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采用透射电镜观察了Ni-Mn-Ga形状记忆合金非调制马氏体变体对A-B的晶体学特点。结果表明,马氏体变体为微米级的板条,该板条由两种粗、细不同的纳米级的片层组成,粗、细片层呈{1 1 2}复合型孪晶关系。两变体之间任意一对片层的取向关系随着细片层所占体积分数(λ)的改变而改变。λ较大时,变体之间片层对(粗-粗、粗-细、细-细片层对)都不是(1 12)孪晶,λ接近于零时,细片层消失,粗-粗片层对为(1 12)孪晶。随着λ由较大值减小至零,A-B界面由波浪状的弯曲界面转变成平直的共格孪晶界。
The crystallographic characteristics of Ni-Mn-Ga shape memory alloy unmodulated martensite on A-B were observed by transmission electron microscopy. The results show that the martensite variant is a micrometer-scale lath. The lath is composed of two coarse and fine nanoscale laminae. The coarsening and fine lamellae show a complex twins relationship of {1 1 2}. The orientation relationship of any pair of layers between two variants changes with the change of the volume fraction (λ) of the fine layers. When λ is large, the lamella pairs (crude-coarse, coarse-fine, fine-fine lamellar pairs) are not (1 12) twins. When λ is close to zero, Rough layer pairs (12) twins. As λ decreases from a larger value to zero, the A-B interface transforms from a wavy curved interface into a flat coherent twin boundary.