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Acta Metall Sin  2017, Vol. 53 Issue (8): 991-1000    DOI: 10.11900/0412.1961.2016.00582
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Deformation Characteristics and Mechanical Properties of Single Crystal Copper During Equal Channel Angular Pressing by Route A
Tingbiao GUO1,2(), Qi LI1, Chen WANG1, Feng ZHANG1, Zhi JIA1,2
1 State Key Laboratory of Advanced Processing and Recycling of Nonferrous Metals, Lanzhou University of Technology, Lanzhou 730050, China
2 Key Laboratory of Non-Ferrous Metal Alloys and Processing, Ministry of Education, Lanzhou University of Technology, Lanzhou 730050, China
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The single crystal copper has got more and more attention in the important areas of the national economy due to its good conductivity and thermal conductivity and elongation. Whereas the lower strength limits its application and strengthening methods of single crystal copper are of great concern. The traditional strengthening methods, such as solid solution strengthening, fine grain strengthening and deformation strengthening, can seriously damage the conductivity of single crystal copper. As an effective method for severe plastic deformation (SPD), equal channel angular pressing (ECAP) can effectively improve the material strength and keep its excellent performance by controlling the deformation and strain. Deformation texture of the single crystal copper (99.999%) during ECAP by A route was investigated by XRD, EBSD and TEM, the mechanical properties and conductivity were tested, and the mechanism of texture evolution and influence factors of mechanical and electrical properties during deformation process were analyzed. The results show that equiaxed deformation structure with small sizes appeared in single crystal copper after two passes extruded. After four passes of deformation, deformation band structure with same (110) orientation was formed. And the grain orientation of the highly refined grains gradually tended to the (111) surface, the {111}<110>, {111}<112> textures and the little {001}<100> recrystallization texture formed. The scattering of electrons by grain boundaries (GBs) can effectively get reduced and conductivity increases slightly, at the same time, the work hardening rate of the material is significantly improved when {hkl}<110> texture with stable orientation forms under medium and low strains. A large number of low-angle grain boundaries (LAGBs) are formed in the initial deformation stage of single crystal copper. With the increase of strain, the LAGBs gradually change to the high-angle grain boundaries (HAGBs). Dislocation accumulation and GB density increase that dislocation movement is obstructed during deformation process. The tensile strength increases from 168 MPa to 400 MPa, the elongation decreases from 63% to 27.3% after three passes deformation. With the extrusion process, the tensile strength increases slowly, whereas the elongation increases slightly. When the extrusion pass is less than eight times, hardness increases continuously, and recrystallization occurs after eighth passes extrusion that hardness tends to be unstable.

Key words:  single crystal copper      equal channel angular pressing      deformation band      texture      mechanical property     
Received:  30 December 2016     
ZTFLH:  TG379  
Fund: Supported by National Natural Science Foundation of China (No.51261016)

Cite this article: 

Tingbiao GUO, Qi LI, Chen WANG, Feng ZHANG, Zhi JIA. Deformation Characteristics and Mechanical Properties of Single Crystal Copper During Equal Channel Angular Pressing by Route A. Acta Metall Sin, 2017, 53(8): 991-1000.

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Fig.1  Schematic of equal channel angular pressing (ECAP) (TD—transverse direction, ND—normal direction, ED—extrusive direction, α—die angle, β—die corner angle)
Fig.2  EBSD orientation maps of single crystal copper before (a) and after one pass (b), two passes (c), four passes (d) and eight passes (e) ECAP
Fig.3  Misorientation distributions of single crystal copper after one pass (a), two passes (b), four passes (c) and eight passes (d) ECAP
Fig.4  Low (a, b) and high (c, d) magnified TEM images of dislocation structures of single crystal copper after four passes (a, c) and eight passes (b, d) ECAP
Fig.5  XRD spectra of single crystal copper before and after different ECAP passes
Fig.6  Orientation parameter K of single crystal copper before and after different ECAP passes
Fig.7  Pole figures of single crystal copper before (a) and after one pass (b), two passes (c), four passes (d) and eight passes (e) ECAP
Fig.8  Orientation distribution function (ODF) sections of single crystal copper before (a) and after one pass (b), two passes (c), four passes (d) and eight passes (e) ECAP
Fig.9  Conductivities of single crystal copper and polycrystalline copper before and after different passes ECAP
Fig.10  Relationships between extrusion pass and tensile strength and elongation
Fig.11  Relationship between extrusion pass and hardness
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