Abstract
The present paper is primarily a study of the ordering characteristics within the CuPt system, near the CuPt composition, using X-ray diffraction, optical microscopy (in conjunction with polarized light), high-voltage electron microscopy and dilatometry.
In platinum-rich off-stoichiometric alloys, a wide two-phase region consisting of ordered + disordered platelets was established and the phase boundaries were accurately located. For isothermally ordered stoichiometric alloys, in general two categories of diffraction sequences were observed, depending on the annealing temperature. For anneals in the range 620°C<T<815°C (=Tc), a series of broad, asymmetric X-ray line profiles were obtained during the early part of the ordering cycle: this represents a “continuous” reaction. However, when samples were annealed a temperatures lower than 620°C, there was unmistakable micrographic evidence of the coexistence of both the ordered and disordered phases: this represents a “discontinuous” reaction. After making allowances for a number of side-effects which had broadened X-ray reflections at high temperatures, a nucleation-and-growth model is proposed for CuPt at all ordering temperatures.
The parallel microscopic studies also exhibited quite contrasting morphologies above and below 620°C: a lamellar structure is the product at high temperatures, whereas a grain-boundary reaction, generating very coarse domains, is observed at lower temperatures. A modified microstructure was observed for samples annealed at T<475°C, when ordered spherulites were seen to grow within the grains. Samples cooled slowly through T c order by a diffusion-controlled shear process.
Similar content being viewed by others
References
R. S. Irani and R. W. Cahn, Nature 226 (1970) 1045.
Idem, Acta Metallurgica 21 (1973) 757.
F. W. Jones and C. Sykes, J. Inst. Metals 59 (1936) 257.
R. S. Irani, Contemporary Physics 13 (1972) 559.
J. L. O'Brien and G. C. Kuczynski, Acta Metallurgica 7 (1959) 803.
M. Greenholz, J. Mater. Sci. 7 (1972) 1285.
H. N. Southworth, Scripta Met. 2 (1968) 551.
Fu-Wenling and E. A. Starke, Jun, “Advances in X-ray Analysis” 15 (New York, Plenum Press, 1971) p. 319.
Idem, Scripta Met. 5 (1971) 741.
J. B. Newkirk, A. H. Geisler, D. L. Martin, and. R. Smoluchowski, Trans. AIME 188 (1950) 1249.
J. M. Penisson, A. Bourret, and P. H. Eurin, Acta Metallurgica 19 (1971) 1195.
M. Hirabayashi and S. Weissman, ibid 10 (1962) 25.
P. N. Syutkin, V. I. Syutkina, O. D. Shashkov, E. S. Yakoyleva, and N. N. Buinov, Third Bolton Landing Conf. (edited by B. H. Kear, C. T. Sims, N. S. Stoloff and J. H. Westbrook) (Claitors, Baton Rouge, 1970) p. 227.
R. Smith and J. S. Bowles, Acta Metallurgica 8 (1960) 405.
B. Chakravarti, E. A. Starke, Jun, and B. G. Lefevre, J. Mater. Sci. 5 (1970) 394.
L. E. Tanner, Acta Metallurgica 20 (1972) 1197.
F. N. Rhines and J. B. Newkirk, Trans. ASM 45 (1953) 1029.
M. J. Marcinkowski and L. Zwell, Acta Metallurgica 11 (1963) 373.
F. W. Noble and W. Fairhurst, J. Mater. Sci. 7 (1972) 781.
H. Okamoto and P. A. Beck, Trans. AIME 2 (1971) 569.
P. R. Swann, W. R. Duff, and R. M. Fisher, Phys. Stat. Sol. 37 (1970) 577.
H. Warlimont, K. Bernecker, and R. Lück, Z. Metallk. 62 (1971) 816.
H. P. Aubauer, Acta Metallurgica 20 (1972) 165; 173.
J. O. Linde, Ann. Physik. 30 (1937) 151.
C. B. Walker, J. Appl. Phys. 23 (1952) 118.
N. T. Corke, S. Amelinckz, and J. van Landuyt Mat. Res. Bull. 4 (1969) 289.
H. G. Paris and B. G. Lefevre, Mat. Res. Bull. 7 (1972) 1109.
G. Fournet, “Phase Stability in Metals and Alloys” (edited by P. S. Rudman, J. Stringer and R. I. Jaffee) (McGraw-Hill, New York, 1967), p. 195.
P. C. Clapp and S. C. Moss, Phys. Rev. 142 (1966) 418; 171, 754, 764.
B. W. Mott, “Micro-Indentation Hardness Testing” (Butterworth, London, 1956).
R. S. Irani and R. W. Cahn, Metallography 4 (1971) 91.
S. Tolansky, “Multiple-Beam Interference Microscopy of Metals” (Academic Press, London, 1970).
A. Schneider and U. Esch, Z. Elektrochem. 50 (1944) 290.
P. Assayag and M. Dodé, Compt. Rend. 239 (1954) 762.
H. Warlimont, J. Sheffield Met. Soc. 7 (1968) 45.
R. S. Irani, Fu-Wen Ling, and R. W. Cahn, to be published.
L. E. Tanner and M. F. Ashby, Phys. Stat. Sol. 33 (1969) 59.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Irani, R.S., Cahn, R.W. The mechanism of crystallographic ordering in CuPt. J Mater Sci 8, 1453–1472 (1973). https://doi.org/10.1007/BF00551670
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF00551670