Phase Stability of gamma;rsquo; (L12) Compounds and Alloy Design in Fe, Ni, Co and Cu-Based Alloys
Phase stability of intermetallic compound of γ&’ with L12 structure in Fe, Ni, Co and Cu-based alloys is briefly reviewed focusing on stable and metastable γ (Al) / γ&’ phase equilibria. The γ / γ&’ phase equilibria of Ni-Al-X alloy can be classified into six categories where Ta, Nb and Ti are the strong γ&’ (Ni3Al) stablilizing elements(1). The solvus temperatures of the metastable γ&’ phase in Fe-based alloys are increased by the additions of Ta, Nb and Ti. This trend can also be seen in the ternary compound of the γ&’ Co3 (Al, W) phase in Co-based alloys(2)(3). Based on the phase stability of the γ&’ phase, the following advanced alloys have been designed and developed.
New ferrous shape memory alloys: Fe-Ni-Co-Al-based alloys with the γ + γ&’ two-phase structure exhibit an excellent superelasticity and high transformation stress strengthened by Ta(4) and Nb(5).
Co-based superalloys: Cast Co-based superalloys have been applied to FSW (Friction Stir Welding) tool strengthened by the γ&’ Co3 (Al, W) compound(6).
Cu-based alloys: Cu-Ni-Al based alloys with high strength and high electronic conductivity strengthened by the γ&’ (Ni, Cu)3Al phase have been designed using the thermodynamic database of Cu-based alloys(7). This alloy has been commercially produced and used as suspension wire in a DVD drive.
C. C. Jia, K. Ishida and T. Nishizawa, Metall. Mater. Trans. A, 25A (1994) 473-485.
J. Sato, T. Omori, K. Oikawa, I. Ohnuma, R. Kainuma and K. Ishida, Science, 312 (2006) 90-91.
T. Omori, K. Oikawa, J. Sato, I. Ohnuma, U. R. Kattner, R. Kainuma and K. Ishida, Intermetallics 32 (2013), 274-283.
Y. Tanaka, Y. Himuro, R. Kainuma, Y. Sutou, T. Omori and K. Ishida, Science, 327 (2010) 1488-1490.
T. Omori, S. Abe, Y. Tanaka, D.Y. Lee, K. Ishida and R. Kainuma, Scripta Mater. 69 (2013) 812-815.
Y. S. Sato, M. Miyake, H. Kokawa, T. Omori, K. Ishida, S. Imano, S. H. C. Park and S. Hirano, Friction Stir Welding and Processing VI, TMS (The Minerals, Metals & Materials Society), (2011) 3-9.
C. P. Wang, X. J. Liu, M. Jiang, I. Ohnuma, K. Kainuma and K. Ishida, J. Phys. Chem. Solids, 66 (2005) 256-260.