Strength of Single Crystal Al2O3 Fibers in Ni-Based Intermetallic and Superalloy Composites

Abstract

AbstractStrength degradation of single crystal Al2O3 fibers due to the effect of fiber/matrix interaction and processing of NiAl and superalloy matrix composites, was investigated. Strength loss was quantified by tensile testing fibers that were exposed to the matrix alloy using two different methods. In one method, the fibers were incorporated into a composite by either the Powder Cloth (P-C) or binderless powder technique. The fibers were then extracted from the composite by chemical dissolution of the matrix and subsequently tensile tested and examined by scanning electron microscopy. In the other method, fibers were sputter-coated with a similar matrix composition and heat-treated to simulate conditions similar to those experienced during composite powder fabrication methods. In the sputter coating method, the contribution of fiber-matrix reaction on fiber strength loss was isolated from the effects of the various mechanical loads which are present during powder fabrication. For all matrices studied, significant strength loss was observed both in fibers extracted from composites and in fibers sputter-coated and annealed. Although surface ridges and pores were observed on the degraded fibers, it remains uncertain whether these features were responsible for the strength loss.