Effect of in-situ generated Fe3AlC0.5 on the microstructure and mechanical property of twin-wire directed energy deposition-arc fabricated Fe3Al based iron aluminide

Fe3Al-based iron aluminide alloys are known for their satisfactory resistance to corrosion, oxidation, and sulfidation at both ambient and elevated temperatures. However, the brittleness induced by the intermetallic nature of these alloys at room temperature significantly increases the manufacturing costs. To address this issue, a recent innovation called twin-wire directed energy deposition-arc (TW-DED-arc) technique has been developed to fabricate binary Fe3Al alloys with enhanced flexibility and cost-effectiveness. Building upon the feasibility validation of this technique, the present research aims to improve mechanical properties of TW-DED-arc fabricated Fe30Al alloy by in-situ generation of Fe3AlC0.5 precipitates within Fe3Al matrix. The experimental results demonstrate the successful production of the target Fe-30Al-0.3C-1Si-1Mn alloy. The reinforcement Fe3AlC0.5 precipitates exhibit good adherence to Fe3Al matrix, effectively increasing the tensile strength by nearly 15%. During tensile fracture, Fe3AlC0.5 precipitates are observed to obstruct crack propagation. Higher magnification characterization reveals clear dislocation entanglement occurring at Fe3AlC0.5 precipitate, confirming this phenomenon. Furthermore, preferential precipitation of Fe3AlC0.5 at grain boundaries induces clean areas adjacent to the grain boundaries. This has a dual effect: strengthening the grain boundaries and guiding crack propagations.