Phase transition and heterogeneous strengthening mechanism in CoCrFeNiMn high-entropy alloy fabricated by laser-engineered net shaping via annealing at intermediate-temperature

The CrCuFeMnNi high entropy alloy (HEA) powder was synthesized by mechanical alloying. The effects of milling time and subsequent annealing on the structure evolution, thermostability and magnetic property were investigated. After 50[Formula: see text]h of milling, the CrCuFeMnNi HEA powder consisted of a major FCC phase and a small amount of BCC phase. The crystallite size and strain lattice of 50[Formula: see text]h-ball-milled CrCuFeMnNi HEA powder were 12[Formula: see text]nm and 1.02%, respectively. The powder exhibited refined morphology and excellent chemical homogeneity. The supersaturated solid solution structure of the as-milled HEA powder transformed into FCC1, FCC2, a small amount of BCC and [Formula: see text] phase in annealed state. Most of the BCC phase decomposed into FCC (mainly FCC2 phase) and [Formula: see text] phases, and the dynamic phase transition was almost in equilibrium at 900[Formula: see text]C. The saturated magnetization and coercivity force of the 50[Formula: see text]h-ball-milled CrCuFeMnNi HEA powder were respectively 16.1[Formula: see text]emu/g and 56.2[Formula: see text]Oe.

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Microstructure evolution, mechanical properties and strengthening mechanism of refractory high-entropy alloy matrix composites with addition of TaC

Journal of Alloys and Compounds ◽

10.1016/j.jallcom.2018.11.111 ◽

2019 ◽

Vol 777 ◽

pp. 1168-1175 ◽

Cited By ~ 7

Author(s):

Qinqin Wei ◽

Qiang Shen ◽

Jian Zhang ◽

Yin Zhang ◽

Guoqiang Luo ◽

...

Keyword(s):

Mechanical Properties ◽

Microstructure Evolution ◽

Strengthening Mechanism ◽

High Entropy Alloy ◽

Matrix Composites ◽

Alloy Matrix ◽

High Entropy

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Plastic deformation and strengthening mechanism of FCC/HCP nano-laminated dual-phase CoCrFeMnNi high entropy alloy

Nanotechnology ◽

10.1088/1361-6528/ac2980 ◽

2021 ◽

Author(s):

Cheng Huang ◽

Yin Yao ◽

Xianghe Peng ◽

Shaohua Chen

Keyword(s):

Plastic Deformation ◽

Strengthening Mechanism ◽

High Entropy Alloy ◽

Dual Phase ◽

High Entropy

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Influence of alumina whisker or nano-carbon contents on the microstructure and mechanical properties of CuZrTiAlNi refractory high entropy alloy composites

Materials Testing ◽

10.1515/mt-2020-620705 ◽

2020 ◽

Vol 62 (7) ◽

pp. 678-688

Author(s):

X. Jiang ◽

J. Chen ◽

H. Sun ◽

Z. Shao

Keyword(s):

Mechanical Properties ◽

Load Transfer ◽

Microwave Sintering ◽

Fracture Morphology ◽

Strengthening Mechanism ◽

Cold Isostatic Pressing ◽

High Entropy Alloy ◽

High Entropy ◽

Structure And Property ◽

Fine Grain

Abstract High-entropy alloy composites were fabricated by ball milling, cold isostatic pressing and microwave sintering to which were added varied contents of Al2O3 whiskers, La-Ce, and carbon nanotubes-graphene, respectively. The structure and mechanical properties of the composites were investigated by X-ray diffraction, scanning electron microscopy and a microhardness tester. The high-entropy alloy and composites show amorphous phases and some crystalline phases. Accordingly, the addition of the reinforcement phase can refine the grain size. The formation mechanism of the phase is mainly related to the factors of mixing entropy, enthalpy, differences in atomic size, and the structure and property of the elements. The hardness of the composites is higher than that of the alloy (437.5 HV), and those composites reinforced by 0.5 wt.-% nanotubes- 0.5 wt.-% graphene are the highest (593.99 HV). The fracture morphology of the Al2O3 whisker reinforced composite shows a river pattern, indicating brittle cleavage. According to the research results, it can be concluded that the strengthening mechanism of the high entropy alloy composites mainly reflects fine grain strengthening and load transfer, and the toughening mechanism mainly crack bridging and a pulling out of the reinforcing phase.

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Intermediate-Temperature Creep Deformation and Microstructural Evolution of an Equiatomic FCC-Structured CoCrFeNiMn High-Entropy Alloy

Entropy ◽

10.3390/e20120960 ◽

2018 ◽

Vol 20 (12) ◽

pp. 960 ◽

Cited By ~ 10

Author(s):

Chengming Cao ◽

Jianxin Fu ◽

Tongwei Tong ◽

Yuxiao Hao ◽

Ping Gu ◽

...

Keyword(s):

Activation Energy ◽

Dynamic Recrystallization ◽

Creep Deformation ◽

High Stress ◽

Intermediate Temperature ◽

Tensile Creep ◽

High Entropy Alloy ◽

High Entropy ◽

Stress Region ◽

Stress Dependent

The tensile creep behavior of an equiatomic CoCrFeNiMn high-entropy alloy was systematically investigated over an intermediate temperature range (500–600 °C) and applied stress (140–400 MPa). The alloy exhibited a stress-dependent transition from a low-stress region (LSR-region I) to a high-stress region (HSR-region II). The LSR was characterized by a stress exponent of 5 to 6 and an average activation energy of 268 kJ mol−1, whereas the HSR showed much higher corresponding values of 8.9–14 and 380 kJ mol−1. Microstructural examinations on the deformed samples revealed remarkable dynamic recrystallization at higher stress levels. Dislocation jogging and tangling configurations were frequently observed in LSR and HSR at 550 and 600 °C, respectively. Moreover, dynamic precipitates identified as M23C6 or a Cr-rich σ phase were formed along grain boundaries in HSR. The diffusion-compensated strain rate versus modulus-compensated stress data analysis implied that the creep deformation in both stress regions was dominated by stress-assisted dislocation climb controlled by lattice diffusion. Nevertheless, the abnormally high stress exponents in HSR were ascribed to the coordinative contributions of dynamic recrystallization and dynamic precipitation. Simultaneously, the barriers imposed by these precipitates and severe initial deformation were referred to so as to increase the activation energy for creep deformation.

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