The influence of Y content on grain structure evolution in Mg-Y alloys

To advance the understanding of microstructural evolution behavior in Mg-rare earth alloys, the effect of yttrium (Y) addition on static recrystallization and grain growth in Mg alloys was systematically investigated in extruded Mg-1wt.%Y and Mg-7wt.%Y alloys. Y addition was found to significantly retard the microstructural evolution, primarily due to its solute drag effect arising from Y segregation at grain boundaries. The relative intensity of solute drag effects from different alloying elements in Mg alloys was further assessed from both thermodynamic and kinetic perspectives, considering their grain boundary segregation tendencies and diffusivities. Additionally, static recrystallization in Mg-Y alloys was observed to proceed via a two-stage behavior characterized with two distinct JMAK exponents, indicating the heterogeneous nucleation of recrystallized grains. Abnormal grain growth (AGG) behavior was observed in these Mg-Y alloys. Overall, this study highlights the critical role of Y segregation at grain boundaries in controlling recrystallization and grain growth kinetics in Mg-Y alloys. This provides new insights into the design of thermally stable Mg alloys with refined microstructures.