Microstructure and interface behavoir in diffusion bonded Ni3Al+B matrices containing continuous Al2O3 fibers

Diffusion bonding is a well known method for fabricating metal matrix composites with continuous fiber reinforcements. However, little data yet exist regarding optimum processing conditions for production of such composites using intermetallic matrices. In this study, diffusion bonded couples were made from boron doped nickel aluminide slabs (vacuum arc remelted alloy IC-15) into which small numbers of continuous fibers of α-Al2O3 were laid up. Diffusion bonding was carried out in vacuum at stresses between 20 and 50 MPa for 2 to 8 hours at 1273K to 1553K. The specimens were then fractured in uniaxial tension at room temperature and the microstructures and fracture surfaces examined. Preliminary data from optical and scanning electron microscopy show complete metal-lurgical bonding of the IC-15 slabs occurred only when process temperatures exceeded 1533K. At these temperatures a 2-hour processing time resulted in considerable grain growth in both the matrix and in the fibers. Occasional fiber fracture was also found to have occurred during the bonding cycle. Auger electron spectroscopy has revealed little interdiffusion between fiber and matrix after 2 hours at 1553K and no apparent fiber-matrix reaction zones were detected for any of the process conditions studied