Laws governing deformation and hardening of single crystals of aging alloys
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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
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