Forming with twisting is a promising and untraditional method for shaping articles. A feature of this working method is that during upsetting of a billet there are combined longitudinal compression and shear strains which are accomplished as a result of using a rotating tool. 17zis working scheme increases the intensity of plastic deformation within the volume of a billet which should cause changes in the structure and material properties both immediately after forming with twisting and during subsequent heat treatment, hz the present work the effect of forming with twisting on the structure, standard, and breakdown characteristics of tantalum mechanical properties is determined and a stead), is almost made of conditions for performing it which provide preparation of the minimum grain size with minimum strength and maximum ductility for tantalum.Some data about processes which occur during forming with twisting have been considered in [1, 2]. Studies in this work were carried out on specimens of high-purity tantalum. Deformation of cylindrical billets 50 mm in diameter and length was performed at room temperature. The final articles were disks with a thickness of 4, 6, 8, 25, and 32.5 mm. After cold plastic deformation specimens were annealed in a vacuum furnace at 1200, 1300, 1400, and 1500°C for 0.5h.Specimens for structural studies were disks cut by different schemes: in the case of forming without twisting the plane of the microsection was oriented through the thickness along the radius, but after forming with twisting it was oriented at an angle of 20 ° , i.e., over the tangent to the metal 'twist' angle, which made it possible to estimate the true sizes of deformed and recrystallized grains. Grain size was determined by means of an Epiquant automatic structure analyzer. Microhardness was measured in a Neophot-21 instrument with a load of 0.5 N according to GOST 9450-76 (not less than 30 measurements in each microsection).The results of measurements were treated statistically and the confidence ranges for microhardness values with a probability of 0.95 were determined.The standard and breakdown characteristics of mechanical properties [3][4][5][6] were determined with static tension of cylindrical specimens 3 mm in diameter according to GOST 1497-84 in an Instron machine. During testing a record was made of the load-deformation curve and it was replotted in a breakdown curve for true stress S-true strain e 1/2 from which the breakdown characteristics of mechanical properties were determined according to a procedure developed previously [7]. A study of the effect of the degree of deformation t on microhardness (H) and strength characteristics (af, a0. 2) for tantalum showed that they qualitatively change identically: with an increase in the level of deformation H, af, and o0. 2 increase steadily. The rate of increase in hardness with different levels of deformation varies. If e < 40%, then hardness increases significantly: from 210 to 240 H, but then with E -= 50% a sharp increase is observed up 340-350 H. Wi...
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