Effects of solute redistribution during heat treatment on micro-galvanic corrosion behavior of dilute Mg-Al-Ca-Mn alloy

The underlying mechanism of solute redistribution during heat treatment in affecting corrosion behavior of Mg-1.19Al-0.28Ca-0.44Mn (wt%) alloy was systematically clarified. The supersaturated Al and Ca solutes in matrix effectively alleviate the driving force of micro-galvanic corrosion caused by Al-Mn phases, based on positive shift of matrix potential and film densification. After aging treatment, monoatomic-layer G.P. zones realize higher strength and better corrosion resistance of alloy as compared to nanosized Al2Ca, due to higher number density and less solute consumption in matrix. Our work provides guidance to minimize corrosion loss of Mg by regulating nucleation and growth of precipitates.