Strengthening of Ni3Al by Ternary Additions

1986 ◽  
Vol 81 ◽  
Author(s):  
F. Heredia ◽  
D. P. Pope
Keyword(s):  
Flow Stress ◽  
Dislocation Core ◽  
Uniaxial Stress ◽  
Lattice Parameter ◽  
Strength Increase ◽  
Dominant Mechanism ◽  
Wide Range ◽  
Stress Asymmetry ◽  
Ternary Additions ◽  
Octahedral Slip

AbstractIt is important for a number of reasons to have a basic understanding of the mechanisms by which ternary additions strengthen Ni3Al. First of all, since the basic strength-controlling mechanisms in pure Ni3Al are different from those in pure metals and substitutional solid solutions, it is expected that the mechanisms of solid solution strengthening will also be different in Ni3Al. Secondly, such an understanding will provide valuable insights into the properties of nickel-base superalloys in which Ni3Al is a key constituent. In addition, since new alloys based on an ordered Ni3Al matrix are being developed, it is important to understand the strengthening mechanisms in such alloys. In the present study, flow stress measurements have been performed on single crystals of Ni3Al containing additions of Hf and Ta, and on binary Ni rich, Ni3A1 used as a reference alloy. The data have been collected over a wide range of temperatures, for different orientations within the unit triangle, and as a function of the sense of the applied uniaxial stress. The effect of such additions on the critical resolved shear stress (CRSS) for octahedral slip has been determined and combined with previous data. An attempt is then made to clarify whether a lattice parameter/modulus mismatch effect or a dislocation core effect is the dominant mechanism for the strength increase with compositional changes. It appears that a lattice parameter/modulus mismatch is the dominant mechanism for orientations in which the tension/compression flow stress asymmetry disappears.

Plastic Flow of L12 Ordered Alloys

1984 ◽  
Vol 39 ◽  
Author(s):  
D. P. Pope ◽  
V. Vitek
Keyword(s):  
Flow Stress ◽  
Plastic Strain ◽  
Dislocation Core ◽  
Uniaxial Stress ◽  
Cross Slip ◽  
Slip Model ◽  
Unusual Behavior ◽  
Solid Solution Strengthening ◽  
Ordered Alloys ◽  
The Cross

ABSTRACTThe flow stress of many L12 ordered alloys has a very unusual temperature dependence: the flow stress increases with increasing temperature. This unusual behavior is related to the nature of dislocation dissociation and core structure. The flow stress increase is the result of thermally activated cross slip of [101] screw dislocations to the (010) plane which is accompanied by a transformation of the dislocation core from a glissile to a sessile form. Thus dislocations which are mobile on (111) planes become immobile after cross-slip into (010) planes. The dependence of the flow stress on temperature, orientation and sense of the applied uniaxial stress will be discussed in the light of this cross slip model for Ni3Al, Ni3Ga and for γ/γ′ nickel base superalloys.The response of Ni3Al to cyclic plastic strains (plastic strain controlled fatigue) will also be shown to be in accord with the cross slip model. The mean stress in such a test becomes compressive or tensile, depending on the orientation of the sample, even though the net plastic strain is zero after each cycle.The strengthening of Ni3Al by ternary additions will also be discussed. It will be shown that ordinary solid solution strengthening models are not applicable but that the cross slip model can also be applied.Finally, it will be shown that dislocation core simulation studies predict that there should also be a class of L12 ordered alloys that show a “normal” flow stress-temperature behavior, i.e., the flow stress increases at low temperatures. The results of our studies on Pt3Al will be used to illustrate this behavior.

