Effect of post-weld aging treatment on the precipitation and mechanical behavior of Fe-Ni based alloy weldment

Precipitation and mechanical behavior of Fe-Ni based alloy weldment in the post-weld aging condition were investigated in the present work. Microstructural analysis showed that an inhomogeneous distribution of γ' phase was present in the dendritic structure of fusion zone, exhibiting that γ' phase were precipitated in the interdendritic region while a γ' phase depletion zone was developed in the dendrite core. Cleavage of the dendritic-interdendritic boundaries could be found in the nail-head region by the combined effects of directional growth of dendrite and inhomogenous distribution of γ' phase in the dendritic structure during tensile test. Distinct differences in the hydrogen embrittlement susceptibility between the dendrite core and the interdendritic region led to a higher sensitivity to cleavage cracking in the hydrogen-precharged weldment.