5Spinodal decomposition in advanced stainless steels | Hierarchic Engineering of Industrial Materials, HERO-M

Spinodal decomposition in advanced stainless steels

 

Spinodal decomposition may occur in materials with a miscibility gap in the phase diagram and leads to demixing on the atomic scale. After prolonged heat treatment or service at elevated temperatures this leads to an increased hardness and strength. However, it may also cause embrittlement at low temperatures. In fact, the upper service temperature of duplex stainless steels is limited by the embrittlement caused by spinodal decomposition. 


The scientific goal is to develop a method for prediction of the effect of individual alloying elements, stress state and temperature on phase equilibria, reaction kinetics, morphology and finally the effect of the morphology on the resulting properties. The industrial goal is to improve the performance of the materials by e.g. decreasing the kinetics via an alloying strategy to increase the upper service temperature of the important duplex stainless steels.


The main focus is on developing a multicomponent phase-field model that could handle the influence of stress state and also concurrent precipitation of e.g. carbides during thermal aging. The experimental work will continue with a systematic study of the influence of different alloy elements and temperature on the kinetics of the decomposition using e.g. TEM, Atom Probe Tomography and Small-Angle Neutron Scattering.

 

 

Xiong_Calphad2011.jpg

Figure: Phase separation in Fe-Cr (Xiong et al., Calphad 2011)

 

 

 

 

Project started in 2007