computer thermodynamics and heat transfer during solidification of macroscale shaped castings are specified the boundary conditions of local heat exchange at mesoscale modeling of non-equilibrium formation the solid phase and of the component redistribution between phases during coalescence of secondary dendrite branches. Computer analysis of structural - phase transitions based on the principle of additive physico-chemical effect of the alloy components in the process of diffusional - capillary morphological evolution of the dendrite structure and the o of local dendrite heterogeneity which stochastic nature and extent are revealed under metallographic study and modeling by the Monte Carlo method. The integrated computational materials science tools at researches of alloys are focused and implemented on analysis the multiple-factor system of casting processes and prediction of casting microstructure.

Structural, microstructural and thermal analysis of U-(6-x)Zr-xNb alloys (x = 0, 2, 4, 6)

NASA Astrophysics Data System (ADS)

Kaity, Santu; Banerjee, Joydipta; Parida, S. C.; Bhasin, Vivek

2018-06-01

Uranium-rich U-Zr-Nb alloy is considered as a good alternative fuel for fast reactors from the perspective of excellent dimensional stability and desired thermo-physical properties to achieve higher burnup. Detailed investigations related to the structural and microstructural characterization, thermal expansion, phase transformation, microhardness were carried out on U-6Zr, U-4Zr-2Nb, U-2Zr-4Nb and U-6Nb alloys (composition in wt%) where the total amount of alloying elements was restricted to 6 wt%. Structural, microstructural and thermal analysis studies revealed that these alloys undergo a series of transformations from high temperature bcc γ-phase to a variety of equilibrium and intermediate phases depending upon alloy composition, cooling rate and quenching. The structural analysis was carried out by Rietveld refinement. The data of U-Nb and U-Zr-Nb alloys have been highlighted and compared with binary U-Zr alloy.

Study of atomic structure of liquid Hg-In alloys using ab-initio molecular dynamics

NASA Astrophysics Data System (ADS)

Sharma, Nalini; Thakur, Anil; Ahluwalia, P. K.

2015-05-01

Ab-initio molecular dynamics simulations are performed to study the structural properties of liquid Hg-In alloys. The interatomic interactions are described by ab-initio pseudopotentials given by Troullier and Martins. Five liquid Hg-In mixtures (Hg10In90, Hg30In70, Hg50In50, Hg70In30 and Hg90In10) at 299K are considered. The radial distribution function g(r) and structure factor S(q) of considered alloys are compared with respective experimental results for liquid Hg (l-Hg) and (l-In). The radial distribution function g(r) shows the presence of short range order in the systems considered. Smooth curves of Bhatia-Thornton partial structure factors factor shows the presence of liquid state in the considered alloys.

Structural and electronic properties of Ga2O3-Al2O3 alloys

NASA Astrophysics Data System (ADS)

Peelaers, Hartwin; Varley, Joel B.; Speck, James S.; Van de Walle, Chris G.

2018-06-01

Ga2O3 is emerging as an important electronic material. Alloying with Al2O3 is a viable method to achieve carrier confinement, to increase the bandgap, or to modify the lattice parameters. However, the two materials have very different ground-state crystal structures (monoclinic β-gallia for Ga2O3 and corundum for Al2O3). Here, we use hybrid density functional theory calculations to assess the alloy stabilities and electronic properties of the alloys. We find that the monoclinic phase is the preferred structure for up to 71% Al incorporation, in close agreement with experimental phase diagrams, and that the ordered monoclinic AlGaO3 alloy is exceptionally stable. We also discuss bandgap bowing, lattice constants, and band offsets that can guide future synthesis and device design efforts.

Disk Alloy Development

NASA Technical Reports Server (NTRS)

Gabb, Tim; Gayda, John; Telesman, Jack

2001-01-01

The advanced powder metallurgy disk alloy ME3 was designed using statistical screening and optimization of composition and processing variables in the NASA HSR/EPM disk program to have extended durability at 1150 to 1250 "Fin large disks. Scaled-up disks of this alloy were produced at the conclusion of this program to demonstrate these properties in realistic disk shapes. The objective of the UEET disk program was to assess the mechanical properties of these ME3 disks as functions of temperature, in order to estimate the maximum temperature capabilities of this advanced alloy. Scaled-up disks processed in the HSR/EPM Compressor / Turbine Disk program were sectioned, machined into specimens, and tested in tensile, creep, fatigue, and fatigue crack growth tests by NASA Glenn Research Center, in cooperation with General Electric Engine Company and Pratt & Whitney Aircraft Engines. Additional sub-scale disks and blanks were processed and tested to explore the effects of several processing variations on mechanical properties. Scaled-up disks of an advanced regional disk alloy, Alloy 10, were used to evaluate dual microstructure heat treatments. This allowed demonstration of an improved balance of properties in disks with higher strength and fatigue resistance in the bores and higher creep and dwell fatigue crack growth resistance in the rims. Results indicate the baseline ME3 alloy and process has 1300 to 1350 O F temperature capabilities, dependent on detailed disk and engine design property requirements. Chemistry and process enhancements show promise for further increasing temperature capabilities.

Li-atoms-induced structure changes of Guinier–Preston–Bagaryatsky zones in AlCuLiMg alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Duan, S.Y.; Le, Z.; Chen, Z.K.

2016-11-15

Guinier–Preston–Bagaryatsky (GPB) zones are the well-known strengthening precipitates of AlCuMg alloys formed upon thermal ageing. Here we report that when formed in AlCuLiMg alloys the GPB zones can change significantly in morphology and structure. It is shown that though they do still consist of Al, Cu and Mg elements fundamentally, the GPB zones in AlCuLiMg alloys have a rather different structure due to a featured Li-segregation at their interfaces with the matrix and possible Li-replacement of partial Mg atoms in the structure. As such the Li-containing GPB zones often develop from one-dimensional to quasi-two-dimensional precipitates. - Highlights: • We observemore » Guinier–Preston–Bagaryatsky zone variants in AlCuLiMg alloys. • We obtain atomic-resolution images of the precipitates and model their structures. • Li-atoms play a key role in modifying the structure of these precipitate variants.« less

Structure-composition-property relationships in 5xxx series aluminum alloys

NASA Astrophysics Data System (ADS)

Unocic, Kinga A.

Al-Mg alloys are well suited for marine applications due to their low density, ease of fabrication, structural durability, and most notably resistance to corrosion. The purpose of this study is to investigate the effects of alloying additions, mechanical processing and heat treatments on the development of grain boundary phases that have an effect on intergranular corrosion (IGC). Cu, Zn, and Si modified compositions of AA5083 were produced that were subjected to a low and high degree of cold work and various heat treatments. ASTM G67 (NAMLT) intergranular corrosion testing and detailed microstructural characterization for various alloys was carried out. An optimal composition and processing condition that yielded the best intergranular corrosion resistant material was identified based on the ASTM G67 test screening. Further, the outstanding modified AA5083 was selected for further microstructural analysis. This particular alloy with has a magnesium level high enough to make it susceptible to intergranular corrosion is very resistant to IGC. It was found that development of the appropriate sub-structure with some Cu, Si and Zn resulted in a material very resistant to IGC. Formation of many sinks, provided by sub-boundaries, within microstructure is very beneficial since it produces a relatively uniform distribution of Mg in the grain interiors, and this can suppress sensitization of this alloy very successfully. This is a very promising rote for the production of high-strength, and corrosion resistant aluminum alloys. Additionally in this study, TEM sample preparation become very crucial step in grain boundary phase investigation. Focus Ion Beam (FIB) milling was used as a primary TEM sample preparation technique because it enables to extract the samples from desired and very specific locations without dissolving grain boundary phases as it was in conventional electropolishing method. However, other issues specifically relevant to FIB milling of aluminum alloys

Magnetic Behavior of Ni-Fe Core-Shell and Alloy Nanowires

NASA Astrophysics Data System (ADS)

Tripathy, Jagnyaseni; Vargas, Jose; Spinu, Leonard; Wiley, John

2013-03-01

Template assisted synthesis was used to fabricate a series of Ni-Fe core-shell and alloy nanowires. By controlling reaction conditions as well as pore structure, both systems could be targeted and magnetic properties followed as a function of architectures. In the core-shell structure coercivity increases with decrease in shell thickness while for the alloys, coercivity squareness improve with increase pore diameter. Details on the systematic studies of these materials will be presented in terms of hysteretic measurements, including first order reversal curves (FORC), and FMR data. Magnetic variation as a function of structure and nanowire aspect ratios will be presented and the origins of these behaviors discussed. Advanced Material Research Institute

Structure-induced microalloying effect in multicomponent alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guo, Gu -Qing; Yang, Liang; Wu, Shi -Yang

2016-04-28

In this study, the microalloying effect on glass-forming ability (GFA) has been investigated from the structural aspect, by performing synchrotron radiation x-ray diffraction and absorption measurements coupled with simulations in the NiNbZr ternary system. We propose a new parameter which counts the fraction of the fivefold symmetries in all clusters and find it is strongly associated with the GFA. In particular, this structural parameter has the highest value in a composition where the best GFA is achieved. The present work provides an in-depth understanding of microalloying-induced high GFAs in multicomponent alloys.

Solid State Joining of Dissimilar Titanium Alloys

NASA Astrophysics Data System (ADS)

Morton, Todd W.

Solid state joining of titanium via friction stir welding and diffusion bonding have emerged as enablers of efficient monolithic structural designs by the eliminations fasteners for the aerospace industry. As design complexity and service demands increase, the need for joints of dissimilar alloys has emerged. Complex thermomechanical conditions in friction stir weld joints and high temperature deformation behavior differences between alloys used in dissimilar joints gives rise to a highly variable flow pattern within a stir zone. Experiments performed welding Ti-6Al-4V to beta21S show that mechanical intermixing of the two alloys is the primary mechanism for the generation of the localized chemistry and microstructure, the magnitude of which can be directly related to pin rotation and travel speed weld parameters. Mechanical mixing of the two alloys is heavily influenced by strain rate softening phenomena, and can be used to manipulate weld nugget structure by switching which alloy is subjected to the advancing side of the pin. Turbulent mixing of a weld nugget and a significant reduction in defects and weld forces are observed when the beta21S is put on the advancing side of the weld where higher strain rates are present. Chemical diffusion driven by the heat of weld parameters is characterized using energy dispersive x-ray spectroscopy (EDS) and is shown to be a secondary process responsible for generating short-range chemical gradients that lead to a gradient of alpha particle structures. Diffusion calculations are inconsistent with an assumption of steady-state diffusion and show that material interfaces in the weld nugget evolve through the break-down of turbulent interface features generated by material flows. A high degree of recrystallization is seen throughout the welds, with unique, hybrid chemistry grains that are generated at material interfaces in the weld nugget that help to unify the crystal structure of dissimilar alloys. The degree of

Processing of Advanced Cast Alloys for A-USC Steam Turbine Applications

NASA Astrophysics Data System (ADS)

Jablonski, Paul D.; Hawk, Jeffery A.; Cowen, Christopher J.; Maziasz, Philip J.

2012-02-01

The high-temperature components within conventional supercritical coal-fired power plants are manufactured from ferritic/martensitic steels. To reduce greenhouse-gas emissions, the efficiency of pulverized coal steam power plants must be increased to as high a temperature and pressure as feasible. The proposed steam temperature in the DOE/NETL Advanced Ultra Supercritical power plant is high enough (760°C) that ferritic/martensitic steels will not work for the majority of high-temperature components in the turbine or for pipes and tubes in the boiler due to temperature limitations of this class of materials. Thus, Ni-based superalloys are being considered for many of these components. Off-the-shelf forged nickel alloys have shown good promise at these temperatures, but further improvements can be made through experimentation within the nominal chemistry range as well as through thermomechanical processing and subsequent heat treatment. However, cast nickel-based superalloys, which possess high strength, creep resistance, and weldability, are typically not available, particularly those with good ductility and toughness that are weldable in thick sections. To address those issues related to thick casting for turbine casings, for example, cast analogs of selected wrought nickel-based superalloys such as alloy 263, Haynes 282, and Nimonic 105 have been produced. Alloy design criteria, melt processing experiences, and heat treatment are discussed with respect to the as-processed and heat-treated microstructures and selected mechanical properties. The discussion concludes with the prospects for full-scale development of a thick section casting for a steam turbine valve chest or rotor casing.

New polytypes of LPSO structures in an Mg-Co-Y alloy

NASA Astrophysics Data System (ADS)

Jin, Q. Q.; Shao, X. H.; Hu, X. B.; Peng, Z. Z.; Ma, X. L.

2017-01-01

The magnesium alloys containing long-period stacking ordered (LPSO) structures exhibit excellent mechanical properties. Each LPSO structure is known to contain either AB‧C‧A or AB‧C building block and feature its own stacking sequences. By atomic-scale high-angle annular dark field scanning transmission electron microscopy, we find the co-existence of AB‧C‧A and AB‧C building block in a single LPSO structure of the as-cast Mg92Co2Y6 (at.%) alloy, leading to the formation of six new polytypes of the LPSO structures determined as 29H, 51R, 60H, 72R, 102R and 192R. The lattice parameter of each LPSO structure is derived as ? and ? (n presents the number of basal layers in a unit cell). The stacking sequences and the space groups of these newly identified LPSO structures are proposed based on the electron diffraction and atomic-scale aberration-corrected high-resolution images. A random distribution of Co/Y elements in the basal planes of AB‧C‧A and AB‧C structural units is also observed and discussed.

Process Optimization of Dual-Laser Beam Welding of Advanced Al-Li Alloys Through Hot Cracking Susceptibility Modeling

NASA Astrophysics Data System (ADS)

Tian, Yingtao; Robson, Joseph D.; Riekehr, Stefan; Kashaev, Nikolai; Wang, Li; Lowe, Tristan; Karanika, Alexandra

2016-07-01

Laser welding of advanced Al-Li alloys has been developed to meet the increasing demand for light-weight and high-strength aerospace structures. However, welding of high-strength Al-Li alloys can be problematic due to the tendency for hot cracking. Finding suitable welding parameters and filler material for this combination currently requires extensive and costly trial and error experimentation. The present work describes a novel coupled model to predict hot crack susceptibility (HCS) in Al-Li welds. Such a model can be used to shortcut the weld development process. The coupled model combines finite element process simulation with a two-level HCS model. The finite element process model predicts thermal field data for the subsequent HCS hot cracking prediction. The model can be used to predict the influences of filler wire composition and welding parameters on HCS. The modeling results have been validated by comparing predictions with results from fully instrumented laser welds performed under a range of process parameters and analyzed using high-resolution X-ray tomography to identify weld defects. It is shown that the model is capable of accurately predicting the thermal field around the weld and the trend of HCS as a function of process parameters.

Correlations of phase structure and thermal stability for Alnico 8 alloys

NASA Astrophysics Data System (ADS)

Zhao, J. T.; Sun, Y. L.; Liu, L.; Lee, D.; Liu, Z.; Feng, X. C.; Yan, A. R.

2017-11-01

The correlations of phase structure and thermal stability for Alnico 8 alloys is analyzed by three-step aging at 650 °C, 600 °C and 550 °C gradually in this paper. After three-step aging the a1 phase is a chess-like structure in transverse direction and a bamboo-like structure in longitudinal direction. Meanwhile the magnetic energy product ((BH)m) increases from 9.17 MGOe to 10.59 MGOe, and the remanence temperature coefficient a(RT-180 °C) reduces from -2.31 %%/°C to -1.25 %%/°C. The MPMS and VSM measurements indicate that three-step aging makes the a1 phase be single domain particles and dispersed distribution, which plays an important role in optimizing the thermal stability of Alnico alloys.

Iron aluminide alloys with improved properties for high temperature applications

DOEpatents

McKamey, Claudette G.; Liu, Chain T.

1990-01-01

An improved iron aluminide alloy of the DO.sub.3 type that has increased room temperature ductility and improved high elevated temperature strength. The alloy system further is resistant to corrosive attack in the environments of advanced energy corrosion systems such as those using fossil fuels. The resultant alloy is relatively inexpensive as contrasted to nickel based and high nickel steels currently utilized for structural components. The alloy system consists essentially of 26-30 at. % aluminum, 0.5-10 at. % chromium, 0.02-0.3 at. % boron plus carbon, up to 2 at. % molybdenum, up to 1 at. % niobium, up to 0.5 at. % zirconium, up to 0.1 at. % yttrium, up to 0.5 at. % vanadium and the balance iron.

Iron aluminide alloys with improved properties for high temperature applications

DOEpatents

McKamey, C.G.; Liu, C.T.

1990-10-09

An improved iron aluminide alloy of the DO[sub 3] type is described that has increased room temperature ductility and improved high elevated temperature strength. The alloy system further is resistant to corrosive attack in the environments of advanced energy conversion systems such as those using fossil fuels. The resultant alloy is relatively inexpensive as contrasted to nickel based and high nickel steels currently utilized for structural components. The alloy system consists essentially of 26--30 at. % aluminum, 0.5--10 at. % chromium, 0.02--0.3 at. % boron plus carbon, up to 2 at. % molybdenum, up to 1 at. % niobium, up to 0.5 at. % zirconium, up to 0.1 at. % yttrium, up to 0.5 at. % vanadium and the balance iron. 3 figs.

Simulation of Structural Transformations in Heating of Alloy Steel

NASA Astrophysics Data System (ADS)

Kurkin, A. S.; Makarov, E. L.; Kurkin, A. B.; Rubtsov, D. E.; Rubtsov, M. E.

2017-07-01

Amathematical model for computer simulation of structural transformations in an alloy steel under the conditions of the thermal cycle of multipass welding is presented. The austenitic transformation under the heating and the processes of decomposition of bainite and martensite under repeated heating are considered. Amethod for determining the necessary temperature-time parameters of the model from the chemical composition of the steel is described. Published data are processed and the results used to derive regression models of the temperature ranges and parameters of transformation kinetics of alloy steels. The method developed is used in computer simulation of the process of multipass welding of pipes by the finite-element method.

Electronic structure of lead telluride-based alloys, doped with vanadium

NASA Astrophysics Data System (ADS)

Skipetrov, E. P.; Golovanov, A. N.; Slynko, E. I.; Slynko, V. E.

2013-01-01

The crystal structure, composition, galvanomagnetic properties in low magnetic fields (4.2 K ≤ T ≤ 300 K, B ≤ 0.07 T), and the Shubnikov-de Haas effect (T = 4.2 K, B ≤ 7 T) are studied in Pb1-x-ySnxVyTe (x = 0, 0.05-0.18) alloys synthesized by the Bridgman technique with variable vanadium impurity concentrations. It is shown that increasing the vanadium content leads to the formation of regions enriched in vanadium and of microscopic inclusions of compounds with compositions close to V3Te4. In Pb1-yVyTe stabilization of the Fermi level by a deep vanadium level, an insulator-metal transition, and a rise in the free electron concentration are observed as the vanadium content is increased. The variation in the free charge carrier concentration with increasing vanadium concentration in Pb1-yVyTe and Pb1-x-ySnxVyTe (x = 0.05-0.18) alloys is compared. Possible models for rearrangement of the electronic structure in Pb1-x-ySnxVyTe alloys with vanadium doping are discussed.

Application of holographic interferometry for analysis of the dynamic and modal characteristics of an advanced exotic metal airfoil structure

NASA Astrophysics Data System (ADS)

Fein, Howard

1999-03-01

Holographic Interferometry has been successfully employed to characterize the materials and behavior of diverse types of structures under stress. Specialized variations of this technology have also been applied to define dynamic and vibration related structural behavior. Such applications of holographic technique offer some of the most effective methods of modal and dynamic analysis available. Real-time dynamic testing of the modal and mechanical behavior of aerodynamic control and airfoil structures for advanced aircraft has always required advanced instrumentation for data collection in either actual flight test or wind-tunnel simulations. Advanced optical holography techniques are alternate methods which result in actual full-field behavioral data on the ground in a noninvasive environment. These methods offer significant insight in both the development and subsequent operational test and modeling of advanced exotic metal control structures and their integration with total vehicle system dynamics. Structures and materials can be analyzed with very low amplitude excitation and the resultant data can be used to adjust the accuracy mathematically derived structural and behavioral models. Holographic Interferometry offers a powerful tool to aid in the developmental engineering of exotic metal structures for high stress applications. Advanced Titanium alloy is a significant example of these sorts of materials which has found continually increased use in advanced aerodynamic, undersea, and other highly mobil platforms. Aircraft applications in particular must consider environments where extremes in vibration and impulsive mechanical stress can affect both operation and structural stability. These considerations present ideal requisites for analysis using advanced holographic methods in the initial design and test of structures made with such advanced materials. Holographic techniques are nondestructive, real- time, and definitive in allowing the identification of

Low void content autoclave molded titanium alloy and polyimide graphite composite structures.

NASA Technical Reports Server (NTRS)

Vaughan, R. W.; Jones, R. J.; Creedon, J. F.

1972-01-01

This paper discusses a resin developed for use in autoclave molding of polyimide graphite composite stiffened, titanium alloy structures. Both primary and secondary bonded structures were evaluated that were produced by autoclave processing. Details of composite processing, adhesive formulary, and bonding processes are provided in this paper, together with mechanical property data for structures. These data include -65 F, room temperature, and 600 F shear strengths; strength retention after aging; and stress rupture properties at 600 F under various stress levels for up to 1000 hours duration. Typically, shear strengths in excess of 16 ksi at room temperature with over 60% strength retention at 600 F were obtained with titanium alloy substrates.

Identification of salt-alloy combinations for thermal energy storage applications in advanced solar dynamic power systems

NASA Technical Reports Server (NTRS)

Whittenberger, J. D.; Misra, A. K.

1987-01-01

Thermodynamic calculations based on the available data for flouride salt systems reveal that a number of congruently melting compositions and eutectics exist which have the potential to meet the lightweight, high energy storage requirements imposed for advanced solar dynamic systems operating between about 1000 and 1400 K. Compatibility studies to determine suitable containment alloys to be used with NaF-22CaF2-13MgF2, NaF-32CaF2, and NaF-23MgF2 have been conducted at the eutectic temperature + 25 K for each system. For these three NaF-based eutectics, none of the common, commercially available high temperature alloys appear to offer adequate corrosion resistance for a long lifetime; however mild steel, pure nickel and Nb-1Zr could prove useful. These latter materials suggest the possibility that a strong, corrosion resistant, nonrefractory, elevated temperature alloy based on the Ni-Ni3Nb system could be developed.

4-d magnetism: Electronic structure and magnetism of some Mo-based alloys

NASA Astrophysics Data System (ADS)

Liu, Yong; Bose, S. K.; Kudrnovský, J.

2017-02-01

We report results of a first-principles density-functional study of alloys of the 4 d -element Mo with group IV elements Si, Ge and Sn in zinc blende (ZB) and rock salt (RS) structures. The study was motivated by a similar study of ours based on the 4 d -element Tc, which showed the presence of half-metallic states with integer magnetic moment (1μB) per formula unit in TcX (X=C, Si, Ge) alloys. The calculated Curie temperatures for the ferromagnetic (FM) phases were low, around or less than 300 K. Searching for the possibility of 4 d -based alloys with higher Curie temperatures we have carried out the study involving the elements Mo, Ru and Rh. Among these the most promising case appears to be that involving the element Mo. Among the MoX (X=Si, Ge, Sn) alloys in ZB and RS structures, both MoGe and MoSn in ZB structures are found to possess an integer magnetic moment of 2μB per formula unit. ZB MoSn can be classified as a marginal/weak half-metal or a spin gapless semiconductor, while ZB MoGe would be best described as a gapless magnetic semiconductor. The calculated Curie temperatures are in the range 300-700 K. Considering the theoretical uncertainty in the band gaps due not only to the treatment of exchange and correlation effects, but density functional theory itself, these classifications may change somewhat, but both merit investigation from the viewpoint of potential spintronic application. Based on their higher Curie temperatures, Mo-based alloys would serve such purpose better than the previously reported Tc-based ones.

Dendritic growth and structure of undercooled nickel base alloys

NASA Technical Reports Server (NTRS)

Flemings, M. C.; Shiohara, Y.

1988-01-01

The principal objectives of this overall investigation are to: study means for obtaining high undercooling in levitation melted droplets, and study structures produced upon the solidification of these undercooled specimens. Thermal measurements are made of the undercooling, and of the rapid recalescence, to develop an understanding of the solidification mechanism. Comparison of results is made with the modeling studies. Characterization and metallographic work is done to gain an understanding of the relationship between rapid solidification variables and the structures so produced. In ground based work to date, solidification of undercooled Ni-25 wt percent Sn alloy was observed by high-speed cinematography and the results compared with optical temperature measurements. Also in ground based work, high-speed optical temperature measurements were made of the solidification behavior of levitated metal samples within a transparent glass medium. Two undercooled Ni-Sn alloys were examined. Measurements were carried out on samples at undercoolings up to 330 K. Microstructures of samples produced in ground based work were determined by optical metallography and by SEM, and microsegregation by electron microprobe measurements. A series of flight tests were planned to conduct experiments similar to the ground based experiments. The Space Shuttle Columbia carried an alloy undercooled experiment in the STS 61-C mission in January 1986. A sample of Ni-32.5 wt percent Sn eutectic was melted and solidified under microgravity conditions.

Method of producing superplastic alloys and superplastic alloys produced by the method

NASA Technical Reports Server (NTRS)

Troeger, Lillianne P. (Inventor); Starke, Jr., Edgar A. (Inventor); Crooks, Roy (Inventor)

2002-01-01

A method for producing new superplastic alloys by inducing in an alloy the formation of precipitates having a sufficient size and homogeneous distribution that a sufficiently refined grain structure to produce superplasticity is obtained after subsequent PSN processing. An age-hardenable alloy having at least one dispersoid phase is selected for processing. The alloy is solution heat-treated and cooled to form a supersaturated solid solution. The alloy is plastically deformed sufficiently to form a high-energy defect structure useful for the subsequent heterogeneous nucleation of precipitates. The alloy is then aged, preferably by a multi-stage low and high temperature process, and precipitates are formed at the defect sites. The alloy then is subjected to a PSN process comprising plastically deforming the alloy to provide sufficient strain energy in the alloy to ensure recrystallization, and statically recrystallizing the alloy. A grain structure exhibiting new, fine, equiaxed and uniform grains is produced in the alloy. An exemplary 6xxx alloy of the type capable of being produced by the present invention, and which is useful for aerospace, automotive and other applications, is disclosed and claimed. The process is also suitable for processing any age-hardenable aluminum or other alloy.

Change In The Electronic Structure And Optical Absorption Of Cuprate Delafossites Via B-site Alloying

NASA Astrophysics Data System (ADS)

Beesley, Ramon; Panapitiya, Gihan; Lewis, James; Lewis Group Team

Delafossite oxides are a family of materials with the form ABO2 , where the A-site is a monovalent cation (Cu , Ag , Au) and the B-site is a trivalent cation (Ga , Al , In). Delafossites typically have a wide optical band gap, this band gap may be tuned by adding a second B-site element forming an AB(1- x) 1B(x)2O2 alloy. We investigate changes in the electronic structure of CuAlO2 , CuGaO2 , and CuInO2 when alloyed with CuFeO2 . Using the FIREBALL program to optimize the atomic structure, calculate the total and partial density of states, calculate the valence band edge for each alloy level, and investigate the clustering factor of the second B-site atom, it is found that alloying with Fe creates midgap states caused by Fe - O interactions. From the partial density of state, each type of atoms contribution to the change in the valence band edge can be seen. Observed changes to the materials include increased optical absorption in the visible range, and symmetry breaking because of the deformation in the crystal structure. The CuFeO2 alloying percentages range from 0-5%. We are synthesizing these alloys to experimentally verify the changes in the optical absorption spectra.

Transport, Structural and Mechanical Properties of Quaternary FeVTiAl Alloy

NASA Astrophysics Data System (ADS)

Bhat, Tahir Mohiuddin; Gupta, Dinesh C.

2016-11-01

The electronic, structural, magnetic and transport properties of FeVTiAl quaternary alloy have been investigated within the framework of density functional theory. The material is a completely spin-polarized half-metallic ferromagnet in its ground state with F-43m structure. The structural stability was further confirmed by elastic constants in the cubic phase with high Young's modulus and brittle nature. The present study predicts an energy band gap of 0.72 eV in a localized minority spin channel at equilibrium lattice parameter of 6.00 Å. The transport properties of the material are discussed based on the Seebeck coefficient, and electrical and thermal conductivity coefficients. The alloy presents large values of Seebeck coefficients, ~39 μV K-1 at room temperature (300 K), and has an excellent thermoelectric performance with ZT = ~0.8.

Study of atomic structure of liquid Hg-In alloys using ab-initio molecular dynamics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sharma, Nalini; Ahluwalia, P. K.; Thakur, Anil

2015-05-15

Ab-initio molecular dynamics simulations are performed to study the structural properties of liquid Hg-In alloys. The interatomic interactions are described by ab-initio pseudopotentials given by Troullier and Martins. Five liquid Hg-In mixtures (Hg{sub 10}In{sub 90}, Hg{sub 30}In{sub 70}, Hg{sub 50}In{sub 50}, Hg{sub 70}In{sub 30} and Hg{sub 90}In{sub 10}) at 299K are considered. The radial distribution function g(r) and structure factor S(q) of considered alloys are compared with respective experimental results for liquid Hg (l-Hg) and (l-In). The radial distribution function g(r) shows the presence of short range order in the systems considered. Smooth curves of Bhatia-Thornton partial structure factors factormore » shows the presence of liquid state in the considered alloys.« less

Structure and phase composition of ultrafine-grained TiNb alloy after high-temperature annealings

NASA Astrophysics Data System (ADS)

Eroshenko, Anna Yu.; Glukhov, Ivan A.; Mairambekova, Aikol; Tolmachev, Alexey I.; Sharkeev, Yurii P.

2017-12-01

The paper presents the experimental data observed in the microstructure and phase composition of ultrafine-grained Ti-40 mass % Nb (Ti40Nb) alloy after high-temperature annealings. The ultrafine-grained Ti40Nb alloy is produced by severe plastic deformation (SPD). This method includes multiple abc-pressing and multi-pass rolling followed by further pre-recrystallizing annealing which, in its turn, enhances the formation of ultrafine-grained structures with mean size of 0.28 µm involving stable β- and α-phase and metastable nanosized ω-phase in the alloy. It is shown that annealing at 500°C preserves the ultrafine-grained structure and phase composition. In cases of annealing at 800°C the ultrafine-grained state transforms into the coarse-grained state. The stable β-phase and the nanosized metastable ω-phase have been identified in the coarse-grained structure.

Interacting quasi-band model for electronic states in compound semiconductor alloys: Zincblende structure

NASA Astrophysics Data System (ADS)

Shinozuka, Yuzo; Oda, Masato

2015-09-01

The interacting quasi-band model proposed for electronic states in simple alloys is extended for compound semiconductor alloys with general lattice structures containing several atoms per unit cell. Using a tight-binding model, a variational electronic wave function for quasi-Bloch states yields a non-Hermitian Hamiltonian matrix characterized by matrix elements of constituent crystals and concentration of constituents. Solving secular equations for each k-state yields the alloy’s energy spectrum for any type of randomness and arbitrary concentration. The theory is used to address III-V (II-VI) alloys with a zincblende lattice with crystal band structures well represented by the sp3s* model. Using the resulting 15 × 15 matrix, the concentration dependence of valence and conduction bands is calculated in a unified scheme for typical alloys: Al1-xGaxAs, GaAs1-xPx, and GaSb1-xPx. Results agree well with experiments and are discussed with respect to the concentration dependence, direct-indirect gap transition, and band-gap-bowing origin.

Tuning structural motifs and alloying of bulk immiscible Mo-Cu bimetallic nanoparticles by gas-phase synthesis

NASA Astrophysics Data System (ADS)

Krishnan, Gopi; Verheijen, Marcel A.; Ten Brink, Gert H.; Palasantzas, George; Kooi, Bart J.

