Electron irradiation-induced evolution of the martensitic transformation characteristics in a CuZnAl shape memory alloy

Abstract

CuZnAl shape memory alloy samples were irradiated by 1.7 MeV electrons under the parent and martensite phase, respectively. The transformation temperatures were measured by differential scanning calorimetry (DSC). The effect of electron irradiation on the ordering degree was studied by X-ray diffraction (XRD) by estimating the spacing difference (Δ d) of some selected pairs of diffraction planes. The damage accumulation was determined by positron annihilation technology (PAT). The results showed that irradiation under the parent phase produced no change in the transformation temperatures. The reverse martensite transformation temperatures ( A s and A f) shift to higher temperature of samples and increase with increasing electron doses when irradiation was performed under the martensite phase. The XRD results showed irradiation under the parent phase produces little change in Δ d, but Δ d decreased for the CuZnAl samples irradiated under the martensite phase, this implied that the ordering degree of the martensite decreased after the irradiation under the martensite phase. The PAT results showed that the concentration of vacancy clusters increased after irradiation. It is thought that the martensite stabilization is related to the decreasing of ordering degree in the martensite state.