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Deformation Characteristics Evaluation of Modified Equal Channel Angular Pressing Processes
Yoon, Seung Chae,Nagasekhar, Anumalasetty Venkata,Yoo, Ji Hoon,Abd El Aal, Mohamed Ibrahim,Vaseghi, Majid,Kim, Hyoung Seop The Japan Institute of Metals 2010 MATERIALS TRANSACTIONS Vol.51 No.1
<P>In current studies, equal channel angular pressing process (ECAP) and modified ECAP processes are simulated under ideal conditions to compare the deformation characteristics. The deformation behaviour is more complicated and the strain induced during the processes is highly non-uniform in the modified ECAP processes except in the equal channel multi-angular pressing (ECMAP) process with Route C. The strain homogeneity is more of a possibility with ECAP and ECMAP with Route C processes. The deformation stress state is widely distributed in nature in modified ECAP processes than in conventional ECAP. In addition, the load requirements are also higher in modified ECAP processes with that of the ECAP process.</P>
ECAP법에 의해 제조된 6061 알루미늄 합금의 미세조직과 기계적 특성에 미치는 기공온도의 영향
강효경,김형욱,강석봉 대한금속재료학회 2002 대한금속·재료학회지 Vol.40 No.2
Equal Channel Angular Pressing(ECAP) was carried out on the 6061 aluminum alloy at room temperature, 373K, 423K, and 473K. The microstructures and mechanical properties of specimens pressed at different temperatures and cycles were investigated. All specimens pressed at different temperatures show ultra fine-grained microstructures with the average grain size less than 0.5 ㎛ and dislocation cell structure. When the pressing temperature increased higher than 423K, the tensile strength of the specimens decreased and the total elongation increased. In case of specimens pressed for 4 cycles at 473K, the fraction of grains having high angle grain boundaries is higher than that pressed at room temperature. The specimen pressed for 4 cycles at room temperature shows higher increase of the 0.2% yield strength, ultimate tensile strength and hardness, and much higher decrease of work hardening index.
ECAP으로 제조된 초미세립 Al-Mg 합금의 동적 변형거동
김양곤(Y.G. Kim),고영건(Y.G. Ko),신동혁(D.H. Shin),이성학(S. Lee) 한국소성가공학회 2009 한국소성가공학회 학술대회 논문집 Vol.2009 No.5
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 μm 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 crifical shear strain, deformation energy required for void initiation, and microstructural homogeneity related to ECAP routes.
이한상,황병철,이성학,안병두,신동혁,이창길 대한금속재료학회 2004 대한금속·재료학회지 Vol.42 No.4
Dynamic deformation and fracture behavior of ultra-fine-grained low-carbon steels fabricated by equal channel angular pressing (ECAP) was investigated in this study. Dynamic torsional tests were conducted on four steel specimens, two of which were annealed after ECAP, using a torsional Kolsky bar, and then the test data were compared via microstructures, tensile properties, and fracture mode. The ECAP'ed specimen consisted of very he, elongated grains of -0.5 μm in size, which were slightly coarsened and had an equiaxed shape after annealing. The dynamic torsional test results indicated that maximum shear stress decreased, while fracture shear strain increased, with increasing annealing time. Some adiabatic shear bands were observed at the gage center of the dynamically deformed torsional specimen, and their width was smaller in the ECAP'ed specimen than in the 1-hr annealed specimen, although they were not found in the 24-hr annealed specimen. Ultra-he, equiaxed grains of 0.05-0.3 μm in size were formed inside the adiabatic shear band, and their boundaries had characteristics of high-angle grain boundaries. These phenomena were explained by dynamic recovery and recrystallization due to the highly localized plastic deformation and temperature rise inside the adiabatic shear band. (Received February 11, 2004)
ECAP으로 제조된 초미세립 5083 Al 합금의 동적 변형거동
김양곤,황병철,이성학,김우겸,신동혁 대한금속재료학회 2005 대한금속·재료학회지 Vol.43 No.1
Dynamic deformation behavior of ultra-fine-grained aluminum alloys fabricated by equal channel angular pressing (ECAP) was investigated in this study. Dynamic torsional tests were conducted on four aluminum alloy using a torsional Kolsky bar, and then the test data were analyzed in relation to microstructures, tensile properties, and adiabatic shear band formation. The ECAP'ed specimens consisted of a considerable amount of second phase particles, which were refined and had an equiaxed shape as the ECAP pass number increased. The dynamic torsional test results indicated that maximum shear stress increased, while fracture shear strain remained constant, with increasing ECAP pass number. Observation of the deformed area beneath the fracture surface after the dynamic torsional test indicated that a number of voids initiated mainly at second phase particle/matrix interfaces, and that the number of voids increased with increasing pass number. Adiabatic shear bands of 100-150μm in width were formed in the as-extruded and 1-pass specimens having coarser second phase particles, while they were hardly formed in the 4-pass and 8-pass specimens having finer second phase particles. The possibility of the adiabatic shear band formation was explained by concepts of absorbed deformation energy and void initiation. (Received October 29, 2004)
ECAP으로 제조된 초미세립 저탄소강의 단열성 전단밴드의 미세조직 변화
황병철,이성학,김용찬,김낙준,신동혁 대한금속재료학회 2005 대한금속·재료학회지 Vol.43 No.5
The object of the present study is to investigate the microstructural development of the adiabatic shear band formed by dynamic torsional experiments of ultra-fine-grained low-carbon steels fabricated by equal channel angular pressing (ECAP). Dynamic torsional tests were conducted on four steel specimens, two of which were annealed after ECAP, using a torsional Kolsky bar, and then the test data were compared via microstructures, tensile properties, and fracture mode. The ECAP'ed specimen consisted of very fine, equiaxed grains of 0.2 !Am in size, which were slightly coarsened and had an equiaxed shape after annealing. Some adiabatic shear bands were observed at the gage center of the dynamically deformed torsional specimen, and their width was smaller in the ECAP'ed specimen than in the 1-hr annealed specimen, although they were not found in the 24-hr annealed specimen. Ultra-fine, equiaxed grains of 0.05~0.2 μm in size were formed inside the adiabatic shear band, and their boundaries had characteristics of high-angle grain boundaries. These phenomena were explained by dynamic recovery and recrystallization due to the highly localized plastic deformation and temperature rise occurred within the shear band. The temperature rise in the shear band formation process was inferred to be above 540℃ from the observation of spheroidization behavior of cementites in pearlite grains. (Received February 7, 2005)
급속응고 Al-20 wt% Si 합금 분말의 ECAP를 통한 고형화
윤승채,홍순직,서민홍,정영기,김형섭 한국분말야금학회 2004 한국분말재료학회지 (KPMI) Vol.11 No.3
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.
ECAP 가공 초미세립 조직 금속재료개발의 국가 경쟁력 분석
길상철(S.C. Kil),남수우(S.W. Nam),김환태(H. T. Kim) 한국소성가공학회 2013 한국소성가공학회 학술대회 논문집 Vol.2013 No.10
The increasing interest in the severe plastic deformation to conventional coarse-grained metals is placing stringent demands on the manufacturing techniques and performance requirements, and the engineer employs the high quality and efficiency processing technology for producing ultrafine grained materials. This paper covers recent research trends for of the equal channel angular pressing technology of the metals and alloys including the SCI-E analysis of published papers, research subjects and research institute analysis.