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.
