Abstract:Magnesium aluminum alloy materials were fabricated via powder metallurgy. Microstructural evolution, thermal stability, tensile properties and fracture mechanism of the hot extruded magnesium alloys were investigated. Microstructural observation revealed that all alloys have fine equiaxed grains due to dynamic recrystallization during hot extrusion with Mg17Al12precipitating along grain boundaries. The DSC analyses exhibited that because diffusion rate of Al into Mg is slow in solid state sintering process, Al concentration in localized region after sintering is still high enough to cause eutectic reaction. The tensile test showed that 0.2% yield strength, ultimate tensile strength and elastic modulus increase and elongation decrease with increasing Al content. Mg-9%Al obtains the best combination of mechanical properties among the investigated alloys. Fracture surface observation showed ductile fracture to be a dominant failure mode. Abundant dimples and tear ridges are found in the fracture surfaces. Grain boundary weakening results from the precipitate Mg17Al12caused intergranular cracks during tensile test.

Key words: magnesium alloys; mechanical properties; powder metallurgy; hot extrusion