EBSD에 의한 A1050 압연판재의 결정립 구조 분석

한준현,신명철,Han, Jun-Hyun,Shin, Myung-Chul 한국분석과학회 2001 분석과학 Vol.14 No.1

압연판재의 결정립 미세화를 위해 새롭게 도입된 극저온 강압연법을 극저온 압연법, 상온 강압연법과 비교 분석하였다. EBSD를 이용하여 결정립 구조를 분석하였으며, 결정립 크기를 측정하였다. 극저온 압연법과 상온 강압연법은 각각 39%와 87%의 결정립 크기 감소효과를 보였으며, 극저온 강압연법은 상온 강압연법과 비슷한 결정립 감소효과를 갖고 있었다. 따라서 강압연법이 극저온 압연법보다 결정립 미세화에 훨씬 더 효과적임을 알 수 있었다. The effect of cryogenic heavy rolling method on grain refinement has been studied and compared with those obtained by previous methods of cryogenic rolling and heavy rolling developed separately. Both grain structure and grain size were analyzed using electron back scattered diffraction (EBSD), which can distinguish grains each other by means of crystallographic misorientations between them. The cryogenic rolling and heavy rolling exhibit reduction in grain size of 39% and 87%, respectively, and the cryogenic heavy rolling shows reduced grain size similar to that observed in the heavy rolling. The heavy rolling was proved more effective in grain size refinement than the cryogenic rolling.

논문 : 표면처리 ; EBSD법에 의한 구리전착층의 미세조직과 결정방위에 관한 연구

최창희 ( Chang Hee Choi ),남효승 ( Hyo Seung Nam ),정재한 ( Jae Han Jeong ),이동녕 ( Dong Nyung Lee ) 대한금속재료학회 ( 구 대한금속학회 ) 1998 대한금속·재료학회지 Vol.36 No.7

The structure and texture of copper electrodeposits have been studied in a macro/microscopic viewpoint. The copper specimens composed by three different kinds of fibre texture, namely, near random, (110) and (111) have been obtained at various deposition conditions. The macro/microtexture have been investigated by X-ray and EBSD in SEM, respectively. The crystallographic orientation of each grain of copper electrodeposits could be roughly estimated using crystallographic etch pit method and it was compared with the results measured from EBSD. The through thickness orientation variation was also investigated using EBSD technique in SEM. The twin distribution and its density could be well characterized through this method.

EBSD를 이용한 1, 2차 용융흔 결정립의 방위 비교 분석

박광묵,방선배,양성채,Park, Kwang-Muk,Bang, Sun-Bae,Yang, Sung-Chae 한국전기전자재료학회 2017 전기전자재료학회논문지 Vol.30 No.11

Herein, for the quantitative analysis of the arc beads related to electric fire, we used electron backscatter diffraction (EBSD), a measuring device for grain orientation of materials, we compared and analyzed the surface texture of primary and secondary beads according to the difference in cooling rate at ambient temperature. This analysis revealed that the primary beads showed similar distribution at both low and high angles, while the secondary beads showed a higher distribution at low angles than at high angles. Thus, EBSD can be used for quantitative analysis of the beads and can be applied to identify beads in the future.

EBSD를 이용한 변형소둔한 극저탄소강의 결정립 성장 해석

安聖權,洪承賢,崔章鉉,鄭元燮 대한금속재료학회 2002 대한금속·재료학회지 Vol.40 No.8

A study has been made of the grain coarsening in IF steel after strain annealing. A 92.5% cold rolled and annealed IF steel sheet was temper rolled by 0.4% reduction in thickness and subsequently annealed at 750℃, 850℃ and 950℃ for various time periods. The grains occasionally started to grow abnormally near the surface and grew into the center during strain annealing. The pole figure and EBSD measurements showed that the abnormally grown grains did not have any orientation relation with the primary recrystallization texture before temper rolling. Grains which underwent less strains due to their orientations during temper rolling are believed to grow at the expense of surrounding grains from the calculated Taylor factors. Thus, the major coarsening mechanism was regarded to be the strain induced grain boundary migration rather than grain boundary characteristics.

