The influence of the rheological parameter on the ductility evolution has been also studied. © 2017, Institute for Metals Superplasticity Problems of Russian Academy of Sciences. Rapid grain coarsening, however, occurred during tensile testing beyond 523 K, leading to a loss of superplasticity. Die Wahl von Zirkon-Rohren und der Temperaturen steht im Zusammenhang mit ihrer technologischen Anwendung. Material characteristics obtained were compared to charecteristics determined by other methods for the same set of experimental data available in the literature. A previously suggested equation relating the stress rate and stress which avoids the indeterminacy of machine stiffness is applied to this type of experiments on zirconium tubes at room temperature and 400° C.
Une équation antérieurement proposée reliant la constrainte et la vitesse de mise en contrainte, ce qui évite d'apprécier la rigidité de la machine de traction, est appliquée à ce type d'expériences sur des tubes de zirconium à la température ambiante et à 400°C. The iso-strain rate sensitivity m contour map was used to determine the optimum regime of high temperature workability. Discussion of various types of stress—strain curve in tension. Yielding criteria, invariant functions of stress and strain, and flow rules. The microstructure influence on the thermally activated deformation behaviour of chromium is investigated for a more fundamental understanding on the deformation mechanisms contributing to plasticity in bcc metals. Due to the fast loading time, the local temperature increase during dynamic loading induces a thermal softening. Die Stabilität der Verformung wird untersucht.
Hybrid material systems result from the specific combination of different materials. High elongations have been obtained in iron or cast iron in the range of temperatures corresponding to the α — γ transformation1. Procedure Of Tensile Test Machine are available as part of a TestResources product line of test machine accessories that include a wide range of test fixtures, high low temperature chambers, furnaces, tensile grips, and extensometers. An increase in ductility is favored by the introduction of a grain fraction with submicron grains into the nanocrystalline matrix the creation of a bimodal structure. Furthermore, the coatings were compared with those without cold-swaging coatings at the same time. The value of the optimum strain rate is indeed adapted to the level of strain developed within the part during the forming. RésuméDie Phänomenologie des Zugversuchs wird erneut untersucht, unter besonderer Berücksichtigung des Einflusses einer Verformungsgeschwindigkeitsabhängigkeit der Flieβspannung.
Especially, the elongation increased greatly after aging at 100°C. Les paramètres de cette équation sont discutés en termes des densités de dislocations mobiles et totales. Superplasticity, which enables processing on hard-to-work solids, has been recognized only in metallic solids. For flow stress modelling, an Arrhenius type constitutive model was established to predict the flow stress behaviour during hot deformation. This statement is valid for either the quasi-static or the dynamic observations, but does not fit the experimental data over the whole studied range. We demonstrate that the conditions for plastic instability, which are traditionally obtained from solid mechanics considerations, also follow from linear stability analysis of the intrinsic evolution laws for the dislocation density.
The reduction in m and γ values could be associated with the early onset of plastic instability and with microstructural changes observed as function of the strain. In this work, the pressure law is computed in order to control the forming process by a non-constant strain rate. In addition, the volume fractions of cavities at different plastic strain levels were assessed using X-ray microtomography. Les résultats indiquent que certaines des méthodes utilisées pour l'évaluation des membranes de couverture doivent être soigneusement choisies en fonction du matériau à l'essai. For the considered application, the material can undergo both quasi-static and dynamic loadings. The effect is enhanced at low temperatures as a result of activation of twinning in larger grains.
Stress relaxation offers a means for evaluating the deformation dynamics of metals. Severe plastic deformation is achieved by repetitive cyclic plastic deformation processes such that the overall dimensions of the workpiece remain unchanged after each deformation cycle. This expression is then used to propose criteria for the onset of necking and more importantly for the emergence of strong localization. At low Z, the ferrite phase accommodates the strain and dynamic recovery was the prominent restoration process. Superplastic forming is widely used in aeronautic industry to produce complex parts due to the ability of the material to sustain very large deformation. In situ high-energy X-ray diffraction was used to map changes linked to the separating phases, and the development of a nanoscale Cu-Co composite structure was observed. The possible deformation mechanisms at such extremely small crystallite sizes are discussed within the framework of pertinent literature.
In particular, it was observed that the new model could predict the flow behavior of these metals more successfully compared with two reference models; nevertheless, it requires minimal experimentation and calculation efforts. Il étudie également la stabilité de la déformation et la croissance d'un inhomogénéité pour un régime de déformation instable. Plus de deux cents échantillons ont été soumis aux essais de traction. From the Hart's instability criterion, it is known that an elevated strain rate sensitivity improves the tensile ductility by stabilizing uniform tensile deformation to large strains. By adapting standard nanoindentation test methods, simple protocols capable of probing thermally activated deformation processes can be accomplished. The problems associated with the formation of superplastic state in metallic alloys are very interesting, considering not only the scientific aspects but particularly its suitability for industrial application.
Those mainly result from a changing indentation strain-rate during the hold segment at peak load. During superplastic deformation quite complicated shapes can be accomplished in just one operation and at much lower stresses than in an ordinary deformation process cutting costs and energy expenses. In the present study, a series of tensile tests of Mg-Al alloy has been carried out to study deformation behavior with temperature variation. The microstructural evolution and enhanced mechanical properties of the processed samples are systematically explored, which is expected to expand the application of the 316L stainless steel as a structural material. L'influence des paramètres rhéologiques sur l'évolution de la ductilité est également étudiée. The nonequilibrium solid solution decomposed during subsequent isothermal annealing. On the other hand, runout specimens showed some crack nuclei, but they were not able to overcome the next microstructural barrier.