Key Takeaways & Executive Findings
- •• Adding 0.2 wt.% La to cast Al-Mg-Si alloy simultaneously improves tensile strength and electrical conductivity, achieving UTS of 170 MPa and conductivity of 44.0% IACS. • La addition refines α-Al grains, promotes Mg2Si precipitation, and transforms AlFeSi phase from continuous to discontinuous, enhancing mechanical and electrical properties. • The improvements over La-free alloy are significant: UTS +9.0%, YS +15.8%, elongation +70.3%, and conductivity +17.3%. • Excessive La content deteriorates properties, indicating an optimal La concentration for balanced performance.
Abstract
Lightweight aluminum alloy conductor materials (Al-Mg-Si alloys) require not only high electrical conductivity to reduce electrical loss, but also high strength to withstand extreme weather conditions. To improve electrical conductivity and mechanical properties of Al-Mg-Si alloy simultaneously, the rare earth La was introduced to modify the Al-Mg-Si alloy. The effect of La addition on the microstructure, tensile properties and electrical conductivity of cast Al-Mg-Si alloy was investigated systematically. Results indicate that the appropriate La content is helpful to improve the strength and electrical conductivity of Al-Mg-Si alloys. When the addition of La is 0.2wt.%, the α-Al grains are refined apparently, Mg and Si solute atoms in the Al matrix are reduced by the formation of Mg2Si phase; the distribution of Al11La3 phases is uniform, and the morphology of AlFeSi phase transforms from continuous state to discontinuous state. The Al-Mg-Si-0.2La alloy exhibits the optimal tensile properties and electrical conductivity, with an ultimate tensile strength of 170 MPa, a yield strength of 88 MPa, an elongation of 18.9%, and an electrical conductivity of 44.0% IACS. These values represent improvements of 9.0%, 15.8%, 70.3%, and 17.3%, respectively, compared to the Al-Mg-Si alloy without La addition. However, excessive La deteriorates the properties of Al-Mg-Si-xLa alloys.
1. Introduction
With the construction of a new type of power system and the transition of clean and low-carbon energy, there is an urgent requirement for lightweight aluminum and aluminum alloy conductor materials with excellent comprehensive properties. For example, aluminum alloy conductor materials require not only high conductivity to reduce electrical loss rates, but also high strength to effectively withstand extreme weather conditions [1].
Compared with pure aluminum, the strength of Al-Mg-Si alloy (a typical conductor material) is significantly enhanced, but the electrical conductivity is decreased seriously [2-5]. The contradiction between electrical conductivity and strength is the key problem that limits its wide application. In general, the electrical conductivity of alloy is very sensitive to the solute atoms, which usually intensify the electron scattering, therefore, leading to a reduction in conductivity [6-9].
To increase strength and electrical conductivity of Al-Mg-Si alloys, researchers have made a lot of efforts [10-12]. Karabay [10] designed a modification method, combining the AlB2 addition with artificial aging treatment, to promote the concurrent enhancements of the strength and electrical conductivity of 6201 alloy. Khangholi et al. [11] proposed a strategy for manufacturing Al-Mg-Si alloy, with a superior strength of 369 MPa and an acceptable conductivity of 53% IACS, by combining the natural aging with pre-aging treatment. Zheng et al. [12] found that it is a feasible method to improve the mechanical properties and electrical conductivity of Al-Mg-Si alloys by combining trace Ca, Mn addition with solution and aging treatment. According to these studies, the improvement of electrical conductivity of Al-Mg-Si alloy mainly relies on subsequent heat treatment, while the mechanical properties of cast Al-Mg-Si alloy enhance at the expense of electrical conductivity [13].
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Hong-yu Xu, Hai-feng Jia, Ze-sheng Ji, Ming-liang Li, Han Yu, Bo Jiang, Ye Wang, Mao-liang Hu (2025). Effect of La content on microstructure, tensile properties, and electrical conductivity of cast Al-Mg-Si-xLa alloys. China Foundry. https://doi.org/10.1007/s41230-025-4101-6
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Frequently Asked Questions
What is the optimal La content for improving the properties of cast Al-Mg-Si alloy?
The optimal La content is 0.2 wt.%, which yields the best combination of tensile properties and electrical conductivity.
How does La addition affect the microstructure of Al-Mg-Si alloy?
La addition refines α-Al grains, promotes the formation of Mg2Si phase, and transforms the AlFeSi phase from continuous to discontinuous, leading to improved properties.
What are the improvements in mechanical and electrical properties with 0.2 wt.% La?
Compared to La-free alloy, ultimate tensile strength improves by 9.0%, yield strength by 15.8%, elongation by 70.3%, and electrical conductivity by 17.3%.
Does excessive La addition have a negative effect?
Yes, excessive La deteriorates the properties of Al-Mg-Si-xLa alloys, indicating that there is an optimal La concentration.
What is the significance of this research for conductor materials?
This research provides a method to simultaneously enhance strength and electrical conductivity of Al-Mg-Si alloys, which is crucial for lightweight conductor applications in power systems.
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