对Ni2MnGa铁磁形状记忆合金的缺口试样, 通过在微分干涉相衬显微镜下原位拉伸, 研究了裂纹形核、扩展和马氏体相变以及塑性变形的关系. 结果表明, 拉伸时首先形成马氏体, 当裂尖应力集中足够大时就会在裂尖产生局部塑性区, 微裂纹易于沿马氏体界面形核, 但也可在塑性区中形核. 随载荷升高, 微裂纹沿马氏体不连续形核, 通过韧带剪切连接, 从而导致裂纹扩展阻力也随裂纹扩展而增大.
The interrelationship of crack nucleation to martensite transformation and plastic deformation has been studied in situ using a differential interference constrast (DIC) microscopy for a notched sample of Ni2MnGa ferromagnetic shape memory alloy . The result showed that martensites form firstly during loading and there was a plastic zone when stress concentration ahead of a crack is large enough . Microcrack initiated preferentially along the interface of martensite , but also initiated in the plastic zone . With increasing the load , microcracks initiated discontinuously along the martensites and connected through shear microcracks in the ligaments , resulting in a resistance curve increase behavior .
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