Thermal cycling and shape memory characteristics in (85-X)Ti-Xni-15Hf alloys

摘要

In previous research, martensitic transformationstart temperature of 35Ti-50Ni-l5Hf alloy was highest among (50-X)Ti-Ni-XHf(X = O~2O at.%) alloys. In this research, shapememory characteristics of (85-X) Ti-XNi-15Hf(X = 48~51 at.%)alloys were investigated by means of X-ray diffractometry,differential scanning calorimetry and thermal cycling test underconstant load. Stress dependence of transformation temperaturewas increased with increasing Ni content. The maximumrecoverable elongation was decreased with increasing Ni content.Residual elongation did not occur under applied stress of 120 MPain both 36Ti-49Ni-l5Hf and 35Ti-5ONi-l5Hf alloys. Agingtemperature dependence of transformation temperature in 37Ti-48Ni-l5Hf, 36Ti-49Ni-15Hf, 35Ti-5ONi-l5Hf and 4OTi-5ONi-lOZr alloys was lower than that of a Ti-Ni binary alloy. Thermalcycling dependence of transformation temperature in a 37Ti-48Ni-l5Hf alloy was lower than that of a 40Ti-50Ni-lOZr alloy.