Thermodynamically stable hR20 structure of the Al3Er phase studied by varying solidification rate and polymorphic transformation

Jianzhu Wang; Kunyuan Gao; Xiangyuan Xiong; Jing Ning; Xiaolan Wu; Shengping Wen; Wu Wei; Hui Huang; Zuoren Nie; Dejing Zhou

doi:10.20517/microstructures.2026.105

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Research Article Open Access 15 Oct 2026

Thermodynamically stable hR20 structure of the Al₃Er phase studied by varying solidification rate and polymorphic transformation

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Jianzhu Wang¹

,

Kunyuan Gao¹

, ...

Dejing Zhou²

Microstructures 2026, 6, 20260130. 10.20517/microstructures.2026.105

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Abstract

In this study, the crystal structure evolution and microstructure of the Al₃Er phase in an Al-30 wt% Er alloy solidified at different cooling rates were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM). The XRD and EBSD results show that as the cooling rate decreases, the Al₃Er phase transforms from the cP4 structure (60 °C/h) to a mixture of cP4 and hR20 structures (50-40 °C/h), and finally to the hR20 structure (30-5 °C/h). The cP4-structured Al₃Er obtained at 60 °C/h is single-crystalline with an average grain size of 211 μm and exhibits straight boundaries, whereas the hR20-structured Al₃Er obtained at 5 °C/h is polycrystalline with an average grain size of 92 μm and displays wavy boundaries. TEM analysis shows the orientation relationship between the two structures: $$ [1 \overline{2} 1]_{\mathrm{cP} 4} / /[1 \overline{1} 00]_{\mathrm{hR} 20} $$, (111)_cP4//(0006)_hR20. These findings confirm that the stable structure of the Al₃Er phase is hR20. Classical nucleation theory calculation excludes the possibility of direct precipitation of the hR20-structured Al₃Er from the liquid, indicating that it forms through a polymorphic transformation of the cP4-structured Al₃Er. Johnson-Mehl-Avrami-Kolmogorov kinetic analysis yields a critical cooling rate of 36 °C/h for this transformation, consistent with the experimental observations. The high Avrami exponent (n = 6.8) reveals a diffusion-displacive coupled phase transformation mechanism of polymorphic transformation. This work provides a theoretical basis for understanding the structural evolution of the Al₃Er phase and for designing Al-Er alloys.

Keywords

Al₃Er phasepolymorphic transformationthermodynamic stabilitycritical cooling rateautocatalytic nucleation

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REFERENCES

1. Zhao, W.; Liu, G.; Zhang, S.; et al. A review of rare earth elements microalloying in aluminum alloys: Mechanisms of microstructure evolution and Performance Enhancement. J. Mater. Res. Technol. 2026, 41, 2839-69.

2. Mosleh, A. O.; Wang, J.; Pozdniakov, A. V.; et al. Synergistic effect of Fe, Ni, and Er on microstructural stability and high-temperature performance of Al-Cu-Mg alloys. Mater. Charact. 2026, 239, 116687.

3. Knipling, K. E.; Dunand, D. C.; Seidman, D. N. Criteria for developing castable, creep-resistant aluminum-based alloys - a review. Int. J. Mater. Res. 2006, 97, 246-65. https://www.researchgate.net/publication/270227343_Criteria_for_developing_castable_creep-resistant_aluminum-based_alloys_-_A_review (accessed 2026-10-14).

4. Jin, L.; Kang, Y.; Chartrand, P.; Fuerst, C. D. Thermodynamic evaluation and optimization of Al-Gd, Al-Tb, Al-Dy, Al-Ho and Al-Er systems using a modified quasichemical model for the liquid. Calphad 2010, 34, 456-66.

5. Okamoto, H. Al-Er (Aluminum-Erbium). J. Phase. Equilib. Diffus. 2011, 32, 261-2.

6. Ge, Z.; Wei, S.; Liu, Z.; et al. High-strength additively manufacturable Al-Zr-Er-Ni alloys with high as-built ductility and thermal stability. npj. Adv. Manuf. 2025, 2, 48.

7. Gorlov, L.; Loginova, I.; Glavatskikh, M.; Barkov, R.; Pozdniakov, A. Novel precipitation strengthened Al-Y-Sc-Er alloy with high mechanical properties, ductility and electrical conductivity produced by different thermomechanical treatments. J. Alloys. Compd. 2022, 918, 165748.

