Analysis of the microstructure and phase constitution of the Fe3Al/18-8 diffusion interface after re-heating

The existence of coarse precipitation blocked the diffusion of the atoms and caused the uneven distribution of elements at the Fe3Al/18-8 interface zone. Especially, the brittle precipitation could induce welding cracks directly. Consequently, it was one of the main factors that caused the failure of the joint. The Fe3Al/18-8 diffusion-bonded joint was re-heated and the precipitation and phase constitution of the interface were analysed by means of scanning electron microscope (SEM), energy dispersive spectrum (EDS) and X-ray diffraction (XRD). The results indicated that the precipitation became tiny and regular and distributed evenly due to re-heating. The brittle precipitation zone was liquified to become a smooth and homogeneous diffusion zone. There were no high-microhardness brittle phases such as FeAl2 and Fe2Al5 near the Fe3Al/18-8 diffusion interface after re-heating.