Small carbides, stable grains: How deposition current shapes iron-aluminum alloys fabricated by twin-wire directed energy deposition-arc

Iron-aluminum alloys are attractive for high-temperature applications because of their excellent oxidation resistance, relatively low density, and low cost. However, their inherent brittleness at room temperature poses significant challenges for manufacturing. While wire-based arc additive manufacturing offers a flexible fabrication route, repeated thermal cycles during layer-by-layer deposition can alter the grain structure and mechanical properties of the resulting alloy.

In a study published in the KeAi journal China Welding, researchers from Shanghai Jiao Tong University and collaborating institutions examined how deposition current affects the microstructure and mechanical properties of an iron-aluminum alloy. The findings underscore how Fe₃AlC_0.5 precipitates suppress grain growth and preserve microstructural stability across varying deposition currents, and further elucidate how current settings modulate tensile strength and anisotropy, providing guidance to optimize the TW-DED-arc process for Fe₃Al-based alloys.

Using twin-wire directed energy deposition-arc (TW-DED-arc), the team fabricated the alloy layer by layer by feeding separate steel and aluminum wires into a common molten pool. During deposition, Fe₃AlC_0.5 carbide precipitates formed in the alloy.

“These carbide particles play an important role in controlling grain growth during repeated heating,” says corresponding author Chen Shen. “We wanted to understand whether they could help maintain a stable microstructure when the deposition current changes.”

The researchers produced 50-layer deposits at three deposition currents—105, 115, and 125 A—and examined the temperature distribution, microstructure, and mechanical properties of the resulting alloys.

“As deposition current increased, the molten pool reached higher temperatures, and the carbide precipitates grew larger and became more continuously distributed along grain boundaries,” shares Shen. “Despite these changes, the precipitates helped restrict grain growth, keeping the microstructure relatively stable. Average microhardness also varied little across the three conditions.”

Tensile testing, however, revealed a trade-off between strength and anisotropy. “At 115 A, the alloy achieved its highest tensile strengths—approximately 431 MPa in the horizontal direction and 327 MPa in the vertical direction—but also showed the greatest difference between the two directions. Increasing the current to 125 A reduced this difference, although it did not further improve tensile strength,” says Shen.

Notably, the highest strength and the smallest difference between testing directions were achieved at different currents. “This highlights the importance of balancing mechanical properties when selecting deposition parameters,” says Shen.

Contact the Author: 

Chen Shen, Shanghai Key Lab of Materials Laser Processing and Modification, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China. Email: cshen486@sjtu.edu.cn

Funder:

This research was supported by the Fundamental Research Funds for the Central Universities and Institute of Marine Equipment Fundamental Research; the Shanghai Rising-Star Program (No. 23QA1404700); the National Key Research and Development Program of China (No. 2024YFB4607101); the National Natural Science Foundation of China (Nos. 52505409, 52475384 and 51901136); the Oceanic Interdisciplinary Program of Shanghai Jiao Tong University (No. SL2021MS013); and the China Postdoctoral Science Foundation (No. 2024M761963).

Conflict of interest:

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

See the article:

Wang Li, Shen Chen, Li Yuchen, Zhang Yuelong, Zhang Peilei, Wang Zhiyuan, Ding Yuhan, Zhou Wenlu, Wu Kanglong, Ruan Gang, Li Fang. Effect of deposition current on Fe₃AlC_0.5 precipitation in Fe₃Al alloy fabricated via twin-wire directed energy deposition-arc process. China Welding, 2026; 35(3): 100073. https://doi.org/10.1016/j.cwe.2026.100073.