Synergistic effect of Y and Ca addition on the texture modification in AZ31B magnesium alloy

Tweaking the amount of precipitation and solute segregation is a successful strategy employed in modern micro-alloyed Mg alloys to tailor the microstructure and texture towards improved strength and formability. In the current work, Ca and / or Y are added to AZ31B alloy to examine the synergistic effect of various alloying elements on the texture and microstructure evolution during recrystallization and grain growth. The work examines the segregation behavior of alloying elements with respect to different matrix compositions and different grain boundaries and aims at gaining insights into favorable growth mechanisms that lead to texture modifications. The results demonstrate that in the AZW alloy (Mg-3Al-1Zn-1.0Y wt.%) no Y solute was available in the matrix due to precipitation with Al and Mn. Hence, the texture of this alloy was very similar to typical magnesium basal textures. By the co-addition of Ca and Y in the AZWX alloy (Mg-3Al-1Zn-0.3Ca-1.0Y wt.%), the amount of Ca solute in the matrix remained large enough because Y replaced Ca in forming stable Al ₂ Y precipitates. This resulted in a strong texture modification on the basis of Ca availability in solid solution and its co-segregation with Al and Zn at grain boundaries. The recrystallization kinetics in the AZWX alloy was therefore markedly retarded due to solute and precipitation related effects. Correspondingly, the AZW alloy showed the fastest recrystallization kinetics due to the lack of solute drag at the grain boundaries. The third alloy, AZX (Mg-3Al-1Zn-0.3Ca) containing Ca but no Y was in between because it demonstrated grain boundary segregation but less than the counterpart in the AZWX alloy. It is believed that the co-addition of Ca and Y to the basic Mg-Al-Zn alloy magnifies the synergistic role of solute elements in triggering anisotropic segregation among grain boundaries. This seems significant in modifying the grain boundary mobility characteristics during growth, which grants non-basal grains a growth advantage, resulting in annealing texture modification. This work sheds light on a successful magnesium alloying strategy by tailoring the type and level of precipitation and anisotropic segregation to achieve a desired texture modification.