Computer simulation of free settling and skeletal settling during liquid phase sintering

In recent years, a range of computer simulation models leading to a better understanding of liquid phase sintering phenomena, have been developed with the aim of simulating the detailed evolution of microstructure during grain growth. Some liquid phase sintered materials show both macrostructural and microstructural effects associated with gravity force. Therefore we will develop a numerical procedure for the estimation of how much gravity will influence domain (two-dimensional particle representation) growth, domain boundary migration and solid skeleton formation due to gravity induced segregation during liquid phase sintering. The method used for the simulation of a gravity field will be based on the settling procedure. Gravity induced settling will be separated into two stages - Free Settling and Skeletal Settling. Isolated solid phase domains fall under gravity and slide down over the already settled domains (free settling). During settling they make point contacts with each other. Necks between them then form and start to grow until the equilibrium dihedral angle between the domain boundaries and the liquid is established. Thus a solid skeleton forms and skeletal settling of a connected solid structure takes place. .

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Computer Simulation of Liquid Phase Sintering: Gravity Induced Skeletal Structure Evolution – A Review

Materials Science Forum ◽

10.4028/www.scientific.net/msf.624.19 ◽

2009 ◽

Vol 624 ◽

pp. 19-42

Author(s):

Zoran S. Nikolic

Keyword(s):

Liquid Phase ◽

Solid Phase ◽

Local Equilibrium ◽

Liquid Phase Sintering ◽

Domain Model ◽

Skeletal Structure ◽

Structure Evolution ◽

Time Interval ◽

Extended Model ◽

Solid Skeleton

This paper summarizes and reviews a number of important theoretical and experimental results connected to study of gravitational effects on liquid phase sintering. However, we will also investigate numerically gravity induced skeletal structure evolution during liquid phase sintering. Applying domain methodology, solid skeleton evolution will be introduced by definition of skeleton units determined by equilibrium dihedral angle and formation of large solid skeleton arranged in long chain of connected solid-phase domains. The settling procedure will be simulated by two submodels: free settling model in which solid-phase domains fall under gravity over already settled domains, and extended model in which settled domains continue their motion till they reach a position of their local equilibrium. Three more submodels will be also defined: rearrangement densification model, settling densification model, and Brownian motion model. It will be assumed that under gravity condition Stokes’s law settling usually dominates microstructure formation, where the settling procedure as well as settling time will be used for computation of average migration distance during defined time interval. Thus gravity induced solid-phase domain structure evolution will be simulated by simultaneous computation of displacement of the center of mass. The new methodology will be applied for simulation of microstructural evolution of a regular multi-domain model under gravity and gravity conditions.

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Basic, extended and combined models for computer simulation of liquid phase sintering

Science of Sintering ◽

10.2298/sos0201041n ◽

2002 ◽

Vol 34 (1) ◽

pp. 41-51 ◽

Cited By ~ 6

Author(s):

Zoran Nikolic

Keyword(s):

Computer Simulation ◽

Liquid Phase ◽

Grain Boundary ◽

Boundary Migration ◽

Simulation Method ◽

Liquid Phase Sintering ◽

Grain Boundary Migration ◽

Two Dimensional ◽

Dimensional Modeling ◽

Combined Models

In this study, two-dimensional modeling of microstructural evolution during liquid phase sintering was considered. The simulation method developed is based on basic, extended and combined models defined for diffusion induced grain boundary migration.

