Studies on the Effect of Processing Parameters on Microstructure and Properties of Magnesium Compacts Prepared via Powder Metallurgy

The present study involves the investigation on the effect of processing parameters of powder metallurgy on the microstructure and hardness characteristics of the green as well as sintered specimens of magnesium. The processing parameters include the high-energy ball milling time, compaction pressure, and sintering temperature. From SEM images of 1, 3, and 5 h ball-milled powders, it is revealed that the sequence of change of morphology and size of particles is: flattening (formation of lamellas), fracturing (cracking of lamellas), and dynamic balance (adherence of a small particle with other particles and fracturing), respectively. The average particle size decreases with increasing ball milling time. 0, 1, 3, and 5 h ball-milled powders are compacted at different pressures. It is found that green density of the compacts of ball-milled powders depends on the morphology of powder particles, particle size, and compaction pressure. The selected samples were sintered at 500, 550, and 600 °C for 1 h. SEM characterization indicates that grain growth occurs with increasing sintering temperature. With constant mass, the sintering theory indicates that grain growth of larger particles takes place at the expense of smaller particles due to the difference of surface curvature. The density and hardness of sintered samples were calculated by using Archimedes principle and Vickers hardness tester, respectively.