CuZnAl single crystals pseudoelastic behaviour under biaxial tensile loading: Observations and analysis

Abstract
On one part, lattice parameters of a 66.84Cu 23.73Zn 9.4Al at.% alloy in austenite A and martensite M phases are measured. Using the mathematical crystallographic theory of the phase transformation, the nature of the phase transformation is determined. One obtains thus an exact interface between parent phase and untwinned martensite like the shape strain vector and habit plane normal. Proportional biaxial loadings on a single crystal plate confirm these calculations. On a second part, based on the hypothesis of the phase transformation maximal work, a phase transformation yield surface (A->M) is set up. A homogenisation process neglecting the grains interactions is used to identify the polycrystal yield surface. The cornparison with experimental results obtained under tension/torsion or tension (compression)/internal pressure is fairly good.