EBSD측정에 의한 반복겹침접합압연된 무산소동의 두께방향으로의 미세조직 변화 분석

이성희,임차용,Lee, Seong-Hee,Lim, Cha-Yong 한국재료학회 2014 한국재료학회지 Vol.24 No.11

Microstructural evolution in the thickness direction of an oxygen free copper processed by accumulative rollbonding (ARB) is investigated by electron back scatter diffraction (EBSD) measurement. For the ARB, two copper alloy sheets 1 mm thick, 30 mm wide and 300 mm long are first degreased and wire-brushed for sound bonding. The sheets are then stacked and roll-bonded by about 50% reduction rolling without lubrication at an ambient temperature. The bonded sheet is then cut to the two pieces of the same dimensions and the same procedure was repeated on the sheets up to eight cycles. The specimen after 1 cycle showed inhomogeneous microstructure in the thickness direction so that the grains near the surface were finer than those near the center. This inhomogeneity decreased with an increasing number of ARB cycles, and the grain sizes of the specimens after 3 cycles were almost identical. In addition, the aspect ratio of the grains decreased with an increasing number of ARB cycles due to the subdivision of the grains by shear deformation. The fraction of grains with high angle grain boundaries also increased with continuing process of the ARB so that it was higher than that of the low angle grain boundaries in specimens after 3 cycles. A discontinuous dynamic recrystallization occurred partially in specimens after 5 cycles.

PWHT 대체 원자로 냉각계통 예방정비를 위한 와이어 아크 적층 제조를 통한 용접부 상분율 제어

김준영(Junyeong Kim),김동진(Dongjin Kim),박정수(Jungsoo Park) 한국산학기술학회 2023 한국산학기술학회논문지 Vol.24 No.9

이 연구는 원자력 발전소 냉각재 계통(Reactor Coolant System, RCS) 일차수응력부식균열(Primary Water Stress Corrosion Cracking, PWSCC)에 대응하기 위해 열처리 효과를 유도한 예방정비 와이어 아크 적층 제조(Wire-Arc Additive Manufacturing, WAAM)를 적용하여, 용접후열처리(Post Weld Heat Treatment, PWHT)를 대체하여 마르텐사이트 상분율 억제를 구현하기 위해 수행되었다. 이를 위해 총 3층 적층 용접이 수행되었으며, 반복적으로 용접 적층시 전개되는 열영향부의 미세구조가 광학현미경(Optical Microscopy, OM), 주사전자현미경(Scanning Electron Microscope, SEM) 및 전자후방산란회절(Electron Back-scatter Diffraction, EBSD)을 통해 정량화되었다. 결과적으로, 1층 적층 HAZ에서 67.4 % 마르텐사이트로 구성되었던 상분율이, 3층 적층 HAZ에서는 26.8 %로 현저히 감소되는 열처리 효과가 구현되었다. 마르텐사이트 분율의 감소는 1층 적층 HAZ 경도 395.8Hv가 3층 적층 HAZ경도 320.9Hv로 완화되는데 지배적인 메커니즘으로 밝혀졌다. 이러한 결과를 바탕으로 WAAM 공정을 통해 용접부 상분율을 제어하고 경도의 변화를 발생시킬 수 있었으며, 이는 PWHT를 대체할 수 있는 기술로 간주될 수 있다. This study was conducted to address PWSCC in the RCS of a nuclear power plant. WAAM was applied to induce a heat treatment effect and achieve suppression of martensite formation and replace PWHT. To replace the PWHT, three layers of additive welding were performed, and the HAZ that developed during each welding pass was quantified using OM, SEM, and EBSD. As a result, the heat treatment effect significantly reduced the martensite fraction from 67.4% in the first-layer HAZ to 26.8% in the third-layer HAZ. The reduction in martensite fraction was identified as the dominant mechanism for the decrease in hardness from 395.8 Hv in the first-layer HAZ to 320.9 Hv in the third-layer HAZ. Based on these results, it can be considered that controlling the martensite fraction and inducing hardness changes in the weld zone through WAAM processes can replace PWHT.

미세 조직을 고려한 무산소동 다결정재의 변형 거동에 대한 미소역학적 연구

하상렬(Sangyul Ha),김기태(KiTae Kim) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.4

본 연구에서는 다결정재에서 발생하는 결정립 간의 불균일한 변형거동을 조사하기 위하여 조대한 주상 결정립을 가진 무산소동 구리 다결정재의 평면변형압축 실험을 수행하였다. 각 결정립의 결정학적 방위의 변화는 EBSD를 이용하여 측정하였으며, 압축 변형 후의 결정립 형상은 FE-SEM으로 관찰하였다. 또한, 샘플의 전체 형상 및 결정립의 형상 변형과 집합조직의 발전을 속도의존성 결정소성모델을 적용한 유한요소 해석결과와 비교하였다. In this study, plane strain compression experiments of an OFHC copper multicrystal which consists of large columnar grains were conducted to examine heterogeneous distribution of deformation patterns in each grain of the sample. The evolution of the crystallographic orientation in each grain was measured by the electron back scattered diffraction (EBSD) system. Also, the morphologies of the grains normal to TD were observed after compression by using a field emission scanning electron microscope (FE-SEM). Finally, finite element calculations based on the rate-dependent crystal plasticity model were compared with experimental results: the overall shape change of the compression sample, the deformed shapes of the individual grains, and the rotation of the crystallographic orientation.

