Microstructure Formation and Carbon Partitioning with Austenite Decomposition during Isothermal Heating Process in Fe-Si-Mn-C Steel Monitored by In Situ Time-of-Flight Neutron Diffraction

Retained austenite is a key feature used to realize the transformation-induced plasticity in bainitic high strength steels. In this study, authors focused on formation of metastable Fe-0.61C-1.9Si-0.98Mn (mass%) during isothermal heating processes using situ neutron diffraction techniques. Quantitative discussion carbon partitioning enabled by applying an phase fraction analysis considering crystallographic textures, addition concentration estimation based lattice parameter austenite. The behavior inhomogeneous, resulting bimodal distribution enriched, stable at 673 K and retained even after cooling room temperature. remainder low austenite, which gradually consumed bainite transformation. Above 723 K, also decomposes ferrite cementite due fast diffusion Si. Conversely, below 623 stabilized without These mechanisms prevent retention inhomogeneous must be carefully considered precisely predict microstructure Si-added