Amorphization in extreme deformation of the CrMnFeCoNi high-entropy alloy

Ever-harsher service conditions in the future will call for materials with increasing ability to undergo deformation without sustaining damage while retaining high strength. Prime candidates for these conditions are certain high-entropy alloys (HEAs), which have extraordinary work-hardening ability and toughness. By subjecting the equiatomic CrMnFeCoNi HEA to severe plastic deformation through swaging followed by either quasi-static compression or dynamic deformation in shear, we observe a dense structure comprising stacking faults, twins, transformation from the face-centered cubic to the hexagonal close-packed structure, and, of particular note, amorphization. The coordinated propagation of stacking faults and twins along {111} planes generates high-deformation regions, which can reorganize into hexagonal packets; when the defect density in these regions reaches a critical level, they generate islands of amorphous material. These regions can have outstanding mechanical properties, which provide additional strengthening and/or toughening mechanisms to enhance the capability of these alloys to withstand extreme loading conditions.

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Ultrastrong Al0.1CoCrFeNi high-entropy alloys at small scales: effects of stacking faults vs. nanotwins

Nanoscale ◽

10.1039/c8nr03573c ◽

2018 ◽

Vol 10 (28) ◽

pp. 13329-13334 ◽

Cited By ~ 19

Author(s):

Xiaobin Feng ◽

Jinyu Zhang ◽

Kai Wu ◽

Xiaoqing Liang ◽

Gang Liu ◽

...

Keyword(s):

Stacking Faults ◽

Maximum Strength ◽

High Entropy Alloy ◽

High Entropy Alloys ◽

Face Centered Cubic ◽

High Entropy ◽

Small Scales ◽

Face Centered

The present stacking faulted and nanotwinned Al0.1CoCrFeNi high-entropy alloy pillars achieved the maximum strength among face-centered cubic structured metals.

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Formation and Anisotropic Mechanical Behavior of Stacking Fault Tetrahedron in Ni and CoCrFeNiMn High-Entropy Alloy

Frontiers in Materials ◽

10.3389/fmats.2021.813382 ◽

2022 ◽

Vol 8 ◽

Author(s):

Sen Hu ◽

Tao Fu ◽

Qihao Liang ◽

Shayuan Weng ◽

Xiang Chen ◽

...

Keyword(s):

Mechanical Behavior ◽

Critical Stress ◽

Three Dimensional ◽

Stacking Faults ◽

Stacking Fault ◽

High Entropy Alloy ◽

Face Centered Cubic ◽

High Entropy ◽

Stacking Fault Tetrahedron ◽

Dynamics Simulations

Stacking fault tetrahedron (SFT) is a kind of detrimental three-dimensional defect in conventional face-centered cubic (FCC) structural metals; however, its formation and anisotropic mechanical behavior in a CoCrFeNiMn high-entropy alloy (HEA) remain unclear. In this work, we first performed molecular dynamics simulations to verify the applicability of the Silcox-Hirsch mechanism in the CoCrFeNiMn HEA. The mechanical responses of the SFT to shear stress in different directions and that of the pure Ni counterpart were simulated, and the evolutions of the atomic structures of the SFTs during shear were analyzed in detail. Our results revealed that the evolution of the SFT has different patterns, including the annihilation of stacking faults, the formation and expansion of new stacking faults, and insignificant changes in stacking faults. It was found that the effects of SFT on the elastic properties of Ni and HEA are negligible. However, the introduction of SFT would reduce the critical stress, while the critical stress of the CoCrFeNiMn HEA is much less sensitive to SFT than that of Ni.

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L21-strengthened face-centered cubic high-entropy alloy with high strength and ductility

Materials Science and Engineering A ◽

10.1016/j.msea.2020.140056 ◽

2020 ◽

Vol 797 ◽

pp. 140056 ◽

Cited By ~ 2

Author(s):

Yongliang Qi ◽

Yake Wu ◽

Tinghui Cao ◽

Lin He ◽

Feng Jiang ◽

...

Keyword(s):

High Strength ◽

High Entropy Alloy ◽

Face Centered Cubic ◽

High Entropy ◽

Face Centered ◽

Strength And Ductility

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Nanoporous Quasi-High-Entropy Alloy Microspheres

Metals ◽

10.3390/met9030345 ◽

2019 ◽

Vol 9 (3) ◽

pp. 345 ◽

Cited By ~ 3

Author(s):

Lianzan Yang ◽

Yongyan Li ◽

Zhifeng Wang ◽

Weimin Zhao ◽

Chunling Qin

Keyword(s):

Mechanical Properties ◽

Solid Solution ◽

Specific Surface ◽

Surface Area ◽

Specific Surface Area ◽

High Specific Surface Area ◽

High Entropy Alloy ◽

Face Centered Cubic ◽

High Entropy ◽

Hierarchical Porous

High-entropy alloys (HEAs) present excellent mechanical properties. However, the exploitation of chemical properties of HEAs is far less than that of mechanical properties, which is mainly limited by the low specific surface area of HEAs synthesized by traditional methods. Thus, it is vital to develop new routes to fabricate HEAs with novel three-dimensional structures and a high specific surface area. Herein, we develop a facile approach to fabricate nanoporous noble metal quasi-HEA microspheres by melt-spinning and dealloying. The as-obtained nanoporous Cu30Au23Pt22Pd25 quasi-HEA microspheres present a hierarchical porous structure with a high specific surface area of 69.5 m2/g and a multiphase approximatively componential solid solution characteristic with a broad single-group face-centered cubic XRD pattern, which is different from the traditional single-phase or two-phase solid solution HEAs. To differentiate, these are named quasi-HEAs. The synthetic strategy proposed in this paper opens the door for the synthesis of porous quasi-HEAs related materials, and is expected to promote further applications of quasi-HEAs in various chemical fields.

