• Title, Summary, Keyword: microstructure

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Microstructure and Mechanical Properties of Oxygen Free Copper Processed by ARB at Low Strain Rate (저변형률속도에서 ARB가공된 무산소동의 미세조직 및 기계적 성질)

  • Lee, Seong-Hee;Han, Seung-Zeon;Lim, Cha-Yong
    • Korean Journal of Materials Research
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    • v.17 no.10
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    • pp.521-525
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    • 2007
  • 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.

FE Analysis of Hot Forging Process and Microstructure Prediction for Lower Arm Connector (로워암 커넥터 열간단조 공정의 유한요소해석 및 미세조직 예측)

  • Park, Jong-Jin;Hwang, Han-Sub;Lee, Sang-Joo;Hong, Seung-Chan;Lim, Sung-Hwan;Lee, Kyung-Sub;Lee, Kyung-Jong
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.27 no.7
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    • pp.1243-1250
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    • 2003
  • In the present study, hot forging process for a lower arm connector of an automobile was investigated. An FEM code, DEFORM-3D, was used to analyze the process and the process parameters, such as temperature, strain and strain rate, were obtained. The microstructure of the connector was predicted by applying the Sellars and Yada microstructure evolution models to the process parameters. The method of microstructure prediction used in the present study seems to be effective for the quality assurance of a forged automotive product.

Analytical Quantification and Effect of Microstructure Development in Thick Film Resistor Processing

  • Lee, Byung Soo
    • Journal of the Microelectronics and Packaging Society
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    • v.19 no.4
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    • pp.33-37
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    • 2012
  • Microstructure developments of $RuO_2$ based thick film resistors during firing as a function of glass viscosity were analytically quantified and its effect on the electrical property was investigated. The microstructure development was retarded as the viscosity of glass was increased. It was found that the viscosity range for each stage of microstructure development are as follows ; $7500-10^5Pa{\cdot}s$ for the glass sintering, $2000-7500Pa{\cdot}s$ for the glass island formation, $700-2000Pa{\cdot}s$ for the glass spreading, and $50-700Pa{\cdot}s$ for the infiltration. The sheet resistivity decreased as the viscosity of glass in the resistor film increased due to the higher chance of sintering for the conductive particles with the higher viscosity of the glass.

Microstructure Control of Cu-Ni-Zr-Ti Metallic Glass Composites by Multi-Pass Extrusion Process (다중압출공정을 이용한 Cu-Ni-Zr-Ti 비정질 복합재의 미세조직제어)

  • Kim, Taek-Soo;Lee, Jin-Kyu
    • Transactions of Materials Processing
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    • v.16 no.5
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    • pp.386-390
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    • 2007
  • In order to, simultaneously, synthesize and control the size of microstructure of amorphous/crystalline composites, a repeated extrusion process was performed using the gas atomized $Cu_{54}Ni_6Zr_{22}Ti_{18}$ metallic glass powders and the crystalline brasses. The size of microstructure in the resultant composites was varied depending on the pass of extrusion as well as on the area reduction ratio. The microstructure could be estimated using an equation of $r_n=r_{n-1}/R^{1/2}$, where R is reduction ratio and $r_n$ is the resultant radius of the extruded bar after n pass. Theory of microstructural refinement as well as the relationship between the resultant microstructures and mechanical properties was discussed.

The microstructure and mechanical performance of high strength alloy steel X2M

  • Manigandan, K.;Srivatsan, T.S.;Freborg, A.M.;Quick, T.;Sastry, S.
    • Advances in materials Research
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    • v.3 no.1
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    • pp.283-295
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    • 2014
  • In this paper, the microstructure, hardness, tensile deformation and fracture behavior of high strength alloy steel X2M is presented anddiscussed. The influence of both composition and processing on microstructure of the as-provided material and resultant influence of microstructure, as a function of orientation, on hardness, tensile properties and final fracture behavior is highlighted. The macroscopic mode and intrinsic microscopic features that result from fracture of the steel specimens machined from the two orientations, longitudinal and transverse is discussed. The intrinsic microscopic mechanisms governing quasi-static deformation and final fracture behavior of this high strength steel are outlined in light of the effects oftest specimen orientation, intrinsic microstructural effects and nature of loading.

The Study of Microstructure Influence at Fretting Contacts using Crystal Plasticity Simulation (결정 소성 시뮬레이션을 이용한 프레팅 접촉에서의 마이크로 구조 영향에 관한 연구)

  • Ko, Jun-Bin;Goh, Chung-Hyun;Lee, Kee-Seok
    • Journal of the Korean Society for Precision Engineering
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    • v.22 no.8
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    • pp.84-91
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    • 2005
  • The role of microstructure is quite significant in fretting of Ti-6Al-4V since its material properties depend strongly on crystallographic texture. In this study, we adopt crystal plasticity theory with a 2-D planar triple slip idealization to account fur microstructure effects such as grain orientation distribution, grain geometry, as well as $\alpha$ colony size. Crystal plasticity simulations suggest strong implications of microstructure effects at fretting contacts.

