Influence of Intercritical Annealing Temperature on Microstructure and Mechanical Properties of TRIP780

The influence of intercritical annealing temperature on microstructures and mechanical properties of 0.16C-1.47Si-1.64Mn-0.02Nb-0.02Ti cold rolling TRIP(transformation induced plasticity)steel sheets was investigated by using optical microscopy and X-ray diffraction measurements.The results show that the maximal volume fraction of retained austenite,which is 8.4%(The volume fraction of ferrite and bainite is 53.0% and 38.6%,respectively),can be obtained by heat treatment in anealing at 840 ℃ for 180 s and isothermal heat treat at 420 ℃for 240 s.The best strength and ductility product,which is 22.4×103 MPa%,is also obtained by this heat treatment process.The amount of retained austenite will bereduced at the higher or lower temperature in heat treatment process.