V. Stolyarov, Mechanical Engineering Research Institute, Moscow, Russia; I. Gurtovaya, K. Inaekyan, Moscow State Institute of Steels and Alloys, Moscow, Russia; U. Ugurchiev, A. Sergeeva, Moscow State Industrial Insitute, Moscow, Russia; S. Prokoshkin, Moscow Institute of Steel and Alloys, Moscow, Russia
It is known the shape memory TiNi alloys possess the best functional properties. Recently it has been shown, that these alloys demonstrate especially high strength, reactive stress and recoverable strain in ultrafine-grained (UFG) state processed by severe plastic deformation (SPD) namely high pressure torsion (HPT) [1], or equal channel angular pressing (ECAP) [2]. Numerous applications of TiNi alloys in medicine and technique are based on semi-finished products, in particular, long-size strips and wire of thin section. There are some restrictions for practical application of HPT and ECAP articles that are connected with both the sizes and insufficient technological plasticity UFG billets. That is why, thin long-size product with high-accumulated strain, sufficient for formation of UFG structure at post-deformation annealing, is impossible to process by traditional SPD methods. In this connection the opportunity of use cold rolling with the electropulse influence to form UFG structures in TiNi alloy is considered in the report. The first experience of electroplastic deformation (EPD) application to these alloys is described in works [3, 4]. The purpose of the work consisted in search of EPD modes for nanostructure formation in strips of coarse-grained TiNi alloy.
The investigated earlier Ti49.4Ni50.6 alloy was chosen as object of the present study, in the form of a strip in the sizes 2x6x150 mm in course-grained state processed by quenching from 800°Ñ in water. Samples were subjected to EPD with a variation of cold rolling, annealing and pulse current regimes.
Structural studies, tensile tests, functional properties, technological experiments on deformability and strip widening have been executed. The presented data are discussed and compared for cold rolling with and without a current.
The work was supported by Russian Federation Agency on Science and Innovation, projects 02.513.11.3076.
Summary: Structure and properties for as received course-grained TiNi, subjected to cold rolling with and without pulse current are discussed.
