Thermophysical properties effects on segregation during solidification

Azouni, M.A.; Casses, P.

doi:10.1016/s0001-8686(97)00002-x

Cited by 37 publications

(28 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Such small particles are supposed to float on the top of the molten bath even if their density is relatively higher than that of the liquid matrix. This issue was indeed of paramount importance in micron-sized particle reinforced composites but it is felt that in nano-reinforced materials, other effects such as those induced by extensive surface tension play a much more important role [56].…”

Section: Liquid Processesmentioning

confidence: 99%

Metal Matrix Composites Reinforced by Nano-Particles—A Review

Casati

Vedani

2014

Metals

879

317

View full text Add to dashboard Cite

Metal matrix composites reinforced by nano-particles are very promising materials, suitable for a large number of applications. These composites consist of a metal matrix filled with nano-particles featuring physical and mechanical properties very different from those of the matrix. The nano-particles can improve the base material in terms of wear resistance, damping properties and mechanical strength. Different kinds of metals, predominantly Al, Mg and Cu, have been employed for the production of composites reinforced by nano-ceramic particles such as carbides, nitrides, oxides as well as carbon nanotubes. The main issue of concern for the synthesis of these materials consists in the low wettability of the reinforcement phase by the molten metal, which does not allow the synthesis by conventional casting methods. Several alternative routes have been presented in literature for the production of nano-composites. This work is aimed at reviewing the most important manufacturing techniques used for the synthesis of bulk metal matrix nanocomposites. Moreover, the strengthening mechanisms responsible for the improvement of mechanical properties of nano-reinforced metal matrix composites have been reviewed and the main potential applications of this new class of materials are envisaged.

show abstract

Section: Liquid Processesmentioning

confidence: 99%

Metal Matrix Composites Reinforced by Nano-Particles—A Review

Casati

Vedani

2014

Metals

879

317

View full text Add to dashboard Cite

show abstract

“…[9,10,11] For the subject at hand, the situation can be summarized by considering that the excess free energy of two planar solid/liquid interfaces deviates from 2␥ sl , as the thickness of the liquid between the two interfaces approaches atomic dimensions. Here, we define the interface energies (e.g., the solid/liquid interfacial energy (␥ sl )) as those for isolated interfaces, i.e., for interfaces between two semi-infinite phases.…”

Section: Introductionmentioning

confidence: 99%

Last-stage solidification of alloys: Theoretical model of dendrite-arm and grain coalescence

Rappaz

Jacot

Boettinger

2003

Metall Mater Trans A

265

185

View full text Add to dashboard Cite

Hot tearing in castings is closely related to the difficulty of bridging or coalescence of dendrite arms during the last stage of solidification. The details of the process determine the temperature at which a coherent solid forms; i.e., a solid that can sustain tensile stresses. Based on the disjoining-pressure concept used in fluid dynamics, a theoretical framework is established for the coalescence of primaryphase dendritic arms within a single grain or at grain boundaries. For pure substances, approaching planar liquid/solid interfaces coalesce to a grain boundary at an undercooling (⌬T b ), given bywhere ␦ is the thickness of an isolated solid-liquid interface, and ⌬⌫ b is the difference between the grain-boundary energy, ␥ gb , and twice the solid/liquid interfacial energy, 2␥ sl , divided by the entropy of fusion. If ␥ gb Ͻ 2␥ sl , then ⌬T b Ͻ 0 and the liquid film is unstable. Coalescence occurs as soon as the two interfaces get close enough (at a distance on the order of ␦ ). This situation, typical of dendrite arms belonging to the same grain (i.e., ␥ gb ϭ 0), is referred to as "attractive". The situation where ␥ gb ϭ 2␥ sl is referred to as "neutral"; i.e., coalescence occurs at zero undercooling. If ␥ gb Ͼ 2␥ sl , the two liquid/solid interfaces are "repulsive" and ⌬T b Ͼ 0. In this case, a stable liquid film between adjacent dendrite arms located across such grain boundaries can remain until the undercooling exceeds ⌬T b . For alloys, coalescence is also influenced by the concentration of the liquid film. The temperature and concentration of the liquid film must reach a coalescence line parallel to, but ⌬T b below, the liquidus line before coalescence can occur. Using one-dimensional (1-D) interface tracking calculations, diffusion in the solid phase perpendicular to the interface (backdiffusion) is shown to aid the coalescence process. To study the interaction of interface curvature and diffusion in the liquid film parallel to the interface, a multiphase-field approach has been used. After validating the method with the 1-D interface tracking results for pure substances and alloys, it is then applied to twodimensional (2-D) situations for binary alloys. The coalescence process is shown to originate in small necks and involve rapidly changing liquid/solid interface curvatures.

show abstract

“…The interaction between the embedded particle and the front determines the microstructural and hence strength properties of the solidified material. When a particle is approached by an advancing solidification front, the fate of the particle is determined by the forces that the solid and melt impose on the particle [1][2][3][4][5][6][7][8][9][10][11][12][13].…”

Section: Introductionmentioning

confidence: 99%

“…Conventionally, it is conjectured that there is a thermomolecular interaction force which acts to push the particle away from the front [3][4][5][6][7][8][9][10][11][12], and there is an opposing drag force that pushes the particle towards the front [3][4][5][6][7][8][9][10][11][12][13]. Recently, it has been postulated that there is also a thermal force [6] that can be repulsive or attractive depending on the thermal properties of the melt and particle.…”

Section: Introductionmentioning

confidence: 99%

“…Our purpose in this paper is to compute the drag force on the particle in this limited situation to establish the functional form of the dependence of the drag force on two parameters, namely the gap thickness between the particle and the thermal conductivities of the particle and melt. It is now well established that the drag is dependent on the thermal conductivity differences of the particle and the melt [8,10,11], as well as on the distance between the particle and the interface [3][4][5][6][7][8][9][10][11][12][13]. Analytic expressions have been advanced in these papers to account for both of these dependencies.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation