Key Takeaways & Executive Findings
- •• Twin-roll strip casting successfully produces 2.4 mm thick Cu-12Fe alloy strips with a uniform Fe phase distribution and a 'sandwich structure'. • Direct cold rolling and aging (Process I) achieves 69.5% IACS electrical conductivity and 513 MPa tensile strength, balancing conductivity and strength. • Two-step processing (Process II) further improves tensile strength to 533 MPa while maintaining 66.3% IACS conductivity and enhanced magnetic properties. • The study demonstrates an efficient, low-cost route for producing high-performance Cu-Fe thin strips for electromagnetic shielding applications.
Abstract
The Cu-12Fe alloy has attracted significant attention due to its excellent electrical conductivity and electromagnetic shielding capability, high strength, cost-effectiveness, and recyclability. In the present work, the Cu-12Fe alloy strip with the thickness of 2.4 mm was successfully produced by twin-roll strip casting. The microstructure and properties of the Cu-12Fe alloy were tailored by cold rolling and aging treatment. The tensile strength of the as-cast strip is approximately 328 MPa and its elongation is 25%. The Fe phase randomly dispersed in the matrix, and the average size of Fe-rich phase is 2 μm. Besides, enrichment of Fe phase is observed in the central layer of the strip, results in the formation of the “sandwich structure”. Moreover, the as-cast strip of Cu-12Fe was directly cold-rolled from 2.4 to 0.12 mm. The directly cold-rolled sample after aging at 450 °C for 16 h (Process I) shows excellent electrical conductivity of 69.5% IACS, the tensile strength and elongation are 513 MPa and 3.8%, the saturation magnetic flux density is 20.1 emu·g-1, and the coercive force is 25.2 Oe. In Process II, the as-cast strip firstly cold-rolled to 1.2 mm, then aged at 500 °C for 1.5 h, followed by cold rolling to 0.12 mm, finally aged at 450 °C for 16 h. The sample after Process II shows the electrical conductivity of 66.3% IACS, the tensile strength of 533 MPa, an elongation of 3.5%, saturation magnetic flux density of 21.4 emu·g-1, and the coercive force of 22.3 Oe.
1. Introduction
Cu-Fe alloys have attracted great attention due to their easy processability, low cost, excellent conductivity, and recyclability [1-2]. These alloys are widely applied in various industrial fields, such as aerospace, automotive connectors, mobile terminals, and medical devices like CT and MRI scanners, where they serve as essential shielding materials [3-5]. By precisely adjusting the fraction, size, and distribution of the α-Fe phase, Cu-Fe alloys can be granted exceptional mechanical properties, conductivity, and electromagnetic characteristics. The well-controlled Cu-Fe alloys exhibit superior electromagnetic wave shielding performance. Current advancements are focused on achieving a high content of uniformly distributed α-Fe phase to enhance the electrical and electromagnetic properties of Cu-Fe alloys. Further research and development efforts are crucial for refining the alloy microstructure to fulfill specific performance demands across a wide range of high-tech industries.
The Cu-Fe alloy system undergoes a transition to a metastable immiscible system when the concentration of dissolved Fe atoms in Cu exceeds 5%. In this condition, below the liquidus line, the alloy displays typical characteristics of a metastable immiscible system [6-7]. During solidification, a visible liquid phase separation and segregation occur that pose challenges in obtaining non-eutectic Fe phase particles with sizes less than or equal to 10 μm in the solidified structure. The limited solubility of Fe in Cu further complicates efforts to increase the proportion of a nanoscale Fe phase using conventional solidification processes and heat treatments. Alternative forming processes, such as mechanical alloying, micro/small melt pool construction (e.g., vacuum consumption and 3D printing), and microgravity solidification, have been explored. However, these methods often come with high costs and deliver low efficiency, and are unsuitable in the case of thin strip materials [8]. There is an urgent necessity to develop more efficient and economical methods for producing Cu-Fe alloys with enhanced properties, particularly with respect to thin strip applications.
Several methods are currently employed to address the challenges associated with the Cu-Fe alloy system. The control of solidification behavior involves increasing the solidification cooling rate and adjusting the starting temperature in order to manage the separation process of metastable liquid phase. This approach aims to achieve the control over phase distribution during solidification. Microalloying and unconventional preparation methods involve modifying the morphology and proportion of primary Fe-rich phases, providing alternative approaches to influence the microstructure of alloys. The control of Fe atom solubility in the matrix represents an additional strategy. The solidification of Cu-Fe alloys results in a dual-phase microstructure, where the Fe phase is primarily distributed in the Cu matrix [9]. The amount of Fe-rich phases generated during solidification and the solute Fe atoms present in the matrix play a significant role in determining the ultimate mechanical and electromagnetic properties. Achieving a uniform distribution of Fe phases across micrometer to nanometer scales is crucial for optimizing performance.
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Tian-mo Wu, Yuan-xiang Zhang, Shuai-jie Guo, Nuo-jin Wang, Jian Kang, Guo Yuan (2026). Evolution of microstructure and properties of Cu-12Fe alloys prepared by twin-roll strip casting. China Foundry. https://doi.org/10.1007/s41230-025-4045-x
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Frequently Asked Questions
What is the significance of twin-roll strip casting for Cu-Fe alloys?
Twin-roll strip casting offers an efficient and economical method to produce thin Cu-Fe alloy strips with refined microstructures, overcoming limitations of conventional solidification and alternative processes like mechanical alloying or 3D printing.
How does the 'sandwich structure' affect the properties of Cu-12Fe alloy?
The 'sandwich structure' refers to Fe phase enrichment in the central layer of the strip, which influences the mechanical and electromagnetic properties by providing a gradient in phase distribution, potentially enhancing strength and magnetic performance.
What are the optimal processing conditions for high electrical conductivity and strength?
Process I (direct cold rolling to 0.12 mm followed by aging at 450°C for 16 h) yields 69.5% IACS conductivity and 513 MPa tensile strength, while Process II (intermediate aging at 500°C) achieves higher strength (533 MPa) with slightly lower conductivity (66.3% IACS).
How does the Fe phase distribution influence electromagnetic shielding?
A uniform distribution of Fe phases at micrometer to nanometer scales enhances electromagnetic wave shielding by improving magnetic properties such as saturation magnetization and coercivity, as demonstrated by the measured values in the processed samples.
What are the potential applications of the Cu-12Fe alloy strips?
The Cu-12Fe alloy strips are suitable for aerospace, automotive connectors, mobile terminals, and medical devices like CT and MRI scanners, where they serve as essential electromagnetic shielding materials.
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