Using explosion welding for producing multicomponent active brazing alloys

Abstract

Active eutectic brazing alloys based on certain refractory metals are produced by melting in vacuum arc or electron-beam systems with subsequent rolling of ingots into foil or by electroplating of components on titanium foil. A large number of promising brazing alloys can be produced by conventional methods because of the high hardness and brittleness of alloys or because of the need for vacuum welding sheets of refractory metals produced by hot rolling.In this work, the authors propose a technology of producing active multicomponent brazing alloys of the Ti-Nb-V, Zr-Ti-V-Fe and V-Pd-Nb, Cu-Ni-V-Ti-Zr and Fe-V-Nb systems, including explosion welding the components of the brazing alloy with the production of multilayer blanks with high strength of the joints in the layers, cold rolling of the blanks to the design thickness with intermediate 'softening' heat treatment, and subsequent diffusion annealing for equalising the chemical composition in the thickness of the brazing alloy.To decrease the nonuniformity of layer deformation and minimise the deflection of welded and rolled sheets, investigations were carried out using a symmetric system of composition of the packets.The initial thickness of the sheets-components was calculated taking into account the required chemical composition of the brazing alloy, density and dimensions of the refractory elements used. The thickness of the interlayers was varied from 0.1 to 3.0 mm, and the thickness of the welded packets from 3.4 to 11 mm. The optimum welding conditions and absence of 'dangerous' heterogeneities in the form of brittle intermetallic and chemical compounds at the layer boundaries was ensured by rational alternation of the layers of the metals taking into account their initial thickness. In particular, it was taken into account that Ti with V and Zr, and also V with Fe and Nb form a continuous series of solid solutions. The alloys of the Cu-V system are characterised only by the formation of limited solid solutions with low hardness, high-strength and ductility. The compounds of Cu and Ni with Ti, Nb with Pd and Fe are characterised by the limited initial solubility and form, at specific concentrations, intermetallic compounds with high hardness and brittleness. The hardness of the intermetallic compounds of the elements with similar chemical properties (Fe-Nb) is slightly lower at a specific ductility. 1 Removal of the powerful effect on the intermetallic compounds was achieved by selecting the optimum conditions of welding and using equipment with a given rigidity. Examples of the distribution of layers in the explosion-welded multilayer blanks of the brazing alloys are presented in Fig. 1.In the conventional methods of welding multilayered packets of metals and alloys with a thickness smaller than 1 mm, welded joints often contain defects in the form of bubbles, lack of fusion and fracture of the upper layers. 2 To protect against the nonstationary nature of detonation of the explosive substance (ES) and perturbations in the explosion products, experiments...

On Deformation Powers of the Explosion Welded and Rolled Titanium-Aluminium Composite

“…3 b) in the whole examined range of deformation high-rise deformation εlayer of the aluminium layers has a linear dependence on the magnitudes of the compression of the composite and is approximately equal to them unlike cold rolling, when εlayer has "a bend" with compression of 12 %. Maximum altitude of high-rise deformation equal to 34% is observed in the compression of the composite of 34.5 % [16][17][18].…”

“…In cold rolling (Fig. 3 a) and the reduction to 10 %, AD1 and AMg6 layers are mainly deformed, the height deformation ε layer of which increases to 20.6 % [15]. The thickness of the titanium varies slightly, no more than 3 %.…”

“…Thus, according to [8] the greatest ductility of aluminum polycrystals is observed at temperature of 450-500 °C because it becomes possible to slide on the plane of the octahedron and the cube plane (at lower temperatures the slip plane of the octahedron is difficult and ductility of aluminum polycrystals is markedly reduced). In this case, the destruction of composite connections is not observed, since the conditions of deformation allow to restore the ties similar to the rolling welding process [9][10][11].…”

Relaxation Processes in Ti-Al Composite Material after Rolling

“…The measurement of the deflection was carried out using a flat head with a scale division of 0.002 mm on the basis of 160 mm. From the graph it is seen that the deflection has been decreasing for 7 days by ≈ 0.5 % in relation to the initial one and has amounted from 97.125 mm to 99.200 mm after warm rolling [15][16][17]. The data obtained show that at small deformations the time of reducing internal stresses in titanium-aluminum CM after removal of the load to a level that ensures stability of the form can amount to hundreds of hours.…”

“…The occurrence in various parts of the frame of elastic or plastic deformations can be explained by the work of composite elements under load. The removal of the applied load leads to the development of relaxation processes, caused by the intention of a material to return to equilibrium [7][8][9][10].…”