摘要
Nanoscale segregation of alien solute atoms at the grain boundary(GB)can enhance the stability and mechanical properties of the GB.Systematic molecular dynamic simulations were conducted to clarify the strengthening effect of Cu segregation on AlΣ9(221)[110]GB.The as-predicted negative segregation energy suggests the strong inclination of Cu segregation at Al GBs.Such segregation is expected to improve GB stability and strength.Detailed structural analysis during the uniaxial tensile test indicates that Cu segregation can reduce the free volume of GB atoms and restrict GB atomic displacement,thereby retarding dislocation nucleation and increasing the tensile strength of the GB.The suppressed atomic migrations by Cu doping also give rise to the exceptional stability of E structures at GB,which can retain their kite shape against structural transition during straining.With Cu segregation,the pattern of dislocation nucleation from GB was shifted from“shuffling-assisted regime”to the“collective-migration regime”,wherein the latter necessitates higher critical stress.Further,Cu-doping was also shown to elevate the GB shear strength via blocking the shear-coupled GB migration when subjected to shear deformation.The enhanced GB resistance against shear straining is attributed to the stabilized E structures with Cu segregation featuring reduced atomic free volume.This study provides atomic-scale insights into the stabilizing and strengthening effect of Cu segregation on Al GBs.
溶质原子在晶界处的纳米尺度偏析可显著改善晶界稳定性与力学性能.本文采用分子动力学模拟研究了铜偏聚对铝Σ9(221)[110]晶界的强化机制.计算得到的负偏聚能证实铜原子在铝晶界具有强烈偏析倾向.单轴拉伸下的结构演化分析显示:铜原子偏聚通过减少晶界原子自由体积,限制原子位移,有效抑制了位错形核,从而提高晶界拉伸强度.另外,铜偏聚对原子迁移的抑制增强了晶界E结构的稳定性,使其在形变过程中维持风筝状构型,避免了结构转变.铜偏析使晶界位错形核模式由“原子重组机制”转变为需更高应力的“集体迁移机制”.剪切变形下,铜偏聚通过阻碍剪切耦合晶界迁移,显著提升晶界剪切强度.这种增强效应源于铜偏聚对E结构的稳定化作用及原子自由体积的降低.本研究为铜偏析强化铝晶界的原子尺度机制提供了新见解.
基金
supported by the National Key Research and Development Program of China(2024YFA1209800)
the National Natural Science Foundation of China(52422103,52271010,52001224)。
