Effect of Cd micro-addition on microstructure and mechanical properties in ternary Al-Si-Cu alloy

In present work, Al-7Si-4Cu alloys with/without 0.28 wt % Cd addition were fabricated. Both alloys were solution treated at 500 degrees C for 10 h, followed by quenching and subsequently ageing at 165 degrees C for different times of 0.5-20 h. Results showed that hardness, strength and ductility at peak-aged state for Cd-doped alloy were simultaneously enhanced by comparing with Cd-free alloy. Quantitative analysis results of microstructure indicated that with Cd addition a finer and denser microstructure of theta' can be obtained. Based on microstructure characterization as well as thermodynamics and kinetics calculations, the mechanism for obtaining a finer and denser theta' was discussed, which was considered as a result of the pre-precipitation and heterogeneous nucleation effect of Cd-rich particles. Improved mechanical properties for Cd-doped alloy were discussed to be ascribed to the precipitation of larger number density and less size of theta'. The increase of yield strength with Cd was quantitatively described by the strengthening models. The results indicated that yield strength increment in alloy B was dominated by strengthening contribution of finer and denser theta' precipitates. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

The addition of Cd in Al-7Si-4Cu alloys significantly enhances the mechanical properties, resulting in the formation of a finer and denser θ' microstructure. The improved mechanical properties of the Cd-doped alloy are mainly attributed to the higher number density and smaller size of θ' precipitates, with the increase in yield strength being primarily dominated by the strengthening contribution of the finer and denser θ' precipitates.