Microstructural characterization of welded zone for Fe3Al/Q235 fusion-bonded joint

The microstructural characterization of Fe3Al/Q235 welded zone were analysed to investigate the welding behavior of Fe3Al intermetallic. The results indicated that a crack-free Fe3Al/Q235 joint was obtained when Cr25–Ni13 alloy was adopted as the filler metal. The microstructure of the welded zone presented different morphology due to the severe fluctuation of Al, Ni, Mn and Cr elements near the fusion zone. The fish-bone like structures in Q235 side fusion zone were composed of α-Fe(Cr, Al, Ni) solid solutions. Fe3Al/Q235 joint fractured in the Fe3Al HAZ, and shear strength of 533.33 MPa was achieved. The fracture mode of Fe3Al side fracture surface was mainly transgranular cleavage, occured along [1 1 1] orientation on {1 1 0} planes. And the Q235 side fracture surface was in intergranular and quasi-cleavage mode. The phase relations of γ and α in Fe3Al side fusion zone, constituent of lower bainite in the weld and the Fe3Al ordered transformation in HAZ were also determined.