Characterization of heat treatment-driven microstructural evolution, mechanical properties, and electrochemical behavior of direct powder forged Al–10Si–0.3Mg alloy

This study investigated the effects of direct aging (DA), solution treatment (ST), and ST followed by DA (T6) on the microstructural, mechanical, and corrosion properties of direct powder forged Al–10Si–0.3Mg alloy specimens. Microstructural analyses conducted using optical microscopy, scanning electron microscopy, and electron backscatter diffraction revealed that among DA specimens, direct aging at 200°C (DA-2) exhibited significantly enhanced silicon (Si) particle distribution uniformity and minimal interparticle boundaries owing to increased diffusion bonding; ST specimens exhibited partial Si dissolution, higher porosity, and retained the interparticle boundaries; and T6 specimens exhibited improved microstructural uniformity and enhanced Si precipitation. Furthermore, mechanical property evaluations indicated that T6 treatment comprising ST at 500°C for 180 min followed by DA at 200°C for 360 min resulted in the highest tensile strength (207.15 MPa) and elongation (5.02%), followed closely by DA at 200°C for 360 min (203.13 MPa and 4.39%). These improvements were attributed to the lower residual stress, higher diffusion distances, and well-dispersed Si particles induced by DA-2 treatment. Corrosion analyses conducted using cyclic polarization and impedance spectroscopy indicated varied electrochemical responses, with DA-2 resulting in the lowest corrosion current and highest impedance, and ST resulting in the lowest corrosion resistance. Overall, DA at 200°C for 360 min was the most effective heat treatment, offering the optimal balance between mechanical and corrosion-resistance properties.