bluuebunny/crossref_metadata_2025 huggingface dataset:
Role of Bi and Ca Additions in Controlling the Microstructure of Sr-Modified 319 Alloys
Authors: El Hadad S. , Samuel A.M. , Samuel F.H. , Doty H.W. , Valtierra S.
Published: March 2009

The role of bismuth (50 to 9000 ppm) and calcium (50 to 200 ppm) additions on the microstructural characteristics in Sr-modified 319 alloys (with/without 0.4 wt% Mg addition) were investigated using optical and electron microscopy, and image analysis. It was found that the modification effect of Sr continuously diminished with Bi addition up to ~3000 ppm Bi; further Bi addition led to the modification of the Si particles due to the presence of Bi. In the Ca-containing alloys, a coarse eutectic Si structure resulted with Ca additions of 50 ppm, due to the formation of Alx(Ca,Sr)Siy compounds. Increased Ca additions (up to 200 ppm) did not alter the Si particle size. The Alx(Ca,Sr)Siy phase particles appeared in rod-like form in the Sr-modified alloys and in plate-like form in the 319+0.4 wt% Mg alloys. MgO, Al2O3, and AlP particles appear to act as nucleants for the precipitation of the plate-like Alx(Ca,Sr)Siy phase.
Hydrogen Permeation Behaviour in Aluminium Alloys
Authors: Izumi T. , Itoh Goroh , Itoh Nobuhide , Sasaki Y.
Published: March 2009

Aluminum alloy is one of the candidates for the liners of compressed hydrogen tank mounted
to fuel cell vehicles. It is crucial to elucidate the behavior of hydrogen in the alloy sheet with one side
being exposed to hydrogen gas. In the present work, using the hydrogen microprint technique, in 6061
and 7075 aluminum alloy sheets, relationship between hydrogen pressure and the molar quantity of
hydrogen emitted from the inside has been investigated. Under any pressure, the quantity of emitted
hydrogen is about 10 times smaller in the 7075 alloy than in the 6061 alloy. This indicates that the
amount of hydrogen atoms accumulating in the 7075 alloy may be much larger than that in the 6061
alloy.
Electrical Resistivity Measurements: A Sensitive Tool for Studying Aluminium Alloys
Authors: Raeisinia B. , Poole Warren J.
Published: March 2009

This paper examines the challenges which are encountered when using electrical resistivity measurements for characterization of microstructures in aluminum alloys. Experimental examples are provided of electrical resistivity studies conducted on two aluminum alloys, a heattreatable alloy (AA6111) and a non-heat-treatable alloy (AA5754), which demonstrate how the technique can be used to characterize changes in the microstructure. Results on AA6111 show that the dependence of the measurement on solute atoms and fine scale precipitates makes deconvolution of the resistivity signal non-trivial and therefore, utilization of supplementary technique(s) in conjunction with electrical resistivity measurements is essential. In the next example, room temperature electrical resistivity measurements as a function of cold work for AA5754 illustrate a larger resistivity contribution from dislocations in this alloy as compared to that reported for pure aluminum. The interaction of solutes and dislocations is cited as the possible source for the increased dislocation contribution.
Formability and Bake-Hardenability of Al-Mg-Cu Alloy Sheets by Asymmetric Warm Rolling
Authors: Suzuki Yoshikazu , Omura Tomoya , Hirosawa Shoichi , Sato Tatsuo
Published: March 2009

In this study, asymmetric warm rolling (AWR) has been applied to improve the formability
of bake-hardenable Al-3mass%Mg-1mass%Cu-(Ag) alloy sheets. The T4 sheets by the AWR are
superior to those by conventional rolling (CR) in Lankford value and drawability. This improvement is
caused by a change in the recrystallization texture to have a predominant orientation close to
{111}//ND. The unusual texture for recrystallized aluminum alloy sheets is due to the shear
deformation introduced during AWR. The Al-Mg-Cu alloy sheets by AWR have been confirmed to
possess combined bake-hardenability and the improved formability. However, the bake-hardening
response of the Al-Mg-Cu alloy by AWR is slightly inferior to that of the identical alloy by CR.
Modeling Structure of Al-Sn Alloy
Authors: Padhi P. , Anand Santosh K. , Kar Debashis , Ghosh S. , Panigrahi Sushanta Kumar
Published: March 2009

In metallic alloys, the formation of macrostructure involves different length
and time scales. The macrostructure strongly influences the mechanical properties of the
materials. Modeling of macrostructure provides valuable insights for tailoring of the
macrostructure. In the present study simulation of macrostructure in Al-22Sn has been
carried out. Expression for nucleation rate and growth rate were tuned to get a match with
the experimentally observed macrostructure. The study incorporates the motion of grains
due to Brownian motion. Incorporation of Brownian motion resulted in more uniform
distribution locally, which has been experimentally observed. Both simulation and
macrograph showed few columnar grains and absence of sharp columnar to equiaxed
transition.
Static and Dynamic Grain Growth in Single-Phase Aluminium
Authors: Jazaeri H. , Humphreys John F. , Bate Pete S.
Published: March 2009

