Dynamic Precipitation Behavior of a Mg-Zn-Ca-La Alloy During Deformation

The dynamic precipitation behavior of a Mg-Zn-Ca-La alloy during deformation has been investigated. A large amount of fine precipitates was detected after deformation, indicating that dynamic precipitation occurred. The precipitates at the grain boundaries included Ca2Mg6Zn3 and Mg4Zn7, whereas the intergranular precipitates were mainly Mg4Zn7. Ca, which has a large atomic radius, preferred to segregate to grain boundaries, where it resulted in the formation of Ca2Mg6Zn3. Zn, which has a similar diffusion coefficient to Mg, resulted in Mg4Zn7 being distributed around the matrix. The stability of the Mg4Zn7 phase was enhanced in the as-extruded Mg-Zn-Ca-La alloy. The grain-boundary precipitates acted as effective obstacles to grain growth, giving rise to the formation of a refined microstructure. The intragranular Mg4Zn7 precipitates hindered the mobility of dislocations, improving the mechanical properties. Additionally, a high density of ultrafine nanoparticles was detected in the un-dynamically recrystallized (DRXed) region, being related to the high density of dislocations therein.