Computer simulation of solution and growth processes during the initial stage of liquid phase sintering of tungsten heavy metal

Abstract

In the initial stage of liquid phase sintering, particle dissolution and growth processes occur. The melting matrix penetrates the solid particle agglomerates. A fraction of the particles dissolves in the liquid matrix phase and the original powder size will initially be reduced. At the same time the agglomerates of particles are effectively separated. In a second stage larger particles grow in equilibrium with the matrix, whilst smaller, pure particles dissolve into the matrix and the mean particle size increases. When an equilibrium is reached, the solid particles start to grow in the liquid matrix phase in accordance with the ripening process. The initial stages of liquid phase sintering have been investigated by short time sintering under microgravity and are presented in a series of micrographs. Mathematical models for the 3 stages have been developed. Computer simulations of these different stages in the solution and growth processes have been used to visualise the change in particle size distribution.

Microstructural evolution during the infiltration of boron carbide with molten silicon

“…14,15 Different mechanisms have been put forward in the literature in order to explain this microstructural feature. 11,14,[16][17][18][19][20][21][22] The formation of the core-rim structure in a solid-liquid system is attributed to the partial dissolution of original particles in the liquid and precipitation of a new solid phase at the surface of the initial particles.…”

Tungsten grain separation during initial stage of liquid phase sintering

“…In a series of papers [8][9][10][11] the penetration of the molten W/Ni/Fe matrix into the tungsten grains and agglomerates has been treated by the authors. This paper will analyse and present a theoretical explanation to the mechanisms behind the separation and dispersion of the tungsten grains.…”

Nd2Fe14B: (Nd1-x Dyx)2 Fe14B CORE-SHELL STRUCTURE FORMATION BY HOT PRESS LIQUID PHASE SINTERING

“…process driven by composition inhomogeneity has been described in other liquid phase sintering processes where the liquid is not initially in equilibrium with the solid. [22,23] The low activation energy for composition homogenization would also seem to be consistent with the rapid decrease in CV with density, resulting in the necessity of using pressure assisted sintering to reduce the time and temperature required for consolidation in an attempt to form the Dy rich shell-Nd rich core microstructure.…”