Dynamic precipitation and strengthening in a Mg-Zn-Gd alloy during hot deformation

Dynamic precipitation and microstructural evolution during hot deformation in a Mg-Zn-Gd alloy were investigated through systematic microstructural characterizations. Fast dynamic precipitation of beta'-Mg7Gd rods was activated along dislocations during plastic deformation in Mg97Zn1Gd2 samples annealed at 773 K for 10 h. Transformation of Mg3GdZn to 14H long-period stacking ordered (LPSO) phase increased solute concentration in Mg matrix by similar to 50% after annealing, which perhaps play an important role in activating dynamic precipitation during subsequent hot deformation, besides assistance of heterogeneous nucleation along dislocations. However, dislocations in cold deformed samples would dissociate upon subsequent annealing at 573 K, producing stacking faults with Suzuki segregation of both Zn and Gd, instead of activating fast precipitation of beta'-Mg7Gd rods. Moving dislocations may attract Gd atoms near their slip planes during hot deformation, which is critical for producing local compositional fluctuation high enough to facilitate dynamic precipitation of beta'-Mg7Gd. Both the formation of H-14 LPSO and dynamic precipitation of beta'-Mg7Gd should play a role in strengthening the Mg97Zn1Gd2 alloy. (c) 2022 Elsevier B.V. All rights reserved.

Automated summary

The dynamic precipitation and microstructural evolution during hot deformation in a Mg-Zn-Gd alloy were investigated through systematic microstructural characterizations. The results showed that the precipitation behavior of different phases in the alloy can be influenced by specific temperature and annealing time, which play an important role in strengthening the alloy.