Grain refinement of non-equiatomic Cr-rich CoCrFeMnNi high-entropy alloys through combination of cold rolling and precipitation of σ phase

2018 ◽  
Vol 735 ◽  
pp. 191-200 ◽  
Author(s):  
Ken Cho ◽  
Yumi Fujioka ◽  
Takeshi Nagase ◽  
Hiroyuki Y. Yasuda
Keyword(s):  
Cold Rolling ◽  
Grain Refinement ◽  
High Entropy Alloys ◽  
Σ Phase ◽  
High Entropy

scholarly journals Designing (Ultra)Fine-Grained High-Entropy Alloys by Spark Plasma Sintering and Equal-Channel Angular Pressing

Crystals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1157
Author(s):  
Lisa-Marie Rymer ◽  
Thomas Lindner ◽  
Philipp Frint ◽  
Martin Löbel ◽  
Thomas Lampke
Keyword(s):  
Tensile Strength ◽  
Grain Refinement ◽  
Spark Plasma Sintering ◽  
Equal Channel Angular Pressing ◽  
High Entropy Alloys ◽  
High Entropy ◽  
Fine Grained ◽  
Angular Pressing ◽  
Plasma Sintering ◽  
Spark Plasma

Single-phase, face-centered cubic (FCC) high-entropy alloys (HEA) are promising materials for future applications. In order to improve the mechanical properties, especially the tensile strength of these materials, this study focuses on the combination of spark plasma sintering (SPS) and equal-channel angular pressing (ECAP). The initial fine-grained microstructure produced by SPS is further refined by ECAP in a 90°-die. Optical microscopy and electron backscatter diffraction (EBSD) confirm this considerable grain refinement, leads to a grain size below 1 µm after 1 ECAP pass. An alternating arrangement of fine-grained areas and much coarser regions, aligned under an angle of approximately 27°, is found. Moreover, a first microstructural investigation of the twin structure is conducted. The mechanical behavior was investigated by hardness measurements and tensile testing. Both the hardness and tensile strength are remarkably increased after ECAP. In contrast, the uniform elongation and elongation at fracture are significantly reduced due to the strengthening mechanisms of strain hardening and grain refinement. It is concluded that the combination of SPS and ECAP is an attractive approach for designing (ultra)fine-grained HEAs with superior properties. The investigated techniques could be applied to understand the underlying microstructural mechanisms.

scholarly journals Effect of Molybdenum Additives on Corrosion Behavior of (CoCrFeNi)100−xMox High-Entropy Alloys

Entropy ◽  
2018 ◽  
Vol 20 (12) ◽  
pp. 908 ◽  
Author(s):  
Wenrui Wang ◽  
Jieqian Wang ◽  
Honggang Yi ◽  
Wu Qi ◽  
Qing Peng
Keyword(s):  
Corrosion Behavior ◽  
Compressive Strain ◽  
Compressive Yield Strength ◽  
High Entropy Alloys ◽  
Face Centered Cubic ◽  
Σ Phase ◽  
High Entropy ◽  
Passivation Film ◽  
Face Centered ◽  
Mo Content

The present work investigates the influence of micro-alloyed Mo on the corrosion behavior of (CoCrFeNi)100−xMox high-entropy alloys. All of the (CoCrFeNi)100−xMox alloys exhibit a single face-centered cubic (FCC) solid solution. However, the (CoCrFeNi)97Mo3 alloy exhibits an ordered sigma (σ) phase enriched in Cr and Mo. With the increase of x (the Mo content) from 1 to 3, the hardness of the (CoCrFeNi)100−xMox alloys increases from 124.8 to 133.6 Vickers hardness (HV), and the compressive yield strength increases from 113.6 MPa to 141.1 MPa, without fracture under about a 60% compressive strain. The potentiodynamic polarization curve in a 3.5% NaCl solution indicates that the addition of Mo has a beneficial effect on the corrosion resistance to some certain extent, opposed to the σ phase. Furthermore, the alloys tend to form a passivation film in the 0.5 M H2SO4 solution in order to inhibit the progress of the corrosion reaction as the Mo content increases.

scholarly journals Effect of Annealing on Microstructure and Mechanical Properties of Al0.5CoCrFeMoxNi High-Entropy Alloys

Entropy ◽  
2018 ◽  
Vol 20 (11) ◽  
pp. 812 ◽  
Author(s):  
Yan-Xin Zhuang ◽  
Xiu-Lan Zhang ◽  
Xian-Yu Gu
Keyword(s):  
Mechanical Properties ◽  
Annealing Temperature ◽  
High Entropy Alloys ◽  
Obvious Effect ◽  
Σ Phase ◽  
High Entropy ◽  
Phase Constituent ◽  
Microstructure And Mechanical Properties ◽  
Bcc Phase ◽  
Good Agreement

