PITTSBURGH UNIV PA DEPT OF METALLURGICAL AND MATERIALS ENGINEERING
By a floating zone melting and freezing technique, eutectic and hyper-eutectic Nb-Nb2C alloys may be grown with well aligned two phase composite structures. The morphology of the carbide phase may be rod-like, plate-like or a combination of rods and plates depending on the growth rate and carbon content. The rod spacing or plate-spacing is a function of growth rate. The structural stability of as grown rod-like Nb-Nb2C composites grown at two different growth rates and the stability of deformed Nb-Nb2C composites have been examined after isothermal annealing at temperatures in excess of one half the eutectic temperature for periods up to 700 hrs. In part two, aspects of cast structure, including interfaces, segregation, particles, and discontinuities, are discussed in relation to their dependence on casting conditions and in relation to their effect on properties.