Overcoming the strength-ductility trade-off in refractory medium-entropy alloys via controlled B2 ordering

Herein, we showed that controlled additions of Al, which provided a certain degree of B2 ordering, resulted in a ∼ 37%-enhancement of both yield strength and uniform elongation in Alx(NbTiZr)100-x (x = 0; 2.5; 5; 7.5 at.%) refractory medium-entropy alloys. The improvement of properties stemmed from the solid solution and short-range order strengthening, as well as from the alteration in a character of dislocation glide. The B2 ordering caused the formation of multiple dislocation bands and the activation of cross-slip, which improved the macroscopic stability of plastic flow and extended the strengthening stage, thereby postponing necking.