Fracture Analysis of Hydrogen-Charged Nickel-Titanium Superelastic Alloy

Abstract

Superelastic Ni–Ti alloys are widely used as engineering and medical materials. However, the alloy is susceptible to environmental embrittlement in a corrosive atmosphere. Accelerated tests of hydrogen embrittlement of the Ni–Ti alloy were carried out. The effect of electrolytic charging hydrogen on the properties of the alloy was measured. The rupture process in tension of the alloy with charged hydrogen was discussed on the basis of the tensile stress-strain curve, hardness in a cross-sectional area and fractography. The results of the measurements suggested that hydrogen concentration on the surface of the alloy and immersion time in an electrolytic bath had different effects on embrittlement. This will be related with the distribution of the hydrogen concentration, which was determined from the diffusion equation and boundary conditions.