Study of the Ni_41.3Ti_38.7Nb₂₀ Wide Transformation Hysteresis Shape-Memory Alloy

Author： He Xiang-Ming Rong Li-Jian Yan De-Sheng Jiang Zhi-Min Li Yi-Yi

ISSN： 1543-1940

Source： Metallurgical and Materials Transactions A, Vol.35, Iss.9, 2004-09, pp. : 2782-2787

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Abstract

The shape-memory characteristics in the Ni_41.3Ti_38.7Nb₂₀ alloy have been investigated by means of cryogenic tensile tests and differential scanning calorimetry measurement. The martensite start temperature M_s could be adjusted to around the liquid nitrogen temperature by controlling the cooling condition. The reverse transformation start temperature A_s′ rose to about 70 °C after the specimens were deformed to 16 pct at different temperatures, where the initial states of the specimens were pure austenite phase, martensite phase, or duplex phase. The shape-memory effect and the reverse transformation temperatures were studied on the specimens deformed at (M_s - 30 °C). It was found that once the specimens deformed to 16 pct, a transformation hysteresis width around 200 °C could be attained and the shape recovery ratio could remain at about 50 pct. The Ni_41.3Ti_38.7Nb₂₀ alloy is a promising candidate for the cryogenic engineering applications around the liquid nitrogen temperature. The experimental results also indicated that the transformation temperature interval of the stress-induced martensite is smaller by about one order of magnitude than that of the thermal-induced martensite.