Al-0.1Mg with a 3μm grain size was deformed in channel die plane strain compression at temperatures up to 200oC. It was found that the reduction in grain thickness was significantly less than that predicted from geometric considerations, and at larger strains, a minimum high angle grain spacing, which was equal to the crystallite size was achieved. The velocity of the high angle boundaries during this process is very many orders of magnitude larger than that predicted for curvature driven grain growth, and some possible explanations for this are discussed.
Boundary Mobilities in Binary Al-Mn Alloys
Authors: Driver Julian H. , Maurice Claire , Barou F. , Lens Arnaud
Published: March 2009

This paper described new characterization methods and data to quantify the influence of solute atoms on grain boundary and sub-grain boundary mobilities in Al-Mn alloys with a view to their integration into recovery and recrystallization modelling. Detailed SEM measurements of grain boundary mobilities during recrystallization have been made by in-situ annealing experiments on cold deformed Al – 0.1 and 0.3wt.% Mn binary alloys. Stored energies are estimated from the sub-grain sizes and misorientations and the boundary velocities directly measured in the temperature range 200-450°C. It is shown that in many cases good agreement with the Cahn, Lücke, Stüwe model for solute drag is obtained, e.g. the activation energies are intermediate between those of boundary and volume solute diffusion. Some particular cases of rapid growth occur in Al-0.1%Mn indicating boundary breakaway from solute clouds. A complementary study of sub-grain boundary mobilities has started on the same alloys; in this case the average mobilities are estimated from FEG-SEM growth data for the average sub-grain size for temperatures in the range 150-300°C. The results are compared with some previous data on Al-Si and show similar rates.
Changes in Grain Size Distribution of a Submicron Grained Al-Sc Alloy during High Temperature Annealing
Authors: Burhan N. , Ferry Michael
Published: March 2009

Severe plastic straining is an established method for producing submicron grain (SMG) structures in alloys. However, the development of such a fine grained structure in single-phase alloys is usually futile if they are to be exposed or processed at elevated temperatures. This is a direct consequence of the natural tendency for rapid and substantial grain coarsening which completely removes the benefits obtained by grain refinement. This problem may be avoided by the introduction of nanosized, highly stable particles in the metal matrix. In this work, a SMG structure was generated in an Al-0.3 wt.% Sc alloy by Equal Channel Angular Pressing (ECAP). The alloy was prepared initially to produce a fine grained microstructure exhibiting a large fraction of high angle grain boundaries and a dispersion of nanosized Al3Sc particles. The evolution of microstructure during annealing at temperatures up to 550 °C was examined in detail and grain size distributions generated from the data. It was shown that grain coarsening is rapid at temperatures above 450 °C and the initial log-normal grain size distribution exhibiting low variance and skewness was altered considerably. The statistical information generated from the grain size distributions confirms that discontinuous grain coarsening occurs in this alloy only at temperatures greater than 500 °C.
Recrystallization Behaviour in Twin-Roll Continuous Cast Al-Fe-Ni Alloy
Authors: Niikura Akio , Kawahara Akira , Kimura Go , Doko Takeyoshi
Published: March 2009

Factors controlling the recrystallization of a continuous cast Al-Fe-Ni alloy were investigated by analyzing microstructure, grain structure, texture, and electron backscattering patterns. The texture of an as-rolled sample heated at 400°C was similar to that of a sample at the reduction ratio of 50% after intermediate annealing at 550°C. The as-rolled samples had a strong (213)[36-4] (S-type) orientation that was changed to a strong (130)[3-12] (QQ-type) orientation by heating at 400°C. This recrystallization looks like continuous recrystallization. Discontinuous recrystallization due to particle-stimulated nucleation is suppressed by the fine dispersion of Al-Fe-Ni-Si particles that form during casing and intermediate annealing, and stabilize the grain and subgrain structure. We think that a course initial grain structure and moderate level of strain level are the important factors promoting continuous recrystallization in this alloy.
Geometric Misorientation Changes in Aluminium Subjected to Strain Path Change Test
Authors: Avramovic-Cingara G. , McQueen H.J.
Published: March 2009

