Effect of Mixing Modes and Nano Additives on the Densification and Sintering Behavior of Tungsten Material Under Spark Plasma Sintering

The influence of 0.5 wt% nano tungsten and different mixing (turbular and magnetic mixing) on the densification, microstructure, microhardness and dilatometric properties, of tungsten materials was investigated under spark plasma sintering. The dilatometric analysis confirms that sintering process was started at 1100 A degrees C for magnetic mixed samples but there were no sign of sintering for samples after turbular mixing. Nano tungsten and magnetic mixing increased the density of tungsten up to 98.5% at 1400 A degrees C with the increased micro hardness value of 592 HV. The major impact after magnetic mixing is morphology changes in tungsten, development of active sites on the surface, breakdown of agglomerates and even distribution of nanoparticles throughout the bulk tungsten powder. This facilitates the mass transfer between nano tungsten and bulk tungsten which results in the increase in the Laplace force which plays an important role in mass transfer diffusion process during sintering. As a result, it leads to an enhancement of densification process of tungsten powder mixture during sintering and, hence a decrease in the sintering temperatures. Thus, this is a novel approach to use magnetic mixing and nano tungsten to improve densification and sintering behavior of tungsten under spark plasma sintering.