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

On one part, lattice parameters of a 66.84Cu 23.73Zn 9.4Al at.% alloy in au stenite A and martensite M phases are measured. Using the mathematical crys tallographic theory of the phase transformation, the nature of the phase tr ansformation is determined. One obtains thus an exact interface between par ent phase and untwinned martensite like the shape strain vector and habit p lane normal. Proportional biaxial loadings on a single crystal plate confir m these calculations. On a second part, based on the hypothesis of the phas e 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 comparison with experi mental results obtained under tension/torsion or tension (compression)/inte rnal pressure is fairly good.