Specimens of commercial purity aluminum were subjected to a strain path change test
during high temperature deformation. Specimens were deformed at 4000 C and strain rate of 0.1
s-1 up to various strains of 0.2, 0.5, and 1. Then in a strain path change test, specimens were first
deformed to a strain of 0.5, and subsequently deformed to strains of 0.2 and 0. In order to
further the understanding of the deformation mechanisms in aluminum, the subgrain sizes and
misorientations were characterized in detail by comparative studies using optical microscopy in
polarized light (POM), orientation imaging microscopy (OIM/SEM) and transmission electron
microscopy (TEM). The analysis revealed that while subgrain size is relatively insensitive to
strain, overall misorientations increased with increasing strain. These analyses confirmed a
strong bimodal distribution of boundaries during deformation coupled with a low fraction of
medium angle boundaries. The results contribute to the understanding that dynamic recovery in
aluminum maintains subboundaries with low misorientation but as grains elongate and more
subgrain become adjacent to grain boundaries the fraction of high angle boundaries rises.
Characterization of Fe-Rich Intermetallic Phases in a 6xxx Series Al Alloy
Authors: Sha Gang , O'Reilly Keyna , Cantor Brian
Published: March 2009

Intermetallic phases formed during directional Bridgman solidification of a 6xxx series Al alloy in the growth velocity range 5-120 mm/min have been characterised using conventional and high-resolution transmission electron microscopy. Cubic αc-AlFeSi and β-AlFeSi were always present in the alloy, but Al13Fe4 was only observed at 5mm/min and monoclinic αT-AlFeSi at 80 mm/min. Cubic αc-AlFeSi was observed to have a variety of morphologies resulting from flexibility in its growth mechanisms. β-AlFeSi with twins and faults showed strongly anisotropic growth by steps, resulting in its platelet morphology. Occasionally blocky β-AlFeSi particles were observed particularly at 30-60 mm/min, suggesting that other mechanisms could influence their morphology. Two types of composite particles, β-AlFeSi/Al13Fe4 and β-AlFeSi/cubic αc-AlFeSi, were observed in this alloy, and likely formed by two quasi-peritectic reactions.
The Impact of Partial Drainage on Chemical Composition of 356 Al-Si Alloy
Authors: Nafisi S. , Lashkari O. , Langlais Joseph , Ghomashchi R.
Published: March 2009

A novel method is introduced to investigate the macro-segregation in 356 Al-Si alloy. In this method, a portion of the remaining liquid is extracted during solidification of the alloy from the bottom orifice of a cylindrical sample. Different parts of the sample plus the extracted material are chemically analyzed and a good correlation between the chemical composition and the predicted values from binary Al-Si diagram was obtained. Comparing the chemical composition of the decanted alloy in the cast piece with those of the 356 standard range has shown that even with 15% of the liquid extraction, the composition of the alloy is still within the intended range.
Nucleation-Mediated Structural Refinement and Aluminium Alloy Design
Authors: Muddle Barry C. , Nie Jian Feng
Published: March 2009

Regardless of whether it is cast microstructure, the grain structure that is the product of thermomechanical processing or the nanoscale dispersions of strengthening second-phase particles, it is inescapable that the structural scale that controls mechanical properties in Al alloys is determined primarily by processes of nucleation during either solidification, recrystallisation or solid-state phase transformation. In those advanced alloys with bulk amorphous or nanocrystalline structure, production of an amorphous precursor is reliant on initial suppression of the nucleation of crystallisation, and subsequent controlled nucleation of dispersed nanocrystals within amorphous matrix. The processes of nucleation that control structural scale in modern Al alloys are briefly reviewed, with a focus on potential for further structural refinement and advances in properties.
HRTEM Study of Precipitates in Al-Mg-Si and Al-Mg-Ge Alloys
Authors: Matsuda Kenji , Ikeno Susumu , Munekata Teruyoshi
Published: March 2009

In this work, the crystal structure of the rod-shaped precipitate in aged Al -1.0 mass%
Mg2Ge alloy at 523 K has been investigated by high resolution transmission electron microscopy
(HRTEM), electron diffraction technique and energy dispersive X-ray spectroscopy (EDS). The
rod-shaped precipitate in its alloy has showed the similar arrangement of bright dots in its HRTEM
images and selected area diffraction pattern (SADP) to those of the b’-phase in Al-Mg2Si alloy. But a
lattice constant of this precipitate in Al-Mg2Ge alloy was slightly larger than the b’-phase in
Al-Mg2Si alloy. In addition, the new metastable phase has been found out in Al-Mg-Ge alloy.
Development of a New 7xxx Ageing Model
Authors: Sigli Christophe
Published: March 2009

A kinetic model has been developed to simulate the precipitate size distribution and the
resulting yield strength during ageing of 7xxx alloys. The η phase is the only one considered. The
kinetic model is mean field: precipitates of different sizes see each other through the average solid
solution. Precipitates are assumed to be homogeneous in concentration and are allowed to change
chemistry. Local equilibrium is assumed at the matrix-precipitate interface; the equilibrium
concentrations are corrected by the curvature effect. Values of the equilibrium concentrations at the
matrix-precipitate interface are solved by an iterative method: the resulting flux for each element
must be compatible with equilibrium conditions and with the changing stoechiometry of the
considered precipitate while maximizing the energy gained. The yield strength is derived from the
precipitate size distribution through a mixture law combining the effect of each individual
precipitate. The model can take into account non-isothermal treatments and can therefore simulate
complicated multi-stage ageing treatment as well as a FSW weld. Results of the model are discussed
and compared measurements.
Modelling Dispersoid Precipitation during Recrystallisation in AA3103
Authors: Lok Zacharias J. , Miroux A. , van der Zwaag Sybrand
Published: March 2009

