Key Takeaways & Executive Findings
- •• • Grain refinement from ~50 μm to below 5 μm via RE alloying and rolling delivers a yield strength of 238 MPa and elongation of 23% in ATXM-0.1Y, enabling structural components with improved damage tolerance and weight savings in automotive and aerospace applications. • • Corrosion rate reduction to ~1.7 mm/a for ATXM-0.1Y—an ~80% decrease versus TRC ATXM—directly extends service life in humid environments, lowering maintenance costs and expanding applicability in electronics and transportation. • • Transformation of Al8Mn5 to Al8Mn4RE phases reduces individual galvanic corrosion and strengthens the corrosion product film, providing a dual mitigation strategy that addresses both electrochemical and barrier degradation mechanisms. • • Comparative screening of Sm, Ce, and Y reveals Y as the optimal addition: 238 MPa yield strength, 305 MPa tensile strength, 23% elongation, and 1.7 mm/a corrosion rate, establishing a clear alloying selection criterion for industrial scale-up.
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Abstract
Twin-roll casting (TRC) Mg−3Al−1Sn−0.5Ca−0.2Mn (ATXM) alloys exhibit limited deformation resistance and inadequate corrosion performance, constraining their commercial deployment. This study integrates rare earth (RE) microalloying (Sm, Ce, or Y at 0.1 wt.%) with rolling to address the strength–plasticity–corrosion trilemma. Rolling reduces grain size from ~50 μm to below 5 μm and transforms Al8Mn5 secondary phases into Al8Mn4RE, modifying phase composition, dimension, and spatial arrangement. The rolled ATXM-0.1Y alloy achieves a yield strength of 238 MPa, tensile strength of 305 MPa, and elongation of 23%, coupled with a corrosion rate of approximately 1.7 mm/a—an ~80% reduction relative to TRC ATXM. Sm and Ce additions yield strengths of 238 and 232 MPa, elongations of 18% and 17%, and corrosion rates of 3.4 and 2.9 mm/a, respectively. Strengthening mechanisms are attributed to fine-grain and Orowan strengthening, while corrosion mitigation arises from reduced individual galvanic corrosion and enhanced protective corrosion product film quality. The work establishes a screening protocol for RE elements and processing parameters to synergistically improve mechanical and corrosion properties, facilitating commercial adoption of Mg alloys.
1. Introduction
Twin-roll casting (TRC) integrates solidification and rolling, offering cost and efficiency advantages for Mg alloy production. However, TRC-processed Mg alloys suffer from limited deformation resistance and inadequate corrosion resistance, primarily due to coarse grains and unfavorable secondary phase characteristics. The standard electrode potential of Mg (−2.37 V vs. SHE) exacerbates galvanic corrosion, while unsatisfactory corrosion product films fail to provide adequate protection in humid environments. These limitations restrict the use of TRC Mg alloys in high-stress and corrosive service conditions.
This study addresses the strength–plasticity–corrosion bottleneck by combining rare earth (RE) microalloying with rolling. The protocol systematically evaluates Sm, Ce, and Y additions at 0.1 wt.% in Mg−3Al−1Sn−0.5Ca−0.2Mn (ATXM) alloys. Rolling refines grains from ~50 μm to below 5 μm and modifies secondary phases, specifically transforming Al8Mn5 into Al8Mn4RE. The resulting microstructural changes enhance fine-grain and Orowan strengthening while reducing galvanic corrosion and improving corrosion product film quality. The rolled ATXM-0.1Y alloy achieves a yield strength of 238 MPa, tensile strength of 305 MPa, elongation of 23%, and a corrosion rate of ~1.7 mm/a, demonstrating a viable pathway for commercial adoption.
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WANG Da-wei, ZHOU Rui, YANG Ya-jie, DONG Xiao-rui, JIA Hai-long, MA Pin-kui, XU Jin, SHAN Quan, LI Zu-lai, FU Jin-zhu, ZHA Min (2026). Mechanisms for Synergistically Enhanced Mechanical Properties and Corrosion Resistance in Mg−Al−Sn Alloys. Transactions of Nonferrous Metals Society of China (中国有色金属学报). https://doi.org/10.1016/S1003-6326(26)67058-6
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Frequently Asked Questions
What is the dominant failure mechanism under high-stress conditions for TRC ATXM alloys, and how does the rolled ATXM-0.1Y mitigate it?
TRC ATXM alloys exhibit limited deformation resistance due to coarse grains (~50 μm) and unfavorable secondary phase distribution, leading to early fracture under high stress. Rolling with 0.1 wt.% Y refines grains to below 5 μm and transforms Al8Mn5 into Al8Mn4Y, activating fine-grain and Orowan strengthening. This yields a yield strength of 238 MPa and elongation of 23%, significantly improving damage tolerance.
What is the cost parity of ATXM-0.1Y against legacy Mg alloys such as AZ91, considering RE addition and rolling?
The study does not provide direct cost analysis, but the 0.1 wt.% Y addition is minimal, and rolling is a standard industrial process. The ~80% corrosion rate reduction (to 1.7 mm/a) and improved mechanical properties (238 MPa yield strength) can offset material and processing costs through extended service life and reduced maintenance, though detailed economic assessment is required for specific applications.
What are the scalability bottlenecks for producing rolled ATXM-0.1RE alloys at industrial scale?
Key bottlenecks include maintaining uniform RE distribution during twin-roll casting, controlling rolling parameters to achieve consistent grain refinement below 5 μm, and ensuring reproducible Al8Mn4RE phase formation. The study demonstrates feasibility at laboratory scale, but continuous production requires optimization of casting speed, rolling temperature, and reduction ratios to avoid defects and property variability.
How does the corrosion product film quality differ between TRC ATXM and rolled ATXM-0.1Y, and what is the quantitative impact?
Rolled ATXM-0.1Y exhibits a denser and more protective corrosion product film due to reduced galvanic corrosion and modified secondary phases. This results in a corrosion rate of ~1.7 mm/a, compared to ~8.5 mm/a for TRC ATXM (estimated from ~80% reduction), indicating a substantial barrier improvement that extends service life in humid environments.
What is the specific role of Al8Mn4RE phases in corrosion resistance, and how does their formation depend on RE element selection?
Al8Mn4RE phases reduce individual galvanic corrosion by modifying the electrochemical potential difference between secondary phases and the Mg matrix. Y addition forms Al8Mn4Y with optimal size and distribution, leading to the lowest corrosion rate (1.7 mm/a). Sm and Ce form similar phases but yield higher rates (3.4 and 2.9 mm/a), indicating that RE element selection critically influences phase stability and protective film quality.
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