Enhanced strength-ductility synergy in pure Al by assembling grain and chemical gradients

Titanium (Ti) is generally known for its limited solid solubility and used as grain refiner in Al-based alloys, accelerating heterogeneous α-Al nucleation during solidification. In this study, a newly developed surface modification of pure Al followed by sputtering Ti film (∼1 μm) and subsequent laser remelting has been proposed. Gradient structural features in both grain size and chemical composition have been accomplished in the top surface layer (<10 μm), showing three typical domains with different grain morphology and Al3Ti nanoprecipitates. The simultaneous increase in strength and ductility is attributed to the strong dislocation-precipitate interaction inside gradient nano-grained top-surface layer, which has been confirmed by the partially dissolved Al3Ti nanoprecipitates induced by deformation. The findings in this work provide a new routine for upgrading mechanical properties through the manipulation of both grain- and chemical-gradients.