The formation of intermetallics in dissimilar Ti6Al4V/copper/AISI 316 L electron beam and Nd:YAG laser joints

The welds of titanium alloys with steels suffer from the brittleness of resulting intermetallic compounds. In present study, we report the feasibility of Ti6Al4V to stainless steel AISI 316L welding through pure copper interlayer carried out by electron beam and pulsed Nd:YAG laser. The nature and the localization of intermetallic phases in these welds have been studied by SEM, EDS, XRD and microhardness measurements. The simplified scenario of weld formation has been proposed in order to understand the mechanism of weld formation and to explain the way local phase content determines the mechanical properties. It can be concluded that the insertion of 500 mu m pure copper interlayer allows reducing but not suppressing the formation of brittle Ti-Fe and Ti-Cr-based phases. The local accumulation of Cu-Ti and Cu-Fe-Ti-based phases is less detrimental to the strength of the welds, which makes joining possible. The thickness of brittle regions is reduced due to short lifetime of the melt and compensated by the ductilizing effect of copper. The tensile strength of the welds is limited by brittleness of CuTi2 + FeTi + alpha-Ti layer situated next to the solid Ti6Al4V. (C) 2011 Elsevier Ltd. All rights reserved.