Deformation behavior of β1 phase in polycrystalline CuAlMnZnZr shape memory alloy with wide transformation hysteresis

The stress-induced martensite transformation in Cu-18.4Al-8.7Mn-3.4Zn-0.1Zr alloy (at%) has been studied by means of tensile test, electrical resistivity curve measurement, in situ metallographical observation, X-ray diffraction and TEM observation. By applying stress to the uniform β1 matrix, two or more groups of differently oriented martensitic variants are stress-induced inside one grain. With further increase of stress, they coalesce into a single oriented variant martensitic phase or form complicated cross-like configuration. The elongation and the ultimate tensile strength of the tested CuAlMnZnZr alloy as-quenched in the ordered β1 phase are 11% and 550 MPa, respectively. For the alloy, there is a characteristic deformation temperature (between Ms + 10 °C and Ms + 60 °C) and a strain range (between 6.5 and 9.0%). In this case, deformation can effectively increase the transformation hysteresis (more than 90 °C), while the strain recovery ratio remains practical high (more than 3.7%).