When no filler material is used during the welding of duplex stainless steels, the weld fusion zone and heat affected zone (HAZ) is heated to temperatures above the solvus temperature, and followed by a rapid cooling, showing a higher level of ferrite compared with the base metal. Different precipitates are found in the ferrite phase. These microstructural changes are observed when heat input is less than 2 MJ/m. However, for higher values, it has been found that the level of austenite increases in the weld bead and, in some case, the bead was almost completely transformed in an austenitic structure and free from any precipitation. Chemical composition of weld bead and morphology of precipitates formed at low heat input were examined by Scanning Electron Microscopy (SEM) linked to an EDX analyser. Effect of welding parameters on the distribution of austenite in the HAZ was also studied.