2013-05-01

Nowadays bimetallic nanoparticles (NPs) have emerged as key materials for important modern applications in nanoplasmonics, catalysis, biodiagnostics, and nanomagnetics. Consequently the control of bimetallic structural motifs with specific shapes provides increasing functionality and selectivity for related applications. However, producing bimetallic NPs with well controlled structural motifs still remains a formidable challenge. Hence, we present here a general methodology for gas phase synthesis of bimetallic NPs with distinctively different structural motifs ranging at a single particle level from a fully mixed alloy to core-shell, to onion (multi-shell), and finally to a Janus/dumbbell, with the same overall particle composition. These concepts are illustrated for Mo-Cu NPs, where the precise control of the bimetallic NPs with various degrees of chemical ordering, including different shapes from spherical to cube, is achieved by tailoring the energy and thermal environment that the NPs experience during their production. The initial state of NP growth, either in the liquid or in the solid state phase, has important implications for the different structural motifs and shapes of synthesized NPs. Finally we demonstrate that we are able to tune the alloying regime, for the otherwise bulk immiscible Mo-Cu, by achieving an increase of the critical size, below which alloying occurs, closely up to an order of magnitude. It is discovered that the critical size of the NP alloy is not only affected by controlled tuning of the alloying temperature but also by the particle shape.Nowadays bimetallic nanoparticles (NPs) have emerged as key materials for important modern applications in nanoplasmonics, catalysis, biodiagnostics, and nanomagnetics. Consequently the control of bimetallic structural motifs with specific shapes provides increasing functionality and selectivity for related applications. However, producing bimetallic NPs with well controlled structural motifs still

Modeling of the Structure of Disordered Metallic Alloys and Its Transformation Under Thermal Forcing

NASA Astrophysics Data System (ADS)

Cress, Ryan Paul

The morphology of disordered binary metallic alloys is investigated. The structure of disordered binary metallic alloys is modeled as a randomly close packed (RCP) assembly of atoms. It was observed through a 2-D binary hard sphere experiment that RCP structure can be modeled as a mixture of nano-crystallites and glassy matter. We define the degree of crystallinity as the fraction of atoms contained in nano-crystallites in an RCP medium. Nano-crystallites by size in a crystallite size distribution were determined experimentally to define the morphology of the RCP medium. Both the degree of crystallinity and the crystallite size distribution have been found to be determined by the composition of a given binary mixture. A 2-D Monte Carlo simulation was developed in order to replicate the RCP structure observed in the experiment which is then extended to cases of arbitrary composition. Crystallites were assumed to be spherical with isotropic cross sections. The number of atoms in an individual crystallite in 2-D is simply transformed into the number of atoms in 3-D; we then obtain the crystallite size distribution in 3-D. This experiment accounts for the contribution from the repulsive core of the inter-atomic potential. The attractive part of the potential is recovered by constructing spherical nano-crystallites of a given radius from a crystalline specimen of each given alloy. A structural model of a disordered alloy is thus obtained. With the basic structure of the RCP medium defined, the response to heating would be in the form of changes to the crystallite size distribution. This was first investigated in a hard sphere mechanical oven experiment. The experimental setup consists of a 2-D cell which is driven by two independent stepper motors. The motors drive a binary RCP bed of spheres on a slightly tilted plane according to a chaotic algorithmm. The motors are driven at four different speed settings. The RCP medium was analyzed using a sequence of digital images

High-temperature, low-cycle fatigue of advanced copper-base alloys for rocket nozzles. Part 2: NASA 1.1, Glidcop, and sputtered copper alloys

NASA Technical Reports Server (NTRS)

Conway, J. B.; Stentz, R. H.; Berling, J. T.

1974-01-01

Short-term tensile and low-cycle fatigue data are reported for five advance copper-base alloys: Sputtered Zr-Cu as received, sputtered Zr-Cu heat-treated, Glidcop AL-10, and NASA alloys 1-1A and 1-1B. Tensile tests were performed in argon at 538 C using an axial strain rate of 0.002/sec. Yield strength and ultimate tensile strength data are reported along with reduction in area values. Axial strain controlled low-cycle fatigue tests were performed in argon at 538C using an axial strain rate of 0.002/sec to define the fatigue life over the range from 100 to 3000 cycles for the five materials studied. It was found that the fatigue characteristics of the NASA 1-1A and NASA 1-1B compositions are identical and represent fatique life values which are much greater than those for the other materials tested. The effect of temperature on NASA 1-1B alloy at a strain rate of 0.002/sec was evaluated along with the effect of strain rates of 0.0004 and 0.01/sec at 538 C. Hold-time data are reported for the NASA 1-1B alloy at 538 C using 5 minute hold periods in tension only and compression only at two different strain range values. Hold periods in tension were much more detrimental than hold periods in compression.

Microstructure and mechanical characteristics of gradient structured Cu and Cu alloys processed by surface mechanical attrition treatment

NASA Astrophysics Data System (ADS)

Hu, XZ; Cheng, LP; Chen, HL; Yin, Z.; Zhang, Z.; Shu, BP; Gong, YL; Zhu, XK

2017-05-01

Cu-Al-Zn alloys with different stacking fault energy (SFE) were processed by surface mechanical attrition treatment (SMAT) at cryogenic temperature (CT), mechanical properties of gradient structured Cu-Al-Zn alloys were investigated in this study. Al and Zn content in alloys, which result in the decrease of SFE, can contribute to the increase in strength. Cu-4.5wt%Al-14.3wt%Zn alloy with the lower SFE shows that the strength increased, the ductility did not decrease significantly with increasing processing time, and the strength can be improved by a thicker gradient structure (GS) layer. The better combination of strength and ductility was achieved in Cu-4.5wt%Al-14.3wt%Zn alloy with lower SFE.

Aging Optimization of Aluminum-Lithium Alloy C458 for Application to Cryotank Structures

NASA Technical Reports Server (NTRS)

Sova, B. J.; Sankaran, K. K.; Babel, H. W.; Farahmand, B.; Rioja, R.

2003-01-01

This viewgraph report presents an examination of the fracture toughness of aluminum-lithium alloy C458 for use in cryotank structures. Topics cover include: cryogenics, alloy composition, strengthing precipitates in C458, cryogenic fracture toughness improvements, design of experiments for measuring aging optimization of C458 plate and effects of aging of properties of C458 plate.

Effects of neutron irradiation on deformation behavior of nickel-base fastener alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bajaj, R.; Mills, W.J.; Kammenzind, B.F.

1999-07-01

This paper presents the effects of neutron irradiation on the fracture behavior and deformation microstructure of high-strength nickel-base alloy fastener materials, Alloy X-750 and Alloy 625. Alloy X-750 in the HTH condition, and Alloy 625 in the direct aged condition were irradiated to a fluence of 2.4x10{sup 20} n/cm{sup 2} at 264 C in the Advanced Test Reactor. Deformation structures at low strains were examined. It was previously shown that Alloy X-750 undergoes hardening, a significant degradation in ductility and an increase in intergranular fracture. In contrast, Alloy 625 had shown softening with a concomitant increase in ductility and transgranularmore » failure after irradiation. The deformation microstructures of the two alloys were also different. Alloy X-750 deformed by a planar slip mechanism with fine microcracks forming at the intersections of slip bands with grain boundaries. Alloy 625 showed much more homogeneous deformation with fine, closely spaced slip bands and an absence of microcracks. The mechanism(s) of irradiation assisted stress corrosion cracking (IASCC) are discussed.« less

Crystal structure and equation of state of Fe-Si alloys at super-Earth core conditions

DOE PAGES

Wicks, June K.; Smith, Raymond F.; Fratanduono, Dayne E.; ...

2018-04-25

In this paper, the high-pressure behavior of Fe alloys governs the interior structure and dynamics of super-Earths, rocky extrasolar planets that could be as much as ten times more massive than Earth. In experiments reaching up to 1300 GPa, we combine laser-driven dynamic ramp compression with in situ X-ray diffraction to study the effect of composition on the crystal structure and density of Fe-Si alloys, a potential constituent of super-Earth cores. We find that Fe-7wt.%Si adopts the hexagonal close packed (hcp) structure over the measured pressure range, whereas Fe-15wt.%Si is observed in a body-centered cubic (bcc) structure. This study representsmore » the first experimental determination of the density and crystal structure of Fe-Si alloys at pressures corresponding to the center of a ~3 Earth-mass terrestrial planet. Our results allow for direct determination of the effects of light elements on core radius, density, and pressures for such planets.« less

Crystal structure and equation of state of Fe-Si alloys at super-Earth core conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wicks, June K.; Smith, Raymond F.; Fratanduono, Dayne E.

In this paper, the high-pressure behavior of Fe alloys governs the interior structure and dynamics of super-Earths, rocky extrasolar planets that could be as much as ten times more massive than Earth. In experiments reaching up to 1300 GPa, we combine laser-driven dynamic ramp compression with in situ X-ray diffraction to study the effect of composition on the crystal structure and density of Fe-Si alloys, a potential constituent of super-Earth cores. We find that Fe-7wt.%Si adopts the hexagonal close packed (hcp) structure over the measured pressure range, whereas Fe-15wt.%Si is observed in a body-centered cubic (bcc) structure. This study representsmore » the first experimental determination of the density and crystal structure of Fe-Si alloys at pressures corresponding to the center of a ~3 Earth-mass terrestrial planet. Our results allow for direct determination of the effects of light elements on core radius, density, and pressures for such planets.« less

Surface modification of Ti alloy by electro-explosive alloying and electron-beam treatment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gromov, Victor, E-mail: gromov@physics.sibsiu.ru; Kobzareva, Tatiana, E-mail: kobzarevatanya@mail.ru; Budovskikh, Evgeniy, E-mail: budovskih-ea@physics.sibsiu.ru

2016-01-15

By methods of modern physical metallurgy the analysis of structure phase states of titanium alloy VT6 is carried out after electric explosion alloying with boron carbide and subsequent irradiation by pulsed electron beam. The formation of an electro-explosive alloying zone of a thickness up to 50 µm, having a gradient structure, characterized by decrease in the concentration of carbon and boron with increasing distance to the treatable surface has been revealed. Subsequent electron-beam treatment of alloying zone leads to smoothing of the alloying area surface and is accompanied by the multilayer structure formation at the depth of 30 µm withmore » alternating layers with different alloying degrees having the structure of submicro - and nanoscale level.« less

A feasibility study of using biodegradable magnesium alloy in glaucoma drainage device

PubMed Central

Li, Xiang-Ji; Xie, Lin; Pan, Fu-Sheng; Wang, Yong; Liu, Hong; Tang, Yu-Rong; Hutnik, Cindy ML

2018-01-01

Technological advances in glaucoma have challenged the traditional treatment paradigm. Historically incisional surgery has been used in cases of advanced disease and/or uncontrolled intraocular pressures resistant to medical or laser interventions. More recently, perhaps due to advancements in imaging, surgery has been suggested to be beneficial earlier in the treatment paradigm. Despite these trends, surgical manipulation of the tissues and unpredictability of wound healing continue to result in surgical failure. Magnesium is an essential element for human body and plays a critically important role in maintaining the functional and structural integrity of several tissues, including the eye. Due to several of its advantageous properties such as non-toxicity, biodegradability, and high biological compatibility, magnesium alloy has attracted great attention as a novel biomaterial. Biodegradable cardiovascular stents made of magnesium alloy have already been introduced into clinical practice. The purpose of this review is to determine if bioabsorbable magnesium alloys can be utilized as a promising candidate for the development of a new generation of glaucoma surgical assistive devices. PMID:29376002

Experience of Application of EBW in Producing Welded VT41 Alloy Drums in the Design of an HPC in an Advanced Engine

NASA Astrophysics Data System (ADS)

Bykov, Yu. G.; Fomichev, E. O.; Kashapov, O. S.; Kyaramyan, K. A.

2017-12-01

The conditions of electron-beam welding (EBW) of ring samples made of a VT41 alloy are adjusted to produce large welded joints of this alloy for a high-pressure compressor (HPC) of an advanced engine. The problems of quality control of a welded joint, the level of residual stresses in the near-weld zone, the microstructure of the welded joint, and its properties are considered.

Structural and magnetic properties of FeCoC system obtained by mechanical alloying

NASA Astrophysics Data System (ADS)

Rincón Soler, A. I.; Rodríguez Jacobo, R. R.; Medina Barreto, M. H.; Cruz-Muñoz, B.

2017-11-01

Fe96-XCoXC4 (x = 0, 10, 20, 30, 40 at. %) alloys were obtained by mechanical alloying of Fe, C and Co powders using high-energy milling. The structural and magnetic properties of the alloy system were analyzed by X-ray diffraction, Scanning Electron Microscopy (SEM), Vibrating Sample Magnetometer (VSM) and Mössbauer Spectrometry at room temperature. The X-ray diffraction patterns showed a BCC-FeCoC structure phase for all samples, as well as a lattice parameter that slightly decreases with Co content. The saturation magnetization and coercive field were analyzed as a function of Co content. The Mössbauer spectra were fitted with a hyperfine magnetic field distribution showing the ferromagnetic behavior and the disordered character of the samples. The mean hyperfine magnetic field remained nearly constant (358 T) with Co content.

Microstructural and Mechanical Property Characterization of Shear Formed Aerospace Aluminum Alloys

NASA Technical Reports Server (NTRS)

Troeger, Lillianne P.; Domack, Marcia S.; Wagner, John A.

2000-01-01

Advanced manufacturing processes such as near-net-shape forming can reduce production costs and increase the reliability of launch vehicle and airframe structural components through the reduction of material scrap and part count and the minimization of joints. The current research is an investigation of the processing-microstructure-property relationships for shear formed cylinders of the Al-Cu-Li-Mg-Ag alloy 2195 for space applications and the Al-Cu-Mg-Ag alloy C415 for airframe applications. Cylinders which had undergone various amounts of shear-forming strain were studied to correlate the grain structure, texture, and mechanical properties developed during and after shear forming.

Advanced technology composite aircraft structures

NASA Technical Reports Server (NTRS)

Ilcewicz, Larry B.; Walker, Thomas H.

1991-01-01

Work performed during the 25th month on NAS1-18889, Advanced Technology Composite Aircraft Structures, is summarized. The main objective of this program is to develop an integrated technology and demonstrate a confidence level that permits the cost- and weight-effective use of advanced composite materials in primary structures of future aircraft with the emphasis on pressurized fuselages. The period from 1-31 May 1991 is covered.

Advanced powder metallurgy aluminum alloys via rapid solidification technology, phase 2

NASA Technical Reports Server (NTRS)

Ray, Ranjan; Jha, Sunil C.

1987-01-01

Marko's rapid solidification technology was applied to processing high strength aluminum alloys. Four classes of alloys, namely, Al-Li based (class 1), 2124 type (class 2), high temperature Al-Fe-Mo (class 3), and PM X7091 type (class 4) alloy, were produced as melt-spun ribbons. The ribbons were pulverized, cold compacted, hot-degassed, and consolidated through single or double stage extrusion. The mechanical properties of all four classes of alloys were measured at room and elevated temperatures and their microstructures were investigated optically and through electron microscopy. The microstructure of class 1 Al-Li-Mg alloy was predominantly unrecrystallized due to Zr addition. Yield strengths to the order of 50 Ksi were obtained, but tensile elongation in most cases remained below 2 percent. The class 2 alloys were modified composition of 2124 aluminum alloy, through addition of 0.6 weight percent Zr and 1 weight percent Ni. Nickel addition gave rise to a fine dispersion of intermetallic particles resisting coarsening during elevated temperature exposure. The class 2 alloy showed good combination of tensile strength and ductility and retained high strength after 1000 hour exposure at 177 C. The class 3 Al-Fe-Mo alloy showed high strength and good ductility both at room and high temperatures. The yield and tensile strength of class 4 alloy exceeded those of the commercial 7075 aluminum alloy.

Nanostructured Fe-Cr Alloys for Advanced Nuclear Energy Applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Scattergood, Ronald O.

2016-04-26

We have completed research on the grain-size stabilization of model nanostructured Fe14Cr base alloys at high temperatures by the addition of non-equilibrium solutes. Fe14Cr base alloys are representative for nuclear reactor applications. The neutron flux in a nuclear reactor will generate He atoms that coalesce to form He bubbles. These can lead to premature failure of the reactor components, limiting their lifetime and increasing the cost and capacity for power generation. In order to mitigate such failures, Fe14Cr base alloys have been processed to contain very small nano-size oxide particles (less than 10 nm in size) that trap He atomsmore » and reduce bubble formation. Theoretical and experimental results indicate that the grain boundaries can also be very effective traps for He atoms and bubble formation. An optimum grain size will be less than 100 nm, ie., nanocrystalline alloys must be used. Powder metallurgy methods based on high-energy ball milling can produce Fe-Cr base nanocrystalline alloys that are suitable for nuclear energy applications. The problem with nanocrystalline alloys is that excess grain-boundary energy will cause grains to grow at higher temperatures and their propensity for He trapping will be lost. The nano-size oxide particles in current generation nuclear alloys provide some grain size stabilization by reducing grain-boundary mobility (Zener pinning – a kinetic effect). However the current mitigation strategy minimizing bubble formation is based primarily on He trapping by nano-size oxide particles. An alternate approach to nanoscale grain size stabilization has been proposed. This is based on the addition of small amounts of atoms that are large compared to the base alloy. At higher temperatures these will diffuse to the grain boundaries and will produce an equilibrium state for the grain size at higher temperatures (thermodynamic stabilization – an equilibrium effect). This would be preferred compared to a kinetic effect

Creep-Rupture Behavior of Ni-Based Alloy Tube Bends for A-USC Boilers

NASA Astrophysics Data System (ADS)

Shingledecker, John

Advanced ultrasupercritical (A-USC) boiler designs will require the use of nickel-based alloys for superheaters and reheaters and thus tube bending will be required. The American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code Section II PG-19 limits the amount of cold-strain for boiler tube bends for austenitic materials. In this summary and analysis of research conducted to date, a number of candidate nickel-based A-USC alloys were evaluated. These alloys include alloy 230, alloy 617, and Inconel 740/740H. Uniaxial creep and novel structural tests and corresponding post-test analysis, which included physical measurements, simplified analytical analysis, and detailed microscopy, showed that different damage mechanisms may operate based on test conditions, alloy, and cold-strain levels. Overall, creep strength and ductility were reduced in all the alloys, but the degree of degradation varied substantially. The results support the current cold-strain limits now incorporated in ASME for these alloys for long-term A-USC boiler service.

Characterization of Tubing from Advanced ODS alloy (FCRD-NFA1)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maloy, Stuart Andrew; Aydogan, Eda; Anderoglu, Osman

2016-09-20

Fabrication methods are being developed and tested for producing fuel clad tubing of the advanced ODS 14YWT and FCRD-NFA1 ferritic alloys. Three fabrication methods were based on plastically deforming a machined thick-wall tube sample of the ODS alloys by pilgering, hydrostatic extrusion or drawing to decrease the outer diameter and wall thickness and increase the length of the final tube. The fourth fabrication method consisted of the additive manufacturing approach involving solid-state spray deposition (SSSD) of ball milled and annealed powder of 14YWT for producing thin-wall tubes. Of the four fabrication methods, two methods were successful at producing tubing formore » further characterization: production of tubing by high-velocity oxy-fuel spray forming and production of tubing using high-temperature hydrostatic extrusion. The characterization described shows through neutron diffraction the texture produced during extrusion while maintaining the beneficial oxide dispersion. In this research, the parameters for innovative thermal spray deposition and hot extrusion processing methods have been developed to produce the final nanostructured ferritic alloy (NFA) tubes having approximately 0.5 mm wall thickness. Effect of different processing routes on texture and grain boundary characteristics has been investigated. It was found that hydrostatic extrusion results in combination of plane strain and shear deformations which generate rolling textures of α- and γ-fibers on {001}<110> and {111}<110> together with a shear texture of ζ-fiber on {011}<211> and {011}<011>. On the other hand, multi-step plane strain deformation in cross directions leads to a strong rolling textures of θ- and ε-fiber on {001}<110> together with weak γ-fiber on {111}<112>. Even though the amount of the equivalent strain is similar, shear deformation leads to much lower texture indexes compared to the plane strain deformations. Moreover, while 50% of hot rolling brings about a large

Thermodynamics of Alloys: Studies of Nickel-Gallium, Nickel-Germanium and Nickel-Rhodium Alloys.

DTIC Science & Technology

NICKEL ALLOYS, *GALLIUM ALLOYS, *GERMANIUM ALLOYS, * RHODIUM ALLOYS, *PHASE STUDIES, THERMODYNAMICS, INTERMETALLIC COMPOUNDS, FREE ENERGY, ENTROPY, HEAT OF FORMATION, CRYSTAL STRUCTURE, UNITED KINGDOM.

Predicting the Crystal Structure and Phase Transitions in High-Entropy Alloys

NASA Astrophysics Data System (ADS)

King, D. M.; Middleburgh, S. C.; Edwards, L.; Lumpkin, G. R.; Cortie, M.

2015-06-01

High-entropy alloys (HEAs) have advantageous properties compared with other systems as a result of their chemistry and crystal structure. The transition between a face-centered cubic (FCC) and body-centered cubic (BCC) structure in the Al x CoCrFeNi high-entropy alloy system has been investigated on the atomic scale in this work. The Al x CoCrFeNi system, as well as being a useful system itself, can also be considered a model HEA material. Ordering in the FCC structure was investigated, and an order-disorder transition was predicted at ~600 K. It was found that, at low temperatures, an ordered lattice is favored over a truly random lattice. The fully disordered BCC structure was found to be unstable. When partial ordering was imposed (lowering the symmetry), with Al and Ni limited specific sites of the BCC system, the BCC packing was stabilized. Decomposition of the ordered BCC single phase into a dual phase (Al-Ni rich and Fe-Cr rich) is also considered.

The structure-property relationships of powder processed Fe-Al-Si alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prichard, Paul D.

1998-02-23

Iron-aluminum alloys have been extensively evaluated as semi-continuous product such as sheet and bar, but have not been evaluated by net shape P/M processing techniques such as metal injection molding. The alloy compositions of iron-aluminum alloys have been optimized for room temperature ductility, but have limited high temperature strength. Hot extruded powder alloys in the Fe-Al-Si system have developed impressive mechanical properties, but the effects of sintering on mechanical properties have not been explored. This investigation evaluated three powder processed Fe-Al-Si alloys: Fe-15Al, Fe-15Al-2.8Si, Fe-15Al-5Si (atomic %). The powder alloys were produced with a high pressure gas atomization (HPGA) processmore » to obtain a high fraction of metal injection molding (MIM) quality powder (D 84 < 32 μm). The powders were consolidated either by P/M hot extrusion or by vacuum sintering. The extruded materials were near full density with grain sizes ranging from 30 to 50 μm. The vacuum sintering conditions produced samples with density ranging from 87% to 99% of theoretical density, with an average grain size ranging from 26 μm to 104 μm. Mechanical property testing was conducted on both extruded and sintered material using a small punch test. Tensile tests were conducted on extruded bar for comparison with the punch test data. Punch tests were conducted from 25 to 550 C to determine the yield strength, and fracture energy for each alloy as a function of processing condition. The ductile to brittle transition temperature (DBTT) was observed to increase with an increasing silicon content. The Fe-15Al-2.8Si alloy was selected for more extensive testing due to the combination of high temperature strength and low temperature toughness due to the two phase α + DO 3 structure. This investigation provided a framework for understanding the effects of silicon in powder processing and mechanical property behavior of Fe-Al-Si alloys.« less

Structure and Mechanical and Corrosion Properties of a Magnesium Mg-Y-Nd-Zr Alloy after High Pressure Torsion

NASA Astrophysics Data System (ADS)

Lukyanova, E. A.; Martynenko, N. S.; Serebryany, V. N.; Belyakov, A. N.; Rokhlin, L. L.; Dobatkin, S. V.; Estrin, Yu. Z.

2017-11-01

The structure and the properties of an Mg-Y-Nd-Zr alloy (WE43) are studied after high pressure torsion (HPT) in the temperature range 20-300°C. Structure refinement proceeds mainly by deformation twinning with the formation of a partial nanocrystalline structure with a grain size of 30-100 nm inside deformation twins. The WE43 alloy is shown to be aged during heating after HPT due to the decomposition of a magnesium solid solution. HPT at room temperature and subsequent aging causes maximum hardening. It is shown that HPT significantly accelerates the decomposition of a magnesium solid solution. HPT at all temperatures considerably increases the tensile strength and the yield strength upon tensile tests and significantly decreases plasticity. Subsequent aging additionally hardens the WE43 alloy. A potentiodynamic study shows that the corrosion resistance of this alloy after HPT increases. However, subsequent aging degrades the corrosion properties of the alloy.

Bone bonding strength of diamond-structured porous titanium-alloy implants manufactured using the electron beam-melting technique.

PubMed

Hara, Daisuke; Nakashima, Yasuharu; Sato, Taishi; Hirata, Masanobu; Kanazawa, Masayuki; Kohno, Yusuke; Yoshimoto, Kensei; Yoshihara, Yusuke; Nakamura, Akihiro; Nakao, Yumiko; Iwamoto, Yukihide

2016-02-01

The present study examined the bone bonding strength of diamond-structured porous titanium-alloy (Porous-Ti-alloy) manufactured using the electron beam-melting technique in comparison with fiber mesh-coated or rough-surfaced implants. Cylindrical implants with four different pore sizes (500, 640, 800, and 1000μm) of Porous-Ti-alloy, titanium fiber mesh (FM), and surfaces roughened by titanium arc spray (Ti-spray) were implanted into the distal femur of rabbits. Bone bonding strength and histological bone ingrowth were evaluated at 4 and 12weeks after implantation. The bone bonding strength of Porous-Ti-alloy implants (640μm pore size) increased over time from 541.4N at 4weeks to 704.6N at 12weeks and was comparable to that of FM and Ti-spray implants at both weeks. No breakage of the porous structure after mechanical testing was found with Porous-Ti-alloy implants. Histological bone ingrowth that increased with implantation time occurred along the inner structure of Porous-Ti-alloy implants. There was no difference in bone ingrowth in Porous-Ti-alloy implants with pore sizes among 500, 640, and 800μm; however, less bone ingrowth was observed with the 1000μm pore size. These results indicated Porous-Ti-alloy implants with pore size under 800μm provided biologically active and mechanically stable surface for implant fixation to bone, and had potential advantages for weight bearing orthopedic implants such as acetabular cups. Copyright © 2015 Elsevier B.V. All rights reserved.

Local structure of high-coercivity Fe-Ni-Al alloys

NASA Astrophysics Data System (ADS)

Menushenkov, A. P.; Menushenkov, V. P.; Chernikov, R. V.; Sviridova, T. A.; Grishina, O. V.; Sidorov, V. V.

2011-04-01

Results of hard magnetic Fe-Ni-Al alloys after various thermal processing local structure researches by method of EXAFS-spectroscopy with use of synchrotron radiation at temperature 77 K are presented. It is established, that during cooling a firm solution with critical speed reorganization of a local environment of nickel relative to quickly tempered sample owing to stratification of a firm solution is observed. The subsequent aging at 780°C practically restores local structure, characteristic for quickly tempered sample, keeping thus rather high coercitive force.

Magnetic x-ray linear dichroism of ultrathin Fe-Ni alloy films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schumann, F.O.; Willis, R.F.; Goodman, K.W.

1997-04-01

The authors have studied the magnetic structure of ultrathin Fe-Ni alloy films as a function of Fe concentration by measuring the linear dichroism of the 3p-core levels in angle-resolved photoemission spectroscopy. The alloy films, grown by molecular-beam epitaxy on Cu(001) surfaces, were fcc and approximately four monolayers thick. The intensity of the Fe dichroism varied with Fe concentration, with larger dichroisms at lower Fe concentrations. The implication of these results to an ultrathin film analogue of the bulk Invar effect in Fe-Ni alloys will be discussed. These measurements were performed at the Spectromicroscopy Facility (Beamline 7.0.1) of the Advanced Lightmore » Source.« less

Controlling diffusion for a self-healing radiation tolerant nanostructured ferritic alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miller, Michael K.; Parish, Chad M.; Bei, Hongbin

Diffusion plays a major role in the stability of microstructures to extreme conditions of high temperature and high doses of irradiation. In nanostructured ferritic alloys, first principle calculations indicate that the binding energy of vacancies is reduced by the presence of oxygen, titanium and yttrium atoms. Therefore, the number of free vacancies available for diffusion can be greatly reduced. The mechanical properties of these alloys, compared to traditional wrought alloys of similar composition and grain structure, is distinctly different, and the ultrafine grained alloy is distinguished by a high number density of Ti–Y–O-enriched nanoclusters and solute clusters, which drives themore » mechanical response. When a displacement cascade interacts with a nanocluster, the solute atoms are locally dispersed into the matrix by ballistic collisions, but immediately a new nanocluster reforms due to the local supersaturation of solutes and vacancies until the excess vacancies are consumed. Furthermore, the result of these processes is a structural material for advanced energy systems with a microstructure that is self-healing and tolerant to high doses of radiation and high temperatures.« less

Controlling diffusion for a self-healing radiation tolerant nanostructured ferritic alloy

DOE PAGES

Miller, Michael K.; Parish, Chad M.; Bei, Hongbin

2014-12-18

Diffusion plays a major role in the stability of microstructures to extreme conditions of high temperature and high doses of irradiation. In nanostructured ferritic alloys, first principle calculations indicate that the binding energy of vacancies is reduced by the presence of oxygen, titanium and yttrium atoms. Therefore, the number of free vacancies available for diffusion can be greatly reduced. The mechanical properties of these alloys, compared to traditional wrought alloys of similar composition and grain structure, is distinctly different, and the ultrafine grained alloy is distinguished by a high number density of Ti–Y–O-enriched nanoclusters and solute clusters, which drives themore » mechanical response. When a displacement cascade interacts with a nanocluster, the solute atoms are locally dispersed into the matrix by ballistic collisions, but immediately a new nanocluster reforms due to the local supersaturation of solutes and vacancies until the excess vacancies are consumed. Furthermore, the result of these processes is a structural material for advanced energy systems with a microstructure that is self-healing and tolerant to high doses of radiation and high temperatures.« less

Controlling diffusion for a self-healing radiation tolerant nanostructured ferritic alloy

NASA Astrophysics Data System (ADS)

Miller, M. K.; Parish, C. M.; Bei, H.

2015-07-01

Diffusion plays a major role in the stability of microstructures to extreme conditions of high temperature and high doses of irradiation. In nanostructured ferritic alloys, first principle calculations indicate that the binding energy of vacancies is reduced by the presence of oxygen, titanium and yttrium atoms. Therefore, the number of free vacancies available for diffusion can be greatly reduced. The mechanical properties of these alloys, compared to traditional wrought alloys of similar composition and grain structure, is distinctly different, and the ultrafine grained alloy is distinguished by a high number density of Ti-Y-O-enriched nanoclusters and solute clusters, which drives the mechanical response. When a displacement cascade interacts with a nanocluster, the solute atoms are locally dispersed into the matrix by ballistic collisions, but immediately a new nanocluster reforms due to the local supersaturation of solutes and vacancies until the excess vacancies are consumed. The result of these processes is a structural material for advanced energy systems with a microstructure that is self-healing and tolerant to high doses of radiation and high temperatures.

