The Microstructure Evolution Of 2195 Al-Li Alloy In Multi-pass Hot Deformation And Related Annealing

The multi-pass hot deformation of 2195 Al-Li alloy was investigated,Air annealing sand bath annealing and vacuum annealing of 2195 hot rolling plates were studied.The microstructure and mechanical properties of multi-pass deformation and different annealing treatment were observed via Optical microscopy(OM),Scanning electron microscopy(SEM),Electron back scattering diffraction(EBSD),Transmission electron microscopy(TEM),X-ray diffraction(XRD),Inductively coupling plasma-atomic emission spectrometry(ICP-AES).The main conclusions of this research are listed as follows:(1)The true stress-true strain of multi-pass hot deformation is lower than single pass due to the effect of static softening.The static softening ratio increases with the increase of deformation temperature and passes.(2)The microstructure f single pass hot deformation are elongated grains,grain crushing was observed at 400 °C,The dynamically recrystallized grain size increases with increasing deformation temperature and reduces with increasing strain rate.Low angle grain increased with 10% deformation after the first pass of the hot deformation,dynamic recovery occurs in the microstructure.Grain crushing was observed with 40%defromation after the second pass,dynamic recovery and dynamic recrystallization occur as the temperature rises.The key features of the third pass are similar to the single hot deformation,but with more softening for the stay times between each pass.The recrystallization mechanism of the second pass and third pass is grain crushing,grain boundary migration,sub-grain coarsening and grain boundary bow out at low temperature and sub-grain rotated-induced nucleation at high temperature.(3)Long and straight second phase was observed after homogenization treatment,at the time of deformation reached 40%,second phase distorted.With the deformation degree and temperature increases the second phase morphology transited form needle-like to particles.(4)The microstructure of the hot rolled plates,air annealing,sand bath annealing and vacuum annealing were fiber tissue with ? fiber,R texture,recrystallization and course second particles.The mechanism of recrystallization for the alloy is grain boundary bow out.The course second particles are the mixture of TB and ?'.The second particles of sand bath annealing are the most and uniform distributed in the grain,others along the rolling direction.