“…The traditional solid solution strengthening models (Varvenne et al, 2017;Labusch et al, 1972) were developed with an assumption of dilute alloys, while this assumption is clearly not valid any more in the case of HEAs and MEAs, where the definitions of solute and solvent break down (Okamoto et al, 2016;Varvenne et al, 2016a;Coury et al, 2019;Zhao and Nieh, 2017). Moreover, the models for solid solution strengthening were generally based on an assumption of a random distribution of atoms in the alloy, while more recently, chemical short-range order (CSRO) (Zhang et al, 2017;Li et al, 2019;Zhang et al, 2018;Zhang et al, 2020;Fantin et al, 2020;Varvenne et al, 2016b;Sadigh et al, 2012;Kostiuchenko et al, 2020) and local composition fluctuation (Jian et al, 2020) have also been found to play important roles in the mechanical behaviors of HEAs and MEAs. The local chemical structure/ ordering and the local composition fluctuation can be experimentally characterized by extended X-ray absorption fine structure (EXAFS) techniques (Varvenne et al, 2016a;Zhang et al, 2017) and atomic resolution energy-dispersive X-ray spectroscopy (EDS) mapping using aberration-corrected TEM (Kostiuchenko et al, 2020;Zhang et al, 2020).…”