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Abstract

Weldments of high strength pipeline contains a number of phases depending upon the chemical composition & cooling conditions after the welding. The underlying work deals mainly with two weldment microstructures, acicular ferrite & proeutectoid ferrite, the former being most desirable since it is believed to enhance the strength. However, the co-existence of acicular ferrite with proeutectoid ferrite is found to trigger the occurrence of microcracks in the weldments. The mechanism responsible for microcracking is believed to be hydrogen embrittlement which occurs in susceptible microstructures under high stresses and high content of hydrogen from environment & welding process. In order to mitigate the presence of microcracks in weldments, hydrogen diffusion and embrittlement is being studied at the micromechanical scale in acicular ferrite & proeutectoid ferrite. Initial numerical results show that the hydrogen tend to accumulate at the interface region between two phases.