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The influence of the different process variables on the fracturetoughness of electron beam weldments carried out on a 17 mm thick plateof a Ti – 6 Al – 4V has been analyzed. The use of filler metal of similar anddissimilar chemical composition or unalloyed sheets of different thickness(0.25, 0.50 and 1 mm) prefixed in the joint have been investigated. When thewire used possessed a composition similar to the base material a significantcontent of brittle alpha prime martensite was observed. The presence of thisphase induced a decrease in the fracture toughness of the joint. However,when unalloyed filler metal was used a predominant acicular alpha phasemicrostructure was observed and higher toughness achieved. The use ofsheet filler metal leads to acicular alpha microstructures very similar tothose found in commercially purity titanium weldments and a markedimprovement in fracture toughness obtained. Even when tests were carriedout on specimens machined from clearly defective zones toughness valueswere similar to those measured in the sound weld metal zones producedwithout filler metal