Influence of MoS₂ nanoparticles on tribo-mechanical characteristics of stir-squeeze cast AA7075/MoS₂ metal matrix composites 

This research explores the ability of Molybdenum Disulfide (MoS₂) nanoparticles to enhance the mechanical and tribological properties of AA7075. A novel stir-squeeze casting technique was employed to fabricate AA7075/MoS₂ metal matrix composites (MMCs) with varying weight percentages of MoS₂. Comparative studies were conducted to evaluate how different MoS₂ concentrations affect the morphological, mechanical (including hardness, tensile, compression, and impact strength), tribological (coefficient of friction (CoF) and specific wear rate (SWR)) properties. The incorporation of MoS₂ nanoparticles significantly improved the morphology of the AA7075 alloy, reducing dendrite arm spacing and enhancing the formation of rosette-like dendrites. These morphological changes contributed to the improved mechanical and tribological properties of the AA7075/MoS₂ MMCs. The research found that an optimal concentration of 1.0 wt% MoS₂ nanoparticles resulted in the highest hardness (162.4 HV), superior tensile (357 N/mm²) and compression (404 N/mm²) strengths, and enhanced impact energy (2.3 J). The CoF decreased from 0.318 to 0.302, and the SWR decreased from 0.2206 mm³/KN-m to 0.1903 mm³/KN-m in the AA7075/1.0 wt% MoS₂ MMCs. Primarily, MoS₂ acts as a solid lubricant and promotes the formation of a protective tribo-oxide film during sliding. It also helps to reduce delamination and adhesive wear in AA7075/MoS₂ MMCs compared to as-cast AA7075.