Microstructure and tensile properties of Al-Mn-Mg-Sc-Zr alloy processed by friction rolling additive manufacturing

Abstract

Solid-state additive manufacturing (SSAM) has garnered more attentions in recent years. Due to the non-equilibrium solidification during powder preparation, supersaturated alloy powders as deposition material for SSAM would obtain superior mechanical properties to the rods and plates. In this study, gas-atomized AlMnMgScZr powder was used to produce bulk samples by friction rolling additive manufacturing (FRAM), and the densification behavior, microstructural evolution, and tensile properties of fabricated samples with different additive layer thicknesses ranging from 0.2 mm to 0.5 mm have been investigated. The results showed that the degree of powder bonding is improved, while the second phases formed in the FRAMed alloys become coarser by reducing the additive layer thickness. The FRAM process induces the dissolution of primary second-phase particles existing in the initial powder, meanwhile leading to the dynamic precipitation of Al₆Mn and Al₃Sc phases. The prior precipitation of Al₃Sc particles plays a crucial role in inhibiting the coarsening of the Al₆Mn phase. Tensile tests indicated that the additive layer thickness obviously influenced the strength and ductility of fabricated alloys due to the change in bonding quality and the evolution of the second phases. Both yield strength and ultimate tensile strength are decreased, while the elongation is initially increased and then decreased with decreasing additive layer thickness. The sample with the additive layer thickness of 0.3 mm exhibits a good combination of strength and ductility, in which the yield strength and elongation are 422 MPa and 18%, respectively.