Yunhao Fan1, Gaoming Zhu1, Huamiao Wang1, Leyun Wang1*, Xiaoqin Zeng1

Shanghai Jiao Tong University, Shanghai, 200240, China

EXTENDED ABSTRACT: Synergy between Ca and other alloying elements such as Al and Zn can modify the microstructure and thus enhance the mechanical properties of Mg alloys [1, 2]. To find out the most appropriate amount of Ca addition, we prepared four alloys (AZ62, AZX6205, AZX621, and AZX622) with 0, 0.5wt.%, 1.0wt.%, and 2.0wt.% Ca addition in an Mg-6Al-2Zn (wt.%) alloy. Tensile properties of these four alloys did not monotonically change with Ca concentration. The underlying reasons were explored using in situ synchrotron X-ray diffraction, electron microscopy, and cyclic loading tests. It is found that Ca addition in general reduces the yield strength of the alloys. With 0.5wt.% Ca addition, the material's strain hardening capacity is significantly enhanced due to the formation of fine Al2Ca particles. Those Al2Ca particles are internally deformable but nonshearable by dislocations, imposing a long-range back stress for strain hardening. With 2.0wt. % Ca addition, however, the material's ductility would significantly deteriorate due to the formation of excessive and large Al2Ca particles, which not only become crack initiation sites, but also inhibit dislocation generation. An elastic­viscoplastic self-consistent (EVPSC) model was employed to simulate the deformation of the four alloys. Discrepancies between the simulation results and the experimental measurements mostly occur in the microscopic level (e.g. lattice strains and dislocation density evolution), and the reasons will be discussed.

Keywords: Mg alloys; ductility; work hardening; backstress; synchrotron X-ray diffraction

REFERENCES

[1] G. Zhu, L. Wang, J. Wang, J. Wang, J.-S. Park, X. Zeng, Acta Mater., 200, (2020) 236-245

[2] J. Wang, G. Zhu, L. Wang, E. Vasilev, J.-S. Park, G. Sha, X. Zeng, M. Knezevic, J. Mater. Sci. Technol., 84, (2021) 27-42