Strength and Fracture Behavior of Aluminide Matrix Composites with Ceramic Fibers

Abstract

ABSTRACTThis paper investigates the fracture behavior of FeAl and Ni3AI matrix composites with ceramic continuous fibers 8.5–10 μm in diameter. When stress is applied to these composites, multiple-fracture of fibers predominately occurs before matrix cracking, because the load carried by the fibers reaches their fracture strength. Fragments which remain longer than the critical length can provide significant strengthening through load bearing even though fiber breaking has occurred. The ultimate fracture strength of the composites also depends on stress relaxation by plastic deformation of the matrix at a crack tip in the multiple-fractured fibers. Ductilizing of the matrix by B doping improves the ultimate strength at ambient temperatures in both composites. However, their mechanical properties at elevated temperatures are quite different. In the case of Ni3AI matrix composites, embrittlement of the matrix is undesirable for high strength and reliability at 873–973 K.