Superior strength-ductility synergy in Ti ₂ ZrNbVAl _x alloys enabled by tuning chemical ordering via Al addition

Lightweight high-entropy alloys(LWHEAs) typically exhibit limited room-temperature ductility. Here, we show that Al-induced chemical ordering can be used to regulate deformation behavior in ac-cast Ti2ZrNbVAlx LWHEAs featuring dendritic segregation Although all alloys exhibit nominally single-phase BCC structure, increasing Al content introduces nanoscale B2-type ordering from grain boundaries into grain interiors. An intermediate degree of ordering promotes dislocation storage capacity, and producing a pronounced strength-ductility synergy. In contrast, excessive intragranular ordering constrains dislocation motion, enforces slip localization, and triggers quasi-cleavage fracture. These results reveal that the spatial distribution and continuity of chemical ordering, rather than its mere presence, govern mechanical performance in BCC LWHEAs with heterogeneous dendritic microstructures.