Degradation of tensile strength of Ni–Ti superelastic alloy due to hydrogen absorption in methanol solution containing hydrochloric acid

Degradation of tensile strength of a Ni–Ti superelastic alloy due to hydrogen absorption has been studied in methanol solution containing 0.1 mass % hydrochloric acid (HCl). The amount of absorbed hydrogen from the solution was measured by thermal desorption analysis (TDA). Hydrogen desorption of immersed specimens appeared in the temperature range from 100 to 600 °C. The amounts of absorbed hydrogen of immersed specimens were in the range of 50–500 mass ppm when immersed in the solution for 8–120 h. Tensile strength of immersed specimens decreased abruptly up to immersion time of 24 h. In the immersion time range from 24 to 120 h, the tensile strength was coincident with the critical stress for martensite transformation. It was concluded that the degradation of tensile strength of a Ni–Ti superelastic alloy is caused by hydrogen absorption in methanol solution containing HCl.