• 제목/요약/키워드: grain growth behavior

검색결과 284건 처리시간 0.025초

STS316L의 고온피로균열에 미치는 인장유지시간의 효과 및 결정립크기에 따른 크리프 거동에 관한 연구 (The Effect of Tensile Hold time on the Fatigue Crack Propagation Property and Grain Size on the Creep Behavior in STS 316L.)

  • 김수영
    • 한국공작기계학회:학술대회논문집
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    • 한국공작기계학회 2000년도 춘계학술대회논문집 - 한국공작기계학회
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    • pp.373-378
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    • 2000
  • The heat resistant material, in service, may experience static loading, cyclic loading, or a combination of two. An experimental study of crack growth behavior of STS 316L austenitic stainless steel under fatigue, and creep-fatigue loading conditions were carried out on compact tension specimens at various tensile hold times. In the crack growth experiments under hold times. In the crack growth experiments under hold time loading conditions, tensile hold times were ranged from 5 seconds to 100 seconds and its behavior was characterized using the $\Delta$K parameter. The crack growth rates generally increase with increasing hold times. However in this material, the trend of crack growth rates decreases with increasing hold times for short hold time range relatively. It is attributed to a decline in the cyclic crack growth rate as a result of blunting at the crack tip by creep deformation. The effect of grain size on the creep behavior of STS 316L was investigated. Specimens with grain size of 30, 65 and 125${\mu}{\textrm}{m}$ were prepared through various heat treatments and they were tested under various test conditions. The fracture mode of 316L changed from transgranular to intergranular with increasing grain size.

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마그네슘의 결정립 성장과 집합조직: 상장모델 계산 (Grain Growth and Texture Evolution of Mg: Phase Field Modeling)

  • 김동욱;차필령
    • 한국분말재료학회지
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    • 제18권2호
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    • pp.168-171
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    • 2011
  • We investigate grain growth behavior of poly-crystalline Mg sheet having strong basal fiber texture using phase field model for grain growth and micro-elasticity. Strong initial basal texture was maintained when external load was not imposed, but was weaken when external biaxial strain was imposed. Elastic interaction between elastic anisotropy of Mg grain and external load is the reason why texture evolution occurs.

SiC 휘스커 보강 알루미나 복합재료에서 Slow Crack Growth 현상의 직접관찰 연구 (In Situ Observation of Slow Crack Growth in a Whisker-Reinforced Alumina Matrix Composite)

  • 손기선;김우상;이성학
    • 한국세라믹학회지
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    • 제33권2호
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    • pp.203-213
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    • 1996
  • In this study the subcritical crack growth behavior in an Al2O3-SiCw composite has been investigated using in situ fracture technique of applied moment double cantilever beam (AMDCB) specimens indside an SEM. This technique allows the detailed observation of whisker and grain bridging in the crack wake region. The experimental results indicated that the KI-a curve was deviated from the conventional powder law form and that the existed a region where the rate of microcrack growth was decreased with increasing the externally applied stress intensity factor. This behavior could be explained by arising crack growth resistance i.e. R-curve behavior which was associated with crack shielding due to whisker and grain bridging. The R-curve was also analyzed from the KI-a curve data in order to quantify the bridging effect in the Al2O3-SiCw composite.

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결정립 성장을 고려한 초소성 성형공정의 유한요소해석(I) (Finite Element Analysis of Superplastic Forming Processes Considering Grain Growth (I))

  • 김용관;송재선;김용환
    • 소성∙가공
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    • 제21권3호
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    • pp.151-159
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    • 2012
  • Finite element simulations were conducted to investigate the influence of grain growth in the superplastic blow forming process. A microstructure-based constitutive model considering grain growth effects is proposed and used in the simulations. Also, a grain growth rate equation accounting for both static and dynamic grain growth is implemented. The simulations were made using a 2D plane-strain model for constrained blow forming and an axisymmetric model for free bulging. These two models showed different features during the forming stages. However, the forming pressure-time curve and the thickness distribution obtained by both simulations explained well the deformation hardening induced by the grain growth during superplastic forming. This study shows that grain growth is an important factor in determining the material behavior during superplastic deformation.

탄화물첨가 TiC기지 서멧의 입성장 거동 (Behaviors of Grain Growth in Carbide Added TiC Matrix Cermets)

  • 신순기;이준희;이상화
    • 한국재료학회지
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    • 제12권10호
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    • pp.825-830
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    • 2002
  • The growth rate of solid grains in TiC-XC-2vol% and TiC-XC-30vo1% Ni cermets, where X=Zr, W or Mo, was fitted to an equation of the form $d^3$-$do^3$=Kt. The grain growth behavior during liquid phase sintering at 1673K decreased markedly with addition of $Mo_2$C or WC and increased with addition of ZrC. The contiguity ratio was greater in the alloys with smaller growth rate constant and decreased with increasing Ni content in the $TiC-Mo_2$C-Ni cermet. The grain growth mechanism could be explained by the effect of contiguous grain boundaries in restricting the overall grain growth.

