Enhanced mechanical properties and homogeneous T5 age-hardening behavior of Al-Si-Cu-Mg casting alloys

In this study, the effects of melt-holding temperatures on the mechanical properties and T5 age-hardening behavior of Al-Si-Cu-Mg alloys were investigated. An enhanced yield strength, tensile strength, and elongation were observed simultaneously as the melt-holding temperature was increased from 720 & DEG;C to 820 & DEG;C. The enhanced mechanical property of the T5-treated Al-Si-Cu-Mg alloy with high melt-holding temperature was attributed to several microstructural changes, including a refinement of the microstructure and an acceleration of the precipitation kinetics caused by enhanced second-phase dissolution. The high meltholding temperature was particularly effective in changing the precipitation kinetics. This was demonstrated by the formation of a single peak upon homogenization of the solute distribution, replacing the double hardness peaks found in the Al-Si-Cu-Mg alloy with a low melt-holding temperature. The homogeneous solute distribution not only increased the number of Si- and & beta;-type precipitates in the alloy with a high melt-holding temperature but also refined their size. In addition, the high melt-holding temperature accelerated the segregation behavior of Cu on the Si precipitates, which is critical for the refinement of precipitates. & COPY; 2023 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http:// creativecommons.org/licenses/by/4.0/).