Results 1 - 10 of 6499
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[en] In this work, a review is made of the most recent studies employing Ni3Al(B,X) alloys with the aim of studing their important characteristics. (A.C.A.S.)
[pt]No presente trabalho e feita uma revisao dos estudos mais recentes realizados nas ligas de Ni3Al(B,X) visando divulgar as caracteristicas interessantes destes materiais. (A.C.A.S.)
[en] Creep testing has been performed on the nickel based single crystal alloy CMSX-4 at 750, 982 and 1050 deg C. The crystals had been hot isostatically pressed before testing. At 750 deg C the material exhibited primary creep which was not present at the higher temperatures. A tensile pre-creep at 750 deg C and 250 MPa for 4400 hours reduced the amount of primary creep and the minimum creep rate during creep at 750 deg C and 600 MPa. The pre-crept specimen also failed prematurely at an extensometer ridge. At 982 deg C and 206.9 MPa, tests were interrupted at 0.98, 1.96 and 7.5% strain for investigation of the microstructural changes during a test. Quantitative metallography of specimens after testing showed that at 750 deg C the γ/γ' microstructure was practically unchanged with cuboidal γ' particles in a γ matrix. At the higher temperatures, a transformation of the structure occurred where rafts of γ' phase were formed and the rafts became shorter and thicker as the creep strain increased. Porosity measurements of tested material showed a large increase in porosity up to 2% strain, thereafter the increase was less. One specimen failed in an unexpected manner and was studied using electron back scatter patterns (EBSP). The EBSP investigation revealed the presence of an isolated grain in the gauge length where the fracture occurred
[en] Phenomenological creep equations of a modified Garofalo type, including a description of plastic initial elongation and primary, secondary and tertiary creep can be applied to high-temperature steels and nickel base alloys for the whole range of temperatures, stresses, times and strains that is of practical interest. Deformation and damage under variable tensile pressure creep loads are described by constitutive 1D equations, which can be modelled on the basis of creep data from a phenomenological creep equation and can be integrated in a life prediction program
[de]Phaenomenologische Kriechgleichungen nach Art der modifizierten Garofalo-Gleichung mit Beschreibung von plastischer Anfangsdehnung sowie primaerem, sekundaerem und tertiaerem Kriechen koennen fuer warmfeste Staehle und Nickelbasislegierungen mit Gueltigkeit im ganzen, fuer die Anwendungspraxis interessierenden Bereich von Temperaturen, Spannungen, Zeiten und Dehnungen modelliert werden. Deformation und Schaedigung unter veraenderlichen Zug-Druck-Kriechbeanspruchungen lassen sich durch konstitutive 1D-Gleichungen beschreiben. Diese koennen auf der Grundlage von Kriechdaten aus einer phaenomenologischen Kriechgleichung modelliert und in einem Lebensdauerzaehlerprogramm genutzt werden. (orig.)
[en] The structural particularities of the zone of interaction between nickel aluminide surfaced,by an electron-beam technique and nickel-based alloys were investigated. A possibility was shown to slow down resorption by providing a diffusion barrier rich in chromium beneath the layer of the sufaced aluminide
[en] For many years, high-strength nickel-base superalloys have been used to manufacture turbine blades because of their excellent performance at high temperatures. The prediction of fatigue life of superalloys is important for improving the efficiency of the turbine blades. In this study, low cycle fatigue tests are performed for different values of total strain and temperature. The relations between strain energy density and number of cycles before failure occurs are examined in order to predict the low cycle fatigue life of IN738LC super alloy. The results of low cycle fatigue lives predicted by strain energy methods are found to coincide with experimental data and with the results obtained by the Coffin-Manson method
[en] Presented are the results of tests of the KhN60, KhN73MBTYu alloys and grade 20 steel at temperatures of 20, 300 and 500 deg C under rigorously cyclic loading with step increments and decrements of deformation amplitudes. It is shown that the resistance to cyclic deformation in a stable cycle may be substantially influenced by the loading history. An analytical description of the effect is presented
[en] Certain structurally gradient metallic materials have shown a combination of high strength and work hardening capability. The fundamental mechanisms behind such a unique mechanical behavior remain less well understood. Here we processed NiCrMo based C-22HS alloys by surface mechanical grinding treatment to achieve a gradient microstructure consisting of surface nanolaminated layer, deformation twinned layer and severely deformed layers. In situ micropillar compression tests performed inside a scanning electron microscope reveal different mechanical behaviors of each layer. This study suggests that the increase of intergranular back stress may have contributed to the high strain hardening behavior of the gradient material.
[en] During the 4th quarter of FY17 modeling and simulation development of creep in nickel-based alloys was continued with a focus on incorporation of simulated alloy microstructures into the creep model. Additionally, the model was calibrated with experimental creep data from Alloy 617. Experimental data collection also continued with creep tests, stress drop tests and characterization of alloy microstructures.
[en] Using the ZhS6U alloy as an example, the orientation agreement between the matrix of γ-solid solution and the eutectic depositions of γ+γ' nickel heat-resistant alloys has been considered. The substructure in different areas of a single crystal of the ZhS6U alloy has been examined by resorting to the metallographic and X-ray analysis methods. The microstructure, diffraction, X -ray topographic pictures of a single crystal of the nickel heat-resistant alloy, are presented. It is shown that a good orientation agreement exists between the matrix of γ-solid solution and γ' phase of the eutectic. The alloy presents X-ray pictures that are characteristic of a fairly perfect single crystal