급속응고 Al-20 wt% Si 합금분말 압출재의 ECAP

윤승채,홍순직,서민홍,팜쾅,김형섭,Yoon, Seung-Chae,Hong, Soon-Jik,Seo, Min-Hong,Quang, Pham,Kim, Hyoung-Seop 한국분말야금학회 2004 한국분말재료학회지 (KPMI) Vol.11 No.2

In this paper processing and mechanical properties of Al-20 wt% Si alloy was studied. A bulk form of Al-20Si alloy was prepared by gas atomizing powders having the powder size of 106-145 ${\mu}m$ and powder extrusion. The powder extrudate was subsequently equal channel angular pressed up to 8 passes in order to refine grain and Si particle. The microstructure of the gas atomized powders, powder extrudates and equal channel angular pressed samples were investigated using a scanning electron microscope and X-ray diffraction. The mechanical properties of the bulk sample were measured by compressive tests and a micro Victors hardness test. Equal channel angular pressing was found to be effective in matrix grain and Si particle refinement, which enhanced the strength and hardness of the Al-2OSi alloy without deteriorating ductility in the range of experimental strain of 30%.

기계적 특성 향상을 위한 마그네슘 합금의 등틍로각압출 공정 조건에 관한 연구

배성환,민경호,Bae, Seong-Hwan,Min, Kyung Ho 한국금형공학회 2016 한국금형공학회지 Vol.10 No.1

Although magnesium alloy has received much attention to date for its lightweight and high specific strength, their applications are impeded by the low formability which is caused by the hexagonal crystal structure at room temperature. In general, equal-channel angular extrusion(ECAE) is recognized as one of the attractive severe plastic deformation techniques where the processed bulk metals generally achieve ultrafine-grained microstructure leading to improved physical characteristics and mechanical properties. ECAE process has several parameters such as angle of die, process temperature, process route and speed. During ECAE process of Mg alloy, these parameters has great influence on the extrudability and the mechanical properties of alloy. The aim of this study is to estimate the influences of process conditions on the formability of AZ31 and AZ31-CaO alloys. Mg alloys are processed through ECAE at elevated temperatures using three types of die with channel angle of $90^{\circ}$, $110^{\circ}$, $135^{\circ}$ using route $B_c$, respectively. This study discusses the feasibility of using ECAE to improve both formability and strength on magnesium alloys by comparative analyzing the mechanical properties and microstructural evolution in each condition.

다양한 방식의 등통로각압축공정으로 가공된 Poly(Lactic acid) 시편들의 열 및 기계적 물성

류욱연 ( Xu Yan Liu ),정시인 ( Si In Jung ),최호석 ( Ho Suk Choi ),오준택 ( Jun Taek Oh ),김종국 ( Jong Kuk Kim ) 한국화학공학회 2011 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.49 No.2

We fabricated rod-like poly(lactic acid)(PLA) specimens through applying various methods of equal-channel angular extrusion(ECAE) process and investigated the change of thermal and mechanical properties of specimens before and after each ECAE process. Combining three re-injection routes(A, BC, and C) and three pass counts(1, 2 and 4) allowed us to fabricate 7 different PLA specimens. Thermal properties of each specimen were measured by both differential scanning calorimeter and thermo-gravimetric analyzer. Shear strains of each specimen with respect to applied loads were measured by indentation hardness tester. Field emmision scanning electron microscopy was used to observe internal microstructure of cross-section of each specimen. The observed microstructures qualitatively supported the explanation of hardness test results. Among 7 specimens, PLA-P2A showed the biggest shear strain probably due to its dense microstructure.

Three-dimensional finite element analysis of multi-pass equal-channel angular extrusion of aluminum AA1050 with split dies

Jin, Y.G.,Son, I.H.,Kang, S.H.,Im, Y.T. Elsevier Sequoia 2009 Materials science & engineering. properties, micro Vol.503 No.1

Equal-channel angular pressing (ECAP) is an effective method to produce bulk nanostructured materials with high strength and toughness. Many experimental researches using a conventional solid die have been done so far, but few attempts on finite element analysis have been undertaken to exploit load predictions of the multi-pass ECAP because of difficulty involved with handling the boundary and processing conditions. In this study, split dies were newly designed to reduce the flash formation and the accuracy of finite element simulations of the multi-pass ECAP was improved by introducing better friction condition and saturated flow stress model considering the effect of routes and number of passes. Experiments with commercially available pure aluminum alloy (AA1050) of a square cross-section were carried out using the split dies newly designed for routes A, B<SUB>C</SUB> and C up to three passes. The forming simulation tool, CAMPform3D, was currently used to investigate the effect of routes and number of passes in terms of prediction of the forming load and deformation behavior. It was found out that predicted loads obtained from current numerical simulations were reasonably accurate compared to the measured load data for the three-pass ECAP.

The Effect of Radiation Treatment on Mechanical and Thermal Properties of Semicrystalline Polymers Processed by Severe Plastic Deformation

Yuri Voznyak 한국고분자학회 2017 Macromolecular Research Vol.25 No.1

The effect of irradiation by electron beam with dose of 10-80 kGy on the properties of a number of semicrystalline polymers preliminary subjected to severe plastic deformation (SPD) was studied. SPD up to 8.5 was produced by equal-channel multiple-angular extrusion process. It was demonstrated that polymers capable for radiation hardening (such as high density polyethylene, Nylon-6) show an increase of stiffness and strength, the ductility remains at a non-irradiated polymer as well as retain low values of the effective coefficient of thermal expansion at the level of invar alloys. At the same time radiation softening is much weaker in the case of SPD processed polymers (such as polytetrafluoroethylene). The magnitude of the effect depends on the irradiation dose and the type of the polymer. The achieved effects are associated with the processes of radiation cross-linking, destruction and chemical crystallization.

