scholarly journals Nano-Scaled Creep Response of TiAlV Low Density Medium Entropy Alloy at Elevated Temperatures

Materials ◽  
2019 ◽  
Vol 13 (1) ◽  
pp. 36
Author(s):  
Xiangkai Zhang ◽  
Hanting Ye ◽  
Jacob C. Huang ◽  
Taiyou Liu ◽  
Pinhung Lin ◽  
...  
Keyword(s):  
Elevated Temperatures ◽  
Peierls Stress ◽  
Dislocation Creep ◽  
Calphad Approach ◽  
Low Density ◽  
Face Centered Cubic ◽  
Specific Strength ◽  
Phase Constituent ◽  
Fcc Alloys ◽  
Face Centered

A low density, medium entropy alloy (LD-MEA) Ti33Al33V34 (4.44 g/cm3) was successfully developed. The microstructure was found to be composed of a disordered body-centered-cubic (BCC) matrix and minor ordered B2 precipitates based on transmission electron microscopy characterization. Equilibrium and non-equilibrium modeling, simulated using the Calphad approach, were applied to predict the phase constituent. Creep behavior of {110} grains at elevated temperatures was investigated by nanoindentation and the results were compared with Cantor alloy and Ti-6Al-4V alloy. Dislocation creep was found to be the dominant mechanism. The decreasing trend of hardness in {110} grains of BCC TiAlV is different from that in {111} grains of face-centered-cubic (FCC) Cantor alloy due to the different temperature-dependence of Peierls stress in these two lattice structures. The activation energy value of {110} grains was lower than that of {111} grains in FCC Cantor alloy because of the denser atomic stacking in FCC alloys. Compared with conventional Ti-6Al-4V alloy, TiAlV possesses considerably higher hardness and specific strength (63% higher), 83% lower creep displacement at room temperature, and 50% lower creep strain rate over the temperature range from 500 to 600 °C under the similar 1150 MPa stress, indicating a promising substitution for Ti-6Al-4V alloy as structural materials.

Voids in Irradiated Tungsten and Molybdenum

1969 ◽  
Vol 27 ◽  
pp. 190-191
Author(s):  
Robert C. Rau ◽  
Robert L. Ladd
Keyword(s):  
Melting Point ◽  
Fast Neutron ◽  
Neutron Irradiation ◽  
Elevated Temperatures ◽  
Irradiation Temperature ◽  
The Body ◽  
Face Centered Cubic ◽  
Body Centered Cubic ◽  
Cubic Metals ◽  
Face Centered

Recent studies have shown the presence of voids in several face-centered cubic metals after neutron irradiation at elevated temperatures. These voids were found when the irradiation temperature was above 0.3 Tm where Tm is the absolute melting point, and were ascribed to the agglomeration of lattice vacancies resulting from fast neutron generated displacement cascades. The present paper reports the existence of similar voids in the body-centered cubic metals tungsten and molybdenum.

Low-Density, High-Temperature Co Base Superalloys

2021 ◽  
Vol 51 (1) ◽  
Author(s):  
Surendra Kumar Makineni ◽  
Mahander Pratap Singh ◽  
Kamanio Chattopadhyay
Keyword(s):  
High Temperature ◽  
Elevated Temperatures ◽  
Ternary Alloys ◽  
Specific Yield ◽  
Annual Review ◽  
Publication Date ◽  
High Temperature Strength ◽  
Low Density ◽  
Face Centered Cubic ◽  
Alloy Development

Co base superalloys strengthened by coherent L12 ordered γ′ precipitate in a disordered face-centered cubic γ matrix represent a new opportunity for high-temperature alloy development. The emergence of alloys with low density and high specific yield strength at elevated temperatures has further energized the research and development efforts in the last 5 years. Initially stabilized by the addition of small amounts of Nb and Ta, these new generations of alloys with multiple alloying additions to form basic quaternary and ternary alloys have steadily expanded the property envelopes to raise hope for a modern class of superalloys with higher-temperature capabilities. This article reviews the work of a vibrant set of researchers across the globe whose findings are constantly unlocking the potential of these alloys. These developments have achieved high-temperature strength (at 870°C) >0.6 GPa, γ′ solvus temperature exceeding 1,100°C, and densities between 7.8 and 8.6 g/cm3. Expected final online publication date for the Annual Review of Materials Science, Volume 51 is August 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Optical Constants Retrieval from a Thin Film at Elevated Temperatures Using Emittance

