Effects of tungsten disulfide on microstructure and mechanical properties of AZ91 magnesium alloy manufactured by stir casting

In this work, AZ91 magnesium alloy reinforced with a low fraction (0-1) wt.% tungsten disulfide(WS2) microparticles have been fabricated using stir casting method. Effects of WS2 microparticles on mechanical properties, microstructure, and their correlation have been analyzed. The microstructure of composites has been investigated by scanning electron microscope (SEM) equipped with energy dispersive spectroscopy (EDS) and X-ray diffractometer. Results indicate that density, hardness, ultimate tensile strength (UTS), and tensile ductility have a direct relation with reinforcement (WS2) contents and has optimal value for 0.6 wt% WS2/AZ91 composites then slightly decrease afterward. The UTS and hardness of 0.6 wt%WS2/AZ91 were increased by 23.23% and 10.65% respectively with respect to monolithic AZ91. The ultimate compressive strength(UCS) is directly related with WS2 concentration and 10.07% enhancement in UCS for 1 wt%WS2/AZ91 composites have been noted. The trend is interlinked with density and hardness of composites. SEM images depict, WS2 micro-particles suppress beta-Mg17Al12 precipitates, refine the microstructure and enhance the grain size resulting in an increase in mechanical properties. The improvement in microstructure and mechanical properties is attributed to the dispersion of WS2 particles which hinder the grain growth. The increase in porosity has causes the decrease in mechanical behavior of 1 wt%WS2/AZ91. Twin boundary fracture has been found major fracture phenomenon in fractured WS2/AZ91 surfaces. (C) 2019 Elsevier B.V. All rights reserved.