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

摘要

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 fer-rite and pearlite, leading to the increase of critical cooling rate of proeutectoid ferrite plus pearlite micro-structure. 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.