Abstract . Single-phase high- and medium-entropy alloys with face-centred cubic (fcc) structure can exhibit high tensile ductility 1 , 2 and excellent toughness 2 , 3 , but their room-temperature strengths are low 1 , 2 , 3 . Dislocation obstacles such as grain boundaries 4 , twin boundaries 5 , solute atoms 6 and precipitates 7 , 8 , 9 can increase strength. However, with few exceptions 8 , 9 , 10 , 11 , such obstacles tend to decrease duc...