CALPHAD coupled phase field modeling of sigma phase formation in duplex stainless steels

SNIC 2018/3-15


SNAC Medium

Principal Investigator:

Joakim Odqvist


Kungliga Tekniska högskolan

Start Date:


End Date:


Primary Classification:

20506: Metallurgy and Metallic Materials

Secondary Classification:

10105: Computational Mathematics

Tertiary Classification:

10105: Computational Mathematics




The importance of steel industry in the prosperity of Swedish economy cannot be overemphasized. For the high performance stainless steel, the Swedish steel companies are world leaders in their respective product areas with a share of almost 60% of world´s duplex stainless steel production. However, in order to maintain its global ranking and to ensure the top-notch quality of its niche products, which are already being copied worldwide, the stainless steel industries need to use the state-of-the-art modeling tools for the development of products and production processes. A decisive factor in determining the quality of stainless steel products is the possibility to form detrimental sigma phase during production and fabrication processes. The formation of sigma phase has always been a serious concern for both the manufacturers and the end users since it causes deterioration of certain properties. For instance, in a commercial duplex stainless steel, 2 vol.% of sigma phase causes the impact toughness to drop from 240 Joule to 50 Joule and that the drop in localized corrosion resistance becomes significant for more than 0.5 vol.% of sigma phase. The proposed project aims to develop a state-of-the-art modeling tool, incorporating realistic kinetics/thermodynamics and microstructures, to identify, analyze and eventually eradicate the factors concerning the composition of alloying elements that result in the formation of sigma phase. A successful implementation of this project would offer predictive capabilities for the production process parameters in terms of i) compositions of primary (Cr, Mo, Ni, N) and ii) secondary (Si, Al, Mn) alloying elements and iii) time-temperature profiles to avoid precipitation of detrimental sigma phase.