Intermediate-Temperature Creep Deformation and Microstructural Evolution of an Equiatomic FCC-Structured CoCrFeNiMn High-Entropy Alloy.
Intermediate-Temperature Creep Deformation and Microstructural Evolution of an Equiatomic FCC-Structured CoCrFeNiMn High-Entropy Alloy.
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DOI：
10.3390/e20120960
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发表时间：
2018-12-12
期刊：
影响因子：
--
通讯作者：
Peng L
中科院分区：
文献类型：
--
作者：
Cao C;Fu J;Tong T;Hao Y;Gu P;Hao H;Peng L
系统研究了等原子数CoCrFeNiMn高熵合金在中温（500-600 °C）和外加应力（140-400 MPa）下的拉伸蠕变行为。合金表现出从低应力区（LSR-区I）到高应力区（HSR-区II）的应力依赖性转变。LSR的应力指数为5 ~ 6，平均活化能为268 kJ mol−1，而HSR的应力指数为8.9 ~ 14，平均活化能为380 kJ mol−1。变形后的试样的显微组织检查发现显着的动态再结晶在较高的应力水平。分别在550和600 °C下，LSR和HSR中经常观察到位错慢跑和缠结构型。此外，在HSR中沿沿着形成了被鉴定为M23 C6或富Cr σ相的动态析出物。扩散补偿应变率与模量补偿应力数据分析表明，在两个应力区的蠕变变形是由晶格扩散控制的应力辅助位错攀移。然而，HSR中异常高的应力指数归因于动态再结晶和动态析出的协同贡献。同时，这些析出物和严重的初始变形所施加的障碍，以提高蠕变变形的激活能。
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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发表时间：
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期刊：
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影响因子：
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