Surface engineering of wire arc additively manufactured AZ80 magnesium alloy

Abstract

This study investigates the surface engineering of wire arc additively manufactured (WAAM) AZ80 magnesium alloy, focusing on the combined effects of process parameters, heat treatment, and shot peening on its microstructure and mechanical performance. WAAM AZ80 was produced using two processing conditions: one producing materials with higher defect content (P1) and the other yielding a densified, near-defect-free condition (P2). Specimens were extracted along both parallel and perpendicular to the build direction to assess anisotropy, and benchmarked against wrought EN AW-6082 aluminium alloy in the T6 condition. The findings showed that process-induced defects strongly influenced tensile anisotropy, whereas T6 heat treatment improved ductility, hardness, and tensile strength, reducing orientation-dependent disparity and bringing the mechanical properties closer to EN AW-6082. Compression strength exhibited limited sensitivity to defect content. Shot peening further enhanced the surface integrity by inducing grain refinement, work hardening, and CRS, though at the expense of increased roughness. The surface hardness increased by up to 45% in WAAM AZ80 and by 14% in EN AW-6082, while peak CRS reached ~110 MPa in WAAM AZ80 and ~280 MPa in EN AW-6082. Fatigue life improvements were most pronounced in WAAM AZ80, with shot peening extending life by up to 160%, depending on the printing and associated defect orientation, and enabling run-outs beyond 106 cycles in P2 samples through delayed crack initiation and reduced surface-connected porosity. Although EN AW-6082 retained higher absolute fatigue strength, the results demonstrate that refined process control, T6 heat treatment, and shot peening can collectively transform WAAM AZ80 into a competitive lightweight alternative for aerospace and satellite applications, particularly under cyclic loading conditions. Attempts to improve electrical performance through gold coatings highlighted the challenges of plating reactive magnesium alloys. While electroplating failed to achieve uniform coverage, sputtered coating produced more continuous films but did not significantly enhance conductivity, underscoring the need for tailored pretreatments and interlayers for functional integration.