Martensite and nanobainite transformations in a low alloyed steel studied by in situ high energy synchrotron diffraction

Martensitic and nanobainite transformations are studied in situ a low alloyed, high-Si steel by using HEXRD, combined with dilatometry SEM observations, considering the same composition austenitization conditions. The martensitic microstructure presents mixed lath-plate morphology large scatter of sizes whereas bainite shows finer laths more uniform sizes. Recently introduced methods used to track one single experiment, phase fractions, distribution carbon evolution dislocation densities. study revealed that about two thirds partitions from ferrite precipitate into transition iron carbides or enrich austenite. Both processes occur very fast after formation each lath, but remains largely supersaturated carbon. density increases inside new forming bainitic lath. It then decreases when recovery becomes preponderant, as described model literature. After transformation, retained austenite ends up high hydrostatic compressive stresses. Dislocation densities higher than probably heterogeneous, because is less significant. No were detected, contrary nanobainite. mass balance analyzed light these results previous investigations on similar systems.