Microstructure and lattice parameters of AlN particle-reinforced magnesium matrix composites fabricated by powder metallurgy

Abstract

Magnesium matrix composites reinforced with AlN particles were fabricated by the powder metallurgy technique. The evolution of lattice constants and solid solubility levels of Al in a-Mg and the microstructure of Mg-Al/AlN composites were investigated in the present study. The results showed that the solid solubility of Al in a-Mg reached a relatively high level by the P/M process with a long time of milling. X-ray diffraction showed that the peaks of Mg phase clearly shifted to higher angles. The lattice constants and cell volume decreased significantly compared with those of standard Mg due to a significant amount of Al incorporated into a-Mg in the form of substitutional solid solution. The degree of lattice deformation decreased at a low sintering temperature and increased at higher sintering temperatures due to the presence of AlN. Microstructural characterization of the composites revealed a necklace distribution of AlN particles in the Mg matrix. Heat treatment led to precipitation of Mg17Al12 from the supersaturated a-Mg solid solution. The precipitate exhibited granular and lath-shaped morphologies in Mg matrix and flocculent precipitation around AlN particles.