Properties of self-lubricating silicon carbide particle reinforced aluminium-silicon magnesium alloy hybrid composites

Abstract

A stir casting process was used to fabricate aluminum – 7% silicon – 0.4% magnesium alloy (LM25) composites reinforced with various volume fractions of silicon carbide (SiC) and graphite (G) particulates. Both optical and scanning electron microscopy were used to study the microstructural characterization of the materials. Hardness, tensile and wear properties of the unreinforced LM25 alloy and three hybrid composites were examined. It was observed that the addition of both SiC and G reinforcing particles to LM25 alloys caused a general increase in the properties, although the properties of the composites were predictably affected mostly by the hard reinforcing SiC particles. The hardness, tensile strength and resistance to wear were found to be the maximum in case of HC2 (LM25-5SiC-0G) composite. Addition of G particles somewhat lowered the tensile properties, while a mixed result was obtained in case of hardness. The wear resistance was decreased due to the addition of G particles. The HC1 (LM25-2.5SiC-5G) hybrid composites had the intermediate properties of the two composites HC2 and HC3 where SiC and G particles were used in isolation. The age hardening response of all four materials was predictable. Hardness values were generally increased in case of all materials.