摘要
High/medium entropy alloys(H/MEAs)are generally possible to exhibit chemical short-range order(SRO).However,the complex role of SRO on mechanical properties from nano-scale to meso-scale is still challenging so far.Here,we study the strengthening mechanism and deformation behavior in a model body-centered-cubic HfNbTa MEA by using atomic-scale molecular dynamics,micro-scale dislocation dynamics,and meso-scale crystal plasticity finite element.The SRO inhibits dislocation nucleation at the atomic scale,improving the flow stress.The SRO-induced ultrastrong local stress fluctuation greatly improves the micro-scale dislocation-based strength by the significant dislocation forest strengthening.Moreover,the Ta-rich locally ordered structure leads to an obvious heterogeneous strain and stress partitioning,which forms a strong strain gradient in the adjacent grain interiors and contributes to the strong back-stress-induced strain hardening.
中熵合金中广泛存在的化学短程有序对材料强韧性的影响研究是一个典型的跨尺度问题,构建从纳米尺度结构细节到细观尺度力学性能的跨尺度关联方法是阐明化学短程有序强韧化机理的关键.我们发展了一套结合纳米尺度分子动力学、微米尺度离散位错动力学和介观尺度晶体塑性有限元的分层多尺度模型框架.基于该方法,我们以体心立方HfNbTa体系为例,系统研究了化学短程有序对典型难熔中熵合金变形和强化行为的影响机理.纳米尺度上,化学短程有序结构抑制了位错形核,从而提高了合金的流动应力;细观尺度上,化学短程有序引起的超强局部应力波动诱发了额外的林位错强化,显著提高了位错强化的贡献.此外,通过诱导富Ta局部有序结构的形成,合金中的原子级非均匀应变和应力能够进一步增强,从而在相邻晶粒内部形成强应变梯度,提升背应力诱导的应变硬化.
基金
supported by the National Natural Science Foundation of China(Grant Nos.12372069,12302083,and 12172123)
China Postdoctoral Science Foundation(Grant Nos.2023M731061 and BX20230109)
the Natural Science Foundation of Hunan Province(Grant No.2022JJ20001)
Hunan Provincial Innovation Foundation for Postgraduate(Grant No.CX20220378)
Peter K.Liaw very much appreciates the support from the National Science Foundation(Grant Nos.DMR-1611180,1809640,and 2226508).
作者简介
Corresponding author:陈阳,E-mail address:yangchen0507@hnu.edu.cn;Corresponding author:李甲,E-mail address:lijial23@hnu.edu.cn。
