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A5052-H112 합금의 겹치기 마찰교반접합 조직 특성
고영봉,이중헌,박경채,Ko, Young-Bong,Lee, Joong-Hun,Park, Kyeung-Chae 대한용접접합학회 2009 대한용접·접합학회지 Vol.27 No.6
The Friction Stir Welding(FSW) has mainly been used for making butt joints in Al alloys. Development of Friction Stir Lap Welding(FSLW) would expand the number of applications. Microstructure of FSLW in A5052-H112 alloy was investigated under varying rotation and welding speed. As the rotation speed was increased and the welding speed was decreased, a amount of heat was increased. As a result, bead interval was narrower, bead width are larger, and experimental bead interval was almost similar to theoretical bead interval. Typical microstructures of FSLW A5052-H112 alloy consist of three zones, including Stir Zone(SZ), Thermo-Mechanically Affected Zone(TMAZ) and Heat Affected Zone(HAZ). As a amount of heat was increased, average grain size was larger in three zones. Nevertheless, the aspect ratio was almost fixed for FSLW conditions. The misorientation of SZ, HAZ and TMAZ was examined. A large number of low angle grain boundaries, which were formed by severe plastic deformation, were showed in TMAZ as comparison with SZ and HAZ. Microhardness distribution was high in order of BM, SZ, TMAZ, and HAZ. The Micro-hardness distribution in HAZ, TMAZ of upper plate were lager than lower plate. Relationship between average grain size and microhardness was almost corresponded to Hall-Petch equation.
BSCCO 플라즈마 용사피막의 부분용융열처리 후 어닐링 시간에 따른 초전도 특성
박정식,이선홍,박경채,Park, Jeong-Sik,Lee, Seon-Hong,Park, Kyeung-Chae 한국재료학회 2014 한국재료학회지 Vol.24 No.2
$Bi_2Sr_2CaCu_2O_x$(Bi-2212) and $Bi_2Sr_2Ca_2Cu_3O_y$(Bi-2223) high-Tc superconductors(HTS) have been manufactured by plasma spraying, partial melt process(PMP) and annealing treatment(AT). A Bi-2212/2223 HTS coating layer was synthesized through the peritectic reaction between a 0212 oxide coating layer and 2001 oxide coating layer by the PMP-AT process. The 2212 HTS layer consists of whiskers grown in the diffusion direction. The Bi-2223 phase and secondary phase in the Bi-2212 layer were observed. The secondary phase was distributed uniformly over the whole layer. As annealing time goes on, the Bi-2212 phase decreases with mis-orientation and irregular shape, but the Bi-2223 phase increases because a new Bi-2223 phase is formed inside the pre-existing Bi-2212 crystals, and because of the nucleation of a Bi-2223 phase at the edge of Bi-2212 crystals by diffusion of Ca and Cu-O bilayers. In this study the spray coated layer showed superconducting transitions with an onset Tc of about both 115 K, and 50 K. There were two steps. Step 1 at 115 K is due to the diamagnetism of the Bi-2223 phase and step 2 at 50 K is due to the diamagnetism of the Bi-2212 phase.
$TiO_2$ 및 Ag 스퍼터링-$TiO_2$ 플라즈마 용사피막의 광전류 및 광분해 특성
강태구,장용호,박경채,Kang, Tae-Gu,Jang, Yong-Ho,Park, Kyeung-Chae 대한용접접합학회 2009 대한용접·접합학회지 Vol.27 No.2
In this study, we investigated photocatalytic ability of plasma sprayed $TiO_2$ and Ag sputtering $TiO_2$(Ag-$TiO_2$) coatings. A sputtering processes were adopted to coat the surface of $TiO_2$ with Ag(99.99%). Ag was sputtered at 10mA, 450V for $1{\sim}11$ seconds. $TiO_2$ and Ag-$TiO_2$ coatings were heat-treated at 250, 300, 350, $400^{\circ}C$ for $0{\sim}240$seconds. Photoelectrical conductivity was measured by four-point probe, and photodegradation was calculated by UV-V is spectrometer. Microstructure observation of $TiO_2$ and Ag-$TiO_2$ coatings were investigated by SEM. Crystal structure of $TiO_2$ and Ag-$TiO_2$ coatings were investigated by XRD. Qualitative analyses of $TiO_2$ and Ag-$TiO_2$ coatings were conducted by EDX. When $TiO_2$ coatings were heat-treated at $350^{\circ}C$ for 30 sec, photoelectrical conductivity and photodegradation were best. And in XRD analysis result, (101)/(110) relative intensity ratio of $TiO_2$(rutile) was comparably changed with photoelectrical conductivity. When Ag-$TiO_2$ coatings were heat-treated at $350^{\circ}C$ for 30 [sec] after sputtering Ag for 7 sec, Photoelectrical conductivity and photodegradation are best. Surface of coatings in such condition has very small and uniform Ag particles.
