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Thixoforming is the process of shaping near net shape metal components in a semisolid state. The process consists of preparing feedstock, reheating and shaping. Reheating the billet is the most critical step in thixoforming. Induction heating requires precise temperature control to obtain globular microstructure and prevent process defects, such as insufficient heating, overheating, and electromagnetic end effect and elephant foot phenomena. Moreover, inductive heating parameters are investigated to improve the quality of thixoforming. This study investigates applied coil current and optimal coil geometry and design (i.e. height, diameter and coil turn) in high-frequency induction heating numerically and experimentally. Simulation results combined with an approximation approach method are verified via a reheating experiment. The proposed method validated via an experiment can be a practical tool for predicting temperature distribution and reheating time required for thixoforming.

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The recent advancement in graphene-reinforced aluminium matrix composites improves wear behaviour in the production of lightweight and high-performance nanocomposites. Considerable works have been devoted to using graphene nanoparticles as solid self-lubricants to increase wear resistance, minimise friction coefficients, improve service efficiency, and extend the lifespan of related sliding components. In general, wear behaviour often depends on the homogeneous distribution of graphene in the aluminium matrix. The non-uniform distribution of reinforcement due to the tendency of graphene to agglomerate in aluminium matrix and its poor wettability becomes a challenge in developing optimum functional of composites. The wettability of graphene can be enhanced by proper processing methods and sufficient addition of magnesium that can improve the wear and frictional properties of the produced composites. Hence, this review article provides recent findings and the influence of graphene as reinforcement materials in composites, including the effects on wear behaviour and friction properties. This article also discusses new advancements in the effect of graphene in self-lubricating aluminium matrix composites and the impact of reinforcement on the wear mechanisms of the composites. The future direction of the wear properties of MMCs is also covered at the end of the review.

Forming of metals in their semi-solid state is one of the options for producing near net shape parts. It can produce a strong and highly reliable product. Al-Si-Cu-Mg casting alloy is commonly used in automotive engine components which is now widely used in the semi-solid processing. The main physical properties of the aluminium alloy and alloying element content such as silicon, copper and magnesium, plays an important role in determining the mechanical properties of the alloy. In this paper, the effect of the formation process of Al-Si-Cu-Mg permanent die casting alloy and the thixoforming process has been investigated towards the evolution of microstructure and mechanical properties. Compound phases, shapes and morphology of the two processes were compared. The porosity effect was examined at permanent die castings and thixoforming process. The result of image analysis showed significant change of the thixoforming process of α-aluminum solid phase structure in spherical shape. Size and morphology, as well as the uniformity of the silicon eutectic phases and intermetallic compound distributions of Al2Cu, Al5Fe Si and Al15(Mn,Fe)3Si2 changed due to the compression during thixoforming process. Thixoforming process of the Al-Si-Cu-Mg alloy exhibit the lowest percentage and microporosity area thus proved that porosity issue significantly reduced during the aluminium alloy solidification process in thixoforming process . The tensile properties of thixoformed alloy improved significantly with its ultimate tensile strength, yield strength, and elongation to fracture at 193MPa, 163MPa and 1.6%,respectively.

The effect of Mg addition (0.5–2.0%) on the as-cast and thixoformed microstructures, hardness and the tribological properties of A319 aluminium alloy was investigated. The investigations highlight the dry sliding wear test behaviour using a pin-on-disk tester configuration under the applied pressures of three loads of 10, 50 and 100 N at a constant sliding speed of 1 m/s and a sliding distance of 9 km. Detailed microstructural morphology studied for these alloys is correlated with the wear properties obtained. Results in the as-cast A319 alloy revealed that Mg addition transformed the Al2Cu phase and Si particle to form the Al5Cu2Mg3Si5 and Mg2Si intermetallic phases during the solidification. Moreover, the platelet-like morphology of β-Al5FeSi intermetallic completely converted to Chinese script-like morphology, π-Al8Mg3FeSi6 phase with the addition of Mg up to 1.5 wt.%. By adding Mg and performing thixoforming, the microstructure of the α-Al phase shows a fine globular primary phase surrounded by uniformly distributed Si and refined fragmented of intermetallic phases formed. The morphology of Mg2Si particles was modified from large, polygonal particles into relatively smaller and more globular, whereas the Chinese script-like morphology π-Al8Mg3FeSi6 changes to a compact shape. Adding Mg up to 2 wt.% increased the hardness at 100 Hv. The increase in Mg content enhances the wear resistance, friction coefficient and volume loss of thixoformed A319 alloy. A combination of abrasion and adhesion for alloys of low Mg dominates the wear mechanism. In contrast, excessive subsurface fracturing and delamination with minor abrasion are mainly observed for alloys of high Mg.