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在自制的定向凝固炉中,用带引晶器的石墨模壳制备出Ti-50.0at%Ni单晶。利用光学显微镜(OM)、扫描电镜(SEM)及其配置的能谱(EDS)仪研究合金的铸态组织,通过X射线衍射(XRD)和极图分析确定单晶晶粒取向,利用自制模具对合金的记忆性能进行评价。结果表明:试样横截面与纵截面均呈枝状晶分布特征,枝晶生长方向与定向凝固方向基本一致,未出现晶界,单晶横截面法向与[111]取向夹角为15°。由于消除了晶界对马氏体相变的不利影响,同时[111]取向是TiNi合金能获得较大可恢复应变的择优取向,与普通铸造的TiNi多晶相比,材料的形状记忆最大可恢复应变和记忆疲劳性能都得到一定提高。
In a self-made directional solidification furnace, a Ti-50.0 at% Ni single crystal was prepared using a graphite mold shell with a priming mold. The as-cast microstructure of the alloy was investigated by optical microscope (OM), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The orientation of single crystal grains was determined by X-ray diffraction The memory performance of the alloy was evaluated. The results show that both the cross section and the longitudinal section of the sample show dendritic crystal distribution. The dendrite growth direction is basically the same as that of the directional solidification. No grain boundary occurs. The included angle between the normal direction of the single crystal and the [111] orientation is 15 ° . Due to the elimination of the adverse effect of the grain boundary on the martensitic transformation, the [111] orientation is the preferred orientation for greater recoverable strain in TiNi alloys. Compared with TiNi polycrystal castings, the maximum shape memory Recovery strain and memory fatigue performance have been improved.