Influence of Solution Treatment on Microstructure and Quench Cracking in a Water-Quenched Aluminium Alloy 7150

In this work, the influence of multi-step solution (MSS) treatments on the constituent particle dissolution, overheating and associated quench cracking behaviour in room temperature water-quenched 7150 Al alloy has been investigated. For comparison, the microstructure and quench cracking behaviour of single step solution treated samples water-quenched from 505°C were also investigated. Based on optical microscopy of differently quenched samples, the quench cracking mode and the influence of overheating of constituents on the quench cracking behaviour have been demonstrated. The results reveal that the constituent particles can be effectively dissolved in the MSS-505°C samples. When the quench temperature of MSS-505°C samples is equal to or higher than 485°C , macro quench cracks can be clearly observed. Moreover, the density and length of the quench cracks increase with increasing quench temperature. Etched microstructures indicate that the quench crack propagation mode is intergranular. However, for samples directly heated to 505°C , typical overheating can be observed at the triple junctions and these regions preferentially act as crack propagation routes.