Grain boundary segregation and relaxation in nano-grained polycrystalline alloys  

作　　者：Tong-Yi Zhang Ying-Xin Gao Sheng Sun 

机构地区：[1]Materials Genome Institute,Shanghai University,Shanghai,200444,China

出　　处：《Science China(Physics,Mechanics & Astronomy)》2021年第2期72-90,共19页中国科学：物理学、力学、天文学（英文版）

基　　金：supported by the National Key R&D Program of China(Grant No.2017YFB0701604);the National Natural Science Foundation of China(Grant No.11672168)for financial support。

摘　　要：The present study carries out systematic thermodynamics analysis of Grain Boundary(GB)segregation and relaxation in NanoGrained(NG)polycrystalline alloys.GB segregation and relaxation is an internal process towards thermodynamic equilibrium,which occurs naturally in NG alloys without any applied loads,causes deformation and generates internal stresses.The analysis comprehensively investigates the multiple coupling effects among chemical concentrations and mechanical stresses in GBs and grains.A hybrid approach of eigenstress and eigenstrain is developed herein to solve the multiple coupling problem.The analysis results indicate that the GB stress and grain stress induced by GB segregation and relaxation can be extremely high in NG alloys,reaching the GPa level,which play an important role in the thermal stability of NG alloys,especially via the coupling terms between stress and concentration.The present theoretic analysis proposes a novel criterion of thermal stability for NG alloys,which is determined by the difference in molar free energy between a NG alloy and its reference single crystal with the same nominal chemical composition.If the difference at a temperature is negative or zero,the NG alloy is thermal stable at that temperature,otherwise unstable.

关 键 词：nano-grained alloys thermal stability grain boundary segregation eigenstress EIGENSTRAIN 

分 类 号：TB383.1[一般工业技术—材料科学与工程] TG113[金属学及工艺—物理冶金]