A functionally graded material from stainless steel 304 to Fe–40Al fabricated by dual wire arc additive manufacturing

In this study, gas tungsten arc welding (GTAW) based dual wire additive manufacturing (D-WAAM) is adopted to fabricate the functionally graded material (FGM) from stainless steel (SS) 304 to Fe–40Al, using SS 304 and aluminum alloy (AA) 1070 wires. The Al/Fe atomic ratio varies from 0 to 40 % by varying the ratio of the wire feed speeds of the SS and AA wires. The chemical composition, phases, microstructure, and mechanical properties of the FGM are investigated. The results showed that with the increase of Al content, microstructures evolve as follows: γ-Fe → γ-Fe + α-Fe → α-Fe → Fe3Al → FeAl. Cracks occur in FeAl region, caused by the high stress and the low plasticity. Dislocation walls prevent the large grains from slipping, leading to the loss of plasticity. The microhardness of SS 304 to Fe–40Al FGM ranges from 188HV0.5 to 558HV0.5. As Al content increases, the ultimate compressive strength decreases from 1820 MPa to 1061 MPa. The results on microstructure and mechanical properties provide guidance for the preparation of steel - aluminum alloy FGMs.