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이성희,조준,이충효,한승전,임차용,Lee Seong-Hee,Cho Jun,Lee Chung-Hyo,Han Seung-Zun,Lim Cha-Yong 한국재료학회 2005 한국재료학회지 Vol.15 No.9
An oxygen free copper severely-deformed by eight cycles (an equivalent strain of $\~6.4$) of accumulative roll-bonding (ARB) was annealed at various temperatures ranging from 100 to $300^{\circ}C$. The annealed copper was characterized by transmission electron microscopy (TEM) and tensile & hardness test. TEM observation revealed that the ultrafine grains developed by the ARB still remained up to $150^{\circ}C$, however above $200^{\circ}C$ they were replaced by equiaxed and coarse grains due to an occurrence of the static recrystallization. Tensile strength and hardness of the copper decreased slightly with the annealing temperature up to $150^{\circ}C$, however they dropped largely above $200^{\circ}C$. Annealing characteristics of the copper were compared with those of a commercially pure aluminum processed by ARB and subsequently annealed.
동속압연과 이속압연이 동합금판재의 조직 및 기계적 성질에 미치는 영향
이성희,임정윤,윤대진,어광준,한승전,Lee, Seong-Hee,Lim, Jung-Youn,Yoon, Dae-Jin,Euh, Kwang-Jun,Han, Seung-Zeon 한국재료학회 2011 한국재료학회지 Vol.21 No.1
The effects of conventional rolling (CR) and differential speed rolling (DSR) on the microstructure and mechanical properties of a copper alloy sheet were investigated in detail. A copper alloy with thickness of 3 mm was rolled to a 50% reduction at ambient temperature without lubrication with a differential speed ratio of 2:1; sample was then annealed for 0.5h at various temperatures from 100 to $800^{\circ}C$. Conventional rolling, in which the rolling speed of the upper and lower rolls is identical, was performed under the same rolling conditions. The shear strain introduced by the CR showed positive values at positions on the upper roll side and negative values at positions on the lower roll side. However, the shear strain showed a zero or positive value at all positions for the samples rolled by the DSR. The microstrucure and mechanical properties of the as-rolled copper alloy did not show very significant differences between the CR and DSR for the microstructure and mechanical properties. However, those properties showed very significant differences in the case of the annealed samples. The effects of rolling method on the microstructure and mechanical properties of the as-rolled and subsequently annealed materials are discussed in terms of the shear strain.
이성희,한승전,김형욱,임차용,Lee, Seong-Hee,Han, Seung-Zeon,Kim, Hyoung-Wook,Lim, Cha-Yong 한국재료학회 2009 한국재료학회지 Vol.19 No.8
A Cu-Fe-P copper alloy was processed by accumulative roll-bonding (ARB) for ultra grain refinement and high strengthening. Two 1mm thick copper sheets, 30 mm wide and 300 mm long, were first degreased and wire-brushed for sound bonding. The sheets were then stacked on top of each other and roll-bonded by about 50% reduction rolling without lubrication at ambient temperature. The bonded sheet was then cut into two pieces of the same dimensions and the same procedure was repeated for the sheets up to eight cycles. Microstructural evolution of the copper alloy with the number of the ARB cycles was investigated by optical microscopy (OM), transmission electron microscopy(TEM), and electron back scatter diffraction(EBSD). The grain size decreased gradually with the number of ARB cycles, and was reduced to 290 nm after eight cycles. The boundaries above 60% of ultrafine grains formed exhibited high angle boundaries above 15 degrees. In addition, the average misorientation angle of ultrafine grains was 30 degrees.
이성희,한승전,임차용,Lee, Seong-Hee,Han, Seung-Zeon,Lim, Cha-Yong 한국재료학회 2006 한국재료학회지 Vol.16 No.9
A deoxidized low-phosphorous (DLP) copper was processed by accumulative roll-bonding (ARB) for ultra grain refinement and high strengthening. Two copper 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 to each other, and roll-bonded by about 50% reduction rolling without lubrication at ambient temperature. The bonded sheet is then cut to the two pieces of same dimensions and the same procedure was repeated to the sheets up to eight cycles (${\varepsilon}{\sim}6.3$). TEM observation revealed that ultrafine grains were developed after the 4th cycle, and their size decreased at higher cycles. Tensile strength of the copper increased with the equivalent strain, and it reached 547 MPa which was 3 times higher than that of the initial material. It is concluded that the ARB process is an effective method for high strengthening of the DLP copper.