8. Zhang, Z.; Fan, W.; Long, X.; et al. Er/Sc co-doping enabling laser-powder bed fusion aluminum alloys with superior strength and uncompromised toughness. Rare. Met. 2026, 45, e70427.

9. Xu, Z.; Luan, S.; Tian, S.; Wang, H.; Li, S.; Zhou, L. Effect of erbium on microstructure and properties of AA6061 twin-roll casting sheet. J. Alloys. Compd. 2022, 907, 164458.

10. Cao, P.; Zhu, D.; Wu, N.; et al. Effect mechanism of Er content variations on the mechanical and corrosion properties of T6 state Al-Mg-Si-xEr sheets. J. Mater. Res. Technol. 2024, 29, 1359-76.

11. Moustafa, E. B.; Abushanab, W. S.; Milyani, A. H.; Mosleh, A. O.; Khalil, A. M. Microstructural and mechanical properties of a new Er-modified cast and homogenized AlSiCuMg alloys. J. Alloys. Compd. 2025, 1018, 179144.

12. van Vucht, J. H. N.; Buschow, K. The structures of the rare-earth trialuminides. J. Less. Common. Met. 1966, 10, 98-107.

13. Hu, Z.; Yin, Z.; Lin, J.; et al. Microstructural, electronic, and mechanical properties of L1₂ ordered Al₃Er and Al₃Yb intermetallics: an experimental and first-principles calculations. Mater. Res. Express. 2019, 6, 116516.

14. Kong, Y.; Li, H.; Tao, H.; Liu, W. First-principles study of physical properties of L1₂-Al₃X structural phases for heat-resistant aluminum conductors. Trans. Nonferrous. Met. Soc. China. 2025, 35, 377-91.

15. Villars, P.; Calvert, L. D. Pearson’s Handbook of crystallographic data for intermetallic phases, 2th ed.; ASM International, 1991. https://search.worldcat.org/zh-cn/title/Pearson%27s-Handbook-of-Crystallographic-Data-for-Intermetallic-Phases/oclc/23767318 (accessed 2026-10-14).

16. Wang, J.; Gao, K.; Xiong, X.; et al. Effect of trace Er addition on the age-hardening responses and evolution of Al₃M particles in Al-0.08Sc-0.06Zr alloy aged at 400 °C. Mater. Charact. 2025, 229, 115652.

17. Li, C.; Zhou, Q.; Han, M.; Sha, S.; Luo, Y.; Xu, X. Effect of rare earth element Er on the microstructure and properties of highly alloyed Al-Zn-Mg-Cu-Zr-Ti alloy. J. Alloys. Compd. 2023, 956, 170248.

18. van Vucht, J. H. N. Influence of radius ratio on the structure of intermetallic compounds of the AB3 type. J. Less. Common. Met. 1966, 11, 308-22.

19. Mao, Z.; Seidman, D. N.; Wolverton, C. First-principles phase stability, magnetic properties and solubility in aluminum-rare-earth (Al-RE) alloys and compounds. Acta. Mater. 2011, 59, 3659-66.

20. Meyer, A. Über die kubische und rhomboedrische form des Al₃Er. J. Less. Common. Met. 1970, 20, 353-8.

21. Xu, L.; Shi, X.; Xia, D.; Huang, D.; Tang, H. Experimental investigation and thermodynamic assessment of the Al-Er system. Calphad 2022, 79, 102482.

22. Gao, M. C.; Rollett, A. D.; Widom, M. Lattice stability of aluminum-rare earth binary systems: a first-principles approach. Phys. Rev. B. 2007, 75, 174120.

23. Gao, C.; Gao, K.; Ding, Y.; et al. The phase stability of Al₃Er studied by the first-principles calculations and experimental analysis. Metals 2021, 11, 759.

24. Jiang, C. H. The technique and application of polycrystalline X-ray diffraction. Beijing: Chemical Industry Publishing House, 2014. (in Chinese). https://d.wanfangdata.com.cn/periodical/Ch9QZXJpb2RpY2FsQ0hJTmV3UzIwMjUwMTA0MTcwMjI2Eg1meGh4MjAxNDA4MDIxGggxaDY0YzEzcQ%3D%3D (accessed 2026-10-14).

