Evaluation of mechanical and wear properties of LM24/fly ash/titanium diboride hybrid metal matrix composites using stir casting

This study focuses on the development of novel hybrid composites based on the LM24 alloy, utilizing liquid metallurgy stir casting to incorporate dual reinforcements (titanium diboride (TiB2) and fly ash (FA)). The weight percentage of TiB2 was maintained at levels of 2.5%, 5%, and 7.5%, keeping the FA at 2.5% during the course of fabrication. The introduction of 7.5 wt% TiB2 and 2.5 wt% FA displayed a very notable 43.18% increase in hardness and a 21.53% increase in tensile strength of the hybrid composite compared to the LM24 alloy. Furthermore, hybrid composites with a total reinforcement of 10 wt% exhibited superior wear resistance across the entire range of applied loads. Tensile fractography revealed ductile fracture mode for the LM24 alloy, while hybrid composites displayed a mixed-mode fracture. High-load-induced abrasive wear with little plastic deformation was seen on worn surfaces of hybrid composites, whereas adhesive wear was the dominant type of wear in the LM24 alloy. The results show that hybrid composites have better mechanical and tribological properties because the reinforcement particles are well distributed and the load is transmitted optimally. However, it is noted that increased reinforcement levels lead to a reduction in ductility, resulting in decreased impact resistance for the hybrid composites.