Plastic consolidation of metal matrix composites by pressure cycling

Abstract

Creating metal ceramic composites by plastic deformation driven by compression is the most versatile method as it can nearly preserve the microstructure of the metal phase and a variety of reinforcements and morphologies can be used. The great limitation of this process is that very high pressures are needed for effective consolidation (usually about 3 times the flow stress of the metal phase). If, however, plastic deformation can be developed by some other renewable and repeatable means, a relatively small global and external pressure can drive the material to a fully-consolidated state. Phase transformations, thermal expansion mismatch and the volumetric changes produced by a remote pressure can drive local deviatoric stresses in the vicinity of the particles that provide plastic deformation and if these strains are renewed a small remote external pressure can be used to consolidate the composite. This paper shows that pressure cycling of heterogeneous composites with a compressibility mismatch is a particularly simple and effective way to develop composites of high density in the solid state.