Dynamic electropulsing induced phase transformations in a furnace cooled Zn-Al based alloy (ZA22)

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 hep 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 upquenching), 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.