A diffusion controlled precipitation model based on classical nucleation and growth theory has been implemented to simulate the precipitation kinetics in a hot rolled supersaturated Al- Mn alloy (AA3103). The modelling approach explicitly includes the effect of concurrent recrystallisation on precipitation and considers the simultaneous evolution and interaction of two precipitate populations that vary significantly in size, i.e. constituent particles and dispersoids. Comparison with experimental results shows that this classical modelling approach predicts incorrect nucleus density and too high precipitation rates, which cannot be simply corrected by parameter fitting. Reasons for this discrepancy are discussed in terms of selection of nucleation sites, the effect of diffusion in a multi-component system, various diffusion paths and the possible influence of precipitate shape and size distribution. The model is subsequently altered by introducing two additional parameters that control the Mn solute concentration at the particle-matrix interface. This more phenomenological model is successful in reproducing the experimental precipitation kinetics, both in deformed and undeformed aluminium matrix, and the effect of concurrent recrystallisation for a wide temperature range.
Processing of Aluminium Alloys by Severe Plastic Deformation
Authors: Langdon Terence G.
Published: March 2009

Processing through the application of severe plastic deformation (SPD) has become important over the last decade because it is now recognized that it provides a simple procedure for producing fully-dense bulk metals with grain sizes lying typically in the submicrometer range. There are two major procedures for SPD processing. First, equal-channel angular pressing (ECAP) refers to the repetitive pressing of a metal bar or rod through a die where the sample is constrained within a channel bent through an abrupt angle at, or close to, 90 degrees. Second, high-pressure torsion (HPT) refers to the procedure in which the sample, generally in the form of a thin disk, is subjected to a very high pressure and concurrent torsional straining. Both of these processes are capable of producing metallic alloys with ultrafine grain sizes and with a reasonable degree of homogeneity. Furthermore, the samples produced in this way may exhibit exceptional mechanical properties including high strength at ambient temperature through the Hall-Petch relationship and a potential superplastic forming capability at elevated temperatures. This paper reviews these two procedures and gives examples of the properties of aluminum alloys after SPD processing.
Interaction between Cu and Sn in the Early Stages of Ageing of Al-1.7at.%Cu-0.01at.%Sn
Authors: Bourgeois Laure , Wong Timothy , Xiong X.Y. , Nie Jian Feng , Muddle Barry C.
Published: March 2009

The interaction between vacancies and Sn and Cu solute atoms in an Al-1.7at.%Cu-
0.01at.%Sn alloy was investigated by exploring the effect of incorporating natural ageing into
conventional age hardening treatment. It was found that provided the artificial ageing temperature does
not exceed a critical value between 160°C and 200°C, a narrow window of natural ageing (3-100 h)
will result in a significant acceleration of the age hardening response and no decrease in peak hardness.
Transmission electron microscopy showed that this effect reflects a large and rapid increase in number
density of Cu GP(I) zones, and, to a lesser extent, of θ". The distribution and number density of θ' are
essentially unaffected. Three-dimensional atom probe provided strong evidence that refinement of
GP(I) zone distribution is not due to clustering of Cu atoms onto pre-existing Sn clusters. Instead it
appears to be caused by a subtle interaction between vacancies, Sn and Cu atoms.
Heat Treatment Effect on Properties of Al-Mg-Si-Cu 1370 Alloy
Authors: Kolobnev N.I. , Khokhlatova L.B. , Samokhvalov S.V. , Alekseev A.A. , Sbitneva S.V. , Tararaeva T.I. , Popov V.I.
Published: March 2009

The Russian 1370 Al-Mg-Si-Cu alloy (analogue of 6056) is an advanced material for the
skin and stringers of fuselage. However, these alloys are susceptible to the intercrystalline corrosion
depending on the heat treatment regimes. The investigations of the effect of heating temperature
during the solid solution treatment (530-555)°C and quenching rate, ageing regimes and interval
between the quenching and ageing on the structure and properties of 1370 alloy sheets were performed.
The strengthening β (Mg2Si) -phase and Q (Al5Cu2Mg8Si6) -phase relationship dependence
of the alloy properties is established. Using the dark field electron microscopy which permits to intensify
separate diffraction reflexes of strengthening phases the structure of Q-phase precipitates has
been studied. Optimization of heat treatment of 1370 alloy sheets provided the combination of fracture
toughness characteristic (Kco= 100 MPa√m) high level, the ultimate strength of 400-420 MPa
and intercrystalline corrosion no more 100 μm in depth.
Structure and Mechanical Behaviour of Al-Sc Alloys
Authors: Milman Yu.V.
Published: March 2009

