Effect of hydrogen on the shape memory effect and transformation behavior of Ti-Ni alloy

Abstract

A study has been made of the effect of hydrogen on the shape memory effect and transformation behavior of Ti-Ni alloy. The material was evaluated in the temperature range from 300 to 473 K using a bent specimen. The transformation behavior was analyzed by differential scanning calorimetry (DSC) and X-ray diffraction technique. The results obtained are as follows: The shape recovery rate is markedly decreased by a small amount of hydrogen which does not cause the increase in hardness. The shape recovery occurs even below the transformation temperature (As) in the material charged with hydrogen for a relatively long time, resulting from a hydride formation. It is found that the hydrogen causes a considerable decrease in the heat of the transformation and only a slight decrease in the transformation temperature. The heat of transformation and the transformation temperatures before hydrogenation is restored by holding the hydrogenated material at 753 K for 300 s. Two types of the hydrides form during charging at a current density of 1000 A/m2.