Hierarchical structure in Al-Cu alloys to promote strength/ductility synergy

Abstract

Experimental evidence demonstrated that equal channel angular pressing (ECAP) at cryogenic temperature, in comparison with ECAP at room temperature, led to promoted strength-ductility synergy in an Al-2.5wt.%Cu alloy. The simultaneous improvement is related to microstructural hierarchy of multimodal grains, low angle grain boundaries, and inter/intragranular precipitates, which was tuned by aging treatment in match with the low-temperature ECAP. The artificial aging could maintain multimodal grain size distribution, introduce a large number of low angle grain boundaries and produce intragranular precipitates to improve strength/ductility. A minor 0.3wt.% Sc addition was effective in optimizing the precipitations and further boosting the strength/ductility combination. The underlying mechanisms for higher strength and greater ductility were rationalized in terms of the low-temperature ECAP.