지르코니아 분말 성형체의 고온 치밀화 거동과 결정립 성장 (Densification behavior and grain growth of zirconia powder compacts at high temperature)

  • 김홍기;김기태
    • 대한기계학회논문집A
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    • 제21권8호
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    • pp.1175-1187
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    • 1997
  • Densification behavior and grain growth of zirconia powder compacts are investigated under high temperature. Experimental data are obtained for zirconia powder under pressureless sintering, sinter forging and hot isostatic pressing. The constitutive equations by Kwon et al. are used for diffusional creep and grain growth. The constitutive equations by McMeeking and co-workers are also included to study the effect of power-law creep. These constitutive equations are implemented into a finite element program (ABAQUS) to investigate the friction effect during sinter forging and the canning effect during hot isostatic pressing. The agreements between experimental data and finite element results are very good in pressureless sintering and hot isostatic pressing, but not as good in sinter forging.

Carbide Grain Growth in Cemented Carbides

  • Mannesson, Karin;Agren, John
    • 한국분말야금학회:학술대회논문집
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    • 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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    • pp.336-337
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    • 2006
  • During sintering of cemented carbides abnormal grain growth is often observed but cannot be understood from the classical LSW-theory. A model based on 2-D nucleation of new crystalline layers and a grain-size distribution function is formulated and the equations are solved numerically. Experimental studies and computer simulations show that the initial grain size distribution has a strong effect on the grain growth behavior. For example, a fine-grained powder can grow past a coarser powder.

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상온분사분말공정에 의해 SrTiO3 (100), (110) Seed에 코팅된 BaTiO3의 고온 성장 거동 분석 (High Temperature Grain Growth Behavior of Aerosol Deposited BaTiO3 Film on (100), (110) Oriented SrTiO3 Single Crystal)

  • 임지호;이승희;김기현;지성엽;정승운;박춘길;정한보;정대용
    • 한국재료학회지
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    • 제29권11호
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    • pp.684-689
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    • 2019
  • Single crystals, which have complexed composition, are fabricated by solid state grain growth. However, it is hard to achieve stable properties in a single crystal due to trapped pores. Aerosol deposition (AD) is suitable for fabrication of single crystals with stable properties because this process can make a high density coating layer. Because of their unique features (nano sized grains, stress inner site), it is hard to fabricate single crystals, and so studies of grain growth behavior of AD film are essential. In this study, a $BaTiO_3$ coating layer with ${\sim}9{\mu}m$ thickness is fabricated using an aerosol deposition method on (100) and (110) cut $SrTiO_3$ single crystal substrates, which are adopted as seeds for grain growth. Each specimen is heat-treated at various conditions (900, 1,100, and $1,300^{\circ}C$ for 5 h). $BaTiO_3$ layer shows different growth behavior and X-ray diffraction depending on cutting direction of $SrTiO_3$ seed. Rectangular pillars at $SrTiO_3$ (100) and laminating thin plates at $SrTiO_3$ (110), respectively, are observed.

PVT(Physical Vapor Transport) 법으로 AlN 결정 성장에서 결정립의 성장 거동에 관한 연구 (A study on the crystallite growth behavior in AlN crystal grown by PVT (Physical Vapor Transport) method)

  • 강승민
    • 한국결정성장학회지
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    • 제26권4호
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    • pp.135-138
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    • 2016
  • AlN 결정을 PVT(물리 기상 이동법, Physical Vapor Transport) 법으로 성장함에 있어 결정립의 성장 거동을 관찰하였다. 작은 AlN 결정립이 성장한 이후 결정립들은 이웃한 결정립과 합쳐지면서 성장하는 거동을 보였다. 이를 실체현미경을 이용하여 관찰한 결과를 보고하고자 한다.

Co 액상 내에 공존하는 (Ti,W)(C,N)과 WC입자의 성장 거동 (Growth Behavior of (Ti,W)(C,N) and WC grains in a Co Matrix)

  • 이보아;윤병권;강석중
    • 한국분말재료학회지
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    • 제11권2호
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    • pp.165-170
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    • 2004
  • Growth behavior of two different types of grains, faceted and rounded, in a liquid matrix has been studied in the (75WC-25TiCN)-30Co system. Powder samples were sintered above the eutectic temperature for various times under a carbon saturated condition. (Ti,W)(C,N) grains with a rounded shape and WC grains with a faceted shape coexisted in the same Co based liquid. With increasing sintering time, the average size of (Ti.W)(C,N) grains increased continuously and very large WC grains appeared. The growth of rounded (Ti,W)(C,N) grains followed a cubic law, r^3-r^3_0$=kt, where r is the average size of the grains, $r_0$ the initial average size, k the proportionality constant and t the sintering time. indicating a diffusion-controlled growth. On the other hand, the growth of the faceted WC grains resulted in a bimodal grain size distribution, showing an abnormal grain growth. These observations show that the growth behavior of different types of grains is governed by their shape, faceted or rounded, even in the same liquid matrix.