Triple-scale Dislocation-crystal Plasticity Modeling for Evaluation on Mechanical Properties of Ultrafine-Grained Metal

本研究利用新提出的位错耗尽情况下的临界分解剪应力模型，建立了连接三个层次尺度的多尺度晶体塑性模型，成功地计算再现了超细晶金属中出现的强度随晶粒尺寸减小而增加、塑性随晶粒尺寸减小而降低、屈服应力下降和Luders带扩展的特殊力学行为，即：通过均质化方法得到位错结构、晶粒聚集体和宏观结构。此外，还讨论了粗晶分散在超细晶基体中的双峰组织塑性提高的机理。

In this study, it has been succeeded that peculiar mechanical behaviors occurring in f. c. c. ultrafine-grained metals, i. e., increase of strength and decrease of ductility with decrease of grain size, yield stress drop and propagation of Luders band are computationally reproduced by using a critical resolved shear stress model proposed newly for situation of dislocation exhaustion and by developing a multiscale crystal plasticity model bridging three hierarchical scales, i. e., dislocation structure, grain aggregates and macroscopic structure through the homogenization method. Moreover, a mechanism of ductility improvement of bimodal structures with coarse grains dispersed in ultrafine-grained matrix is also discussed.