Investigations on microstructure, hardness and tribological behaviour of AA7075-Al2O3 composites synthesized via stir casting route

Abstract

Aluminium matrix composite (AMC) materials play an important role in the field of automobile and aerospace industries due to their excellent properties. In this research, aluminium alloy (AA7075) was reinforced with alumina (Al2O3) particles to improve their hardness and tribological behaviour of the base alloy. Four composites were prepared by varying the content (4, 8 and 12 wt.%) of Al2O3 particles through the stir casting technique. The surface morphology of the proposed composites ensured the uniform distribution of Al2O3 particles into the matrix alloy. The hardness of the composite was measured using a Brinell hardness tester and the maximum value of hardness was found in the AA7075 - 8 wt.% Al2O3 composite. Hence, a tribological investigation was carried out on this AA7075 - 8 wt.% Al2O3 composite. Load (P), sliding speed (V) and sliding velocity (D) were taken as the wear parameters for conducting the experiments. A Technique for Order Preference by Similarity to Ideal Preferred Solution (TOPSIS) approach has been applied to find out the optimal conditions of parameters to obtain the lowest wear rate (WR) and the co-efficient of friction (COF). The results showed that the lowest WR and COF was obtained at ‘P’ of 15 N, ‘V’ of 1 m•s-1 and ‘D’ of 1000 m•s-1. ANOVA results revealed that ‘P’ is the factor with the most significant contribution (38.36%), followed by ‘D’ (28.32%). The worn surface morphology of the confirmation experiment specimen was investigated by SEM and the wear mechanism was reported.

Keywords

• AA7075
• Al2O3
• Composites
• Hardness
• Stir casting
• TOPSIS approach