2021 ◽  
Author(s):  
Jui-Yung Chang ◽  
Yi-Hua Yang ◽  
Vikas Yadav ◽  
Yu-Bin Chen
Keyword(s):  
Thin Film ◽  
Refractive Index ◽  
Thermal Radiation ◽  
Optical Constants ◽  
Elevated Temperatures ◽  
Emission Angle ◽  
Face Centered Cubic ◽  
Hexagonal Close Packed ◽  
Phase Temperature ◽  
Face Centered

Abstract Refractive index and extinction coefficient (optical constants) are essential in photonic design and thermal radiation utilization. These constants vary with the material phase, temperature, wavelength, and subject dimension. Precisely retrieving these constants of a thin film is thus challenging at elevated temperatures. To tackle this challenge, a methodology for retrieval using emittance at different emission angle θ has been developed here. The method contains four steps and takes advantages of an emissometry. The method is firstly validated using simulation and then demonstrates its feasibility by retrieving optical constants of a phase change germanium-antimony-tellurium (Ge2Sb2Te5, GST) film. Emittance from samples at 100°C, 200°C, 300°C, and 400°C is measured at θ = 0°, 15°, and 30°. The spectral range of retrieval covers from 4 μm to 18 μm where thermal radiation dominates. The investigated film phase considers amorphous, face-centered cubic (FCC), and hexagonal close packed (HCP). The retrieved constants exhibit temperature and substrate independence, but they show up significant phase reliance.

scholarly journals Invariant plastic deformation mechanism in paramagnetic nickel–iron alloys

2021 ◽  
Vol 118 (14) ◽  
pp. e2023181118
Author(s):  
Zhihua Dong ◽  
Wei Li ◽  
Stephan Schönecker ◽  
Bin Jiang ◽  
Levente Vitos
Keyword(s):  
Plastic Deformation ◽  
High Temperature ◽  
Deformation Mechanism ◽  
Elevated Temperatures ◽  
Face Centered Cubic ◽  
Nickel Iron ◽  
Plastic Deformation Mechanism ◽  
The Face ◽  
Face Centered ◽  
Scientific Attention

The Invar anomaly is one of the most fascinating phenomena observed in magnetically ordered materials. Invariant thermal expansion and elastic properties have attracted substantial scientific attention and led to important technological solutions. By studying planar faults in the high-temperature magnetically disordered state of Ni1−cFec, here we disclose a completely different anomaly. An invariant plastic deformation mechanism is characterized by an unchanged stacking fault energy with temperature within wide concentration and temperature ranges. This anomaly emerges from the competing stability between the face-centered cubic and hexagonal close-packed structures and occurs in other paramagnetic or nonmagnetic systems whenever the structural balance exists. The present findings create a platform for tailoring high-temperature properties of technologically relevant materials toward plastic stability at elevated temperatures.

scholarly journals Quasi-periodic variation of Peierls stress of dislocations in face-centered-cubic metals

2017 ◽  
Vol 90 ◽  
pp. 156-166 ◽  
Author(s):  
Guisen Liu ◽  
Xi Cheng ◽  
Jian Wang ◽  
Kaiguo Chen ◽  
Yao Shen
Keyword(s):  
Periodic Variation ◽  
Peierls Stress ◽  
Face Centered Cubic ◽  
Cubic Metals ◽  
Face Centered

scholarly journals A dual-phase alloy with ultrahigh strength-ductility synergy over a wide temperature range

2021 ◽  
Vol 7 (34) ◽  
pp. eabi4404
Author(s):  
Raymond Kwesi Nutor ◽  
Qingping Cao ◽  
Ran Wei ◽  
Qingmei Su ◽  
Gaohui Du ◽  
...  
Keyword(s):  
Wide Temperature Range ◽  
Elevated Temperatures ◽  
Interesting Property ◽  
Specific Yield ◽  
Dynamic Strain ◽  
Face Centered Cubic ◽  
High Entropy ◽  
Temperature Range ◽  
Face Centered ◽  
Multiple Deformation

