A thermo-mechanical coupling finite element model was built to investigate the inertia friction welding of GH4169 bars.The remeshing and map solution techniques were adopted.The whole welding process was investigated by adopting an innovative heat generation model and the flywheel rotational speed measured via the experiment. The simulated evolution of axial shortening shows a good agreement with the experiment. In addition,extensive strain concentration presents in the interface and flash,and the largest strain exists near the flash root.Moreover,an interesting thermal reflux phenomenon during the cooling stage was found.