Enhanced high-temperature age-hardening behavior and mechanical properties of Al–Mg–Si alloys via microalloying with Cd

Abstract

The effects of trace (0.05 at.%) Cd addition on the high-temperature (250 °C) age-hardening behavior, precipitate microstructure and room-temperature tensile properties of an Al-0.8Mg-0.8Si (wt.%) alloy were investigated. The results showed that the Cd addition not only accelerated the precipitation kinetics but also increased the peak hardness of Al–Mg–Si alloys. The quantitative analysis of the peak-aged precipitates based on (high-resolution) transmission electron microscopy images indicated that the Cd addition refined the size of needle-shaped precipitates and increased their number density. High-angle annular dark-field scanning transmission electron microscopy characterizations revealed that the Cd addition stimulated the heterogeneous nucleation of β" on the early formed nanosized Cd-rich precipitates and Cd-containing QP lattices, resulting in a much-refined precipitate microstructure. Furthermore, the Cd addition also enhanced the room-temperature tensile properties of the peak-aged alloy. The Cd-added alloy exhibited higher yield strength, ultimate tensile strength, and total elongation than the Cd-free alloy, which was due to the refined precipitate microstructure and narrowed precipitate-free zone along the grain boundaries.