Advanced composite structural concepts and material technologies for primary aircraft structures

NASA Technical Reports Server (NTRS)

Jackson, Anthony

1991-01-01

Structural weight savings using advanced composites have been demonstrated for many years. Most military aircraft today use these materials extensively and Europe has taken the lead in their use in commercial aircraft primary structures. A major inhibiter to the use of advanced composites in the United States is cost. Material costs are high and will remain high relative to aluminum. The key therefore lies in the significant reduction in fabrication and assembly costs. The largest cost in most structures today is assembly. As part of the NASA Advanced Composite Technology Program, Lockheed Aeronautical Systems Company has a contract to explore and develop advanced structural and manufacturing concepts using advanced composites for transport aircraft. Wing and fuselage concepts and related trade studies are discussed. These concepts are intended to lower cost and weight through the use of innovative material forms, processes, structural configurations and minimization of parts. The approach to the trade studies and the downselect to the primary wing and fuselage concepts is detailed. The expectations for the development of these concepts is reviewed.

Advanced powder metallurgy aluminum alloys via rapid solidification technology

NASA Technical Reports Server (NTRS)

Ray, R.

1984-01-01

Aluminum alloys containing 10 to 11.5 wt. pct. of iron and 1.5 to 3 wt. pct. of chromium using the technique of rapid solidification powder metallurgy were studied. Alloys were prepared as thin ribbons (.002 inch thick) rapidly solidified at uniform rate of 10(6) C/second by the melt spinning process. The melt spun ribbons were pulverized into powders (-60 to 400 mesh) by a rotating hammer mill. The powders were consolidated by hot extrusion at a high reduction ratio of 50:1. The powder extrusion temperature was varied to determine the range of desirable processing conditions necessary to yield useful properties. Powders and consolidated alloys were characterized by SEM and optical metallography. The consolidated alloys were evaluated for (1) thermal stability, (2) tensile properties in the range, room temperature to 450 F, and (3) notch toughness in the range, room temperature to 450 F.

Structure and mechanical characterization of Mg-Nd-Zn alloys prepared by different processes

NASA Astrophysics Data System (ADS)

Dvorský, D.; Kubásek, J.; Vojtěch, D.; Voňavková, I.; Veselý, M.; Čavojský, M.

2017-02-01

Magnesium alloys containing about 3 wt. % of Nd and 0.5 wt. % of Zn are considered as promising materials for application in transport and medical industry. Properly treated materials can reach ultimate tensile strength (UTS) higher than 300 MPa. Also the corrosion resistance of these alloys is superior to many other magnesium-based materials. Present work is focused on the preparation of Mg-3Nd-0.5Zn magnesium alloy by classical casting and subsequent thermal treatment. As-cast material was extruded at 400 °C, with extrusion ratio equal to 16 and velocity of 0.2 mm/s. The effect of thermal treatment and also strong plastic deformation during extrusion on final structure conditions and mechanical properties is specified. Present results confirm significant improvement of tensile yield strength (TYS) and UTS after extrusion process as a consequence of fine-grained structure combined with precipitation strengthening. Beside, texture strengthening in the direction parallel to the extrusion has been observed too.

Electrochemical alloying of immiscible Ag and Co for their structural and magnetic analyses

NASA Astrophysics Data System (ADS)

Santhi, Kalavathy; Kumarsan, Dhanapal; Vengidusamy, Naryanan; Arumainathan, Stephen

2017-07-01

Electrochemical alloying of immiscible Ag and Co was carried out at different current densities from electrolytes of two different concentrations, after optimizing the electrolytic bath and operating conditions. The samples obtained were characterized using X-ray diffraction to confirm the simultaneous deposition of Ag and Co and to determine their crystallographic structure. The atomic percentage of Ag and Co contents in the granular alloy was determined by ICP-OES analysis. The XPS spectra were observed to confirm the presence of Ag and Co in the metallic form in the granular alloy samples. The micrographs observed using scanning and transmission electron microscopes threw light on the surface morphology and the size of the particles. The magnetic nature of the samples was analyzed at room temperature by a vibration sample magnetometer. Their magnetic phase transition while heating was also studied to provide further evidence for the magnetic behaviour and the structure of the deposits.

PLUTONIUM-ZIRCONIUM ALLOYS

DOEpatents

Schonfeld, F.W.; Waber, J.T.

1960-08-30

A series of nuclear reactor fuel alloys consisting of from about 5 to about 50 at.% zirconium (or higher zirconium alloys such as Zircaloy), balance plutonium, and having the structural composition of a plutonium are described. Zirconium is a satisfactory diluent because it alloys readily with plutonium and has desirable nuclear properties. Additional advantages are corrosion resistance, excellent fabrication propenties, an isotropie structure, and initial softness.

Recent Advances in Nanostructured Thermoelectric Half-Heusler Compounds

PubMed Central

Xie, Wenjie; Weidenkaff, Anke; Tang, Xinfeng; Zhang, Qingjie; Poon, Joseph; Tritt, Terry M.

2012-01-01

Half-Heusler (HH) alloys have attracted considerable interest as promising thermoelectric (TE) materials in the temperature range around 700 K and above, which is close to the temperature range of most industrial waste heat sources. The past few years have seen nanostructuing play an important role in significantly enhancing the TE performance of several HH alloys. In this article, we briefly review the recent progress and advances in these HH nanocomposites. We begin by presenting the structure of HH alloys and the different strategies that have been utilized for improving the TE properties of HH alloys. Next, we review the details of HH nanocomposites as obtained by different techniques. Finally, the review closes by highlighting several promising strategies for further research directions in these very promising TE materials. PMID:28348315

Formation of Gradient Structures in the Zone of Joining a Deformable Nickel Alloy and a Single-Crystal Intermetallic Alloy during Thermodiffusion Pressure Welding and Subsequent Heat Treatment

NASA Astrophysics Data System (ADS)

Povarova, K. B.; Valitov, V. A.; Drozdov, A. A.; Bazyleva, O. A.; Galieva, E. V.; Arginbaeva, E. G.

2018-01-01

The possibility of formation of a high-quality solid-phase joint of an Ni3Al-based single-crystal intermetallic VKNA-25 blade alloy with a high-temperature deformable EP975 disk alloy by pressure welding is studied to create high-performance one-piece blisk unit for the next-generation aviation gas turbine engines and to decrease the unit mass. The influence of the conditions of thermodiffusion pressure welding under the hightemperature superplasticity of the disk alloy and the influence of heat treatment of welded joints on the gradient structures in the welded joint zone and the structure at the periphery of the welded samples are investigated.

Process-Structure-Property Relationship in Magnesium-Based Biodegradable Alloy for Biomedical Applications

NASA Astrophysics Data System (ADS)

Trivedi, Pramanshu

Magnesium alloys are considered to be the next generation of biomaterials because of their ability to degrade in the physiological environment. We elucidate here the impact of multiaxial forging of Mg-2Zn-2Gd alloy on grain refinement to sub-micron regime and relate the structure to mechanical properties and biological functionality. As-cast and annealed samples were multiaxial forged (MAF) for a total number of two passes with a true strain of 2/pass. Considering that the microstructure governs the biological response of materials, we studied the constituents of the microstructure in conjunction with the mechanical behavior. The antimicrobial behavior in a Mg-2Zn-2Gd alloy with different grain size in the range of 44 microm to 710 nm was studied by seeding. Surface energy and contact angle measurements using goniometer and wettability were assessed with water, SBF, n-Hexane, and DMEM. The structure-property relationship in Mg-2Zn-2Gd alloy to maintaining mechanical integrity during degradation was studied by seeding Escherichia coli ( E. coli). Furthermore, we studied the effect of degradation behavior in the presence and absence of cells. This was followed by the study of bioactivity in terms of phases present on the surface and degradation products in simulated body fluid (SBF). Magnesium coated with apatite using a biomimetic approach were placed in a 24-well culture plate with alpha-MEM media and the degradation behavior was studied in the absence and presence of cells (seeding density: 10,000 cells/cm2). The change in pH was monitored at regular intervals. Cell attachment was studied by seeding the cells for 4h and cell viability was studied by seeding the cells for up to 1, 3, and 7 days. The study underscores that the fine-grained alloys exhibited superior mechanical properties, antimicrobial resistance, and cell attachment. The degradation rate was also least for fine-grained alloy. The higher surface energy of ultrafine-grained Mg-2Zn-2Gd alloy led to the

Mechanical Alloying of W-Mo-V-Cr-Ta High Entropy Alloys

NASA Astrophysics Data System (ADS)

Das, Sujit; Robi, P. S.

2018-04-01

Recent years have seen the emergence of high-entropy alloys (HEAs) consisting of five or more elements in equi-atomic or near equi-atomic ratios. These alloys in single phase solid solution exhibit exceptional mechanical properties viz., high strength at room and elevated temperatures, reasonable ductility and stable microstructure over a wide range of temperatures making it suitable for high temperature structural materials. In spite of the attractive properties, processing of these materials remains a challenge. Reports regarding fabrication and characterisation of a few refractory HEA systems are available. The processing of these alloys have been carried out by arc melting of small button sized materials. The present paper discusses the development of a novel refractory W-Mo-V-Cr-Ta HEA powder based on a new alloy design concept. The powder mixture was milled for time periods up to 64 hours. Single phase alloy powder having body centred cubic structure was processed by mechanical alloying. The milling characteristics and extent of alloying during the ball milling were characterized using X-ray diffractiometre (XRD), field emission scanning electron microscope (FESEM) and transmission electron microscope (TEM). A single phase solid solution alloy powder having body-centred cubic (BCC) structure with a lattice parameter of 3.15486 Å was obtained after milling for 32 hours.

Structural and magnetic properties of FexNi100-x alloys synthesized using Al as a reducing metal

NASA Astrophysics Data System (ADS)

Srakaew, N.; Jantaratana, P.; Nipakul, P.; Sirisathitkul, C.

2017-08-01

Iron-nickel (Fe-Ni) alloys comprising nine different compositions were rapidly synthesized from the redox reaction using aluminum foils as the reducing metal. Compared with conventional chemical syntheses, this simple approach is relatively safe and allows control over the alloy morphology and magnetic behavior as a function of the alloy composition with minimal oxidation. For alloys having low (10%-30%) Fe content the single face-centered cubic (FCC) FeNi3 phase was formed with nanorods aligned in the (1 1 1) crystalline direction on the cluster surface. This highly anisotropic morphology gradually disappeared as the Fe content was raised to 40%-70% with the alloy structure possessing a mixture of FCC FeNi3 and body-centered cubic (BCC) Fe7Ni3. The FCC phase was entirely replaced by the BCC structure upon further increase the Fe content to 80%-90%. The substitution of Ni by Fe in the crystals and the dominance of the BCC phase over the FCC structure gave rise to enhanced magnetization. By contrast, the coercive field decreased as a function of increasing Fe because of the reduction in shape anisotropy and the rise of saturation magnetization.

Structure and soft magnetic properties of Fe-Si-B-P-Cu nanocrystalline alloys with minor Mn addition

NASA Astrophysics Data System (ADS)

Jia, Xingjie; Li, Yanhui; Wu, Licheng; Zhang, Wei

2018-05-01

Addition of minor Mn effectively improves the amorphous-forming ability and thermal stability of the Fe85Si2B8P4Cu1 alloy. With increasing the Mn content from 0 to 3 at.%, the critical thickness for amorphous formation and onset temperature of the primary crystallization increase from 14 μm and 659 K to 27 μm and 668 K, respectively. The fine nanocrystalline structure with α-Fe grains in size (D) of < 20 nm was obtained for the annealed amorphous alloys, which show excellent soft magnetic properties. The alloying of Mn reduces the coercivity (Hc) by decreasing the D value and widens the optimum annealing temperature range for obtaining low Hc, although the saturation magnetic flux density (Bs) is decreased slightly. The Fe83Mn2Si2B8P4Cu1 nanocrystalline alloy possesses fine structure with a D of ˜17.5 nm, and exhibits a high Bs of ˜1.75 T and a low Hc of ˜5.9 A/m. The mechanism related to the alloying effects on the structure and magnetic properties was discussed in term of the crystallization activation energy.

Synthesis, structure stability and magnetic properties of nanocrystalline Ag-Ni alloy

NASA Astrophysics Data System (ADS)

Santhi, Kalavathy; Thirumal, E.; Karthick, S. N.; Kim, Hee-Je; Nidhin, Marimuthu; Narayanan, V.; Stephen, A.

2012-05-01

Silver-nickel alloy nanoparticles with an average size of 30-40 nm were synthesized by chemically reducing the mixture of silver and nickel salts using sodium borohydride. The structure and the magnetic properties of the alloy samples with different compositions were investigated. The phase stability of the material was analysed after annealing the sample in vacuum at various temperatures. The material exhibits single fcc phase which is stable up to 400 °C and Ni precipitation sets in when the sample is annealed to 500 °C. The thermal analysis using DSC was carried out to confirm the same. The alloy compositions are found to be in close correlation with the metal salt ratios in the precursors. The synthesized samples exhibit weak paramagnetic to ferromagnetic behaviour. The magnetic measurements reveal that by adjusting the precursor ratio, the Ni content in the material can be altered and hence its magnetic properties tailored to suit specific requirements. The formation of Ag-Ni alloy is confirmed by the observed Curie temperature from the magneto thermogram. Annealing the sample helps to produce significant enhancement in the magnetization of the material.

Growth and structural evolution of Sn on Ag(001): Epitaxial monolayer to thick alloy film

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chakraborty, Suvankar; Menon, Krishnakumar S. R., E-mail: krishna.menon@saha.ac.in

The growth and structure of Sn on Ag(001), from submonolayer to thick film coverages at room temperature, are studied using low energy electron diffraction, x-ray photoemission spectroscopy and angle-resolved photoemission spectroscopy (ARPES) techniques. The authors observe different growth modes for submonolayer Sn coverages and for higher Sn coverages. Systematic surface structural evolution, consistent with the substitution of surface Ag atoms by Sn atoms, is observed for submonolayer Sn coverages while an ordered Ag-Sn bulk alloy film is formed for higher Sn coverages with an Ag overlayer. For monolayer coverage of Sn, a pseudomorphic growth of a Sn layer without alloyingmore » is determined. ARPES results also confirm the presence of an ordered Ag overlayer on the bulk Ag-Sn alloy film, suggesting the formation of an Ag/Ag{sub 3}Sn/Ag(001) sandwich structure at the surface for higher Sn coverages. The present results illustrate the complex interplay of atomic mobilities, surface free-energies, and alloy formation energies in determining the growth and structural properties of the system.« less

Electronic structure and magnetic properties of disordered Co{sub 2}FeAl Heusler alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jain, Vishal, E-mail: vjain045@gmail.com; Jain, Vivek, E-mail: vjain045@gmail.com; Sudheesh, V. D., E-mail: vjain045@gmail.com

The effects of disorder on the magnetic properties of Co{sub 2}FeAl alloy are reported. X-ray diffraction exhibit A2-type disordered structure. Room temperature Mössbauer studies show the presence of two sextets with hyperfine field values of 31T and 30T along with a nonmagnetic singlet. The electronic structure of ordered and disordered Co{sub 2}FeAl alloys, investigated by means of the KKR Green's-function method shows that the magnetic moment of the ordered structure is 5.08μ{sub B} and is 5.10μ{sub B} when disordered. However, a much higher magnetic moment of 5.74μ{sub B} is observed experimentally.

Theoretical investigation of the structural, electronic, and thermodynamic properties of CdS1-xSex alloys

NASA Astrophysics Data System (ADS)

Long, Debing; Li, Mingkai; Meng, Dongxue; Ahuja, Rajeev; He, Yunbin

2018-03-01

In this work, the structural, electronic, and thermodynamic properties of wurtzite (WZ) and zincblende (ZB) CdS1-xSex alloys are investigated using the density functional theory (DFT) and the cluster expansion method. A special quasirandom structure containing 16 atoms is constructed to calculate the band structures of random alloys. The band gaps of CdS1-xSex alloys are direct and decrease as the Se content increases. The delta self-consistent-field method is applied to correct band gaps that are underestimated by DFT. The band offsets clearly reflect the variation in valence band maxima and conduction band minima, thus providing information useful to the design of relevant quantum well structures. The positive formation enthalpies of both phases imply that CdS1-xSex is an immiscible system and tends to phase separate. The influence of lattice vibrations on the phase diagram is investigated by calculating the phonon density of states. Lattice vibration effects can reduce the critical temperature Tc and increase alloy solid solubilities. This influence is especially significant in the ZB structure. When only chemical interactions are present, the Tc values for WZ- and ZB-CdS1-xSex are 260 K and 249 K, respectively. The lattice vibration enthalpy and entropy lower the Tc to 255 K and 233 K, respectively.

How closely do many-body potentials describe the structure and dynamics of Cu-Zr glass-forming alloy?

NASA Astrophysics Data System (ADS)

Lad, K. N.; Jakse, N.; Pasturel, A.

2017-03-01

Molecular dynamics investigations of the structure and dynamics of Cu64.5Zr35.5 metallic glass-forming alloy have been carried out using five different semi-empirical, many-body interaction potentials based on the Finnis-Sinclair model [M. I. Mendelev et al., J. Appl. Phys. 102, 043501 (2007) (MSK); M. I. Mendelev et al., Philos. Mag. 89, 967 (2009) (MKOSYP); L. Ward et al., e-print arXiv:1209.0619 (2012) (WAFW)] and the embedded-atom model [Y. Q. Cheng et al., Phys. Rev. Lett. 102, 245501 (2009) (CMS) and N. Jakse et al., Phys. Rev. B 85, 174201 (2012) (JNP)]. Although the total static structure factor of the alloy for all the five interaction potentials is, in general, found to be in good agreement with the experimental results, the investigation of a local structure in terms of icosahedral short-range order reveals that the effect of the interaction potential (especially the cohesive part) on the structure of the alloy is not as trivial as it seems. For MSK and JNP potentials, the self-intermediate scattering function Fs(q, t), q-dependence of the structural relaxation time τα in the low-q region, and the self-diffusion coefficient, Ds, for Cu-atoms in the alloy are in excellent agreement with the experimental results. The results for MKOSYP, CMS, and WAFW potentials deviate significantly from the experiment and suggest the dynamics of the alloy to be faster. The difference in the description of the dynamics of the alloy by different potentials is found to be due to the difference in the relevant energy scales corresponding to the temperature scales. τα and Ds exhibit Arrhenius temperature dependence in the high temperature regime above the melting temperature. We also suggest that the attractive forces influence the dynamics of the liquid alloy significantly, which is against the mere perturbative role assigned to the attractive forces in the van der Waals picture of liquids that has been challenged in the recent years. As the five interaction potentials

Research and Development of High-Strength of Al-Zn-Mg-Cu Alloys

NASA Astrophysics Data System (ADS)

Vakhromov, R. O.; Antipov, V. V.; Tkachenko, E. A.

The paper is focused on high-strength alloys (UTS=600-650 MPa, specific strength (UTS/density) 220-230 kN•m/kg) which will allow one to retain aluminum's predominant position during the next 15-20 years as applied in advanced aircraft primary structures. Parameters of microstructure (dispersoids, precipitates, degree of recrystallisation, grain size) and properties of semiproducts were studied in dependence on content of base alloying elements in chemical compositions of alloys (total sum of Zn+Mg+Cu — higher than 10 % mass). Contribution of minor additions (Zr, Sc, Ag) to strengthening and creation of improved combination of service properties was investigated. Evolution of phase composition and properties was studied as a dependence of different aging treatments.

Nickel-aluminum alloy clusters -- structural and dynamical properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jellinek, J.; Krissinel, E.B.

1997-08-01

Structural and dynamical properties of mixed Ni{sub n}Al{sub m} alloy clusters mimicked by a many-body potential are studied computationally for all the possible compositions n and m such that n + m = 13. It is shown that the manifold of the usually very large number of the different possible structural forms can be systematized by introducing classes of structures corresponding to the same concentration of the components, geometry and type of the central atom. General definitions of mixing energy and mixing coefficient are introduced, and it is shown that the energy ordering of the structural forms within each classmore » is governed by the mixing coefficient. The peculiarities of the solid-to-liquid-like transition are described as a function of the concentration of the two types of atoms. These peculiarities are correlated with and explained in terms of the energy spectra of the structural forms. Class-dependent features of the dynamics are described and analyzed.« less

Atom redistribution and multilayer structure in NiTi shape memory alloy induced by high energy proton irradiation

NASA Astrophysics Data System (ADS)

Wang, Haizhen; Yi, Xiaoyang; Zhu, Yingying; Yin, Yongkui; Gao, Yuan; Cai, Wei; Gao, Zhiyong

2017-10-01

The element distribution and surface microstructure in NiTi shape memory alloys exposed to 3 MeV proton irradiation were investigated. Redistribution of the alloying element and a clearly visible multilayer structure consisting of three layers were observed on the surface of NiTi shape memory alloys after proton irradiation. The outermost layer consists primarily of a columnar-like TiH2 phase with a tetragonal structure, and the internal layer is primarily comprised of a bcc austenite phase. In addition, the Ti2Ni phase, with an fcc structure, serves as the transition layer between the outermost and internal layer. The above-mentioned phenomenon is attributed to the preferential sputtering of high energy protons and segregation induced by irradiation.

Effect of a microstructure and surface hydrogen alloying of a VT6 alloy on diffusion welding

NASA Astrophysics Data System (ADS)

Senkevich, K. S.; Skvortsova, S. V.; Kudelina, I. M.; Knyazev, M. I.; Zasypkin, V. V.

2014-01-01

The effect of a structural type (lamellar, fine, gradient) and additional surface alloying with hydrogen on the diffusion bonding of titanium alloy VT6 samples is studied. It is shown that the surface alloying of VT6 alloy parts with hydrogen allows one to decrease the diffusion welding temperature by 50-100°C, to obtain high-quality pore-free bonding, and to remove the "structural" boundary between materials to be welded that usually forms during welding of titanium alloys with a lamellar structure.

Semiconductor structures having electrically insulating and conducting portions formed from an AlSb-alloy layer

DOEpatents

Spahn, Olga B.; Lear, Kevin L.

1998-01-01

A semiconductor structure. The semiconductor structure comprises a plurality of semiconductor layers formed on a substrate including at least one layer of a III-V compound semiconductor alloy comprising aluminum (Al) and antimony (Sb), with at least a part of the AlSb-alloy layer being chemically converted by an oxidation process to form superposed electrically insulating and electrically conducting portions. The electrically insulating portion formed from the AlSb-alloy layer comprises an oxide of aluminum (e.g. Al.sub.2 O.sub.3), while the electrically conducting portion comprises Sb. A lateral oxidation process allows formation of the superposed insulating and conducting portions below monocrystalline semiconductor layers for forming many different types of semiconductor structures having particular utility for optoelectronic devices such as light-emitting diodes, edge-emitting lasers, vertical-cavity surface-emitting lasers, photodetectors and optical modulators (waveguide and surface normal), and for electronic devices such as heterojunction bipolar transistors, field-effect transistors and quantum-effect devices. The invention is expected to be particularly useful for forming light-emitting devices for use in the 1.3-1.6 .mu.m wavelength range, with the AlSb-alloy layer acting to define an active region of the device and to effectively channel an electrical current therein for efficient light generation.

Structural efficiencies of various aluminum, titanium, and steel alloys at elevated temperatures

NASA Technical Reports Server (NTRS)

Heimerl, George J; Hughes, Philip J

1953-01-01

Efficient temperature ranges are indicated for two high-strength aluminum alloys, two titanium alloys, and three steels for some short-time compression-loading applications at elevated temperatures. Only the effects of constant temperatures and short exposure to temperature are considered, and creep is assumed not to be a factor. The structural efficiency analysis is based upon preliminary results of short-time elevated-temperature compressive stress-strain tests of the materials. The analysis covers strength under uniaxial compression, elastic stiffness, column buckling, and the buckling of long plates in compression or in shear.

Atomistic simulation of cubic and tetragonal phases of U-Mo alloy: Structure and thermodynamic properties

NASA Astrophysics Data System (ADS)

Starikov, S. V.; Kolotova, L. N.; Kuksin, A. Yu.; Smirnova, D. E.; Tseplyaev, V. I.

2018-02-01

We studied structure and thermodynamic properties of cubic and tetragonal phases of pure uranium and U-Mo alloys using atomistic simulations: molecular dynamics and density functional theory. The main attention was paid to the metastable γ0 -phase that is formed in U-Mo alloys at low temperature. Structure of γ0 -phase is similar to body-centered tetragonal (bct) lattice with displacement of a central atom in the basic cell along [ 001 ] direction. Such displacements have opposite orientations for part of the neighbouring basic cells. In this case, such ordering of the displacements can be designated as antiferro-displacement. Formation of such complex structure may be interpreted through forming of short U-U bonds. At heating, the tetragonal structure transforms into cubic γs -phase, still showing ordering of central atom displacements. With rise in temperature, γs -phase transforms to γ-phase with a quasi body-centered cubic (q-bcc) lattice. The local positions of uranium atoms in γ-phase correspond to γs -phase, however, orientations of the central atom displacements become disordered. Transition from γ0 to γ can be considered as antiferro-to paraelastic transition of order-disorder type. This approach to the structure description of uranium alloy allows to explain a number of unusual features found in the experiments: anisotropy of lattice at low temperature; remarkably high self-diffusion mobility in γ-phase; decreasing of electrical resistivity at heating for some alloys. In addition, important part of this work is the development of new interatomic potential for U-Mo system made with taking into account details of studied structures.

Synthesis, Structure, Te Alloying, and Physical Properties of CuSbS 2

DOE PAGES

Hobbis, Dean; Wei, Kaya; Wang, Hsin; ...

2017-10-30

Materials with very low thermal conductivities continue to be of interest for a variety of applications. In this paper, we synthesized CuSbS 2 employing a mechanical alloying technique in order to investigate its physical properties. The trigonal pyramid arrangement of the S atoms around the Sb atoms allows for lone-pair electron formation that results in very low thermal conductivity. Finally, in addition to thermal properties, the structural, electrical, and optical properties, as well as compositional stability measurements, are also discussed. CuSbS 1.8Te 0.2 was similarly synthesized and characterized in order to compare its structural and transport properties with that ofmore » CuSbS 2, in addition to investigating the effect of Te alloying on these properties.« less

Synthesis, Structure, Te Alloying, and Physical Properties of CuSbS 2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hobbis, Dean; Wei, Kaya; Wang, Hsin

Materials with very low thermal conductivities continue to be of interest for a variety of applications. In this paper, we synthesized CuSbS 2 employing a mechanical alloying technique in order to investigate its physical properties. The trigonal pyramid arrangement of the S atoms around the Sb atoms allows for lone-pair electron formation that results in very low thermal conductivity. Finally, in addition to thermal properties, the structural, electrical, and optical properties, as well as compositional stability measurements, are also discussed. CuSbS 1.8Te 0.2 was similarly synthesized and characterized in order to compare its structural and transport properties with that ofmore » CuSbS 2, in addition to investigating the effect of Te alloying on these properties.« less

High-entropy alloys in hexagonal close-packed structure

DOE PAGES

Gao, Michael C.; Zhang, B.; Guo, S. M.; ...

2015-08-28

The microstructures and properties of high-entropy alloys (HEAs) based on the face-centered cubic and body-centered cubic structures have been studied extensively in the literature, but reports on HEAs in the hexagonal close-packed (HCP) structure are very limited. Using an efficient strategy in combining phase diagram inspection, CALPHAD modeling, and ab initio molecular dynamics simulations, a variety of new compositions are suggested that may hold great potentials in forming single-phase HCP HEAs that comprise rare earth elements and transition metals, respectively. Lastly, experimental verification was carried out on CoFeReRu and CoReRuV using X-ray diffraction, scanning electron microscopy, and energy dispersion spectroscopy.

Chemical complexity induced local structural distortion in NiCoFeMnCr high-entropy alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Fuxiang; Tong, Yang; Jin, Ke

In order to study chemical complexity-induced lattice distortion in high-entropy alloys, the static Debye–Waller (D-W) factor of NiCoFeMnCr solid solution alloy is measured with low temperature neutron diffraction, ambient X-ray diffraction, and total scattering methods. Here, the static atomic displacement parameter of the multi-element component alloy at 0 K is 0.035–0.041 Å, which is obvious larger than that of element Ni (~0 Å). The atomic pair distance between individual atoms in the alloy investigated with extended X-ray absorption fine structure (EXAFS) measurements indicates that Mn has a slightly larger bond distance (~0.4%) with neighbor atoms than that of others.

Chemical complexity induced local structural distortion in NiCoFeMnCr high-entropy alloy

DOE PAGES

Zhang, Fuxiang; Tong, Yang; Jin, Ke; ...

2018-06-16

In order to study chemical complexity-induced lattice distortion in high-entropy alloys, the static Debye–Waller (D-W) factor of NiCoFeMnCr solid solution alloy is measured with low temperature neutron diffraction, ambient X-ray diffraction, and total scattering methods. Here, the static atomic displacement parameter of the multi-element component alloy at 0 K is 0.035–0.041 Å, which is obvious larger than that of element Ni (~0 Å). The atomic pair distance between individual atoms in the alloy investigated with extended X-ray absorption fine structure (EXAFS) measurements indicates that Mn has a slightly larger bond distance (~0.4%) with neighbor atoms than that of others.

Formation Of Nano Layered Lamellar Structure In a Processed γ-TiAl Based Alloy

NASA Astrophysics Data System (ADS)

Heshmati-Manesh, S.; Shakoorian, H.; Armaki, H. Ghassemi; Ahmadabadi, M. Nili

2009-06-01

In this research, microstructures of an intermetallic alloy based on γ-TiAl has been investigated by optical and transmission electron microscopy. Samples of Ti-47Al-2Cr alloy were subjected to either a cyclic heat treatment or thermomechanical treatment with the aim of microstructural refinement. In both cases it was found that very fine lamellar structure with an interlamellar spacing in the nano scale is formed. Upon cyclic heat treatment, nano layers of α2 and γ ordered intermetallic phases were either formed during rapid cooling cycle in competition with massive structure formation, or formed as secondary lamellar structure during final stages of cyclic heat treatment. Also, TEM observations in hot forged specimens with initial lamellar structure revealed that micro twins form during the deformation within lamellar structure with twinning plates parallel to lamellar interfaces. Concurrent dynamic recrystallisation results in a nano layered structure with an interlamellar spacing of less than 100 nm.

Valence electronic structure of Ni in Ni Si alloys from relative K X-ray intensity studies

NASA Astrophysics Data System (ADS)

Kalayci, Y.; Aydinuraz, A.; Tugluoglu, B.; Mutlu, R. H.

2007-02-01

The Kβ-to-Kα X-ray intensity ratio of Ni in Ni 3Si, Ni 2Si and NiSi has been determined by energy dispersive X-ray fluorescence technique. It is found that the intensity ratio of Ni decreases from pure Ni to Ni 2Si and then increases from Ni 2Si to NiSi, in good agreement with the electronic structure calculations cited in the literature. We have also performed band structure calculations for pure Ni in various atomic configurations by means of linear muffin-tin orbital method and used this data with the normalized theoretical intensity ratios cited in the literature to estimate the 3d-occupation numbers of Ni in Ni-Si alloys. It is emphasized that investigation of alloying effect in terms of X-ray intensity ratios should be carried out for the stoichiometric alloys in order to make reliable and quantitative comparisons between theory and experiment in transition metal alloys.

