Processing and Microstructure of Cr-Ta and Cr-Ta-Mo Composites Reinforced by the Cr2Ta Laves Phase

摘要

The Cr-Ta alloy with an eutectic structure has a good combination of high strength and oxidation resistance at elevated temperatures up to 1200 C. It is an ideal candidate for ultrahigh-temperature applications. However, the material shows low ductility and fracture toughness at room temperature. A possible way to improve the ductility and fracture toughness is to obtain an aligned microstructure of eutectic Cr-based alloys, using a directional-solidification (DS) process, in which the feed materials with eutectic compositions are preferred. In the present work, a quantitative technique was developed to assist in monitoring and controlling the composition of the Cr-based alloys at each stage of the processing at elevated temperatures. The eutectic composition of the binary Cr-Ta alloy was determined to be Cr-9.7 at.% (atomic percent) Ta, and a drop-cast ternary Cr-9.7 at.% Ta-1.0 at.% Mo alloy was found to possess a fully eutectic structure.