The room-temperature tensile properties, fracture mode, and grain boundary chemistry of undoped stoichiometric NiAl, as well as NiAl doped with boron, carbon, and beryllium, have been investigated, Pure, stoichiometric NiAl fractures with limited tensile ductility in a predominantly intergranular manner. Auger analyses revealed that the grain boundaries in NiAl are extremely clean and free of any segregated impurities, indicating that they are intrinsically brittle. Boron, when added to stoichiometric NiAl at a bulk level of 300 wt. ppm, segregates to the grain boundaries and suppresses intergranular fracture. However, there is no attendant improvement in tensile ductility because boron is an extremely potent solid solution strengthener in NiAl, more than doubling its yield strength. As a result, any potential benefit of improving grain boundary strength is more than offset by the increase in yield strength. Unlike boron, both carbon (300 ppm) and beryllium (500 ppm) are ineffective in suppressing intergranular fracture in NiAl, and Auger analyses of the C-doped alloy revealed that carbon did not affect the fracture mode because it did not segregate to the grain boundaries. Although neither beryllium nor carbon suppressed grain boundary fracture, their effects on the tensile ductility of NiAl were quite different: the ductility of the Be-doped alloy was higher than that of the B-doped alloy because beryllium, unlike boron, has a rather modest strengthening effect in NiAl, whereas the C-doped alloy was brittle like the B-doped alloy, because carbon is a potent solid solution strengthener, just like boron. These observations were rationalized by considering a hard-sphere model for interstitial and substitutional sites in NiAl. It was concluded that boron and carbon occupy interstitial sites, whereas beryllium dissolves substitutionally. In all the alloys that were investigated, the Ni and Al contents of the grain boundaries were not significantly different from the bulk levels, and no evidence was found for B–Ni cosegregation.
This is a preview of subscription content, access via your institution.
Buy single article
Instant access to the full article PDF.
Tax calculation will be finalised during checkout.
Subscribe to journal
Immediate online access to all issues from 2019. Subscription will auto renew annually.
Tax calculation will be finalised during checkout.
K. H. Hahn and K. Vedula, Scripta Metall. 23, 7 (1989).
A. G. Rozner and R. J. Wasilewski, J. Inst. Met. 94, 169 (1966).
Binary Alloy Phase Diagrams, edited by T. B. Massalski, J. L. Murray, L. H. Bennett, and H. Baker (American Society for Metals, Metals Park, OH, 1986).
J. H. Westbrook, J. Electrochem. Soc. 103, 54 (1956).
A. Ball and R. E. Smallman, Acta Metall. 14, 1349 (1966).
R. T. Pascoe and C. W. A. Newey, Met. Sci. J. 2, 138 (1968).
M. P. Seah, Surf. Sci. 53, 168 (1976).
C. J. McMahon, Jr., Mater. Sci. Eng. 25, 233 (1976).
D. McLean, J. Inst. Met. 81, 121 (1952–53).
A. Joshi and D. F. Stein, J. Inst. Met. 99, 178 (1971).
C. L. White and D. F. Stein, Metall. Trans. A 9A, 13 (1978).
C. T. Liu, C. L. White, and J. A. Horton, Acta Metall. 33, 213 (1985).
T. Takasugi, E. P. George, D. P. Pope, and O. Izumi, Scripta Metall. 19, 551 (1985).
T. Ogura, S. Hanada, T. Masumoto, and O. Izumi, Metall. Trans. A 16A, 441 (1985).
W. C. Oliver and C. L. White, in High-Temperature Ordered Intermetallic Alloys II (Proc. Mater. Res. Soc. Symp.), edited by N. S. Stoloff, C. C. Koch, C. T. Liu, and O. Izumi (Materials Research Society, Pittsburgh, PA, 1987), Vol. 81, p. 241.