Structure-property relations and modeling of small crack fatigue behavior of various magnesium alloys

NASA Astrophysics Data System (ADS)

Bernard, Jairus Daniel

Lightweight structural components are important to the automotive and aerospace industries so that better fuel economy can be realized. Magnesium alloys in particular are being examined to fulfill this need due to their attractive stiffness- and strength-to-weight ratios when compared to other materials. However, when introducing a material into new roles, one needs to properly characterize its mechanical properties. Fatigue behavior is especially important considering aerospace and automotive component applications. Therefore, quantifying the structure-property relationships and accurately predicting the fatigue behavior for these materials are vital. This study has two purposes. The first is to quantify the structure-property relationships for the fatigue behavior in an AM30 magnesium alloy. The second is to use the microstructural-based MultiStage Fatigue (MSF) model in order to accurately predict the fatigue behavior of three magnesium alloys: AM30, Elektron 21, and AZ61. While some studies have previously quantified the MSF material constants for several magnesium alloys, detailed research into the fatigue regimes, notably the microstructurally small crack (MSC) region, is lacking. Hence, the contribution of this work is the first of its kind to experimentally quantify the fatigue crack incubation and MSC regimes that are used for the MultiStage Fatigue model. Using a multi-faceted experimental approach, these regimes were explored with a replica method that used a dual-stage silicone based compound along with previously published in situ fatigue tests. These observations were used in calibrating the MultiStage Fatigue model.

Biocompatibility of Advanced Manufactured Titanium Implants-A Review.

PubMed

Sidambe, Alfred T

2014-12-19

Titanium (Ti) and its alloys may be processed via advanced powder manufacturing routes such as additive layer manufacturing (or 3D printing) or metal injection moulding. This field is receiving increased attention from various manufacturing sectors including the medical devices sector. It is possible that advanced manufacturing techniques could replace the machining or casting of metal alloys in the manufacture of devices because of associated advantages that include design flexibility, reduced processing costs, reduced waste, and the opportunity to more easily manufacture complex or custom-shaped implants. The emerging advanced manufacturing approaches of metal injection moulding and additive layer manufacturing are receiving particular attention from the implant fabrication industry because they could overcome some of the difficulties associated with traditional implant fabrication techniques such as titanium casting. Using advanced manufacturing, it is also possible to produce more complex porous structures with improved mechanical performance, potentially matching the modulus of elasticity of local bone. While the economic and engineering potential of advanced manufacturing for the manufacture of musculo-skeletal implants is therefore clear, the impact on the biocompatibility of the materials has been less investigated. In this review, the capabilities of advanced powder manufacturing routes in producing components that are suitable for biomedical implant applications are assessed with emphasis placed on surface finishes and porous structures. Given that biocompatibility and host bone response are critical determinants of clinical performance, published studies of in vitro and in vivo research have been considered carefully. The review concludes with a future outlook on advanced Ti production for biomedical implants using powder metallurgy.

Biocompatibility of Advanced Manufactured Titanium Implants—A Review

PubMed Central

Sidambe, Alfred T.

2014-01-01

Titanium (Ti) and its alloys may be processed via advanced powder manufacturing routes such as additive layer manufacturing (or 3D printing) or metal injection moulding. This field is receiving increased attention from various manufacturing sectors including the medical devices sector. It is possible that advanced manufacturing techniques could replace the machining or casting of metal alloys in the manufacture of devices because of associated advantages that include design flexibility, reduced processing costs, reduced waste, and the opportunity to more easily manufacture complex or custom-shaped implants. The emerging advanced manufacturing approaches of metal injection moulding and additive layer manufacturing are receiving particular attention from the implant fabrication industry because they could overcome some of the difficulties associated with traditional implant fabrication techniques such as titanium casting. Using advanced manufacturing, it is also possible to produce more complex porous structures with improved mechanical performance, potentially matching the modulus of elasticity of local bone. While the economic and engineering potential of advanced manufacturing for the manufacture of musculo-skeletal implants is therefore clear, the impact on the biocompatibility of the materials has been less investigated. In this review, the capabilities of advanced powder manufacturing routes in producing components that are suitable for biomedical implant applications are assessed with emphasis placed on surface finishes and porous structures. Given that biocompatibility and host bone response are critical determinants of clinical performance, published studies of in vitro and in vivo research have been considered carefully. The review concludes with a future outlook on advanced Ti production for biomedical implants using powder metallurgy. PMID:28788296

Effect of abrasive water jet on the structure of the surface layer of Al-Mg alloy

NASA Astrophysics Data System (ADS)

Tabatchikova, T. I.; Tereshchenko, N. A.; Yakovleva, I. L.; Gudnev, N. Z.

2017-09-01

Optical, scanning, and transmission electron microscopy methods, and X-ray diffraction analysis have been used to study the changes in the structure and the microhardness in the surface layer of the Al-Mg (5.8-6.8 wt %) alloy after water jet cutting. The dislocation density, the sizes of coherent scattering regions, and microdistortions have been determined. The transformation of the fine structure has been revealed in the displacement from the alloy volume to the abrasive-waterjet cutting surface.

Investigation of selected structural parameters in Fe 95Si 5 amorphous alloy during crystallization process

NASA Astrophysics Data System (ADS)

Fronczyk, Adam

2007-04-01

In this study, we report on a crystallization behavior of the Fe 95Si 5 metallic glasses using a differential scanning cabrimetry (DSC), and X-ray diffraction. The paper presents the results of experimental investigation of Fe 95Si 5 amorphous alloy, subjected to the crystallizing process by the isothermal annealing. The objective of the experiment was to determine changes in the structural parameters during crystallization process of the examined alloy. Crystalline diameter and the lattice constant of the crystallizing phase were used as parameters to evaluate structural changes in material.

Parametric Study of Amorphous High-Entropy Alloys formation from two New Perspectives: Atomic Radius Modification and Crystalline Structure of Alloying Elements

NASA Astrophysics Data System (ADS)

Hu, Q.; Guo, S.; Wang, J. M.; Yan, Y. H.; Chen, S. S.; Lu, D. P.; Liu, K. M.; Zou, J. Z.; Zeng, X. R.

2017-01-01

Chemical and topological parameters have been widely used for predicting the phase selection in high-entropy alloys (HEAs). Nevertheless, previous studies could be faulted due to the small number of available data points, the negligence of kinetic effects, and the insensitivity to small compositional changes. Here in this work, 92 TiZrHfM, TiZrHfMM, TiZrHfMMM (M = Fe, Cr, V, Nb, Al, Ag, Cu, Ni) HEAs were prepared by melt spinning, to build a reliable and sufficiently large material database to inspect the robustness of previously established parameters. Modification of atomic radii by considering the change of local electronic environment in alloys, was critically found out to be superior in distinguishing the formation of amorphous and crystalline alloys, when compared to using atomic radii of pure elements in topological parameters. Moreover, crystal structures of alloying element were found to play an important role in the amorphous phase formation, which was then attributed to how alloying hexagonal-close-packed elements and face-centered-cubic or body-centered-cubic elements can affect the mixing enthalpy. Findings from this work not only provide parametric studies for HEAs with new and important perspectives, but also reveal possibly a hidden connection among some important concepts in various fields.

Advanced high-temperature alloys: Processing and properties; Proceedings of the Nicholas J. Grant Symposium, MIT, Cambridge, MA, June 16-18, 1985

DOE Office of Scientific and Technical Information (OSTI.GOV)

Allen, S.M.; Pelloux, R.M.; Widmer, R.

1986-01-01

Historical and advanced methods of producing, forming and polishing alloys in billets and net shapes are explored. Attention is given to the deficiencies in arc furnace melts and to the benefits which are accruing from rapid solidification processing, powder metallurgy and superplastic forming. The techniques employed in these methods for processing materials to desired shapes, mainly for aircraft gas turbine engines, are described, along with the microstructures and mechanical properties which are obtained. The state of the art in casting and forming techniques which yield the most favorable properties in intermetallic compound-based alloys, superalloys, glasses and metacrystals are identified. Finally,more » research directions being pursued to obtain higher purity, enhanced temperature, longer lifetime, damage resistant alloys which can be formed to net shapes are discussed.« less

Synthesis of alloys with controlled phase structure

DOEpatents

Guthrie, Stephen Everett; Thomas, George John; Bauer, Walter; Yang, Nancy Yuan Chi

1999-04-20

A method for preparing controlled phase alloys useful for engineering and hydrogen storage applications. This novel method avoids melting the constituents by employing vapor transport, in a hydrogen atmosphere, of an active metal constituent, having a high vapor pressure at temperatures .apprxeq.300 C. and its subsequent condensation on and reaction with the other constituent (substrate) of an alloy thereby forming a controlled phase alloy and preferably a single phase alloy. It is preferred that the substrate material be a metal powder such that diffusion of the active metal constituent, preferably magnesium, and reaction therewith can be completed within a reasonable time and at temperatures .apprxeq.300 C. thereby avoiding undesirable effects such as sintering, local compositional inhomogeneities, segregation, and formation of unwanted second phases such as intermetallic compounds.

Synthesis of alloys with controlled phase structure

DOEpatents

Guthrie, S.E.; Thomas, G.J.; Bauer, W.; Yang, N.Y.C.

1999-04-20

A method is described for preparing controlled phase alloys useful for engineering and hydrogen storage applications. This novel method avoids melting the constituents by employing vapor transport, in a hydrogen atmosphere, of an active metal constituent, having a high vapor pressure at temperatures {approx_equal}300 C and its subsequent condensation on and reaction with the other constituent (substrate) of an alloy thereby forming a controlled phase alloy and preferably a single phase alloy. It is preferred that the substrate material be a metal powder such that diffusion of the active metal constituent, preferably magnesium, and reaction therewith can be completed within a reasonable time and at temperatures {approx_equal}300 C thereby avoiding undesirable effects such as sintering, local compositional inhomogeneities, segregation, and formation of unwanted second phases such as intermetallic compounds. 4 figs.

Special quasiordered structures: Role of short-range order in the semiconductor alloy (GaN) 1 -x(ZnO) x

NASA Astrophysics Data System (ADS)

Liu, Jian; Fernández-Serra, Maria V.; Allen, Philip B.

2016-02-01

This paper studies short-range order (SRO) in the semiconductor alloy (GaN) 1 -x(ZnO) x. Monte Carlo simulations performed on a density functional theory (DFT)-based cluster expansion model show that the heterovalent alloys exhibit strong SRO because of the energetic preference for the valence-matched nearest-neighbor Ga-N and Zn-O pairs. To represent the SRO-related structural correlations, we introduce the concept of special quasiordered structure (SQoS). Subsequent DFT calculations reveal the dramatic influence of SRO on the atomic, electronic, and vibrational properties of the (GaN) 1 -x(ZnO) x alloy. Due to the enhanced statistical presence of the energetically unfavored Zn-N bonds with the strong Zn 3 d -N 2 p repulsion, the disordered alloys exhibit much larger lattice bowing and band-gap reduction than those of the short-range ordered alloys. Lattice vibrational entropy tilts the alloy toward less SRO.

Effect of bimodal harmonic structure design on the deformation behaviour and mechanical properties of Co-Cr-Mo alloy.

PubMed

Vajpai, Sanjay Kumar; Sawangrat, Choncharoen; Yamaguchi, Osamu; Ciuca, Octav Paul; Ameyama, Kei

2016-01-01

In the present work, Co-Cr-Mo alloy compacts with a unique bimodal microstructural design, harmonic structure design, were successfully prepared via a powder metallurgy route consisting of controlled mechanical milling of pre-alloyed powders followed by spark plasma sintering. The harmonic structured Co-Cr-Mo alloy with bimodal grain size distribution exhibited relatively higher strength together with higher ductility as compared to the coarse-grained specimens. The harmonic Co-Cr-Mo alloy exhibited a very complex deformation behavior wherein it was found that the higher strength and the high retained ductility are derived from fine-grained shell and coarse-grained core regions, respectively. Finally, it was observed that the peculiar spatial/topological arrangement of stronger fine-grained and ductile coarse-grained regions in the harmonic structure promotes uniformity of strain distribution, leading to improved mechanical properties by suppressing the localized plastic deformation during straining. Copyright © 2015 Elsevier B.V. All rights reserved.

Subband Structure and Effective Mass in the Inversion Layer of a Strain Si-Based Alloy P-Type MOSFET.

PubMed

Chen, Kuan-Ting; Fan, Jun Wei; Chang, Shu-Tong; Lin, Chung-Yi

2015-03-01

In this paper, the subband structure and effective mass of an Si-based alloy inversion layer in a PMOSFET are studied theoretically. The strain condition considered in our calculations is the intrinsic strain resulting from growth of the silicon-carbon alloy on a (001) Si substrate and mechanical uniaxial stress. The quantum confinement effect resulting from the vertically effective electric field was incorporated into the k · p calculation. The distinct effective mass, such as the quantization effective mass and the density-of-states (DOS) effective mass, as well as the subband structure of the silicon-carbon alloy inversion layer for a PMOSFET under substrate strain and various effective electric field strengths, were all investigated. Ore results show that subband structure of relaxed silicon-carbon alloys with low carbon content are almost the same as silicon. We find that an external stress applied parallel to the channel direction can efficiently reduce the effective mass along the channel direction, thus producing hole mobility enhancement.

The effect of boron concentration on the structure and elastic properties of Ru-Ir alloys: first-principles calculations

NASA Astrophysics Data System (ADS)

Li, Xiaolong; Zhou, Zhaobo; Hu, Riming; Zhou, Xiaolong; Yu, Jie; Liu, Manmen

2018-04-01

The Phase stability, electronic structure, elastic properties and hardness of Ru-Ir alloys with different B concentration were investigated by first principles calculations. The calculated formation enthaplies and cohesive energies show that these compounds are all thermodynamically stable. Information on electronic structure indicates that they possess metallic characteristic and Ru-Ir-B alloys were composed of the Ru-B and Ir-B covalent bond. The elastic properties were calculated, which included bulk modulus, shear modulus, Young’s modulus, Poisson’s ratio and hardness. The calculated results reveal that the plastic of Ru-Ir-B alloys increase with the increase of the content of B atoms, but the hardness of Ru-Ir-B alloys have no substantial progress with the increase of the content of B atoms. However, it is interesting that the hardness of the Ru-Ir-B compound was improved obviously as the B content was higher than 18 atoms because of a phase structure transition.

Laser irradiation effects on the surface, structural and mechanical properties of Al-Cu alloy 2024

NASA Astrophysics Data System (ADS)

Yousaf, Daniel; Bashir, Shazia; Akram, Mahreen; kalsoom, Umm-i.-; Ali, Nisar

2014-02-01

Laser irradiation effects on surface, structural and mechanical properties of Al-Cu-Mg alloy (Al-Cu alloy 2024) have been investigated. The specimens were irradiated for various fluences ranging from 3.8 to 5.5 J/cm2 using an Excimer (KrF) laser (248 nm, 18 ns, 30 Hz) under vacuum environment. The surface and structural modifications of the irradiated targets have been investigated by scanning electron microscope (SEM) and X-ray diffractometer (XRD), respectively. SEM analysis reveals the formation of micro-sized craters along the growth of periodic surface structures (ripples) at their peripheries. The size of the craters initially increases and then decreases by increasing the laser fluence. XRD analysis shows an anomalous trend in the peak intensity and crystallite size of the specimen irradiated for various fluences. A universal tensile testing machine and Vickers microhardness tester were employed in order to investigate the mechanical properties of the irradiated targets. The changes in yield strength, ultimate tensile strength and microhardness were found to be anomalous with increasing laser fluences. The changes in the surface and structural properties of Al-Cu alloy 2024 after laser irradiation have been associated with the changes in mechanical properties.

Structural and electronic transport properties of compound forming HgPb liquid alloy using ab-initio pseudopotential

NASA Astrophysics Data System (ADS)

Sharma, Nalini; Thakur, Anil; Ahluwalia, P. K.

2013-02-01

The electrical resistivity of compound forming liquid alloy HgPb is studied as a function of concentration. Hard sphere diameters of Hg and Pb are obtained through the inter-ionic pair potential evaluated using Troullier and Martins ab initio pseudopotential, which have been used to calculate partial structure factors. Considering the liquid alloy to be a ternary mixture Ziman's formula for calculating the resistivity of binary liquid alloys, modified for complex formation, has been used. The concentration dependence in resistivity occurs due to preferential ordering of unlike atoms as nearest neighbours with help of complex formation model. Though the compound HgiPbi as per structure peaks is found to be less stable. However it contributes significantly to resistivity as compared to bare ions.

Structure of metal-oxide Ti-Ta-(Ti,Ta)xOy coatings during spark alloying and induction-thermal oxidation

NASA Astrophysics Data System (ADS)

Koshuro, V.; Fomin, A.; Fomina, M.; Rodionov, I.; Brzhozovskii, B.; Martynov, V.; Zakharevich, A.; Aman, A.; Oseev, A.; Majcherek, S.; Hirsch, S.

2016-08-01

The study focuses on combined spark alloying of titanium and titanium alloy surface and porous matrix structure oxidation. The metal-oxide coatings morphology is the result of melt drop transfer, heat treatment, and oxidation. The study establishes the influence of technological regimes of alloying and oxidation on morphological heterogeneity of metal- oxide system Ti-Ta-(Ti,Ta)xOy.

Three-dimensional nanometer scale analyses of precipitate structures and local compositions in titanium aluminide engineering alloys

NASA Astrophysics Data System (ADS)

Gerstl, Stephan S. A.

Titanium aluminide (TiAl) alloys are among the fastest developing class of materials for use in high temperature structural applications. Their low density and high strength make them excellent candidates for both engine and airframe applications. Creep properties of TiAl alloys, however, have been a limiting factor in applying the material to a larger commercial market. In this research, nanometer scale compositional and structural analyses of several TiAl alloys, ranging from model Ti-Al-C ternary alloys to putative commercial alloys with 10 components are investigated utilizing three dimensional atom probe (3DAP) and transmission electron microscopies. Nanometer sized borides, silicides, and carbide precipitates are involved in strengthening TiAl alloys, however, chemical partitioning measurements reveal oxygen concentrations up to 14 at. % within the precipitate phases, resulting in the realization of oxycarbide formation contributing to the precipitation strengthening of TiAl alloys. The local compositions of lamellar microstructures and a variety of precipitates in the TiAl system, including boride, silicide, binary carbides, and intermetallic carbides are investigated. Chemical partitioning of the microalloying elements between the alpha2/gamma lamellar phases, and the precipitate/gamma-matrix phases are determined. Both W and Hf have been shown to exhibit a near interfacial excess of 0.26 and 0.35 atoms nm-2 respectively within ca. 7 nm of lamellar interfaces in a complex TiAl alloy. In the case of needle-shaped perovskite Ti3AlC carbide precipitates, periodic domain boundaries are observed 5.3+/-0.8 nm apart along their growth axis parallel to the TiAl[001] crystallographic direction with concomitant composition variations after 24 hrs. at 800°C.

Structural difference rule for amorphous alloy formation by ion mixing

NASA Technical Reports Server (NTRS)

Liu, B.-X.; Johnson, W. L.; Nicolet, M.A.; Lau, S. S.

1983-01-01

A rule is formulated which establishes a sufficient condition that an amorphous binary alloy will be formed by ion mixing of multilayered samples when the two constituent metals are of different crystalline structure, regardless of their atomic sizes and electronegativities. The rule is supported by the experimental results obtained on six selected binary metal systems, as well as by the previous data reported in the literature. The amorphization mechanism is discussed in terms of the competition between two different structures resulting in frustration of the crystallization process.

Structural Phase Transformation in Strained Monolayer MoWSe2 Alloy.

PubMed

Apte, Amey; Kochat, Vidya; Rajak, Pankaj; Krishnamoorthy, Aravind; Manimunda, Praveena; Hachtel, Jordan A; Idrobo, Juan Carlos; Syed Amanulla, Syed Asif; Vashishta, Priya; Nakano, Aiichiro; Kalia, Rajiv K; Tiwary, Chandra Sekhar; Ajayan, Pulickel M

2018-04-24

Two-dimensional (2D) materials exhibit different mechanical properties from their bulk counterparts owing to their monolayer atomic thickness. Here, we have examined the mechanical behavior of 2D molybdenum tungsten diselenide (MoWSe 2 ) precipitation alloy grown using chemical vapor deposition and composed of numerous nanoscopic MoSe 2 and WSe 2 regions. Applying a bending strain blue-shifted the MoSe 2 and WSe 2 A 1g Raman modes with the stress concentrated near the precipitate interfaces predominantly affecting the WSe 2 modes. In situ local Raman measurements suggested that the crack propagated primarily thorough MoSe 2 -rich regions in the monolayer alloy. Molecular dynamics (MD) simulations were performed to study crack propagation in an MoSe 2 monolayer containing nanoscopic WSe 2 regions akin to the experiment. Raman spectra calculated from MD trajectories of crack propagation confirmed the emergence of intermediate peaks in the strained monolayer alloy, mirroring experimental results. The simulations revealed that the stress buildup around the crack tip caused an irreversible structural transformation from the 2H to 1T phase both in the MoSe 2 matrix and WSe 2 patches. This was corroborated by high-angle annular dark-field images. Crack branching and subsequent healing of a crack branch were also observed in WSe 2 , indicating the increased toughness and crack propagation resistance of the alloyed 2D MoWSe 2 over the unalloyed counterparts.

Advances in Solid State Joining of High Temperature Alloys

NASA Technical Reports Server (NTRS)

Ding, R. Jeff; Schneider, Judy; Walker, Bryant

2011-01-01

Many of the metals used in the oil and gas industry are difficult to fusion weld including titanium and its alloys. Thus solid state joining processes, such as friction stir welding (FSWing) and a patented modification termed thermal stir welding (TSWing), are being pursued as alternatives to produce robust structures more amenable to high pressure applications. Unlike the FSWing process where the tool is used to heat the workpiece, TSWing utilizes an induction coil to preheat the material prior to stirring thus minimizing the burden on the weld tool and thereby extending its life. This study reports on the initial results of using a hybrid (H)-TSW process to join commercially pure, 1.3cm thick panels of titanium (CP Ti) Grade 2.

The Analysis of the General Performance and Mechanical Behavior of Unirradiated FeCrAl Alloys Before and After Welding

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gussev, Maxim N.; Field, Kevin G.; Yamamoto, Yukinori

2016-06-03

The present report summarizes and discusses the preliminary results for the in-depth characterization of the modern, nuclear-grade FeCrAl alloys currently under development. The alloys were designed for enhanced radiation tolerance and weldability, and the research is currently being pursued by the Department of Energy (DOE) Nuclear Energy Enabling Technologies (NEET) program. Last year, seven candidate FeCrAl alloys with well-controlled chemistry and microstructures were designed and produced; welding was performed under well-controlled conditions. The structure and general performance of unirradiated alloys were assessed using standardized and advanced microstructural characterization techniques and mechanical testing. The primary objective is to identify the bestmore » candidate alloy, or at a minimum to identify the contributing factors that increase the weldability and radiation tolerance of FeCrAl alloys, therefore enabling future generations of FeCrAl alloys to deliver better performance parameters. This report is structured so as to describe these critical assessments of the weldability; radiation tolerance will be reported on in later reports from this program.« less

Design, processing and characterization of mechanically alloyed galfenol & lightly rare-earth doped FeGa alloys as smart materials for actuators and transducers

NASA Astrophysics Data System (ADS)

Taheri, Parisa

Smart materials find a wide range of application areas due to their varied response to external stimuli. The different areas of application can be in our day to day life, aerospace, civil engineering applications, and mechatronics to name a few. Magnetostrictive materials are a class of smart materials that can convert energy between the magnetic and elastic states. Galfenol is a magnetostrictive alloy comprised primarily of the elements iron (Fe) and gallium (Ga). Galfenol exhibits a unique combination of mechanical and magnetostrictive (magnetic) properties that legacy smart materials do not. Galfenol's ability to function while in tension, mechanical robustness and high Curie temperature (600 °C) is attracting interest for the alloy's use in mechanically harsh and elevated temperature environments. Applications actively being investigated include transducers for down-hole use, next-generation fuel injectors, sensing, and energy harvesting devices. Understanding correlations between microstructure, electronic structure, and functional response is key to developing novel magnetostrictive materials for sensor and actuator technologies. To this end, in the first part of this thesis we report successful fabrication and investigation of magnetic and magnetostrictive properties of mechanically alloyed Fe81Ga19 compounds. For the first time, we could measure magnetostrictive properties of mechanically alloyed FeGa compounds. A maximum saturation magnetostriction of 41 ppm was achieved which is comparable to those measured from polycrystalline FeGa alloys prepared by other processing techniques, namely gas atomization and cold rolling. Overall, this study demonstrates the feasibility of large-scale production of FeGa polycrystalline alloys powders by a simple and cost-effective mechanical alloying technique. In the second part of this work, we report for the first time, experimental results pertaining to successful fabrication and advanced characterization of a series

Fine structure of Fe-Co-Ga and Fe-Cr-Ga alloys with low Ga content

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kleinerman, Nadezhda M., E-mail: kleinerman@imp.uran.ru; Serikov, Vadim V., E-mail: kleinerman@imp.uran.ru; Vershinin, Aleksandr V., E-mail: kleinerman@imp.uran.ru

2014-10-27

Investigation of Ga influence on the structure of Fe-Cr and Fe-Co alloys was performed with the use of {sup 57}Fe Mössbauer spectroscopy and X-ray diffraction methods. In the alloys of the Fe-Cr system, doping with Ga handicaps the decomposition of solid solutions, observed in the binary alloys, and increases its stability. In the alloys with Co, Ga also favors the uniformity of solid solutions. The analysis of Mössbauer experiments gives some grounds to conclude that if, owing to liquation, clusterization, or initial stages of phase separation, there exist regions enriched in iron, some amount of Ga atoms prefer to entermore » the nearest surroundings of iron atoms, thus forming binary Fe-Ga regions (or phases)« less

Prediction of Fatigue Crack Growth of Repaired Al-alloy Structures with Double Sides

NASA Astrophysics Data System (ADS)

Benachour, M.; Benachour, N.; Benguediab, M.; Seriari, F. Z.

During navigation, aircrafts are subject to fatigue damage. In order to rehabilitate damaged structures some techniques are often used to resolve this problem. Efficient repair technique, called composite patch repair, was used to reinforce the damaged structures and stop cracks. In this paper, effect of composite patch repair (Boron/Epoxy) on fatigue crack growth (FCG) was investigated on 2219 T62 Al-alloy. Effects of double patch repair in single notch tensile specimen (SENT) on FCG were studied and compared to single patch repair. Results show beneficial effect of patch repair on fatigue life and FCGR in comparison with the un-patched specimen. In addition, effect of mean stress characterized by stress ratio was highlighted. Fatigue behavior of investigated Al-alloy was compared.

Pressure-dependent structure of the null-scattering alloy Ti 0.676 Zr 0.324

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zeidler, Anita; Guthrie, Malcolm; Salmon, Philip S.

2015-05-13

The room temperature structure of the alloy Ti0.676Zr0.324Ti0.676Zr0.324 was measured by X-ray diffraction under compression at pressures up to ~30GPa. This alloy is used as a construction material in high pressure neutron-scattering research and has a mean coherent neutron scattering length of zero, that is, it is a so-called null-scattering alloy. A broad phase transition was observed from a hexagonal close-packed α-phase to a hexagonal ω-phase, which started at a pressure of ≲12GPa≲12GPa and was completed by ~25GPa. The data for the α-phase were fitted by using a third-order Birch–Murnaghan equation of state, giving an isothermal bulk modulus B0=87(4)GPaB0=87(4)GPa andmore » pressure derivative B'0=6.6(8)B0'=6.6(8). The results will help to ensure that accurate structural information can be gained from in situ high pressure neutron diffraction work on amorphous and liquid materials where the Ti0.676Zr0.324Ti0.676Zr0.324 alloy is used as a gasket material.« less

Development and Characterization of High Performance Shape Memory Alloy Coatings for Structural Aerospace Applications.

PubMed

Exarchos, Dimitrios A; Dalla, Panagiota T; Tragazikis, Ilias K; Dassios, Konstantinos G; Zafeiropoulos, Nikolaos E; Karabela, Maria M; De Crescenzo, Carmen; Karatza, Despina; Musmarra, Dino; Chianese, Simeone; Matikas, Theodore E

2018-05-18

This paper presents an innovative approach, which enables control of the mechanical properties of metallic components by external stimuli to improve the mechanical behavior of aluminum structures in aeronautical applications. The approach is based on the exploitation of the shape memory effect of novel Shape Memory Alloy (SMA) coatings deposited on metallic structural components, for the purpose of relaxing the stress of underlying structures by simple heating at field-feasible temperatures, therefore enhancing their structural integrity and increasing their stiffness and rigidity while allowing them to withstand expected loading conditions safely. Numerical analysis provided an insight in the expected response of the SMA coating and of the SMA-coated element, while the dependence of alloy composition and heat treatment on the experienced shape memory effect were investigated experimentally. A two-phase process is proposed for deposition of the SMA coating in an order that induces beneficial stress relaxation to the underlying structure through the shape memory effect.

Development and Characterization of High Performance Shape Memory Alloy Coatings for Structural Aerospace Applications

PubMed Central

Exarchos, Dimitrios A.; Dalla, Panagiota T.; Tragazikis, Ilias K.; Zafeiropoulos, Nikolaos E.; Karabela, Maria M.; De Crescenzo, Carmen; Karatza, Despina; Matikas, Theodore E.

2018-01-01

This paper presents an innovative approach, which enables control of the mechanical properties of metallic components by external stimuli to improve the mechanical behavior of aluminum structures in aeronautical applications. The approach is based on the exploitation of the shape memory effect of novel Shape Memory Alloy (SMA) coatings deposited on metallic structural components, for the purpose of relaxing the stress of underlying structures by simple heating at field-feasible temperatures, therefore enhancing their structural integrity and increasing their stiffness and rigidity while allowing them to withstand expected loading conditions safely. Numerical analysis provided an insight in the expected response of the SMA coating and of the SMA-coated element, while the dependence of alloy composition and heat treatment on the experienced shape memory effect were investigated experimentally. A two-phase process is proposed for deposition of the SMA coating in an order that induces beneficial stress relaxation to the underlying structure through the shape memory effect. PMID:29783626

Phase Structure and Site Preference Behavior of Ternary Alloying Additions to PdTi and PtTi Shape-Memory Alloys

NASA Technical Reports Server (NTRS)

Bozzolo, Guillermo; Mosca, Hugo O.; Noebe, Ronald D.

2006-01-01

The phasc structure and concentration dependence of the lattice parameter and energy of formation of ternary Pd-'I-X and Pt-Ti-X alloys for a large number of ternary alloying additions X (X = Na, Mg, Al, Si, Sc. V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Ag, Cd, Hf, Ta, W, Re, Os, Ir) are investigated with an atomistic modeling approach. In addition, a detailed description of the site preference behavior of such additions showing that the elements can be grouped according to their absolute preference for a specific site, regardless of concentration, or preference for available sites in the deficient sublattice is provided.

Unusual Thermal Stability of High-Entropy Alloy Amorphous Structure

DTIC Science & Technology

2012-06-20

incident angle X - ray diffractometer (GIAXRD, RIGAKU D/MAX2500) with Cu Kα radiation and at the incident angle of 1°. The surface morphology and...microanalyzer (EPMA, JEOL JAX-8800). The crystallographic structures of as-deposited and annealed metallic films were characterized utilizing a glancing ...field image and selected-area- diffraction (SAD) patterns of (a) 800 °C-, (b) 850 °C- and (c) 900 °C-annealed alloy thin films, respectively. Both

Liquid-liquid phase separation and core-shell structure of ternary Al-In-Sn immiscible alloys

NASA Astrophysics Data System (ADS)

Zhao, Degang; Bo, Lin; Wang, Lin; Li, Shanshan

2018-04-01

In this study, the liquid-liquid phase separation of four kinds of ternary immiscible Al-In-Sn melts was investigated with resistivity and thermodynamics method. The nonlinear changes in ρ-T and DSC curves of Al-In-Sn immiscible alloys above monotectic reaction temperature revealed the occurrence of liquid-liquid phase separation of Al-In-Sn melts. The monotectic temperature, liquid phase separation temperature and immiscible gap of ternary Al-In-Sn alloys were lower than those of binary Al-In alloy. With the Al content decreasing, the immiscible gap of Al-In-Sn alloy decreased. The composition of Al80In10Sn10, Al70In15Sn15, Al60In20Sn20 and Al50In25Sn25 was located in the immiscible zone of Al-In-Sn system. Due to the differences of Stokes effect, Marangoni convection and immiscible gap, the solidification morphology of four kinds of Al-In-Sn monotectic alloy was different. The core–shell structure of Al-In-Sn monotectic alloy can form within a certain range of composition.

