This article provides an intensive review of the past and current research work on the solid-state recycling of light metals. The review includes an experimental aspect of the relevant works that clearly clarify the effects of several critical factors noted as chip preparation, reinforcing phases, die geometry, process parameter selection and performance of miscellaneous methods over the quality of the extruded profiles. Likewise, reviews of numerical and analytical works on the solid-state recycling were presented to understand the strengthening phenomena of chip-based billet through the plastic deformation. Finally, concluding remarks underline challenges of direct recycling method and subsequently highlight the potential future work on making the method as a promising alternative for sustainable manufacturing agenda.

This paper provides an intensive review on past and current research works in solid state recycling of aluminium and its alloys. The review relates the extrudates quality of the solid state recycled aluminium to certain aspects noted as chips preparation, reinforced materials addition, die geometry, processing parameters, and performance of miscellaneous solid state recycling techniques. Finally, concluding remarks underline challenges for aluminium recycling by the solid state and also highlight the potential future work on making the method as a promising alternative for sustainable manufacturing and hence technologically feasible for industrial implementation

In the past few decade, Additive Manufacturing (AM) has become popular and substantial to manufacture direct functional parts in varieties industrial applications even in very challenging like aerospace, medical and manufacturing sectors. Selective Laser Melting (SLM) is one of the most efficient technique in the additive Manufacturing (AM) which able to manufacture metal component directly from Computer Aided Design (CAD) file data. Accuracy, mechanical and physical properties are essentials requirement in order to meet the demand of those engineering components. In this paper, the mechanical properties of SLM manufactured AlSi10Mg samples such as hardness, tensile strength, and impact toughness are investigated and compared to conventionally high pressure die cast A360 alloy. The results exposed that the hardness and the yield strength of AlSi10Mg samples by SLM were increased by 42% and 31% respectively to those of conventionally high pressure die cast A360 alloy even though without comprehensive post processing methods. It is also discovered that AlSi10Mg parts fabricated by SLM achieved the highest density of 99.13% at the best setting parameters from a previous study of 350 watts laser power, 1650 mm/s scanning speed and hatching distance 0.13 mm.

Solid-state recycling is a direct conversion method for producing metal chips, whereas the materials are plastically deformed into the final product without melting, offering lower energy consumption and metal waste. This technique was reported for fabricating aluminium-zirconium oxide (Al-ZrO₂) composite and it was widely used to avoid metal chips bounding at high temperatures during the extrusion process. Aluminium alloy (AA7075) is known for its high yield strength of more than 500 MPa under optimum ageing conditions. However, AA7075 can be further reinforced by zirconium oxide nanoparticles when needed for high-performance applications. Hot extrusion is used to obtain better mechanical properties of composite materials. The equal channel angular pressing (ECAP), a severe plastic deformation technique, was recently used to produce bulk and light recycled metal chips, such as porosity-free and ultra-fine-grained aluminium nanocomposites (ANCs). Heat treatments (HT) and ECAP post hot extrusion are mostly incorporated to improve tribological and mechanical properties and aluminium nanocomposite bonding efficiency. In this review, ANCs’ fabrication by the hot extrusion technique and the effects of ZrO₂ nanoparticle are duly summarised and discussed. Furthermore, this review emphasises the importance of using HT and ECAP techniques to acquire better metal alloy incorporation, such as AA7075-ZrO₂. Interestingly, owing to the lightweight properties and superior performance of AA7075-ZrO₂, it was reported to be suitable for fabricating many drones’ parts, military equipment, and some other promising applications.

Compared to the recycling process by remelting, hot extrusion significantly reduces the energy consumption and CO₂ emission and ensures good mechanical and microstructural properties. This study investigates the effects of reinforcing aluminium AA6061 chips with mixed boron carbide (B₄C) and zirconia (ZrO₂) particles by employing a design of experiment (DOE) under 550 °C processing temperature and three hours preheating time. The findings showed that compressive strength (CS) and hardness increased with up to 5% added particles, and beyond 5%, the yielded values decreased because of materials agglomeration. However, the decreasing density was dependent on the addition of ZrO₂ particles. The distribution of particles with different volume fractions of mixed particles was investigated by employing SEM, AFM, and EDS tests. Thus, the process can produce a net shape structure that utilises material-bonding consolidation to provide sufficient support to reuse the recovered materials in engineering applications, such as in the automotive industry.