CoCrNi中熵合金极薄带流动应力的尺寸效应

Size Effect of Flow Stress in CoCrNi Medium Entropy Alloy Ultrathin Strips

摘要:

构建了一个考虑尺寸效应的本构模型，以分析CoCrNi中熵合金极薄带在单轴准静态拉伸试验中不同变形阶段的行为。结果表明，由于尺寸效应，传统宏观成形技术在微成形过程中的适用性受限，这一点与极薄带成形过程中厚度与直径比（t/d）的关系密切相关。在t/d低于10.62的情况下，CoCrNi合金带材在弹性变形阶段展现出明显的尺寸依赖性。随着t/d的降低，表面层晶粒的体积分数上升，导致流动应力呈线性下降趋势。在塑性变形阶段，材料的刚度与t/d呈现相关性。具体来说，随着t/d的提升，材料的加工硬化能力增强，当t/d接近10时达到峰值，超过该值后加工硬化能力开始减弱。

Abstract:

A constitutive model considering the size effect was established to investigate the behavior of CoCrNi medium entropy alloy ultrathin strip in different deformation stages during the uniaxial quasi-static tensile test. Results show that when the t/d value is lower than 10.62, the CoCrNi alloy ultrathin strip shows an obvious size-dependent property in the elastic deformation stage. With the decrease in t/d value, the volume fraction of the surface layer grains is increased, leading to the linear decrease in flow stress. In the plastic deformation stage, the material stiffness is correlated with the t/d value. Specifically, as the t/d value increases, the work-hardening capacity of the material is enhanced. When the t/d value increases to 10, the work-hardening capacity reaches a maximum state; when the t/d value is beyond 10, the work-hardening capacity weakens.