摘要
运用拓扑模型研究了等原子比NiTi合金B2-B19'马氏体相变晶体学,根据最优扭转角(wo)准则计算得到wo=-0.969°,并获得了马氏体惯习面指数及母相-马氏体相界面位错结构特征,计算结果与实验测量值非常接近。NiTi合金马氏体相变所产生的相变应变包含一个平行于惯习面的剪切应变和一个垂直于惯习面的轴向应变,轴向应变量表示B2-B19'相变所引起的宏观体积变化为εHP33=6.6879×10-3,表明NiTi合金的负热膨胀现象来源于合金中马氏体相变所产生的相变应变。
Some NiTi alloys, generally known as shape memory alloys or smart materials, exhibit larger negative thermal expansion （NTE） strain than that of traditional nonmetallic NTE materials. Furthermore, high strength and better ductility of NiTi alloy make it more advantageous compared to nonmetallic materials. The NTE response of NiTi alloy may be attributed to the transformation strain that originates from the volume change accompanying the B2-B19＇ martensitic transformation in the alloy. Therefore, it is of great importance and interests to study the martensitic transformation crystallography in NiTi alloy. In this work, the martensitic transformation crystallography in an equiatomic NiTi alloy was investigated by using the topological model, as well as the optimum twist criterion developed lately. The optimum twist angle, ωo, in NiTi alloy was determined to be -0.969°, and the so-obtained transformation crystallography results, including the habit plane index and parent-martensite orientation relationship, agree well with the corresponding experimental data and theoretical calculations in the literature. Furthermore, the martensitic transformation strain of NiTi alloy was calculated based on the analysis of interfacial dislocation movement, and the total transformation strain can be resolved into an in-habit-plane shear strain and an axial strain perpendicular to the habit plane. In particular, the value of the axial strain that represents the volume change due to the B19＇ to B2 transformation was found to be negative, indicating that the NiTi alloy shrinks during the reverse martensitic phase transformation when heated, which might shed some light on the relationship between the NTE mechanism and martensitic transformation in NiTi alloy. The measured NTE strain is much smaller than the theoretical calculated phase transformation strain in NiTi alloy, due to the self-accommodation effect of martensite variants and the compensation of transformation strains in polycrystalline materials.
作者
韦昭召
马骁
张新平
Zhaozhao WEI;Xiao MA;Xinping ZHANG(School of Mechanical and Electrical Engineering,Wuyi University,Jiangmen 529020,China;School of Materials Science and Engineering,South China University of Technology,Guangzhou 510640,China)
出处
《金属学报》
SCIE
EI
CAS
CSCD
北大核心
2018年第10期1461-1470,共10页
Acta Metallurgica Sinica
基金
国家自然科学基金项目No.51571092
广东省自然科学基金项目No.2017A030310657
广东省"创新强校工程"青年创新人才类项目No.2016KQNCX170
五邑大学博士启动基金项目No.2015BS16~~
关键词
拓扑模型
NITI合金
马氏体相变晶体学
相变应变
负热膨胀
topological model
NiTi alloy
martensitic transformation crystallography
transformationstrain
negative thermal expansion
