Effect of constituent phase of Ni–Ti shape memory alloy on susceptibility to hydrogen embrittlement

The susceptibility of a Ni–Ti shape memory alloy towards hydrogen embrittlement has been examined with respect to the constituent phase of the alloy. Fracture always occurred in the presence of martensite. A steep decrease in fracture stress took place initially with increasing hydrogen content irrespective of the initial phases. The effect of the constituent phase appeared at high hydrogen contents. The work-hardened martensite phase showed the highest susceptibility succeeded by the parent phase that fractured in the course of martensite transformation. The critical stress for the martensite transformation increased at high hydrogen contents. The embrittlement is likely to be enhanced by the interactions between hydrogen and dynamic processes in materials.