Gamma (γ) phase transformation in pulsed GTAW weld metal of duplex stainless steel

The cooling rate and large undercooling significantly affect the fusion zone microstructure in pulsed GTAW weldment under the same heat input condition. The weld pool solidified at fast cooling rate about 139 °C/s superimposed a relative amount of undercooling has a desired higher γ content of about 37 vol.% without tradition nitrogen addition or post-weld heat treatment. The final structure of the pulsed weld metal at 7 °C plate consists of a great amount of desirable intra-granular austenite γ ′ 2 (IGA) inside the α grain matrix, besides Widmannstätten austenite γ ′ 2 (W) and grain boundary austenite γ2 (GBA). It results in the weldment with an uniform microhardness distribution and a homogeneous mechanical property.