The effect of strain and temperature profiles on static recrystallization during solution heat treatment after hot deformation of alloy 718

An investigation into the effect of temperature and strain gradients on recrystallization during solution heat treatment has been performed on Alloy 718 test pieces. High temperature compression experiments were carried out using a Gleeble, which generates strain and temperature gradients within the compression sample. The initial results have shown there is a band in the deformation transition zone where large abnormally coarse grains manifest after solution heat treatment. Detailed analysis by Electron Backscatter Diffraction (EBSD) was carried out to determine grain characteristics as well as δ phase distribution and morphology. Grains produced via this abnormal grain coarsening are characterised by a large percentage of twin boundaries. The grain growth also appears to be immune to the effects of boundary pinning by δ phase particles. The results suggest that stored energy gradients may be the key to this phenomenon.