• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.179-180
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• 2006

Densification behavior of various metal and ceramic powder was investigated under cold compaction. The Cap model was proposed based on the parameters obtained from axial and radial deformation of sintered metal powder compacts under uniaxial compression and volumetric strain evolution. For ceramic powder, the parameters were obtained from deformation of green powder compacts under triaxial compression. The Cap model was implemented into a finite element program (ABAQUS) to compare with experimental data for densification behavior of various metal and ceramic powder under cold compaction.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.4
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• pp.333-339
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• 2008

Densification behavior of copper powder was investigated to study the effect of an aluminum mold under warm pressing. The low flow stress of an aluminum mold is appropriate to apply hydrostatic stress to powder compacts during compaction under high temperature. The suggested powder metallurgy process is very useful under high temperature since copper powder compacts have higher relative density over axial stress of 100 MPa and show more homogeneity as compared with conventional warm pressing. Elastoplastic constitutive equation proposed by Shima and Oyane was implemented into a finite element program (ABAQUS) for densification behavior under warn pressing by using a metal mold. Finite element results agreed well with experimental data for densification and deformation of copper powder compacts in the mold.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.2 s.173
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• pp.394-402
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• 2000

Densification behavior of titanium alloy powder was investigated under hot isostatic pressing at various pressures and temperatures. Uniaxial creep responses of a dense specimen were also obtained at high temperatures. The densification model of Abouaf and co-workers was implemented into a Finite element program (ABAQUS) to compare with experimental data for titanium alloy powder. The agreements between finite element calculations and experimental data for deformation and densification of titanium alloy powder were good during hot isostatic pressing.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.363-368
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• 2000

Densification, grain growth, and phase transformation of nanocrystalline ceramic powder were investigated under pressureless sintering, sinter forging, and hot pressing. A constitutive model for densification of nanocrystalline ceramic powder was proposed and implemented into a finite element program (ABAQUS). A grain growth model was also proposed by including the effect of applied stress on grain growth when phase transformation occurs. Finite element results by using the proposed models well predicted densification behavior, deformation, and grain growth of nanocrystalline titania powder during pressureless sintering, sinter forging, and hot pressing.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1352-1357
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• 2003

The effect of the metal mold on densification behavior of stainless steel 316L powder was investigated under warm isostatic pressing with metal mold. We use lead as metal mold and obtain experimental data of metal mold property. To simulate densification of metal powder, the elastoplastic constitutive equation proposed by Shima and Oyane was implemented into a finite element program (ABAQUS) under warm die pressing and warm isostatic pressing with metal mold. Finite element results were compared with experimental data for densification and deformation of metal powder under warm isostatic pressing and warm die pressing.

• Transactions of Materials Processing
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• v.16 no.3 s.93
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• pp.210-214
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• 2007

Manufacturing bulk nanostructured materials with least grain growth from initial powders is challenging because of the bottle neck of bottom-up methods using the conventional powder metallurgy via compaction and sintering. In the study, densification behavior of nano Cu powders during pressureless sintering was investigated using an in-situ optical dilatometer technique. The initial heating and steady temperature stages during the sintering of nano Cu powder compacts were observed. At the initial heating stage, the powder compact has many porosities and full densification needs high temperature and/or high pressure sintering. In the experimental analysis, changes in geometry and density were measured and discussed for optimal consolidation and densification by the in-situ optical dilatometer.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.282-283
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• 2006

Densification behavior of nano-agglomerate powder during pressureless sintering of Fe-Ni nanopowder was investigated in terms of diffusion kinetics and microstructural development. To understand the role of agglomerate boundary for sintering process, densification kinetics of Fe-Ni nano-agglomerate powder with different agglomerate size was investigated. It was found that activation energy for densification was lower in the small-sized agglomerate powder. The increase in the volume fraction of inter-agglomerate boundary acting as high diffusion path might be responsible for the enhanced diffusion process.

• Journal of Powder Materials
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• v.16 no.2
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• pp.85-90
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• 2009

Magnesium and its alloys are attractive as light weight structural/functional materials for high performance application in automobile and electronics industries due to their superior physical properties. In order to obtain high quality products manufactured by the magnesium powders, it is important to control and understand the densification behavior of the powders. The effect of the sheath surrounding the magnesium powders on the plastic deformation and densification behavior during equal channel angular pressing was investigated in the study by experimental and the finite element methods. A modified version of Lee-Kim's plastic yield criterion, notably known as the critical relative density model, was applied to simulate the densification behavior of magnesium powders. In addition, a new approach that extracts the mechanical characteristics of both the powder and the matrix was developed. The model was implemented into the finite element method, with which powder compaction under equal channel angular pressing was simulated.

• Journal of the Korean Ceramic Society
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• v.32 no.1
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• pp.51-56
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• 1995

Variation of sintered density of BaTiO3 powder calcined at 120$0^{\circ}C$ and 135$0^{\circ}C$ was investigated with respect to the grain growth behavior. It was found that BaTiO3 powder, which was calcined at 120$0^{\circ}C$, showed abnormal grain growth behavior during sintering process. At initial stage of sintering process, the densification rate of specimen was accelerated with rapid grain growth caused by the abnormal grain growth. But with the increase of sintering time, abnormally grown grain met each other and the density of specimen decreased drastically due to coalescence of pores located in triple junction. On the contrary, BaTiO3 powder calcined at 135$0^{\circ}C$ showed normal grain growth behavior and gradually densified with the increase of sintering time.

• Proceedings of the KSME Conference
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• 2005.11a
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• pp.120.2-120.2
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• 2005