Research on microstructure and mechanical properties at elevated temperature of Al-Mg-Si-Sc-Zr alloy strengthened by Al3(Sc, Zr) nanoprecipitates

Abstract

In this work, a newly designed Al-Mg-Si-Sc-Zr alloy was prepared to study the effect of Al3(Sc, Zr) nanoprecipitates on microstructure evolution and high-temperature properties. Modified by Sc, Zr, huge dendritic grains were refined to small equiaxed grains, and coarse intermetallics along grain boundaries were also modified to small pieces. Numerous Ll2-ordered Al3(Sc, Zr) nanoprecipitates with spherical shape ranging from 20 nm to 60 nm generated during heat treatment, and they were fully coherent with α-Al matrix. During cold rolling deformation, a further DRV, DRX happened in Al-Mg-Si-Sc-Zr alloy due to severe dislocation accumulation caused by Al3(Sc, Zr) nanoprecipitates. Compared with Al-Mg-Si matrix alloy, the YS, UTS and EL of Al-Mg-Si-Sc-Zr alloy at 250 ℃ were increased by 26.0%, 25.1% and 22.3% respectively. At elevated temperature, nanosized Al3(Sc, Zr) particles with excellent coarsening resistance could well maintain their morphology and structure. These thermally stable Al3(Sc, Zr) nanoprecipitates can retard dislocation motion and pin grain boundaries effectively during high-temperature tensile process, contributing to the prominent enhancement on the matrix alloy at elevated temperature.