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Development of Novel Lightweight Al-Rich Quinary Medium-Entropy Alloys with High Strength and Ductility

Materials ◽

10.3390/ma14154223 ◽

2021 ◽

Vol 14 (15) ◽

pp. 4223

Author(s):

Po-Sung Chen ◽

Yu-Chin Liao ◽

Yen-Ting Lin ◽

Pei-Hua Tsai ◽

Jason S. C. Jang ◽

...

Keyword(s):

Mechanical Properties ◽

Compressive Strength ◽

Compressive Strain ◽

High Strength ◽

Fine Tuning ◽

Face Centered Cubic ◽

Transportation Industry ◽

High Entropy ◽

Good Potential ◽

Face Centered

Most high-entropy alloys and medium-entropy alloys (MEAs) possess outstanding mechanical properties. In this study, a series of lightweight nonequiatomic Al50–Ti–Cr–Mn–V MEAs with a dual phase were produced through arc melting and drop casting. These cast alloys were composed of body-centered cubic and face-centered cubic phases. The density of all investigated MEAs was less than 5 g/cm3 in order to meet energy and transportation industry requirements. The effect of each element on the microstructure evolution and mechanical properties of these MEAs was investigated. All the MEAs demonstrated outstanding compressive strength, with no fractures observed after a compressive strain of 20%. Following the fine-tuning of the alloy composition, the Al50Ti20Cr10Mn15V5 MEA exhibited the most compressive strength (~1800 MPa) and ductility (~34%). A significant improvement in the mechanical compressive properties was achieved (strength of ~2000 MPa, strain of ~40%) after annealing (at 1000 °C for 0.5 h) and oil-quenching. With its extremely high specific compressive strength (452 MPa·g/cm3) and ductility, the lightweight Al50Ti20Cr10Mn15V5 MEA demonstrates good potential for energy or transportation applications in the future.

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Vacuum brazing of Al2O3 and 3D printed Ti6Al4V lap-joints using high entropy driven AlZnCuFeSi filler

Scientific Reports ◽

10.1038/s41598-021-87705-x ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Ashutosh Sharma ◽

Byungmin Ahn

Keyword(s):

Strength Properties ◽

Lap Joints ◽

High Entropy Alloy ◽

Face Centered Cubic ◽

High Entropy ◽

Plasma Sintering ◽

Spark Plasma ◽

3D Printed ◽

Face Centered ◽

Alloy Filler

AbstractIn this work, we studied the brazing characteristics of Al2O3 and 3D printed Ti–6Al–4V alloys using a novel equiatomic AlZnCuFeSi high entropy alloy filler (HEAF). The HEAF was prepared by mechanical alloying of the constituent powder and spark plasma sintering (SPS) approach. The filler microstructure, wettability and melting point were investigated. The mechanical and joint strength properties were also evaluated. The results showed that the developed AlZnCuFeSi HEAF consists of a dual phase (Cu–Zn, face-centered cubic (FCC)) and Al–Fe–Si rich (base centered cubic, BCC) phases. The phase structure of the (Cu–Al + Ti–Fe–Si)/solid solution promises a robust joint between Al2O3 and Ti–6Al–4V. In addition, the joint interfacial reaction was found to be modulated by the brazing temperature and time because of the altered activity of Ti and Zn. The optimum shear strength reached 84 MPa when the joint was brazed at 1050 °C for 60 s. The results can be promising for the integration of completely different materials using the entropy driven fillers developed in this study.

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Microstructure Refinement by Low-Temperature Ausforming in an Fe-Based Metastable High-Entropy Alloy

Metals ◽

10.3390/met11050742 ◽

2021 ◽

Vol 11 (5) ◽

pp. 742

Author(s):

Motomichi Koyama ◽

Takeaki Gondo ◽

Kaneaki Tsuzaki

Keyword(s):

Low Temperature ◽

Plastic Anisotropy ◽

High Entropy Alloy ◽

Face Centered Cubic ◽

High Entropy ◽

Microstructure Refinement ◽

Hexagonal Close Packed ◽

Solution Treated Condition ◽

Solution Treated ◽

Face Centered

The effects of ausforming in an Fe30Mn10Cr10Co high-entropy alloy on the microstructure, hardness, and plastic anisotropy were investigated. The alloy showed a dual-phase microstructure consisting of face-centered cubic (FCC) austenite and hexagonal close-packed (HCP) martensite in the as-solution-treated condition, and the finish temperature for the reverse transformation was below 200 °C. Therefore, low-temperature ausforming at 200 °C was achieved, which resulted in microstructure refinement and significantly increased the hardness. Furthermore, plasticity anisotropy, a common problem in HCP structures, was suppressed by the ausforming treatment. This, in turn, reduced the scatter of the hardness.

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