Use of plastic deformation for the formation of complex structures and properties of metals is a widely used technique
Analysis of the status issue shows that one of the promising areas of research is to study the effect of combination of plastic deformation on the structure and mechanical properties of metallic materials to produce structures that ensure high strength and plastic characteristics. Under the combined plastic deformation understand forming material slozhnonapryazhennom state under the influence of multiple forces or torques.
The aim of the work was to compare the effect of equal channel angular pressing (ECAP) techniques and the hydrostatic extrusion (HE) on the structure and properties of copper
Schemes of equal-channel angular pressing and the hydrostatic extrusion depicted in Figure 1
HE differs in that instead of a punch is pressed sample with water under high pressure.
In research conducted microhardness on a PMT-3 microhardness, the study of the microstructure of the samples, the microstructure was photographed with increasing 400-x, measured grain size using the computer program AxioVision 4.6. The studies were conducted on samples of copper grade M0b. Samples were obtained by HE diameter 19mm and 22mm diameter by ECAP. Photo samples are shown in Figure 2 .
Figure 2 - The sample obtained by severe plastic deformation
The measured values of microhardness constructed three-dimensional graphs presented in Figure 3. Microhardness of the original sample of 170 N/mm2.
à – ECAP; b – HE;
Figure 3 - Distribution of microhardness over the cross section of the sample
Figure 3 shows that the sample obtained by ECAP microhardness at the edges of the sample is higher than in sertsevine. And in a sample obtained by the HE microhardness decreases from the top to the bottom of the sample. This can be explained by examining the microstructure of the sample (Figure 4).
a - the microstructure of the sample obtained by the HE
b - microstructure of the sample obtained by ECAP
Figure 4 - The microstructure of the samples obtained: a - by the HE, b - by ECAP;
The grain size in the original sample is 20-30 microns. Figure 5 and 6 shows the grain size of samples.
Figure 5 - Change the size of grains in the sample obtained by the HE
Figure 6 - Change the size of grains in the sample obtained by ECAP
From figures 4, 5 and 6 shows that the sample obtained by the HE grain size decreases from top to bottom. The sample obtained by the ECAP grain in the middle of the sample is larger than at the edges. This explains the distribution of microhardness over the cross section of the sample.
From the studies show that during severe plastic deformation is grain refinement is almost twice that leads to an increase in the microhardness of copper. However revealed differences in the effect of HE method and the method of ECAP on the structure and properties of copper. They are presented in Table 1.
Table 1 - Differences in grain size in samples
Table 1 shows that On average in the samples we obtain similar values of the size and the average number of crushed grains and grains with a size close to the source. However, in a sample obtained by ECAP appears a large number of grains with a size of 4-6mkm, which may indicate a more intensive process of deformation. This requires a detailed study of stress distribution in the samples during deformation. In further studies planned to study the fine structure of copper after the SPD, the study of thermal stability of the structure and the effect of subsequent deformation on structure and properties.