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Lecture

Role of deformation behaviour and recrystallization mechanisms of Mg-Nd and Mg-Ca based alloys

Thursday (07.11.2019)
10:15 - 10:35
Part of:


Rare earth addition is an effective way to weaken the basal texture from rolling process and improve the formability of Mg alloy sheets. A comprehensive understanding of the texture weakening mechanism is important to obtain the high performance Mg alloys. The microstructure and texture evolution during deformation and recrystallization of Mg-Nd and Mg-Ca based alloys were investigated. Shear banding plays an important role in deformation of Mg-Nd alloys, while twinning is favoured in Mg-Ca alloys. Channel die compression was applied to simulate the rolling process. Channel die compression samples deformed to different strain levels reveal the diverse deformation modes. The third alloying element, Zn, contributes to a homogeneous deformation in both Mg-Nd and Mg-Ca alloys, while the Al addition introduces many coarse precipitates due to its a high affinity with Nd and Ca. The activities of different slip modes were investigated by intragranular misorientation axis analysis. The recrystallization mechanisms of different alloys will be discussed in regard to the deformation energy and precipitates distribution. The different deformation behaviours like homogeneous and inhomogeneous deformation have significant impacts on the deformation energy, which is the important driving force for recrystallization. The recrystallization process in Mg-Zn-Nd alloy can be retarded by the precipitates In the Al containing alloys, recovery was preferred in the less deformed grains because of insufficient deformation energy for recrystallization. Some atomic segregation of Zn and Nd at the recrystallized grain boundaries hindered boundary mobility, which attributes to the development of the so called rare earth texture. The nuclei formed within shear bands show weak but comparable components with the deformed matrix. An equivalent growth of the recrystallized grains at the early annealing stage retains the more randomised orientations during grain growth.

Speaker:
Xun Zeng
Helmholtz-Zentrum Geesthacht
Additional Authors:
  • Dr. Sangbong Yi
    Helmholtz-Zentrum Geesthacht
  • Dr. Dietmar Letzig
    Helmholtz-Zentrum Geesthacht
  • Prof. Karl Kainer
    Helmholtz-Zentrum Geesthacht