The effect of annealing temperature on the microstructure, phase constituents and mechanical properties of Al0.5CoCrFeMoxNi high-entropy complex alloys has been investigated at a fixed annealing time (10 h). The 600 °C-annealing has no obvious effect on their microstructures, while the annealing at 800–1200 °C enhances the precipitation of (Al,Ni)-rich ordered BCC phase or/and (Cr,Mo)-rich σ phase, and thereby greatly affects the microstructure and mechanical properties of the alloys. All the annealed Al0.5CoCrFeNi alloys are composed of FCC and (Al,Ni)-rich ordered BCC phases; the phase constituent of the Al0.5CoCrFeMo0.1Ni alloy changes from FCC + BCC (600 °C) to FCC + BCC + σ (800 °C) and then to FCC + BCC (1100 °C); the phase constituents of the Al0.5CoCrFeMo0.2Ni and Al0.5CoCrFeMo0.3Ni alloys change from FCC + BCC + σ to FCC + BCC with the annealing temperature rising from 600 to 1200 °C; while all the annealed Al0.5CoCrFeMo0.4Ni and Al0.5CoCrFeMo0.5Ni alloys consist of FCC, BCC and σ phases. The phase constituents of most of the alloys investigated are in good agreement with the calculated results from Thermo-Calc program. The alloys annealed at 800 °C under current investigation conditionshave relative fine precipitations and microstructure, and thereby higher hardness and yield stress.

Microstructures and properties of Fe1.25CoNi1.25CrxAl0.25 high-entropy alloys after cold-rolling and annealing

2021 ◽  
Vol 570 ◽  
pp. 121023
Author(s):  
Chunyan Li ◽  
Yu Lu ◽  
Xinling Li ◽  
Zhenxiang Zhao ◽  
Shengzhong Kou ◽  
...  
Keyword(s):  
Cold Rolling ◽  
High Entropy Alloys ◽  
High Entropy ◽  
Cold Rolling And Annealing

Effect of Chemical Composition on Grain Refinement of AlxCoCrFeNi High Entropy Alloys with NiAl Grain Boundary Precipitates

2021 ◽  
Vol 1016 ◽  
pp. 1690-1695
Author(s):  
Hiroyuki Y. Yasuda ◽  
Hiroyuki Miyamoto ◽  
Takuya Inagaki ◽  
Ken Cho ◽  
Takeshi Nagase
Keyword(s):  
Grain Refinement ◽  
Volume Fraction ◽  
High Entropy Alloys ◽  
High Entropy ◽  
Nial Phase ◽  
Ultrafine Grained ◽  
Average Grain Size ◽  
Ultrafine Grained Microstructure ◽  
B2 Structure ◽  
Smith Model

In AlxCoCrFeNi high entropy alloys (x = 0.3–0.5), the NiAl phase with the B2 structure is precipitated rapidly along the fcc grain boundaries. During recrystallization after conventional cold rolling, the NiAl precipitates effectively suppress the grain growth, which results in the ultrafine-grained microstructure. It should be noted that no severe plastic deformation is necessary to obtain the microstructure. The volume fraction of the NiAl precipitates increases with increasing x. As a result, the average grain size of the fcc matrix (dm) after the recrystallization decreases with increasing x, and therefore, a minimum dm of 0.5 μm can be obtained at x = 0.5. The grain refinement by the NiAl precipitates is consistent with the Zener-Smith model. At x = 0.5, the alloy with dm = 0.5 μm exhibits a yield stress of 1163 MPa and an elongation of 24% at room temperature.

Effect of Cold Rolling on the Microstructure and Hardness of Al5Cr12Fe35Mn28Ni20 High Entropy Alloy

2018 ◽  
Vol 917 ◽  
pp. 241-245 ◽  
Author(s):  
Sally Elkatatny ◽  
Mohamed Abdel Hady Gepreel ◽  
Atef Hamada
Keyword(s):  
Cold Rolling ◽  
Phase Structure ◽  
Rolling Reduction ◽  
High Entropy Alloy ◽  
High Entropy Alloys ◽  
Characterization Methods ◽  
High Entropy ◽  
Cold Rolling Reduction ◽  
Fcc Phase ◽  
Dendritic Structures

The microstructure and hardness changes of a non-equiatomic Al5Cr12Fe35Mn28Ni20high-entropy-alloys (HEA) with cold rolling are presented here. Using a variety of characterization methods, it is shown that the alloy is single FCC phase structure which doesn't change with cold rolling up to90%CR. With increasing the cold rolling reduction ratio, the hardness increased and the dendritic structures are broken and refined.

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