Microstructure Evolution of Twin-Roll Cast and Hot-Rolled WZ73 Alloy during the Finishing Heat-Treatment

Abstract:

The microstructural evolution of the WZ73 magnesium alloy (Mg-7.4Y-3.8Zn-0.4Zr) was systematically investigated during finishing heat-treatments following twin-roll casting and hot rolling at equivalent strain rates of 17 s⁻¹ and 50 s⁻¹. Hot rolling at 500 °C was performed to achieve a logarithmic strain of 0.7 (thickness reduction from 5.3 mm to 3 mm). Higher strain rates during hot rolling enhanced dynamic recrystallization (DRX), resulting in refined microstructures, whereas lower strain rates promoted the formation of lamellar long period stacking ordered (LPSO) phases. Subsequent heat-treatments at 200 °C to 550 °C for up to 24 hours revealed temperature-dependent microstructural transformations. At 500 °C, complete recrystallization occurred with minimal grain growth, while 550 °C caused grain coarsening, partial grain boundary melting, and morphological changes of the LPSO phase from lamellar to spherical and rod-like structures. Notably, at temperatures above 500 °C, prior hot rolling had limited influence on microstructure. The microstructure and phase evolution were characterized using optical and scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD).

• Periodical: Materials Science Forum (Volume 1175)
• Pages: 7-12
• DOI: https://doi.org/10.4028/p-xx8ZtX
• Online since: January 2026
• Authors: Franziska Ueberschär*, Madlen Ullmann, Ulrich Prahl
• Keywords: Finishing Heat-Treatment, LPSO Phase, Microstructure, WZ73

References

[1] J. Freudenberger, M. Heilmaier, Materialkunde der Nichteisenmetalle und -legierungen, Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim, 2020.

[2] M. Ullmann, K. Kittner, T. Henseler, C. Krbetschek, D. Rafaja, R. Kawalla, U. Prahl, Dynamic recrystallization and texture evolution of Mg-6.8Y-2.5Zn-0.3Zr alloy during hot rolling, Procedia Manuf. 50 (2020) 809–816.

DOI: 10.1016/j.promfg.2020.08.146

[3] K. Kittner, M. Ullmann, U. Prahl, A Comparative Study on the Hot Deformation Behavior of As-Cast and Twin-Roll Cast Mg-6.8Y-2.5Zn-0.4Zr Alloy, Materials 14 (2021) 3628.

DOI: 10.3390/ma14133628

[4] B. Chen, X. Li, C. Lu, D. Lin, Recrystallization and microstructural evolution during hot extrusion of Mg97Y2Zn1 alloy, Met. Mater. Int. 20 (2014) 489–497.

DOI: 10.1007/s12540-014-3012-7

[5] K. Kittner, M. Ullmann, F. Arndt, R. Kawalla, U. Prahl, Microstructure and Texture Evolution during Twin-Roll Casting and Annealing of a Mg–6.8Y2.5Zn–0.4Zr Alloy (WZ73), Crystals 10 (2020) 513.

DOI: 10.3390/cryst10060513

[6] X. Zhou, C. Liu, Y. Gao, S. Jiang, X. Han, Z. Chen, Evolution of LPSO Phases and Their Effect on Dynamic Recrystallization in a Mg-Gd-Y-Zn-Zr Alloy, Metall. Mater. Trans. A 48 (2017) 3060–3072.

DOI: 10.1007/s11661-017-4081-2

[7] J. Xiao, Z. Chen, J. Shao, T. Chen, X. Lin, C. Liu, Evolution of long-period stacking ordered phases and their effect on recrystallization in extruded Mg-Gd-Y-Zn-Zr alloy during annealing, Mater. Charact. 167 (2020) 110515.

DOI: 10.1016/j.matchar.2020.110515

[8] R. Lu, J. Wang, Y. Chen, D. Qin, W. Yang, Z. Wu, Effects of heat treatment on the morphology of long-period stacking ordered phase, the corresponding damping capacities and mechanical properties of Mg–Zn–Y alloys, J. Alloys Compd. 639 (2015) 541–546.

DOI: 10.1016/j.jallcom.2015.03.208

[9] X.R. Dong, H. Yu, S.M. Kang, W. Yu, B.A. Jiang, D. Chen, Z.F. Wang, F.X. Yin, K.S. Shin, A comparable study of Mg98.15Y1Zn0.85 sheets fabricated by twin-roll casting and direct-chill casting and related annealing behavior, Mater. Sci. Eng. A 815 (2021) 141316.

DOI: 10.1016/j.msea.2021.141316

[10] T. Itoi, T. Suzuki, Y. Kawamura, M. Hirohashi, Microstructure and Mechanical Properties of Mg-Zn-Y Rolled Sheet with a Mg<SUB>12</SUB>ZnY Phase, Mater. Trans. 51 (2010) 1536–1542.

DOI: 10.2320/matertrans.L-M2010816

[11] Y. Meng, Q. Chen, S. Sugiyama, J. Yanagimoto, Effects of reheating and subsequent rapid cooling on microstructural evolution and semisolid forming behaviors of extruded Mg–8.20Gd–4.48Y–3.34Zn–0.36Zr alloy, J. Mater. Process. Technol. 247 (2017) 192–203.

DOI: 10.1016/j.jmatprotec.2017.04.001

[12] C. Zheng, S. Chen, M. Cheng, S. Zhang, Y. Li, Y. Yang, Controlling dynamic recrystallization via modified LPSO phase morphology and distribution in Mg-Gd-Y-Zn-Zr alloy, J. Magnes. Alloys 11 (2023) 4218–4234.

DOI: 10.1016/j.jma.2023.01.006

[13] L. Yuan, G. Bi, Y. Li, J. Jiang, Y. Han, D. Fang, Y. Ma, Effects of solid solution treatment and cooling on morphology of LPSO phase and precipitation hardening behavior of Mg–Dy–Ni alloy, Trans. Nonferrous Met. Soc. China 27 (2017) 2381–2389.

DOI: 10.1016/S1003-6326(17)60264-4