Pressure Casting of Ni3Al/Al2O3 Composites

Abstract

ABSTRACTA series of Du Pont PRD-166 and FP fiber reinforced Ni and nickel aluminide matrix composites, containing Ti or Y as a wetting agent, were produced by pressure casting. Modulus values determined under compression varied from 273 to 287 GPa in a direction parallel to the fibers and ranged from 148 to 159 in a direction normal to the fibers. Modulus values parallel to the fiber direction were approximately 5% lower than that predicted by the rule-of-mixtures. The much lower values of modulus normal to the fibers has been attributed to a number of sources which include fiber/matrix and fiber/fiber debonding and stress concentration resulting from voids existing at fiber/fiber bonds. It was observed, qualitatively, that good bonding between matrix and fiber occurred when Ti diffused from the matrix into fibers. The presence of Al in the matrix tended to inhibit Ti diffusion, increasingly as Al content increased. Thus fiber/matrix bond strength was poorer in the aluminides than in an alloy containing no Al. Y was not found to improve bonding, and an interface reaction zone was obserced in some areas where liquid metal initially entered the fiber preform.