이속압연에 의해 가공된 Cu-Ni-Si 합금의 미세 조직 및 기계적 성질
이성희,한승전,Lee, Seong-Hee,Han, Seung Zeon 한국재료학회 2016 한국재료학회지 Vol.26 No.1
Effects of conventional rolling(CR) and differential speed rolling(DSR) on the microstructure and mechanical properties of Cu-Ni-Si alloy were investigated in detail. The copper alloy with thickness of 3 mm was rolled to 50 % reduction at ambient temperature without lubricant with a differential speed ratio of 2:1. The conventional rolling in which the rolling speed of upper and lower rolls is identical was performed under identical rolling conditions. The shear strain introduced by the CR showed positive values at positions of upper roll side and negative values at positions of lower roll side. However, it showed zero or positive values at all positions for the samples rolled by the DSR. The microstrucure and texture development of the as-rolled copper alloy did not show any significant difference between CR and DSR. The tensile strength of the DSR processed specimen was larger than that of the CR processed specimen. The effects of rolling methods on the microstructure and mechanical properties of the as-rolled copper alloy are discussed in terms of the shear strain.
반복겹침접합압연법에 의해 강소성가공된 무산소동의 미세조직 및 기계적 특성
이성희,조준,한승전,임차용,Lee Seong-Hee,Cho Jun,Han Seung-Zun,Lim Cha-Yong 한국재료학회 2005 한국재료학회지 Vol.15 No.4
An oxygen free copper was severely deformed by accumulative roll-bonding (ARB) process for improvement of its mechanical properties. Two copper sheets 1 m thick, 30 mm wide and 300 m long are first degreased and wire-brushed for sound bonding. The sheets are then stacked to each other, and roll-bonded by about $50\%$ reduction rolling without lubrication at ambient temperature. The bonded sheet is then cut to the two pieces of same dimensions and the same procedure was repeated to the sheets up to eight cycles $(\varepsilon-6.4)$. TEM observation revealed that ultrafine grains were developed after the third cycle, and their size was slightly increased at higher cycles. Tensile strength of the copper increased with the strain at low strain levels, but it hardly increased from 3 cycles $(\varepsilon>2.4)$ due to occurrence of dynamic recovery, even if the imposed strain increased.
저변형률속도에서 ARB가공된 무산소동의 미세조직 및 기계적 성질
이성희,한승전,임차용,Lee, Seong-Hee,Han, Seung-Zeon,Lim, Cha-Yong 한국재료학회 2007 한국재료학회지 Vol.17 No.10
The microstructure and mechanical properties of an oxygen free copper processed by accumulative roll bonding(ARB) at low strain rate were studied. The copper sheets were highly strained up to an equivalent strain of ${\sim}6.4$ by ARB process at ambient temperature. The strain rate of the copper during the ARB was $2.6sec^{-1}$. The microstructure and mechanical properties of the ARB-processed copper were compared to those of the specimens processed by ARB at relatively high strain rate ($37sec^{-1}$). The microstructure and mechanical properties of the copper with ARB process was very similar to each other despite of some differences in recovery.
ARB가공된 인탈산동의 어닐링에 따른 미세조직 및 기계적 특성 변화
이성희,김춘수,김상식,한승전,임차용,Lee, Seong-Hee,Kim, Chun-Su,Kim, Sang-Shik,Han, Seung-Zeon,Lim, Cha-Yong 한국재료학회 2007 한국재료학회지 Vol.17 No.7
A deoxidized low-phosphorous copper processed by eight cycles of accumulative roll-bonding (ARB) was annealed at various temperatures ranging from 100 to $400^{\circ}C$. The annealed copper was characterized by transmission electron microscopy (TEM) and tensile & hardness test. TEM observation revealed that the ultrafine grains developed by the ARB still remained up to $350^{\circ}C$, however above $400^{\circ}C$ they were replaced by equiaxed and coarse grains due to an occurrence of the static recrystallization. The hardness of the copper decreased slightly with the annealing temperature up to $350^{\circ}C$, however they dropped largely above $400^{\circ}C$. Annealing characteristics of the copper were compared with those of an oxygen free copper processed by ARB and subsequently annealed.
냉간압연된 Cu-3.0Ni-0.7Si 합금의 어닐링에 따른 두께방향으로의 미세조직 및 기계적 특성 변화
이성희,한승전,Lee, Seong-Hee,Han, Seung Zeon 한국재료학회 2018 한국재료학회지 Vol.28 No.2
Effects of annealing temperature on the microstructure and mechanical properties through thickness of a cold-rolled Cu-3.0Ni-0.7Si alloy were investigated in detail. The copper alloy with thickness of 3 mm was rolled to 50 % reduction at ambient temperature without lubricant and subsequently annealed for 0.5h at $200{\sim}900^{\circ}C$. The microstructure of the copper alloy after annealing was different in thickness direction depending on an amount of the shear and compressive strain introduced by rolling; the recrystallization occurred first in surface regions shear-deformed largely. The hardness distribution of the specimens annealed at $500{\sim}700^{\circ}C$ was not uniform in thickness direction due to partial recrystallization. This ununiformity of hardness corresponded well with an amount of shear strain in thickness direction. The average hardness and ultimate tensile strength showed the maximum values of 250Hv and 450MPa in specimen annealed at $400^{\circ}C$, respectively. It is considered that the complex mode of strain introduced by rolling effected directly on the microstructure and the mechanical properties of the annealed specimens.