The review of the works devoted to the influence of scandium on the structure, mechanical behavior and corrosion resistance of aluminum alloys is given. The wrought thermally non-hardenable alloys of Al- Mg system and thermally hardenable high-strength alloys of Al-Zn- Mg-Cu system are considered. The influence of Sc on the glass forming ability of amorphous alloys and on the superplastic behavior of aluminum alloys is discussed.
Improvement of Structure and Deformation Behaviour of High Strength Al-Zn-Mg Foam
Authors: Milman Yu.V. , Byakova A.V. , Sirko A.I. , Gnyloskurenko S. , Nakamura T.
Published: March 2009

Metal foams based on high-strength Al-Zn-Mg alloy are promising material for energy
absorption application. The performance of coated calcium carbonate (CaCO3) as foaming agent for
Alporas like route is studied in the present paper by comparison with the conventional titanium
hydride (TiH2). Compressive response of the foams was examined and microstructure of cell wall
was investigated. The advantages of CaCO3–foam are shown and discussed.
Factors Influencing the Heterogeneous Nucleation of θ' in Al-Cu-In Alloy
Authors: Gable Brian M. , Muddle Barry C.
Published: March 2009

The ability to improve mechanical properties through trace alloying additions that enhance the precipitation-hardening response has been a cornerstone of aluminium research and alloy development. It is now known that many of these alloying additions are beneficial (or deleterious) because of their influence on the competitive precipitation kinetics, in many cases arising from the formation of chemical and structural heterogeneities in the matrix. In order to better our understanding of this phenomenon, the earliest stages of microstructural evolution of indium precipitates and θ' plates in an Al-Cu-In ternary alloy have been investigated. Quantitative microstructural characterization reveals that there is a correlation between the size of the pre-existing indium particle and the resulting heterogeneous precipitation kinetics, with larger indium particles favouring θ' precipitation.
Surface Science Studies of the Effect of Al Alloy Microstructure on the Formation of Chromate Coatings
Authors: Kulinich S.A. , Akhtar A.S. , Susac D. , Wong K.C. , Wong P.C. , Mitchell K.A.R.
Published: March 2009

Surface science methods including scanning Auger microscopy (SAM), scanning
electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy
have been used to study the initial growth of chromate conversion coatings on aluminum 2024-T3
alloy, using a coating bath formed by dissolving CrO3, Na2Cr2O7 and NaF in water. The objective
is to learn more about growth mechanism on the different microstructural regions of this alloy
surface, including the second-phase particles and the alloy matrix.
Pitting Corrosion Behaviour of the 6056-T78 Aluminium Alloy
Authors: Bourdet Paul , Blanc Christine , Mankowski Georges , Guillot Jean Bernard
Published: March 2009

The morphology and propagation of corrosion pits on a 6056-T78 aluminum alloy in a
sulfate and chloride-containing solution have been investigated and the influence of different
parameters has been studied: the passivation potential for passive film growth, the pitting potential
i.e. the applied potential during the pitting process and the time for pit propagation. The passivation
potential did not influence the pit morphology and the pit propagation; it only influenced the pit
density. On the contrary, it was found that the pitting potential and the time had a similar influence
on the pit growth. For low pitting potentials or short times, the pit depth to pit radius ratio was high
(about 0.7) whereas it decreased to a value close to 0.4 for higher pitting potentials or longer times.
Nonuniform Temperature Distribution in Adiabatic Shear Band Using Measured Shear Stress-Shear Strain Curve in Torsion of Thin-Walled Tube Aluminium Alloy Specimen and Gradient-Dependent Plasticity
Authors: Wang X.B.
Published: March 2009

Gradient-dependent plasticity where a characteristic length is involved to consider the
microstructural effect (interactions and interplaying among microstructures due to the heterogeneous
texture) and the measured nonlinear shear stress-shear strain curves for different loading strain rates
are used to calculate the distribution of local temperature rise in adiabatic shear band (ASB) for
aluminum-lithium alloy specimen of thin-walled tube in dynamic torsion test. ASB is assumed to
initiate just at peak shear stress in the specimen. The temperature rise in ASB is decomposed into the
uniform temperature rise in strain-hardening stage and the nonuniform temperature rise in
strain-softening stage. The former depends on the measured nonlinear shear stress-shear strain curve
prior to the peak, the density, the work to heat conversion factor and the heat capacity. The latter is
related to the softening branch of the measured nonlinear shear stress-shear strain curve, the internal
length parameter and the physical parameters. For binary Al-Li alloy, the predicted maximum
temperatures in ASB are 413K at strain rate of 2000s-1 and 433K at strain rate of 2600s-1. These peak
temperatures are lower than the recrystallization and phase transformation temperatures. Higher
loading strain rate results in higher pre-peak and post-peak temperature rises, steeper profile of local
temperature and higher peak local temperature in ASB. These predictions qualitatively agree with the
previously analytical solution for ductile metal exhibiting linear strain-softening behavior beyond the
peak shear stress based on gradient-dependent plasticity.
Through-Process Texture Simulation for Aluminium Sheet Fabrication
Authors: Gottstein Günter , Crumbach Mischa , Neumann L. , Kopp R.
Published: March 2009

