Thermal Stability of Ultra-fine Grained AZ31 Magnesium Alloy Processed by Severe Plastic Deformation
Abstract
The microstructure of ultra-fine grained (UFG) magnesium alloy AZ31 and its development with temperature were investigated. UFG specimens were prepared by a combined two-step severe plastic deformation process: the extrusion (EX) and the equal-channel angular pressing (ECAP).
This combined process leads to microstructure refinement and enhanced microhardness. The microstructure evolution and mechanical properties were studied by light and scanning electron microscopy and microhardness measurements.
Specimens were annealed for 1 hour at temperatures of 150, 200, 250, 300, 350, 400, 450, 500 oC. No changes were observed after annealing at 150 oC.
The coarsening of a fine-grained structure at higher temperatures was accompanied by a gradual decrease of the microhardness. Microstructure of the specimens annealed at 450 oC and 500 oC is very non-homogeneous due to the secondary recrystallization.