scholarly journals Deformation-induced crystalline-to-amorphous phase transformation in a CrMnFeCoNi high-entropy alloy

2021 ◽  
Vol 7 (14) ◽  
pp. eabe3105
Author(s):  
Hao Wang ◽  
Dengke Chen ◽  
Xianghai An ◽  
Yin Zhang ◽  
Shijie Sun ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Amorphous Phase ◽  
Structural Evolution ◽  
Crack Tip ◽  
Dislocation Slip ◽  
High Entropy Alloy ◽  
Face Centered Cubic ◽  
High Entropy ◽  
Dislocation Glide ◽  
Ultrafine Grained

The Cantor high-entropy alloy (HEA) of CrMnFeCoNi is a solid solution with a face-centered cubic structure. While plastic deformation in this alloy is usually dominated by dislocation slip and deformation twinning, our in situ straining transmission electron microscopy (TEM) experiments reveal a crystalline-to-amorphous phase transformation in an ultrafine-grained Cantor alloy. We find that the crack-tip structural evolution involves a sequence of formation of the crystalline, lamellar, spotted, and amorphous patterns, which represent different proportions and organizations of the crystalline and amorphous phases. Such solid-state amorphization stems from both the high lattice friction and high grain boundary resistance to dislocation glide in ultrafine-grained microstructures. The resulting increase of crack-tip dislocation densities promotes the buildup of high stresses for triggering the crystalline-to-amorphous transformation. We also observe the formation of amorphous nanobridges in the crack wake. These amorphization processes dissipate strain energies, thereby providing effective toughening mechanisms for HEAs.

scholarly journals Effects of Nb Addition on Microstructures and Mechanical Properties of Nbx-CoCrFeMnNi High Entropy Alloy Films

Coatings ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1539
Author(s):  
Yu-Hsuan Liang ◽  
Chia-Lin Li ◽  
Chun-Hway Hsueh
Keyword(s):  
Mechanical Properties ◽  
Amorphous Phase ◽  
Compressive Yield Strength ◽  
High Entropy Alloy ◽  
Face Centered Cubic ◽  
Compression Tests ◽  
Alloy Films ◽  
High Entropy ◽  
Microstructures And Mechanical Properties ◽  
Nb Addition

In the present work, Nbx-CoCrFeMnNi high entropy alloy films (HEAFs, 0 to 7.2 at.% Nb) were fabricated by radio frequency (RF) magnetron co-sputtering of CoCrFeMnNi alloy and Nb targets. The effects of Nb addition on the microstructures and mechanical properties of HEAFs were systematically investigated. For Nb-free film (0 at.% Nb), the face-centered cubic (FCC) peaks were identified in the X-ray diffraction (XRD) pattern. The addition of Nb resulted in a broadening of diffraction peaks, a decrease in peak intensity, and the vanishment of high-angle peaks. Transmission electron microscope (TEM) images indicated the formation of nanotwins at low Nb concentrations, and a transition from a single phase FCC solid solution to an amorphous phase was observed with the increasing Nb concentration. The films were strengthened with an increase in Nb concentration. Specifically, the hardness characterized by nanoindentation increased from 6.5 to 8.1 GPa. The compressive yield strength and fracture strength measured from micropillar compression tests were improved from 1.08 GPs and 2.56 GPa to 2.70 GPa and 5.76 GPa, respectively, whereas the fracture strain decreased from >29.4% (no fracture) to 15.8%. Additionally, shear banding was observed in the presence of amorphous phase.

