Microstructure, Residual Stresses, Texture, and Mechanical Properties of a Welded Joint in Vt1-0 Alloy Sheets

The grain structure, microstrain distribution, crystallographic texture and residual stresses in a CO2 laser welded joint of VT1-0 alloy sheets (technical titanium) are studied by EBSD and X-ray diffraction analysis. The mechanical properties of the welded joint are determined. It is shown that the weld structure is represented by differently directed large laths of the α-phase. The metal in the heat-affected zones is characterized by a mixed structure resulting from the polymorphic β→α transformation in the form of packets of secondary α-phase plates near the weld and polyhedral α-grains near the base metal. Multicomponent textures have been detected in all the zones of the welded joint. This creates prerequisites for decreased anisotropy of strength properties, which is typical of hexagonal crystals. The strength of the welded joint proves to be significantly higher than that of the base metal; namely, the ultimate strength of the joint is 660 MPa, and that of the base material is 500 MPa. The heat-affected zone is the most deformed zone in the welded joint, the share of deformed grains reaches 44%, and residual stresses do not exceed 10% of the yield strength.