• Transactions of Materials Processing
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• v.23 no.4
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• pp.231-237
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• 2014

In the current study, a rate-dependent crystal plasticity finite element method (CPFEM) was used to simulate flow stress behavior and texture evolution of a body-centered cubic (BCC) crystalline material during plastic deformation at room temperature. To account for crystallographic slip and rotation, a rate-dependent crystal constitutive law with a hardening model was incorporated into an in-house finite element program, CAMPform3D. Microstructural heterogeneity and anisotropy were handled by assigning a crystallographic orientation to each integration point of the element and determining the stiffness matrix of the individual crystal. Uniaxial tensile tests of single crystals with different crystallographic orientations were simulated to determine the material parameters in the hardening model. The texture evolution during four different deformation modes - uniaxial tension, uniaxial compression, channel die compression, and simple shear deformation - was investigated based on the comparison with experimental data available in the literature.

• Journal of the Korean Ceramic Society
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• v.43 no.3 s.286
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• pp.152-155
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• 2006

Silicon carbide ceramics seeded with 10-30 wt% SiC whiskers are fabricated by hot pressing and annealing. A quantitative texture analysis including calculation of the Orientation Distribution Function (ODF) is used for obtaining the degrees of preferred orientation of the fabricated samples. The microstructure and crystallographic texture are discussed with respect to the effect of ${\beta}-SiC$ whisker seeds on the resulting fracture toughness values. The SEM microstructures and the texture data reveal a correlation between texture and fracture toughness anisotropy.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.463-465
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• 2002

In order to increase perpendicular magnetic anisotropy of magnetic layer and prepare magnetic recording layer with a good quality by epitaxial growth between magnetic layer and, we prepared Co$\_$77/Cr$\_$20/Ta$_3$/Si doublelayer for perpendicular magnetic recording media which was promoted as next generation recording media on slide glass substrate. The thickness of magnetic layer and Underlayer were varied from 20 to 100 nm and 5 to 100 m, respectively. The surface morphology and crystal structure of the CoCrTa/Si film were examined with XRD and AFM. Prepared thin films showed improvement of dispersion angle of c-axis orientation Δ$\theta$$\_$50/ caused by inserting amorphous Si underlayer.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.5
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• pp.1516-1523
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• 1996

The present study is concerned with the development of anisotropy and deformation texture in polycrystals. The individual grain in an aggregate is assumed to experience the viscoplastic dedformation with crystallographic slip that unsure uniquenessof the active slip systems and shearing rate onthese systems. Two different methods for updating the grain orientation are examined. Texture development for some deformation modes such as plane strain compression, uniaxial tension and simple shear are found. Changes in anisotropic flow potential due to texture development during large deformation are also given. Anisotropic behavior of polycrystals with defferent textures are examined.

• Journal of Magnetics
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• v.7 no.3
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• pp.115-125
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• 2002

We proposed a novel method to evaluate the magnetic properties of the initial layer and the columnar structure separately for CoCr-based perpendicular recording media. We show that the thickness of the initial layer and the intrinsic magnetocrystalline anisotropy of columnar structure can be quantitatively evaluated using the plotted product of perpendicular anisotropy to magnetic film thickness versus magnetic film thickness ($K_{u{\bot}}^{ex{p.}}$ $\times$ d$_{mag.}$ vs. d$_{mag.}$ plot). Based on the analyses, it is found that: (1) compared with CoCrPtTa media, CoCrPtB media have relatively thin initial layer, and have fine grains with homogeneous columnar structure with c-plane crystallographic orientation; (2) CoCrPtB media can be grown epitaxially on Ru or CoCr/C intermediate layer, and as the result, the magnetic properties of the media within thin thickness region of d$_{mag.}$ $\leq$ 20 nm is significantly improved; (3) the key issue of material investigation for CoCr-based perpendicular recording media will be focused on how to fabricate c-plane-oriented columnar grains well isolated with nonmagnetic substance in epitaxial-growth media, while maintaining the thermal stability of the media.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1996.03a
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• pp.62-72
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• 1996

A process model is formulated considering the effect of crystallographic testure developed in forming process. The deformation induced plastic anisotropy can be predicted by capturing the evolution of texture during large deformatin in the poly crystaline aggregate. The anisotropic stiffness matrix for the aggregate is derived and implemented in Dulerian finite element code. As an application , the evolution of texture in rolling, drawing and extrusion processes are simulated . The numerical results show good agreement with reported experimental textures.

• Communications of the Korean Mathematical Society
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• v.22 no.3
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• pp.453-464
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• 2007

A computationally efficient numerical scheme is presented for the phase-field model of two-phase systems for anisotropic interfacial energy. The scheme is solved by using a nonlinear multigrid method. When the coefficient for the anisotropic interfacial energy is sufficiently high, the interface of the system shows corners or missing crystallographic orientations. Numerical simulations with high and low anisotropic coefficients show excellent agreement with exact equilibrium shapes. We also present spinodal decomposition, which shows the robustness of the pro-posed scheme.

• Journal of Magnetics
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• v.3 no.2
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• pp.49-54
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• 1998

Dependence of magnetic and magneto-optic properties on composition of amorphous NdFe alloys has been studied to identify a promising magneto-optic recording material in the wavelength of a blue laser beam. From the view point of crystallographic state, perpendicular magnetic anisotropy energy and polar Kerr rotation angle, the Nd-rich region was found to be suitable for the research purpose.

• Transactions of Materials Processing
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• v.5 no.4
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• pp.297-304
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• 1996

A process model is formulated considering the effect of crystallographic texture developed in forming process. The deformation induced plastic anisotropy can be predicted by capturing the evolution of texture during large deformation in the polycrystalline aggregate. The anisotropic stiffness matrix for the aggregate is derived and implemented in Eulerian finite element code using a Consistent Penalty method. As an application the evolution of texture in rolling drawing and extrusion processes are simulated. The numerical results show good agreements with report-ed experimental textures.

• Tunnel and Underground Space
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• v.10 no.1
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• pp.70-79
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• 2000

We carried out NPT-ensemble (constant-number of particles, pressure, and temperature) Molecular Dynamics (MD) simulations for measuring strength anisotropy under uniaxial compressive stress rotated to the crystallographic axes in $\alpha$-quartz. Uniaxial compressive strengths of a single quartz crystal were measured in directions of the a- and c-axis. Measured uniaxial strength of a single quartz crystal was higher in the direction parallel to the c-axis than that measured in the direction normal to the c-axis. However the reverse was found in calculated uniaxial strengths by MD simulation. The contradictive result of strengths was observed in both cases but was found to be different in origin. Strength anisotropy of defectless $\alpha$-quartz crystal in MD simulation is basically caused by structural difference of quartz. By contrast, anisotropy of measured strength in the uniaxial compression test is related to oriented micro-defects developed during crystal growth.