We introduce a simulation procedure for through-process texture and anisotropy prediction, in particular for AA5182 sheet production from hot rolling through cold rolling and annealing. The FEM package ‘T-Pack’ based on the software LARSTRAN served as a process model. It was combined with physics based microstructure models for deformation texture (GIA), work hardening (3IVM), nucleation texture (ReNuc), and recrystallization texture (StaRT). The terminal sheet texture was used for a FEM simulation of cup drawing. A new concept of interactively updated texture based yield locus predictions was employed. The simulation predictions were compared to experimental data. The procedure can be applied to a wide variety of Aluminum alloys.
Initial Oxidation Rate Law of Binary Alloys by Hopping Migration of Cations
Authors: Ishikawa Ikuo , Nanjo Hiroshi
Published: March 2009

We propose a multi-element hopping model, which shows the flux equations of various
cations under high electric field. The model is applied to the initial oxidation of binary alloys
which produces a homogeneous single layer solid solution oxide film. The flux equations by this
model for two kinds of cations were substituted to the oxidation growth rate definition equation.
Finally, it is shown that the initial oxidation rate law of dilute binary alloys can be obtained as a
type of inverse logarithmic rate law.
The Effect of Gas Flow Rate on the Oxide Scale Morphology of a 10%Cr-Ferritic Steels in Ar-H2O and Ar-H2-H2O Mixtures
Authors: Zurek J. , Michalik M. , Singheiser Lorenz , Quadakkers W.Joe
Published: March 2009

The oxidation behaviour of a Ferritic 10%Cr steel in Ar-H2O mixtures was investigated at 650°C. The studies aimed at elucidating the effect of water vapour content as well as the gas flow rate on the mechanisms of oxide scale formation. An important observation of the present investigation is, that H2 produced by the reaction of water vapour with the steel, can play a significant role in the oxidation process. It affects the possibility to form an external haematite layer and may alter the oxide scale growth rate. The extend by which the H2 affects the oxidation behaviour depends on the gas flow conditions, the water vapour content and the exposure time. To confirm these observations a number of specimens were oxidized in Ar-H2-H2O mixtures. This atmosphere guarantees a very low equilibrium oxygen partial pressure, in which H2 formed by reaction of the gas with the metal, does not substantially alter the thermodynamic properties of the gas.
Determinability of Complete Residual Strain Tensor from Multiple CBED Patterns
Authors: Morawiec Adam
Published: March 2009

The ambiguity in determination of complete elastic strain tensor by convergent
beam electron diffraction can be overcome by simultaneous use of multiple diffraction patterns.
Numerical tests of strain determining procedure based on multiple patterns have been carried
out. Patterns were simulated using both kinematic and dynamic approaches, and then they
were used as input in the tested procedure. The tests indicate that, in practice, at least three
patterns are needed in order to determine a complete strain tensor with reasonable accuracy.
The strain resolution of two parts per ten thousand was achieved with five diffraction patterns.
Moreover, the impact of errors in voltage and camera length is considered. It is shown that
within the kinematic description, the deviations from the correct voltage are equivalent to
errors in the isotropic part of strain.
Residual Stress State and Fatigue Behaviour of Laser Shock Peened Titanium Alloys
Authors: Altenberger I. , Sano Yuji , Cherif M.A. , Nikitin Ivan , Scholtes Berthold
Published: March 2009

Laser shock peening is a very effective mechanical surface treatment to enhance the
fatigue behaviour of highly stressed components. In this work the effect of different laser shock
peening conditions on the residual stress depth profile and fatigue behaviour without any sacrificial
coating layer is investigated for two high strength titanium alloys, Ti-6Al-4V and Timetal LCB.
The results show that the optimization of peening conditions is crucial to obtain excellent fatigue
properties. Especially, power density, spot size and coverage severely influence the residual stress
profile of laser shock peened Ti-6Al-4V and Timetal LCB specimens. For both alloys, subsurface
as well as surface compressive residual stress peaks can be obtained by varying the peening
conditions. In general, Timetal LCB exhibits steeper stress gradients than Ti-6Al-4V for identical
peening conditions. The main parameters affecting the fatigue life are near-surface cold work and
compressive residual stresses.
A Kinematic Hardening Finite Elements Model to Evaluate Residual Stresses in Shot-Peened Parts, Local Measurements by X-Ray Diffraction
Authors: Ould Choumad , Rouhaud Emmanuelle , François Manuel , Chaboche Jean Louis
Published: March 2009

