Probing temperature effects on lattice distortion and oxidation resistance of high-entropy alloys by in situ SR-XRD and XANES

To investigate lattice distortion evolutions of CrCoNi medium-entropy alloy (MEA), CrFeCoNi, and CrMnFeCoNi high-entropy alloys (HEAs) with temperature increasing from 300 to 1323 K, we conduct in situ synchrotron-radiation-based X-ray diffraction experiments. Electron backscattering diffraction, energy-dispersive X-ray spectroscopy and X-ray absorption near edge fine structure spectra (XANES) are further carried out to uncover variations of microstructure, morphology and oxidation resistance. Generally, the lattice will expand continuously with temperature increasing, however, the expansion rate is affected by grain growth and oxidation. The oxidation resistance of CrCoNi MEA is slightly higher than CrFeCoNi HEA, and much higher than CrMnFeCoNi HEA. The XANES spectra demonstrate higher oxidation resistance of Ni, Co, and Fe than Cr and Mn. Formation of local short-range order structures around Ni and Co is observed, but no such features are observed around Fe and Mn. The present findings are significant on deepening the understandings of correlations between atomic structure and mechanical properties in advanced HEAs. Graphic Abstract