Microstructure and corrosion behaviors of AZ63 magnesium alloy fabricated by accumulative roll bonding process

Abstract

AZ63 magnesium alloy sheets were fabricated by accumulative roll bonding (ARB) process at 350 °C up to 5 cycles. The aim of this work is to study the effect of ARB process on the microstructure and corrosion behavior of AZ63 magnesium alloy. The ARBed sheets were investigated via microstructure observations, electrochemical tests, hydrogen evolution measurements and immersion tests. After ARB process, the average grain size decreased. The coarse Mg17Al12 phase was broken under the action of rolling force and it distributed more dispersed in the magnesium matrix. The corrosion resistance of samples increased significantly with increasing the number of ARB cycles. The influence of microstructure on the corrosion behaviors was discussed. Fine grain produced more passive oxide layers which acted as a corrosion barrier. The Mg17Al12 phase acted primarily as a micro-galvanic cathode during the corrosion process because of its low volume fraction and isolated distribution. The volume fraction of Mg17Al12 phase decreased after ARB process, which results in the reduction of the effect of galvanic corrosion.