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A mathematical approach to Ostwald ripening due to diffusion and deformation in liquid bridge

Science of Sintering ◽

10.2298/sos1303261r ◽

2013 ◽

Vol 45 (3) ◽

pp. 261-271 ◽

Cited By ~ 2

Author(s):

B. Randjelovic ◽

K. Shinagawa ◽

Z.S. Nikolic

Keyword(s):

Liquid Phase ◽

Liquid Bridge ◽

Ostwald Ripening ◽

Solid Phase ◽

Liquid Phase Sintering ◽

Solute Diffusion ◽

Deformation Analysis ◽

Mathematical Approach ◽

Fe Method ◽

Grain Coarsening

From many experiments with mixtures of small and large grains, it can be concluded that during liquid phase sintering, smaller grains partially dissolve and a solid phase precipitates on the larger grains and grain coarsening occurs. The growth rate can be controlled either by the solid-liquid phase boundary reaction or by diffusion through the liquid phase. The microstructure may change either by larger grains growing during the Ostwald ripening process or by shape accommodation. In this study, two-dimensional mathematical approach for simulation of grain coarsening by grain boundary migration based on a physical and corresponding numerical modeling of liquid phase sintering will be considered. A combined mathematical method of analyzing viscous deformation and solute diffusion in liquid bridge between two grains with different sizes will be proposed. The viscous FE method will be used for calculating meniscus of the liquid bridge, with the interfacial tensions taken into consideration. The FE method for diffusion will be also implemented by using the same mesh as the deformation analysis.

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Basic and mixed models for computer simulation of liquid phase sintering of a porous structure

Science of Sintering ◽

10.2298/sos0701003n ◽

2007 ◽

Vol 39 (1) ◽

pp. 3-8 ◽

Cited By ~ 3

Author(s):

Z.S. Nikolic

Keyword(s):

Computer Simulation ◽

Liquid Phase ◽

Porous Structure ◽

Microstructural Evolution ◽

Mixed Models ◽

Liquid Phase Sintering ◽

Two Dimensional ◽

Gravitational Effects ◽

Diffusion Phenomena

A two-dimensional method based on basic and mixed models for simulation of liquid phase sintering of a porous structure will be developed. These models will be tested in order to conduct a study of diffusion phenomena and gravitational effects on microstructural evolution during liquid phase sintering of a W-Ni system.

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Interaction of Components of Co-Sn and Co-Sn-Cu Powder Materials in Liquid Phase Sintering

Materials Science Forum ◽

10.4028/www.scientific.net/msf.943.113 ◽

2019 ◽

Vol 943 ◽

pp. 113-118

Author(s):

Evgeniy Georgiyevich Sokolov ◽

Alexander Vitalyevich Ozolin ◽

Lev Ivanovich Svistun ◽

Svetlana Alexandrovna Arefieva

Keyword(s):

Liquid Phase ◽

Solid Phase ◽

Steel Substrate ◽

Liquid Phase Sintering ◽

Powder Materials ◽

Cu Alloys ◽

Initial Stage ◽

Interaction Of Components ◽

Sintered Alloys ◽

Liquid Tin

The interaction of components and structure formation were studied in liquid phase sintering of Co-Sn and Co-Sn-Cu powder materials. The powders of commercially pure metals were mixed with an organic binder and applied on the steel substrate. Sintering was performed under vacuum at temperatures of 820 and 1100 °C. The structure of sintered alloys was investigated by X-ray diffractometry and electron probe microanalysis, and microhardness (HV0.01) of the structural components was measured. It has been found that the nature of interaction of the liquid tin with the solid phase at the initial stage of sintering affects the formation of structure and porosity of Co-Sn and Co-Sn-Cu alloys considerably. In Co-Sn alloys, diffusion of tin into cobalt particles leads to the formation of intermetallic compounds, which hinders spreading of the liquid phase. This results in a porous defect structure formed in Co-Sn alloys. In Co-Sn-Cu alloys, at the initial stage of sintering the liquid phase enriched with copper is formed that wets the cobalt particles and contributes to their regrouping. As a result of this, materials with minor porosity are formed.