Cellular response of osteoblasts to low modulus Ti-24Nb-4Zr-8Sn alloy mesh structure.

PubMed

Nune, K C; Misra, R D K; Li, S J; Hao, Y L; Yang, R

2017-03-01

Titanium alloys (Ti-6Al-4V and Ti-6Al-7Nb) are widely used for implants, which are characterized by high elastic modulus (∼110 GPa) with (α + β) structure and that may induce undesirable stress shielding effect and immune responses associated with the presence of toxic elements. In this regard, we have combined the attributes of a new alloy design and the concept of additive manufacturing to fabricate 3D scaffolds with an interconnected porous structure. The new alloy is a β-type Ti-24Nb-4Zr-8Sn (Ti2448) alloy with significantly reduced modulus. In the present study, we explore the biological response of electron beam melted low modulus Ti2448 alloy porous mesh structure through the elucidation of bioactivity and osteoblast functions. The cellular activity was explored in terms of cell-to-cell communication involving proliferation, spreading, synthesis of extracellular and intracellular proteins, differentiation, and mineralization. The formation of fine apatite-like crystals on the surface during immersion test in simulated body fluid confirmed the bioactivity of the scaffold surface, which provided the favorable osteogenic microenvironment for cell-material interaction. The combination of unique surface chemistry and interconnected porous architecture provided the desired pathway for supply of nutrients and oxygen to cells and a favorable osteogenic micro-environment for incorporation (on-growth and in-growth) of osteoblasts. The proliferation and differentiation of pre-osteoblasts and their ability to form a well mineralized bone-like extracellular matrix (ECM) by secreting bone markers (ALP, calcium, etc.) over the struts of the scaffold point toward the determining role of unique surface chemistry and 3D architecture of the Ti2448 alloy mesh structure in modulating osteoblasts functions. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 859-870, 2017. © 2016 Wiley Periodicals, Inc.

Atomic and electronic basis for the serrations of refractory high-entropy alloys

NASA Astrophysics Data System (ADS)

Wang, William Yi; Shang, Shun Li; Wang, Yi; Han, Fengbo; Darling, Kristopher A.; Wu, Yidong; Xie, Xie; Senkov, Oleg N.; Li, Jinshan; Hui, Xi Dong; Dahmen, Karin A.; Liaw, Peter K.; Kecskes, Laszlo J.; Liu, Zi-Kui

2017-06-01

Refractory high-entropy alloys present attractive mechanical properties, i.e., high yield strength and fracture toughness, making them potential candidates for structural applications. Understandings of atomic and electronic interactions are important to reveal the origins for the formation of high-entropy alloys and their structure-dominated mechanical properties, thus enabling the development of a predictive approach for rapidly designing advanced materials. Here, we report the atomic and electronic basis for the valence-electron-concentration-categorized principles and the observed serration behavior in high-entropy alloys and high-entropy metallic glass, including MoNbTaW, MoNbVW, MoTaVW, HfNbTiZr, and Vitreloy-1 MG (Zr41Ti14Cu12.5Ni10Be22.5). We find that the yield strengths of high-entropy alloys and high-entropy metallic glass are a power-law function of the electron-work function, which is dominated by local atomic arrangements. Further, a reliance on the bonding-charge density provides a groundbreaking insight into the nature of loosely bonded spots in materials. The presence of strongly bonded clusters and weakly bonded glue atoms imply a serrated deformation of high-entropy alloys, resulting in intermittent avalanches of defects movement.

Characteristics of aluminum alloy microplastic deformation in different structural states

DOE Office of Scientific and Technical Information (OSTI.GOV)

Seregin, G.V.; Efimenko, L.L.; Leonov, M.V.

The solution to the problem of improving the mechanical properties (including cyclic strength) of structural materials is largely dependent on our knowledge of the laws governing the development of microplastic deformations in them. The effect of heat and mechanical treatment on the elastoplastic properties and fatigue resistance of the commercial aluminum alloys AK4-1 and D16 is analyzed.

The structure and mechanical properties of AlMg5Si2Mn alloy after surface alloying by the use of fiber laser

NASA Astrophysics Data System (ADS)

Pakieła, Wojciech; Tanski, Tomasz; Pawlyta, Mirosława; Pakieła, Katarzyna; Brytan, Zbigniew; Sroka, Marek

2018-03-01

Laser surface treatment is successfully applied to increase hardness as well as corrosion and wear resistance in light alloys such as aluminum or magnesium. The laser surface remelting also can be used to repair superficial cracks, voids or porosity caused by the mechanical impact, metallurgical process as well as the corrosive environment on the surface of the aluminum alloy. The purpose of this paper was to investigate the influence of a fiber laser surface treatment on the structure and properties of the EN AC AlMg5Si2Mn alloy. The goal of this investigation was to increase the hardness and improve tribological properties of the aluminum alloy surface as a result of the conducted laser surface treatment. During laser processing, the top surface of the aluminum alloy was enriched with Cr and Ni particles. The grain size of the applied particles was approximately about 60-130 m. The Cr-Ni powder has been introduced in the molten pool using vacuum feeder at a constant rate of 4.5 g/min. For surface remelting we used square laser beam at a size 3 × 3 mm and with the power of 3.0 kW. The linear laser scan rate of the beam was set at 0.5 m/min. Argon was used to protect the liquid metal alloy during surface treatment. Application of the laser treatment on aluminum alloy has enabled to obtain much harder as well as better wear resistant material compared to the untreated EN AC AlMg5Si2Mn.

Local structure of NiPd solid solution alloys and its response to ion irradiation

DOE PAGES

Zhang, Fuxiang; Ullah, Mohammad Wali; Zhao, Shijun; ...

2018-04-27

The local structure of Ni$-$Pd solid solution alloys with compositions of Ni 80Pd 20 and Ni 50Pd 50 was investigated with anomalous X-ray diffraction, X-ray absorption and theoretical calculation/simulation. The fcc lattice is distorted for both alloys, and the Pd$-$Pd atomic pair distance is +4.4% and +1.4% larger than ideal values in Ni 80Pd 20 and Ni 50Pd 50 alloys, respectively. The corresponding atomic pair distance of Ni$-$Ni is -1.8% and -3.0% less than the ideal values. Different short-range orders in the alloys were quantitatively identified at the atomic level. In Ni 80Pd 20, Pd atoms are likely to formmore » Pd$-$Pd pairs, while Pd atoms are connected with Pd atoms in the second shell in the equiatomic solid solution alloy. Upon ion irradiation, little change of interatomic distance, but modification of chemical short-range order was observed. The number of Pd$-$Pd pairs decreases to the lowest value at 0.1 dpa, and further irradiation make it increase.« less

Local structure of NiPd solid solution alloys and its response to ion irradiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Fuxiang; Ullah, Mohammad Wali; Zhao, Shijun

The local structure of Ni$-$Pd solid solution alloys with compositions of Ni 80Pd 20 and Ni 50Pd 50 was investigated with anomalous X-ray diffraction, X-ray absorption and theoretical calculation/simulation. The fcc lattice is distorted for both alloys, and the Pd$-$Pd atomic pair distance is +4.4% and +1.4% larger than ideal values in Ni 80Pd 20 and Ni 50Pd 50 alloys, respectively. The corresponding atomic pair distance of Ni$-$Ni is -1.8% and -3.0% less than the ideal values. Different short-range orders in the alloys were quantitatively identified at the atomic level. In Ni 80Pd 20, Pd atoms are likely to formmore » Pd$-$Pd pairs, while Pd atoms are connected with Pd atoms in the second shell in the equiatomic solid solution alloy. Upon ion irradiation, little change of interatomic distance, but modification of chemical short-range order was observed. The number of Pd$-$Pd pairs decreases to the lowest value at 0.1 dpa, and further irradiation make it increase.« less

A Study of Phase Composition and Structure of Alloys of the Al - Mg - Si - Fe System

NASA Astrophysics Data System (ADS)

Mailybaeva, A. D.; Zolotorevskii, V. S.; Smagulov, D. U.; Islamkulov, K. M.

2017-03-01

The Thermo-Calc software is used to compute the phase transformations occurring during cooling of alloys. Polythermal and isothermal sections of the phase diagram of the Al - Mg - Si - Fe system are plotted. The phase composition and the structure of aluminum alloys in cast condition and after a heat treatment are studied experimentally.

Structure-property relationships in oxide-dispersed iron-beryllia alloys

NASA Technical Reports Server (NTRS)

Wolf, S.; Grant, N. J.

1977-01-01

Two BeO dispersed iron alloys containing about 2.5 and 5.5 v/o dispersoid were produced by attritting, internally oxidizing, and extruding dilute, prealloyed Fe-Be powders. As-extruded alloys were given various thermomechanical treatments involving room temperature swaging and annealing above and below the allotropic transformation temperature. The elevated temperature rupture strengths were measured and correlated with changes in structure; strengthening trends were examined in the light of proposed models for such strengthening. The results obtained showed that the elevated temperature strength was determined by the oxide interparticle spacing (IPS) in recrystallized material and IPS as well as prior deformation in swaged specimens. In fact, a parametric correlation was found between rupture strength values in the longitudinal direction with prestrain during swaging. The overall pattern in strength and microstructural observations were more consistent with a strength-stored energy (substructure) dependence than a strength-grain shape (grain aspect ratio) relation.

Partial structure factors reveal atomic dynamics in metallic alloy melts

NASA Astrophysics Data System (ADS)

Nowak, B.; Holland-Moritz, D.; Yang, F.; Voigtmann, Th.; Kordel, T.; Hansen, T. C.; Meyer, A.

2017-07-01

We investigate the dynamical decoupling of the diffusion coefficients of the different components in a metallic alloy melt, using a combination of neutron diffraction, isotopic substitution, and electrostatic levitation in Zr-Ni melts. We show that excess Ni atoms can diffuse more freely in a background of saturated chemical interaction, causing their dynamics to become much faster and thus decoupled than anticipated from the interparticle interactions. Based on the mode-coupling theory of the glass transition, the averaged structure as given by the partial static structure factors is able to explain the observed dynamical behavior.

Dynamic Recrystallization Behavior of Zr-1Sn-0.3Nb Alloy During Hot Rolling Process

NASA Astrophysics Data System (ADS)

Zhao, Siyu; Liu, Huiqun; Lin, Gaoyong; Jiang, Yilan; Xun, Jian

2017-11-01

Zirconium alloys are advanced materials with properties that are greatly affected by their crystalline structure. To investigate this, sheets of Zr-1Sn-0.3Nb alloy were hot rolled with different reductions (10%, 30%, 50%, and 60%) at 1023 K and 1073 K to investigate the alloy's dynamic recrystallization behavior. Recrystallization kinetics was observed via electron backscattering diffraction and transmission electron microscopy, and the results were compared with estimates based on the Johnson-Mehl-Avrami-Kolmogorov (JMAK) equation. The values of the JMAK exponent n and k increased with the rolling temperature. The estimates and microstructural observations of dynamic recrystallization (DRX) kinetics were in good agreement.

Structural, elastic and electronic properties of typical NdMgT4 (T = Co, Ni, Cu) alloys from ab initio calculation

NASA Astrophysics Data System (ADS)

Wang, Na; Zhang, Wei-bing; Tang, Bi-yu; Gao, Hai-Tao; He, En-jie; Wang, Lei

2018-07-01

The crystal structure, elastic and magnetic properties of important ternary Mg-based alloys NdMgT4 (T = Co, Ni, Cu) have been studied using reliable ab initio calculations. Both cohesive energy and charge density difference suggest that three alloys have good structural stability with the order: NdMgCo4 > NdMgNi4 > NdMgCu4. It shows that NdMgCo4 alloy has magnetic moments with the Co atoms being the main contribution, which is also in agreement with the calculated electronic structures. We find that NdMgT4 (T = Co, Ni, Cu) alloys are all ductile materials with bulk-to-shear modulus (B/G) values higher than 1.75. The trends of calculated values for the shear moduli Cs and C44 are consistent with that of shear modulus G and young's modulus E, proving that NdMgT4 (T = Co, Ni, Cu) alloys exhibit good plasticity with the trend: NdMgNi4 > NdMgCu4 > NdMgCo4. These calculated results give the basis guidance for the design of rare earth-magnesium-transition metal (R-Mg-T) alloys with improved mechanical properties.

The influence of interfacial energies and gravitational levels on the directionally solidified structures in hypermonotectic alloys

NASA Technical Reports Server (NTRS)

Andrews, J. B.; Curreri, P. A.; Sandlin, A. C.

1988-01-01

Various Cu-Pb-Al alloys were directionally solidified under 1-g conditions and alternating high-g/low-g conditions (achieved using NSAS's KC-135 aircraft) as a means of studying the influence of interfacial energies and gravitational levels on the resulting microstructures. Directional solidification of low Al content alloys was found to result in samples with coarser more irregular microstructures than in alloys with high Al contents under all the gravity conditions considered. Structures are correlated with interfacial energies, growth rates, and gravitational levels.

Optimization of the random multilayer structure to break the random-alloy limit of thermal conductivity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Yan; Gu, Chongjie; Ruan, Xiulin, E-mail: ruan@purdue.edu

2015-02-16

A low lattice thermal conductivity (κ) is desired for thermoelectrics, and a highly anisotropic κ is essential for applications such as magnetic layers for heat-assisted magnetic recording, where a high cross-plane (perpendicular to layer) κ is needed to ensure fast writing while a low in-plane κ is required to avoid interaction between adjacent bits of data. In this work, we conduct molecular dynamics simulations to investigate the κ of superlattice (SL), random multilayer (RML) and alloy, and reveal that RML can have 1–2 orders of magnitude higher anisotropy in κ than SL and alloy. We systematically explore how the κmore » of SL, RML, and alloy changes relative to each other for different bond strength, interface roughness, atomic mass, and structure size, which provides guidance for choosing materials and structural parameters to build RMLs with optimal performance for specific applications.« less

Biomimetic hydrophobic surface fabricated by chemical etching method from hierarchically structured magnesium alloy substrate

NASA Astrophysics Data System (ADS)

Liu, Yan; Yin, Xiaoming; Zhang, Jijia; Wang, Yaming; Han, Zhiwu; Ren, Luquan

2013-09-01

As one of the lightest metal materials, magnesium alloy plays an important role in industry such as automobile, airplane and electronic product. However, magnesium alloy is hindered due to its high chemical activity and easily corroded. Here, inspired by typical plant surfaces such as lotus leaves and petals of red rose with super-hydrophobic character, the new hydrophobic surface is fabricated on magnesium alloy to improve anti-corrosion by two-step methodology. The procedure is that the samples are processed by laser first and then immersed and etched in the aqueous AgNO3 solution concentrations of 0.1 mol/L, 0.3 mol/L and 0.5 mol/L for different times of 15 s, 40 s and 60 s, respectively, finally modified by DTS (CH3(CH2)11Si(OCH3)3). The microstructure, chemical composition, wettability and anti-corrosion are characterized by means of SEM, XPS, water contact angle measurement and electrochemical method. The hydrophobic surfaces with microscale crater-like and nanoscale flower-like binary structure are obtained. The low-energy material is contained in surface after DTS treatment. The contact angles could reach up to 138.4 ± 2°, which hydrophobic property is both related to the micro-nano binary structure and chemical composition. The results of electrochemical measurements show that anti-corrosion property of magnesium alloy is improved. Furthermore, our research is expected to create some ideas from natural enlightenment to improve anti-corrosion property of magnesium alloy while this method can be easily extended to other metal materials.

Correlations Between Structural and Magnetic Properties of Co2 FeSi Heusler-Alloy Thin Films

NASA Astrophysics Data System (ADS)

Zhu, Weihua; Wu, Di; Zhao, Bingcheng; Zhu, Zhendong; Yang, Xiaodi; Zhang, Zongzhi; Jin, Q. Y.

2017-09-01

The structural and magnetic properties are the most important parameters for practical applications of Co-based Heusler alloys. The correlations between the crystallization degree, chemical order, magnetic coercivity, saturation magnetization (MS ), and in-plane magnetic anisotropies are systematically investigated for Co2FeSi (CFS) films fabricated at different temperatures (TS ). XRD shows that the CFS layer changes progressively from a disordered crystal structure into a chemically disordered A 2 structure and further into a chemically ordered B 2 and even L 21 structures when increasing TS up to 480 °C . Meanwhile, the static angular remanence magnetization curves show a clear transition of magnetic anisotropy from twofold to fourfold symmetry, due to the competition effect between the uniaxial anisotropy field HU and biaxial anisotropy field HB . The HU value is found to be weakly dependent on TS , while HB shows a continuous enhancement at TS>300 °C , implying that the enhancement of the L 21 ordering degree would not weaken the biaxial anisotropy. The varying trend of HB is similar to MS , which can be respectively attributed to the improved crystal structure and chemical order. The anisotropic fields and their variation behaviors determined by a vibrating sample magnetometer are highly consistent with the results by a time-resolved magneto-optical Kerr effect study. Our findings provide a better understanding of the structural ordering and magnetic anisotropy, which will be helpful for designing advanced spintronic devices.

Influence of Severe Plastic Deformation on the Structure and Properties of Al-Li-Cu-Mg-Zr-Sc-Zn Alloy

NASA Astrophysics Data System (ADS)

Kaigorodova, L. I.; Rasposienko, D. Yu.; Pushin, V. G.; Pilyugin, V. P.; Smirnov, S. V.

2018-02-01

The structural and phase transformations in the Al-Li-Cu-Mg-Zr-Sc-Zn alloy have been studied by the electron microscopy after the aging for the maximum strength and in the nanostructured state after severe plastic deformation by high-pressure torsion. It has been shown that severe plastic deformation leads to the formation of a nanostructured state in the alloy, the nature of which is determined by the magnitude of deformation and the degree of completeness of the dynamic recrystallization. It has been established that deformation also causes a change in the phase composition of the alloy. The influence of the structural components of the severely deformed alloy on the level of mechanical properties, such as the hardness, plasticity, elastic modulus, and stiffness has been discussed.

Embedded-atom-method study of structural, thermodynamic, and atomic-transport properties of liquid Ni-Al alloys

NASA Astrophysics Data System (ADS)

Asta, Mark; Morgan, Dane; Hoyt, J. J.; Sadigh, Babak; Althoff, J. D.; de Fontaine, D.; Foiles, S. M.

1999-06-01

Structural, thermodynamic, and atomic-transport properties of liquid Ni-Al alloys have been studied by Monte Carlo and molecular-dynamics simulations based upon three different embedded-atom method (EAM) interatomic potentials, namely those due to Foiles and Daw (FD) [J. Mater. Res. 2, 5 (1987)], Voter and Chen (VC) [in Characterization of Defects in Materials, edited by R. W. Siegel et al. MRS Symposia Proceedings. No. 82 (Materials Research Society, Pittsburgh, 1987), p.175] and Ludwig and Gumbsch (LG) [Model. Simul. Mater. Sci. Eng. 3, 533 (1995)]. We present detailed comparisons between calculated results and experimental data for structure factors, atomic volumes, enthalpies of mixing, activities, and viscosities. Calculated partial structure factors are found to be in semiquantitative agreement with published neutron scattering measurements for Ni20Al80 alloys, indicating that short-range order in the liquid phase is qualitatively well described. Calculated thermodynamic properties of mixing are found to agree very well with experimental data for Ni compositions greater than 75 atomic %, while for alloys richer in Al the magnitudes of the enthalpies and entropies of mixing are significantly underestimated. The VC and LG potentials give atomic densities and viscosities in good agreement with experiment for Ni-rich compositions, while FD potentials consistently underestimate both properties at all concentrations. The results of this study demonstrate that VC and LG potentials provide a realistic description of the thermodynamic and atomic transport properties for NixAl1-x liquid alloys with x>=0.75, and point to the limitations of EAM potentials for alloys richer in Al.

Structural, magnetic and transport studies of Mn0.8Cr0.2CoGe alloy

NASA Astrophysics Data System (ADS)

Das, S. C.; Dutta, P.; Pramanick, S.; Chatterjee, S.

2018-04-01

Different physical and functional properties of Mn0.8Cr0.2CoGe alloy has been investigated through structural, magnetic and electrical transport measurements. Substitution of Cr for Mn results significant decrease in both structural and magnetic transition temperature and brings them well below the room temperature. A reasonable amount of conventional magnetocaloric effect (ΔS˜ - 2.22 J/kg-K for magnetic field (H) changing from 0 to 50 kOe) with large relative cooling power (251.7 J/kg for H changing from 0 to 50 kOe) has also been observed around the region of transition. On thermal cycling through the structural transition, noticeable training effect is found to be associated with the resistivity of the alloy.

Castable nickel aluminide alloys for structural applications

DOEpatents

Liu, Chain T.

1992-01-01

The specification discloses nickel aluminide alloys which include as a component from about 0.5 to about 4 at. % of one or more of the elements selected from the group consisting of molybdenum or niobium to substantially improve the mechanical properties of the alloys in the cast condition.

Effect of High Strain-Rate Deformation and Aging Temperature on the Evolution of Structure, Microhardness, and Wear Resistance of Low-Alloyed Cu-Cr-Zr Alloy

NASA Astrophysics Data System (ADS)

Kheifets, A. E.; Khomskaya, I. V.; Korshunov, L. G.; Zel'dovich, V. I.; Frolova, N. Yu.

2018-04-01

The effect of the preliminary high strain-rate deformation, performed via the method of dynamic channel-angular pressing (DCAP), and subsequent annealings on the tribological properties of a dispersionhardened Cu-0.092 wt % Cr-0.086 wt % Zr alloy has been investigated. It has been shown that the surfacelayer material of the alloy with a submicrocrystalline (SMC) structure obtained by the DCAP method can be strengthened using severe plastic deformation by sliding friction at the expense of creating a nanocrystalline structure with crystallites of 15-60 nm in size. It has been shown that the SMC structure obtained by the high strain-rate DCAP deformation decreases the wear rate of the samples upon sliding friction by a factor of 1.4 compared to the initial coarse-grained state. The maximum values of the microhardness and minimum values of the coefficient of friction and shear strength have been obtained in the samples preliminarily subjected to DCAP and aging at 400°C. The attained level of microhardness is 3350 MPa, which exceeds the microhardness of the alloy in the initial coarse-grained state by five times.

Effect of metallurgical structure and properties on adhesion and friction behavior of cobalt alloys

NASA Technical Reports Server (NTRS)

Keller, D. V., Jr.; Shatynski, S.; Vedamanikam, P. M.

1972-01-01

The metallurgical structure and some of the mechanical properties of two cobalt alloys, cobalt-50% iron and cobalt-25% molybdenum-10% chromium, were determined under various heat treated conditions. The mechanical properties of the bcc disordered Co-50Fe alloy, which was found to be very brittle, indicated an exceedingly low fracture strength, low hardness, and very weak grain boundary strength. Ordering by suitable heat treatment only produced a more brittle material with a lower fracture strength and a slightly higher hardness value. Work hardening was found to produce a finer grain structure and a greater grain boundary strength. Tensile properties were examined. It was found that the Co-25Mo-10Cr alloy was difficult to place in the alpha Co solid solution condition, which limited the ability to use precipitation as a hardening reaction. Over two hundred adhesion cycles from zero contact load, to maximum load, to fracture were conducted between couples for each of the above alloys in an ultrahigh vacuum system which would permit the sample surfaces to be cleaned of all contaminant layers. In the Co-50Fe case, the calculated fracture stress from the adhesion tests showed values in the range of 80 to 150 k.s.i., which is about ten times greater than the values from tension tests.

Structural and magnetic properties on the Fe-B-P-Cu-W nano-crystalline alloy system

NASA Astrophysics Data System (ADS)

Zhang, Yan; Wang, Yaocen; Makino, Akihiro

2018-04-01

In the present article, the structural and soft magnetic properties of Fe-B-P-Cu alloy system with W addition have been studied as well as the annealing configurations required for magnetic softness. It is found that the substitution of B by W deteriorates the soft magnetic properties after annealing. The reason of such impact with W addition may lie in the insufficient bonding strength between W and B so that the addition of W is not effective enough to suppress grain growth against the high concentration and high crystallization tendency of Fe during annealing. The addition of 4 at.% W is also found to reduce the saturation magnetization of the nano-crystalline alloy by 14%. It is also found that the addition of P in the Fe-based alloys could help reduce the coercivity upon annealing with high heating rate. The existence of P could also help slightly increase the overall saturation magnetization by enhancing the electron transfer away from Fe in the residual amorphous structure.

Local Structures of High-Entropy Alloys (HEAs) on Atomic Scales: An Overview

DOE PAGES

Diao, Haoyan; Santodonato, Louis J.; Tang, Zhi; ...

2015-08-29

The high-entropy alloys (HEAs), containing several elements mixed in equimolar or near-equimolar ratios, have shown exceptional engineering properties. Local structures on atomic level are essential to understand the mechanical behaviors and related mechanisms. In this paper, the local structure and stress on the atomic level are reviewed by the pair-distribution function (PDF) of neutron-diffraction data, ab-initio-molecular-dynamics (AIMD) simulations, and atomic-probe microscopy (APT).

Effect of mechanical alloying and heat treatment on the behavior of fe - 28% al - 5% cr powder with nanocrystalline structure

NASA Astrophysics Data System (ADS)

Tang, W. M.; Liu, H. L.; Wang, Y. X.; Xu, G. O.; Zheng, Z. X.

2012-05-01

Nanocrystalline powders of alloy Fe - 28% Al - 5% Cr (at.%) obtained by mechanical alloying from powdered iron, aluminum, and preliminarily alloyed Fe - 20% Cr are studied. The chemical composition is shown to be homogenized. The changes in the structure and in the morphology of the particles in the process of ball milling and subsequent heat treatment are determined. The alloying is shown to occur by the mechanism of continuous diffusion mixing.

The strainrange partitioning behavior of an advanced gas turbine disk alloy, AF2-1DA

NASA Technical Reports Server (NTRS)

Halford, G. R.; Nachtigall, A. J.

1979-01-01

The low-cycle, creep-fatigue characteristics of the advanced gas turbine disk alloy, AF2-1DA have been determined at 1400 F and are presented in terms of the method of strainrange partitioning (SRP). The mean stresses which develop in the PC and CP type SRP cycles at the lowest inelastic strainrange were observed to influence the cyclic lives to a greater extent than the creep effects and hence interfered with a conventional interpretation of the results by SRP. A procedure is proposed for dealing with the mean stress effects on life which is compatible with SRP.

Advanced nickel base alloys for high strength, corrosion applications

DOEpatents

Flinn, John E.

1998-01-01

Improved nickel-base alloys of enhanced strength and corrosion resistance, produced by atomization of an alloy melt under an inert gas atmosphere and of composition 0-20Fe, 10-30Cr, 2-12Mo, 6 max. Nb, 0.05-3 V, 0.08 max. Mn, 0.5 max. Si, less than 0.01 each of Al and Ti, less than 0.05 each of P and S, 0.01-0.08C, less than 0.2N, 0.1 max. 0, bal. Ni.

Comparison of the Fatigue Behavior of Copper Alloys

NASA Technical Reports Server (NTRS)

Lerch, Brad; Ellis, David

2006-01-01

This presentation is about the development of advanced copper alloys with high thermal conductivity, good creep strength, and adequate fatigue strength for rocket engine applications. It also focuses on the commercial availability of the advanced alloy-GRCop-84 developed at NASA-GRC. The presentation's conclusions are that GRCop-84 has equivalent or better isothermal fatigue lives compared to other commercially available copper alloys, that GRCop-84 can be fabricated in various forms with minimal change in the fatigue lives, that it is equivalent in sothermal, fatigue to AMZIRC at moderate temperatures, and that Narloy-Z is equivalent in fatigue capabilities to GRCop-84 at 400C and below.

Modification of the titanium alloy surface in electroexplosive alloying with boron carbide and subsequent electron-beam treatment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gromov, Victor E., E-mail: gromov@physics.sibsiu.ru; Budovskikh, Evgeniy A., E-mail: budovskikh-ea@physics.sibsiu.ru; Bashchenko, Lyudmila P., E-mail: gromov@physics.sibsiu.ru

2015-10-27

The modification of the VT6 titanium alloy surface in electroexplosion alloying with plasma being formed in titanium foil with a weighed powder of boron carbide with subsequent irradiation by a pulsed electron beam has been carried out. An electroexplosive alloying zone of a thickness up to 50 μm with a gradient structure is found to form. The subsequent electron-beam treatment of the alloying zone results in smoothing of the alloying surface and is accompanied by the formation of the multilayer structure with alternating layers of various alloying degree at a depth of 30 μm.

Cryogenic Fracture Toughness Evaluation of an Investment Cast Aluminum-Beryllium Alloy for Structural Applications

NASA Technical Reports Server (NTRS)

Gamwell, Wayne; McGill, Preston

2006-01-01

This document is a viewgraph presentation that details the fracture toughness of Aluminum-Beryllium Alloy for use in structures at cryogenic temperatures. Graphs and charts are presented in the presentation

Semiconductor structures having electrically insulating and conducting portions formed from an AlSb-alloy layer

DOEpatents

Spahn, O.B.; Lear, K.L.

1998-03-10

The semiconductor structure comprises a plurality of semiconductor layers formed on a substrate including at least one layer of a III-V compound semiconductor alloy comprising aluminum (Al) and antimony (Sb), with at least a part of the AlSb-alloy layer being chemically converted by an oxidation process to form superposed electrically insulating and electrically conducting portions. The electrically insulating portion formed from the AlSb-alloy layer comprises an oxide of aluminum (e.g., Al{sub 2}O{sub 3}), while the electrically conducting portion comprises Sb. A lateral oxidation process allows formation of the superposed insulating and conducting portions below monocrystalline semiconductor layers for forming many different types of semiconductor structures having particular utility for optoelectronic devices such as light-emitting diodes, edge-emitting lasers, vertical-cavity surface-emitting lasers, photodetectors and optical modulators (waveguide and surface normal), and for electronic devices such as heterojunction bipolar transistors, field-effect transistors and quantum-effect devices. The invention is expected to be particularly useful for forming light-emitting devices for use in the 1.3--1.6 {mu}m wavelength range, with the AlSb-alloy layer acting to define an active region of the device and to effectively channel an electrical current therein for efficient light generation. 10 figs.

Alloy-Based Anode Materials toward Advanced Sodium-Ion Batteries.

PubMed

Lao, Mengmeng; Zhang, Yu; Luo, Wenbin; Yan, Qingyu; Sun, Wenping; Dou, Shi Xue

2017-12-01

Sodium-ion batteries (SIBs) are considered as promising alternatives to lithium-ion batteries owing to the abundant sodium resources. However, the limited energy density, moderate cycling life, and immature manufacture technology of SIBs are the major challenges hindering their practical application. Recently, numerous efforts are devoted to developing novel electrode materials with high specific capacities and long durability. In comparison with carbonaceous materials (e.g., hard carbon), partial Group IVA and VA elements, such as Sn, Sb, and P, possess high theoretical specific capacities for sodium storage based on the alloying reaction mechanism, demonstrating great potential for high-energy SIBs. In this review, the recent research progress of alloy-type anodes and their compounds for sodium storage is summarized. Specific efforts to enhance the electrochemical performance of the alloy-based anode materials are discussed, and the challenges and perspectives regarding these anode materials are proposed. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Polyphase alloys as rechargeable electrodes in advanced battery systems

NASA Technical Reports Server (NTRS)

Huggins, Robert A.

