Abstract:In order to prepare high-performance Mo with fine and homogeneous microstructure to meet the demand of high-technology applications such as metallurgical, mechanical, national defense, aerospace and electronics applications, the microwave sintering process and densification mechanism of Mo nanopowder were studied. In this experiment, Mo nanopowder and micropowder were used for conventional sintering and microwave sintering at different sintering temperatures and sintering time, respectively. The results showed that with the increase in the sintering temperature, the increase rates of the relative density and hardness increased rapidly at first and then slowed down. The relative density rapidly reached 95%, followed by a small change. Mo nanopowder with a relative density of 98.03% and average grain size of 3.6 μm was prepared by microwave sintering at 1873 K for 30 min. According to the analysis of the sintering kinetics, its densification is attributed to the combination of volumetric diffusion and grain boundary diffusion mechanisms. The calculated sintering activation energy of Mo nanopowder was 203.65 kJ/mol, which was considerably lower than that in the conventional sintering, suggesting that the microwave sintering was beneficial to the enhancement in the atom diffusion and densification for the powder. The results confirm that the microwave sintering is a promising method to economically prepare molybdenum with high properties.

Key words: molybdenum; microwave sintering; nanopowder; densification kinetics; diffusion mechanism