Dissimilar laser welding of AISI 316L stainless steel to Ti6-Al4-6V alloy via pure vanadium interlayer

Successful continuous laser joining of AISI 316L stainless steel with Ti6Al4V titanium alloy through pure vanadium interlayer has been performed. Three welding configurations were tested: one-pass welding involving all three materials and two pass and double spot welding involving creation of two melted zones separated by remaining solid vanadium. For the most relevant welds, the investigation of microstructure, phase content and mechanical properties has been carried out. In case of formation of a single melted zone, the insertion of steel elements into V-based solid solution embrittles the weld. In case of creation of two separated melted zones, the mechanical resistance of the junction is determined by annealing of remaining vanadium interlayer, which can be witnessed by observing the increase of grain size and decrease of UTS. The two pass configuration allows attain highest mechanical resistance: 367 MPa or 92% of UTS of annealed vanadium. Double spot configuration produces excessive heat supply to vanadium interlayer, which results in important decrease of tensile strength down to 72% of UTS of annealed vanadium. It was found that undesirable a phase which forms between Fe and V is not created during the laser welding process because of high cooling rates. However, the zones whose composition corresponds to a homogeneity range are crack-susceptible, so the best choice is to reduce the V content in steel/vanadium melted zone below a phase formation limit. In the same time, the proportion between V and Ti in Ti6Al4V/vanadium melted zones does not influence mechanical properties as these elements form ideal solid solution. (C) 2014 Elsevier B.V. All rights reserved.