S. S. Hecker, D. L. Rohr, and D. F. Stein, Metall. Trans. A 9A, 481 (1978).
C. L. White, R. E. Clausing, and L. Heatherly, Metall. Trans. A 10A, 683 (1979).
K. Aoki and O. Izumi, J. Jpn. Inst. Met. 43, 1190 (1979).
G. S. Painter and F. W. Averill, Phys. Rev. B 39, 7522 (1989).
T. Takasugi, N. Masahashi, and O. Izumi, Scripta Metall. 20, 1317 (1986).
A. Choudhury, Ph. D. Thesis, University of Tennessee, Knoxville, TN, 1987.
A. K. Kuruvilla and N. S. Stoloff, in High-Temperature Ordered Intermetallic Alloys (Proc. Mater. Res. Soc. Symp.), edited by C. C. Koch, C. T. Liu, and N. S. Stoloff (Materials Research Society, Pittsburgh, PA, 1985), Vol. 39, p. 229.
A. Choudhury, C. L. White, and C. R. Brooks, Scripta Metall. 20, 1061 (1986).
E. P. George, C. T. Liu, and R. A. Padgett, Scripta Metall. 23, 979 (1989).
U. F. Kocks and D. G. Westlake, Trans. Amer. Inst. Min. Engrs. 239, 1107 (1967).
E. M. Schulson and D. R. Barker, Scripta Metall. 17, 519 (1983).
M. A. Crimp and K. Vedula, J. Mater. Sci. 78, 193 (1986).
C. T. Liu, in Proc. ASM Materials Science Seminar: Science of Advanced Materials (to be published).
C. T. Liu, E. H. Lee, and C. D. McKamey, Scripta Metall. 23, 875 (1989).
N. Masahashi, T. Takasugi, and O. Izumi, Acta Metall. 36, 1815 (1988).
P. Villars and L. D. Calvert, Pearson’s Handbook of Crystallographic Data for Intermetallic Phases (American Society for Metals, Metals Park, OH, 1985), Vol. 2.
P. Lamparter, W. Sperl, S. Steeb, and J. Bletry, Z. Naturforsch. 37a, 1223 (1982).
F. Laves, in Theory of Alloy Phases (American Society for Metals, Cleveland, OH, 1956), p. 124.
H. W. King, in Physical Metallurgy, edited by R. W. Cahn (North-Holland, Amsterdam-London, 1970), p. 33.
C. T. Liu, in Interfacial Structure, Properties and Design (Proc. Mater. Res. Soc. Symp.), edited by M. H. Yoo, W.A.T. Clark, and C. L. Briant (Materials Research Society, Pittsburgh, PA, 1988), Vol. 122, p. 429.
C. T. Liu, unpublished results (1989).
N. Masahashi, T. Takasugi, and O. Izumi, Acta Metall. 36, 1823 (1988).
Sumit Guha, Paul Munroe, and Ian Baker, Scripta Metall. 23, 897 (1989).
J. J. Kruisman, V. Vitek, and J. Th. M. De Hosson, Acta Metall. 36, 2729 (1989).
V. Vitek, S. P. Chen, A. F. Voter, J. J. Kruisman, and J. Th. M. De Hosson, in Grain Boundary Chemistry and Intergranular Fracture, edited by G. S. Was (Trans. Tech. Publications, 1989).
A. H. King and M. H. Yoo, in High-Temperature Ordered Intermetallic Alloys II (Proc. Mater. Res. Soc. Symp.), edited by N. S. Stoloff, C. C. Koch, C. T. Liu, and O. Izumi (Materials Research Society, Pittsburgh, PA, 1987), Vol. 81, p. 99.
L. E. Davis, N. C. MacDonald, P. W. Palmberg, G. E. Riach, and R. E. Weber, Handbook of Auger Electron Spectroscopy (Physical Electronics Industries, Inc., Eden Prairie, MN, 1976).
P. P. Camus, I. Baker, J. A. Horton, and M. K. Miller, J. de Physique (to be published).
S. P. Chen, A. F. Voter, A. M. Boring, R. C. Albers, and P. J. Hay, in High-Temperature Ordered Intermetallic Alloys III (Proc. Mater. Res. Soc. Symp.), edited by C. T. Liu, A. I. Taub, N. S. Stoloff, and C. C-. Koch (Materials Research Society, Pittsburgh, PA, 1989), Vol. 133, p. 149.
About this article
Cite this article
George, E.P., Liu, C.T. Brittle fracture and grain boundary chemistry of microalloyed NiAl. Journal of Materials Research 5, 75 (1990). https://doi.org/10.1557/JMR.1990.0754