Microstructure, Mechanical Properties, and Corrosion Behavior of Laser Powder Bed Fused AlSi10Mg Alloy after High-Pressure Torsion

Abstract This study investigates the microstructure, mechanical properties, and corrosion behavior of AlSi10Mg alloy fabricated via laser powder bed fusion (LPBF) and subsequently processed through high-pressure torsion (HPT), a severe plastic deformation (SPD) technique. HPT was conducted at various levels of strain, including quarter, half, one, five, and ten turns, all under a consistent pressure of 6 GPa at room temperature. Mechanical properties were assessed through microhardness and nano-indentation tests. Corrosion behavior was evaluated using open-circuit potential (OCP), potentiodynamic polarization (PP), and electrochemical impedance spectroscopy (EIS) electrochemical tests in a 3.5 wt% NaCl solution with 3.62 mg/L dissolved oxygen and a pH of 7 at 27 °C. Microstructure analysis revealed a progressive refinement of melt pools and cellular structures formed during LPBF as the number of HPT turns increased. This resulted in the elimination of porosity and an increase in the microhardness and nano-hardness of the alloy. Transmission electron microscopy (TEM) observations displayed the presence of uniformly distributed nanometer-sized grains after ten turns. Mechanical properties showed marked improvement, with microhardness increasing by approximately 50% and nano-hardness showing similar enhancement. Corrosion test analysis indicated that the corrosion resistance of the alloy did not show a significant improvement after HPT processing, except after five turns of HPT, where the corrosion resistance was indeed enhanced. This non-monotonic trend is attributed to microstructural inhomogeneity and the redistribution of eutectic Si and Mg 2 Si phases, which impact the formation and stability of protective oxide films. The findings highlight that while HPT effectively refines the microstructure of LPBF-fabricated AlSi10Mg alloy and enhances mechanical properties, its effect on corrosion behavior is more complex and composition-dependent.