Microstructural Characterization of Welded Joint in Duplex Stainless Steel by Laser Continuous Heat Treatment

Microstructural characterization in fusion zone of the laser continuous heat treatment welded joint was investigated. The results showed that the martensite-like microstructure is the face centered cubic (FCC) crystal structure so that it can be identified as the secondary austenite. The dislocation is observed inside and outside the secondary austenite, whereas inclusion is not found in the vicinity of the secondary austenite. In the fusion zone, there is a kind of carbide precipitate which is identified as M23 C6 by the means of transmission electron microscope (TEM). The carbide precipitate is a representative mode of transformation, which can be generated by the eutectoid reaction. Furthermore, the formation mechanisms of the secondary austenite and chromium carbide are analyzed.