고영봉,최준웅,박경채,Ko, Young-Bong,Choi, Jun-Woong,Park, Kyeung-Chae 대한용접접합학회 2010 대한용접·접합학회지 Vol.28 No.1
In Friction Stir Lap Welding(FSLW), the movement of material within the weld was more important than the microstructure, due to the interface present between the sheets. Thus, The soundness of free defect, Effective Sheet Thickness(EST) and width of joint were most important factor of mechanical properties. Specimens by lap joint types that were 'A-type' and 'R-type' were made in this study. A-type tensile specimen was loaded at advancing side and R-type tensile specimen was loaded at retreating side. Macro-, micro-structural observation and mechanical properties of FSLW A5052-H112 alloy ware investigated under varying rotating and welding speed. The results were as follows: Material hook formed decreasing after sharply increasing was appeared at the end interface of joint area in advanced side, and material hook formed decreasing after smoothly increasing was observed at that in retreated side. Tensile load had no relation with defects. As rotating speed was higher, tensile strength was increasing and EST was decreasing regardless of joint types. joint efficiency was over 70%. In a result of fractography, fracture in A-type was partially occurred by dimple in SZ, and fracture in R-type was generally occurred by dimple in HAZ.
플라즈마 용사 BSCCO(Bismuth Strontium Calcium Copper Oxide) 초전도 피막의 접합 특성
박정식(Jung-Sik Park),조창은(Chang-Eun Cho),고영봉(Young-Bong Ko),박광순(Kwang-Soon Park),박경채(Kyeung-Chae Park) 한국표면공학회 2013 한국표면공학회지 Vol.46 No.5
We performed plasma spraying for 2001 (Bi:Cu = 2:1), 0212 (Sr:Ca:Cu = 2:1:2) oxide powders. Bi₂Sr₂CaCu₂Ox (2212) superconductor has been prepared by PMP-AT (partial melting process-annealing treatment). The 2212 phase is synthesized between Sr-Ca-Cu oxide coating layer (0212) and Bi-Cu oxide coating layer (2001) by movement of partial melted Bi on 2001 layer and the diffusion reaction (Cu, Sr, Ca) after PMP-AT. There are two different coating layers on joining process. The one is ABAB coating layers and the other is BAAB coating layers by arrangement of 2001 (A), 0212 (B) layers. We performed heat treatment these two different coating layers processes under same PMP-AT conditions. We obtained Bi-2212 superconducting layers at each experimental condition, and the result of MPMS, the critical temperature was showed about 78 K. But the microstructure images and result of EDS as each experimental variable were showed about the qualitatively different Bi-2212 superconducting phases. We also deduced the generation mechanism of Bi-2212 superconducting layer as a result of these experimental data, microstruc ture images, EDS data and phase diagram.
5052 알루미늄 합금에서 접합변수에 따른 겹치기 마찰교반접합부의 특성
고영봉(Young-Bong Ko),박경채(Kyeung-Chae Park) 한국표면공학회 2012 한국표면공학회지 Vol.45 No.5
The Friction Stir Welding (FSW) has mainly been used for making butt joints in Al alloys. The development of Friction Stir Lap Welding (FSLW) would expand the number of applications. In this study, microstructures and mechanical properties of FSLW in A5052 alloy were investigated under varying rotating speed and probe length. Investigating the characteristics as FSLWed conditions were as below ; Failure Maximum load by shear fracture was increased proportional to the width of joint area, which was increased by input heat, stirring intensity in the case of 2.3 mm probe length. Tensile fracture occurred, and maximum load was determined due to side worm hole of joint area and softening of microstructure in the case of 3.0 mm probe length. In the case of 3.7 mm probe length, material hook and bottom worm hole were appeared at the end interface of joint area. The most sound FSLW condition with no defects was 3.0 mm probe length and 1500 rpm-100 mm/min. No defects were showed in 1500 rpm-100 mm/min and 1800 rpm-100 mm/min, but Vickers microhardness distribution in TMAZ/HAZ which was fracture zone was lower in 1800 rpm-100 mm/min than in 1500 rpm-100 mm/min. In this condition highest tensile strength, 215 MPa (allowable rate 78% of joint efficient) was obtained.
프루브 길이에 따른 A5052 겹치기 마찰교반접합 특성
고영봉(Young-Bong Ko),강채원(Chae-Won Kang),최준웅(Jun-Woong Choi),박경채(Kyeung-Chae Park) 한국표면공학회 2009 한국표면공학회지 Vol.42 No.6
The Friction Stir Welding (FSW) has mainly been used for making butt joints in Al alloys. The development of Friction Stir Lap Welding (FSLW) would expand the number of applications. In this study, for effective application on thin aluminum alloy lap joint, non-heat treatment A5052 alloys were joined by FSLW with the length of probe 2.3 ㎜ and 3.0 ㎜. Investigating the characteristics of joint area showed the results were as below ; When the length of probe was 2.3 ㎜, good joint area was formed at all welding condition except for 600 rpm-700 ㎜/min. In the case of 3.0 ㎜ probe length, there was formed good joint area without defects at 1500 rpm-100 ㎜/min. The width of joint area, position and size of defects were very important factors for FSLW, due to heat input and stirring intensity.