Laws governing deformation and hardening of single crystals of aging alloys
The phenomenon of "early overaging" is not observed in single crystals, i. e., softening of the alloy does not begin until a particle size is reached that is almost an order higher than the "critical" size for polycrystalline material. The phenomenon of early overaging is associated with the structure of the grain boundaries. Softening of single crystals begins when the coherent bond between the particles and the matrix is disrupted.
For nickel-base aging alloys hardened with particles of the γ′ type (Ni3Al) one observed an anomalous temperature dependence of the yield strength. The magnitude of the anomaly depends on the properties and the volume percentage of γ′ phase. For alloys with considerable dislocations splitting in the matrix (Ni-Al-Cr alloys, e. g.) the anomalous variation of τc with T at elevated temperatures is combined with a normal variation in the temperature range below room temperature.
A means of increasing the ductility of biphase alloys that is new in principle was established—the creation of regular "quasiperiodic macrolattices" from particles of the precipitating phase. The character of the quasiperiodic distribution of particles can be changed by alloying, heat treatment, or application of external loads in the process of aging.
KeywordsParticle Size Heat Treatment Ductility Yield Strength Elevated Temperature
Unable to display preview. Download preview PDF.
- 1.N. T. Travina and G. I. Nosova, "Effect of the size and distribution of the ordered phase on the critical shearing stress in Ni-Al and Nimonic alloys," Fiz. Metal. Metalloved.,29, No. 3, 564 (1970).Google Scholar
- 2.J. Friedel, Dislocations, Pergamon Press (1964).Google Scholar
- 3.B. Kear et al., Scr. Metall.,3, No. 2, 123 (1969).Google Scholar
- 4.G. Leverant and S. Hopkins, Mater. Sci. and Eng.,8, No. 3, 125 (1971).Google Scholar
- 5.M. Tamura, T. Mori, and T. Nakamura, Trans. Japan Inst. Met.,14, No. 5, 355 (1973).Google Scholar
- 6.Yu. D. Tyapkin, in: Problems of Metal Science and Physics of Metals [in Russian], No. 3, Metallurgiya, Moscow (1976), p. 6.Google Scholar
- 7.Yu. D. Tyapkin, N. T. Travina, and V. P. Kozlov, "Electron microscopic study ofthe three-dimensional distribution of second phase in nickel-base aging alloys," Fiz. Metal. Metalloved.,35, No. 3, 577 (1973).Google Scholar
- 8.Yu. D. Tyapkin, N. T. Travina, and V. P. Kozlov, "Relationship between the character and parameters of short-range order of the quasiperiodic distribution of particles of second phase in nickel alloys and their structural characteristics," Fiz. Metal. Metalloved.,39, No. 1, 73 (1975).Google Scholar
- 9.N. T. Travina et al., Fiz. Metal. Metalloved.,36, No. 4, 804 (1973).Google Scholar
- 10.V. Phillips, Phil. Mag.,16, No. 139, 103 (1967).Google Scholar