The role of silicon in carbon partitioning processes in martensite/austenite microstructures

- Carbon redistribution in complex microstructures consisting of martensite, carbides and austenite is unveiled.
- Silicon inhibits austenite decomposition during processing by promoting carbon partitioning from martensite into austenite.
- Austenite stabilisation may also occur by transformation strains induced during martensite formation.

Understanding carbon redistribution in steels is crucial in developing advanced high strength steels. For instance, Quenching & Partitioning (Q&P) processes rely on the partitioning of carbon from martensite into austenite, where at the end of the heat treatment the carbon-enriched austenite shows higher stability at room temperature. Recent literature gives increasing evidence of carbide precipitation occurring during partitioning despite the addition of silicon, conventionally thought to suppress carbide precipitation. The aim of the present study is to gain insight into carbon-competing processes by applying a series of Q&P heat treatments, with particular focus on the partitioning stage, where the role of silicon in the stability of austenite is evaluated. Various characterisation techniques are combined in order to unveil the microstructural changes. While carbide precipitation does appear to occur in the presence of silicon, it is found that silicon plays an active role in the stabilisation of the austenite during the partitioning reaction.

Graphical Abstract216