Abstract
Tensile properties, impact value and fracture toughness of weld metals of Ti-5Al-2.5Sn (ELI) alloy were investigated by comparing them with those of base metal at cryogenic temperatures. Two kinds of welding atmosphere were applied for gas tungsten-arc welding. One is a high purity inert atmosphere using an improved shielding. The other is vacuum. The conclusions are summarized as follows:
(1) The contents of O and N in the weld metals welded in both atmospheres were less than those of the base metal.
(2) The tensile elongation, impact value and fracture toughness of the weld metals welded in both atmospheres were larger than those of the base metal at 4.2K. It is reasoned that the martensitic structure of weld metal can deform plastically more than the equiaxial structure of base metal at cryogenic temperatures.
(3) The 0.2% proof stress of the weld metal welded in a high purity inert atmosphere was small compared with that of the weld metal welded in vacuum. However, the tensile elongation, impact value and fracture toughness of the weld metal welded in a high purity inert atmosphere were nearly equal to those of the weld metal weled in vacuum at cryogenic temperatures.
