Abstract: The present research work reports the fabrication and evaluation of the mechanical properties of hybrid aluminium matrix composites (HAMC). Aluminium 7075 (Al7075) alloy was reinforced with particles of boron carbide (B4C), silicon carbide (SiC) and coconut shell fly ash (CSFA). Al7075 matrix composites were fabricated by stir casting method. The samples of Al7075 HAMC were fabricated with different weight percentages and in different compositions B4C, SiC and CSFA. The mechanical properties discussed in this work are hardness, tensile strength, and impact strength. Hardness of the composites increased 33% by reinforcements of 6wt.% B4C, 6wt% SiC and 3wt.% CSFA in aluminium 7075 alloy. The tensile strength of the composites increased 66% by the addition of 9wt.% B4C and 3wt.% CSFA in aluminium 7075 alloy. Further addition of reinforcements decreased the tensile strength of the composites. Elongation of the composites decreased while increasing B4C and CSFA reinforcements in the matrix. The impact energy of the composites increased up to 2.3 J with 9wt.% B4C and 3wt.% CSFA addition in aluminium alloy. Further addition of reinforcement decreased the impact strength of the composites. The optical micrographs disclosed the homogeneous distribution of reinforcement particles (B4C and CSFA) in Al7075 matrix. The homogeneously distributed B4C and CSFA particles added as reinforcement in the Al7075 alloy contributed to the improvement of hardness, tensile strength, and impact strength of the composites.
Key words: Aluminium 7075; boron carbide; silicon carbide; fly ash; casting; hardness; tensile strength; impact energy
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