Effect of Ta Addition on Structural Evolution and Mechanical Properties of the CoFeNi2W0.5 High Entropy Alloy

2016 ◽  
Vol 849 ◽  
pp. 34-39 ◽  
Author(s):  
Li Jiang ◽  
Yong Dong ◽  
Hui Jiang ◽  
Yi Ping Lu ◽  
Zhi Qiang Cao ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Vickers Hardness ◽  
Solution Structure ◽  
Structural Evolution ◽  
Alloy System ◽  
High Entropy Alloy ◽  
Face Centered Cubic ◽  
High Entropy ◽  
Microstructure And Mechanical Properties ◽  
Electron Microscopes

A series of CoFeNi2W0.5Tax (x = 0-0.6) high entropy alloys (HEAs) were synthesized by arc melting to investigate the alloying effect of Ta element on the microstructure and mechanical properties of the CoFeNi2W0.5 alloy system. Phase constitution, microstructure and mechanical properties of the alloys were analyzed by X-ray diffraction (XRD), scanning electron microscopes (SEM), Vickers hardness and compressive test. It was found that when x = 0, the alloy consists of a single-phase face-centered cubic (FCC) solid solution structure and exhibit excellent ductility, the compressive plastic elongation of which can reach 80% without fracture. While with increasing Ta content, the brittle Co2Ta-type Laves phase appears which leads to a decrease of the plastic strain and an increase of the yield strength, and the Vickers hardness shows an obvious increase from HV 179.5 to HV 753.2.

scholarly journals Microstructure, Texture, and Strength Development during High-Pressure Torsion of CrMnFeCoNi High-Entropy Alloy

Crystals ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 336 ◽  
Author(s):  
Werner Skrotzki ◽  
Aurimas Pukenas ◽  
Eva Odor ◽  
Bertalan Joni ◽  
Tamas Ungar ◽  
...  
Keyword(s):  
High Pressure ◽  
Phase Transformation ◽  
Room Temperature ◽  
High Pressure Torsion ◽  
Strength Development ◽  
High Entropy Alloy ◽  
Face Centered Cubic ◽  
X Ray ◽  
High Entropy ◽  
Face Centered

The equiatomic face-centered cubic high-entropy alloy CrMnFeCoNi was severely deformed at room and liquid nitrogen temperature by high-pressure torsion up to shear strains of about 170. Its microstructure was analyzed by X-ray line profile analysis and transmission electron microscopy and its texture by X-ray microdiffraction. Microhardness measurements, after severe plastic deformation, were done at room temperature. It is shown that at a shear strain of about 20, a steady state grain size of 24 nm, and a dislocation density of the order of 1016 m−2 is reached. The dislocations are mainly screw-type with low dipole character. Mechanical twinning at room temperature is replaced by a martensitic phase transformation at 77 K. The texture developed at room temperature is typical for sheared face-centered cubic nanocrystalline metals, but it is extremely weak and becomes almost random after high-pressure torsion at 77 K. The strength of the nanocrystalline material produced by high-pressure torsion at 77 K is lower than that produced at room temperature. The results are discussed in terms of different mechanisms of deformation, including dislocation generation and propagation, twinning, grain boundary sliding, and phase transformation.

Phase transformation assisted twinning in a face-centered-cubic FeCrNiCoAl high entropy alloy

2019 ◽  
Vol 181 ◽  
pp. 491-500 ◽  
Author(s):  
Peijun Yu ◽  
Rui Feng ◽  
Junping Du ◽  
Shuhei Shinzato ◽  
Jyh-Pin Chou ◽  
...  
Keyword(s):  
Phase Transformation ◽  
High Entropy Alloy ◽  
Face Centered Cubic ◽  
High Entropy ◽  
Face Centered

scholarly journals Nanoporous Quasi-High-Entropy Alloy Microspheres

Metals ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 345 ◽  
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.

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

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.

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

Metals ◽  
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.

Effects of Al addition on structural evolution and tensile properties of the FeCoNiCrMn high-entropy alloy system

2014 ◽  
Vol 62 ◽  
pp. 105-113 ◽  
Author(s):  
J.Y. He ◽  
W.H. Liu ◽  
H. Wang ◽  
Y. Wu ◽  
X.J. Liu ◽  
...  
Keyword(s):  
Tensile Properties ◽  
Structural Evolution ◽  
Alloy System ◽  
High Entropy Alloy ◽  
High Entropy ◽  
Al Addition
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