Parameter optimization and characterization of environmental friendly aluminium hybrid metal matrix composites

The present experimental investigation was carried out to fabricate environmental friendly hybrid aluminium metal matrix composites with three reinforcements in minimal amount through electromagnetic stir casting: an uncommon fabrication technique. Al 7075-T6 alloy was infused with three reinforcements; eggshell particles (wt% 0.5, 1 and 1.5, particle size ∼60 μm), SiC particles (wt% 1, 1.5 and 2, particle size ∼65 μm) and Al₂O₃ particles (wt% 1.5, 2 and 2.5, particle size ∼90 μm) with variable mechanical stirring time (2, 4 and 6 min). Composite fabrication experiments were run in accordance with Taguchi's orthogonal array L9 and analysis of variance (ANOVA) was conducted to optimize process parameters and to observe their influence on quality characteristics. Developed composites were characterized for various physical and mechanical properties such as density, porosity, residual stress, micro hardness and tensile strength. Investigation outcomes show that synthesized hybrid composite specimen S8 with a total reinforcement content of 4.5% only, demonstrated no significant change in density (only upto 2.2%) whereas the maximum reduction in percentage porosity was 75%. Additionally, maximum abatement in residual stress of hybrid composite specimen S8 was 76% as compared to their unreinforced counterpart specimen S0, there was a maximum enhancement of 83% in microhardness and 107% in tensile strength of fabricated hybrid aluminium metal matrix composite specimen S8 in comparison of as-cast Al 7075-T6 specimen S0. Disposal of eggshells is a serious threat to environment, thus more focus was put on recycling them and using them for development of environmental friendly and cost effective hybrid composites with enhanced properties for numerous engineering applications. (paper)