多晶Ni-Mn-Ga-Gd高温记忆合金的双程形状记忆效应

Ni-Mn-Ga高温记忆合金具有双程形状记忆效应，沿其单晶的某些方向可获得极大的双程可逆应变，是一种发展潜力巨大的高温记忆合金。但关于多晶Ni-Mn-Ga高温双程记忆效应的研究目前仍未完全展开。申请者的前期研究发现，硬性第二相有利于提高多晶Ni-Mn-Ga合金的双程形状记忆效应，因此本项目拟采用Gd掺杂方法引入硬性第二相，制备多晶双相Ni-Mn-Ga-Gd高温记忆合金。研究第二相对双程形状记忆效应及其热稳定性的影响规律和微观机制，确立最佳合金成分设计准则；阐明热机械训练方法对双程形状记忆效应的影响规律和物理本质，优化训练工艺，提高双程形状记忆效应；采用定向凝固方法制备取向多晶，研究晶粒取向对双程记忆效应的影响，进一步提升双程形状记忆性能；建立合金制备与热机械训练工艺、双程形状记忆效应及热循环稳定性的内在联系，研制出具有高热稳定性、大双程形状记忆效应的高温记忆合金。

Ni-Mn-Ga high-temperature shape memory alloy (HTSMA) exhibits two-way shape memory effect (TWSME), and a large two-way reversible strain can be obtained along the certain direction of some single crystal Ni-Mn-Ga, which makes it become a potential HTSMA. However, the TWSME of polycrystalline Ni-Mn-Ga HTSMA has not been widely researched. The applicant's previous studies have found that the hard second phase introduction is advantageous to TWSME of polycrystalline Ni-Mn-Ga. Thus, hard second phase is formed by rare earth Gd doping, and polycrystalline Ni-Mn-Ga with dual-phase is obtained in the present project. The influence and mechanism of second phase on TWSME and thermo-stability is studied to establish the best criteria of composition. The influence and physical nature of thermomechanical training method on TWSME is investigated, and the training method is optimized to improve TWSME. The oriented polycrystalline Ni-Mn-Ga is prepared by directional solidification. In order to further enhance the two-way shape memory properties, the effect of grain orientation on TWSME is observed. The relationship among the process of preparation and thermomechanical training, TWSME and thermo-stability is bulit up. The HTSMA with high TWSME and high thermo-stability is developed.