The effect of continous transformations on phase diagrams

Nitrogen in chromium-manganese stainless steels: a review on the evaluation of stacking fault energy by computational thermodynamics

Nitrogen in austenitic stainless steels and its effect on the stacking fault energy (SFE) has been the subject of intense discussions in the literature. Until today, no generally accepted method for the SFE calculation exists that can be applied to a wide range of chemical compositions in these systems. Besides different types of models that are used from first-principle to thermodynamics-based approaches, one main reason is the general lack of experimentally measured SFE values for these steels. Moreover, in the respective studies, not only different alloying systems but also different domains of nitrogen contents were analyzed resulting in contrary conclusions on the effect of nitrogen on the SFE. This work gives a review on the current state of SFE calculation by computational thermodynamics for the Fe-Cr-Mn-N system. An assessment of the thermodynamic effective Gibbs free energy, [Formula: see text], model for the [Formula: see text] phase transformation considering existing data from different literature and commercial databases is given. Furthermore, we introduce the application of a non-constant composition-dependent interfacial energy, б γ/ε , required to consider the effect of nitrogen on SFE in these systems.

The Mutual Influence of Magnetic and Chemical Ordering

It can be concluded from experiments that atomic (also called “chemical”) and magnetic ordering reactions exert a mutual influence on each other. In bcc Fe-Al alloys a strong depression of the Curie temperature is observed with the onset of atomic long range order (lro) as compared to the extrapolation of Tc from the random alloys, see Fig. 1. In fcc Co-Pt alloys a depression of the critical temperature of atomic lro L12 →A1 is observed in the Co-rich alloys which are ferromagnetic, as compared to the Pt-rich counterparts which are paramagnetic, see Fig. 2. In this instance it should be noticed that this assymetry is not observed in Ni-Pt allovs where the Curie temperature is inferior to the critical temperatures of atomic lro [1].