Effect of electron beam welding on fracture behaviour of thick TC4-DT alloy

摘要

Fracture toughness of a damage tolerant Ti6Al4V (TC4-DT) alloy and its electron beam welded joint was investigated using compact tension specimens. Moreover, tensile test, microhardness test and microstructure examination were carried out. The result indicates that the weld metal is strength overmatching. The tensile strength and microhardness of the weld metal are higher than those of the base metal, but the ductility and the energy absorbed before fracture are lower. In addition, the fracture toughness K_(1c) of the base metal is relatively high. The fracture toughness of the weld metal decreases compared with the base metal. It is expected that the toughness reduction of the weld metal is mainly related to the as solidified coarse ? columnar grain structure containing martensite in comparison with the bimodal structure of the base metal. Moreover, fractographic observation shows that the fracture mode of both weld and base metals is found to be ductile.