Shanghai Jiao Tong University Stabilizes Fe3Al 3D Printing at 105–125 A

In a study published in China Welding (中国焊接：英文版), researchers from Shanghai Jiao Tong University and collaborating institutions analyzed the effect of deposition current on the microstructure and mechanical performance of Fe-30Al-0.3C-Si-Mn alloy fabricated via twin-wire directed energy deposition-arc (TW-DED-arc) sciencedirect.com中国焊接：英文版sciencedirect.comOpen source ↗. The team printed 50-layer laboratory samples using separate steel and aluminum wires fed simultaneously into a single molten pool at three current levels: 105 A, 115 A, and 125 A.

Microstructure and Carbide Evolution

Iron-aluminum alloys based on Fe₃Al are prone to room-temperature brittleness, and repeated thermal cycling during additive deposition typically destabilizes grain structure. During the TW-DED-arc process, in-situ Fe₃AlC₀.₅ carbide precipitates formed directly within the Fe₃Al matrix. Although higher deposition currents raised the molten pool temperature and total heat accumulation, the carbide particles promoted grain nucleation and restricted grain growth across all tested parameters. As current increased, the carbides enlarged and distributed continuously along grain boundaries, but average microhardness remained relatively stable.

Mechanical Properties and Anisotropy

Tensile testing demonstrated that the alloy's strength and directional anisotropy vary independently with current adjustments. At 115 A, the alloy achieved its highest tensile strengths of approximately 431 MPa in the horizontal direction and 327 MPa in the vertical direction. However, this condition also showed the largest difference between the two orientations. Increasing the current to 125 A reduced tensile anisotropy, though it did not yield higher overall tensile strength. The authors concluded that in-situ carbide formation expands the viable processing window for wire-arc additive manufacturing of iron aluminides.