In situ diffraction analysis using high energy synchrotron radiation to investigate the influence of active deformation and recrystallisation mechanisms on the microstructural development of new magnesium sheet alloys
Mechanical Properties of Metallic Materials and their Microstructural Origins
Final Report Abstract
The main aim of the project was to understand the influence of deformation and recrystallization mechanisms in rare-earth or calcium and combination with Zn alloyed Mg, compared to the single addition of Zn alloys. We revealed that the addition of Nd or Ca to pure Mg leads to a higher activation of prismatic dislocation slip, which acts as a main deformation mechanism under tensile loading in comparison with to binary Mg-Zn alloys. Concurrently, a retardation of the recrystallization behavior, i.e. delayed relaxation of dislocation densities is revealed. In succession, the higher activation of the prismatic dislocation leads to texture development, i.e., a spread basal pole perpendicular to the LD. The former is enhanced in combination with the addition Zn, i.e. ZN10 and ZX10. In order to reveal the abovementioned finding, the microstructure and texture developments were investigated at different levels of deformation in same volume area by the diffraction peak profiles using the synchrotron X-ray radiation, consequently, by in-grain misorientation analysis using the scanning electron microscopy and by texture simulations using a (e)VPSC model.
The project started with observation of texture development in different Mg alloys, containing rare-earth and calcium, and their ternary alloys combined with Zn. Comparison was carried out to the binary Mg- Zn alloys (modified with Zr for grain refinement) in this study as an example for a conventional Mg alloy, which develops a strong basal texture. All examined alloys were hot-rolled and annealed with different conditions in order to minimize the influence of the grain sizes and to avoid statistic issue for the in-situ diffraction experiments during tensile loading. Using these different Mg alloy sheets having different initial textures, the experimental investigations of the activated dislocation slip systems as well as the recrystallization behaviors as aspect with the addition of alloying element at different temperatures were successfully carried out. The Nd or Ca containing Mg alloys showed approximately 150-200% increases of the nonbasal dislocations during tensile deformation, especially prismatic dislocations, compared to the Nd- and Ca-free counterpart, and the nonbasal dislocations in ternary alloys containing Zn and Nd or Ca increased approximately by 200-250%.
Our experimental investigations showed that the activated prismatic slips by the addition of Nd or Ca leaded to a texture development which is broadened in the basal pole perpendicular to the LD during tensile deformation. Particularly the texture development was enhanced in combination of Zn and –Nd or –Ca due to the stronger activation of prismatic slips than other examined alloys. Furthermore, the Nd or Ca containing Mg alloys showed the retained activation of nonbasal dislocation density at elevated temperatures, while the free-Nd or –Ca containing Mg alloy showed the distinct relaxation of the dislocation densities accompanying the reduced activation of nonbasal - as well as
Publications
- “Texture and lattice strain evolution of Mg ZN202 during tension at RT, 100°C and 200°C by in-situ synchrotron diffraction”, 6 th International Conference on Magnesium, Shenyang, China, 23-26 September 2017
X. Zhou, C. Ha, S. Yi, J. Bohlen, B. Schwebke, Z. Zhong, N. Schell, H.-G. Brokmeier
- “Deformation and Recrystallization Mechanisms and Their Influence on the Microstructure Development of Rare Earth Containing Magnesium Sheets”, Magnesium Technology 2018, 2018, 209-216
C. Ha, S. Yi, J. Bohlen, X. Zhou, H.-G. Brokmeier, N. Schell, D. Letzig, K. U. Kainer
(See online at https://doi.org/10.1007/978-3-319-72332-7_33) - “Mobility of pinned twin boundaries during mechanical loading of extruded binary Mg-1Zn alloy”, Materials Characterization 139, 2018, 81-88
D. Drozdenko, P. Dobroň, S. Yi, K. Horváth, D. Letzig, J. Bohlen
(See online at https://doi.org/10.1016/j.matchar.2018.02.034) - “Study of deformation mechanisms in Mg-Zn-Nd alloys by using in-situ synchrotron diffraction”, Proceeding of the 11th International Conference on Magnesium Alloys and Their Applications, 2018, 214-219
C. Ha, S. Yi, J. Bohlen, X. Zhou, H.-G. Brokmeier, N. Schell, D. Letzig, K. U. Kainer
- Tension-compression asymmetry of extruded Mg-Gd-Y-Zr alloy with a bimodal microstructure studied by in-situ synchrotron diffraction, Materials & Design, Volume 170 (2019), 10775
Y.Q. Chi, X.H. Zhou, X.G. Qiao, H.G. Brokmeier, M.Y. Zheng
(See online at https://doi.org/10.1016/j.matdes.2019.107705) - “Influence of Nd or Ca addition on the dislocation activity and texture changes of Mg–Zn alloy sheets under uniaxial tensile loading”, Materials Science & Engineering A 761, 138053, 2019
C. Ha, J. Bohlen, S. Yi, X. Zhou, H.-G. Brokmeier, N. Schell, D. Letzig, K. U. Kainer
(See online at https://doi.org/10.1016/j.msea.2019.138053) - “Processing effects on the formability of extruded flat products of three magnesium alloys”, Frontiers in Materials – Structural Materials 6:253 (2019)
M. Nienaber, K. U. Kainer, D. Letzig, J. Bohlen
(See online at https://doi.org/10.3389/fmats.2019.00253) - “Texture and lattice strain development of ZK10 and ZN10 studied by in-situ synchrotron diffraction at RT, 100°C and 200°C”, Annual Texture Symposium of DGM, Garching, Germany, 28. -29. March 2019
X. Zhou, C. Ha, S. Yi, J. Bohlen, N. Schell, H.-G. Brokmeier
- “The effect of Nd or Ca addition on dislocation activity and texture development in Mg-Zn alloys sheets”, Annual Texture Symposium of DGM, Garching, Germany, 28.-29. March 2019
C. Ha, S. Yi, J. Bohlen, X. Zhou, H.-G. Brokmeier, N. Schell, D. Letzig, K. U. Kainer
