Microstructure and performance in diffusion-welded joints of Fe3Al/Q235 carbon steel

Fe3Al and Q235 carbon steel were joined successfully at 1080 °C for 60 min by vacuum diffusion welding technology. A Fe3Al/Q235 diffusion-welded joint was thus formed. The microstructure features in the Fe3Al/Q235 diffusion-welded joint were analyzed by a variety of characterization techniques such as scanning electron microscope (SEM) with energy-dispersive spectroscopy (EDS), electronic probe microanalysis (EPMA) and an X-ray diffractometer. The micro-hardness from Fe3Al to Q235 carbon steel was measured with a micro-sclerometer. The shear strength in the Fe3Al/Q235 diffusion-welded joint was evaluated with a strain and stress machine. The experimental results indicated that Al atom content decreases from 27 to 1% and Fe atom content increases from 73 to 96% from Fe3Al base metal to Q235 carbon steel. The micro-hardness was 420–200 HM and the shear strength was 71.4 MPa in the Fe3Al/Q235 joint. There were Fe3Al, α-Fe (Al) solid solution and FeAl in the Fe3Al/Q235 diffusion-welded joint without brittle phases and with high micro-hardness. Thus, the ideal Fe3Al/Q235 joint can be obtained, which will meet the requirement for engineering structures.