Effect of deformation and grain size on austenite decomposition during quenching and partitioning of (high) silicon-aluminum steels

The effect of austenite deformation on carbon partitioning and transformation to athermal and isothermal martensite, and bainite during quenching and partitioning (QP) is described for three steel compositions: Fe0.3C-0.6Si-1.1Al, Fe-0.3C-1.0Si and Fe-0.3C-0.5Si-0.5Al. Microstructures were characterized using SEM-EBSD, TEM and XRD. Austenite decomposition kinetics was investigated using dilatometry. Deformation close to the no-recrystallization temperature refines the grain size, lowers the martensite start temperature and affects the stability of austenite during QP processing. The results in respect of dilatation measurements and retained austenite contents at room temperature corroborate the QP microstructures and their hardness and can help in designing optimal QP treatments for these novel steels.

Automated summary

The study describes the effect of austenite deformation on carbon partitioning and transformation to athermal and isothermal martensite, and bainite during quenching and partitioning (QP). It was found that deformation close to the no-recrystallization temperature refines the grain size, lowers the martensite start temperature and affects the stability of austenite during QP processing. These results can help in designing optimal QP treatments for these novel steels by corroborating the QP microstructures and their hardness through dilatation measurements and retained austenite contents at room temperature.