Heterogeneous pulsed Nd: YAG laser welding of tantalum with TA6V titanium alloy

The knowledge of heterogeneous welding of tantalum and titanium alloys still remains partial. With the use of pulsed YAG laser welding process, distortions can be minimised. However, we can notice several misunderstandings: firstly, an irregular laser/material interaction and secondly, a difficulty to obtain thermal effect expected into the melting zone according to joint design: butt or step joint. On a butt joint, we studied laser/matter interaction using a design of experiments. We observed no crack in the fusion and heat affected zones but we could point out a relation between the efficiency of laser/matter interaction and the spatial distribution of energy on each material. On the other joint design, the main difficulty is to control the amount of energy provided on TA6V directly by the laser beam and trough tantalum thanks to thermal conduction. An optimisation of the step joint design has to be done before beginning a specific metallurgical study of the welded zone. In the end, welding tantalum with TA6V titanium alloy is technologically difficult and induces complex thermal behaviours that could be responsible for lack of fusion and other defects on welds.