A Physically Consistent Method for the Prediction of Creep Behavior of Metals

1979 ◽  
Vol 46 (4) ◽  
pp. 800-804 ◽  
Author(s):  
G. J. Weng
Keyword(s):  
Single Crystals ◽  
Creep Behavior ◽  
Pure Shear ◽  
Tensile Creep ◽  
Polycrystalline Materials ◽  
Steady Creep ◽  
Creep Properties ◽  
Consistent Method ◽  
Latent Hardening ◽  
Good Agreement

A physically consistent method, which considers the deformation mechanisms, the active and latent hardening in single crystals, and their transient and steady creep, is proposed to predict the creep behavior of polycrystalline materials. This method consists of two steps: first, the material constants of single crystals are determined from the tensile creep data of the polycrystal, and then these constants are used to predict the creep properties of the same polycrystal under required loading conditions. This method simultaneously satisfies the requirements of equilibrium and compatibility over the grain boundaries, and is self-consistent. The proposed method was applied to calculate the creep strains of a 2618-T61 Aluminum alloy under pure shear, combined stress and nonradial loading; the results obtained were in good agreement with the test data.

Improved tensile creep properties of yttrium- and lanthanum-doped alumina: a solid solution effect

2001 ◽  
Vol 16 (2) ◽  
pp. 425-429 ◽  
Author(s):  
Junghyun Cho ◽  
Chong Min Wang ◽  
Helen M. Chan ◽  
J. M. Rickman ◽  
Martin P. Harmer
Keyword(s):  
Solid Solution ◽  
Steady State ◽  
Creep Behavior ◽  
Solubility Limit ◽  
Steady State Creep ◽  
Tensile Creep ◽  
Creep Properties ◽  
Uniform Microstructure ◽  
Equiaxed Grains ◽  
Rare Earth Doped

The tensile creep behavior of yttrium- and lanthanum-doped alumina (at dopant levels below the solubility limit) was examined. Both compositions (100 ppm yttrium, 100 ppm lanthanum) exhibited a uniform microstructure consisting of fine, equiaxed grains. The creep resistance of both doped aluminas was enhanced, compared with undoped alumina, by about two orders of magnitude, which was almost the same degree of improvement as for materials with higher dopant levels (in excess of the solubility limit). In addition, measured creep rupture curves exhibited predominantly steady-state creep behavior. Our results, therefore, verified that the creep improvement in these rare-earth doped aluminas was primarily a solid-solution effect.

Latent hardening in single crystals. II. Analytical characterization and predictions

1991 ◽  
Vol 435 (1893) ◽  
pp. 21-41 ◽  
Keyword(s):  
Low Temperature ◽  
Single Crystals ◽  
Programming Algorithm ◽  
Loading Test ◽  
Slip Rates ◽  
Crystalline Materials ◽  
Analytical Characterization ◽  
History Of ◽  
Latent Hardening ◽  
Good Agreement

Constitutive equations are developed that characterize the multiple-slip behaviour of crystalline materials at low temperature. A matrix of instantaneous hardening moduli that relate the rate of hardening on each slip system to all slip-rates is proposed based upon well-known observations and the latent hardening experiments reported in Part I. In general, these moduli depend on the history of slips. Simulations of various behaviours are presented for FCC single crystals (copper) that are in good agreement with observations. These include, for example, stress-strain curves in a uniaxial loading test, hardening rate variations with respect to initial orientation, latent hardening, tensile overshoot and secondary slips. Numerical calculations are facilitated using an extremum principle and a modified quadratic programming algorithm.

scholarly journals Tensile Creep Properties of Cr-Si Alloys at 980 °C in Air—Influence of Ge and Mo Addition

Metals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1072
Author(s):  
Petra Pfizenmaier ◽  
Anke Silvia Ulrich ◽  
Mathias C. Galetz ◽  
Uwe Glatzel
Keyword(s):  
Creep Behavior ◽  
Alloy Composition ◽  
Constant Load ◽  
Ternary Alloys ◽  
Tensile Creep ◽  
Chromium Nitride ◽  
Creep Properties ◽  
Alloying Additions ◽  
Nitride Formation ◽  
The Impact

The tensile creep behavior of Cr-Si alloys with Cr ≥ 91 at.% was investigated in air at 980 °C with a constant load of 50–100 MPa. Additionally, the influence of substitutional alloying additions of 2 at.% Ge and Mo, leading to ternary alloys was studied. The addition of Ge or Mo results in an improvement in creep strength, with the highest strength achieved with addition of Mo. For longer creep exposure times a strong effect is observed, because of severe nitrogen uptake from the air, depending on alloy composition. Based on the results a novel mechanism for the impact of chromium nitride formation on the creep behavior is proposed.

