• Title/Summary/Keyword: microstructure effect

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Effect of Thermomechanical Treatments on Microstructure and Mechanical Properties in Al-Li-Cu-Mg Alloy (Al-Li-Cu-Mg합금의 조직과 기계적 성질에 미치는 가공열처리의 영향)

  • Woo, Kee-Do;Cho, Hyun-Kee
    • Journal of the Korean Society for Heat Treatment
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    • v.3 no.1
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    • pp.8-16
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    • 1990
  • Effects of thermomechanical treatments(TMT) on the microstructures and mechanical properties in Al-2.27%, Li-1.28%, Cu-0.63%, Mg-0.12%, Zr alloy were investigated. The TMT process improved the tensile strength. Growth of ${\delta}^{\prime}$, S' and $T_1$ phases was restrained by TMT processes while the density of ${\delta}^{\prime}$, S' and $T_1$ phases was increased by TMT processes. The TMT treated specimens tend to fail in inter-subboundary mode. The increases of strength by the T-HA processes were compared to those of the T-AHA processes.

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An experimental study on the in-process measurement of case depth for LASER surface hardening process (레이저 표면경화 공정에서 경화층깊이의 실시간 측정을 위한 실험적 연구)

  • Woo, H.G.;Park, Y.J.;Han, Y.H.
    • Journal of the Korean Society for Precision Engineering
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    • v.10 no.2
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    • pp.66-75
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    • 1993
  • This paper proposes a monitoring method for nondestructive and in-process measurement of the case depth in LASER surface heat treatment process. The method is essentially an eddy-current method, and measures sensing coil's electrical impedance which varies with the changes of the material microstructure due to hardening. To investigate te validity of the proposed method a series of experiments were performed for various hardning depths. The results show that the relationship between the eddy- current sensor output and the changes in case depth is almost linear. This indicates that the eddy-current measuring method can be used as one of the possible monitoring method for mesauring the hardened depth in LASER heat treatment processes.

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On the Wear Properties of the Alumina Short Fiber and Particle Reinforced Aluminium Bronze Alloy Composite (알루미나 단섬유 및 입자강화 알루미늄 청동기지 복합재의 마모특성)

  • 이상로;허무영
    • Tribology and Lubricants
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    • v.10 no.3
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    • pp.39-46
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    • 1994
  • In order to investigate the effect of the ceramic reinforcements on the wear properties of aluminum bronze composites, Cu-8wt%Al aluminum bronze alloys reinforced with the Saffil alumina short fiber were produced by the powder metallurgical method and tested by a pin-ondisc wear testing machine. The wear surfaces of the pin specimens and discs, wear debris, and the cross sections of the wear specimens were observed by SEM. The wear mechanism according to various wear conditions and the change of microstructure in the composites were also discussed. In the results, the reinforcement of the composites with alumina short fiber was very effective at the higher applied load over 10N. The material transportation to the counter disc was observed in the alloy specimens without reinforcements. However, the composites reinforced with ceramic particles and fibers showed the resistance against the material transportation.

Study on Phenomenological and Crystal Plasticity Models to Predict Anisotropic Behaviors for Aluminum Alloy Sheets (알루미늄 판재의 이방성거동 예측을 위한 현상학적 모델과 결정소성학적 모델의 비교연구)

  • Chung, W.J.;Yoon, J.W.;Cuitino, A.
    • Transactions of Materials Processing
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    • v.15 no.8 s.89
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    • pp.574-580
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    • 2006
  • Anisotropy has an important effect on the strain distribution in aluminum alloy sheet forming, and it is closely related to the thinning and formability of sheet metals. Thus, the anisotropy of the material should be properly considered for the realistic analyses of aluminum sheet forming processes. For this, anisotropy can be approached in two different scales: phenomenological and microstructural (polycrystal) models. Recent anisotropic models (Yld2000-2d; Barlat et al.[1] 2003, Cuitino et al.[2] 1992) were employed in this work. For the simulation using shell element, the method which can impose plane stress condition in the polycrystal model is developed. Lankford values and yield stress ratios are calculated along various directions. As planar anisotropic behavior, a circular cup deep drawing simulation was carried out to compare the phenomenological and microstructure models in terms of earing profile.

Effect of Bonding Condition on High Temperature Mechanical Properties of TLP Bonded Joints of FE-35Ni-26Cr Alloy (Fe-35Ni-26Cr 주강 액상확산접합부의 고온기계적 특성에 미치는 접합조건의 영향)

  • 김대업
    • Journal of Welding and Joining
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    • v.18 no.4
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    • pp.96-103
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    • 2000
  • This study investigated the effects of bonding temperature and bonding atmosphere on high temperature mechanical properties of transient liquid phase(TLP) bonded joints of heat resistant alloy using MBF-50 insert metal. Specimens were bonded at 1,423~1,468K for 600s. Microconstituents of {TEX}$Cr_{7}(C,B)_{3}${/TEX}were formed in the bonded region when the bonding temperature was low. The amount of microcostituents in the bonded layer decreased with increasing the bonding temperature, and the microconstituents in the bonded layer disappeared at the bonding temperature above 1,468K. The tensile strength of the joints at elevated temperatures increased with the increase the bonding temperature and was the same level as one of the base metal in the bonding temperature over 1,453K. Microstructure and alloying element distributions of the bonded region bonded in Ar and $N_2$atmosphere were similar to those of the bonded in vacuum. The creep rupture strength and rupture lives of joints were almost identical to those of base metal.

