High Temperature Deformation and Microstructure Evolution Behaviours of 7075 Cast Aluminum Alloy under Multi-pass Loading

Abstract

To analyse the effects of loading pass and heating temperature on the deformation behaviour and microstructure evolution of 7075 cast aluminium alloy, multi-pass high temperature loading experiments on Gleeble-3500 thermal simulation compressor were carried out. The results indicated that under each loading, all the true stress-strain curves are typical dynamic recrystallization curves. As strain increases, the stress increases sharply and then basically remains unchanged when it reaches a maximum value. As temperature rise, the peak value of flow stress slightly decreases when the temperature is less than 350°C, whereas it increases slightly when the temperature is larger than 350°C. The grain was elongated perpendicular to the axis. Only a small amount of fine recrystallized grains were found to nucleate and grow at grain boundaries at a lower temperature (250°C). As temperature increased, the recrystallized grain gradually increases, and its proportion gradually also increases until the recrystallization is basically completed. The achievements can provide a guideline to select processing parameters for the processes of metal forming of 7075 cast aluminium alloy, such as ingot blooming, spinning and extrusion.