Thermally stable strength-ductility synergy in Al-Mg matrix composites via interval oxidation

A bimodal-grained Al-Mg matrix composite with thermally stable strength-ductility synergy is developed via an interval oxidation (IO) powder processing strategy. In-situ formed MgO and Al4O4C nanoparticles are uniformly embedded in ultrafine grains, which replace metastable Al-Mg nano-precipitates for strengthening, and suppress Mg segregation during long-term thermal exposure at 80℃. The IO-processed composite achieves a high yield strength of 629.8 MPa with 7.3% uniform elongation, and retains over 94% of its strength and 97% of its ductility after thermal exposure. Enhanced density gradient of geometrically necessary dislocations and damage delocalization mechanisms collectively contribute to the high ductility.