Problem Statement (Relevance): The paper describes some features and prospective benefits of deformation by methods of drawing with shear (SD) and high pressure torsion (HPT) in a temperature range of dynamic strain aging (DSA) effect, which allow receiving a high complex of physical and mechanical properties. Objectives: The study aims to investigate and analyze features of the structure formation with the combined application of severe plastic deformation (SPD) and the DSA effect during deformation by drawing with shear and high pressure torsion, to establish patterns of the gradient structure formation. Methods Applied: 1. Computer simulation in Deform 3D software to investigate the stress-strain state on materials with various types of a crystalline lattice: copper grade M1 (FCC), Steel 10 (BCC) and titanium VT1-0 (HCP) and a further comparison with experimental results. 2. Microhardness measurement 3. Scanning and transmission electron microscopy. Originality: This research resulted in investigation of the combined effect of the DSA effect and SPD on the gradient structure formation and mechanical properties of metals with various crystalline lattices. Findings: the paper presents the results of the study of the structure formation during non-monotonous plastic deformation of the alloys (steel 10, copper and titanium) with various crystalline lattice types by SD, as well as ECAP and HPT of low-carbon steel in the temperature range of the DSA effect. Deformation mechanisms and features of the deformation behavior on a mesoscopic scale under various deformation treatment modes are analyzed. The temperature range of the DSA effect in steel 10 under ECAP and the fact of the gradient structure formation under HPT are established. Practical Relevance: The study helped to obtain data that can be used to choose the optimal deformation treatment mode with the DSA effect.

The paper presents the results of computer modeling and experimental studies of the parameters of the stress-strain state and structure of the material during deformation by the method of alternating multi-cycle bending of a long-length workpiece (bar, wire rod) around a rotating roller in free and constrained conditions. The material for the study was long-length rods of low alloyed bronze for electrical applications -the Cu-0.5 %Cr alloy. It was found that after 4 bending cycles with the workpiece turning through 90° around the longitudinal axis, a gradient field of accumulated strain with maximum values in the peripheral region and minimum in the central region of the workpiece is formed in the workpiece before each subsequent processing cycle. Accordingly, the structural state also has a gradient distribution over the grain size. Constrained bending conditions provide a more uniform deformation field and lower average stresses in the deformation zone, which in turn leads to a smaller structural gradient in the cross section of the sample. After 4 cycles of free bending, a grain-subgrain structure with a minimum grain size of 7.0 ± 0.5 μm is formed in the surface layers of the workpiece, while in the central region, the grain size is 45 ± 5 μm.

In this work, we give a theoretical justification of the non-monotonic character of strain in the process of refinement and formation of a grain-type structure during the deformation processing of low-alloyed copper heat-hardenable alloys. A regularity is revealed, suggesting the alternating behavior of the strain state in the process of the continuous bending of billets. It is found that the continuous free bending process in the conditions of multi-cycle (four cycles) processing increases the strength and produces a gradient-type structure and a gradient of mechanical properties. Using fabrication of the experimental samples of the contact wire as an example, it is shown that the obtained results can serve as a scientific and technical foundation for the development of complex methods for the processing of axis-symmetrical long-length objects from copper heat-hardenable alloys in the form of wires and shaped products with improved mechanical properties, with potential adaptability for manufacturing.

No abstract

No abstract