Development and characterization of the mechanical properties of Al6063 alloy composites reinforced with fly ash and E-glass fiber

Aluminum matrix composites reinforced with industrial waste can combine good mechanical performance with sustainability. Al6063 alloy was reinforced with fly ash from Ethiopia's first waste-to-energy plant and with chopped E-glass fiber by sand-mold stir casting (680-700 °C, 450 rpm, 3 × 5 min, 1% Mg), followed by T6 heat treatment. A 3 × 3 factorial design of 2, 5 and 7 vol% E-glass fiber and 3, 6 and 9 vol% fly ash plus an unreinforced control (ten castings) was used so that the separate and combined effects of the two reinforcements could be identified. Hardness, compressive strength, and flexural strength were measured, and the microstructure was examined by optical microscopy. The composite with 7 vol% E-glass fiber and 6 vol% fly ash gave the highest hardness reading (116.73 against 44.26 for the control) and the highest compressive strength (850.31 MPa, +198.7%), and the composite with 5 vol% E-glass fiber and 9 vol% fly ash gave the highest flexural strength (340.1 MPa, +68.9%). A two-way analysis of variance of the factorial data showed that the E-glass fiber content explained about 85% of the variance of hardness and compressive strength, whereas the effect of fly ash was not significant within the range tested. At 7 vol% E-glass fiber and 9 vol% fly ash, the properties decreased, which is attributed to agglomeration and weak interfaces. The combination of two waste-derived, low-cost reinforcements can considerably improve Al6063, and the reinforcement content has to be optimized.