Optimization of heating rate on hybrid microwave sintering of the PM Fe-Cr MMCs reinforced with Al<inf>2</inf>O<inf>3</inf>particle

This study reports the optimization of heating rate on the microwave sintered Fe-Cr-Al2O3 metal matrix composite (MMC). The heating rate was selected between 10°C/min to 60°C/min with increment of 10°C/min respectively. The samples were fabricated via PM route and microwave sintering was carried out in a tubular microwave furnace HAMiLab-V3 in N2 atmosphere purposely to avoid any oxidation and chemical reaction to samples. The microstructure of sintered samples was evaluated using SEM and bulk density and porosity were determined based on ASTM B962 - 17 and the microhardness were determined based on ASTM E384. The optimized heating rate of the sample was selected based on the micro hardness value and total porosity percentage as well as based on SEM microstructure analysis. The results revealed that the optimum heating rate occurred at 20°C/min due to the highest value of hardness achieved which is about 119.28 HV with at the highest bulk density about 6.07 g/cm3 and at the lowest total porosity about 14.55%. SEM micrographs also showed that the diffusion was mostly effective at 20°C/min heating rate compared to others, indicated that significant grain boundary diffusion of Fe matrix into Al2O3 particle was occurred.