Compression-induced hexagonal martensite in Cu–Zn–Al

The martensitic transformations occurring in β Cu–8.54at.%Zn–21.75at.%Al single crystals with e/a=1.52 are studied by compressive pseudoelastic cycles, optical and electronic microscopy. A change between serrated to smooth transformation behaviour is observed at T–Ms around 20 K. Once a critical volume of 18R martensite has formed, 2H martensite is induced in a β-18R mixture at temperatures between Ms and T–Ms=71 K. The pseudoelastic cycles exhibit high stress hysteresis and the 2H phase is retained on unloading. The experimental habit plane of the 2H martensite matches with that calculated from the phenomenological theory. Two 2H variants are mainly formed, which are comparable with those induced by tension from 18R single crystals.