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Journal ArticleDOI

High-temperature flow behaviour and concurrent microstructural evolution in an Al-24 wt% Cu alloy

01 Oct 1995-Journal of Materials Science (Kluwer Academic Publishers-Plenum Publishers)-Vol. 30, Iss: 20, pp 5295-5303
TL;DR: In this article, the presence of non-steady-state flow influences the parameters of the constitutive relation to varying extents and the strain softening is associated with cavitation in Al-24 wt% Cu alloy of grain sizes in the range 7.6-20.6 μm.
Abstract: Tensile specimens of an Al-24 wt% Cu alloy of grain sizes in the range 7.6–20.6 μm were deformed at 400–540 °C using constant initial strain rates ranging from 5×10−6 to 2×10−2 s−1. Initially the stress-strain (σ-ɛ) curves show work hardening which is followed by strain softening at higher strain rates and lower temperatures. At lower strain rates and higher temperatures, on the other hand, σ continues to increase with strain or tends to be independent of strain. Grain growth and cavitation occur to varying extents depending on strain rate and test temperature. While the grain growth can account for the work hardening at higher temperatures as well as at lower strain rates, it fails to do so at higher strain rates. The strain softening is associated with cavitation. The presence of non-steady-state flow influences the parameters of the constitutive relation to varying extents.
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TL;DR: In this article, a Zr-2.5Nb alloy was annealed at 900°C for 5-90 min and quenched in water, which resulted in formation of α′ martensite and primary α phase.

4 citations

References
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Journal Article
TL;DR: A general survey of plastic deformation can be found in this article, where Orowan and Bailey-Orowan equations are used to define deformation mechanism maps for pure metals.
Abstract: 1. Deformation and Creep. Deformation. Definition of creep. Time dependence of creep strain. Creep Curve. Mechanisms of plastic deformation: A general survey. Mechanical equation of state. Creep test compared with tensile test at constant strain rate and constant loading rate. Creep tests at constant load and constant stress. 2. Motion of Dislocations. Dynamic Recovery. Motion of dislocations. Free, mobile and moving dislocations. Dynamic recovery. 3. Temperature Dependence of Creep Rate. Activation energy of creep. Methods of determination of activation energy of creep. Correction of experimentally determined activation energy of creep for temperature dependence of elastic modulus. Activation energy or creep and activation enthalpy of diffusion. 4. Applied Stress Dependence of Creep Rate. Initial creep rate. Steady-state creep. Transient creep. 5. Influence of Grain Size and Stacking Fault Energy. Grain size. Stacking fault energy. 6. Orowan and Bailey-Orowan Equations. Orowan equation. Bailey-Orowan equation. Relation between Orowan equation and Bailey-Orowan equations. A consequence of the equivalence of Orowan and Bailey-Orowan equations. Experimental verification of Bailey-Orowan equation. Experimental determination of quantities r and h. Incubation period and ``Frictional'' stress. 7. Back Stress. Internal, threshold and frictional stress. Internal and effective stress. Concept of internal and effective stress and the mechanical equation of state. Definitions of experimental parameters. Interpretation of experimental parameters. 8. Dislocation Structure. Development of dislocation structure during creep. Basic quantitative characteristics of dislocation structure. Subgrain structure. Subgrain structure and long-range internal stress. Behaviour of sub-boundaries. Interaction of dislocations with sub-boundaries. Generation of dislocations. Structural steady state. Concept of hard and soft regions and measured internal stress. 9. Dislocation Creep in Pure Metals. Creep controlled by recovery. Creep controlled by dislocation glide. Models based on thermally activated glide and diffusion controlled recovery. Relation between constants A and n in the dorn creep equation and the natural third power law. Harper-Dorn creep. 10. Creep in Solid Solution Alloys. Introduction. Mechanisms of creep strengthening in solid solutions. Creep controlled by viscous dislocation glide. 11. Creep in Precipitation and Dispersion Strengthened Alloys. Models of Ansell and Weertman. Back stress concept. 12. Diffusional Creep. Nabarro-Herring and Coble creep. Subgrain boundaries as sources and sinks for vacancies. Diffusional creep and grain boundary sliding. Reactions on grain boundaries. Diffusional caritational creep. 13. Deformation Mechanism Maps. Equations used for construction of deformation mechanism maps. Examples of deformation mechanism maps. ``Generalized'' deformation mechanism map for pure metals. 14. Grain Boundary Sliding.

499 citations

Journal ArticleDOI
TL;DR: The relationship between stress and strain rate is often sigmoidal in superplastic materials, with a low strain rate sensitivity at low and high strain rates (regions I and III, respectively) and a high strain rate sensitive at intermediate strain rate (region II) where the material exhibits optimal super-plasticity as discussed by the authors.
Abstract: The relationship between stress and strain rate is often sigmoidal in superplastic materials, with a low strain rate sensitivity at low and high strain rates (regions I and III, respectively) and a high strain rate sensitivity at intermediate strain rates (region II) where the material exhibits optimal superplasticity This relationship is examined in detail, with reference both to the conflicting results reported for the Zn-22 pct Al eutectoid alloy and to the significance of the three regions of flow

378 citations

Book
01 May 1989

304 citations

Journal ArticleDOI
TL;DR: The simultaneous diffusion of 64Cu and 67Cu has been measured in copper single crystals from 890 to 1061 °C and the strength of the isotope effect f ΔK is 0.684 ± 0.014 and is independent of temperature within the experimental error.
Abstract: The simultaneous diffusion of 64Cu and 67Cu has been measured in copper single crystals from 890 to 1061 °C. The strength of the isotope effect f ΔK is 0.684 ± 0.014 and is independent of temperature within the experimental error. This indicates that the contribution of divacancies to self-diffusion in copper is small. The diffusion coefficient of 67Cu in copper single crystals was measured from 700 to 1060 °C and is given by . Die gleichzeitige Diffusion von 64Cu und 67Cu wurde im Bereich von 890 bis 1061 °C an Kupfereinkristallen gemessen. Die Grose des Isotopeneffekts f ΔK ergibt sich zu 0,684 ± 0,014 und ist temperaturunabhangig innerhalb der Mesgenauigkeit. Dies bedeutet, das der Beitrag von Doppelleerstellen zur Selbstdiffusion in Kupfer gering ist. Der Diffusionskoeffizient von 67Cu in Kupfereinkristallen wurde im Bereich von 700 bis 1060 °C gemessen und ergibt sich zu ,

168 citations