Rapid Solidification Of The Full Memory Effect Of Ni-ti Shape Memory Alloy

In this paper, Ti-51at%Ni shape memory alloys(SMAs) were prepared by means of Rapid Solidification Technology (copper-mold vacuum suction casting) and shape memory effect and microstructure were investigated by differential scanning calorimeter(DSC), X-ray diffraction(XRD), scanning electron microscope(SEM), etc. Constrained aging "training" method was used to obtain the All-round way shape memory effect(ARSME) of Ti-51at%Ni SMAs. The change of microstructure and the influence of constrained aging temperature and time on ARSME during constrained aging process were investigated. The results show:1. There are two transformations(reverse martensitic transformation and reverse R-phase transformation) in Ti-51at%Ni SMA during the heating process, which are separated each other. As(Ms) decrease sharply.2. The microstructure of Ti-51at%Ni SMA is characteristic of super-fine grain and two-columnar crystal which growed from the alloy's surface to center. Intensive-texture is found in alloy. There is B2 (typical CsCl type) structure in the substrate in room temperature. There are not ARSME and TWSME in alloy.There is sharp OWSME with big recovery rate and high respondence in alloy.3. There is TWSME in the alloy After 300℃ constrained aging; Gradual change form TWSME to ARSME as aging time increases occurs after 400 ℃ aging; There are different ARSMEs after 500 ℃ aging, which depends on aging time and increases first and then decreases as the aging time increases; There is only OWSME after 600℃ aging.4. There are two transformations in ARSME after constrained aging treatment: martensitic transformation and R-phase transformation. Constrained aging temperature and time have remarkable influence on martensitic transformation, but there is little effect on R-phase transformation.5. The alloy consists of parent B2, Ti₃Ni₄ phase and few martensite-phase after constrained aging treatment and its structure has not distinctive change. The...