残留オーステナイト型複合組織鋼の相変態と成分分配挙動

抄録

Transformation behavior and compositional partitioning in TRIP (Transformation induced plasticity) steel was investigated by means of microstructural observation and computer modelling. Orthoequilibrium partitioning of alloying elements of Si and Mn was attained even in short intercritical annealing time. A model based on transformation mechanism controlled by C diffusion well described the volume fractional change of ferrite and pearlite during the cooling to austempering temperature. Slower cooling rate significantly increased C concentration to around 0.5% in untransformed γ and caused pearlite transformation. Bainite volume fraction obtained by austempering increased with austempering temperature. Analysis by computer modelling revealed that transformation kinetics above 350°C followed the model based on diffusion mechanism, while it agreed better with the model based on shear mechanism below 350°C.