Characterization of microstructure evolution after severe plastic deformation of pure copper with continuous columnar crystals
15 Jul 2010-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing (Elsevier)-Vol. 527, Iss: 18, pp 4750-4757
TL;DR: In this article, a pure copper bar with continuous columnar crystals was fabricated by continuous unidirectional solidification and it exhibited novel plastic deformation ability with total true strain over 13.5 during rolling and drawing at room temperature without annealing.
Abstract: Pure copper bar with continuous columnar crystals was fabricated by continuous unidirectional solidification. The bar with orientation preference along [0 0 1] exhibited novel plastic deformation ability with total true strain over 13.5 during rolling and drawing at room temperature without annealing. Microstructure analysis and in situ observation of tensile test were performed to investigate the mechanism of plastic deformation. Results exhibit that the novel plastic deformation ability of copper bar is beneficial from the absence of transverse grain boundary as well as small angle grain boundary of the continuous columnar microstructure. The existence of cell structure, recrystallization and deformation twin leads to grain rotation during deformation and enhances the orientation preference of the continuous columnar crystals, enabling copper bar a high ability for further deformation.
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19 Aug 2019-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, the effect of different cold rolling reduction rates on mechanical properties and electrical conductivity of C70250 copper alloy strips was investigated, and the mechanism of the mechanism was revealed.
Abstract: The contradictory relation between the strength and electrical conductivity of Cu–Ni–Si alloy after cold deformation is a significant scientific issue, break the contradictory relation is an important challenge for preparing the Cu–Ni–Si alloy with high strength and electrical conductivity. The C70250 copper alloy strips were prepared by temperature controlled mold continuous casting (TCMCC) and cold rolled. The effects of different cold rolling reduction rates on mechanical properties and electrical conductivity of the alloy were investigated, and the mechanism was revealed. The results indicate that the C70250 copper alloy strip prepared by TCMCC can be directly cold rolled with large deformation. When the cumulative cold rolling reduction rate reaches 97.5%, the strength and electrical conductivity of the alloy increase by 327 MPa and 0.6 IACS%, respectively. With the increase of cold rolling reduction rate, the shear deformation degree of columnar grain structure with strong [001] orientation increases gradually in C70250 copper alloy prepared by TCMCC. The alloy forms a large number of parallel shear bands consisting of high density dislocations, which seriously hinder the slip of dislocations and lead to the continuous increase of strength of the alloy. The parallel distributed shear bands in the C70250 copper alloy uniformly cut the matrix during the cold rolling process, and finally form a fibrous-shaped microstructure. The transverse grain boundary density is significantly reduced after cold deformation, which greatly reduces the influence of transverse grain boundary on the electrical conductivity and leads to abnormal increase of the electrical conductivity of the alloy.
32 citations
15 Dec 2012-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, a new bulk severe plastic deformation method based on repetitive forging (RF) using inclined punches is proposed, which is applied to commercially pure copper and significant grain refinement was achieved after four passes of RF.
Abstract: A new bulk severe plastic deformation method based on repetitive forging (RF) using inclined punches is proposed. This process consists of two half cycles. In the first half cycle, a square cross section deforms to parallelogram by forging with two inclined punches, and the parallelogram cross section is forged back to square using two flat punches in the second half cycle. This method was applied to commercially pure copper and significant grain refinement was achieved after four passes of RF. The results showed that significant improvement in the mechanical properties was obtained. Notable increase of yield and ultimate strengths corresponding to 358 MPa and 381 MPa after four passes of RF from the initial values of 121 MPa and 230.5 MPa is detectable. Microhardness increases to about 100 Hv after four passes of RF from the initial value of 53 Hv. Finite element (FE) results illustrate that RF is able to impose extremely high plastic strains to the materials. In the RF process, the processed samples have the same dimensions and geometry as those of the initial sample without any waste material and there is no need for back pressure.
32 citations
TL;DR: The microstructure, microhardness, texture and corrosion resistance of cold-swaged and coldwiredrawn copper rods were evaluated in this article, where the copper grains in both cold-worked rods presented a preferential orientation in the [1/1/0] crystallographic direction but this trend was more pronounced for swaged rods.
31 citations
27 Mar 2020-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, two different copper powder batches with different oxygen levels are processed and compared to wrought and annealed copper, and the mechanical properties of the crack-free samples are investigated.
Abstract: Additive Manufacturing using Selective Electron Beam Melting is attractive to fabricate pure copper components due to the specific properties of the electron beam. In this contribution, two different copper powder batches with different oxygen levels are processed. The samples produced using the powder with high oxygen level show cracks, whereas samples from the powder with low oxygen content are crack-free. The mechanical properties of the crack-free samples are investigated and compared to wrought and annealed copper.
