Localized tensile strain distribution and metallurgy of electron beam welded Ti-5Al-5V-5Mo-3Cr titanium alloys

The tensile properties, strain distribution, fracture mechanisms, and microstructure of electron beam welded Ti-5Al-5V-5Mo-3Cr (Ti-5553) in the as-welded condition were investigated in order to evaluate the weldability of the titanium alloy. Rolled sheets of Ti-5553 were electron beam welded perpendicular to the rolling direction and sub-size tensile specimens were machined from the sheets. Tensile tests were conducted in conjunction with the use of a non-contact 3D image correlation photogrammetry system, ARAMIS, to determine the as-welded tensile properties as well as localized strain in the vicinity of the weld zone. Microstructural examination showed the fusion zone and heat affected zones consisted of large grains of retained beta phase whereas the base metals consisted of a surrounding small beta grains containing dispersed alpha precipitates. Tensile tests revealed that elongation at fracture in the as-welded condition was comparable to un-welded Ti-5553 while also revealing that the tensile strength was lower. Hardness profiles across the welds showed a decrease in average hardness from the base metals to the fusion zone. The decrease in hardness can be attributed to the large grain size, retained beta phase, and loss of Al during welding. Fracture occurred in the weld zone and was primarily due to microvoid coalescence. These results indicate that Ti-5553 is readily weldable and displays reasonable properties in the as-welded condition. (C) 2012 Elsevier B.V. All rights reserved.