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A method for pressure welding of cylindrical workpieces in the solid state of an aluminum–zinc alloy in a vacuum at a temperature of 250°C under conditions of low-temperature superplasticity is developed. Tensile tests showed that the strength of the welding joints is 90–95% of the ultimate tensile strength of the base material. [ABSTRACT FROM AUTHOR]

The influence of low-temperature superplastic deformation on the structural-phase state and mechanical properties of ultrafine-grained titanium alloy VT22 has been studied at room temperature. It is shown that the tensile strain of alloy samples has an insignificant effect on their mechanical properties at strain rates of 2·10–3 and 6.9·1–3 s–1 and a temperature of 823 K. It has been established that this effect is due to the preservation of the ultra fine grade (UFG) structural-phase state of the alloy during superplastic deformation formed as a result of its processing by the method of all-round pressing. An increase in the deformation temperature to 873 K at the same strain rates leads to a decrease in the mechanical properties of the alloy by about 6–8%. [ABSTRACT FROM AUTHOR]

A new approach to solid-state pressure welding of Zn–22% Al aluminum–zinc alloy in vacuum at a temperature of 250°C under conditions of low-temperature superplasticity is proposed. An ultrafine equi-axial structure with an average size of both phases was obtained by annealing in an oven at 350°C followed by quenching in water. This treatment produces stable ultrafine grains of about 0.65 μm with a uniform distribution of Zn and Al grains. When welding high-height billets with pressure, barrel-like properties appear on the side surface of welded materials. It is shown that the sizing of the mold for pressure welding of cylindrical billets makes it possible to influence development of local flow and to provide the most favorable conditions of deformation by optimizing energy consumption for deformation in the zone of the welded joint. As a result of heating and precipitation, a joint superplastic deformation occurs and the main deformation is localized in the region of formation of the solid-phase joint, while most of the blanks are slightly deformed. Oxide films on the surfaces to be joined are broken by extrusion and removed by superplastic deformation in radial directions, and a new oxide-free layer appears on the surface of the workpieces to be welded. The welded area is formed due to the occurrence of metal bonds between the juvenile contacting surfaces of the welded workpieces. Mechanical tensile tests showed that the strength of the solid-phase joints was 90–95% of the ultimate strength of the base material. [ABSTRACT FROM AUTHOR]

The structure and mechanical properties of the titanium alloy VT6 joint diffusion welded in vacuum at 820°C using an ultrafine-grained interlayer made of alloy VT22 in are studied after annealing at 900°C for 2 h. The heating-induced activation of diffusion processes is found to halve the number of micropores in the weld zone and to increase the tensile strength of the welded joint from 975 to 1108 MPa. The impact toughness of this joint after heat treatment corresponds to the initial impact toughness of the VT6 alloy. [ABSTRACT FROM AUTHOR]