Microstructure and mechanical properties of hypo/hyper-eutectic Al–Si alloys synthesized using a near-net shape forming technique

Abstract

In the present study, three aluminum–silicon alloys containing 7, 10 and 19 wt % silicon were synthesized using a novel technique commonly known as disintegrated melt deposition technique. The results following processing revealed that a yield of at least 80% can be achieved after defacing the shrinkage cavity from the as-processed ingots. Microstructural characterization studies conducted on the as-processed samples revealed an increase in the volume fraction of porosity with an increase in silicon content. Porosity levels of 1.07, 1.51 and 2.65% attained in the case of Al–7Si, Al–10Si, and Al–19Si alloys indicates the near-net shape forming capability of the disintegrated melt deposition technique. The results of aging studies conducted on the aluminum–silicon alloys revealed similar aging kinetics irrespective of different silicon content. Results of ambient temperature mechanical tests demonstrate an increase in matrix microhardness and 0.2% yield stress and decrease in ductility with an increase in silicon content in aluminum. Furthermore, the results of an attempt to investigate the effect of extrusion on Al–19Si alloy revealed that the extrusion process significantly assists in reducing porosity and improving microstructural uniformity, 0.2% yield strength, ultimate tensile strength and ductility when compared to the as-processed Al–19Si alloy. The results of microstructural characterization and mechanical properties of aluminum–silicon alloys were finally correlated with the amount of silicon in aluminum and secondary processing technique.