Microstructural evolution and mechanical response of Cu–Al–Be–B shape memory alloy processed by repetitive equal channel angular pressing

Equal channel angular pressing (ECAP) was applied to modify the microstructures of Cu–Al–Be–B shape memory alloys (SMAs). The alloy was greatly refined because of the interaction of the large plastic deformation and physicochemical effects. With an increase of ECAP passes, the specimens showed a change from plastic fracture to brittle fracture, increased proportion of transgranular fracture, and decreased ultimate strength from 460 MPa to 340 MPa. These were caused by the precipitation of the γ2-phase and the disappearance of thermoelastic martensite. After appropriate heat treatment, the content of thermoelastic martensites increased, while the grain size remained smaller than that of the as-cast alloy. Further tests showed that the ultimate strength of this alloy improved to 703 MPa and the attenuation of shape recovery ratio was alleviated.