1987-01-01

The rechargeability of electrochemical cells is often limited by negative electrode problems. These may include loss of capacity, increased impedance, macroscopic shape change, dendrite growth, or a tendency for filamentary or whisker growth. In principle, these problems can be reduced or eliminated by the use of alloys that undergo either displacement or insertion reactions at reactant species activities less than unity, rather than pure elements. The fundamental reasons for some of these problems with elemental electrodes, as well as the basic principles involved in the different behavior of alloys, are briefly discussed. More information is now available concerning the thermodynamic and kinetic properties of a number of alloys of potential interest for use as electrodes in elevated temperature lithium battery systems. Recent results have extended these results down to ambient temperatures, indicating that some such materials may be of interest for use with new low temperature molten salt electrolytes, or with organic solvent electrolytes. The all solid mixed conductor matrix concept is also reviewed.

Temperature Dependence of the Magnetization of the Ni52Mn24Ga24 Alloy in Various Structural States

NASA Astrophysics Data System (ADS)

Musabirov, I. I.; Sharipov, I. Z.; Mulyukov, R. R.

2015-10-01

are presented of a study of the temperature dependence of the magnetization σ(Т) of the polycrystalline Ni52Mn24Ga24 alloy in various structural states: in the initial coarse-grained state, after severe plastic deformation by high pressure torsion, and after stepped annealing of the deformed specimen at temperatures from 200 to 700°С for 30 min. As a study of the σ(Т) curve shows, in an alloy possessing a coarse-grained initial structure, a martensitic phase transition and a magnetic phase transition are observed in the room temperature interval. The martensitic transformation takes place in the ferromagnetic state of the alloy. This transformation is accompanied by an abrupt lowering of the magnetization of the material, associated with a lowering of the symmetry of the crystalline lattice and a high value of the magnetocrystalline anisotropy constant of the alloy in the martensitic phase. It is shown that as a result of plastic deformation there takes place a destruction of ferromagnetic order and a suppression of the martensitic transformation. Consecutive annealing after deformation leads to a gradual recovery of ferromagnetic order and growth of the magnetization of the material. Recovery of the martensitic transformation begins to be manifested only after annealing of the alloy at a temperature of 500°C, when the mean grain size in the recrystallized structure reaches a value around 1 μm.

Advanced nickel base alloys for high strength, corrosion applications

DOEpatents

Flinn, J.E.

1998-11-03

Improved nickel-base alloys of enhanced strength and corrosion resistance, produced by atomization of an alloy melt under an inert gas atmosphere and of composition 0--20Fe, 10--30Cr, 2--12Mo, 6 max. Nb, 0.05--3 V, 0.08 max. Mn, 0.5 max. Si, less than 0.01 each of Al and Ti, less than 0.05 each of P and S, 0.01--0.08C, less than 0.2N, 0.1 max. 0, bal. Ni. 3 figs.

A Fundamental Approach to Developing Aluminium based Bulk Amorphous Alloys based on Stable Liquid Metal Structures and Electronic Equilibrium - 154041

DTIC Science & Technology

2017-03-28

AFRL-AFOSR-JP-TR-2017-0027 A Fundamental Approach to Developing Aluminium-based Bulk Amorphous Alloys based on Stable Liquid -Metal Structures and...to 16 Dec 2016 4.  TITLE AND SUBTITLE A Fundamental Approach to Developing Aluminium-based Bulk Amorphous Alloys based on Stable Liquid -Metal...including Al, Cu, Ni, Zr, Mg, Pd, Ga , Ca. Many new Al-based amorphous alloys were found within the numerous alloy systems studied in this project, and

High-Temperature Alloys for Automotive Stirling Engines

NASA Technical Reports Server (NTRS)

Stephens, J. R.; Titran, R. H.

1986-01-01

Stirling engine is external-combustion engine that offers fuel economy, low emissions, low noise, and low vibrations. One of most critical areas in engine development concerns material selection for component parts. Alloys CG-27 and XF-818 identified capable of withstanding rigorous requirements of automotive Stirling engine. Alloys chosen for availability, performance, and manufacturability. Advanced iron-base alloys have potential for variety of applications, including stationary solar-power systems.

Correlation between thermal parameters, structures, dendritic spacing and corrosion behavior of Zn Al alloys with columnar to equiaxed transition

NASA Astrophysics Data System (ADS)

Ares, A. E.; Gassa, L. M.; Gueijman, S. F.; Schvezov, C. E.

2008-04-01

The columnar to equiaxed transition (CET) has been examined for many years and the significance of CET has been treated in several articles. Experimental observations in different alloy systems have shown that the position of the transition is dependent on parameters like cooling rate, velocity of the liquidus and solidus fronts, local solidification time, temperature gradients and recalescence. The dendritic structure in alloys results in microsegregation of solute species which affects significantly the mechanical properties of the material. The main parameters characterizing the microstructure and the length range of microsegregation is the spacing which is classified as primary, secondary and tertiary. Properties like mechanical resistance and ductility are influenced by the dimensions and continuity of the primary branches, while the secondary and tertiary branches permit the isolation of interdendritic phases which can deteriorate the mechanical behavior of the material. Since the morphology and dimensions of the dendritic structure is related to the solidification parameters mentioned above, for each type of alloy it is essential to correlate dimensions and solidification conditions in order to control the structure. The objective of the present research consists on studying the influence of solidification thermal parameters with the type of structure (columnar, equiaxial or with the CET); and with grain size and dendritic spacing (primary and secondary) in Zn-Al (ZA) alloys (Zn—4 wt%Al, Zn—16 wt%Al and Zn—27 wt%Al, weight percent). Also, correlate the thermal parameters, type of structure, grain size and dendritic spacing with the corrosion resistance of these alloys.

TERNARY ALLOY-CONTAINING PLUTONIUM

DOEpatents

Waber, J.T.

1960-02-23

Ternary alloys of uranium and plutonium containing as the third element either molybdenum or zirconium are reported. Such alloys are particularly useful as reactor fuels in fast breeder reactors. The alloy contains from 2 to 25 at.% of molybdenum or zirconium, the balance being a combination of uranium and plutonium in the ratio of from 1 to 9 atoms of uranlum for each atom of plutonium. These alloys are prepared by melting the constituent elements, treating them at an elevated temperature for homogenization, and cooling them to room temperature, the rate of cooling varying with the oomposition and the desired phase structure. The preferred embodiment contains 12 to 25 at.% of molybdenum and is treated by quenching to obtain a body centered cubic crystal structure. The most important advantage of these alloys over prior binary alloys of both plutonium and uranium is the lack of cracking during casting and their ready machinability.

Fracture characteristics of structural aerospace alloys containing deep surface flaws. [aluminum-titanium alloys

NASA Technical Reports Server (NTRS)

Masters, J. N.; Bixler, W. D.; Finger, R. W.

1973-01-01

Conditions controlling the growth and fracture of deep surface flaws in aerospace alloys were investigated. Static fracture tests were performed on 7075-T651 and 2219-T87 aluminum, and 6Ai-4V STA titanium . Cyclic flaw growth tests were performed on the two latter alloys, and sustain load tests were performed on the titanium alloy. Both the cyclic and the sustain load tests were performed with and without a prior proof overload cycle to investigate possible growth retardation effects. Variables included in all test series were thickness, flaw depth-to-thickness ratio, and flaw shape. Results were analyzed and compared with previously developed data to determine the limits of applicability of available modified linear elastic fracture solutions.

Development of oxide dispersion strengthened turbine blade alloy by mechanical alloying

NASA Technical Reports Server (NTRS)

Merrick, H. F.; Curwick, L. R. R.; Kim, Y. G.

1977-01-01

There were three nickel-base alloys containing up to 18 wt. % of refractory metal examined initially for oxide dispersion strengthening. To provide greater processing freedom, however, a leaner alloy was finally selected. This base alloy, alloy D, contained 0.05C/15Cr / 2Mo/4W/2Ta/4.5Al/2.Ti/015Zr/0.01-B/Bal. Ni. Following alloy selection, the effect of extrusion, heat treatment, and oxide volume fraction and size on microstructure and properties were examined. The optimum structure was achieved in zone annealed alloy D which contained 2.5 vol. % of 35 mm Y2O3 and which was extruded 16:1 at 1038 C.

Nano-sized Superlattice Clusters Created by Oxygen Ordering in Mechanically Alloyed Fe Alloys

NASA Astrophysics Data System (ADS)

Hu, Yong-Jie; Li, Jing; Darling, Kristopher A.; Wang, William Y.; Vanleeuwen, Brian K.; Liu, Xuan L.; Kecskes, Laszlo J.; Dickey, Elizabeth C.; Liu, Zi-Kui

2015-07-01

Creating and maintaining precipitates coherent with the host matrix, under service conditions is one of the most effective approaches for successful development of alloys for high temperature applications; prominent examples include Ni- and Co-based superalloys and Al alloys. While ferritic alloys are among the most important structural engineering alloys in our society, no reliable coherent precipitates stable at high temperatures have been found for these alloys. Here we report discovery of a new, nano-sized superlattice (NSS) phase in ball-milled Fe alloys, which maintains coherency with the BCC matrix up to at least 913 °C. Different from other precipitates in ferritic alloys, this NSS phase is created by oxygen-ordering in the BCC Fe matrix. It is proposed that this phase has a chemistry of Fe3O and a D03 crystal structure and becomes more stable with the addition of Zr. These nano-sized coherent precipitates effectively double the strength of the BCC matrix above that provided by grain size reduction alone. This discovery provides a new opportunity for developing high-strength ferritic alloys for high temperature applications.

Two phase titanium aluminide alloy

DOEpatents

Deevi, Seetharama C.; Liu, C. T.

2001-01-01

A two-phase titanic aluminide alloy having a lamellar microstructure with little intercolony structures. The alloy can include fine particles such as boride particles at colony boundaries and/or grain boundary equiaxed structures. The alloy can include alloying additions such as .ltoreq.10 at % W, Nb and/or Mo. The alloy can be free of Cr, V, Mn, Cu and/or Ni and can include, in atomic %, 45 to 55% Ti, 40 to 50% Al, 1 to 5% Nb, 0.3 to 2% W, up to 1% Mo and 0.1 to 0.3% B. In weight %, the alloy can include 57 to 60% Ti, 30 to 32% Al, 4 to 9% Nb, up to 2% Mo, 2 to 8% W and 0.02 to 0.08% B.

Structural health monitoring for DOT using magnetic shape memory alloy cables in concrete

NASA Astrophysics Data System (ADS)

Davis, Allen; Mirsayar, Mirmilad; Sheahan, Emery; Hartl, Darren

2018-03-01

Embedding shape memory alloy (SMA) wires in concrete components offers the potential to monitor their structural health via external magnetic field sensing. Currently, structural health monitoring (SHM) is dominated by acoustic emission and vibration-based methods. Thus, it is attractive to pursue alternative damage sensing techniques that may lower the cost or increase the accuracy of SHM. In this work, SHM via magnetic field detection applied to embedded magnetic shape memory alloy (MSMA) is demonstrated both experimentally and using computational models. A concrete beam containing iron-based MSMA wire is subjected to a 3-point bend test where structural damage is induced, thereby resulting in a localized phase change of the MSMA wire. Magnetic field lines passing through the embedded MSMA domain are altered by this phase change and can thus be used to detect damage within the structure. A good correlation is observed between the computational and experimental results. Additionally, the implementation of stranded MSMA cables in place of the MSMA wire is assessed through similar computational models. The combination of these computational models and their subsequent experimental validation provide sufficient support for the feasibility of SHM using magnetic field sensing via MSMA embedded components.

Thermostructural analysis of three structural concepts for reusable space vehicles

NASA Technical Reports Server (NTRS)

Taylor, A. H.; Jackson, L. R.

1979-01-01

Three structural concepts are studied: (1) a state-of-the-art insulated aluminum skin-stringer structure; (2) a near-art insulated evacuated aluminum-alloy honeycomb structure; and (3) an advanced evacuated Rene 41 honeycomb hot structure. Each is evaluated for its thermostructural performance for each of the flight profiles (ascent, entry, and a recall or abort). Results indicate that (1) the state-of-the-art structure encounters negligible thermal stress; (2) the near-art structure has acceptable thermal stresses; and (3) the advanced structure will have thermal stress levels above the material allowables.

Using heterostructural alloying to tune the structure and properties of the thermoelectric Sn 1–xCa xSe

DOE Office of Scientific and Technical Information (OSTI.GOV)

Matthews, Bethany E.; Holder, Aaron M.; Schelhas, Laura T.

We grow and kinetically stabilize the isotropic rocksalt phase of SnSe thin films by alloying SnSe with CaSe. Thin polycrystalline films of the metastable heterostructural alloy Sn 1–xCa xSe are synthesized by pulsed laser deposition on amorphous SiO 2 over the entire composition range 0 < x < 1. We observe the theoretically-predicted, composition-driven change from a layered, orthorhombic structure to an isotropic, cubic structure near x = 0.18, in reasonable agreement with the theoretical value of x = 0.13 calculated from first principles. The optical band gap is highly non-linear in x and the trend agrees with theory predictions.more » Compared to the layered end-member SnSe, the isotropic alloy near the orthorhombic-to-rocksalt transition has a p-type electrical resistivity three orders of magnitude lower, and a thermoelectric power factor at least ten times larger. Furthermore manipulation of the structure of a functional material like SnSe via alloying may provide a new path to enhanced functionality, in this case, improved thermoelectric performance.« less

Using heterostructural alloying to tune the structure and properties of the thermoelectric Sn 1–xCa xSe

DOE PAGES

Matthews, Bethany E.; Holder, Aaron M.; Schelhas, Laura T.; ...

2017-07-21

We grow and kinetically stabilize the isotropic rocksalt phase of SnSe thin films by alloying SnSe with CaSe. Thin polycrystalline films of the metastable heterostructural alloy Sn 1–xCa xSe are synthesized by pulsed laser deposition on amorphous SiO 2 over the entire composition range 0 < x < 1. We observe the theoretically-predicted, composition-driven change from a layered, orthorhombic structure to an isotropic, cubic structure near x = 0.18, in reasonable agreement with the theoretical value of x = 0.13 calculated from first principles. The optical band gap is highly non-linear in x and the trend agrees with theory predictions.more » Compared to the layered end-member SnSe, the isotropic alloy near the orthorhombic-to-rocksalt transition has a p-type electrical resistivity three orders of magnitude lower, and a thermoelectric power factor at least ten times larger. Furthermore manipulation of the structure of a functional material like SnSe via alloying may provide a new path to enhanced functionality, in this case, improved thermoelectric performance.« less

The effect of Mn and B on the magnetic and structural properties of nanostructured Fe60Al40 alloys produced by mechanical alloying.

PubMed

Rico, M M; Alcázar, G A Pérez; Zamora, L E; González, C; Greneche, J M

2008-06-01

The effect of Mn and B on the magnetic and structural properties of nanostructured samples of the Fe60Al40 system, prepared by mechanical alloying, was studied by 57Fe Mössbauer spectrometry, X-ray diffraction and magnetic measurements. In the case of the Fe(60-x)Mn(x)Al40 system, 24 h milling time is required to achieve the BCC ternary phase. Different magnetic structures are observed according to the temperature and the Mn content for alloys milled during 48 h: ferromagnetic, antiferromagnetic, spin-glass, reentrant spin-glass and superparamagnetic behavior. They result from the bond randomness behaviour induced by the atomic disorder introduced by the MA process and from the competitive interactions of the Fe-Fe ferromagnetic interactions and the Mn-Mn and Fe-Mn antiferromagnetic interactions and finally the presence of Al atoms acting as dilutors. When B is added in the Fe60Al40 alloy and milled for 12 and 24 hours, two crystalline phases were found: a prevailing FeAl BCC phase and a Fe2B phase type. In addition, one observes an additional contribution attributed to grain boundaries which increases when both milling time and boron composition increase. Finally Mn and B were added to samples of the Fe60Al40 system prepared by mechanical alloying during 12 and 24 hours. Mn content was fixed to 10 at.% and B content varied between 0 and 20 at.%, substituting Al. X-ray patterns show two crystalline phases, the ternary FeMnAl BCC phase, and a (Fe,Mn)2B phase type. The relative proportion of the last phase increases when the B content increases, in addition to changes of the grain size and the lattice parameter. Such behavior was observed for both milling periods. On the other hand, the magnetic hyperfine field distributions show that both phases exhibit chemical disorder, and that the contribution attributed to the grain boundaries is less important when the B content increases. Coercive field values of about 10(2) Oe slightly increase with boron content

Development of advanced fuel cell system, phase 2

NASA Technical Reports Server (NTRS)

Handley, L. M.; Meyer, A. P.; Bell, W. F.

1973-01-01

A multiple task research and development program was performed to improve the weight, life, and performance characteristics of hydrogen-oxygen alkaline fuel cells for advanced power systems. Development and characterization of a very stable gold alloy catalyst was continued from Phase I of the program. A polymer material for fabrication of cell structural components was identified and its long term compatibility with the fuel cell environment was demonstrated in cell tests. Full scale partial cell stacks, with advanced design closed cycle evaporative coolers, were tested. The characteristics demonstrated in these tests verified the feasibility of developing the engineering model system concept into an advanced lightweight long life powerplant.

Nickel aluminide alloy for high temperature structural use

DOEpatents

Liu, Chain T.; Sikka, Vinod K.

1991-01-01

The specification discloses nickel aluminide alloys including nickel, aluminum, chromium, zirconium and boron wherein the concentration of zirconium is maintained in the range of from about 0.05 to about 0.35 atomic percent to improve the ductility, strength and fabricability of the alloys at 1200.degree. C. Titanium may be added in an amount equal to about 0.2 to about 0.5 atomic percent to improve the mechanical properties of the alloys and the addition of a small amount of carbon further improves hot fabricability.

Manufacture of gradient micro-structures of magnesium alloys using two stage extrusion dies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hwang, Yeong-Maw; Huang, Tze-Hui; Alexandrov, Sergei

2013-12-16

This paper aims to manufacture magnesium alloy metals with gradient micro-structures using hot extrusion process. The extrusion die was designed to have a straight channel part combined with a conical part. Materials pushed through this specially-designed die generate a non-uniform velocity distribution at cross sections inside the die and result in different strain and strain rate distributions. Accordingly, a gradient microstructure product can be obtained. Using the finite element analysis, the forming temperature, effective strain, and effective strain rate distributions at the die exit were firstly discussed for various inclination angles in the conical die. Then, hot extrusion experiments withmore » a two stage die were conducted to obtain magnesium alloy products with gradient micro-structures. The effects of the inclination angle on the grain size distribution at cross sections of the products were also discussed. Using a die of an inclination angle of 15°, gradient micro-structures of the grain size decreasing gradually from 17 μm at the center to 4 μm at the edge of product were achieved.« less

Effects of Casting Conditions on the Structure and Magnetic Properties of the Co-19 at.%Al-6 at. %W Alloy

NASA Astrophysics Data System (ADS)

Kazantseva, N. V.; Stepanova, N. N.; Rigmant, M. B.; Davidov, D. I.; Shishkin, D. A.; Romanov, E. P.

The Co-19 at.%Al-6 at.%W alloy was prepared by two methods of casting. We used arc melting under an argon atmosphere with casting into a copper water-cooled casting mold and induction melting furnace with casting into a ceramic Al2O3 mold. According to the X-ray and SEM analyses, phase compositions depend on the cooling rate of the ingot after melting. After arc melting, the cast alloy has a three-phase structure, consisting of γ cobalt (FCC), intermetallic phases CoAl (B2) type, and Co3W (DO19) type. After the induction melting, the alloy has a three-phase structure, consisting of γ cobalt (FCC), intermetallic phases CoAl (B2) type, and Co7W6 (µ) type. All phases in the investigated ternary alloy at the room temperature are ferromagnetic. Curie temperatures of all obtained phases were defined. It is shown that the magnetic properties of the studied alloy are typical for soft magnetic materials.

URANIUM ALLOYS

DOEpatents

Seybolt, A.U.

1958-04-15

Uranium alloys containing from 0.1 to 10% by weight, but preferably at least 5%, of either zirconium, niobium, or molybdenum exhibit highly desirable nuclear and structural properties which may be improved by heating the alloy to about 900 d C for an extended period of time and then rapidly quenching it.

Life cycle assessment of metal alloys for structural applications

NASA Astrophysics Data System (ADS)

Malovrh Rebec, K.; Markoli, B.; Leskovar, B.

2018-03-01

The study compared environmental footprints of two types of Al-alloys: well-known 5083 aluminium alloy with magnesium and traces of manganese and chromium in its composition. This material is highly resistant to seawater corrosion and the influence of industrial chemicals. Furthermore, it retains exceptional strength after welding. The comparisons were made to an innovative alloy where the aluminium based matrix is reinforced by metastable quasicrystals (QC), thus avoiding magnesium in its composition. Furthermore, we checked other aluminium ingots’ footprints and compared European average and Germany country specific production data. Environmental footprints were assessed via cradle to gate life cycle assessment. Our findings normalized to 1 m2 plate suggest, that newly proposed alloy could save around 50 % in value of parameters abiotic resources depletion of fossil fuels, acidification, eutrophication, global warming potential and photochemical ozone creation potential if we compare Qc5 to 6 mm 5083 alloy plate. Only abiotic resources depletion of elements and ozone depletion parameters increase for Qc5 compared to 6 mm 5083 alloy plate.

Robust biomimetic-structural superhydrophobic surface on aluminum alloy.

PubMed

Li, Lingjie; Huang, Tao; Lei, Jinglei; He, Jianxin; Qu, Linfeng; Huang, Peiling; Zhou, Wei; Li, Nianbing; Pan, Fusheng

2015-01-28

The following facile approach has been developed to prepare a biomimetic-structural superhydrophobic surface with high stabilities and strong resistances on 2024 Al alloy that are robust to harsh environments. First, a simple hydrothermal treatment in a La(NO3)3 aqueous solution was used to fabricate ginkgo-leaf like nanostructures, resulting in a superhydrophilic surface on 2024 Al. Then a low-surface-energy compound, dodecafluoroheptyl-propyl-trimethoxylsilane (Actyflon-G502), was used to modify the superhydrophilic 2024 Al, changing the surface character from superhydrophilicity to superhydrophobicity. The water contact angle (WCA) of such a superhydrophobic surface reaches up to 160°, demonstrating excellent superhydrophobicity. Moreover, the as-prepared superhydrophobic surface shows high stabilities in air-storage, chemical and thermal environments, and has strong resistances to UV irradiation, corrosion, and abrasion. The WCAs of such a surface almost remain unchanged (160°) after storage in air for 80 days, exposure in 250 °C atmosphere for 24 h, and being exposed under UV irradiation for 24 h, are more than 144° whether in acidic or alkali medium, and are more than 150° after 48 h corrosion and after abrasion under 0.98 kPa for 1000 mm length. The remarkable durability of the as-prepared superhydrophobic surface can be attributed to its stable structure and composition, which are due to the existence of lanthanum (hydr)oxides in surface layer. The robustness of the as-prepared superhydrophobic surface to harsh environments will open their much wider applications. The fabricating approach for such robust superhydrophobic surface can be easily extended to other metals and alloys.

Fusion materials: Technical evaluation of the technology of vandium alloys for use as blanket structural materials in fusion power systems

NASA Astrophysics Data System (ADS)

1993-08-01

The Committee's evaluation of vanadium alloys as a structural material for fusion reactors was constrained by limited data and time. The design of the International Thermonuclear Experimental Reactor is still in the concept stage, so meaningful design requirements were not available. The data on the effect of environment and irradiation on vanadium alloys were sparse, and interpolation of these data were made to select the V-5Cr-5Ti alloy. With an aggressive, fully funded program it is possible to qualify a vanadium alloy as the principal structural material for the ITER blanket in the available 5 to 8-year window. However, the data base for V-5Cr-5Ti is limited and will require an extensive development and test program. Because of the chemical reactivity of vanadium the alloy will be less tolerant of system failures, accidents, and off-normal events than most other candidate blanket structural materials and will require more careful handling during fabrication of hardware. Because of the cost of the material more stringent requirements on processes, and minimal historical working experience, it will cost an order of magnitude to qualify a vanadium alloy for ITER blanket structures than other candidate materials. The use of vanadium is difficult and uncertain; therefore, other options should be explored more thoroughly before a final selection of vanadium is confirmed. The Committee views the risk as being too high to rely solely on vanadium alloys. In viewing the state and nature of the design of the ITER blanket as presented to the Committee, it is obvious that there is a need to move toward integrating fabrication, welding, and materials engineers into the ITER design team. If the vanadium alloy option is to be pursued, a large program needs to be started immediately. The commitment of funding and other resources needs to be firm and consistent with a realistic program plan.

Structural and morphological approach of Co-Cr dental alloys processed by alternative manufacturing technologies

NASA Astrophysics Data System (ADS)

Porojan, Sorin; Bîrdeanu, Mihaela; Savencu, Cristina; Porojan, Liliana

2017-08-01

The integration of digitalized processing technologies in traditional dental restorations manufacturing is an emerging application. The objective of this study was to identify the different structural and morphological characteristics of Co-Cr dental alloys processed by alternative manufacturing techniques in order to understand the influence of microstructure on restorations properties and their clinical behavior. Metallic specimens made of Co-Cr dental alloys were prepared using traditional casting (CST), and computerized milling (MIL), selective laser sintering (SLS) and selective laser melting (SLM). The structural information of the samples was obtained by X-ray diffraction, the morphology and the topography of the samples were investigated by Scanning Electron Microscopy and Atomic Force Microscope. Given that the microstructure was significantly different, further differences in the clinical behavior of prosthetic restorations manufactured using additive techniques are anticipated.

Advanced Gradient Heating Facility (AGHF)

NASA Technical Reports Server (NTRS)

1998-01-01

This section of the publication includes papers entitled: (1) Coupled growth in hypermonotectics; (2) Directional solidification of refined Al-4 wt.% Cu alloys; (3) Effects of convection on interface curvature during growth of concentrated ternary compounds; (4) Directional solidification of Al-1.5 wt.% Ni alloys; (5) Interactive response of advancing phase boundaries to particles; (6) INTeractive Response of Advancing Phase boundaries to Particles-INTRAPP; and (7) Particle engulfment and pushing by solidifying interfaces.

Electron Microscopic Study of the Structure of Tetragonal Martensite in In-4.5% Cd Alloy

NASA Astrophysics Data System (ADS)

Khlebnikova, Yu. V.; Egorova, L. Yu.; Rodionov, D. P.

2018-04-01

In this work, the formation of a packet structure composed of colonies of lamellar plates separated by twin boundary {101}fct in In-4.5 wt % Cd alloy upon cooling below the fcc → fct martensitic transition temperature has been shown using the methods of metallography, X-ray diffraction, transmission electron microscopy, and EBSD analysis. Two neighboring lamellae differ from each other by the direction of their tetragonality axes. Using EBSD analysis, it has been established that neighboring packets always contain three types of tetragonal martensite lamellae, which are in twin positions and differ from each other by the direction of their tetragonality axes. In turn, each martensite lamella consists of a set of smaller lamellae, which are in twin positions. After the cycle of fct → fcc → fct transitions, the alloy recrystallizes with a decrease in the grain size by several times compared with the initial structure such that the size of packets and the length and width of martensitic lamellae in a packet correlate with a change in the size of an alloy grain.

Shape memory alloys: a state of art review

NASA Astrophysics Data System (ADS)

Naresh, C.; Bose, P. S. C.; Rao, C. S. P.

2016-09-01

Shape memory alloys (SMAs) are the special materials that have the ability to return to a predetermined shape when heated. When this alloy is in below transformation temperature it undergoes low yield strength and will deform easily into any new shape which it will retain, if this alloy is heated above its transformation temperature it changes its crystal lattice structure which returns to its real shape. SMAs are remarkably different from other materials are primarily due to shape memory effect (SME) and pseudoelasticity which are related with the specific way the phase transformation occurs, biocompatibility, high specific strength, high corrosion resistance, high wear resistance and high anti-fatigue property. SMA are used in many applications such as aerospace, medical, automobile, tubes, controllers for hot water valves in showers, petroleum industry, vibration dampers, ball bearings, sensors, actuators, miniature grippers, micro valves, pumps, landing gears, eye glass frames, Material for helicopter blades, sprinklers in fine alarm systems packaging devices for electronic materials, dental materials, etc. This paper focuses on introducing shape memory alloy and their applications in past, present and in future, also revealed the concept and mechanism of shape memory materials for a particular requirement. Properties of SMAs, behaviour and characteristics of SMA, summary of recent advances and new application opportunities are also discussed.

Structural, electronic, magnetic, and transport properties of the equiatomic quaternary Heusler alloy CoRhMnGe: Theory and experiment

NASA Astrophysics Data System (ADS)

Rani, Deepika; Enamullah, Suresh, K. G.; Yadav, A. K.; Jha, S. N.; Bhattacharyya, D.; Varma, Manoj Raama; Alam, Aftab

2017-11-01

In this work, we present structural, electronic, magnetic, mechanical, and transport properties of equiatomic quaternary Heusler alloy, CoRhMnGe, using theoretical and experimental techniques. A detailed structural analysis is performed using x-ray diffraction and extended x-ray absorption fine structure spectroscopy. The alloy is found to crystallize in Y -type structure having space group F 4 ¯3 m (no. 216). The ab initio simulation predicts half-metallic ferromagnetic characteristics leading to large spin polarization. The calculated magnetization is found to be in fair agreement with experiment as well as those predicted by the Slater-Pauling rule, which is a prerequisite for half-metallicity. The magnetic transition temperature (TC) is found to be ˜760 K. Measured electrical resistivity in the temperature range 2-400 K also gives an indication of half-metallic behavior. Effect of hydrostatic pressure on electronic structure, magnetic, and mechanical properties are investigated in detail. The alloy is found to preserve half-metallic characteristics up to 30.27 GPa, beyond which it transits to metallic phase. No magnetic phase transition is found to occur in the whole range of pressure. The system also satisfies the Born-Huang criteria for mechanical stability up to a limited range of pressure. All these properties make the CoRhMnGe alloy promising for spintronics devices.

Effect of different annealing condition on the structural and magnetic properties of Mn2NiGa Heusler alloys

NASA Astrophysics Data System (ADS)

Vagadia, Megha; Hester, James; Nigam, A. K.

2018-04-01

We studied the effect of different annealing conditions on structural and magnetic properties of Mn2NiGa Heusler alloys. Reitveld refinement of neutron diffraction pattern at RT confirms the tetragonal structure with cubic phase for I-W quenched alloy whereas Le Bail fitting trials performed on neutron diffraction pattern collected for other three alloys confirm 7M monoclinic structure with cubic phase. It is found that starting and finish temperatures associated with martensite and austenite phase transformation depends strongly on the cooling rate corresponding to different cooling techniques. Slow furnace cooled sample possesses the highest martensite start temperature above room temperature ˜ 326K which decreases to ˜ 198K for ice -water quenched sample. Variation in the drop in the magnetization around MS obtained upon warming from martensite to austenite phase under ZFC cycle suggests that change in the cooling condition strongly affects the magnetization in the low temperature martensite phase. Present results suggest that by varying the cooling rate, martensite transformation as well as the martensite structure can be tuned.

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.

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

Aeronautical requirements for Inconel 718 alloy

NASA Astrophysics Data System (ADS)

Elefterie, C. F.; Guragata, C.; Bran, D.; Ghiban, B.

