Abstract
This paper investigated the microstructure of AlN particles reinforced AZ91D Mg-based metal-matrix composites (MMCs). The AZ91D is initially placed inside a graphite crucible and heated to 680-700°C in a resistance-heated furnace. The molten alloy is stirred with a vane operated at 350 rev./min for 3 minutes. Preheated AlN particles are simultaneously added to the stirred alloy with addition of 1, 2 and 5 wt. % of 1 ?m AlN particles. The microstructure of the AZ91D and AlNp reinforced AZ91D Mg MMCs specimens were observed by optical microscope. The mean grain size was determined using the linear intercept method. The clear microstructure of the eutectic structure is observed by polarization microscope. It was found that the ?-phase Mg was almost eliminated through homogenization by SEM observation.