Features of Structure Formation in Layered Metallic Materials Processed by High Pressure Torsion
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TRODUCTION
SEVERE plastic deformation makes it possible to create metallic hybrid (composite) materials with simultaneous transformation of their structure into nano- or submicrocrystalline.[1–6] The high pressure torsion (HPT) deformation of layered samples (sandwiches) consisting of several layers made of dissimilar metals is of particular interest. There are well-known works in which some sandwiches were deformed by HPT: two-layer—aluminum/magnesium alloy’’[7,8]; threelayer—‘‘steel/vanadium alloy/steel’’[9,10]; ‘‘steel/copper/ steel’’[11]; ‘‘aluminum/magnesium alloy/aluminum’’[12]; ‘‘vanadium alloy/zirconium alloy/vanadium alloy’’[13]; 25-layer—‘‘copper/aluminum,’’[14] etc. In the structure of such materials after HPT, in some cases there was a smooth interface between the layers, in others—’’mixing’’ of layers and the formation of an ultrathin multilayer ‘‘vortex’’ structure. One of the mechanisms for the formation of vortex defects in metals under HPT is considered in References 14 and 15. However, the mechanisms and patterns of the formation of multi-layered structures in such materials under HPT have not been established.
STANISLAV O. ROGACHEV, SERGEY A. NIKULIN, VLADIMIR M. KHATKEVICH, and ALEXANDER A. KOMISSAROV are with the National University of Science and Technology MISIS, Leninsky pr. 4, Moscow, Russia, 119049. Contact e-mail: [email protected] ROMAN V. SUNDEEV is with the National University of Science and Technology MISIS and also with the Russian Technological University MIREA, Vernadskogo pr. 78, Moscow 119454, Russia. Manuscript submitted July 1, 2019.
METALLURGICAL AND MATERIALS TRANSACTIONS A
In this paper, we studied the main patterns of the structure formation in layered metallic materials during HPT-deformation; we proposed a physical model for the formation of multi-layered structures in such materials.
II.
MATERIALS AND RESEARCH METHODS
The three-layer samples (sandwiches) subjected to joint deformation by HPT were considered as materials for this study: (1) (2) (3) (4) (5) (6) (7)
steel/vanadium alloy/steel; steel/zirconium alloy/steel; vanadium alloy/zirconium alloy/vanadium alloy; steel/copper/steel; vanadium alloy/copper/vanadium alloy; zirconium alloy/copper/zirconium alloy; steel/steel/steel.
In the three-layer samples numbered (1)-(6), a softer material was chosen for the middle layer compared to the materials for the lower and upper layers. The upper and lower layers were made of the same material. In the three-layer sample numbered (7), all layers were made of the similar materials. Also, the use of selected materials for the layers of the original samples provided both same or different mechanical behavior of the layers in the course of severe plastic deformations, as well as the same or different type of crystal lattices. The original layers (plates) with diameters of 8 mm were cut by the electric spark method from 08Kh17T (AISI 439 type) and 15Kh25T (AISI 446) steel sheets and V-10Ti-5Cr vanadium alloy sheet, as well as from Zr-2.5 pct Nb alloy (E125 alloy) rod and 99.95 pct p
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