Experimental analysis can be very costly and time consuming when searching for the
optimal process parameters of a new shot-peening configuration (new material, new geometry of the
part…).
The prediction of compressive residual stresses in shot-peened parts has been an active field of
research for the past fifteen years and several finite elements models have been proposed. These
models, although they give interesting qualitative results, over-estimate, most of the time, the level
of the maximal compressive stresses.
A better comprehension of the phenomena and of the influence of the parameters used in the model
can only carry a notable improvement to the prediction of the stresses. The fact that the loading path
is cyclic and is not radial led us to think that a model including kinematic hardening would be better
adapted for the modelling of shot peening.
In this article we present the results of a simulation of a double impact for several constitutive laws.
We study the effect of the chosen constitutive law on the level of residual stresses and, in particular,
we show that kinematic hardening, even identified on the same tensile curve than isotropic
hardening, leads to lower stress levels as compared with isotropic hardening. Furthermore, the
overall shape of the stress distribution within the depth is significantly different for the two types of
hardening behaviour.
Further, in order to check the modelisations, local measurements were carried on with X-ray
diffraction on a large size impact and correlated with the topography of the impact.
Experimental and FEM Analysis of Cutting Sequence on Residual Stresses in Machined Layers of AISI 316L Steel
Authors: Outeiro J.C. , Umbrello Domenico , M'Saoubi Rachid
Published: March 2009

The reliability of a mechanical component depends to a large extent on the physical state
of its surface layers. This state includes the distribution of residual stresses induced by machining.
Residual stresses in the machined surface and subsurface are affected by the cutting tool, work
material, contact conditions on the interfaces, cutting regime parameters (cutting speed, feed and
depth of cut), but also depends on the cutting procedure. In this paper, the effects of cutting
sequence on the residual stress distribution in the machined surface of AISI 316L steel are
experimentally and numerically investigated. In the former case, the X-ray diffraction technique is
applied, while in the latter an elastic-viscoplastic FEM formulation is implemented. The results
show that sequential cut tends to increase superficial residual stresses. A greater variation in residual
stresses is observed between the first and the second cut. Moreover, an increase in the thickness of
the tensile layer is also observed with the number of cuts, this difference also being greater between
the first and the second cut. Based on these results, the residual stress distribution on the affected
machined layers can be controlled by optimizing the cutting sequence.
Mechanical Stress Gradients in Thin Films Analyzed Employing X-Ray Diffraction Measurements at Constant Penetration/Information Depths
Authors: Wohlschlögel M. , Baumann W. , Welzel U. , Mittemeijer Eric Jan
Published: March 2009

Stress gradients have been investigated employing a measurement strategy for diffraction
measurements at constant penetration/information depths. Two examples have been considered: (i)
sputter-deposited copper thin films on silicon wafers and (ii) γ’-Fe4N1-x layers on α-Fe substrates
obtained by gaseous nitriding. In the Cu thin films rather low tensile stresses, increasing in
magnitude with increasing penetration/information depth have been found. An evaluation of the
measured lattice strains has been performed on the basis of the f(ψ) method, where the X-ray elastic
constants (XEC’s) have been calculated as weighed averages of the corresponding Voigt and Reuss
XEC’s and the weighing parameter has been taken as a fitting parameter. This evaluation reveals
that the grain interaction changes with increasing penetration/information depth from near-Reuss
type towards Neerfeld-Hill type. In the γ’-Fe4N1-x layers stress gradients occur due to surface
relaxation near the surface and deeper in the layer due to a nitrogen concentration gradient which is
built up during nitriding. First measurements in a laboratory diffractometer show the effect of
surface relaxation on the stress-depth profile near the surface. As no single-crystal elastic constants
are available for γ’-Fe4N1-x, the mechanical elastic constants have been employed in diffraction
stress analysis. The results indicated that single-crystal elastic anisotropy occurs. From the measured
data also a concentration – depth profile has been deduced.
Design of Engineering Diffractometer at J-PARC
Authors: Harjo Stefanus , Moriai Atsushi , Torii Shuki , Suzuki Hiroshi , Suzuya Kentaro , Morii Yukio , Arai Masatoshi , Tomota Yo , Akita Koichi , Akiniwa Yoshiaki
Published: March 2009

