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

摘要

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.