Abstract

Constructional streight of materials plays an important role in the maintenance of reliable and durable work of the details of machines and units. Creation of a new samples of technics in the aviation, machine-building, oil and gas extraction and other industries demands more rigid and increased requirements to the working capacity of constructions. It causes necessity of the application of materials with higher complex of physical-mechanical properties. For metallic materials this problem dares by the creation of the new alloys, or by the development of the new more effective thermal-mechanical processing of serial industrial alloys.

The possibilities of alloying by this time are mostly settled. Besides, the development of absolutely new alloys demands great material inputs on the creation of new compositions, their certification and introduction. Meanwhile last time the new direction in material science and processing of the materials intensively develops. It consists in the formation in metals and alloys ultradisperse structure. It allows to increase specific streight in the area of operational temperatures, thus in the area of the temperatures of processing by the pressure the technological plasticity increases essentially. On the basis of this direction it is possible to create essentially new complex of physical and chemical and mechanical properties in usual industrial materials. It concerns the metals and alloys, with the size of grains less then 0,1 microns.

The obtaining of the materials with ultradisperse structure for today is a difficult technological problem. The most perspective way of manufacturing of half-finished products with ultradisperse structure is the deformational-thermal processing. It includes intensive plastic deformation.

It is known that as a result of cold plastic deformation there is an accumulation of defects of a crystal structure, first of all dislocations. As a result of it in the primary grains there is a subgrains structure. Plastic deformation leads to structure crushing, but the traditional kinds of processing occurs the increase of the streight. So further plastic deformation becomes impossible. Therefore using usual methods of deformation it is impossible to receive nanograins. For formation of ultradisperse structure it is necessary to realize the special methods of plastic deformation. It consists in the deformation of material at least on two axes. Origin of cracks in a material in this case is at a loss and it makes it possible to continue the deformation of material for structure crushing.

Feature of a tension at intensive plastic deformation is the high share of tangents of pressure.

The kind of a tension and parity of components of the pressure in the deformation centre makes essential impact on behavior of a material, and also on its final structure and properties. Changing the deformation conditions, varying the degree of deformation and temperature, it’s possible to provide the changing of properties. Correction of thermal-deformational parameters usually use in many technological processes, such as: various schemes of extrusion, screw rolling, drawing with imposing of rotation of preparation and others.

The literature review shows that the modern material science is directed on the decision of a problem of the obtaining of ultrafine-grained materials with high corner borders of grains. By the methods of intensive plastic deformation it is possible to receive volume nanostructural materials with the size of grains 0,1-0,2 microns and the specifical substructure. Such structure has big elastic distortions of a crystal grate. It is considered that similar fine-grained structures should provide simultaneously high plastic and streight characteristics.

High corner borders of grains can be received by thermal-mechanical processing with multidirected deformation.

Creation of such structures can be carried out by the methods of the combined plastic deformation with the shift. The temperature of processing is low. The enclosed pressures are high. In material science using the term «intensive plastic deformations» is more often, means using in the scheme of the deformation the simple shift combined with compression (stretching).

Thus, now an important scientific question is studying of structurization and mechanical properties by the influence of the combined plastic deformation.

Thus, currently an important research question is the study of structure and mechanical properties under the influence of a combination of plastic deformation.

At the first stage of work acquaintance with the basic methods of intensive plastic deformation has been spent. At this standard of the development of a science the basic ways of intensive plastic deformation are torsion with shift, equal channel angular pressing, screw extrusion, 3D forgine, rolling with shift.

All methods described before have a common fault – the process of the deformation occurs in the tool of the difficult form. Thus the tool is exposed to the very big loadings and often breaks.

Shift rolling is very perspective method. Its feature is that simultaneously the influence carried out on the part of the volume of the metal. It has allowed to increase the sizes of the samples.

In my work the influence of shift rolling on structure and mechanical properties of copper, such as streight, plasticity and hardness is considered.

Shift rolling is one of methods of intensive plastic deformation. It represents the rolling on the shafts with the cuts. Cuts can be cross-section, longitudinal and combined. Besides, cuts can be symmetrized on one and on the second shaft, or can be displaced from each other. At such method the special kind of a current of metal realized.

Such kind of deformation was carried out on the samples from copper. Shift rolling was carried out on the shafts with the longitudinal, cross-section and combined cuts.

At this stage of the researching of influence of a kind of cuts on properties of copper is spending. Thus already now it is possible to tell that the kind of cuts makes very essential impact on microhardness and structure.

The obtained data demands more detailed and profound analysis. There are questions about the mechanism of hardening and unhardening in a material, about the influence of kind of the cuts. Therefore at a following stage it is planned to spend microstructure analysis, and to research the interrelation between a microstructure and a microhardness.

Now there is a considerable quantity of the researches devoted to a question of interrelation of formation of certain structure and properties under the influence of various mechanisms of plastic deformation. However the review of references has shown that it is a question is not solved regularly for schemes of the combined plastic deformation: the Data received by an empirical way, does not allow to formulate a way and to find methods of predicted management structure and properties at transition from the investigated alloys to other alloys, a different chemical compound, a crystal lattice, background of thermodeformation influences.

Earlier studying of a microstructure has been spent and following conclusions are made. The samples, subjected a rollig with shift, have the structure caused by the following factors. In the process of rollig there is a distortion of grains but when the deformation degree becomes above critical there is a process of the recrystallization. It is necessary to notice that the recrystallization begins in the more defective places. The recrystallizated grains are again involved into the process of plastic deformation. The development of the plural recrystallization alternating with a fragmentation gets repeating character. It leads to stage-by-stage crushing of the recrystallizated and fragmentated grains. The size of the recrystallizated grains is 0,5 - 4 microns. Such kind of structure provides high streight and plasticity.

The recrystallizated and the deformed grains are united in macrograins (drawing 5).

Figure 5 - The microstructure of a copper after the rolling with shift

Also with the measurement of microhardness and the general analysis of a microstructure there was the streight of the copper researched. The diagram of a stretching of the samples of copper after rolling with shift on drawing 6.

Figure 6 - The diagram of a stretching of the samples of copper after rolling with shift