Electropulsing-induced phase transformations in a Zn–Al-based alloy

Microstructural changes and phase transformations of an electropulsing-treated (EPT) ZA22 alloy wire were studied using scanning electron microscopy and transmission electron-microscopy techniques. Two stages of phase transformation were detected in the EPT alloy: (i) quenching from the as furnace-cooled (FC) state to the final stable state and (ii) up-quenching from the final stable state back to the as FC state through two reverse phase transformations: T′ + η → α + ε and η′_T + ε + α → η′_FC. Electropulsing accelerated phase transformation tremendously. It was at least 1200 times faster than the aging process. The mechanism of the electropulsing-induced phase transformations is discussed from the point of view of Gibbs free energy and electropulsing kinetics.