2017-06-01

The project goal is to present the requirements imposed by aviation components made from super alloys based on Nickel. A significant portion of fasteners, locking lugs, blade retainers and inserts are manufactured from Alloy 718. The thesis describes environmental factors (corrosion), conditions of external aggression (salt air, intense heat, heavy industrial pollution, high condensation, high pressure), mechanical characteristics (tensile strength, yield strength and fatigue resistance) and loadings (tensions, compression loads) that must be satisfied simultaneously by Ni-based super alloy, compared to other classes of aviation alloys (as egg. Titanium alloys, Aluminum alloys). For this alloy the requirements are strength durability, damage tolerance, fail safety and so on. The corrosion can be an issue, but the fatigue under high-magnitude cyclic tensile loading it’s what limits the lifetime of the airframe. Also, the excellent malleability and weldability characteristics of the 718 system make the material physical properties tolerant of manufacturing processes. These characteristics additionally continue to provide new opportunities for advanced manufacturing methods.

Deformation and Damage Studies for Advanced Structural Materials

NASA Technical Reports Server (NTRS)

2005-01-01

Advancements made in understanding deformation and damage of advanced structural materials have enabled the development of new technologies including the attainment of a nationally significant NASA Level 1 Milestone and the provision of expertise to the Shuttle Return to Flight effort. During this collaborative agreement multiple theoretical and experimental research programs, facilitating safe durable high temperature structures using advanced materials, have been conceived, planned, executed. Over 26 publications, independent assessments of structures and materials in hostile environments, were published within this agreement. This attainment has been recognized by 2002 Space Flight Awareness Team Award, 2004 NASA Group Achievement Award and 2003 and 2004 OAI Service Awards. Accomplishments in the individual research efforts are described as follows.

Aging Optimization of Aluminum-Lithium Alloy C458 for Application to Cryotank Structures

NASA Technical Reports Server (NTRS)

Sova, B. J.; Sankaran, K. K.; Babel, H.; Farahmand, B.; Rioja, R.

2003-01-01

Compared with aluminum alloys such as 2219, which is widely used in space vehicle for cryogenic tanks and unpressurized structures, aluminum-lithium alloys possess attractive combinations of lower density and higher modulus along with comparable mechanical properties. These characteristics have resulted in the successful use of the aluminum-lithium alloy 2195 (Al-1.0 Li-4.0 Cu-0.4 Mg-0.4 Ag-0.12 Zr) for the Space Shuttle External Tank, and the consideration of newer U.S. aluminum-lithium alloys such as L277 and C458 for future space vehicles. These newer alloys generally have lithium content less than 2 wt. % and their composition and processing have been carefully tailored to increase the toughness and reduce the mechanical property anisotropy of the earlier generation alloys such 2090 and 8090. Alloy processing, particularly the aging treatment, has a significant influence on the strength-toughness combinations and their dependence on service environments for aluminum-lithium alloys. Work at NASA Marshall Space Flight Center on alloy 2195 has shown that the cryogenic toughness can be improved by employing a two-step aging process. This is accomplished by aging at a lower temperature in the first step to suppress nucleation of the strengthening precipitate at sub-grain boundaries while promoting nucleation in the interior of the grains. Second step aging at the normal aging temperature results in precipitate growth to the optimum size. A design of experiments aging study was conducted for plate. To achieve the T8 temper, Alloy C458 (Al-1.8 Li-2.7 Cu-0.3 Mg-0.08 Zr-0.3 Mn-0.6 Zn) is typically aged at 300F for 24hours. In this study, a two-step aging treatment was developed through a comprehensive 2(exp 4) full factorial design of experiments study and the typical one-step aging used as a reference. Based on the higher lithium content of C458 compared with 2195, the first step aging temperature was varied between 175F and 250F. The second step aging temperatures was

Aging Optimization of Aluminum-Lithium Alloy C458 for Application to Cryotank Structures

NASA Technical Reports Server (NTRS)

Sova, B. J.; Sankaran, K. K.; Babel, H.; Farahmand, B.; Rioja, R.

2003-01-01

Compared with aluminum alloys such as 2219, which is widely used in space vehicle for cryogenic tanks and unpressurized structures, aluminum-lithium alloys possess attractive combinations of lower density and higher modulus along with comparable mechanical properties. These characteristics have resulted in the successful use of the aluminum-lithium alloy 2195 (Al-1.0 Li-4.0 Cu-0.4 Mg-0.4 Ag-0.12 Zr) for the Space Shuttle External Tank, and the consideration of newer U.S. aluminum-lithium alloys such as L277 and C458 for future space vehicles. These newer alloys generally have lithium content less than 2 wt. % and their composition and processing have been carefully tailored to increase the toughness and reduce the mechanical property anisotropy of the earlier generation alloys such 2090 and 8090. Alloy processing, particularly the aging treatment, has a significant influence on the strength-toughness combinations and their dependence on service environments for aluminum-lithium alloys. Work at NASA Marshall Space Flight Center on alloy 2195 has shown that the cryogenic toughness can be improved by employing a two-step aging process. This is accomplished by aging at a lower temperature in the first step to suppress nucleation of the strengthening precipitate at sub-grain boundaries while promoting nucleation in the interior of the grains. Second step aging at the normal aging temperature results in precipitate growth to the optimum size. A design of experiments aging study was conducted for plate. To achieve the T8 temper, Alloy C458 (Al-1.8 Li-2.7 Cu-0.3 Mg- 0.08 Zr-0.3 Mn-0.6 Zn) is typically aged at 300 F for 24 hours. In this study, a two-step aging treatment was developed through a comprehensive 24 full factorial design of experiments study and the typical one-step aging used as a reference. Based on the higher lithium content of C458 compared with 2195, the first step aging temperature was varied between 175 F and 250 F. The second step aging temperatures was

Atomistic Method Applied to Computational Modeling of Surface Alloys

NASA Technical Reports Server (NTRS)

Bozzolo, Guillermo H.; Abel, Phillip B.

2000-01-01

The formation of surface alloys is a growing research field that, in terms of the surface structure of multicomponent systems, defines the frontier both for experimental and theoretical techniques. Because of the impact that the formation of surface alloys has on surface properties, researchers need reliable methods to predict new surface alloys and to help interpret unknown structures. The structure of surface alloys and when, and even if, they form are largely unpredictable from the known properties of the participating elements. No unified theory or model to date can infer surface alloy structures from the constituents properties or their bulk alloy characteristics. In spite of these severe limitations, a growing catalogue of such systems has been developed during the last decade, and only recently are global theories being advanced to fully understand the phenomenon. None of the methods used in other areas of surface science can properly model even the already known cases. Aware of these limitations, the Computational Materials Group at the NASA Glenn Research Center at Lewis Field has developed a useful, computationally economical, and physically sound methodology to enable the systematic study of surface alloy formation in metals. This tool has been tested successfully on several known systems for which hard experimental evidence exists and has been used to predict ternary surface alloy formation (results to be published: Garces, J.E.; Bozzolo, G.; and Mosca, H.: Atomistic Modeling of Pd/Cu(100) Surface Alloy Formation. Surf. Sci., 2000 (in press); Mosca, H.; Garces J.E.; and Bozzolo, G.: Surface Ternary Alloys of (Cu,Au)/Ni(110). (Accepted for publication in Surf. Sci., 2000.); and Garces, J.E.; Bozzolo, G.; Mosca, H.; and Abel, P.: A New Approach for Atomistic Modeling of Pd/Cu(110) Surface Alloy Formation. (Submitted to Appl. Surf. Sci.)). Ternary alloy formation is a field yet to be fully explored experimentally. The computational tool, which is based on

Grain refinement of 7075Al alloy microstructures by inoculation with Al-Ti-B master alloy

NASA Astrophysics Data System (ADS)

Hotea, V.; Juhasz, J.; Cadar, F.

2017-05-01

This paper aims to bring some clarification on grain refinement and modification of high strength alloys used in aerospace technique. In this work it was taken into account 7075 Al alloy, and the melt treatment was carried out by placing in the form of master alloy wire ternary AlTiB the casting trough at 730°C. The morphology of the resulting microstructures was characterized by optical microscopy. Micrographs unfinished and finished with pre-alloy containing ternary Al5Ti1B evidence fine crystals, crystal containing no columnar structure and highlights the size of the dendrites, and intermetallic phases occurring at grain boundaries in Al-Zn-Mg-Cu alloy. It has been found that these intermetallic compounds are MgZn2 type. AlTiB master alloys finishing ensures a fine eutectic structure, which determines the properties of hardware and improving the mechanical properties of aluminum alloys used in aeronautical engineering.

Aging Optimization of Aluminum-Lithium Alloy L277 for Application to Cryotank Structures

NASA Technical Reports Server (NTRS)

Sova, B. J.; Sankaran, K. K.; Babel, H.; Farahmand, B.; Cho, A.

2003-01-01

Compared with aluminum alloys such as 2219, which is widely used in space vehicle for cryogenic tanks and unpressurized structures, aluminum-lithium alloys possess attractive combinations of lower density and higher modulus along with comparable mechanical properties and improved damage tolerance. These characteristics have resulted in the successful use of the aluminum-lithium alloy 2195 for the Space Shuttle External Tank, and the consideration of newer U.S. aluminum-lithium alloys such as L277 and C458 for future space vehicles. A design of experiments aging study was conducted for plate and a limited study on extrusions. To achieve the T8 temper, Alloy L277 is typically aged at 290 F for 40 hours. In the study for plate, a two-step aging treatment was developed through a design of experiments study and the one step aging used as a control. Based on the earlier NASA studies on 2195, the first step aging temperature was varied between 220 F and 260 F. The second step aging temperatures was varied between 290 F and 310 F, which is in the range of the single-step aging temperature. For extrusions, two, single-step, and one two-step aging condition were evaluated. The results of the design of experiments used for the T8 temper as well as a smaller set of experiments for the T6 temper for plate and the results for extrusions will be presented.

Electronic structure and glass forming ability in early and late transition metal alloys

NASA Astrophysics Data System (ADS)

Babić, E.; Ristić, R.; Figueroa, I. A.; Pajić, D.; Skoko, Ž.; Zadro, K.

2018-03-01

A correlation between the change in magnetic susceptibility (Δχexp) upon crystallisation of Cu-Zr and Hf metallic glasses (MG) with their glass forming ability (GFA) observed recently, is found to apply to Cu-Ti and Zr-Ni alloys, too. In particular, small Δχexp, which reflects similar electronic structures, ES, of glassy and corresponding crystalline alloys, corresponds to high GFA. Here, we studied Δχexp for five Cu-Ti and four Cu-Zr and Ni-Zr MGs. The fully crystalline final state of all alloys was verified from X-ray diffraction patterns. The variation of GFA with composition in Cu-Ti, Cu-Zr and Cu-Hf MGs was established from the variation of the corresponding critical casting thickness, dc. Due to the absence of data for dc in Ni-Zr MGs their GFA was described using empirical criteria, such as the reduced glass transition temperature. A very good correlation between Δχexp and dc (and/or other criteria for GFA) was observed for all alloys studied. The correlation between the ES and GFA showed up best for Cu-Zr and NiZr2 alloys where direct data for the change in ES (ΔES) upon crystallisation are available. The applicability of the Δχexp (ΔES) criterion for high GFA (which provides a simple way to select the compositions with high GFA) to other metal-metal MGs (including ternary and multicomponent bulk MGs) is briefly discussed.

Structure-Property Relations in Aluminum-Lithium Alloys

DTIC Science & Technology

1989-01-01

adsorbed ( Mughrabi et al , 1983). Such dislocations could not re-enter the grain during the reverse cycle of stress and the associated slip would be...ASTM STP 601, ASTM, 33 Mughrabi , H., Wang, R., Differt, D., Essmann, U. (1983) ASTM STP 811, ASTM, 5 Muller, W. et al (1986) Aluminium-Lithium Alloys...behaviour of Al -Li-Cu-Mg-Zr alloys ...... 34 2.4 Mechanical behaviour ......................................... 35 2.4.1 Elastic modulus

Superplastic Forming/Diffusion Bonding Without Interlayer of 5A90 Al-Li Alloy Hollow Double-Layer Structure

NASA Astrophysics Data System (ADS)

Jiang, Shaosong; Jia, Yong; Lu, Zhen; Shi, Chengcheng; Zhang, Kaifeng

2017-09-01

The hollow double-layer structure of 5A90 Al-Li alloy was fabricated by SPF/DB process in this study. The characteristics and mechanism of 5A90 Al-Li alloy with respect to superplasticity and diffusion bonding were investigated. Tensile tests showed that the optimal elongation of tensile specimens was 243.97% at the temperature of 400 °C and the strain rate of 0.001 s-1. Effect of the surface roughness, bonding temperature and bonding time to determine the microstructure and mechanical properties of diffusion bonding joints was investigated, and the optimum bonding parameters were 540 °C/2.5 h/Ra18. Through the finite element simulation, it could be found that the SPF/DB process of hollow double-layer structure was feasible. The hollow double-layer structure of 5A90 Al-Li alloy was manufactured, showing that the thickness distribution of the bonding area was uniform and the thinnest part was the round corner. The SEM images of diffusion bonding joints showed that sound bonding interfaces were obtained in which no discontinuity existed.

Effect of the Thermomechanical Treatment on Structural and Phase Transformations in Cu-14Al-3Ni Shape Memory Alloy Subjected to High-Pressure Torsion

NASA Astrophysics Data System (ADS)

Lukyanov, A. V.; Pushin, V. G.; Kuranova, N. N.; Svirid, A. E.; Uksusnikov, A. N.; Ustyugov, Yu. M.; Gunderov, D. V.

2018-04-01

The possibilities of controlling the structure and properties of a Cu-Al-Ni shape memory alloy due to the use of different schemes of the thermomechanical treatment, including forging, homogenizing in the austenitic state and subsequent quenching, and high-pressure torsion have been found. For the first time, an ultrafine-grain structure has been produced in this alloy via severe plastic deformation using high-pressure torsion. It has been detected that high-pressure torsion using ten revolutions of the anvils leads to the formation of a nanocrystalline structure with a grain size of less than 100 nm. The subsequent short-term heating of the alloy to 800°C (10 s) in the temperature region of the existence of the homogeneous β phase made it possible to form an ultrafine-grain structure with predominant sizes of recrystallized grains of 1 and 8 μm. The quenching after heating prevented the decomposition of the solid solution. The refinement of the grain structure changed the deformation behavior of the alloy, having provided the possibility of the significant plastic deformation upon mechanical tensile tests. The coarse-grained hot-forged quenched alloy was brittle, and fracture occurred along the boundaries of former austenite grains and martensite packets. The highstrength ultrafine-grained alloy also experienced mainly the intercrystalline fracture along the high-angle boundaries of elements of the structure, the grain size of which was less by two orders than that in the initial alloy. This determined an increase in its relative elongation upon mechanical tests.

Aluminum battery alloys

DOEpatents

Thompson, David S.; Scott, Darwin H.

1985-01-01

Aluminum alloys suitable for use as anode structures in electrochemical cs are disclosed. These alloys include iron levels higher than previously felt possible, due to the presence of controlled amounts of manganese, with possible additions of magnesium and controlled amounts of gallium.

Aluminum battery alloys

DOEpatents

Thompson, D.S.; Scott, D.H.

1984-09-28

Aluminum alloys suitable for use as anode structures in electrochemical cells are disclosed. These alloys include iron levels higher than previously felt possible, due to the presence of controlled amounts of manganese, with possible additions of magnesium and controlled amounts of gallium.

Temperature effect of elastic anisotropy and internal strain development in advanced nanostructured alloys: An in-situ synchrotron X-ray investigation

DOE PAGES

Gan, Yingye; Mo, Kun; Yun, Di; ...

2017-03-19

Nanostructured ferritic alloys (NFAs) are promising structural materials for advanced nuclear systems due to their exceptional radiation tolerance and high-temperature mechanical properties. Their remarkable properties result from the ultrafine ultrahigh density Y-Ti-O nanoclusters dispersed within the ferritic matrix. In this work, we performed in-situ synchrotron X-ray diffraction tests to study the tensile deformation process of the three types of NFAs: 9YWTV, 14YWT-sm13, and 14YWT-sm170 at both room temperature and elevated temperatures. A technique was developed, combining Kroner's model and X-ray measurement, to determine the intrinsic monocrystal elastic-stiffness constants, and polycrystal Young's modulus and Poisson's ratio of the NFAs. Temperature dependencemore » of elastic anisotropy was observed in the NFAs. Lastly, an analysis of intergranular strain and strengthening factors determined that 14YWT-sm13 had a higher resistance to temperature softening compared to 9YWTV, attributed to the more effective nanoparticle strengthening during high-temperature mechanical loading.« less

Shape memory alloys: Properties and biomedical applications

NASA Astrophysics Data System (ADS)

Mantovani, Diego

2000-10-01

Shape memory alloys provide new insights for the design of biomaterials in bioengineering for the design of artificial organs and advanced surgical instruments, since they have specific characteristics and unusual properties. This article will examine (a) the four properties of shape memory alloys, (b) medical applications with high potential for improving the present and future quality of life, and (c) concerns regarding the biocom-patibility properties of nickel-titanium alloys. In particular, the long-term challenges of using shape memory alloys will be discussed, regarding corrosion and potential leakage of elements and ions that could be toxic to cells, tissues and organs.

NASA-UVA Light Aerospace Alloy and Structure Technology Program Supplement: Aluminum-Based Materials for High Speed Aircraft

NASA Technical Reports Server (NTRS)

Starke, E. A., Jr.

1997-01-01

This is the final report of the study "Aluminum-Based Materials for High Speed Aircraft" which had the objectives (1) to identify the most promising aluminum-based materials with respect to major structural use on the HSCT and to further develop those materials and (2) to assess the materials through detailed trade and evaluation studies with respect to their structural efficiency on the HSCT. The research team consisted of ALCOA, Allied-Signal, Boeing, McDonnell Douglas, Reynolds Metals and the University of Virginia. Four classes of aluminum alloys were investigated: (1) I/M 2XXX containing Li and I/M 2XXX without Li, (2) I/M 6XXX, (3) two P/M 2XXX alloys, and (4) two different aluminum-based metal matrix composites (MMC). The I/M alloys were targeted for a Mach 2.0 aircraft and the P/M and MMC alloys were targeted for a Mach 2.4 aircraft. Design studies were conducted using several different concepts including skin/stiffener (baseline), honeycomb sandwich, integrally stiffened and hybrid adaptations (conventionally stiffened thin-sandwich skins). Alloy development included fundamental studies of coarsening behavior, the effect of stress on nucleation and growth of precipitates, and fracture toughness as a function of temperature were an integral part of this program. The details of all phases of the research are described in this final report.

Formation of soft magnetic high entropy amorphous alloys composites containing in situ solid solution phase

NASA Astrophysics Data System (ADS)

Wei, Ran; Sun, Huan; Chen, Chen; Tao, Juan; Li, Fushan

2018-03-01

Fe-Co-Ni-Si-B high entropy amorphous alloys composites (HEAACs), which containing high entropy solid solution phase in amorphous matrix, show good soft magnetic properties and bending ductility even in optimal annealed state, were successfully developed by melt spinning method. The crystallization phase of the HEAACs is solid solution phase with body centered cubic (BCC) structure instead of brittle intermetallic phase. In addition, the BCC phase can transformed into face centered cubic (FCC) phase with temperature rise. Accordingly, Fe-Co-Ni-Si-B high entropy alloys (HEAs) with FCC structure and a small amount of BCC phase was prepared by copper mold casting method. The HEAs exhibit high yield strength (about 1200 MPa) and good plastic strain (about 18%). Meanwhile, soft magnetic characteristics of the HEAs are largely reserved from HEAACs. This work provides a new strategy to overcome the annealing induced brittleness of amorphous alloys and design new advanced materials with excellent comprehensive properties.

Microstructural Evolution and Creep-Rupture Behavior of Fusion Welds Involving Alloys for Advanced Ultrasupercritical Power Generation

NASA Astrophysics Data System (ADS)

Bechetti, Daniel H., Jr.

Projections for large increases in the global demand for electric power produced by the burning of fossil fuels, in combination with growing environmental concerns surrounding these fuel sources, have sparked initiatives in the United States, Europe, and Asia aimed at developing a new generation of coal fired power plant, termed Advanced Ultrasupercritical (A-USC). These plants are slated to operate at higher steam temperatures and pressures than current generation plants, and in so doing will offer increased process cycle efficiency and reduced greenhouse gas emissions. Several gamma' precipitation strengthened Ni-based superalloys have been identified as candidates for the hottest sections of these plants, but the microstructural instability and poor creep behavior (compared to wrought products) of fusion welds involving these alloys present significant hurdles to their implementation and a gap in knowledge that must be addressed. In this work, creep testing and in-depth microstructural characterization have been used to provide insight into the long-term performance of these alloys. First, an investigation of the weld metal microstructural evolution as it relates to creep strength reductions in A-USC alloys INCONELRTM 740, NIMONICRTM 263 (INCONEL and NIMONIC are registered trademarks of Special Metals Corporation), and HaynesRTM 282RTM (Haynes and 282 are registered trademarks of Haynes International) was performed. gamma'-precipitate free zones were identified in two of these three alloys, and their development was linked to the evolution of phases that precipitate at the expense of gamma'. Alloy 282 was shown to avoid precipitate free zone formation because the precipitates that form during long term aging in this alloy are poor in the gamma'-forming elements. Next, the microstructural evolution of INCONELRTM 740H (a compositional variant of alloy 740) during creep was investigated. Gleeble-based interrupted creep and creep-rupture testing was used to

Formation of the structure and properties of an Mg-Al-Zn-Mn alloy during plastic deformation by rolling

NASA Astrophysics Data System (ADS)

Bozhko, S. A.; Betsofen, S. Ya.; Kolobov, Yu. R.; Vershinina, T. N.

2015-03-01

The laws of formation of an ultrafine structure in an Mg-Al-Zn-Mn alloy (MA5 alloy) under severe plastic deformation have been studied during lengthwise section rolling at a strain e = 1.59. The deformation behavior and the physical factors of anisotropy of yield strength during compression tests in various directions with respect to axis of rolling are analyzed. The role of crystallographic texture and twinning processes in the generation of strength processes and the development of plastic deformation of the alloy is analyzed.

High-temperature steam oxidation testing of select advanced replacement alloys for potential core internals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tan, Lizhen; Pint, Bruce A.

2017-05-19

Coupons from a total of fourteen commercial and custom fabricated alloys were exposed to 1 bar full steam with ~10 ppb oxygen content at 600 and 650°C. The coupons were weighed at 500-h intervals with a total exposure time of 5,000 h. The fourteen alloys are candidate alloys selected under the ARRM program, which include three ferritic steels (Grade 92, 439, and 14YWT), three austenitic stainless steels (316L, 310, and 800), seven Ni-base superalloys (X750, 725, C22, 690, 625, 625 direct-aging, and 625- plus), and one Zr-alloy (Zr–2.5Nb). Among the alloys, 316L and X750 are served as reference alloys formore » low- and high-strength alloys, respectively. The candidate Ni-base superalloy 718 was procured too late to be included in the tests. The corrosion rates of the candidate alloys can be approximately interpreted by their Cr, Ni and Fe content. The corrosion rate was significantly reduced with increasing Cr content and when Ni content is above ~15 wt%, but not much further reduced when Fe content is less than ~55 wt%. Simplified thermodynamics analyses of the alloy oxidation provided reasonable indications for the constituents of oxide scales formed on the alloys and explanations for the porosity and exfoliation phenomena because of the nature of specific types of oxides.« less

First-principles investigations on structural, elastic and mechanical properties of BNxAs1‑x ternary alloys

NASA Astrophysics Data System (ADS)

Zhang, Junqin; Ma, Huihui; Zhao, Bin; Wei, Qun; Yang, Yintang

2018-05-01

A systematic investigation of the structural optimization, elastic and mechanical properties of the BNxAs1‑x ternary alloys are reported in the present work using the density-functional theory with the generalized gradient approximation (GGA) of the exchange-correlation functional. Some of the constants which are used to analyze the properties including elastic constants and modulus, and some parameters describing the elastic anisotropy and Debye temperature are also calculated. Our calculations were performed to evaluate the equilibrium lattice constant and band structure compared with the available theoretical works. On the one hand, our results might be expected to provide a theoretical basis for future study of BNxAs1‑x alloys towards elastic or mechanical properties. On the other hand, we draw a conclusion that BNxAs1‑x alloys show direct bandgap when x equals 0.25, 0.5 or 0.75. We obtained the elastic modulus, Poisson’s ratio and universal anisotropic index which are used to demonstrate the elastic anisotropy of these alloys which is proved according to our calculations. Also, we calculated the Debye temperature to illustrate covalent interactions and obtained the lower limit of the thermal conductivity for further research.

Evolution of the Structural-Phase State of a Ti-Al- V-Mo Alloy During Severe Plastic Deformation and SubSequent Annealing

NASA Astrophysics Data System (ADS)

Grabovetskaya, G. P.; Ratochka, I. V.; Mishin, I. P.; Zabudchenko, O. V.; Lykova, O. N.

2016-05-01

The effect of the initial phase composition of a Ti-Al-V-Mo alloy (VT16 according to Russian classification) on the evolution of its structural-phase state during the formation of ultrafine-grained structure and subsequent annealing is investigated by methods of optical and transmission electron microscopy and x-ray diffraction analysis. The structure is produced by cyclic pressing with a change of the deformation axis in each cycle combined with a gradual decrease of the pressing temperature from 1073 to 723 K. As this takes place, α″ → α + β and β → α phase transitions are found to develop in the test alloy. The phase state of the ultrafinegrained material thus produced depends for the most part on its elemental composition and severe plastic deformation regime. Annealing below the recrystallization temperature is shown to give rise to a β→α phase transition and alloying element redistribution. The foregoing processes allow for retaining a high level of the strength properties of the alloy.

Theoretical investigation of structural, mechanical and electronic properties of GaAs1-xNx alloys under ambient and high pressure

NASA Astrophysics Data System (ADS)

Li, Jian; Han, Xiuxun; Dong, Chen; Fan, Changzeng

2017-12-01

Using first-principles total energy calculations, we have studied the structural, mechanical and electronic properties of GaAs1-xNx ternary semiconductor alloys with the zinc-blende crystal structure over the whole nitrogen concentration range (with x from 0 to 1) within density functional theory (DFT) framework. To obtain the ideal band gap, we employ the semi-empirical approach called local density approximation plus the multi-orbital mean-field Hubbard model (LDA+U). The calculated results illustrate the varying lattice constants and band gap in GaAs1-xNx alloys as functions of the nitrogen concentration x. According to the pressure dependence of the lattice constants and volume, the higher N concentration alloy exhibits the better anti-compressibility. In addition, an increasing band gap is predicted under 20 GPa pressure for GaAs1-xNx alloys.

Evaluation of a Gamma Titanium Aluminide for Hypersonic Structural Applications

NASA Technical Reports Server (NTRS)

Johnson, W. Steven; Weeks, Carrell E.

2005-01-01

Titanium matrix composites (TMCs) have been extensively evaluated for their potential to replace conventional superalloys in high temperature structural applications, with significant weight-savings while maintaining comparable mechanical properties. New gamma titanium aluminide alloys and an appropriate fiber could offer an improved TMC for use in intermediate temperature applications (400-800 C). The purpose of this investigation is the evaluation of a gamma titanium aluminide alloy with nominal composition Ti-46.5Al-4(Cr,Nb,Ta,B)at.% as a structural material in future aerospace transportation systems, where very light-weight structures are necessary to meet the goals of advanced aerospace programs.

NASA-427: A New Aluminum Alloy

NASA Technical Reports Server (NTRS)

Nabors, Sammy A.

2015-01-01

NASA's Marshall Space Flight Center researchers have developed a new, stronger aluminum alloy, ideal for cast aluminum products that have powder or paint-baked thermal coatings. With advanced mechanical properties, the NASA-427 alloy shows greater tensile strength and increased ductility, providing substantial improvement in impact toughness. In addition, this alloy improves the thermal coating process by decreasing the time required for heat treatment. With improvements in both strength and processing time, use of the alloy provides reduced materials and production costs, lower product weight, and better product performance. The superior properties of NASA-427 can benefit many industries, including automotive, where it is particularly well-suited for use in aluminum wheels.

Elevated temperature crack growth in advanced powder metallurgy aluminum alloys

NASA Technical Reports Server (NTRS)

Porr, William C., Jr.; Gangloff, Richard P.

1990-01-01

Rapidly solidified Al-Fe-V-Si powder metallurgy alloy FVS0812 is among the most promising of the elevated temperature aluminum alloys developed in recent years. The ultra fine grain size and high volume fraction of thermally stable dispersoids enable the alloy to maintain tensile properties at elevated temperatures. In contrast, this alloy displays complex and potentially deleterious damage tolerant and time dependent fracture behavior that varies with temperature. J-Integral fracture mechanics were used to determine fracture toughness (K sub IC) and crack growth resistance (tearing modulus, T) of extruded FVS0812 as a function of temperature. The alloy exhibits high fracture properties at room temperature when tested in the LT orientation, due to extensive delamination of prior ribbon particle boundaries perpendicular to the crack front. Delamination results in a loss of through thickness constraint along the crack front, raising the critical stress intensity necessary for precrack initiation. The fracture toughness and tensile ductility of this alloy decrease with increasing temperature, with minima observed at 200 C. This behavior results from minima in the intrinsic toughness of the material, due to dynamic strain aging, and in the extent of prior particle boundary delaminations. At 200 C FVS0812 fails at K levels that are insufficient to cause through thickness delamination. As temperature increases beyond the minimum, strain aging is reduced and delamination returns. For the TL orientation, K (sub IC) decreased and T increased slightly with increasing temperature from 25 to 316 C. Fracture in the TL orientation is governed by prior particle boundary toughness; increased strain localization at these boundaries may result in lower toughness with increasing temperature. Preliminary results demonstrate a complex effect of loading rate on K (sub IC) and T at 175 C, and indicate that the combined effects of time dependent deformation, environment, and strain aging

High performance alloy electroforming

NASA Technical Reports Server (NTRS)

Malone, G. A.; Winkelman, D. M.

1989-01-01

Electroformed copper and nickel are used in structural applications for advanced propellant combustion chambers. An improved process has been developed by Bell Aerospace Textron, Inc. wherein electroformed nickel-manganese alloy has demonstrated superior mechanical and thermal stability when compared to previously reported deposits from known nickel plating processes. Solution chemistry and parametric operating procedures are now established and material property data is established for deposition of thick, large complex shapes such as the Space Shuttle Main Engine. The critical operating variables are those governing the ratio of codeposited nickel and manganese. The deposition uniformity which in turn affects the manganese concentration distribution is affected by solution resistance and geometric effects as well as solution agitation. The manganese concentration in the deposit must be between 2000 and 3000 ppm for optimum physical properties to be realized. The study also includes data regarding deposition procedures for achieving excellent bond strength at an interface with copper, nickel-manganese or INCONEL 718. Applications for this electroformed material include fabrication of complex or re-entry shapes which would be difficult or impossible to form from high strength alloys such as INCONEL 718.

NASA-UVa light aerospace alloy and structure technology program supplement: Aluminum-based materials for high speed aircraft

NASA Technical Reports Server (NTRS)

Starke, E. A., Jr.

1993-01-01

This report on the NASA-UVa Light Aerospace Alloy and Structure Technology Program Supplement: Aluminum-Based Materials for High Speed Aircraft covers the period from January 1, 1992 to June 30, 1992. The objective of the research is to develop aluminum alloys and aluminum matrix composites for the airframe which can efficiently perform in the HSCT environment for periods as long as 60,000 hours (certification for 120,000 hours) and, at the same time, meet the cost and weight requirements for an economically viable aircraft. Current industry baselines focus on flight at Mach 2.4. The research covers four major materials systems: (1) ingot metallurgy 2XXX, 6XXX, and 8XXX alloys, (2) powder metallurgy 2XXX alloys, (3) rapidly solidified, dispersion strengthened Al-Fe-X alloys, and (4) discontinuously reinforced metal matrix composites. There are ten major tasks in the program which also include evaluation and trade-off studies by Boeing and Douglas aircraft companies.

