Abstract:Effects of a minor Ca addition on microstructural stability and dynamic restoration behavior of AlMg5 during hot deformation were investigated. They were studied using scanning electron microscopy (SEM), differential scanning calorimetry (DSC), electron backscatter diffraction (EBSD) analyses and transmission electron microscopy (TEM). JMatPro package was used for simulation of the solidification path of the alloys. The results show that the addition of Ca does not affect the microstructure and hot compression behavior of the as-cast samples. However, it prevents the drastic grain growth during homogenization. It is found that coarse grains of Ca-free alloy promote the dynamic recovery and slow down the dynamic recrystallization during hot compression. Also, the particle stimulated nucleation is suggested as the main nucleation mechanism of new recrystallized grains for hot compressed Ca-free alloy. On the other hand, the microstructure of the hot compressed Ca-added alloy is greatly affected by the presence of Al₄Ca intermetallics. The formation of Al₄Ca phase is predicted by JMatPro and revealed by DSC, SEM and TEM studies. Finally, it is found that the presence of Al₄Ca precipitates on the grain boundaries of Ca-added alloy prevents the growth of α(Al) by Zener pinning effect and results in the stability of microstructure during homogenization.

Key words: AlMg5 alloy; hot compression; homogenization; microstructure; particle stimulated nucleation; Zener pinning effect