High-temperature stability of chemically architectured high entropy alloys studied by X-ray diffraction and diffusion modelling
Résumé
Chemically architectured high entropy alloys are an original concept of microstructure which is based on a metastable 3D network of composition fluctuations, named interphase. In the present work the evolution of CoCrFeMnNi-Ni architectured alloys at high temperatures was studied through long duration annealing at 500 and 800°C followed by microstructure characterization using scanning electron microscopy coupled with energy dispersive X-ray spectroscopy mapping and X-ray diffraction (XRD). Concentration evolution induced by the annealing was also modelled by diffusion simulations using DICTRA software. It results that the microstructure of CoCrFeMnNi-Ni chemically architectured alloys is stable at intermediate temperatures with no or slight microstructure evolution (below 500 or around 650°C depending on the initial thickness of the interphase). At higher temperature, architectured alloys tend to homogenize. Finally, a specific Rietveld XRD analysis was proposed for a quantification of phase fraction in high entropy alloys, applicable for architectured or not alloys.