Investigation of the Effect of Copper on Microstructural Modification and ‎Quality Index of Al-15Mg2Si Composite

In-situ Al-15Mg2Si composite due to their low density and good strength and wear properties are considered as potential candidates to substitute the Al and cast iron parts used in automotive and aerospace industries. The improved properties of these composites are governed by controlling the size and morphology (modification) of the primary Mg2Si particles. In the current study the effect of Cu addition (1.0, 3.0, and 5.0 wt. %) on metallurgical structure and quality index of Al-15Mg2Si composite was investigated. According to the results, Cu addition modified the morphology and reduced the average size of primary Mg2Si particles. The addition of Cu up to 3.0 wt. % improved the composite tensile strength by up to 34% whilst its further addition impaired the tensile properties. Moreover, the addition of Cu up to 1.0 wt. % improved the composite elongation by about 7%. This is while its further addition deteriorated the composite ductility. The maximum quality index was observed in 3.0 wt. % Cu containing composite where its quality index was 8% higher than that of the base sample. The microstructural observations, micro-hardness testing, precipitates chemical analysis, and fractography of fractured surfaces revealed that solid-solution-strengthening, dispersion hardening of Cu-containing precipitates, and modification of Mg2Si particles are the main factors improving the composite quality. Moreover, increasing the volume fraction of hard Cu-precipitates and micro-pores, negatively affected the composite tensile properties and quality index.