摘要
运用马氏体相变拓扑模型研究了Ni_2MnGa合金中相界面位错结构及马氏体相变晶体学,并将计算结果与马氏体相变唯象理论进行了对比.当选择相变位错b_(+1/+1)^(D1)和晶格不变应变位错b^L=0.186[111]_M作为吸收共格应变的界面缺陷,且扭转角ω=3.2°时,惯习面HP^((2))的晶面指数为{0.691-0.117 0.713}_P,与台阶台面的倾角为42.000°;两相的位向关系为:(111)_P偏离(101)_M 0.317°,[110]_P偏离[111]_M约3.200°.上述计算结果与基于马氏体相变唯象理论的估算值非常接近,表明Burgers矢量长度较小的界面缺陷在相变过程中更容易被激活,由此计算所获得的理论结果也更符合马氏体相变唯象理论基于不变平面的假设.另外,还用马氏体相变拓扑模型计算并获得了马氏体相变唯象理论所无法获得的相界面缺陷网结构参数,说明这种模型比唯象理论更普适、更优越.
Ferromagnetic shape memory alloys （FSMAs）, such as Ni2MnGa alloy, promise to be the key materials in manufacturing new type of actuator and sensor because of their high responsive speed and large strain output. In order to find the best functions of FSMAs, the understanding of their martensite transformation crystallography is of enormous necessity and importance. In the present study, the topological model of martensite transformation was applied to the analysis of the interphase interfacial defect structure and crystallography of martensite transformation, such as the habit plane index and orientation relationship, in a Ni2MnGa alloy. The results obtained in this work were compared with the prediction from the phenomenological theory of martensite crystallography （PTMC）. When the transformation dislocation DI b＋1/＋1 with smaller Burgers vectors and the lattice invariant deformation （LID） dislocation bL---0.186[III]M are activated to accommodate the coherency strain with a twist angle w=3.2°, the habit plane is determined to be {0.691 -0.117 0.713}p represented in the parent crystal frame, having an inclination angle p--42.000with the terrace plane （lll）p. Furthermore, the orientation relationship between the parent and martensite phases is found to be, namely, {0.69 -0.117 0.713}p 0.317°away from （101）M and [li0]p about 3.200away from [111]M, which are close to the calculated values based on the phenomenologi- cal theory of martensite crystallography. It is evident that the transformation dislocation with smaller Burgers vectors can be activated more easily during a martensite transformation. Additionally, for a range of twist w, the alternative combination of disconnection and LID might be introduced in the topological model to obtain multiple predictions of martensite transformation crystallography, which could provide an explanation for the diversity and complexity of martensite transformation crystallography resulting from the different measured positions or external fields. Moreover, the parameters of the interfacial defect network, i.e., the line direction and the spacing of the interracial defects, were also determined according to the topological model of martensite transformation, while the PTMC provides limited information of the microstructure of the martensite interface. It has been shown that the topological model of martensite transformation exhibits greater flexibility and advantage compared to the PTMC.
出处
《金属学报》
SCIE
EI
CAS
CSCD
北大核心
2013年第2期187-198,共12页
Acta Metallurgica Sinica
基金
国家自然科学基金项目50801029和50871039
广东省自然科学基金项目10151064101000017
中央高校基本科研业务费专项资金项目2012ZZ0014资助~~
关键词
马氏体相变
拓扑模型
相变晶体学
相界面结构
相变位错
martensite transformation, topological model, transformation crystallography,interphase interface structure, transformation dislocation
