Au-Fe alloy solidification and solid-state transformations

In order to better understand the microstructure that forms during laser welding of an 18 carat gold and an austenitic stainless steel, solidification of the Au-Fe binary analog has been studied using thermal analysis and interrupted Bridgman experiments. For a hypoperitectic composition, the formation of the primary phase, its coarsening and the peculiar macrosegregation associated with the large density difference between the elements have been studied. Just after the peritectic phase forms around the primary dendrites, continuous and discontinuous precipitation has been shown to occur as a result of the immiscibility of the two face-centered cubic phases below the peritectic temperature. Finally, the solid-state transformations associated with the eutectoid have been characterized. (C) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.