Change in Hardness and Microstructure with Quenching and Tempering of Ductile Cast Iron (구상흑연주철의 열처리에 따른 미세조직 및 경도 변화)

  • Jeong, Woo Chang
    • Journal of the Korean Society for Heat Treatment
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    • v.21 no.2
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    • pp.69-78
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    • 2008
  • Differences in hardness and microstructure between surface and area at 0.3 mm below the surface after quenching and tempering of ductile cast iron for rear planet carrier of automotive transmission have been investigated. Microstructure of ductile cast iron consisted of ferrite, pearlite, and nodular graphite. The amount of pearlite increased with going down to the half-thickness area. It was found that Cr and Mo segregated to the pearlite and the pearlite transformed to the harder martensite during quenching. The martensite was more resistant to the decomposition to ferrite and cementite during tempering because of segregation of Cr and Mo, resulting in the harder tempered martensite. Consequently, the hardness of the surface with less amount of pearlite, corresponding to the harder martensite in the quenched and tempered microstructure, was lower than that of the area at 0.3 mm below the surface.

CONTROL OF NITROGEN CONTENT FOR THE IMPROVEMENT OF HAZ

  • Bang, Kook-soo;Kim, Byong-chul;Kim, Woo-yeul
    • Proceedings of the KWS Conference
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    • pp.229-234
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    • 2002
  • The variation of HAZ toughness with nitrogen content and weld cooling rate was investigated and interpreted in terms of both microstructure and the amount of free nitrogen. The presence of free nitrogen in HAZ was investigated by internal friction measurement and its amount was measured by hydrogen hot extraction analysis. Both nitrogen content and weld cooling rate influenced HAZ microstructure and high toughness was obtained at a mixed microstructure of acicular ferrite, feffite sideplate and polygonal ferrite. If nitrogen content is too low or cooling rate is too fast, bainitic microstructure is obtained and toughness is low. On the other hand, if nitrogen content is too high or cooling rate is too slow, coarse polygonal ferritic microstructure is obtained and toughness is deteriorated again. ill addition to the microstructural change, high nitrogen content also resulted in a large amount of free nitrogen. Therefore, nitrogen content should be kept as low as possible even if the mixed micostructure is obtained. In this experimental condition, the maximum toughness was obtained at 0.006% nitrogen content when weld cooling time ($\Delta$t$_{8}$5/)) is 60s.TEX>5/)) is 60s.

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EFFECT OF MICROSTRUCTURE ON MECHANICAL PROPERTIES IN FRICTION STIR WELDED CAST A356 ALUMINUM ALLOY

  • Sato, Yutaka S.;Kaneko, Takayasu;Urata, Mitsunori;Kokawa, Hiroyuki
    • Proceedings of the KWS Conference
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    • pp.493-498
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    • 2002
  • Friction stir welding (FSW) is a relatively new solid-state joining process which can homogenize the heterogeneous microstructure by intensely plastic deformation arising from the rotation of the welding tool. The present study applied the FSW to an A356 aluminum (AI) alloy with the as-cast heterogeneous microstructure in the T6 temper condition, and examined an effect of microstructure on mechanical properties in the weld. The base material consisted of Al matrix with a high density of strengthening precipitates, large eutectic silicon and a lot of porosities. The FSW led to fragment of the eutectic silicon, extinction of the porosities and dissolution of the strengthening precipitates in the Al alloy. The dissolution of strengthening precipitates reduced the hardness of the weld around the weld center and the transverse ultimate tensile strength of the weld. Longitudinal tensile specimen containing only the stir zone showed the roughly same strength as the base material and a much larger elongation. Moreover, Charpy impact tests indicated that the stir zone had remarkably the higher absorbed energy than the base material. The higher mechanical properties of the stir zone were attributed to a homogenization of the as-cast heterogeneous microstructure by FSW.

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Effect of Sintering Atmosphere Changing Temperature on Microstructure and Mechanical Property of Al2O3/Cu Nanocomposites (소결분위기 변환온도가 Al2O3/Cu 나노복합재료의 미세조직과 파괴강도에 미치는 영향)

  • Oh Sung-Tag;Yoon Se-Joong
    • Journal of Korean Powder Metallurgy Institute
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    • v.11 no.5
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    • pp.421-426
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    • 2004
  • The microstructure and mechanical property of hot-pressed $Al_2O_3/Cu$ composites with a different temperature for atmosphere changing from H$_{2}$ to Ar have been studied. When atmosphere-changed from H$_{2}$ to Ar gas at 145$0^{\circ}C$, the hot-pressed composite was characterized by inhomogeneous microstructure and low fracture strength. On the contrary, when atmosphere-changed at low temperature of 110$0^{\circ}C$ the composite showed more homogeneous microstructure, higher fracture strength and smaller deviation in strength. Based on the thermodynamic consideration and microstructural analysis, it was interpreted that the Cu wetting behavior relating to the formation of CuAlO$_{2}$ is probably responsible for strong dependence of microstructure on atmosphere changing temperature. The reason for a strong sensitivity of fracture strength and especially of its deviation to atmosphere changing temperature was explained by the microstructural inhomogeneity and by the role of CuAlO$_{2}$ phase on the interfacial bonding strength.