Optimization and characterization of hybrid aluminum metal matrix composites for enhanced tribological properties

Abstract

The present research investigated the preparation and characterization of a hybrid aluminum metal matrix composite (MMC) consisting of 92 wt.% AA6061 matrix, reinforced with 6 wt.% zirconium dioxide (ZrO2) and 2 wt.% graphite (C). The research study focused on optimizing the mechanical, tribological properties of the hybrid MMC through methodical experimentation and analysis. The hybrid MMC specimens were fabricated using the stir casting method and were subjected to mechanical, microstructural and tribological characterizations as per ASTM standards. A total of 13 specimens were prepared for mechanical and microstructural evaluations, while tribological properties were assessed through 17 experiments designed using the Box-Behnken method under Response Surface Methodology (RSM). Mechanical characterization of the 13 hybrid MMC specimens revealed that the hybrid composite specimen 12 achieved enhanced tensile strength (175 MPa) and hardness (49 HRC) with the composition of 92 wt.% AA6061, 6 wt.% ZrO2, and 2 wt.% of Graphite. These improvements were attributed to the effective distribution of ZrO2 and graphite particles, which improved interfacial bonding and load transfer within the matrix. newlineMicrostructural analysis was performed using optical and scanning electron microscopy (SEM) which confirmed uniform dispersion of reinforcements in well-performing specimens. The analysis also highlighted the detrimental effects of agglomeration in specimens exhibiting lower mechanical performance. Fractographical analysis of the tensile tested specimens further revealed a mixed-mode fracture behavior, where the optimal composite (specimen 12) demonstrated a balance between ductile and brittle properties. newline newline newline