Revealing the effect of inverse dislocation pileups on the mechanical properties of multi-principal element alloys  

作　　者：Fei Shuang Jian Xue Katerina E.Aifantis 

机构地区：[1]Department of Mechanical and Aerospace Engineering,University of Florida,Gainesville,FL,32611,USA [2]State Key Laboratory of Nonlinear Mechanics(LNM),Institute of Mechanics,Chinese Academy of Sciences,Beijing 100190,China

出　　处：《Journal of Materials Science & Technology》2024年第23期155-171,共17页材料科学技术（英文版）

摘　　要：In this work, we utilize atomistic simulations and dislocation mechanics to explore the formation of in-verse pileups in CrCoNi model alloys and elucidate their unique impact on the strength and ductilityof multi-principal element alloys (MPEAs). The present atomistic simulations on single crystals revealthat during the deformation of CrCoNi, stress gradients lead to the formation of novel inverse disloca-tion pileup. We find that this unique dislocation pattern in a confined volume is due to the elevatedlattice friction and significant stress gradient present in the material. Furthermore, this phenomenon canbe notably promoted by lowering the temperature, increasing the loading rate, and introducing chemicalshort-range ordering. Additional simulations on bicrystals show that these inverse pileups play a criticalrole in suppressing dislocation transmission, reflection, and grain boundary (GB) migration. As a result,they effectively mitigate stress concentration and reduce damage accumulation at GBs, lowering the riskof catastrophic failure due to GB damages. In our theoretical analysis, we utilize dislocation mechanics topredict the formation of the inverse pileup and its subsequent strengthening effect, considering scenarioswith and without obstacles. Our investigations encompass various lattice frictions and stress gradients.Remarkably, our results shed light on the prevailing impact of dislocation hardening in the plastic de-formation of CrCoNi even under the presence of a linear stress gradient, while the contribution of GBstrengthening is found to be comparatively limited. These findings provide valuable insights into the de-formation mechanisms of MPEAs in general and significantly aid their applications as promising structuralmaterials.

关 键 词：Multi-principal element alloys CrCoNi Inverse dislocation pileup Strength Ductility Stress gradient 

分 类 号：TG146.23[一般工业技术—材料科学与工程]