Research on accelerating artificial aging process of Al-5Mg-3Zn-1Cu cast alloy by natural aging

Abstract

In this study, natural aging (NA) has been carried out to accelerate the artificial aging process and enhance the mechanical properties of Al-5Mg-3Zn-1Cu Cast Alloys. The studies show that, during the first 120 h of natural aging, the supersaturated Al-5Mg-3Zn-1Cu cast alloy after the solution heat treatment is unstable, and an amount of nano solute clusters are precipitated from the matrix, which leads to the rapid increase of the hardness of the alloy. Moreover, introducing 120 h natural aging before artificial aging significantly shortens the peaked-aged time and improves the mechanical properties of peak-aged alloys, especially at 150 and 175 ℃ artificial aging temperatures. It is considered that the solute clusters precipitating in the matrix during natural aging and the precipitates formed during artificial aging co-develop to accelerate the artificial aging process of the alloy. In addition, the increase in the number of precipitates reduces the inter-precipitate spacing, which is inversely proportional to the strength of the alloy, resulting in a significant increase in the strength of the alloy. This research suggests that a combination of natural and artificial aging is an effective and economical method for achieving optimized mechanical properties for the Al-5Mg-3Zn-1Cu cast alloy.