The Effect of Molybdenum on the Creep Behavior of Orthorhombic Titanium Aluminides

2002 ◽  
Author(s):  
Dominique A. Shepherd ◽  
Vijay K. Vasudevan
Keyword(s):  
Creep Behavior ◽  
Titanium Aluminide ◽  
Creep Resistance ◽  
Titanium Aluminides ◽  
Tensile Creep ◽  
Atomic Fraction ◽  
Beta Transus ◽  
Creep Properties ◽  
Orthorhombic Titanium ◽  
Transus Temperature

The effect of molybdenum additions on the creep properties of two orthorhombic titanium aluminide materials, Ti-22Al-26Nb and Ti-22Al-24.5Nb-1.5Mo (% atomic fraction), has been investigated. Heat treatments below the beta transus temperature followed by a 16-hour ageing treatment produced similar microstructures. Using the similar microstructures (consisting of O laths in a B2 matrix with α2 dispersed at B2 grain boundaries) for the two compositions, tensile creep testing was conducted under stresses of 68 MPa, 160 MPa, and 197 MPa at temperatures of 590 °C and 760 °C. The creep results demonstrated the favorable effects of Mo on creep resistance in these orthorhombic titanium aluminides. Due to similar microstructures, results also suggested that improvements have been substructural, rather than purely microstructural, in nature.

Structure Dependence of Tensile Creep Behavior in Thermo-Mechanically-Treated Ti-50Mol%Al Intermetallics

1990 ◽  
Vol 213 ◽  
Author(s):  
Tohru Takahashi ◽  
Hiroshi Oikawa
Keyword(s):  
Creep Behavior ◽  
Tensile Creep ◽  
Ingot Metallurgy ◽  
Structural Effects ◽  
Creep Life ◽  
Cast Material ◽  
Creep Properties ◽  
Structure Dependence ◽  
Creep Characteristics

ABSTRACTTensile creep properties have been studied in Ti-50mol%Al intermetallics prepared by ingot metallurgy. Four types of structure were obtained in as-cast material (C), homogenized material (CA), isothermally forged material (F) and forged-and-recrystallized material (FA). Structural effects was investigated by comparing creep properties such as minimum creep rates, fracture strains and creep life among C, CA, F, and FA materials. Creep characteristics were strongly dependent upon the structure.

Dislocation structures around SiO2 Particles in aged Cu-Cr-SiO2

1978 ◽  
Vol 36 (1) ◽  
pp. 594-595
Author(s):  
N.J. Long ◽  
M.H. Loretto ◽  
C.H. Lloyd
Keyword(s):  
Flow Stress ◽  
Single Crystals ◽  
Room Temperature ◽  
Thin Foil ◽  
Age Hardening ◽  
Dispersion Strengthening ◽  
Accurate Picture ◽  
The Matrix ◽  
Very High ◽  
Good Agreement

IntroductionThere have been several t.e.m. studies (1,2,3,4) of the dislocation arrangements in the matrix and around the particles in dispersion strengthened single crystals deformed in single slip. Good agreement has been obtained in general between the observed structures and the various theories for the flow stress and work hardening of this class of alloy. There has been though some difficulty in obtaining an accurate picture of these arrangements in the case when the obstacles are large (of the order of several 1000's Å). This is due to both the physical loss of dislocations from the thin foil in its preparation and to rearrangement of the structure on unloading and standing at room temperature under the influence of the very high localised stresses in the vicinity of the particles (2,3).This contribution presents part of a study of the Cu-Cr-SiO2 system where age hardening from the Cu-Cr and dispersion strengthening from Cu-Sio2 is combined.

Measurement of growth rates for single crystals and pressed tablets of CuSO4.5 H2O on a rotating disc

1989 ◽  
Vol 54 (11) ◽  
pp. 2951-2961 ◽  
Author(s):  
Miloslav Karel ◽  
Jaroslav Nývlt
Keyword(s):  
Growth Rate ◽  
Single Crystal ◽  
Single Crystals ◽  
Growth Rates ◽  
Diffusion Coefficients ◽  
Preferred Orientation ◽  
Rotating Disc ◽  
Dissolution Rates ◽  
Rates Of Growth ◽  
Good Agreement

Measured growth and dissolution rates of single crystals and tablets were used to calculate the overall linear rates of growth and dissolution of CuSO4.5 H2O crystals. The growth rate for the tablet is by 20% higher than that calculated for the single crystal. It has been concluded that this difference is due to a preferred orientation of crystal faces on the tablet surface. Calculated diffusion coefficients and thicknesses of the diffusion and hydrodynamic layers in the vicinity of the growing or dissolving crystal are in good agreement with published values.

Latent hardening of doped alkali halide single crystals

1978 ◽  
Vol 46 (1) ◽  
pp. 107-115 ◽  
Author(s):  
R. Steinbrech ◽  
W. Skrotzki ◽  
P. Haasen
Keyword(s):  
Single Crystals ◽  
Alkali Halide ◽  
Latent Hardening
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