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Thermodynamic Modeling of the Al-Li-Zr Ternary System Zhaohui Long1,2 • Dongyu Cui1,2 • Hongxing Hu1,2 • Zhi Li1,2 • Fucheng Yin1,2 Touwen Fan3

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Submitted: 21 June 2020 / in revised form: 28 June 2020 Ó ASM International 2020

Abstract Using CALPHAD method, the Al-Zr, Al-Li and Al-Li-Zr systems have been reassessed based on the latest experimental phase relations from literatures and the firstprinciple calculation of the formation enthalpy for ternary compound T1(AlLi2Zr) in this work. The excess Gibbs energies of solution phases, including liquid, bcc, fcc and hcp, were expressed by the Redlich–Kister polynomial. The stoichiometric compounds, i.e. Al4Zr5, Al3Zr5, AlZr2, AlZr3, Al2Li3, Al4Li9 and T1(AlLi2Zr), were modeled as stoichiometric model and the non-stoichiometric compounds, i.e. Al3Zr, Al2Zr, Al3Zr2, AlZr, Al3Zr4, Al2Zr3, AlLi2 and T2(AlLix?yZr5-x), were described with different sublattice models. Finally, a set of reasonable thermodynamic parameters for Al-Li-Zr ternary system have been obtained, which notes a clear improvement on the selfconsistency. The calculated isothermal section at 470 K of Al-Li-Zr system was in reasonable agreement with the experimental one. Keywords Al-Li-Zr  Al-Zr  CALPHAD  phase diagram

& Zhaohui Long [email protected] 1

Key Laboratory of Materials Design and Preparation Technology of Hunan Province, Xiangtan University, Xiangtan 411105, Hunan, People’s Republic of China

2

School of Materials Science and Engineering, Xiangtan University, Xiangtan 411105, Hunan, People’s Republic of China

3

School of Materials Science and Energy Engineering, Foshan University, Foshan 528000, Guangdong, People’s Republic of China

1 Introduction Aluminum and its alloys are known as the materials used for aviation, aerospace, automotive and etc. Zirconium and Lithium are important alloy elements for aluminum. Mechanical properties of aluminum alloy are improved by adding Zr and Li.[1,2] In Al-Li-Zr ternary system, Al-Zr covalent bond in Al3Zr is greater than the Al-Li covalent bond in Al3Li, leading to Al3Zr using as an inhomogeneous nucleus for Al3Li, which improve the strength and toughness of alloy.[3] Studied by classical nucleation theory, Al3Zr is a nucleation substrate for Al3Li.[4] Furthermore, Wang et al.[5] reported bimodal-grained Al-Li/Al-Li-Zr laminated composite owns high strength and ductility. It is realized that the calculation of phase diagrams (CALPHAD) approach is a useful tool to establish thermodynamic databases which bases for the predictions of thermodynamic properties, phase diagrams, DICTRA[6] and phase-field simulations.[7] According to the latest report,[8] the liquidus and solidus between 20 and 94.6 at.% Zr at 1573–2133 K of Al-Zr system have been measured. Furthermore, a new phase AlLi2 has been discovered in Al-Li binary system[9] and two new ternary compounds have been found in Al-Li-Zr ternary system.[10] However, the experimental information mentioned above was not considered by recent assessments.[11–17] In order to describe these systems more reason