NASA-UVa light aerospace alloy and structures technology program supplement: Aluminum-based materials for high speed aircraft

NASA Technical Reports Server (NTRS)

Starke, E. A., Jr. (Editor)

1995-01-01

This report on the NASA-UVa light aerospace alloy and structure technology program supplement: Aluminum-Based Materials for High Speed Aircraft covers the period from July 1, 1992. The objective of the research is to develop aluminum alloys and aluminum matrix composites for the airframe which can efficiently perform in the HSCT environment for periods as long as 60,000 hours (certification for 120,000 hours) and, at the same time, meet the cost and weight requirements for an economically viable aircraft. Current industry baselines focus on flight at Mach 2.4. The research covers four major materials systems: (1) Ingot metallurgy 2XXX, 6XXX, and 8XXX alloys, (2) Powder metallurgy 2XXX alloys, (3) Rapidly solidified, dispersion strengthened Al-Fe-X alloys, and (4) Discontinuously reinforced metal matrix composites. There are ten major tasks in the program which also include evaluation and trade-off studies by Boeing and Douglas aircraft companies.

Structure, mechanical characteristics and in vitro degradation, cytotoxicity, genotoxicity and mutagenicity of novel biodegradable Zn-Mg alloys.

PubMed

Kubásek, J; Vojtěch, D; Jablonská, E; Pospíšilová, I; Lipov, J; Ruml, T

2016-01-01

Zn-(0-1.6)Mg (in wt.%) alloys were prepared by hot extrusion at 300 °C. The structure, mechanical properties and in vitro biocompatibility of the alloys were investigated. The hot-extruded magnesium-based WE43 alloy was used as a control. Mechanical properties were evaluated by hardness, compressive and tensile testing. The cytotoxicity, genotoxicity (comet assay) and mutagenicity (Ames test) of the alloy extracts and ZnCl2 solutions were evaluated with the use of murine fibroblasts L929 and human osteosarcoma cell line U-2 OS. The microstructure of the Zn alloys consisted of recrystallized Zn grains of 12 μm in size and fine Mg2Zn11 particles arranged parallel to the hot extrusion direction. Mechanical tests revealed that the hardness and strength increased with increasing Mg concentration. The Zn-0.8 Mg alloys showed the best combination of tensile mechanical properties (tensile yield strength of 203 MPa, ultimate tensile strength of 301 MPa and elongation of 15%). At higher Mg concentrations the plasticity of Zn-Mg alloys was deteriorated. Cytotoxicity tests with alloy extracts and ZnCl2 solutions proved the maximum safe Zn(2+) concentrations of 120 μM and 80 μM for the U-2 OS and L929 cell lines, respectively. Ames test with extracts of alloys indicated that the extracts were not mutagenic. The comet assay demonstrated that 1-day extracts of alloys were not genotoxic for U-2 OS and L929 cell lines after 1-day incubation. Copyright © 2015 Elsevier B.V. All rights reserved.

Effect of Cooling Rate and Chemical Modification on the Tensile Properties of Mg-5wt% Si Alloy

NASA Astrophysics Data System (ADS)

Mirshahi, Farshid; Meratian, Mahmood; Zahrani, Mohsen Mohammadi; Zahrani, Ehsan Mohammadi

Hypereutectic Mg-Si alloys are a new class of light materials usable for aerospace and other advanced engineering applications. In this study, the effects of both cooling rate and bismuth modification on the micro structure and tensile properties of hypereutectic Mg-5wt% Si alloy were investigated. It was found that the addition of 0.5% Bi, altered the morphology of primary Mg2Si particles from bulky to polygonal shape and reduced their mean size from more than 70 μm to about 30 (am. Also, the tensile strength and elongation of the modified alloy increased about 10% and 20%, respectively, which should be ascribed to the modification of Mg2Si morphology and more uniform distribution of the primary particles. Moreover, an increase in tensile strength value with increase in cooling rate were observed which is attributed to finer micro structure of alloy in higher cooling rates. It was observed that Bi addition is significantly more effective in refining the morphology of primary Mg2Si particles than applying faster cooling rates.

Molecular dynamics simulation of liquid structure for undercooled Zr-Nb alloys assisted with electrostatic levitation experiments

NASA Astrophysics Data System (ADS)

Yang, S. J.; Hu, L.; Wang, L.; Wei, B.

2018-06-01

The liquid structures of undercooled Zr90Nb10, Zr70Nb30 and Zr50Nb50 alloys were studied by molecular dynamics simulation combined with electrostatic levitation experiments. The densities of three alloys were measured by electrostatic levitation to modify the Zr-Nb potential functions by adjusting parameters in potential functions. In simulation, the atomic packing in Zr-Nb alloys was more ordered at lower temperatures. The Voronoi tessellation analyses indicated Nb-centered clusters were easier to form than Zr-centered clusters although the Nb content was less than 50%. The partial pair distribution functions showed that the interactions among Zr atoms are quite different to that among Nb atoms.

YF-12 Lockalloy ventral fin program, volume 1. [design analysis, fabrication, and manufacturing of aircraft structures using aluminum and beryllium alloys for the lockheed YF-12 aircraft

NASA Technical Reports Server (NTRS)

Duba, R. J.; Haramis, A. C.; Marks, R. F.; Payne, L.; Sessing, R. C.

1976-01-01

Results are presented of the YF-12 Lockalloy Ventral Fin Program which was carried out by Lockheed Aircraft Corporation - Advanced Development Projects for the joint NASA/USAF YF-12 Project. The primary purpose of the program was to redesign and fabricate the ventral fin of the YF-12 research airplane (to reduce flutter) using Lockalloy, and alloy of beryllium and aluminum, as a major structural material. A secondary purpose, was to make a material characterization study (thermodynamic properties, corrosion; fatigue tests, mechanical properties) of Lockalloy to validate the design of the ventral fin and expand the existing data base on this material. All significant information pertinent to the design and fabrication of the ventral fin is covered. Emphasis throughout is given to Lockalloy fabrication and machining techniques and attendant personnel safety precautions. Costs are also examined. Photographs of tested alloy specimens are shown along with the test equipment used.

Study of structural phase transitions in quinary TiNi(MoFeAg)-based alloys

NASA Astrophysics Data System (ADS)

Gunther, Victor; Marchenko, Ekaterina; Chekalkin, Timofey; Baigonakova, Gulsharat; Kang, Ji-hoon; Kim, Ji-soon; Klopotov, Anatoliy

2017-10-01

The structural phase transitions of quinary Ti50Ni49.5-X Mo0.3Fe0.2Ag X (X  =  0, 0.1, 0.2, 0.5, 1.0, and 1.5 at%) alloys prepared by vacuum-induction melting were studied by means of the four-point-probe, x-ray diffraction (XRD), and optical microscopy methods after thermal cycling. The two-stage B2 ↔ R ↔ B19‧ reversible martensitic transformation (MT) took place in all the investigated samples. It is found that the substitution of Ag for Ni in the studied alloy when C Ag  =  0-0.5 at%, reduces the T R, M s, and M f characteristic points by 20-30 K, whereas they increase by 15-35 K when the Ag content was varied from 1.0 to 1.5 at% and the B2 ↔ R ↔ B19‧ MT was realized in the high-temperature area. XRD patterns of the studied alloys recorded at the ambient temperature detected the pure Ag phase as well as Ti2Ni precipitate with a small volume fraction (up to 5%) alongside with structural lines of B2, R, and B19‧ phases.

Resistance of a directionally solidified gamma/gamma prime-delta eutectic alloy to recrystallization. [Ni-base alloy

NASA Technical Reports Server (NTRS)

Tewari, S. N.; Scheuermann, C. M.; Andrews, C. W.

1976-01-01

A lamellar nickel-base directionally-solidified eutectic gamma/gamma prime-delta alloy has potential as an advanced gas turbine blade material. The microstructural stability of this alloy was investigated. Specimens were plastically deformed by uniform compression or Brinell indentation, then annealed between 750 and 1120 C. Microstructural changes observed after annealing included gamma prime coarsening, pinch-off and spheroidization of delta lamellae, and appearance of an unidentified blocky phase in surface layers. All but the first of these was localized in severely deformed regions, suggesting that microstructural instability may not be a serious problem in the use of this alloy.

Effect of stoichiometry and Cu-substitution on the phase structure and hydrogen storage properties of Ml-Mg-Ni-based alloys

NASA Astrophysics Data System (ADS)

Li, Yuan; Tao, Yang; Huo, Quan

2015-01-01

To improve the electrochemical properties of rare-earth-Mg-Ni-based hydrogen storage alloys, the effects of stoichiometry and Cu-substitution on the phase structure and thermodynamic properties of the alloys were studied. Nonsubstituted Ml0.80Mg0.20(Ni2.90Co0.50-Mn0.30Al0.30) x ( x = 0.68, 0.70, 0.72, 0.74, 0.76) alloys and Cu-substituted Ml0.80Mg0.20(Ni2.90Co0.50- y Cu y Mn0.30Al0.30)0.70 ( y = 0, 0.10, 0.30, 0.50) alloys were prepared by induction melting. Phase structure analysis shows that the nonsubstituted alloys consist of a LaNi5 phase, a LaNi3 phase, and a minor La2Ni7 phase; in addition, in the case of Cu-substitution, the Nd2Ni7 phase appears and the LaNi3 phase vanishes. Thermodynamic tests show that the enthalpy change in the dehydriding process decreases, indicating that hydride stability decreases with increasing stoichiometry and increasing Cu content. The maximum discharge capacity, kinetic properties, and cycling stability of the alloy electrodes all increase and then decrease with increasing stoichiometry or increasing Cu content. Furthermore, Cu substitution for Co ameliorates the discharge capacity, kinetics, and cycling stability of the alloy electrodes.

The hydrogen embrittlement of titanium-based alloys

NASA Astrophysics Data System (ADS)

Tal-Gutelmacher, Ervin; Eliezer, Dan

2005-09-01

Titanium-based alloys provide an excellent combination of a high strength/weight ratio and good corrosion behavior, which makes these alloys among the most important advanced materials for a variety of aerospace, marine, industrial, and commercial applications. Although titanium is considered to be reasonably resistant to chemical attack, severe problems can arise when titanium-based alloys come in contact with hydrogen-containing environments, where they can pick up large amounts of hydrogen, especially at elevated temperatures. The severity and the extent of the hydrogen interaction with titanium-based alloys are directly related to the microstructure and composition of the titanium alloys. This paper addresses the hydrogen embrittlement of titanium-based alloys. The hydrogen-titanium interaction is reviewed, including the solubility of hydrogen in α and β phases of titanium and hydride formation. Also, the paper summarizes the detrimental effects of hydrogen in different titanium alloys.

Measuring the Thermodynamics of the Alloy/Scale Interface

NASA Technical Reports Server (NTRS)

Copland, Evan

2004-01-01

A method is proposed for the direct measurement of the thermodynamic properties of the alloy and oxide compound at the alloy/scale interface observed during steady-state oxidation. The thermodynamic properties of the alloy/scale interface define the driving force for solid-state transport in the alloy and oxide compound. Accurate knowledge of thermodynamic properties of the interface will advance our understanding of oxidation behavior. The method is based on the concept of local equilibrium and assumes that an alloy+scale equilibrium very closely approximates the alloy/scale interface observed during steady-state oxidation. The thermodynamics activities of this alloy+scale equilibrium are measured directly by Knudsen effusion-cell mass spectrometer (KEMS) using the vapor pressure technique. The theory and some practical considerations of this method are discussed in terms of beta-NiAl oxidation.

Applications of high-temperature powder metal aluminum alloys to small gas turbines

NASA Technical Reports Server (NTRS)

Millan, P. P., Jr.

1982-01-01

A program aimed at the development of advanced powder-metallurgy (PM) aluminum alloys for high-temperature applications up to 650 F using the concepts of rapid solidification and mechanical alloying is discussed. In particular, application of rapidly solidified PM aluminum alloys to centrifugal compressor impellers, currently used in auxiliary power units for both military and commercial aircraft and potentially for advanced automotive gas turbine engines, is examined. It is shown that substitution of high-temperature aluminum for titanium alloy impellers operating in the 360-650 F range provides significant savings in material and machining costs and results in reduced component weight, and consequently, reduced rotating group inertia requirements.

Helium sequestration at nanoparticle-matrix interfaces in helium + heavy ion irradiated nanostructured ferritic alloys

DOE PAGES

Parish, Chad M.; Unocic, Kinga A.; Tan, Lizhen; ...

2016-10-24

Here we irradiated four ferritic alloys with energetic Fe and He ions: one castable nanostructured alloy (CNA) containing Ti-W-Ta-carbides, and three nanostructured ferritic alloys (NFAs). The NFAs were: 9Cr containing Y-Ti-O nanoclusters, and two Fe-12Cr-5Al NFAs containing Y-Zr-O or Y-Hf-O clusters. All four were subjected to simultaneous dual-beam Fe + He ion implantation (650 °C, ~50 dpa, ~15 appm He/dpa), simulating fusion-reactor conditions. Examination using scanning/transmission electron microscopy (STEM) revealed high-number-density helium bubbles of ~8 nm, ~10 21 m -3 (CNA), and of ~3 nm, 10 23 m -3 (NFAs). STEM combined with multivariate statistical analysis data mining suggests thatmore » the precipitate-matrix interfaces in all alloys survived ~50 dpa at 650 °C and serve as effective helium trapping sites. All alloys appear viable structural material candidates for fusion or advanced fission energy systems. Finally, among these developmental alloys the NFAs appear to sequester the helium into smaller bubbles and away from the grain boundaries more effectively than the early-generation CNA.« less

The Effect of Electronic Structure on the Phases Present in High Entropy Alloys

PubMed Central

Leong, Zhaoyuan; Wróbel, Jan S.; Dudarev, Sergei L.; Goodall, Russell; Todd, Iain; Nguyen-Manh, Duc

2017-01-01

Multicomponent systems, termed High Entropy Alloys (HEAs), with predominantly single solid solution phases are a current area of focus in alloy development. Although different empirical rules have been introduced to understand phase formation and determine what the dominant phases may be in these systems, experimental investigation has revealed that in many cases their structure is not a single solid solution phase, and that the rules may not accurately distinguish the stability of the phase boundaries. Here, a combined modelling and experimental approach that looks into the electronic structure is proposed to improve accuracy of the predictions of the majority phase. To do this, the Rigid Band model is generalised for magnetic systems in prediction of the majority phase most likely to be found. Good agreement is found when the predictions are confronted with data from experiments, including a new magnetic HEA system (CoFeNiV). This also includes predicting the structural transition with varying levels of constituent elements, as a function of the valence electron concentration, n, obtained from the integrated spin-polarised density of states. This method is suitable as a new predictive technique to identify compositions for further screening, in particular for magnetic HEAs. PMID:28059106

The Effect of Electronic Structure on the Phases Present in High Entropy Alloys.

PubMed

Leong, Zhaoyuan; Wróbel, Jan S; Dudarev, Sergei L; Goodall, Russell; Todd, Iain; Nguyen-Manh, Duc

2017-01-06

Multicomponent systems, termed High Entropy Alloys (HEAs), with predominantly single solid solution phases are a current area of focus in alloy development. Although different empirical rules have been introduced to understand phase formation and determine what the dominant phases may be in these systems, experimental investigation has revealed that in many cases their structure is not a single solid solution phase, and that the rules may not accurately distinguish the stability of the phase boundaries. Here, a combined modelling and experimental approach that looks into the electronic structure is proposed to improve accuracy of the predictions of the majority phase. To do this, the Rigid Band model is generalised for magnetic systems in prediction of the majority phase most likely to be found. Good agreement is found when the predictions are confronted with data from experiments, including a new magnetic HEA system (CoFeNiV). This also includes predicting the structural transition with varying levels of constituent elements, as a function of the valence electron concentration, n, obtained from the integrated spin-polarised density of states. This method is suitable as a new predictive technique to identify compositions for further screening, in particular for magnetic HEAs.

Application of Advanced Fracture Mechanics Technology to Ensure Structural Reliability in Critical Titanium Structures,

DTIC Science & Technology

1982-11-22

RD-Ri42 354 APPLICATION OF ADVANCED FRACTURE MECHANICS TECHNOLOGY i/i TT ENSURE STRUCTURA..(U) 1WESTINGHOUSE RESEARCH FND DEVELOPMENT CENTER...I Iml .4. 47 Igo 12. 4 %B 1. __ ~. ~% ski Z L __ 12 APPLICATION OF ADVANCED FRACTURE MECHANICS -p TECHNOLOGY TO ENSURE STRUCTURAL RELIABILITY IN...Road W Pilttsburgh. Pennsylvania 15235 84 06 18 207 APPLICATION OF ADVANCED FRACTURE MECHANICS TECHNOLOGY TO ENSURE STRUCTURAL RELIABILITY IN CRITICAL

Microstructural and mechanical characterization of laser deposited advanced materials

NASA Astrophysics Data System (ADS)

Sistla, Harihar Rakshit

Additive manufacturing in the form of laser deposition is a unique way to manufacture near net shape metallic components from advanced materials. Rapid solidification facilitates the extension of solid solubility, compositional flexibility and decrease in micro-segregation in the melt among other advantages. The current work investigates the employment of laser deposition to fabricate the following: 1. Functionally gradient materials: This allows grading dissimilar materials compositionally to tailor specific properties of both these materials into a single component. Specific compositions of the candidate materials (SS 316, Inconel 625 and Ti64) were blended and deposited to study the brittle intermetallics reported in these systems. 2. High entropy alloys: These are multi- component alloys with equiatomic compositions of 5 or more elements. The ratio of Al to Ni was decreased to observe the transition of solid solution from a BCC to an FCC crystal structure in the AlFeCoCrNi system. 3. Structurally amorphous alloys: Zr-based metallic glasses have been reported to have high glass forming ability. These alloys have been laser deposited so as to rapidly cool them from the melt into an amorphous state. Microstructural analysis and X-ray diffraction were used to study the phase formation, and hardness was measured to estimate the mechanical properties.

Biomimetic superhydrophobic surface of high adhesion fabricated with micronano binary structure on aluminum alloy.

PubMed

Liu, Yan; Liu, Jindan; Li, Shuyi; Liu, Jiaan; Han, Zhiwu; Ren, Luquan

2013-09-25

Triggered by the microstructure characteristics of the surfaces of typical plant leaves such as the petals of red roses, a biomimetic superhydrophobic surface with high adhesion is successfully fabricated on aluminum alloy. The essential procedure is that samples were processed by a laser, then immersed and etched in nitric acid and copper nitrate, and finally modified by DTS (CH3(CH2)11Si(OCH3)3). The obtained surfaces exhibit a binary structure consisting of microscale crater-like pits and nanoscale reticula. The superhydrophobicity can be simultaneously affected by the micronano binary structure and chemical composition of the surface. The contact angle of the superhydrophobic surface reaches up to 158.8 ± 2°. Especially, the surface with micronano binary structure is revealed to be an excellent adhesive property with petal-effect. Moreover, the superhydrophobic surfaces show excellent stability in aqueous solution with a large pH range and after being exposed long-term in air. In this way, the multifunctional biomimetic structural surface of the aluminum alloy is fabricated. Furthermore, the preparation technology in this article provides a new route for other metal materials.

Effect of Homogenizing Heat Treatment of Liquid Aluminum-Copper Alloys on the Structure of Rapidly Crystallized Specimens

NASA Astrophysics Data System (ADS)

Astaf'ev, V. V.; Kurochkin, A. R.; Yablonskikh, T. I.; Brodova, I. G.; Popel', P. S.

2017-11-01

Centrifugal casting into a massive slot chill mold was used to prepare two series of specimens of alloys of the Al - Cu system, containing from 10 to 32.2 at.% Cu. The first series was fabricated without a homogenizing heat treatment of the melt, while the second series was fabricated with heating of the melt to 1400°C. Both kinds of specimens were cast at the same temperature in order to provide for the same cooling rate of about 104 K/sec. The structures, phase compositions and microhardnesses of the structural components are compared. It is established that the homogenizing heat treatment changes the kinetics of crystallization and, hence, the proportion of phases in the alloy structure and the copper content in them.

Advanced structures technology and aircraft safety

NASA Technical Reports Server (NTRS)

Mccomb, H. G., Jr.

1983-01-01

NASA research and development on advanced aeronautical structures technology related to flight safety is reviewed. The effort is categorized as research in the technology base and projects sponsored by the Aircraft Energy Efficiency (ACEE) Project Office. Base technology research includes mechanics of composite structures, crash dynamics, and landing dynamics. The ACEE projects involve development and fabrication of selected composite structural components for existing commercial transport aircraft. Technology emanating from this research is intended to result in airframe structures with improved efficiency and safety.

Report on the completion of the procurement of the first heat of Alloy 709

DOE Office of Scientific and Technical Information (OSTI.GOV)

Natesan, K.; Zhang, X.; Sham, T. -L.

2017-01-01

This report provides details on the completion of the procurement of the first commercial-sized heat of Alloy 709. The report is a Level 3 deliverable in FY17 (M3AT- 17OR1602053), under the Work Package AT-17OR160205, “Advanced Alloy Development” performed by Oak Ridge National Laboratory, as part of Advanced Structural Materials Program for the Advanced Reactor Technologies (ART). This work project supports the fabrication scale up effort for Alloy 709 that was started in FY16. The effort culminated in the placement of a Purchase Order in August 2016 with a commercial vendor to melt an Alloy 709 heat using industrial melt practice.more » Four ingots, totaling about 45,000 lb, had been bottom-poured from the melt in September 2016. Two of the ingots were hot rolled into 1.2”x60”x155” and 1.1”x60”x100” plates using standard hot rolling process in FY17. Some small test pieces were cut from the asrolled plates and sent to Argonne National Laboratory (ANL) for archival. The plates were then heat treated and surface pickled by the vendor. The plates were subsequently delivered to ANL and Oak Ridge National Laboratory (ORNL). Properties and microstructure screening were performed on these plates upon delivery in February 2017 at ANL. Several samples were cut from the as-rolled and heattreated plates and were analyzed for their microstructures, hardness values, grain sizes, and room temperature tensile properties. The results indicate that the scaled-up heat of Alloy 709 fabricated using commercial practice exhibit tensile properties that exceed the minimum values specified in the ASME Code Case for commercial heat of NF709. These plates will be used to support base metal testing for the 650°C, 100,000-h Alloy 709 Code Case development, for fabrication of weldments, and for the NEUP projects.« less

Linear complexions: Confined chemical and structural states at dislocations.

PubMed

Kuzmina, M; Herbig, M; Ponge, D; Sandlöbes, S; Raabe, D

2015-09-04

For 5000 years, metals have been mankind's most essential materials owing to their ductility and strength. Linear defects called dislocations carry atomic shear steps, enabling their formability. We report chemical and structural states confined at dislocations. In a body-centered cubic Fe-9 atomic percent Mn alloy, we found Mn segregation at dislocation cores during heating, followed by formation of face-centered cubic regions but no further growth. The regions are in equilibrium with the matrix and remain confined to the dislocation cores with coherent interfaces. The phenomenon resembles interface-stabilized structural states called complexions. A cubic meter of strained alloy contains up to a light year of dislocation length, suggesting that linear complexions could provide opportunities to nanostructure alloys via segregation and confined structural states. Copyright © 2015, American Association for the Advancement of Science.

Magnesium Alloys for Space Hardware Design

NASA Technical Reports Server (NTRS)

Aroh, Joseph

2017-01-01

There have been advances in magnesium alloy development that NASA has not taken into consideration for space hardware because of a lack of test data. Magnesium alloys offer excellent weight reduction, specific strength, and deep space radiation mitigation. Traditionally, magnesium has been perceived as having too poor of a flammability resistance and corrosion resistance to be used for flight. Recent developments in magnesium alloying has led to the formation of two alloys, WE43 and Elektron 21, which are self-extinguishing and significantly less flammable because of their composition. Likewise, an anodizing process called Tagnite was formulated to deter any concern with galvanic and saltwater corrosion. The Materials Science Branch at Kennedy Space Center is currently researching these new alloys and treatments to better understand how they behave in the harsh environment of space. Successful completion of the proposed testing should result in a more thorough understanding of modern aerospace materials and processes, and possibly the permission to use magnesium alloys in future NASA designs.

The structural, electronic and dynamic properties of the L1{sub 2}- type Co{sub 3}Ti alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arikan, Nihat; Özduran, Mustafa

2014-10-06

The structural, electronic and dynamic properties of the cubic Co{sub 3}Ti alloy in L1{sub 2} structure have been investigated using a pseudopotential plane wave (PP-PW) method within the generalized gradient approximation proposed by Perdew–Burke–Ernzerhof (GGA-PBE). The structural properties, including the lattice constant, the bulk modulus and its pressure derivative agree reasonably with the previous results. The density of state (DOS), projected density of state (PDOS) and electronic band structure are also reported. The DOS shows that Co{sub 3}Ti alloy has a metallic character since the energy bands cross the Fermi level. The density of states at Fermi level mainly comesmore » from the Co-3d states. Phonon dispersion curves and their corresponding total densities of states were obtained using a linear response in the framework of the density functional perturbation theory. All computed phonon frequencies are no imaginer and thus, Co{sub 3}Ti alloy is dynamically stable. The zone center phonon modes have been founded to be 9.307, 9.626 and 13.891 THz for Co{sub 3}Ti.« less

First principles examination of electronic structure and optical features of 4H-GaN1-xPx polytype alloys

NASA Astrophysics Data System (ADS)

Laref, A.; Hussain, Z.; Laref, S.; Yang, J. T.; Xiong, Y. C.; Luo, S. J.

2018-04-01

By using first-principles calculations, we compute the electronic band structures and typical aspects of the optical spectra of hexagonally structured GaN1-xPx alloys. Although a type III-V semiconductor, GaP commonly possesses a zinc-blende structure with an indirect band gap; as such, it may additionally form hexagonal polytypes under specific growth conditions. The electronic structures and optical properties are calculated by combining a non-nitride III-V semiconductor and a nitride III-V semiconductor, as GaP and GaN crystallizing in a 4H polytype, with the N composition ranging between x = 0-1. For all studied materials, the energy gap is found to be direct. The optical properties of the hexagonal materials may illustrate the strong polarization dependence owing to the crystalline anisotropy. This investigation for GaN1-xPx alloys is anticipated to supply paramount information for applications in the visible/ultraviolet spectral regions. At a specific concentration, x, these alloys would be exclusively appealing candidates for solar-cell applications.

Chemical, electronic, and magnetic structure of LaFeCoSi alloy: Surface and bulk properties

NASA Astrophysics Data System (ADS)

Lollobrigida, V.; Basso, V.; Borgatti, F.; Torelli, P.; Kuepferling, M.; Coïsson, M.; Olivetti, E. S.; Celegato, F.; Tortora, L.; Stefani, G.; Panaccione, G.; Offi, F.

2014-05-01

We investigate the chemical, electronic, and magnetic structure of the magnetocaloric LaFeCoSi compound with bulk and surface sensitive techniques. We put in evidence that the surface retains a soft ferromagnetic behavior at temperatures higher than the Curie temperature of the bulk due to the presence of Fe clusters at the surface only. This peculiar magnetic surface effect is attributed to the exchange interaction between the ferromagnetic Fe clusters located at the surface and the bulk magnetocaloric alloy, and it is used here to monitor the magnetic properties of the alloy itself.

Differently Structured Advance Organizers Lead to Different Initial Schemata and Learning Outcomes

ERIC Educational Resources Information Center

Gurlitt, Johannes; Dummel, Sebastian; Schuster, Silvia; Nuckles, Matthias

2012-01-01

Does the specific structure of advance organizers influence learning outcomes? In the first experiment, 48 psychology students were randomly assigned to three differently structured advance organizers: a well-structured, a well-structured and key-concept emphasizing, and a less structured advance organizer. These were followed by a sorting task, a…

Development of Bulk Nanocrystalline Tungsten Alloys for Fusion Reactor Structures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fang, Zhigang Zak

This project developed a technology for manufacturing bulk ultrafine tungsten materials that are at or near full density for fusion reactor structural applications, aiming to improve ductility and toughness of tungsten before and after irradiation. The project involved the development of fabrication processes for making bulk ultrafine grained W, the development of new alloys of ultrafine grained W and evaluations of properties of these specific materials. The goal of this fabrication process is to produce fully dense bulk W with ultrafine grain sizes, with uniform distributions of grain size and additives. To date there is no known process that couldmore » be used to make ultrafine grained tungsten in a fully dense state and in a cost-acceptable fashion. The specific technology described in this proposal for making ultrafine grained tungsten involves a suite of nano-particle processing and sintering techniques. The program also developed new alloys of ultrafine grained W, e.g. W-(Ta,V,Ti)-TiC alloys to improve ductility and toughness before and after irradiation. By completing this project, we achieved the following objectives: • Demonstrated experimentally the feasibility of producing bulk ultrafine grained tungsten alloys (at or near 100% dense, <1000 nm grain size) using the proposed process • Demonstrated the proposed ultrafine grained W alloys, namely, W-(Ta, V, Ti)-TiC, can indeed be made using the proposed process • Demonstrated that the properties of nano tungsten alloys meet the requirements for fusion reactor applications. The overall goal was to harness the potential of ultrafine grained W produced using the proposed processes as the core structural materials for future fusion reactors. The project was very successful overall, meeting all milestones and surpassing project goals in terms of process development and material’s blistering resistance properties. A novel process similar to the conventional press-and-sinter powder metallurgy method

Fe-Al-Mn-C lightweight structural alloys: a review on the microstructures and mechanical properties.

PubMed

Kim, Hansoo; Suh, Dong-Woo; Kim, Nack J

2013-02-01

Adding a large amount of light elements such as aluminum to steels is not a new concept recalling that several Fe-Al-Mn-C alloys were patented in 1950s for replacement of nickel or chromium in corrosion resistance steels. However, the so-called lightweight steels or low-density steels were revisited recently, which is driven by demands from the industry where steel has served as a major structural material. Strengthening without loss of ductility has been a triumph in steel research, but lowering the density of steel by mixing with light elements will be another prospect that may support the competitiveness against emerging alternatives such as magnesium alloys. In this paper, we review recent studies on lightweight steels, emphasizing the concept of alloy design for microstructures and mechanical properties. The influence of alloying elements on the phase constituents, mechanical properties and the change of density is critically reviewed. Deformation mechanisms of various lightweight steels are discussed as well. This paper provides a reason why the success of lightweight steels is strongly dependent on scientific achievements even though alloy development is closely related to industrial applications. Finally, we summarize some of the main directions for future investigations necessary for vitalizing this field of interest.

Fe–Al–Mn–C lightweight structural alloys: a review on the microstructures and mechanical properties

PubMed Central

Kim, Hansoo; Suh, Dong-Woo; Kim, Nack J

2013-01-01

Adding a large amount of light elements such as aluminum to steels is not a new concept recalling that several Fe–Al–Mn–C alloys were patented in 1950s for replacement of nickel or chromium in corrosion resistance steels. However, the so-called lightweight steels or low-density steels were revisited recently, which is driven by demands from the industry where steel has served as a major structural material. Strengthening without loss of ductility has been a triumph in steel research, but lowering the density of steel by mixing with light elements will be another prospect that may support the competitiveness against emerging alternatives such as magnesium alloys. In this paper, we review recent studies on lightweight steels, emphasizing the concept of alloy design for microstructures and mechanical properties. The influence of alloying elements on the phase constituents, mechanical properties and the change of density is critically reviewed. Deformation mechanisms of various lightweight steels are discussed as well. This paper provides a reason why the success of lightweight steels is strongly dependent on scientific achievements even though alloy development is closely related to industrial applications. Finally, we summarize some of the main directions for future investigations necessary for vitalizing this field of interest. PMID:27877553

Study on solidification of immisible alloys (M-10)

NASA Technical Reports Server (NTRS)