Dynamic tensile deformation and microstructural evolution of AlxCrMnFeCoNi high-entropy alloys
Dynamic tensile deformation and microstructural evolution of AlxCrMnFeCoNi high-entropy alloys
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DOI：
10.1016/j.msea.2019.05.095
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发表时间：
2019-06
期刊：
影响因子：
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通讯作者：
C. Cao;W. Tong;S. H. Bukhari;J. Xu;Y. Hao;P. Gu;H. Hao;Peng Lijun
中科院分区：
文献类型：
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作者：
C. Cao;W. Tong;S. H. Bukhari;J. Xu;Y. Hao;P. Gu;H. Hao;Peng Lijun
研究了AlxCrMnFeCoNi（x = 0，0.4和0.6）高熵合金的显微组织和应变速率对拉伸行为的影响。Al含量较低的合金经形变热处理后为fcc固溶体，而Al 0.6CrMnFeCoNi合金经形变热处理后为fcc + bcc固溶体。由于固溶强化、晶界强化和沉淀硬化的综合作用，Al0.6CrMnFeCoNi合金在准静态条件下具有较高的抗拉强度。在动态加载条件下，两种含铝合金的屈服强度和加工硬化都随应变速率的增加而显著增加。而Al0.4CrMnFeCoNi合金的应变速率敏感性比Al0.6CrMnFeCoNi合金大，这是由于合金中存在大量的bcc相和相间边界。Johnson-Cook本构模型可以用来描述应变率和应变对动态流动应力的影响。与准静态相比，动态变形条件下合金的微观组织以高密度位错和位错间的相互作用为主要特征，导致流变应力增大。较高的体心立方相体积分数和应变速率导致了韧性断裂向准解理断裂的转变。
The influence of microstructure and strain rate on tensile behavior of AlxCrMnFeCoNi (x = 0, 0.4 and 0.6 in molar ratio) high-entropy alloys was investigated. The alloys with lower Al content exhibited microstructures of simple fcc solid solution whereas the Al0.6CrMnFeCoNi alloy consisted of fcc + bcc mixed solutions after thermomechanical processing. Al0.6CrMnFeCoNi showed higher tensile strength at quasi-static condition due to the combinative contributions from solution strengthening, grain-boundary strengthening and precipitation hardening. Under dynamic loading conditions, both the yield strength and work hardening increased remarkably with increasing strain rate for the two Al-containing alloys. However, the Al0.4CrMnFeCoNi alloy showed a larger strain-rate sensitivity than Al0.6CrMnFeCoNi alloy owing to the existence of abundant bcc phase and interphase boundaries. Johnson-Cook constitutive model can be utilized to describe the effects of strain rate and strain on the dynamic flow stress. Compared to quasi-static condition, the higher density dislocations and interaction were the main characteristics of microstructures for dynamic deformation, leading to the increased flow stress. High volume fraction of bcc phase and strain rate led to a transition from ductile to quasi-cleavage fracture.