Key Takeaways & Executive Findings
- •• Mg/Si alloying combined with T6 treatment significantly enhances the strength of cast Al-2.3Fe alloy while maintaining high electrical conductivity, achieving a UTS of 309.5 MPa and EC of 52.5% IACS. • Optimizing the Mg/Si ratio to 0.56 balances solid solubility and precipitation, minimizing conductivity loss and maximizing mechanical properties. • The addition of Mg and Si alters the solidification path, refining second-phase morphology and phase constitution, which improves aging response. • The developed Al-2.3Fe-Mg-Si alloy offers a promising alternative to Cu conductors for automotive motor rotors, meeting the demanding requirements of high strength and conductivity.
Abstract
The Al-2.3Fe eutectic alloy is regarded as a promising substitute for Cu conductors in automotive motors owing to its excellent castability and low resistivity. However, its application is restricted by the mutually exclusive relationship between electrical conductivity and mechanical strength. The microstructure and mechanical properties of Al-2.3Fe alloy were modified through Mg/Si alloying combined with T6 heat treatment in this work, leading to the development of a high-performance cast Al-2.3Fe-Mg-Si alloy. In the Al-2.3Fe-0.40Mg-0.72Si (Mg/Si=0.56) alloy subjected to T6 treatment, an electrical conductivity of (52.5±0.6)% IACS is achieved, while the ultimate tensile strength is significantly enhanced to 309.5±5.6 MPa. The addition of Mg and Si brings about marked changes in the solidification process of the Al-2.3Fe alloy, resulting in considerable variations in both the morphology of the second phase and its phase constitution. The aging behavior of the alloy is governed by second phase and solid solubility. Through optimization of the Mg/Si ratio, the aging response can be effectively enhanced. At the ratio of Mg/Si=0.56, a balance is achieved between solid solubility and precipitation, while simultaneously minimizing the detrimental impact on electrical conductivity and reaching the best mechanical properties and electrical conductivity in peak-aged Al-2.3Fe-xMg-ySi alloy. This work providing valuable insights for developing advanced conductor materials.
1. Introduction
In recent years, with the advancement of the country's “dual-carbon” goal and the implementation of energy conservation and emission reduction policies, new energy vehicles, due to their low energy consumption (11.9 kWh/100 km), are gradually becoming the main alternative to fuel vehicles (45 kWh/100 km) [1, 2]. As a core component, the performance of the motor directly affects the power output and energy efficiency of the vehicle [3]. With the advancement of drive technology, rotational velocity of the motor rotor is constantly increasing, and the maximum speed can reach 20,000 rpm. This puts forward higher requirements for the strength, electrical conductivity (EC), and heat resistance of the rotor material.
Aluminum alloys, with high specific strength, low cost, and excellent electrical and thermal conductivity, have become the primary choice for rotor materials [4-6]. However, existing commercial aluminum alloy systems have difficulty meeting the requirements of high conductivity and high strength simultaneously. For example, the ultimate tensile strength (UTS) of commercial A356 alloy is approximately 250 MPa, but its EC is less than 40% IACS [7-10]. The EC of commercial 1070 alloy reaches up to 60% IACS, yet its strength is lower than 30 MPa [11]. The rotor material of the drive motor for new energy vehicles needs to maintain an EC of not less than 50% IACS and a yield strength of not less than 60 MPa at a service working temperature of 180 °C [12]. Therefore, the development of new Al alloys with both high EC and high strength has become an urgent problem to be solved.
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Yu-fei Zhang, Xi-long Luo, Zheng-hao Shao, Qun Luo, Bin Hu, Hong-zhou Lu, Qian Li (2026). Achieving optimal strength-conductivity balance in cast Al-2.3Fe-Mg-Si alloys via Mg/Si ratio regulation. China Foundry. https://doi.org/10.1007/s41230-026-5183-5
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Frequently Asked Questions
What is the main challenge in developing Al-Fe alloys for automotive motor rotors?
The main challenge is achieving a balance between high electrical conductivity and high mechanical strength, as these properties are often mutually exclusive in aluminum alloys.
How does Mg/Si alloying improve the performance of Al-2.3Fe alloy?
Mg/Si alloying combined with T6 heat treatment modifies the microstructure, refining second-phase morphology and phase constitution, which enhances the aging response and leads to improved strength while maintaining good electrical conductivity.
What is the optimal Mg/Si ratio for the Al-2.3Fe-Mg-Si alloy?
The optimal Mg/Si ratio is 0.56, which achieves a balance between solid solubility and precipitation, minimizing the detrimental impact on electrical conductivity and maximizing mechanical properties.
What are the key properties of the developed Al-2.3Fe-Mg-Si alloy?
The alloy exhibits an electrical conductivity of (52.5±0.6)% IACS and an ultimate tensile strength of 309.5±5.6 MPa after T6 treatment, making it a promising candidate for high-performance conductor applications.
Why is this alloy considered a promising substitute for copper conductors?
Due to its excellent castability, low resistivity, and now improved strength and conductivity balance, it offers a cost-effective and lightweight alternative to copper for automotive motor rotors.
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