Effects of current density on electropulsing-induced phase transformations in a Zn-Al based alloy

Phase transformations of an electropulsing-treated ZA22 alloy were studied after tensile deformation by using scanning electron microscopy and transmission electron microscopy. It was found that electropulsing tremendously accelerated phase transformations consequentially in the two stages: (a) quenching from supersaturated state approaching the final stable state, i.e., α+ε→T′+η, and (b) up-quenching from the final stable state to a higher temperature state, i.e., T′+η→α+ε. The mechanism of electropulsing-induced phase transformation is discussed from the point of view of Gibbs free energy, and electropulsing kinetics.