Processing and Microstructures of Cr-Ta and Cr-Ta-Mo Composites Reinforced By the Cr(sub 2) 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 1,200 C. It is an ideal candidate for ultrahigh-temperature applications. However, the material shows low ductility and fracture toughness at room temperature. An effective 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 employed to assist in monitoring and controlling the composition of the Cr-based alloys throughout the processing stages at elevated temperatures. A colony structure related to the instable liquid/solid interface was observed in a DS Cr-Ta sample. A possible eutectic area was probed in the Cr-Mo-Ta system, which could facilitate the development of well-aligned lamellar structures by DS.