2D X-ray diffraction and molecular modelling of the crystalline structure of polyesters under uniaxial stress

2021 ◽  
pp. 096739112199822
Author(s):  
Ahmed I Abou-Kandil ◽  
Gerhard Goldbeck
Keyword(s):  
Crystalline Structure ◽  
Molecular Modelling ◽  
Three Dimensional ◽  
Uniaxial Stress ◽  
X Ray Diffraction ◽  
X Ray ◽  
Wide Range ◽  
Modelling Techniques ◽  
Diffraction Patterns

Studying the crystalline structure of uniaxially and biaxially drawn polyesters is of great importance due to their wide range of applications. In this study, we shed some light on the behaviour of PET and PEN under uniaxial stress using experimental and molecular modelling techniques. Comparing experiment with modelling provides insights into polymer crystallisation with extended chains. Experimental x-ray diffraction patterns are reproduced by means of models of chains sliding along the c-axis leading to some loss of three-dimensional order, i.e. moving away from the condition of perfect register of the fully extended chains in triclinic crystals of both PET and PEN. This will help us understand the mechanism of polymer crystallisation under uniaxial stress and the appearance of mesophases in some cases as discussed herein.

The Use of Controlled Dissolution Glasses to Consolidate and Create Permeable or Impermeable Minerals in Formation

2021 ◽  
Author(s):  
Max Olsen ◽  
Ragni Hatlebakk ◽  
Chris Holcroft ◽  
Arne Stavland ◽  
Nils Harald Giske ◽  
...  
Keyword(s):  
Tensile Strength ◽  
Oil And Gas ◽  
Stable Solution ◽  
Oil And Gas Industry ◽  
Post Treatment ◽  
Strength Increase ◽  
Glass Technology ◽  
Nuclear Waste Storage ◽  
Wide Range ◽  
Glass Compositions

Abstract Scope Controlled dissolution glasses form a permanent consolidating mineral matrix inside formations with either permeable or impermeable properties. The unique solution has a low injection viscosity and can be easily injected into a wide range of formations. The application method is simple and does not require multiple fluids or pre- and post-flushing. This paper focuses on the benefits of controlled dissolution glasses and potential applications in the oil and gas industry. Methods, Procedures, Process Controlled dissolution glasses have been researched extensively by Glass Technology Services (GTS) since 1999 for the biomedical industry, nuclear waste storage industry, and defense and aerospace industries. GTS together with operators have been performing research and development for the oil industry over the last 10 years. The research investigated different glass compositions to determine their injectability and change in formation properties post-treatment. Sandstone, chalk, and shale formations were used in the testing. Flow testing using a Hoek cell and a core flood apparatus was used to determine the post-treatment permeability. For post-treatment strength measurement, Brazilian tensile strength tests and modified cone penetration tests were used to determine tensile strength and shear strength respectively. The testing evaluated different mixing fluids, such as water and different brines, compatibility, corrosion testing, and concentrations. Results, Observations, Conclusions The testing identified different glass compositions and concentrations that are suitable for different applications and formations. Certain glass compositions increase tensile strength significantly while also maintaining the permeability in the formation. Other glass compositions have similar tensile strength increase, but result in an impermeable seal. The liquid glass solutions react with the formation to form a mineral precipitation inside the formation. The reaction with the formation occurs quickly at downhole conditions, within hours of placement. The glass can be mixed with water and variety of brines to form a stable solution across a range of densities. The testing and results to date have laid the foundation for use in a variety of consolidation and P&A applications in oil and gas wells. Testing is ongoing for a chalk and sandstone consolidation solution and for a sealing solution. Novel/Additive Information These novel glass solutions can solve many of the production and instability challenges that plague weak formations. The glasses can be injected into very low permeability formation to either seal or consolidate.

