OBRABOTKAMETALLOV technology Vol. 25 No. 2 2023 of SPD are known: high-pressure torsion [1], pack rolling [2], all-round forging [3], cyclic extrusion and compression, also called “hourglass pressing” [4], equal-channel angular pressing [5] and others. A detailed review of SPD methods was performed by R.Z. Valieev et al. [6] and V.M. Segal [7]. The desire to improve the performance of SPD processes has stimulated the development of various methods of continuous pressing. The methods of continuous pressing, which have found the widest application in industry, include conformal (forming of long-rolled metal by the method of continuous extrusion), Linex [8], and combined rolling-pressing [8–9]. The work of V.M. Segal [10] considered the theoretical aspects of the process that combines the methods of equal-channel angular pressing and conformals. SPD of powder and porous materials realizes a complex stress-strain state characterized by joint triaxial compression and shear [11]. The process of consolidation from pure aluminum powder by the method of equal-channel angular pressing with torsion is described in [5], where it is shown that reiteration of SPD makes it possible to accumulate structural changes in the material. This contributes to a more efficient closure of large structural defects, and also increases the number and size of areas of mechanical adhesion of particles due to the initiating effect of shear deformation. It was shown in [12] that SPD for porous titanium and a porous titanium-magnesium composite makes it possible to obtain an ultrafine-grained structure and good contact between particles. Of particular interest is the method of equal-channel angular pressing (ECAP) of powder and porous materials. It was shown in [13] that the use of ECAP of a metal powder makes it possible to obtain practically pore-free blanks with high hardness even after a single pressing. However, a particularly important advantage of ECAP is the possibility of consolidating powder and porous materials at lower temperatures compared to the temperature required in traditional powder metallurgy methods [14]. At the same time, it is of great practical interest to obtain semi-finished products from powdered raw materials of hard-to-deform and low-plastic alloys and metals, such as titanium, with uniform properties and minimal porosity. The reduction in the cost of titanium powder products directly depends on the reduction in the cost of production methods and pressure shaping of titanium powders. Of great interest are methods for the production of titanium powder, close in its physical and mechanical properties and morphology of individual particles to titanium sponge obtained by the traditional Kroll method. International Titanium Powder, L.C.C. (Cristal US Inc., USA) has developed a process for obtaining titanium powder (Armstrong process), suitable for the manufacture of essential components by powder metallurgy. Chen et al. [15] studied the process of cold compaction of Armstrong powders of the Ti-6Al-4V system. According to the data given in [16], this technology makes it possible to reduce the cost of manufacturing finished titanium products by at least two times. The authors of [17] presented an electrochemical method (Cambridge process) for the direct reduction of solid TiO2. The Rapid Plasma Quenching Process (Idaho Titanium Technologies, USA) is based on the use of high-temperature plasma energy and makes it possible to reduce the cost of high-quality titanium powders’ production [18]. In [19], a method for obtaining cheap titanium powder from a titanium sponge using the technology of self-propagating high-temperature synthesis (SHS) is proposed. The use of severe plastic deformation methods for these materials will make it possible to obtain high-density blanks without the use of traditional energy- and labor-intensive titanium production technology. It is worth noting that finely divided titanium sponge and powder compositions based on it are promising materials for the manufacturing powdered titanium products, which require high corrosion resistance, low weight and satisfactory strength properties at a low cost of raw materials. NORSK Titanium (Norway) has received twopatents for theproductionofweldingwiredirectly fromtitaniumsponge (Patent WO2011049465, Patent WO2012127426). In [20], the effect of combined treatment, including hydrogenation/hydrogen removal and rolling, on the structure and mechanical properties of sponge titanium plates pressed by a shock wave was studied. The authors of [21] showed the possibility of using a porous material based on titanium sponge granules in the production of implants for osseointegration. In [22], the process of uniaxial pressing of titanium sponge powder was investigated. In [23–25], the effect of hydrogen doping on the properties of briquettes made of sponge titanium by pressing was investigated.
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