一、前言 近年来,Ni-Ti系等合金中的形状记忆效应(Shape memory effect)及其机理愈来愈引起人们的注意。迄今已有的研究表明,NiTi合金的SME不仅与马氏体转变有关,而且也涉及到预马氏体转变,与所谓的“预马氏体现象”密切相关。然而,关于预马氏体相变的本质及其对SME的贡献至今尚未得到很好的理解,人们对问题的看法也还存在分歧。 I. INTRODUCTION In recent years, the shape memory effect and its mechanism in Ni-Ti alloy have drawn more and more attention. So far, studies have shown that the SME of NiTi alloys is not only related to the martensitic transformation, but also to the pre-martensitic transformation, which is closely related to the so-called “pre-martensite phenomenon.” However, the nature of the pre-martensitic transformation and its contribution to the SME have not yet been well understood and there are still divergent views on the issue.