A method of fabricating articles, such as prototype parts and prototype tooling for injection molding, is disclosed. The method begins with the fabrication of the article in a "green" state by the selective laser sintering, or another additive thermal process, applied to a composite powder, preferably a powder of metal particles coated with a thermoplastic polymer. Both the green article and also an aqueous emulsion of a thermosetting material are then preheated to a temperature below the glass transition temperature of the thermoplastic polymer, and the green article is then infiltrated with the aqueous emulsion. The thermosetting material may be a thermosetting polymer with an appropriate cross-linking agent, or may be a cross-linking agent that will react with the thermoplastic binder polymer. After infiltration, the article is dried, and a rigid skeleton of a thermosetting material is now present within the structure of the article. Further processing may now be performed. The article may be heated beyond the decomposition temperature of the polymers so as to drive off the polymer and sinter the metal particles to one another; alternatively, a resin may be added to the article to form a metal-polymer composite article. High strength articles may thus be formed in a manner which preserves the dimensional accuracy of the article relative to its CAD representation.