The application of pettifor structure maps to ternary additions in Nb 3Al-based alloys

Abstract

The intermetallic compound Nb{sub 3}Al exhibits the A15 crystal structure and forms via a peritectic reaction between the liquid and a BCC (A2) Nb-rich solid solution at 1,960 C. While this compound exhibits significant high temperature strength and creep resistance, it is not possible to induce plastic deformation at temperatures below {approx} 1,100 C. One strategy which has been adopted in attempting to overcome the brittle behavior of Nb{sub 3}Al has been to use a combination of rapid solidification processing and ternary alloying to induce the B2 structure which results in alloys which are significantly more ductile. In the present paper the authors illustrate this approach by considering Nb-Al-X compositions for which structural data is available, and compare these with the structures which would be expected on the basis of the Pettifor maps.