Enhancing and Predicting Microhardness of Al 7075 Hybrid Composites Reinforced with TiC and Graphite Using ANOVA and Regression

Abstract

The mechanical behavior of metal matrix composites (MMCs) is significantly influenced by the type and proportion of reinforcements used. This study investigates the hardness characteristics of Al 7075 hybrid composites reinforced with Titanium Carbide (TiC) and Graphite through a structured factorial design approach. Ten distinct composite formulations were prepared by varying TiC (1, 3, 5 wt.%) and Graphite (1, 3, 5 wt.%) contents, including an unreinforced control sample. The composites were fabricated using the bottom-pouring stir casting technique, ensuring uniform dispersion of reinforcements. Vickers micro hardness testing was conducted to evaluate surface hardness, and the results revealed values ranging from 66 HV to 85 HV. The maximum hardness was recorded for the composite containing 5 wt.% TiC and 5 wt.% Graphite. The experimental design was statistically validated using regression modeling and ANOVA, with a coefficient of determination (R²) of 0.8233 and Adeq Precision of 8.42, indicating a strong predictive model and good signal-to-noise ratio. The results confirmed that both TiC and Graphite significantly enhance hardness through mechanisms such as grain refinement, dislocation generation, and load-bearing reinforcement. The factorial design approach proved effective for analyzing individual and interaction effects, offering an optimized route for developing high-performance hybrid composites.