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TEM Analysis of an Alumina Bicrystal Section Using a Fib

Microscopy and Microanalysis ◽

10.1017/s1431927600027707 ◽

2001 ◽

Vol 7 (S2) ◽

pp. 326-327

Author(s):

Jeffrey K. Fairer ◽

N. Ravishankar ◽

Joseph R. Michael ◽

C. Barry Carter

Keyword(s):

Liquid Phase ◽

Mass Transport ◽

Binary Phase Diagram ◽

Boundary Migration ◽

Liquid Phase Sintering ◽

Grain Boundary Migration ◽

Tem Analysis ◽

Sem Image ◽

Polycrystalline Ceramic ◽

Polycrystalline Ceramic Material

Grain boundary migration (GBM) during the sintering and densification of a polycrystalline ceramic material occurs as a result of mass transport across an interface. When there is a liquid film present, either due to additives used for liquid-phase sintering or unavoidable impurities in the material, the mass transport can be visualized in terms of dissolving material from one grain and precipitating it on another. in order to study the effects of crystallography on GBM in the presence of a liquid phase, alumina bicrystals have been fabricated with anorthite (CaA12Si208) glass films at the interface. The alumina-anorthite system in a bicrystal geometry is used because the pseudo-binary phase diagram of the system is well known, the bicrystal geometry allows for control over the original interface misorientation, and the glassy phase of anorthite is the most commonly occurring glass in commercially used alumina.Fig. 1 is a secondary-electron SEM image of an alumina bicrystal recorded using a field-emission SEM (Hitachi S900) operating at 5 kV.

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True Sedimentation and Particle Packing Rearrangement during Liquid Phase Sintering

Materials Science Forum ◽

10.4028/www.scientific.net/msf.534-536.609 ◽

2007 ◽

Vol 534-536 ◽

pp. 609-612

Author(s):

Jong K. Lee ◽

Lei Xu ◽

Shu Zu Lu

Keyword(s):

Liquid Phase ◽

Concentration Gradient ◽

Volume Fraction ◽

Solid Volume Fraction ◽

Liquid Phase Sintering ◽

Particle Packing ◽

Sintering Process ◽

Second Stage ◽

Packing Efficiency ◽

Two Stages

When an alloy such as Ni-W is liquid phase sintered, heavy solid W particles sedimentate to the bottom of the container, provided that their volume fraction is less than a critical value. The sintering process evolves typically in two stages, diffusion-driven macrosegregation sedimentation followed by true sedimentation. During sedimentation, the overall solid volume fraction decreases concurrently with elimination of liquid concentration gradient. However, in the second stage of true sedimentation, the average solid volume fraction in the mushy zone increases with time, and oddly, no concentration gradient is necessary in the liquid zone. In this work, we propose that the true sedimentation results from particle rearrangement for higher packing efficiency.

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Microstructure and Properties of In Situ Fabricated Al-5wt.%Si-Al2O3 Composites

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.567.15 ◽

2012 ◽

Vol 567 ◽

pp. 15-20 ◽

Cited By ~ 3

Author(s):

Ling Cheng ◽

De Gui Zhu ◽

Ying Gao ◽

Wei Li ◽

Bo Wang

Keyword(s):

Shear Strength ◽

Liquid Phase ◽

Solid Phase ◽

Hold Time ◽

Aluminum Matrix ◽

Liquid Phase Sintering ◽

Aluminum Matrix Composites ◽

Matrix Composites ◽

X Ray

Alumina reinforced aluminum matrix composites (Al-5wt.%Si-Al2O3) fabricated by powder metallurgy through hot isotactic pressing were sintered in different processes, i.e. solid and liquid phase sintering. Optical microscopy (OM), X-ray diffraction (XRD), scanning electron microscope (SEM), Energy Dispersive X-ray (EDX) techniques were used to characterize the sintered composites. The effects of solid phase and liquid phase sintering on density, microstructure, microhardness, compression and shear strength were investigated. It was found that in situ chemical reaction was completed in solid phase sintering, but the composites had lower microhardness, comprehension and shear strength due to low density and segregation of alumina and Si particles in microstructure. Segregation of reinforcement particles in solid phase sintering resulted from character of solid reaction and Si diffusion at high temperature over a long hold time.

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