Advanced characterization of heterogeneous arc welds using micro tensile tests and a two-stage strain hardening ('UGent') model

Arc welds and their heat affected zones are heterogeneous due to the nature of the involved welding process. Nevertheless, the complexity of weld integrity assessments is often reduced by assuming homogeneous properties for weld metal and for heat affected zone metal. To evaluate this simplification, the authors aim to examine the effect of weld metal heterogeneity on the structural integrity of welded connections. As a part of this examination, the presented paper describes the characterization of heterogeneity in a selection of multi-pass steel arc welds. An extensive set of micro tensile tests has been performed. Significant differences in strength and yield-to-tensile ratio are observed between as-deposited and grain refined weld metal. Stress–strain curves of local microstructures are defined using a stress–strain model that describes two-stage strain hardening. This approach allows to quantify variations in stress–strain curve shape. The magnitude of the observed heterogeneity justifies the incentive for further research in the field of weld metal heterogeneity. - Highlights: • Micro tensile and hardness tests reveal significant heterogeneity in arc welds. • Grain refined microstructures appear stronger than as-deposited microstructures. • FITNET correctly describes decrease of strain hardening as strength increases. • UGent stress–strain model simultaneously describes early and advanced yielding. • UGent model is significantly more accurate than the Ramberg–Osgood model