NiMn基磁控形状记忆合金外应力作用于马氏体相变的晶体学研究

This project aims to reveal the martensitic transformation crystallography under the external stress for NiMnX (X = Ga、In、Sn) based magnetic shape memory alloys, where the external stress is applied during martensitic transformation for microstructure optimization. Through detailed analyses on the morphological and crystallographic features by use of EBSD technique, as well as in-situ neutron diffraction, the underlying mechanisms for martensitic transformation, strain accommodation and variant selection under the external stress are to be illustrated. Moreover, the crystallographic model depicting the martensitic transformation under the external stress is to be developed. Based on the above investigations, the correlation between the crystallographic features resulted from the martensitic formation under the external stress and the magnetic field induced strains is to be established, which is expected to provide some necessary guidance for the microstructure control and property optimization of novel magnetic field controlled functional materials through the external field treatment.

本申请项目以NiMnX（X = Ga、In、Sn等）基磁控形状记忆合金为研究对象，以合金的微观组织调控为出发点，将外应力引入到马氏体相变过程中，开展外应力作用于马氏体相变的晶体学研究。以EBSD为主要技术手段，结合原位中子衍射，在系统分析马氏体相变过程中施加外应力条件下的组织形貌学与晶体学特征的基础上，揭示外应力作用下的马氏体相变机制，阐明相变过程中的应变协调与变体选择机理，构建外应力作用于马氏体相变的晶体学理论模型，并进一步探讨外应力作用于马氏体相变的晶体学特征与磁感生应变的关联性及其影响规律和作用机制，以期为利用外场进行新型磁控功能材料的微观组织调控与性能优化奠定理论基础和提供技术支撑。

由于马氏体相变的晶格畸变具有强烈的晶体学各向异性特征，将外应力引入到马氏体相变过程势必会促进有利变体的择优形成而抑制不利变体的出现，从而实现对微观组织的调控。本申请项目以NiMnX（X = Ga、In、Sn等）磁控形状记忆合金为研究对象，以合金的微观组织调控为出发点，将外应力引入到马氏体相变过程中，开展应力场与温度场耦合条件下的相变晶体学研究。以EBSD为主要技术手段，结合原位中子衍射，解析了应力场与温度场耦合条件下的马氏体组织形貌学与晶体学特征，阐明了相变过程中的应变协调与变体选择机理，实现了基于外场训练的磁感生应变调控，并探索了多晶合金的弹热效应。项目实施以来，共发表SCI期刊论文27篇。

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