Electron beam welding of titanium aluminides - Influence of the welding parameters on the weld seam and microstructure

This paper gives an account of research which has been carried out on electron-beam welded specimens made of high-Niobium gamma/alpha(2)-titanium aluminides in comparison to gamma-titanium aluminides. The high niobium content of this alloy (5-8%) has a positive effect on the strength and the creep resistance and also on the oxidation resistance. The standard welding parameters weld speed and beam current and also additional beam oscillation have been used for the determination of factors which will effect the solidification morphology and structural constitution since those, in return, exert influence on the high cracking susceptibility of the alloy. In order to reduce the critical cooling rate, preheating which has a positive effect on crack formation has, in addition, been applied. In a direct comparison of both alloys, micrographs and electron beam micro-analyses of the developing weld structure and of the heat affected zone, the effects of the beam parameters on both alloys have been established.