• Title, Summary, Keyword: Microstructure

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The Evaluation of Mechanical properties on the Changes of Microstructure for Titanium Alloy (Ti-6Al-4V) (티타늄 합금(Ti-6Al-4V)의 조직변화에 따른 기계적 특성 평가)

  • Kwon, Jae-Do;Bae, Yong-Tak;Choi, Sung-Jong
    • Proceedings of the KSME Conference
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    • pp.135-140
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    • 2000
  • The characteristics of mechanical behavior were estimated for Ti-6Al-4V alloy with four kinds of microstructure prepared with heat treatments. For this study, impact test, tensile test and fatigue crack growth test were performed, and then compared mechanical properties on the four microstructures. Furthermore, for quantitative evaluation, fractal dimensions of crack pass were obtained using the box counting method. The main results obtained are summarized as follows. (1) The microstructures exhibited equiaxed microstructure, bimodal-microstructure and lamellar microstructure by heat treatment. (2) The impact absorbed energy and elongation is superior in the bimodal-microstructure, and the hardness and tensile strength are superior in the lamellar microstructure. (3) The fatigue crack growth rate is similar to all microstructures in the low ${\Delta}K$ region. The fatigue crack growth rate of equiaxed microstructure is fastest, and that of lamellar microstructure is lowest in the high ${\Delta}K$ region. (4) The fractal dimension D of lamellar microstructure is higher then that of the equiaxed microstructure and bimodal microstructure.

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Research Progress in SiC-Based Ceramic Matrix Composites

  • Dong, Shaoming;Wang, Zhen;Zhou, Haijun;Kan, Yan-Mei;Zhang, Xiangyu;Ding, Yusheng;Gao, Le;Wu, Bin;Hu, Jianbao
    • Journal of the Korean Ceramic Society
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    • v.49 no.4
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    • pp.295-300
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    • 2012
  • SiC-based ceramic matrix composites show many advantages over their monolithic ceramic counterparts, which makes them potential candidates for applications in various fields. Depending strongly on the chemical composition and microstructure of the fiber reinforcement, matrix as well as the fiber/matrix interphase in the material, the properties of ceramic matrix composites(CMCs) are highly tailorable. In this paper, the latest progresses in the interphase design, matrix modification and fiber reinforcement decoration of CMCs are reviewed, their effects on the properties of the CMCs are introduced.

The Investigation of Microstructure of Electro-deposited Layer for the Corrosion Resistance on Sheet Steel (강판의 부식방지를 위한 도금층 조직관찰)

  • 김인수;이세광
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • pp.224-227
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    • 1997
  • In Ni and Zn plating, microstructure and corrosion behavior of electrodeposits with various electroplating condition were investigated. Optical microstructure, SEM images and polarization curves of electrodeposits are different with plating time and temperature.

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Micro Patterning of Roll using Fast Tool Servo System (FTS시스템을 이용한 룰외 미세 패턴 가공)

  • Lu, Hong;Choi, Soo-Chang;Lee, Sang-Min;Park, Chun-Hong;Lee, Deug-Woo
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.10 no.6
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    • pp.22-26
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    • 2011
  • The application of fast tool servo (FTS) for diamond turning has been investigated extensively. This paper focuses on the fabrication of the sinusoidal microstructure on a roller, which generated by a piezoelectric-assisted FTS. The influence of the machining parameters on the microstructure configuration was investigated. The experiment results point out that the configuration of the machined microstructure depends mainly on the spindle speed, the diameter of roller and the driving frequency of FTS. The calculation method of the microstructure dimension was reported. The turning test results show that the diamond tool can be moved up to 1kHz without any reinjected vibration in the machining and the peak-to-valley amplitude of the machined sinusoidal microstructure is about 12<${\mu}m$

PREDICTION OF MICROSTRUCTURE EVOLUTION AND HARDNESS DISTRIBUTION IN THE WELD REPAIR OF CARBON STEEL PIPELINE

  • Li, Victor;Kim, Dong
    • Proceedings of the KWS Conference
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    • pp.205-210
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    • 2002
  • This article presents an integrated modeling approach for coupled analysis of heat transfer and microstructure evolution in welding carbon steel. The modeling procedure utilizes commercial [mite element code ABAQUS/Standard as the platform for solving the equation of heat conduction. User subroutines that implement computational thermodynamics and kinetics models are integrated with the FEA code to compute the transient microstructure evolution. In this study, the integrated models are applied to simulate the hot-tap repair welding of carbon steel pipeline. Microstructural components are treated as user output variables. Based on the predicted microstructure and cooling rates, hardness distributions in the welds were also predicted. The predicted microstructure and hardness distribution were found in good agreement with metallographic examinations and hardness measurements. This study demonstrates the applicability of computational models for the development of welding procedure for in-service pipeline repair.

