OBRABOTKAMETALLOV Vol. 25 No. 2 2023 technology A variety of technologies for obtaining semi-finished products and rheological features of powdered titanium leads to the need for preliminary calculations to develop specific technical devices for its implementation. Reliable estimation of the energy-power parameters of the process and prediction of the porosity of pressed materials remains an important issue for the study of the ECAP semicontinuous process up to now. This in turn is associated with the need to develop sufficiently accurate, reliable, and simple for practical application mathematical models. The work aims to develop a model of the process of semicontinuous ECAP of titanium-containing raw materials to improve the technological processes of manufacturing blanks and products. To achieve this aim, it is necessary to determine the scheme of ECAP, a statistically admissible loading scheme for a severely deformed layer, and a kinematically admissible flow scheme for a plastically compressible medium in the layer, construct a system of equations, and compare the solution obtained with the developed system of equations with the finite element solution. Materials and methods The object of the study is the process of semicontinuous ECAP of an axisymmetric porous briquette (ϑb – initial porosity) of titanium sponge in the channel of the mold, which has an input part 6 and, crossing it at an angle 2α, output part 5 (fig. 1). The length of the briquette in the inlet and outlet parts of the channel at the current time are L1 and L2, respectively; Lb – the original length of the briquette, dl – the movement of the working plunger 1; D – the diameter of the channel. Plunger 1 creates pressure P1 on the briquette. The device also contains a plunger 2 to create counter-pressure (pressure P2 that prevents the flow of the deformed material from the mold channel). Plunger 2 is used in the first pressing cycle. In the second and subsequent cycles, the backpressure creates the discard 4 of the previous cycle. The flow of the deformed material in the mold channel is prevented by frictional forces on the surface of the extruded blank. Angular pressing provides severe plastic shear deformations in a thin layer located in the vicinity of section A–B (fig. 1) and separating the inlet I and outlet II parts of the mold channel. In this case, as a result of triaxial compression and intense shear deformation in layer A–B, the porosity of the titanium sponge decreases. In the input part 6 of the mold, the deformable material experiences a stressed state, similar to the usual pressing of a plastically compressible mass in a closed mold [26, 27]. Powdered sponge titanium of the TG-100 grade (composition complies with GOST 17747-79) (fig. 2) without additional processing (sieving, secondary fine dividing, purification, etc.) was used as a material for the study. It was assumed that the titanium sponge material was pre-compacted by double-sided pressing to briquettes with a relative porosity of ϑb = 0.4. The briquette material was considered to be homogeneous from the statistical viewpoint. Results and discussion Each ECAP cycle has two stages. In the first stage, the material to be processed in part II of the mold channel is not deformed; in part I, uniaxial compression of the porous mass takes place. Movement dl of plunger 1 leads to the Fig. 1. Scheme of equal-channel angular pressing: 1 – punch creating working pressure; 2 – punch for back pressure; 3 – part of the extruded blank; 4 – pressed part of the blank; 5, 6 – parts of the a pressing tool with output II and input I channels
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