Mechanism of phase refinement and its effect on mechanical properties of a severely deformed dual-phase Mg-Li alloy during annealing

摘要

Microstructure evolution of severely cold rolled dual-phase Mg-Li alloy during annealing at various temperatures was systemically investigated. The results showed that severely deformed α-Mg phase can be significantly refined by annealing process. α-Mg phases were first stratified into various layers by phase transformation from α-Mg phase into β-Li phase. Low angle grain boundary was more easily inducing phase transformation compared to high angle one during annealing, α layers continuously broken into chains of α grains at high annealing temperature, which is controlled by the motion of triple junction at the intersection of phase and grain boundary. Grain boundaries exhibited a high interface tension compared to phase boundary, which drove the globulari-zation of α-Mg grains. Mechanical properties and strain hardening behavior were influenced by phase refinement. Coordination of grain refinement and phase refinement promoted the ductility of dual-phase Mg-Li alloy without a remarkable decrease in strength.