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The Influence of Effective Strain on the Globular Microstructure by SIMA Process for Semi-Solid Forging (반용융 단조를 위한 SIMA 공정에서 유효 변형률이 구상화 조직에 미치는 영향)

  • Park, H.J.;Lee, B.M.;Park, J.C.
    • Journal of the Korean Society for Precision Engineering
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    • v.14 no.9
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    • pp.45-51
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    • 1997
  • For semi-solid forging, it is necessarily required to prepare a workpiece with globular microstructure. Among several processes to obtain golbular microstructure, SIMA process is very simple and advantageous with respect to equipment. This paper presents the influence of effective strain on the globularization with aluminium 2024 alloy in cold working stage by SIMA process. Upsetting and forward extrusion are tested for cold working and induction heating is also carried out for reheating to obtain golbular microstructure. Microstructure is observed with an optical microscope. And finite element simulations to obtain effective strain in cold working stage are performed by using commercial finite element code, DEFORM.

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The Evaluation of Mechanical Properties on the Changes of Microstructure for Titanium Alloy (Ti-6Al-4V) (티타늄 합금(Ti-6Al-4V)의 조직변화에 따른 기계적 특성 평가)

  • Gwon, Jae-Do;Bae, Yong-Tak;Choe, Seong-Jong
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.26 no.4
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    • pp.609-616
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    • 2002
  • The characteristics of mechanical behavior are investigated for Ti-6Al-4V alloy. Four kinds of the specimens are prepared under different heat treatments in order to produce different microstructures. In the present investigations, impact, tensile and fatigue crack growth tests are performed for each test specimen. The results obtained through the investigations are compared. Additionally fr actal dimensions of crack pass are obtained using the box counting method. The results are, 1) the microstructures shows as equiaxed, bimodal and Widmanstatten microstructures respectively, 2) the impact energy and elongation are superior fur the bimodal microstructure, and the hardness and tensile strength are superior fur the Widmanstatten microstructure, 3) the fatigue crack growth rate is similar to all microstructures in low ΔK region while that of equiaxed microstructure is the largest, and that of Widmanstatten microstructure is the lowest in high ΔK region respectively, 4) the fractal dimension D of Widmanstatten microstructure shows higher value than that of the equiaxed and bimodal microstructures under 200 magnification view of the SEM micrographs.

Sliding Wear Behavior of AISI 52100 Steel with Pearlitic and Bainitic Microstructures (미세조직 변화에 따른 AISI 52100 강의 미끄럼마멸 특성)

  • Yoon, N.;Kim, Y.S.
    • Transactions of Materials Processing
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    • v.20 no.7
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    • pp.479-484
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    • 2011
  • Dry sliding wear behavior of AISI 52100 steel that has a pearlite or bainite microstructure was characterized to explore the effect of microstructure on the wear of the steel. Isothermal heat treatments were employed to obtain the different microstructures. Pin-on-disk type wear tests of the steel disk were performed at loads of 25~125N in air against an alumina ball. Sliding speed and wear distance used were 0.1m/sec and 300m, respectively. Worn surfaces, wear debris and cross-sections of the worn surfaces were examined with SEM to investigate the wear mechanism of the steel. Hardness of the steel was also evaluated. Wear rate of the steel was correlated with the hardness and the microstructure. On the whole, wear resistance increased with an increase in hardness. However, the pearlite microstructure showed superior wear resistance as compared to the bainite microstructure with a similar hardness. The effect of the microstructure on the wear rate was attributed to the morphological differences of the carbide in the microstructure, which was found to have a significant effect on strain hardening during the wear.

Lattice based Microstructure Evolution Model for Monte Carlo Finite Element Analysis of Polycrystalline Materials (격자식 미세구조 성장 모델을 이용한 다결정 박막 소재의 유한 요소 해석)

  • 최재환;김한성;이준기;나경환
    • Transactions of Materials Processing
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    • v.13 no.3
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    • pp.248-252
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    • 2004
  • The mechanical properties of polycrystalline thin-films, critical for Micro-Electro-Mechanical Systems (MEMS) components, are known to have the size effect and the scatter in the length scale of microns by the numbers of intensive investigation by experiments and simulations. So, the consideration of the microstructure is essential to cover these length scale effects. The lattice based stochastic model for the microstructure evolution is used to simulate the actual microstructure, and the fast and reliable algorithm is described in this paper. The kinetics parameters, which are the key parameters for the microstructure evolution based on the nucleation and growth mechanism, are extracted from the given micrograph of a polycrystalline material by an inverse method. And the method is verified by the comparison of the quantitative measures, the number of grains and the grain size distribution, for the actual and simulated microstructures. Finite element mesh is then generated on this lattice based microstructure by the developed code. And the statistical finite element analysis is accomplished for selected microstructure.