25. Flemings, M. C. Solidification processing. Metall. Trans. 1974, 5, 2121-34.

26. Glicksman, M. E. Principles of solidification, 1th ed.; Springer, 2011.

27. Gao, Q.; Ai, J.; Tang, S.; et al. Fast crystal growth at ultra-low temperatures. Nat. Mater. 2021, 20, 1431-9.

28. Phase transformations in materials; Kostorz, G., Ed.; Springer. 2001.

29. Dantzig, J. A.; Rappaz, M. Solidification, 2th ed.; EPFL Press, 2016. https://books.google.com/books?id=k1Q-DgAAQBAJ&printsec=frontcover&hl=zh-CN&source=gbs_ge_summary_r&cad=0#v=onepage&q&f=false (accessed 2026-10-09).

30. Du, Y.; Chang, Y.; Huang, B.; et al. Diffusion coefficients of some solutes in fcc and liquid Al: critical evaluation and correlation. Mater. Sci. Eng. A. 2003, 363, 140-51.

31. Johnson, W. A.; Mehl, R. F. Reaction kinetics in processes of nucleation and growth. Trans Am Inst Min Metall Eng 1939;135:416-42. https://onemine.org/documents/papers-reaction-kinetics-in-processes-of-nucleation-and-growth-? (accessed 2026-10-09).

32. Jiang, W.; An, X.; Liu, W.; Ni, S.; Song, M. Microstructure and hardness of solution treated and cold-rolled Co₇₅Cr₂₅ alloy. Mater. Charact. 2021, 181, 111521.

33. Zhang, L.; Yu, P.; Fan, J.; Li, Y.; Gao, Y.; Li, G. High pressure induced the polymorphism phase transition in the Fe₄₀Mn₄₀Co₁₀Cr₁₀ multi-principal element alloy. Intermetallics 2021, 136, 107268.

34. Calabretta, C.; Scuderi, V.; Bongiorno, C.; et al. Impact of nitrogen on the selective closure of stacking faults in 3C-SiC. Cryst. Growth. Des. 2022, 22, 4996-5003.

35. Lu, K.; Wang, J. Activation energies for crystal nucleation and growth in amorphous alloys. Mater. Sci. Eng. A. 1991, 133, 500-3.

36. Blázquez, J. S.; Romero, F. J.; Conde, C. F.; Conde, A. A review of different models Derived from Classical Kolmogorov, Johnson and Mehl, and Avrami (KJMA) theory to recover physical meaning in solid-state transformations. Physica. Status. Solidi. (b). 2022, 259, 2100524.

37. Sun, Z.; Han, G. G. D.; Schmidt-Rohr, K. Partially cooperative phase conversions and noninteger Avrami exponents. J. Phys. Chem. C. 2024, 128, 20765-73.

38. Shewmon, P. G. Diffusion in solids, 2th ed.; Springer Cham, 2016. https://link.springer.com/book/10.1007/978-3-319-48206-4 (accessed 2026-10-14).

39. Yang, Z.; Qiu, N.; Yang, H.; Wang, Y. Vacancies-mediated atomic diffusion controlled by the interfacial structure of FCC/BCC HEA multilayers. J. Alloys. Compd. 2023, 947, 169512.

40. Cahn, J. W. The kinetics of grain boundary nucleated reactions. Acta. Metall. 1956, 4, 449-59.

41. Raghavan, V.; Cohen, M. Measurement and interpretation of isothermal martensitic kinetics. Metall. Trans. 1971, 2, 2409-18.

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Research Article

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Thermodynamically stable hR20 structure of the Al₃Er phase studied by varying solidification rate and polymorphic transformation

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Wang, J.; Gao, K.; Xiong, X.; Ning, J.; Wu, X.; Wen, S.; Wei, W.; Huang, H.; Nie, Z.; Zhou, D. Thermodynamically stable hR20 structure of the Al₃Er phase studied by varying solidification rate and polymorphic transformation. Microstructures 2026, 6, 20260130. https://dx.doi.org/10.20517/microstructures.2026.105

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DOI: https://doi.org/10.20517/microstructures.2026.105

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