Percolation and Universal Scaling in Composite Infiltration Processing

Abstract

Supplementary Material Available OnlineComposite materials are often made by infiltration, that is, by injecting a liquid matrix between packed solid fibers or particles. We give here direct proof that molten copper, slowly infiltrated into a broad spectrum of preforms, displays in initial phases of the process universal scaling and fractal geometric features that are characteristic signatures of percolation-dominated flow. Implications are that the microstructure of infiltrated composite materials can develop over length scales that far exceed the average preform pore size, and that network models are pertinent in the simulation of composite infiltration processing.

Infiltration of tin bronze into alumina particle beds: influence of alloy chemistry on drainage curves

“…In a recent article, we have brought to light the role of percolation in initial phases of slow, gradual, pressure infiltration of several different alumina or carbon preforms with pure molten copper [33]. This contribution is an extension of that work to tin bronze : we present here drainage curves that quantify the wetting during infiltration of porous Al2O3 preforms by Cu-Sn molten alloys, covering the entire alloy spectrum from pure Cu to pure Sn.…”

“…Full infiltration (meaning S = 1) is taken to occur when, within uncertainty, the graphite plunger no longer moves after the pressure is increased, indicating that all available pores within the preform have been invaded. This procedure permits to trace the entire drainage curve after one single infiltration experiment [26,33]. Two custom-built devices were also incorporated to provide rotative and vibrative motion of the plunger.…”

“…Continuous infiltration -A detailed description of infiltration apparatus characteristics and of the experimental procedure can be found in Refs [26,33,37]. In a few words, a CIPed preform is placed underneath a slug of metal inside a cylindrical alumina crucible in a pressure infiltration apparatus.…”

“…The metal/pore relative distribution and the metal fractal dimension were then measured using thresholded images from the observed two-dimensional metallographic cuts, as in Ref. [26,33], by means of the box counting method (using the function "Fractal box counter" of ImageJ, U. S. National Institutes of Health, Bethesda, Maryland, USA). In this method, the fractal dimension D is computed from the relation N(h) ~ h -D , where N(h) is the number of boxes of linear size h necessary to cover a data set of points distributed in a two-dimensional plane.…”

“…Various methods have nonetheless been developed to enable this [5,8,11,18,[22][23][24][25][26][31][32][33][34]. We use here an apparatus that tracks, dynamically and with high precision, the volume of metal that has entered a porous solid preform (as is practiced at room temperature in a mercury porosimeter) as a function of pressure and time, thus providing entire drainage curves characteristic of a given system in one, single, infiltration experiment [26,[31][32][33]. The apparatus comprises, in its current configuration, a custom-designed optics-based system capable of measuring the displacement of a graphite plunger that floats atop the surface of a liquid metal bath, which is pushed by pressurized gas to invade open pores of a preform situated below the metal surface [26].…”