Experimental investigation on mechanical properties of AA7068/marble dust/fly ash hybrid composite processed by stir casting technique

Abstract Aluminum alloys have wide applications in serval industrial sectors like aerospace, automobile and manufacturing industries. Aluminum reinforced with industrial wastes manufactured through stir casting technique showed potential industrial applications. These hybrid aluminum metal matrix composites are light in weight compared to their counterparts. However, stir casting process parameters effects the mechanical properties of the stir casted aluminum hybrid composites. Hence, there is a need for research to find the optimal stir casting process parameters. The current work focusses on experimental investigation of stir casting technique to find the effect of the process parameters on the uniform distribution of reinforced marble dust and fly ash particulates and mechanical properties such as the tensile strength and the hardness. The various parameters considered in this work especially stirring speed (300, 350, 400) rpm, stirring time (3, 5, and 7) min, stirring temperature (750 °C, 800 °C, and 850 °C) and percentage of reinforcement (3%, 5% and 7%). The mathematical and statistical approach of Response Surface Method (RSM) is used to optimize the stir casting parameters in addition to study interaction effects of process parameters by using response surface and interaction plots. Fabricated metal matrix composites have been characterized by using a Field Emission Scanning Electron Microscope (FESEM), inorder to examine the particle dispersion in the aluminium matrix. The significance of statistical results was evaluated with the analysis of variance (ANOVA) based on P-values and coefficients of corelation (R2). Results indicate that the best values for tensile strength and hardness is achieved at processing conditions of stirring at 900 °C with stirrer speed of 407.56 rpm and the stirring time 7.46 min. The 8.11% reinforcement has the highest tensile strength and hardness values of 347.84 MPa and 153.70 Hv, respectively, with composite desirability of 0.96.