A MICROMECHANISTIC MODEL OF THE COMBINED COMBUSTION SYNTHESIS-DENSIFICATION PROCESS

A series of computer experiments has been conducted in order to study the combined combustion synthesis-densification process, in which a me chanical load is applied to a sample as it undergoes a combustion synt hesis process. The current work is an extension of a theoretical model of the combustion synthesis process that was developed previously.(1. 2) In this work, the appropriate constitutive equations for sample def ormation have been incorporated, in order to account for the pore-volu me change that mag take place when the mechanical load is applied, thu s densifying the sample. It was shown that the brief appearance of a l iquid phase in the combustion wave front provide:, an important opport unity for densification when the self-propagating combustion synthesis process is conducted in conjunction with an applied mechanical load. That is, the concomitant decrease in the (local) total volume fraction of the solid phases-due to the elementary melting and dissolution pro cesses that also occur (locally)-effectively lowered the (local) appar ent yield strength of the sample, thus allowing for the compaction and densification of the sample (i.e., locally). Results indicated that t he mechanical load should be applied at the instant at which the sampl e is ignited, in order to ensure that articles whose density is unifor m throughout the sample can be fabricated, This work provided a more d etailed and quantitative understanding of this unique process for prep aring dense articles by the self-propagating combustion synthesis proc ess. that ist when it is conducted in conjunction with an applied mech anical load.