Phase field modeling of the aspect ratio dependent functional properties of NiTi shape memory alloys with different grain sizes  

不同晶粒尺寸的NiTi形状记忆合金长细比相关功能性能的相场模拟

作　　者：Bo Xu Beihai Huang Chong Wang Qingyuan Wang 徐波;黄北海;王宠;王清远

机构地区：[1]Failure Mechanics and Engineering Disaster Prevention,Key Laboratory of Sichuan Province,Sichuan University,Chengdu 610065,China [2]Department of Mechanical Science and Engineering,College of Architecture and Environment,Sichuan University,Chengdu 610065,China [3]Key Laboratory of Deep Underground Science and Engineering(Sichuan University),Ministry of Education,Chengdu 610065,China

出　　处：《Acta Mechanica Sinica》2025年第1期22-41,共20页力学学报(英文版)

基　　金：supported by the National Natural Science Foundation of China (Grant Nos.12202294 and 12022208);the Project funded by China Postdoctoral Science Foundation (Grant No.2022M712243);the Fundamental Research Funds for the Central Universities (Grant No.2023SCU12098).

摘　　要：It is well known that coarse-grained super-elastic NiTi shape memory alloys(SMAs)exhibit localized rather than homogeneous martensite transformation(MT),which,however,can be strongly influenced by either internal size(grain size,GS)or the external size(geometric size).The coupled effect of GS and geometric size on the functional properties has not been clearly understood yet.In this work,the super-elasticity,one-way,and stress-assisted two-way shape memory effects of the polycrystalline NiTi SMAs with different aspect ratios(length/width for the gauge section)and different GSs are investigated based on the phase field method.The coupled effect of the aspect ratio and GS on the functional properties is adequately revealed.The simulated results indicate that when the aspect ratio is lower than about 4:1,the stress biaxiality and stress heterogeneity in the gauge section of the sample become more and more obvious with decreasing the aspect ratio,which can significantly influence the microstructure evolution in the process involving external stress.Therefore,the corresponding functional property is strongly dependent on the aspect ratio.With decreasing the GS and the aspect ratio(to be lower than 4:1),both the aspect ratio and GS can affect the MT or martensite reorientation in each grain and the interaction among grains.Thus,due to the strong internal constraint(i.e.,the constraint of grain boundary)and the external constraint(i.e.,the constraint of geometric boundary),the capabilities of the functional properties of NiTi SMAs are gradually weakened and highly dependent on these two factors.众所周知,粗晶的超弹性NiTi形状记忆合金(SMA)会表现出局域而非均匀的马氏体相变,其会受到内部尺寸(晶粒尺寸)或外部尺寸(几何尺寸)的强烈影响.晶粒尺寸和几何尺寸对功能性能的耦合作用尚未得到明确的认识.本文采用相场法研究了不同长细比(工作段的长/宽)和不同晶粒尺寸的多晶NiTi SMAs的超弹性、单程和应力辅助双程形状记忆效应.本工作充分揭示了长细比和晶粒尺寸对功能性能的耦合作用.模拟结果表明,当长细比低于约4:1时,随着长细比的减小,试样工作段的应力双轴性和应力非均质性越来越明显,这对外加应力过程中的微结构演化有显著影响.因此,相应的功能性能强烈依赖于长细比.随着晶粒尺寸和长细比(小于4:1)的减小,长细比和晶粒尺寸都会影响晶粒内部的马氏体相变或重取向以及晶粒间的交互作用.因此,由于较强的内部约束(即晶界约束)和外部约束(即几何边界约束),NiTi SMA功能性能的能力逐渐减弱,并强烈依赖于这两个因素.

关 键 词：Phase field modeling NITI Aspect ratio Grain size Functional property 

分 类 号：TG139.6[一般工业技术—材料科学与工程]