Mechanical properties of aluminide matrix composites fabricated by reactive hot-pressing in several environments

The mechanical properties of Ni and Fe alminide matrix composites with low volume fraction of ceramic particles and fibers, fabricated by reactive hot-pressing, were evaluated. These composites reveal particular mechanical behaviors depending on characteristics of these matrix alloys. FeAl and Ni3Al matrix composites with ceramic particles exhibit significant loading rate dependence of toughness due to the moisture induced environmental embrittlement at ambient temperatures. The ultimate strength of the composites with ceramic continuous fibers, which exhibit the multiple fracture of fibers prior to the matrix cracking, also depends on the environmental embrittlement. Although the ductility and toughness of these composites at ambient temperatures is improved by the B doping, those of Ni3Al composites drastically decrease at intermediate temperatures due to dynamic oxygen embrittlement, deterioration of grain boundary cohesion and unique behavior of dislocations. On the other hand, NiAl composites are insensitive to the chemical effect of environmental factors because the matrix is inherently brittle. The alloy design for the matrix needs to be adequately applied to develop high performance intermetallic matrix composites.