Morphologies of the transition region in dissimilar austenitic-ferritic welds

The morphology of the transition region in dissimilar austenitic-ferritic steel welds has been characterized using scanning and transmission electron microscopy and using energy-dispersive X-ray spectrometry. With increasing base metal carbon content, a martensite-like layer in the unmixed zone of this region diminishes or disappears, and a “sawtooth-like” morphology extends from the partially melted zone into the weld. The number of weld interfaces also changes with variation in carbon content, from the double austenite/martensite-like and martensite-like/ferrite interfaces to a single austenite/martensite-like one. These variations are attributed to the local melting range of the base metal, which depends upon the carbon content, cooling rate, and alloy element segregation.