共晶型Ti5Si3/TiNi记忆合金复合材料变形机制与界面结构研究

Based on the eutectic transformation of Ti5Si3-TiNi system, by preliminary exploration, the Ti5Si3/TiNi shape memory composite with controllable transformation temperature and volume fraction was obtained. It was found that the composite containing brittle Ti5Si3 phase (there is no plastic deformation at room temperature) showed unconspicuous yielding and high strain harding on the compressive stress-strain curve. The compressive plastic deformation was about 35% and the fracture strength was about 2.5 GPa, which were higher than those of the TiCuNiSnNb nanostructure-dendrite composite with enhanced plasticity reported on the Nature Materials. It was noted that the Ti5Si3 exhibited an large lattice elastic strain about 2.1% in the eutectic composite, which was different from the previous reported bulk Ti5Si3 that has an ealstic strain limit less than 1%. It was also found that there was a specific orientation reationship between the TiNi phase and Ti5Si3 phase. This project intends to investigate the deformation behavior of the Ti5Si3/TiNi composite, recognize the microscopic deformaition behavior of nano-scale Ti5Si3 phase in the matrix deforming by shear deformation，physical mechanism of the compounding damping, recognize the deformation， reveal the interface dislocation sturcture of the composite. This research is expected to be a high-quality academic achievement..

基于Ti5Si3-TiNi共晶型相变思路, 经前期探索，在国际上首次获得了复合比与相变温度可控的Ti5Si3/TiNi 记忆合金复合材料。并发现含硬脆性Ti5Si3相（室温没有塑性）的过共晶Ti5Si3/TiNi 复合材料压缩应力-应变曲线呈现不明显屈服与高应变强化现象，且压缩塑性变形达35%、断裂强度达2.5GPa，均高于Nature Materials报道的枝晶相增塑纳米晶复合材料的塑性与强度。更为值得关注的是，我们初步发现存在于切变型变形基体中的Ti5Si3相与以往报道不同，在室温压缩变形过程中，其点阵弹性应变可达2.1%（块体Ti5Si3的弹性变形仅为1%）。同时，TiNi相与Ti5Si3相之间存在特定的位向关系。本项目拟研究TiSi3/TiNi复合材料的变形行为，认知切变型变形基体中纳米尺度硬脆相的微观变形行为，揭示基体与硬脆相的界面位错结构，可望获得高质量学术成果

采用熔炼获得了Ti5Si3/TiNi记忆合金复合材料。研究表明，过共晶复合材料由初生TiNi相和共晶组织（TiNi+Ti5Si3）组成，共晶Ti5Si3/TiNi复合材料中TiNi片层厚度约130nm，Ti5Si3片层厚度约在50nm。过共晶Ti5Si3/TiNi复合材料的断裂强度可达2.5GPa，压缩塑性应变达35%。共晶复合材料的压缩断裂强度和塑性均有所下降。复合材料的压缩应力应变曲线均表现出两段加工硬化现象。当TiNi基体为马氏体相时，在压缩加载初始阶段，TiNi马氏体相发生弹性变形与变体取向过程，Ti5Si3发生弹性变形，继续加载TiNi相发生塑性变形，Ti5Si3则产生裂纹，在整个压缩变形过程中，Ti5Si3点阵弹性应变最大可达2.1%。利用O点阵理论计算了Ti5Si3与TiNi记忆合金界面的位错结构，由于两组元匹配良好，界面存在较大近重位点区域，在近重位点区域之间存在一组位错，位错间距大约为20nm。. 经熔炼、锻造、拔丝制备出Nb纳米线/TiNiCu记忆合金复合材料，复合材料展现出低弹性模量、高屈服强度和大弹性应变极限。当基体发生应力诱发相变时，纳米线的弹性应变最大可以达到约5%，当基体发生塑性变形与马氏体相变混合变形时，纳米线依然可以展现大约3%的弹性应变。. 通过电弧熔炼制备了TiNbSn合金，研究结果表明，随着Nb含量的增加，(Ti87Sn13)100-xNbx合金组织由β相和Ti3Sn两相转变为单一β相。合金固溶处理后析出大量Ti3Sn，并且弹性模量随着固溶温度的升高先减小后增大。铸态(Ti90Sn10)100-xNbx合金随Nb含量的增加组织由单一α相转变为单一β相，合金固溶处理后析出Ti3Sn，并且弹性模量随固溶温度的升高而降低。随着Nb含量的增加，铸态(Ti93Sn7)100-xNbx合金组织由大量α相和少量β相组成转变为由单一β相组成。