Effect of annealing on microstructure and mechanical properties of an Al-Mg-Sc-Zr alloy

Understanding the microstructural stability and mechanical response of Al-Mg-Sc-Zr alloys at high temperatures is significant to broaden their aerospace applications. In this study, the effect of annealing temperatures (300, 500, 550 degrees C) and durations (1, 24, 72 h) on the recrystallization behavior, precipitate evolution and mechanical properties of an Al-6.15Mg-0.3Sc-0.15Zr alloy was investigated comprehensively. Results showed when the annealing temperature was low (<500 degrees C), the movement of dislocation and the migration of grain/sub-grain boundaries was hindered by precipitates. As the annealing temperature reached 500 degrees C, the hindering effect diminished due to the coarsening of precipitates. The size of Al-3(Sc,Zr) precipitates increased apparently when annealed at 550 degrees C for 72 h. Meanwhile, recrystallization occurred due to the diminishing of precipitates hindering. The texture of recrystallized grains was strongly related to the size and density of the Al-3(Sc,Zr) precipitates. In additional, the strength of the material decreased with increasing the annealing temperature and duration. This material softening phenomenon was analyzed statistically. Results indicated that the strength drop at 500 degrees C was mainly due to the coarsening of precipitates and the decrease of dislocation density, while the sharp strength decrease at 550 degrees C was also attributed to the coarsening of grains.

Automated summary

In this study, the effect of annealing temperatures and durations on the recrystallization behavior, precipitate evolution, and mechanical properties of Al-Mg-Sc-Zr alloys was comprehensively investigated. Results showed that precipitates hindered the movement of dislocation and migration of grain/sub-grain boundaries at low annealing temperatures, but the hindering effect diminished and recrystallization occurred at higher temperatures. The size of Al-3(Sc,Zr) precipitates increased with longer annealing durations. Moreover, the strength of the material decreased with increasing annealing temperature and duration.