Bainite transformation affected by predeformation and stress in G55SiMoV steel

The influence of predeformation and stress on the isothermal bainite transformation has been investigated in G55SiMoV steel via microstructure observation and kinetic analysis. It was found that the bainite transformation became faster and at the end of isothermal holding the bainite fraction increased under the applied stress condition. When the stress increased to 150 MPa, the bainite distribution became to be nonrandom in G55SiMoV steel. Different deformation conditions, in which both promotion and inhibition occurred in the same steel, were created. The promoting and inhibiting factors affected bainite transformation comprehensively. 20% deformation could promote the bainite transformation when it deformed at 900 °C, but prevent bainite transformation when it deformed at 750 °C. Increase of ferrite nucleation rate caused by distortion and dislocation, would suppress the growth of bainite carbides and make most carbides without full growth be finer and shorter.