7. Mechanical and Welding Properties of A6082–SiC–ZrO₂ Hybrid Composite Fabricated by Stir and Squeeze Casting

Aluminium metal matrix composites are having lightweight, high strength, good corrosive resistance and toughness. Aluminium A6082 alloy has good mechanical properties and is mainly used in structural applications. The reinforcement particles SiC and ZrO₂ have high strength. In this work, A6082/SiC/ZrO₂ hybrid composites are fabricated with different wt% of reinforcement materials (0.5, 1 and 1.5 wt% ZrO₂ and SiC constant for all composites) by using stir and squeeze casting process. A6082 alloy and A6082/SiC/ZrO₂ hybrid composites are prepared for mechanical and welding properties like hardness, impact, compression, welded tensile test and welded hardness test. SEM microstructures of A6082/SiC/ZrO₂ hybrid composites have shown uniform distribution of ceramic particles. The hardness is increased for A6082 alloy and hybrid composite with increasing reinforcement up to 1 wt% ZrO₂. Hybrid composite reinforced with 1 wt% ZrO₂ is 18.6% more than the base alloy. The compression strength is increased in A6082 alloy reinforced with 1 wt% SiC and 1 wt% ZrO₂, which is 20% more than the A6082 base alloy. The Charpy impact strength of the composite materials is increased with the addition of 1 wt% ZrO₂, which is 60% compared to base alloy. “As-cast” A6082 aluminium and composites are joined by friction stir welding process with similar materials. Tensile test and hardness are performed on welded plates. The ultimate tensile strength is increased up to 33% at 0.5 wt% ZrO₂ compared to welded base alloy. The UTS of 1 and 1.5 wt% ZrO₂ decreased and showed brittle failure. The SEM fractography of welded tensile fracture surface showed more dimples in 1 wt% SiC and 0.5 wt% of ZrO₂ reinforced composite, and less dimples and more cleavages are shown in higher wt% ZrO₂. The hardness strength is increased to welded composites of 1 wt% SiC and 1 wt% ZrO₂, and the hardness is increased up to 17% compared to base alloy.