Evaluation of Tensile and Fatigue Behaviours of Novel A356/Melon Husk Ash Nanocomposite

Abstract

Lightweight materials such as aluminum matrix composites are gaining prominence in automobile manufacturing due to their competitive properties, with further improvement in properties is achievable by exploiting nanotechnology and developing nanocomposites. The present study explores the tensile and fatigue behaviours of a novel lightweight aluminium-based nanocomposite—A356 reinforced with melon husk ash nanoparticles (MHAnp). Melon husk ash nanoparticles (MHAnp) produced from an abundant Nigerian agro-waste, Egusi melon (Citrullus colocynthis L.) husks, were used to fabricate an A356/MHAnp composite through a modified stir-casting route, i.e., a low-frequency vibration-assisted stir casting. Samples cast were evaluated for tensile and fatigue performance using standard test procedures. X-ray diffraction (XRD) and optical microscopy (OPM) and scanning electron microscopy (SEM) were used to study the microstructure of the fabricated samples and morphology of the fatigue-fractured surfaces, respectively. XRD patterns of the nanocomposite revealed presence of α-Al, Si, β-Al₅FeSi and SiO₂, while optical micrographs of the samples showed a refined microstructure of primary α-Al dendrites, acicular Si and a relatively even distribution of nanoparticles.  Results of tensile tests showed that the nanocomposite exhibited improved properties over the as-cast aluminium alloy. The improvements are by 22.85, 3.09 and 8.00 % for tensile strength, yield strength and ductility, respectively. Compared to the as-cast aluminium alloy sample, the nanocomposite sample exhibited a 3.12% improvement in fatigue strength and 10.60% improvement in fatigue life. Fractography of fatigue-fractured samples using SEM indicated that, despite low-frequency vibration during processing, some nanoparticle agglomeration persisted, contributing to crack initiation. In summary, this study demonstrates that melon husk ash nanoparticles are a viable and effective reinforcement for aluminium matrix composites, offering a sustainable pathway to enhance mechanical and fatigue properties for lightweight automotive applications