ECAP된 마그네슘 합금(AZ31) 압출판재의 기계적 물성평가

윤덕재(D. J. Yoon),임성주(S. J. Lim),배성환(S. H. Bae),김응주(E. Z. Kim) 한국소성가공학회 2015 한국소성가공학회 학술대회 논문집 Vol.2015 No.10

In this paper, a transversely isotropic behavior of AZ31 Mg alloy produced by equal-channel angular pressing (ECAP) process was investigated through tensile test and microstructure observation. As a result of the tensile test in three directions(0°, 45°, and 90° to the extrusion direction of the sheet) at room temperature, elongation of as-extruded AZ31 alloy showed an unusual anisotropic behavior depending on the extrusion direction although the yield strength and tensile strength are similar to the ECAPed AZ31 alloy. After 4 ECAP passes following route BC, microstructural observations showed a significant grain refinement, leading to an equiaxed grain structure with average size of 2.5μm. The microstructures of the extruded billet are observed by the use of an Electron Back-Scattering Diffraction (EBSD) technique to evaluate of the influence of extrusion process on the grain refinement and recrystallization mechanism of AZ31 Mg alloy.

등통로각압축이 결합된 압출 공정에 의한 알루미늄 분말의 치밀화 거동

윤승채,김형섭,Yoon, Seung-Chae,Kim, Hyoung-Seop 한국분말야금학회 2008 한국분말재료학회지 (KPMI) Vol.15 No.3

Aluminum alloys are not only lightweight materials, but also have excellent thermal conductivity, electrical conductivity and workability, hence, they are widely used in industry. It is important to control and enhance the densification behavior of metal powders of aluminum. Investigation on the extrusion processing combined with equal channel angular pressing for densification of aluminum powders was performed in order to develop a continuous production process. The continuous processing achieved high effective strain and full relative density at $200^{\circ}C$. Optimum processing conditions were suggested for good mechanical properties. The results of this simulation helped to understand the distribution of relative density and effective strain.

Finite element analysis of planar twist channel angular extrusion (PTCAE) as a novel severe plastic deformation method

Ali Shokuhfar,Mahmoud Shamsborhan 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.5

A new severe plastic deformation (SPD) method based on equal channel angular pressing (ECAP) is introduced for producing ultrafinegrains in bulk alloys, entitled as “Planar twist channel angular extrusion (PTCAE)”. In PTCAE method, there is additional angle, α, (plusφ and ψ angles in ECAP method) which represents angle associated with the lateral reversal arc of curvature in deformation zone. Threedimensional finite element method (FEM) simulations of both ECAP and PTCAE processes were performed in order to investigate theplastic deformation state of processed samples and, moreover, the effect of different die geometry (in terms of variation of planar twistangle) on plastic strain distribution and magnitude. Results revealed that PTCAE process related with ECAP process can impose higherstrain values in different shear planes simultaneously in one deformation zone. Therefore, PTCAE can produce UFG or nanostructuredmaterials better than ECAP method which has simpler design and significantly higher efficiency compared with other new SPD processes.

Plastic Flow and Strain Homogeneity of an Equal Channel Angular Pressing Process Enhanced through Forward Extrusion

Nagasekhar, A. V.,Yoon, S. C.,Yoo, J. H.,Kang, S.-Y.,Baik, S. C.,El Aal, M. I. A.,Kim, H. S. The Japan Institute of Metals 2010 Materials transactions Vol.51 No.5

<P>The plastic deformation behavior of forward extrusion, equal channel angular pressing, and a combination of the forward extrusion and equal channel angular pressing processes are analyzed by the finite element method. Simulations were carried out under realistic conditions by considering the strain hardening of the material and the degree of friction. Strain homogeneity in the combined processes is also compared to that of the individual forward extrusion and equal channel angular pressing processes. The plastic flow is more complicated and the strain induced is non-uniform in the combined processes. However, the combined processes show no corner gap formation. Moreover, it led to the development of higher strains in a single step compared to the individual processes. In addition, the load requirements for the combined processes are higher than the summation of loads of the individual processes.</P>

Finite element investigation of equal channel angular extrusion with back pressure

Son, Il-Heon,Lee, Jeong-Ho,Im, Yong-Taek Elsevier 2006 Journal of materials processing technology Vol.171 No.3

<P><B>Abstract</B></P><P>The back pressure in equal channel angular extrusion (ECAE) can produce more uniform and increased strain level into the workpiece, consequently obtaining the improved material property of the workpiece. It also has advantages in fabricating the materials without forming defects by giving the compressive pressure to the material surfaces. This study numerically investigates the effect of back pressure on material behavior and strain distribution of the commercially available pure titanium (CP-Ti) specimen. The back pressure effect in multi-pass ECAE process was also examined. Three types of the die tooling termed as Type-I, Type-II and Type-III to apply back pressure were examined under the plane-strain and non-isothermal conditions. From the simulation results, it was found out that the back pressure applied to the ECAE greatly increased the strain level accumulated without reducing the uniformity of the strain distribution.</P>