Martensite formation and tempering
The martensitic phase transformation is of vital importance as a high-strength constituent in numerous steels such as powder metallurgy steels, low alloyed steels and stainless steels. Hence, a profound understanding of martensite helps in the development of high-performance steels. The current focus of the project can be grouped in four main areas: i) developing a model for the prediction of martensite formation and how it is affected by e.g. alloy composition, temperature, cooling rate and deformation in low alloy steels, ii) structure-mechanical prioperty relation in alloyed steels, iii) studies of the deformation-induced martensitic transformation (DIMT) in metastable austenitic stainless steels and establishing a relation between the governing factors of DIMT and the microstructure including texture etc., iv) modeling of precipitation of carbides during tempering of martensite.
Significant efforts have previously been devoted to the characterization of the change of martensite structure with the carbon content in low alloyed steels, and this work is continued, now focusing on other alloying elements. Moreover, a 3D elastoplastic phase-field model was successfully developed to simulate the martensitic microstructure evolution in steels. The model is based on the phase field microelasticity model proposed by Khachaturyan. The model has been applied on both single crystalline and polycrystalline steels. The model is currently used for simulations of the martensitic transformation and further development of the model will be initiated.
Figure: Light optical image of plate martensite in Fe-C
Figure: Martensitic microstructure formation from a 3D phase-field simulation of martensitic transformation in a pure elastic material of Fe-0-3%C steel