Microstructure characteristics of Fe₃Al/18-8 diffusion welded joint

Fe₃Al intermetallic and 18-8 stainless steel were vacuum diffusion welded and an obvious Fe₃Al/18-8 diffusion welded joint with three reaction layers was formed. Microstructure and phase structure of the joint were researched by means of scanning electron microscope, X-ray diffractometry and transmission electron microscope. The results indicate that shear strength of the Fe₃Al/18-8 diffusion welded joint which was obtained at 1 040℃ for 60 min with a pressure of 15 MPa is up to 226 MPa. And there are FeAl, Fe₃Al, Ni₃Al phases and α-Fe (Al) solid solution from Fe₃Al to 18-8 in the joint. The peak microhardness was measured to be 610 HM and there were no brittle phases such as FeAl₂ (820 HM), Fe₂Al₅ (990 HM), FeAl₃ (1030 HM).