Enhanced strength-ductility synergy in an Al-Cu alloy via Cd-induced hybrid 0"+0′ precipitation

In this work, trace Cd addition (-0.2 wt%) was exploited in Al-Cu alloys to improve the mechanical properties by introducing the hybrid 0 '' -H 0 ' precipitates, as governed by the solid -solution temperature T . In detail, if the solid solution temperature is low ( T = 500 degrees C), Cd microalloying merely initiates undesirable dual precipitates of 0 '' and 0 ' with similar size and a homogenous distribution. In such case, the Cd-microalloyed Al-Cu alloy suffers from limited optimization on the strength-ductility synergy in comparison to the Cd-free Al-Cu alloy. However, elevating T to 530 degrees C results in the formation of dense Cd-rich nanoparticles, significantly promoting the hybrid 0 '' -H 0 ' precipitation with a bimodal distribution by offering numerous heterogeneous Cd-rich nucleation sites. Such hybrid 0 '' -H 0 ' precipitation imparts the architecture of microstructural heterogeneity, which was found to be responsible for the rapid age-hardening response and enhanced strength-ductility synergy in the Cd-microalloyed Al-Cu alloy.