Deformation behavior of β_1 phase in polycrystalline CuAlMnZnZr shape memory alloy with wide transformation hysteresis

摘要

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 β_1 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 β_1 phase are 11 % and 550 MPa, respectively. For the alloy, there is a characteristic deformation temperature (between M_s + 10℃ and M_s + 60℃) and a strain range (between 6.5 and 9.0%). In this case, deformation can effectively increase the transformation hysteresis (more than 90℃), while the strain recovery ratio remains practical high (more than 3.7%).