Comparative Investigation of Microwave Hybrid and Conventional Sintering on the Densification, Microstructure, and Phase Evolution of Magnesium-, Vermiculite-, and Tungsten-Based Powder Metallurgy Composites

Abstract

The process of microwave hybrid sintering has come out as a potential substitute for the traditional method of sintering by means of furnace due to the advantages offered by rapid volumetric heating, energy efficiency and densification characteristics. In the present research work, a comparative study on the densification performance, microstructural analysis, surface integrity and phase formation of microwave sintered and conventional furnace sintered magnesium, vermiculite and tungsten powder metallurgy composites have been conducted. Compacts were prepared using powder metallurgy techniques and subjected to processing under similar conditions through microwave hybrid heating and conventional furnace sintering. Effect of sintering temperature (500-900°C), reinforcement content (1.0-2.0 wt.%) and holding time (3-6 minutes) on densification and porosity were studied systematically. The microstructural studies were conducted using optical microscopy and the phase formation was analyzed using X-ray diffraction (XRD). It has been observed from the experimentation that the process of microwave sintering resulted in better densification with bulk density of 7.88 g/cm³ and porosity of 20.42%. Optical microscopy showed improvements in particle bonding, pore refinement, better formation of necks, and homogeneity in the microstructure in comparison with the traditionally sintered samples. XRD results proved successful creation of crystalline phases in both composite systems, where the effect of reinforcement was very evident in the composition of phases and peak intensity. This superiority of microwave sintering can be explained by volumetric heating, which facilitates fast diffusion and homogenization of particles. Generally, microwave hybrid sintering shows great prospects for production of composites based on magnesium, vermiculite, and tungsten.