Experimental and computational assessment of the temperature dependency of the stacking fault energy in face-centered cubic high-entropy alloys

The activation of deformation mechanisms in face-centered cubic materials is considered closely related with the stacking fault energy. Experimentally determined stacking fault energy (SFE) values are exclusively positive. However, results obtained by first principle methods predict that the intrinsic SFE of metastable face-centered cubic metals and alloys is negative. It was previously shown that SFE values from the first principle methods and experiments can be reconciled by accounting for the resolved shear stress for Shockley partial dislocations. Determining this resolved shear stress for Shockley partial dislocations is experimentally challenging, making the reconciliation of experimental and first-principles SFE values a laborious exercise. In the present contribution, we demonstrate that the critical resolved shear stress for Shockley partial dislocations and SFE values can be determined from a single in-situ neutron diffraction experiment, thus enabling more confident and efficient reconciliation of experimental and theoretical SFE values

Modelling nitriding of iron: From thermodynamics to residual stress

The present article presents a few selected aspects of the modelling of gaseous nitriding of pure iron. After descriptions of the thermodynamics of the gas phase and the reactions at the gas/solid interface, a model description of the thermodynamics of $\gamma'-Fe_{\rm 4}N{\rm 1-x}$ is given, which takes the long-range ordering of nitrogen atoms into account. Subsequently, the kinetics of nucleation and growth of iron nitride layers is described in terms of the rates of the surface reactions and solid state diffusion. Thereafter, the mechanisms of stress generation in $\gamma'-Fe_{\rm 4}N{\rm 1-x}$ layers during nitriding are summarized. Finally, the model for stress development in $\gamma'-Fe_{\rm 4}N{\rm 1-x}$ layers is compared with published experimental work