Effect of Solution Temperature on the Microstructure and Properties of AlSi37Cu0.7Mg0.9Ni0.2 Alloy Prepared by Rapid Solidification and Hot Extrusion

This study systematically investigated the effects of solution temperature (460-560 °C) on the microstructure, mechanical properties, and corrosion behavior of AlSi37Cu0.7Mg0.9Ni0.2 alloy rods prepared by rapid solidification and hot-extrusion. The results demonstrated that the solution temperature critically governed the alloy's recrystallization behavior, precipitation kinetics, and phase distribution. With the increase in solution temperature, the alloy exhibited progressive grain coarsening (from 4.51 μm at 460 °C to 13.25 μm at 560 °C) and enhanced precipitation hardening, leading to a 108.8% increase in hardness (198.4 HV at 560 °C) but a concurrent reduction in ductility (from 2.5% to 1.0%). Electrical conductivity initially improved by 3.4% at 460 °C (27.44% IACS) compared with the extruded state, but deteriorated at higher temperatures due to increased electron scattering. Anodic oxidation tests revealed a non-monotonic corrosion trend, with maximum weight loss (57.50 mg·g^-1) occurring at 480 °C due to microstructural inhomogeneity, while higher temperatures (560 °C) partially restored corrosion resistance. Electrochemical analysis corroborated these findings, showing the 480-treated sample exhibited the lowest corrosion potential (-1.0159 V). Microstructural characterization confirmed that optimal mechanical properties were achieved through a combination of fine <i>β</i>″-Mg₂Si (<20 nm), <i>θ</i>'-Al₂Cu precipitates, and thermally stable Al₃Ni phase. These results established a comprehensive process-structure-property relationship, which provided critical guidance for tailoring the alloy's performance in structural-functional applications.