Abstract
Low-stress creep behaviour of microduplex Zn-22% Al alloy was studied using spring specimen geometry. The average phase size in the specimens investigated was 0.87, 1.48 and 1.98 μm. Experiments were conducted in the temperature range 393–473 K at stresses below about 1.0 MN m−2. The present study has established that the stress exponent of the creep rate is unity and, therefore, a viscous creep process dominates the flow in Region I superplasticity. The activation energy corresponds to that for boundary diffusion. However, the phase-size exponent was found to be −2 instead of −3, as predicted by the Coble creep theory. Further, the measured creep rates are three to four orders of magnitude slower than those predicted by the Coble theory. Transmission electron microscopy revealed precipitation, along α/α grain interfaces, whose inhibiting action on plastic flow should at least be partly responsible for the lower values of measured creep rates. There also exist two other interfaces, namely α/β and β/β, whose comprehensive role in diffusion creep is not yet fully understood. Therefore, it seems illogical to describe the creep behaviour of Zn-22% Al by the classical Coble theory, originally developed for single-phase polycrystals.
Similar content being viewed by others
References
P. YAVARI and T. G. LANGDON, Mater. Sci. Engng 57 (1983) 55.
M. L. VAIDYA, K. L. MURTHY and J. E. DORN, Acta Metall. 21 (1973) 1615.
A. ARIELI, A. K. S. YU and A. K. MUKHERJEE, Metall. Trans. 11A (1980) 181.
S. C. MISRA and A. K. MUKHERJEE, in “Rate Processes in Plastic Deformation of Materials”, edited by J. C. M. LI and A. K. MUKHERJEE (ASM, Metals Park, OH, 1975) p. 434.
R. S. MISHRA and G. S. MURTY, J. Mater. Sci. 23 (1988) 593.
H. ISHIKAWA, F. A. MOHAMED and T. G. LANGDON, Phil. Mag. 32 (1975) 1269.
F. A. MOHAMED and T. G. LANGDON, Acta Metall. 23 (1975) 117.
F. A. MOHAMED, S. A. SHEI and T. G. LANGDON, ibid. 23 (1975) 1443.
F. A. MOHAMED, M. M. I. AHMED and T. G. LANGDON, Metall. Trans. 8A (1977) 933.
P. SHARIAT, R. B. VASTAVA and T. G. LANGDON, Acta Metall. 30 (1982) 285.
D. GRIVAS, J. W. MORRIS and T. G. LANGDON, Scripta Metall. 15 (1981) 229.
D. GRIVAS, Rep. LBL-7375, Lawrence Berkeley Laboratory, University of California, Berkeley, CA (1978).
S. H. VALE, D. J. EASTGATE and P. M. HAZZLEDINE, Scripta Metall. 13 (1979) 1157.
D. W. LIVESEY and N. RIDLEY, ibid. 16 (1982) 165.
P. K. CHAUDHURY and F. A. MOHAMED, Acta Metall. 36 (1988) 1099.
D. J. TOWLE and H. JONES, ibid. 24 (1976) 399.
G. MALAKONDAIAH and P. Rama RAO, Trans. Ind. Inst. Metals 31 (1978) 361.
W. ROSTOKER and J. R. DVORAK, “Interpretation of Metallographic Structures”, 2nd Edn (Academic Press, New York, 1977).
E. S. WAJDA, Acta Metall. 2 (1954) 184.
T. S. LUNDY and J. F. MURDOCK, J. Appl. Phys. 33 (1962) 671.
G. A. SHIRN, E. S. WAJDA and H. B. HUNTINGTON, Acta Metall. 1 (1953) 513.
K. A. PADMANABHAN and G. J. DAVIES, in “Superplasticity” (Springer, Berlin, Heidelberg, 1980).
F. R. N. NABARRO, “Reports of the Conference on he Strength of Solids” (Physical Society, London, 1948) p. 75.
C. HERRING, J. Appl. Phys. 21 (1950) 437.
R. L. COBLE, ibid. 34 (1963) 1679.
M. F. ASHBY and R. A. VERRALL, Acta Metall. 21 (1973) 149.
J. J. KEARNS, J. E. MCCAULEY and F. A. NICHOLS, J. Nucl. Mater. 61 (1976) 169.
L. W. CHEN, Acta Metall. 30 (1982) 1655.
J. H. SCHNEIBEL and P. M. HAZZLEDINE, J. Mater. Sci. 18 (1983) 562.
R. B. VASTAVA and T. G. LANGDON, Acta Metall. 27 (1979) 251.
T. CHANDRA, J. J. JONAS and D. M. R. TAPLIN, J. Mater. Sci. 13 (1978) 2380.
G. S. MURTHY, Scripta Metall. 20 (1986) 533.
K. E. EASTERLING and G. H. GESSINGER, Z. Metallkde 63 (1972) 237.
M. F. ASHBY, Scripta Metall. 3 (1969) 837.
B. BURTON, Mater. Sci. Engng 11 (1973) 337.
J. E. HARRIS, Metal Sci. J. 7 (1973) 1.
B. BURTON, “Diffusional Creep of Polycrystalline Materials” (Trans. Tech. Publications, Aedermannsdorf, Switzerland, 1977).
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Prasad, N., Malakondaiah, G., Banerjee, D. et al. Low-stress creep behaviour of superplastic Zn-22% Al alloy. Journal of Materials Science 28, 1585–1594 (1993). https://doi.org/10.1007/BF00363353
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/BF00363353