Product Code: ICAL09_401

Statistical Analysis of Low Porosity Laser Welding of Ti Alloys using a Directed Gas Jet
Authors:
Jonathan Blackburn, The University of Manchester; Manchester Great Britain
Chris Allen, TWI Ltd; Cambridge Great Britain
Paul Hilton, TWI Ltd; Cambridge Great Britain
Lin Li, The University of Manchester; Manchester Great Britain
Presented at ICALEO 2009

Titanium alloys are increasingly utilized in the aerospace sector as a result of their high specific strength, fatigue performance and corrosion resistance. It has been reported previously by the authors that high quality, low internal porosity content welds can be made in titanium alloys using near-infrared laser beams. In general, when laser welding titanium alloys, a jet of inert gas directed at the region of the laser beam/material surface interaction point, is utilised to achieve the weld quality required. This paper presents the results of a three stage statistical approach to determine the optimum position and flow rate of this directed gas jet, with respect to the resulting subsurface weld metal porosity and weld profile, for autogenous Nd:YAG laser welding of 3.2mm thick Ti-2.5Cu and Ti-6Al-4V. High speed imaging and spectroscopic analysis of the welding process has shown that, once correctly set-up, the directed inert gas jet disperses the formation of excited metal vapour above the keyhole and also significantly changes the hydrodynamic behaviour of the weld pool.