Effect of deformation of austenite and cooling rates on transformation microstructures in a Mn–Cr gear steel

The effect of austenite deformation and cooling rates on continuous cooling transformation microstructures for a Mn–Cr gear steel were investigated using a Gleeble 1500 thermomechanical test system. The experimental results show that the deformation of austenite promotes the formation of proeutectoid ferrite and pearlite, leading to the increase of critical cooling rate of proeutectoid ferrite plus pearlite microstructure. The deformation enhances the stability of austenite against bainite transformation, which results in an increase in amount of martensite/austenite (M/A) constituent with deformation at some cooling rates studied. Moreover, cooling rate also affects amount of M/A constituent. With decrease of cooling rate, amount of M/A constituent increases at first, but decreases subsequently till disappears eventually.