Effect of iron additions on structure of Laves phases in NbCrFe alloys

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Structural materials : properties, microstructure and processing, 1993-01, Vol.160 (1), p.37-48
• Main Authors: Grujicic, M., Tangrila, S., Cavin, O.B., Porter, W.D., Hubbard, C.R.
• Format: Article
• Language: English
• Subjects: Alloys; Applied sciences; Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Metals. Metallurgy; Physics; Structure of solids and liquids; crystallography; Structure of specific crystalline solids
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/0921-5093(93)90495-Z

The effect of iron additions on the stability of various Laves phases in the NbCr base system has been examined. In the binary NbCr system a hexagonal (C14) Laves phase exists at temperatures above approximately 1860 K, and undergoes] a shear-like martensitic transformation to a face centered cubic (C15) Laves phase on cooling to room temperature. Addition of iron promotes formation of an additional phase, the dihexagonal (C36) Laves phase. In alloys with a lower iron content (below approximately 5 wt.%), the C36 phase forms at higher temperatures. In addition, the C15 phase begins to form on cooling to room temperature. In sharp contrast, in alloys with a higher iron content, only the C14→C36 phase transformation takes place in the entire temperature range studied ( RT 1473 K). These findings were rationalized on the basis of the effects of chemical energy change and elastic strain energy on magnitude of the activation energy for martensitic transformation.