High-entropy alloys (HEAs), as an emerging class of materials, have pointed a pathway in developing alloys with interesting property combinations. Although they are not exempted from the strength-ductility trade-off, they present a standing chance in overcoming this challenge. Here, we report results for a precipitation-strengthening strategy, by tuning composition to design a CoNiV-based face-centered cubic/B2 duplex HEA. This alloy sustains ultrahigh gigapascal-level tensile yield strengths and excellent ductility from cryogenic to elevated temperatures. The highest specific yield strength (~150.2 MPa·cm3/g) among reported ductile HEAs is obtained. The ability of the alloy presented here to sustain this excellent strength-ductility synergy over a wide temperature range is aided by multiple deformation mechanisms i.e., twins, stacking faults, dynamic strain aging, and dynamic recrystallization. Our results open the avenue for designing precipitation-strengthened lightweight HEAs with advanced strength-ductility combinations over a wide service temperature range.

Improved measurement of void swelling

1990 ◽  
Vol 48 (4) ◽  
pp. 844-845
Author(s):  
D. S. Gelles ◽  
R. M. Claudson ◽  
L. E. Thomas
Keyword(s):  
Electron Micrographs ◽  
Austenitic Stainless Steels ◽  
Sample Volume ◽  
Void Volume ◽  
Spherical Approximation ◽  
Face Centered Cubic ◽  
Simple Measurement ◽  
Fcc Alloys ◽  
Void Volumes ◽  
Face Centered

Irradiation of crystalline materials by neutrons or other energetic particles often causes swelling by formation of internal cavities, or voids. The swelling, or total void volume within a given sample volume, can be determined from transmission electron micrographs by simple measurement of the void images. However, errors of over 100% in the calculated void volumes are possible if the voids are approximated as spheres. The problem arises because the voids are usually polyhedral, crystallographically oriented features and no single size parameter has been defined for the spherical approximation. In austenitic stainless steels and other face-centered-cubic (fCC) alloys, voids range from octahedra with {111} faces to cubes with {100} faces and exhibit all intermediate (truncated) forms. Void truncation may also vary widely within a given field of view. Voids in ferritic steels and other body-centered-cubic (bcc) materials may range from octahedra with {111} faces to cubes with {100} faces to dodecahedra with {110} faces. The relationship between void shape on electron micrographs and void volume was therefore studied with the aim of improving the accuracy of swelling determination without requiring a separate shape determination for each void. Void volumes were determined as a function of a shape parameter and related to the various ‘size’ parameters available in different crystal orientations. Procedures were then defined to minimize the error in swelling measurement.

Studies of Sputter Deposited CU1-XTAX Alloys

1993 ◽  
Vol 308 ◽  
Author(s):  
Hong Wang ◽  
M. J. Zaluzec ◽  
Y. Liu ◽  
J. Mazumder ◽  
J. M. Rigsbee
Keyword(s):  
Refractory Metal ◽  
Elevated Temperatures ◽  
High Strength ◽  
Face Centered Cubic ◽  
Structure Property ◽  
Metal Composites ◽  
Face Centered ◽  
Sputter Deposited ◽  
Mutual Solubilities ◽  
Rf Sputter Deposition

ABSTRACTCopper-refractory metal composites/alloys are of interest for aerospace and related applications requiring good thermal conductivity and high strength at elevated temperatures[1]. These materials, due to generally very low mutual solubilities, may allow high strength microstructures to be developed which are stable at temperatures exceeding those suitable for precipitation strengthened alloys. Phase stability and mechanical property characteristics of bulk fabricated Cu-refractory metal composites were recently reviewed[2-3]. This paper reports the results of structure-property studies of a series of Cu1–xTax alloys created by RF sputter deposition. It will be shown that nanoscale face-centered-cubic and body-centered-cubic Ta particles form in the Cu matrix and that these Ta particles are very resistant to coarsening at temperatures up to 900ºC. Nanoindentation studies of these alloys reveal that their strengths are also essentially unaffected by exposure to 900ºC for times up to 100 hours.

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