Microstructures and micromechanical behaviors of high entropy alloys investigated by synchrotron X-ray and neutron diffraction techniques: a review

High-entropy alloys (HEAs) have excellent characteristics, including corrosion resistance, irradiation resistance, and mechanical properties. A few HEAs have become alternative application materials in various fields, such as aerospace and defense technology. Comprehensive investigation of the deformation mechanisms of HEAs can guide microstructure control and toughness design, which is of vital significance for the understanding and exploration of advanced structural materials. Synchrotron X-ray and neutron diffraction techniques are required tools for materials science research, especially for in situ coupling of physical/chemical fields and for resolving macro/microcrystallographic information about materials. In recent years, many scholars have used synchrotron X-ray and neutron diffraction techniques to investigate the deformation mechanisms, phase transformations, stress behaviors, and in situ processes of HEAs, such as variable-temperature, high-pressure and hydrogenation processes. Herein, we present the principles and development of neutron and synchrotron radiation technology and their applications in the deformation mechanisms of HEAs. The factors influencing the deformation mechanisms of HEAs are also summarized. We focus on their microstructures and micromechanical behaviors during tension/compression or creep/fatigue deformation, and we study the application of synchrotron X-ray and neutron diffraction techniques to the observation of dislocations/stacking faults/twins/phases and intergrain/interphase stress changes. Outlooks on the future development of synchrotron X-ray and neutron diffraction techniques and on the study of deformation mechanisms of new metals are discussed.