Fe 3 Al Iron Aluminides Alloyed with High Concentrations of V and Cr: Their Structure and High Temperature Strength
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TION
REGARDLESS of the intensive research on different iron-based materials, alloys based on iron aluminides remain ideal candidates for the development of new structural materials with improved performance in petrochemical, power-generation, and aeronautical applications.[1,2] The major advantages of iron aluminides are excellent resistance to oxidation and sulfidation, a high strength-to-weight ratio (two-thirds of the density of steel), high electrical resistance, and the input material is relatively inexpensive due to the high content of Fe and Al. The high strength-to-weight ratio of this material and chemical stability is particularly useful for industrial applications. Nevertheless, the main drawbacks of these alloys strongly limit their wider utilization—particularly their poor workability at room
PETR KRATOCHVI´L, JOSEF PESˇICˇKA, PETER MINA´RIK, and ROBERT KRA´L are with the Department of Physics, Faculty of Mathematics and Physics, Charles University, Ke Karlovu 5, 12116 Prague 2, Czech Republic. Contact e-mail: [email protected]ff.cuni.cz STANISLAV DANISˇ is with the Department of Condensed Matter Physics, Faculty of Mathematics and Physics, Charles University, Ke Karlovu 5, 12116 Prague 2, Czech Republic. Manuscript submitted February 22, 2018.
METALLURGICAL AND MATERIALS TRANSACTIONS A
temperature and low high-temperature (HT) strength. Huge efforts have been made to increase the HT strength of iron aluminides and now a variety of methods have been developed, see, e.g., References 3 and 4. The most common ones are based on alloying and are, in particular,
Strengthening
by solid solution hardening (SSH)—typically Cr, Mo, or V.[4,5] Strengthening by D03 order increase in the D03 M B2 transition temperature, typically Ti.[6,7] Strengthening by coherent precipitates—the most effective way to enhancing the HT properties, typically for Ti.[8] Strengthening by incoherent precipitates—typically Zr, Nb, or Ta.[9,10] The number of additives with proper solubilities in Fe3Al iron aluminide is not high. The effect of Cr, Ti, V, Mo, Si, and Mn on the value of the 0.2 pct yield stress is described in detail in References 4, 5 and 11 through 14. References 4 and 11 are the first effort to describe the value of 0.2 pct proof stress in iron aluminide with the use of the Labusch’s theory of SSH.[15] Recently, Kratochvı´ l et al.[5] have measured and discussed the combined effect of two solutes in an iron aluminide and compared it to the effect of a single solute. The additivity of the strengthening effects of single solutes
was tested. There were found higher values than the sum of the solid solution strengthening contributions by individual solutes in the case of concentrations above ~ 5 at. pct. The explanation was based on the structural ordering that appeared in the alloys. In this study, the effect of high concentrations of V and Cr in Fe3Al on the microstructure and mechanical properties is studied. The data available in the Landolt–Bernstein ternary diagrams (Springer Materials)[16] indicate that the solid solubil
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