Flow stress asymmetry in cyclic deformation of molybdenum crystals

1974 ◽  
Vol 8 (8) ◽  
pp. 931-935 ◽  
Author(s):  
B Etamad ◽  
F Guiu
Keyword(s):  
Flow Stress ◽  
Cyclic Deformation ◽  
Stress Asymmetry

Rapid structural and chemical characterization of ternary phase diagrams using synchrotron radiation

2003 ◽  
Vol 18 (10) ◽  
pp. 2522-2527 ◽  
Author(s):  
E. D. Specht ◽  
A. Rar ◽  
G. M. Pharr ◽  
E. P. George ◽  
P. Zschack ◽  
...  
Keyword(s):  
Synchrotron Radiation ◽  
Chemical Characterization ◽  
Lattice Parameter ◽  
Ternary Alloys ◽  
Charge Coupled Device ◽  
Ternary Phase Diagrams ◽  
Wide Range ◽  
Combinatorial Materials ◽  
A Charge

A technique based on synchrotron radiation was developed that allows for rapid structural and chemical characterization of ternary alloys over a wide range of composition. The technique was applied to isothermal sections of the Cr–Fe–Ni system grown on Al2O3(0001) sapphire substrates by sequential deposition of layers of graded.thickness followed by annealing to interdiffuse the elements. A film spanning the Cr–Fe–Ni ternary system was measured in 4 h at a resolution of 2 at.% by rastering the sample under a focused beam of synchrotron radiation while simultaneously measuring the diffraction pattern with a charge-coupled device detector to determine crystallographic phases, texture, and lattice parameters and also measuring the x-ray fluorescence with an energy-dispersive detector to determine elemental composition. Maps of phase composition and lattice parameter as a function of composition for several annealing treatments were found to be consistent with equilibrium values. The technique will be useful in combinatorial materials design.

A High-Precision Kossel Camera for Research and Routine Analytical Use

1968 ◽  
Vol 12 ◽  
pp. 188-207
Author(s):  
T. E. Reichard
Keyword(s):  
Electron Probe ◽  
Lattice Parameter ◽  
Electrical Contacts ◽  
Significant Feature ◽  
X Ray ◽  
Source Distance ◽  
Wide Range ◽  
Single Pattern ◽  
Box Structure ◽  
Ray Projection

AbstractA transmission Kossel camera unit has been built for the Cambridge Mark II electron probe. It replaces the standard specimen stage assembly, and is useful also for regular electron probe microanalysis and projection microradiography.Its design extends the attainable precision of lattice parameter measurements to near-ultimate practical limits, while providing special features for research studies, and speed, flexibility, and convenience of operation for routine analytical use on a wide variety of specimens, particularly semiconductor materials.The most significant feature is a novel X-ray projection box structure which casts index-mark images on each pattern. From these images, the exact source distance and pattern-center positions are determined for each exposure. Precise crystal-piane spacings can be measured, therefore, from conic intersections anywhere on the exposed area of the plate. Since the conics need not be in any particular favorable location, it is not necessary to achieve an exact orientation of the sample. Precise lattice dimensions in several different crystallographic directions are obtainable from a single pattern exposure if their various sensitive conics appear anywhere on the pattern. The need for a reference measurement of “fixed” conics is eliminated, being replaced by a much more precise measurement of very sharp, high contrast, widely spaced index-mark images.Camera length is 12.5 cm and exposed pattern area is 9.4 cm square. Glass photo plates are used to eliminate errors due to film shrinkage and warp. A removable cassette holds ten 4″×5″ glass plates, interchangeableiunder vacuum. The X-ray shutter has ten positions for making exposure-time sequences. The specimen stage is thermostatted to ±0.01° C, controllable from room temperature up to 200° C, and;temperature is measured to +0.005° C. Stage movement range is 25mmx50mn, with coordinates shown on external digital dials. Interchangeable inserts provide for a wide range of specimen sizes and shapes. Electrical contacts to the specimen are available.An externally adjustable plate holds 24 different target foils or target-filter combinations for pseudo-Kossel patterns. An open position provides for true Kossel work and for scatteredelectron image viewing.

scholarly journals On the Zener–Hollomon Parameter, Multi-Layer Perceptron and Multivariate Polynomials in the Struggle for the Peak and Steady-State Description