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The effect of external electromagnetic force on droplet in GMAW (가스메탈 아크용접법에서 전자기력이 아크 현상에 미치는 영향에 관한 연구)

  • Lee, Sung-Ho;Lee, Jae-Yoon;Kim, Yong;Kim, Jae-Sung;Lee, Bo-Young
    • Proceedings of the KWS Conference
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    • 2003.11a
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    • pp.221-223
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    • 2003
  • Effects of electromagnetic force which is one of the most important factor of metal transfer that affects bead geometry and microstructure of weld metal in GMAW(gas metal arc welding). In this paper, different ways of external electromagnetic forces were applied on GMAW process and their effects on the welding were studied. On certain conditions, better bead geometry, better influence on the arc and metal transfer mode and higher welding efficiency could be obtained. Experimental methods and their results will be presented.

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Effect of Binder Addtion Method on Microstructure and Magnetic Prooperties of Sr-ferrite (결합체 첨가 방법이 Sr-ferrite의 미세구조와 자기적 성질에 미치는 영향)

  • 이병교;김정주;조상희
    • Journal of the Korean Ceramic Society
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    • v.27 no.4
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    • pp.548-552
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    • 1990
  • Effects of binder addition method during compacting on microstructural change and magnetic characteristics of Sr-ferrite system was investigated. Used binders were PVA and PEG, which were added separately or simultaneously. After compacts were heated at 50$0^{\circ}C$ for 3hr in air for burning out all the binders, they were sintered at 125$0^{\circ}C$ for 2h. Based on results, in the case of using the two binders simultaneously, comparing to single binder system, compacted density was somewhat higher but sintered density was rather lower, and abnormal grain growth was accelerated. According to these sintering characteristics, remanent magnetization and coercive force were also diminished.

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Effects of Stearic Acid on the Watertightness Properties of the Cementitious Materials (시멘트 재료의 수밀성에 대한 스테아르산의 영향)

  • Na, Seung-Hun;Kang, Hyun-Ju;Song, Myong-Shin
    • Journal of the Korean Ceramic Society
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    • v.46 no.4
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    • pp.365-371
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    • 2009
  • It is well known that the properties of concrete such as the compressive strength, water permeability, water tightness and durability are affected by micro-structure in hardened cement paste. Especially, for durability of concrete, watertightness of cementitious materials is the most critical property among various properties. Recently, many types of materials as organic and/or inorganic materials are used for watertightness of concrete. In this study, The effect of Stearic Acid at $0.5\;wt%{\sim}3.0\;wt%$ adding ratios on the hydration and watertightness property of cement were investigated. And we also discussed the changing of microstructure in hardened cement paste by addition of Stearic Acid. Cement paste with Stearic Acid showed improvement of watertightness by reducing of cement total pore volume and decomposition of Stearic Acid.

Transport Property of Externally Reinforced Bi-2223 Superconducting Tape under Axial Fatigue Loading

  • Shin, Hyung-Seop;John-Ryan C. Dizon;Kim, Ki-Hyun;Oh, Sang-Soo;Ha, Dong-Woo
    • Progress in Superconductivity and Cryogenics
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    • v.6 no.4
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    • pp.22-26
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    • 2004
  • For practical applications, the evaluation of reliability or endurance of HTS conductors is necessary. The mechanical properties and the critical current, Ie, of multifilamentary Bi-2223 superconducting tapes, externally reinforced with stainless steel foils, subjected to high cycle fatigue loading in the longitudinal direction were investigated at 77K. The S-N curves were obtained and its transport property was evaluated with the increase of repeated cycles at different stress amplitudes. The effect of the stress ratio, R, on the Ie degradation behavior under fatigue loading was also examined considering the practical application situation of HTS tapes. Microstructure observation was conducted in order to understand the Ie degradation mechanism in fatigued Bi-2223 tapes.

A Study on the Residual Stress and Microstructure of Autofrettaged SCM440 High Strength Steel (자긴가공된 SCM440 고강도강의 잔류응력 및 미세구조 분석에 관한 연구)

  • Kim, J.H.;Shim, W.S.;Lee, Y.S.;Cha, K.U.;Hong, S.K.
    • Proceedings of the KSME Conference
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    • 2008.11a
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    • pp.311-316
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    • 2008
  • Thick-walled cylinders, such as a cannon or nuclear reactor, are autofrettaged to induce advantageous residual stresses into pressure vessels and to increase operating pressure and the fatigue lifetimes. As the autofrettage level increases, the magnitude of compressive residual stress at the bore also increases. The purpose of the present paper is to predict the accurate residual stress of SCM440 high strength steel using the Kendall model which was adopted by ASME Code. Hydraulic pressure process was applied and thick-walled cylinders were autofrettaged up to 30% overstrain levels. Electro polishing was performed to get more accurate data. Residual stresses were measured by X-ray diffraction method. The autofrettaged surface which was plastically deformed analyzed using a scanning electron microscope(SEM). Although there were some differences in measured residual stress and numerical, there is a tendency to agree.

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