Recycling powder by-products to achieve low-cost and high-strength press-and-sinter 6061 aluminium alloys

Abstract

To achieve efficient recycling of by-product powders from gas atomisation, we used fine and recycled powder by-products as raw materials to fabricate 6061 aluminium alloys through conventional press-and-sinter powder metallurgy, and the effect of powder by-products on sintered density, microstructure evolution, ageing behaviour, and mechanical properties was also investigated. Samples with increasing mass fraction of powder by-products exhibited progressive enhancement of densification and mechanical properties, achieving a sintered density of 99.5% of theoretical in the sample with 100% powder by-products (C100) due to improved liquid-phase formation during sintering, and hybrid powders compositions (25–75% powder by-products) developed distinct bimodal distributions. After heat treatment, the T6 C100 sample has the best mechanical properties, with a hardness of 126.5 HV, a yield strength of 317.3 MPa, a tensile strength of 340.8 MPa, and an elongation of 3.0%. The practical validation of preparing end cap and timing pulley components demonstrated the viability of by-product powders for cost-sensitive applications with moderate surface requirements, enabling the reuse of powder by-products, while gear parts revealed compromised tooth flank integrity. The hybrid powder formulations provided a compromise, delivering acceptable mechanical performance alongside superior surface quality relative to pure powder by-products, facilitating the upcycling of powder by-products.