Application of Mismatch Induced Superplasticity to the Consolidation of CompositeCompacts

摘要

It has been postulated that mismatch induced superplastic effects can be attainedin the pressure cycling of materials that have a mismatch in compressibility. This project sought to: (1) experimentally verify that superplastic effects can be attained this way, and (2) apply this effect to the practical forming of metal matrix composites and the consolidation of composite powder compacts. This project was fully successful in demonstrating that the effect exists and can be applied to the practical compaction of composite powders. However, at present, the forming of composite sheets by pressure cycling does not appear to be practical (although has been demonstrated). Specifically it was shown pressure cycling can increase the density, density uniformity and strength (by factors up to 5) of green composite powder compacts by imposing proper pressure cycling. This is important as very minor modifications to conventional uniaxial (hot or cold) pressing equipment are all that are required to access these effects, strengths can increase strongly, and a simple model we have produced can guide the design of compaction processes. This may make possible the development of classes of highly reinforced composites that are presently impossible to produce.