Evolution and formation of dissimilar metal interfaces in fusion welding
Fan Wu, T.F. Flint, Renan Medeiros Kindermann, M.J. Roy, Lu Feng Yang, Stuart Robertson, Zhaoxia Zhou, Michael Smith, Pratheek Shanthraj, Paul English, Robert Atwood, Wajira Mirihanage
Abstract
The evolving interface forms between two different liquids during dissimilar welding can critically influence the development of the as-solidified microstructure and determine the mechanical properties of the joint. To investigate the interface evolution mechanisms during arc welding, time-resolved X-radiography was employed. The observations reveal the formation of transient finger-like protrusions at the dissimilar liquid interface prior to a brief, quasi-steady state. The analysis of the experimental observations using the magneto-thermal-hydrodynamic numerical simulations confirms that the quasi-steady state involves the formation of a short-lived solid phase, which alters the regular mixing during the process. Analysis of the in-situ experimental observations elucidate the interactions between thermal, momentum, electromagnetic and compositional fields which determine mechanisms of formation of the liquid interface instabilities and the melt pool shape. Based on the analysis, we extended our study to offer practical enhancement for dissimilar welding through offsetting the heat source.