티타늄의 변형률 경화 특성에 미치는 쌍정의 영향 분석

안광현(Kwanghyun Ahn),허훈(Hoon Huh),윤종헌(Jonghun Yoon) 한국자동차공학회 2012 한국자동차공학회 부문종합 학술대회 Vol.2012 No.5

This paper is concerned with the effect of deformation twinning on the strain hardening in pure titanium. It is reported that the strain hardening of titanium during compressive deformation shows uncommon behavior. Generally, strain hardening rate of metallic materials is decreasing as strain increases. In accordance with many researches for titanium, however, strain hardening behavior of titanium shows different characteristics from general metallic materials. It is observed that the strain hardening rate of titanium during compression process can be divided into 3 stages. In first stage, strain hardening rate is decreasing as strain increases. Following first stage, strain hardening rate is increasing as strain increases in second stage. After second stage, strain hardening rate is decreasing again as strain increases in third stage. It is well known that the occurrence of the second stage is due to the occurrence of the deformation twinning. In this paper, the occurrence and the growth of the deformation twinning are observed using EBSD. Change of twin volume fraction during compressive deformation of titanium is investigated quantitatively. Strain hardening model which can represent the strain hardening of titanium is also suggested by investigating the effect of deformation twinning on the strain hardening behavior.

Investigation of Fe-rich fragments in aluminum-steel friction stir welds <i>via</i> simultaneous Transmission Kikuchi Diffraction and EDS

Abbasi, Majid,Dehghani, Morteza,Guim, Hwan-Uk,Kim, Dong-Ik Elsevier 2016 Acta materialia Vol.117 No.-

<P>An attempt has been made to investigate Fe-rich fragments and surrounding intermetallic compounds in aluminum-steel friction stir welds using conventional EBSD + EDS as well as advanced Transmission Kikuchi Diffraction (TKD). Results indicate that the fragments are covered by a layer of orthorhombic Al5Fe2. This layer is surrounded by a mixed region composed of sub-micrometer Al3Fe crystals in a matrix of Al nano grains. Employing high beam current TKD on electron-transparent samples enables investigation of sub-micrometer grains in the mixed region with a higher spatial resolution than conventional EBSD. As a result, nano-twinning in Al in the mixed region has been observed. Microstructural and texture results imply that Fe-rich fragments travel through the Al matrix under extreme shear forces, severely refining Al grains, and inducing nano-twinning. Due to extreme shear forces and Fe outward diffusion, fine steel fragments dissolve in the surroundings leading to the nucleation of nano Al3Fe crystals particularly along Al grain boundaries. Al3Fe crystals consume the Al matrix as they grow in size and fraction. (C) 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.</P>

수소취화된 스테인리스강 304의 VHCF(Very High Cycle Fatigue) 피로특성과 UNSM처리 효과에 관한 연구

남승훈(Seung-Hoon Nahm),백운봉(Un-Bong Baek),서창민(Chang-Min Suh),편영식(Young-Sik Pyun) 대한기계학회 2018 大韓機械學會論文集A Vol.42 No.6

실온에서 미처리재와 UNSM 처리재, 수소취화재(10 MPa, 300 ℃, 120 h) 및 이 수소취화재의 UNSM 처리재의 스테인리스강 304 시험편의 재료특성파악을 위한 실험에서 수소취화재는 기존의 미처리재의 S-N곡선보다 피로강도가 거의 비숫한 경향을 나타내었으며, 수소취화효과는 미미하였다. 미처리재와 수소취화재의 피로한도는 400 ㎫로 같았고, 약 8.1배의 많은 수소를 함유함에도 수소취화영향은 거의 없었다. 미처리재에 비해서 UNSM처리재의 피로한도는 약 50 % 상승하였고, 수소취화재의 UNSM처리재는 수소취화재보다 약 50 % 상승하는 경향을 나타내었다. EBSD에 의한 IQ, IPF, KAM 및 phase diagram map에서 UNSM처리 후, 이 처리의 영향을 받는 나노 입자 표면층의 두께는 약 112 ㎛이다. This study is to investigate the influence of hydrogen attack and UNSM on fatigue behaviors of STS 304. Fatigue endurance limit of untreated material and hydrogen treated one was the same at 400 ㎫, and hydrogen embrittlement had little influence even though it contained about 8.1 times more hydrogen. Thus the sensitivity of hydrogen gas of this STS 304 material is very low. The fatigue endurance limit of the UNSM treated material rose by about 50 % compared with the untreated material and showed a tendency to increase by about 50 % as compared with the hydrogen treated material. After the UNSM treatment with IQ, IPF, KAM and phase diagram map by EBSD, the thickness of the nanoparticle surface layer affected by this treatment is about 112 ㎛.