29 citations
15 Dec 2011-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, the texture evolution and microstructure in continuous columnar-grained polycrystalline copper during wire drawing at room temperature were investigated quantitatively using the electron backscatter diffraction (EBSD) technique, and the stored energy and flow stress were calculated based on the texture constitution and structural parameters of different texture components measured by high resolution EBSD.
Abstract: The texture evolution and microstructure in continuous columnar-grained (CCG) polycrystalline copper during wire drawing at room temperature were investigated quantitatively using the electron backscatter diffraction (EBSD) technique, and the stored energy and flow stress were calculated based on the texture constitution and structural parameters of different texture components measured by high resolution EBSD. The results indicate that the development of 〈1 1 1〉 texture within original 〈1 0 0〉 columnar grains was significantly slower compared with that in equiaxed polycrystalline copper, e.g. the volumetric ratio of the 〈1 1 1〉 to 〈1 0 0〉 component in columnar-grain copper was 0.82 at the strain of 2.98, while it was 2.96 in equiaxed polycrystalline copper at the same strain. The relatively low content of 〈1 1 1〉 fiber texture accounted for the low flow stress, low work hardening rate and excellent cold plastic extensibility of the columnar-grained polycrystalline copper. The average size of the dislocation cells developed within the 〈1 1 1〉 fiber was the minimum among all the deformation texture components, and decreased rapidly with the increase of strain, leading to a high stored energy, a high flow stress and a high work hardening rate. On the other hand, the average size of the dislocation cells developed within the 〈1 0 0〉 fiber was the maximum, which held a large value at high strain, leading to a low stored energy, a low flow stress and a low work hardening rate.
27 citations
References
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TL;DR: In this article, the deformation microstructure is subdivided by dislocation boundaries having different characteristics depending on the orientation of the deformed grain, and the majority of the dislocations in the boundaries originate from active slip systems predicted by a Schmid factor analysis.
454 citations
TL;DR: In this article, the authors investigated the microstructural variables influencing the stress required to produce deformation twins in polycrystalline fcc metals and found that the dislocation density and the homogeneous slip length are the most relevant micro-structural variable that directly influence the deformation twinning stress in the polycrystal.
Abstract: This article investigates the microstructural variables influencing the stress required to produce deformation twins in polycrystalline fcc metals. Classical studies on fcc single crystals have concluded that the deformation-twinning stress has a parabolic dependence on the stacking-fault energy (SFE) of the metal. In this article, new data are presented, indicating that the SFE has only an indirect effect on the twinning stress. The results show that the dislocation density and the homogeneous slip length are the most relevant microstructural variables that directly influence the twinning stress in the polycrystal. A new criterion for the initiation of deformation twinning in polycrystalline fcc metals at low homologous temperatures has been proposed as (σ
tw
−σ
0)/G=C(d/b)A, where σ
tw
is the deformation twinning stress, σ
0 is the initial yield strength, G is the shear modulus, d is the average homogeneous slip length, b is the magnitude of the Burger’s vector, and C and A are constants determined to have values of 0.0004 and −0.89, respectively. The role of the SFE was observed to be critical in building the necessary dislocation density while maintaining relatively large homogeneous slip lengths.
420 citations
TL;DR: In this article, the deformation twins were observed in polycrystalline Cu with grain sizes varying from micrometers to nanometers during the process of equal channel angular pressing at room temperature and low strain rate.
244 citations
TL;DR: In this paper, the evolution of deformation microstructure in medium to high stacking fault energy fcc metals has been described in terms of a general framework of grain subdivision involving the formation of rotates volume elements for all deformation modes.
159 citations
25 Mar 2008-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, a mixture of equal-channel angular pressing (ECAP), high pressure torsion (HPT) and a combination of both in order to find out the evolution on the microstructural homogeneity for each of the processes and their combination.
Abstract: Pure Cu of 99.98 wt.% purity has been processed at room temperature by diverse techniques of severe plastic deformation, namely equal-channel angular pressing (ECAP), high pressure torsion (HPT) and a combination of both in order to find out the evolution on the microstructural homogeneity for each of the processes and their combination. Starting with a grain size of ∼60 μm, severe plastic deformation has been introduced to the material while maintaining the sample dimensions unchanged through the processes of ECAP and HPT. A significant decrease in grain size was observed by transmission electronic microscopy (TEM). Microtensile and microhardness tests were carried out on the deformed material in the three processing conditions. A significant improvement of the tensile strength was promoted with admissible penalization on ductility.
155 citations