Recrystallization and Precipitation of β-Mg17Al12 Phase of the Cold-Rolled Mg-9Al-1Zn Alloy Strip during Isothermal Annealing

Abstract

Effect of isothermal annealing on the microstructure evolution of the cold-rolled Mg-9Al-1Zn alloy strip was investigated. It is found that the competition between the precipitation of β-Mg17Al12 phase and recrystallization of α-Mg matrix occur under the conditions of various annealing temperature and time. At a low annealing temperature (523K), the β-Mg17Al12 particles precipitate preferentially at locally high deformation area and grow into the lamellar-cluster with an increase in the annealing time, retarding the recrystallization of α-Mg matrix. With raising the annealing temperature (573~623K), both the precipitation of β-Mg17Al12 particles and recrystallization of α-Mg matrix take place. Both recrystallization and grain growth are prone to proceed without precipitation of β-Mg17Al12 particles when the annealing temperature is 673K. A mechanism for the competitive behavior between the precipitation of β-Mg17Al12 phase and recrystallization of α-Mg matrix at various annealing conditions is discussed.