• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2006.05a
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• pp.119-122
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• 2006

In this study, bottom-up type powder processing and top-down type SPD (severe plastic deformation) approaches were combined in order to achieve full density of 1 vol.% carbon nanotube (CNT)-metal matrix composites with superior mechanical properties by improved particle bonding and least grain growth, which were considered as a bottle neck of the bottom-up method using the conventional powder metallurgy of compaction and sintering. ECAP (equal channel angular pressing), the most promising method in SPD, was used for the CNT-Cu powder consolidation. The powder ECAP processing with 1, 2, 4 and 8 route C passes was conducted at room temperature. It was found by mechanical testing of the consolidated 1 vol.% CNT-Cu that high mechanical strength could be achieved effectively as a result of the Cu matrix strengthening and improved particle bonding during ECAP. The ECAP processing of powders is a viable method to achieve fully density CNT-Cu nanocomposites.

• Transactions of Materials Processing
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• v.9 no.3
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• pp.219-225
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• 2000

Equal channel angular pressing (ECAP) is a convenient forming process to extrude material without substantial changes in the sample geometry and this deformation process gives rise to produce ultrafine grained materials. The properties of the materials are strongly dependent on the plastic deformation behaviour during ECAP. The major process variables during ECAP are 1) die geometries, such as a channel angle and coner angles, and 2) the processes variables, such as lubrication and deformation speed. In this study, the plastic deformation behaviour of materials during the ECAP has been theoretically analysed by the finite element method (FEM). The effect of the die friction on the plastic deformation behaviour during the pressing is discussed by means of FEM calculations.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.531-536
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• 2003

Equal channel angular pressing (ECAP) has been employed to produce materials with ultra-fine grains that have high strength and high corrosion resistance properties. In order to obtain super plastic deformation during ECAP, multipass angular pressing is frequently employed. In this paper, three-dimensional finite element analyses have been performed to investigate the deformation behavior of pure-Zr specimen and the effects of process parameters for equal channel multi-angular pressing (ECMAP) process. The results have been compared with some experimental results

• Transactions of Materials Processing
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• v.15 no.7 s.88
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• pp.524-528
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• 2006

Although equal channel angular pressing (ECAP), imposing large plastic shear strain deformation by moving a workpiece through two intersecting channels, is a promising severe plastic deformation method for grain refinement of metallic materials, its batch type characteristic makes ECAP inefficient for multiple-passing. Rotary-die ECAP (RDECAP) proposed by Nishida et al. can achieve high productivity by using continuous processing without taking out the samples from the channel. However, plastic deformation behavior during RD-ECAP has not been investigated. In this study, material plastic flow and strain hardening behavior of the workpiece during RD-ECAP was investigated using the finite element method. It was found that plastic deformation becomes inhomogeneous with the number of passes due to an end effect, which was not found seriously in ECAP. Especially, decreasing corner gap with increasing the number of passes was observed and explained by the strain hardening effect.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.9
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• pp.1539-1545
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• 2003

A lot of researches have been performed on the equal channel angular pressing (ECAP) which produces ultra-fine grains. Along with the experiments, the finite element method has been widely employed to investigate the deformation behavior of specimen during ECAP and the effects of process parameters of ECAP. In this paper, pure-Zirconium is considered for ECAP process by using three-dimensional finite element analysis. The results have been compared with those of previous two-dimensional analysis and with the experimental results

• Transactions of Materials Processing
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• v.16 no.5 s.95
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• pp.406-411
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• 2007

The microstructure and the hardness of interstitial free steel processed by equal channel angular pressing (ECAP) was investigated experimentally. ECAP processing of route A and route C was compared with regard to grain refinement by transmission electron micrographs. Micro hardness evolution was correlated with the gram structure produced by ECAP. Especially, the effects of the ECAP processing temperature and the number of processing passes were discussed in terms of grain refinement.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.306-309
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• 2009

The influence of equal-channel angular pressing (ECAP) route on dynamic deformation behavior of ultra-fine grained Al-4.4%Mg alloys was investigated in this study. The 8-pass ECAPed specimens consisted of ultra-fine grains of $0.5{\mu}m$ in size, and contained the considerable amount of second phase particles, which were fragmented and distributed homogeneously in the matrix. The result of dynamic torsional tests indicated that the maximum shear stress and fracture shear strain were lowest in the specimen deformed by ECAP via route A among the 8-pass ECAPed specimens. The formation of adiabatic shear bands was addressed by concepts of critical shear strain, deformation energy required for void initiation, and microstructural homogeneity related to ECAP routes.

• Journal of Powder Materials
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• v.11 no.3
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• pp.233-241
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• 2004

In this study, bottom-up type powder processing and top-down type SPD (severe plastic deformation) approaches were combined in order to achieve both full density and grain refinement of Al-20 wt% Si powders without grain growth, which was considered as a bottle neck of the bottom-up method using the conventional powder metallurgy of compaction and sintering. ECAP (Equal channel angular pressing), one of the most promising method in SPD, was used for the powder consolidation. The powder ECAP processing with 1, 2, 4 and 8 passes was conducted for 10$0^{\circ}C$ and 20$0^{\circ}C$ It was found by microhardness, compression tests and micro-structure characterization that high mechanical strength could be achieved effectively as a result of the well bonded powder contact surface during ECAP process. The SPD processing of powders is a viable method to achieve both fully density and nanostructured materials.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.827-832
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• 2001

A lot of investigations have been made in recent years on the equal channel angular pressing(ECAP) which produces ultra-fine grains(UFG). Among many process parameters such as channel angles, frictions, die deformations and materials employed, the effects of material properties on the deformation behavior have been investigated. The finite element method(FEM) has been used to investigate this issue.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2002.05a
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• pp.177-180
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• 2002

The effects of pressing temperatures on the formability and the microstructural evolution during equal channel angular pressing (ECAP) of lamellar Ti-6Al-4V alloy were investigated in this study. ECAP above isothermally 600$^{\circ}C$ was successful without producing any noticeable segments at the specimen surfaces after a single pass of pressing. After 4 passes of ECA pressing, lamellar microstructures were significantly refined revealing equiaxed grains of 0.3$\mu\textrm{m}$ in diameter consisting of high angle grain boundaries. Also these ultrafine grains were relatively stable with little grain growth when annealed up to 600$^{\circ}C$ for 1hour.