2010 Volume 51 Issue 11 Pages 1997-2004
Multi-phase identification and phase transformations in a dynamic electropulsing treated Zn-Al based alloy (ZA22) were studied by using backscattered scanning electron microscopy (BSEM) and electron back-scattered diffraction techniques (EBSD). By using EBSD, two hcp phases η′S and η′T with a small difference of about 1% in lattice parameters (c/a) were discriminated. Two stages of phase transformations: (a) η′S→η′T+ε′T+α′T and ε+α→T′+η (in a way of quenching), and (b) T′+η→ε+α and η′T+ε′T+α′T→η′S (in a way of up-quenching), were detected. It was found that dynamic electropulsing was less effective in accelerating phase transformations than static electropusling. The mechanism of dynamic electropulsing induced phase transformations is discussed from the point view of Gibbs free energy and electropulsing kinetics.