Effect of a Small Amount of Hydrogen on the Pseudo-Elastic Properties of Ti-Ni Alloy

Abstract

The effect of a small amount of hydrogen on the cyclic pseudo-elastic properties of a Ti-Ni alloy has been studied. A cyclic test machine and control systems were constructed for the study. A decrease in the pseudo-elastic properties due to the absorption of a small amount of hydrogen was observed. Hydrogen seems to reduce or shift the stress-temperature range for the appearance of pseudo-elasticity. The changes in pseudo-elastic properties during the cyclic test were attributed to the accumulation of plastic strain at local regions such as grain boundaries and hydrogen induced decrease in the critical stress for slip deformation. Hydrogen is thought to have an interaction with dislocations and lead to the local formation of stress induced martensites. Dissolved or trapped hydrogen, or both, are supposed to have played an important role during the processes.