Metals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1413 ◽  
Author(s):  
Petr Opěla ◽  
Petr Kawulok ◽  
Ivo Schindler ◽  
Rostislav Kawulok ◽  
Stanislav Rusz ◽  
...  
Keyword(s):  
Steady State ◽  
Flow Stress ◽  
Flow Curve ◽  
Multivariate Polynomials ◽  
Multi Layer Perceptron ◽  
Stress Evolution ◽  
Flow Curves ◽  
Hollomon Parameter ◽  
Wide Range ◽  
Stress Models

Description of flow stress evolution, specifically an approximation of a set of flow curves acquired under a wide range of thermomechanical conditions, of various materials is often solved via so-called flow stress models. Some of these models are associated with a description of significant flow-curve coordinates. It is clear, the more accurate the coordinates description, the more accurate the assembled model. In the presented research, Zener–Hollomon-based relations, multi-layer perceptron networks and multivariate polynomials are employed to describe the peak and steady-state coordinates of an Invar 36 flow curve dataset. Comparison of the utilized methods in the case of the studied alloy has showed that the suitable description is given by the multivariate polynomials although the Zener–Hollomon and perceptron networks also offer valuable results.

Sensitivity Analysis of the Material Flow Stress in Machining

Manufacturing ◽  
2003 ◽  
Author(s):  
Ning Fang
Keyword(s):  
Sensitivity Analysis ◽  
Flow Stress ◽  
Aluminum Alloys ◽  
Strain Rate ◽  
Strain Hardening ◽  
Material Flow ◽  
Chemical Compositions ◽  
Wide Range ◽  
Strain Rate Hardening ◽  
Factor Governing

Among the effects of strain hardening, strain-rate hardening, and temperature softening, it has long been argued about which effect is predominant in governing the material flow stress in machining. This paper compares four material constitutive models commonly employed, including Johnson-Cook’s model, Oxley’s model, Zerilli-Armstrong’s model, and Maekawa et al.’s model. A new quantitative sensitivity analysis of the material flow stress is performed based on Johnson-Cook’s model covering a wide range of engineering materials, including plain carbon steels with different carbon contents, alloyed steels, aluminum alloys with different chemical compositions and heat treatment conditions, copper and copper alloys, iron, nickel, tungsten alloys, etc. It is demonstrated that the first predominant factor governing the material flow stress is either strain hardening or thermal softening, depending on the specific work material employed and the varying range of temperatures. Strain-rate hardening is the least important factor governing the material flow stress, especially when machining aluminum alloys.

THE FOUNDATIONS OF CONTINUUM DAMAGE MECHANICS

2019 ◽  
Vol 6 (1) ◽  
Author(s):  
Siamak Yazdani ◽  
Sevenn Borgersen ◽  
Asli Pelin Gurgun ◽  
Hossein Nazari
Keyword(s):  
Damage Mechanics ◽  
Nonlinear Behavior ◽  
Continuum Damage Mechanics ◽  
Uniaxial Stress ◽  
Internal Variable ◽  
Continuum Damage ◽  
Damage Potential ◽  
Variable Theory ◽  
Wide Range ◽  
The Many

Damage Mechanics has become a useful theory in describing the nonlinear behavior of solids driven by the nucleation and growth of cracks and microcracks. This approach, based on the first principles of mechanics and thermodynamics, has also been combined with classical theories of plasticity to address a wide range of loading applications. In spite of the many different damage mechanics models and representations that are proposed, the foundation of damage mechanics is not well understood or at least not thoroughly published giving rise to the many inaccurate definitions and formulations. The intent of this paper is to provide the background of the continuum damage mechanics outlining the fundamentals on which this field theory is set up. The internal variable theory of continuum thermodynamics is reviewed and is shown that with Legendre transformation technique, various potential functions can be developed for damage mechanics formulation in either stress or strain space. The concept of constrained or neighboring equilibrium state is also introduced and is explained. The paper will conclude with the derivation of the general damage potential and a suggestion is given for the isotropic damage formulation with the resulting uniaxial stress-strain relation.

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