Modification and characterization of the Al concentration induced precipitate in the Fe3Al-based iron aluminide fabricated using the wire-arc additive manufacturing process

Abstract Fe3Al based alloys have been continuously attractive to the fossil energy industry due to the excellent high temperature oxidation resistance and strength, light weight and low materials cost. In recent years, to overcome the fabrication difficulty of Fe3Al based alloys and reduce the room temperature induced high manufacturing cost, the twin wire-arc additive manufacturing (WAAM) technique is invented. During the post-production heat treatment aiming to modify the as-fabricated microstructures, the Al concentration induced precipitates are reported in the previous research, which can effectively refine the initial large grains and weaken the WAAM induced microstructural anisotropy. Therefore, the further characterization on the precipitate is meaningful for the development of the innovative WAAM in the Fe3Al fabrication. In the present research, to further characterize such Al concentration induced precipitates and find the functioning mechanism on the material properties, the precipitates are modified using various heat treatments and subsequently characterized in detail using microscopies and room temperature tensile test. According to the results, the Al concentration induced precipitates are characterized as the long-range ordered D03 structured Fe3Al superlattice. And the generation of such superlattice precipitates in the Fe3Al matrix performs dislocation pinning effect thus improves the alloy strength. However, the strengthening by D03 superlattice precipitates cannot compensate the tensile property anisotropy, thus the grain refinement is still the key to break down the large columnar grains and further improve the mechanical properties.