On the non-equilibrium microstructure and mechanical behavior of the fast-heating Q&P steels
Geng Liu, Tsinghua University, Beijing, ChinaHao Chen, Tsinghua University, Beijing, ChinaJun Li, Research Institute of Baoshan Iron and Steel Co. ,Ltd, Shanghai, China
Fast-heating technology was applied to processing a cold-rolled quenching and partitioning (Q&P) steel. The competition between ferrite recrystallization and non-equilibrium austenite formation during fast heating was analyzed, and it was suggested that fast-heating promotes grain refinement, accelerates austenite transformation and yields inhomogeneous distribution of elements, and finally leads to the non-equilibrium and heterogeneous microstructure. It is interestingly found that the heterogeneous retained austenite in the fast-heated Q&P samples leads to a continuous TRIP effect during tensile test, which improves work hardening behavior of the steels. The statistics of the ultimate tensile strength vs. total elongation of each sample under the orthogonal annealing conditions suggested that, compared with conventional Q&P samples, fast-heating could improve the strength with approximately 90 MPa on average within the elongation ranged from 17 to 27%.