An engineering diffractometer designed to solve many problems in materials science and
engineering including investigations of stresses and crystallographic structures within engineering
components is now being developed at J-PARC project. This instrument views a decoupled-poisoned
liquid H2 moderator providing neutrons with good symmetrical diffraction profiles in the acceptable
wavelength range. The primary flight path and the secondary flight path are 40 m and 2.0 m,
respectively, for 90 degree scattering detector banks. A curved supermirror neutron guide will be
installed to avoid intensity loss due to the long flight path and to reduce backgrounds from fast
neutrons and gamma rays. Therefore, stress measurements with sufficient accuracies in many
engineering studies are quite promising. The optimization of this instrument has been performed with
a Monte Carlo simulation, and an appropriate resolution of less than 0.2 % in d/d has been
confirmed. A prototyped radial collimator to define a gauge width of 1 mm has been designed and
manufactured. From performance tests conducted at the neutron diffractometer for residual stress
analysis RESA in JRR-3 of Japan Atomic Energy Agency, the normal distribution with a full width at
half maximum of 1 mm was obtained in a good agreement with the simulation.
Residual Stress Reconstruction by Variational Eigenstrain Procedures
Authors: Korsunsky Alexander M. , Regino Gabriel M. , Nowell David
Published: March 2009

Residual stress can be found in engineering components as a result of non-uniform plastic
strain introduced through a variety of manufacturing processes such as rolling, casting, hot forging,
cold working, shot-peening, laser shock peening, welding, etc. The numerical simulation of the
resulting residual stress field requires the use of sophisticated coupled microstructural and thermomechanical
models that rely on profound understanding of the constitutive laws and detailed
knowledge of material parameters. In practice this level of understanding is not generally available,
leading to the use of simplified models that are unable to reproduce or predict reliably the real
residual stress distributions. This leads to the necessity of using increased safety factors and utilising
overly conservative designs. A rational approach to the description of residual stress states is
proposed that relies on the use of eigenstrain distributions as sources of residual stress. The problem
of residual stress evaluation can then be replaced by the problem of determining the underlying
eigenstrain distribution. An approach to this problem is proposed based on a simple variational
formulation. Some examples of its application are shown, and the difficulties and challenges that
may arise are discussed.
Application of the cos α Method to Area Detector Type Neutron Stress Measurement
Authors: Sasaki Toshihiko
Published: March 2009

In order to study the method of the neutron stress measurement using the
cosα method, a numerical simulation study was performed and the result was compared
with author's former experiment. The results of the simulation study agreed with those
obtained in the previous experiment, which suggests the validity of the present method
for neutron stress measurement.
Residual Stress Distribution in Pure Bending Beam Subjected to Tensile Failure on One Side
Authors: Wang X.B.
Published: March 2009

The stress distribution on the midsection of a pure bending beam where tensile strain
localization band initiates on the tensile side of the beam and propagates within the beam is analyzed.
Using the static equilibrium condition on the section of the midspan of the beam and the assumption
of plane section as well as the linear softening constitutive relation beyond the tensile strength, the
expressions for the length of tensile strain localization band and the distance from the tip of the band
to the neutral axis are derived. After superimposing a linear unloading stress distribution over the
initial stress distribution, the residual stress distribution on the midsection of the beam is investigated.
In the process of strain localization band’s propagation, strain-softening behavior of the band occurs
and neutral axis will shift. When the unloading moment is lower, the length of tensile strain
localization band remains a constant since the stress on the base side of the beam is tensile stress.
While, for larger unloading moment, with an increase of unloading moment, the length of tensile
strain localization band decreases and the distance from the initial neutral axis to the unloading
neutral axis increases. The neutral axis of midsection of the beam will shift in the unloading process.
The present analysis is applicable to some metal materials and many quasi-brittle geomaterials (rocks
and concrete, etc) in which tensile strength is lower than compressive strength. The present
investigation is limited to the case of no real crack. Moreover, the present investigation is limited to
the case that the length of strain localization band before unloading is less than half of depth of the
beam. Otherwise, the residual tensile stress above the elastic neutral axis will be greater than the
tensile strength, leading to the further development of tensile strain localization band in the unloading
process.
Residual Stress in Laser Bent Steel Components
Authors: Topic M. , Bucher R. , Vorster Willem J.J. , Zhang Shu Yan , McGrath P.J. , Korsunsky Alexander M.
Published: March 2009

The kinetics of plastic deformation and microstructural evolution, and the residual stress in
particular, were investigated on the steel plates (SABS 1431) bent by laser beam. The steel
plates were bent by different number of laser scans and therefore, each was bent to a different
extent. The stress results obtained by x-ray diffraction (sin2ψ-method) show a higher
compressive stress along the laser path than in the transverse direction. It was also found that
stress relaxation occurs during multi-scan laser forming process and most importantly, that the
stress is not significantly different in comparison to the stress, which initially existed in rolled
steel plates. The metallographic analyses show that phase transformation, dynamic recovery and
recrystallization processes occur during laser forming.
Residual Stress Prediction and Relaxation in Welded Tubular Joints under Constant Cyclic Loading
Authors: Barsoum Zuheir
Published: March 2009

In this paper three-dimensional welding simulations were carried out in FE
software ANSYS in order to predict transient temperatures and the residual stresses in a three
pass welded tubular joints. The thermal analysis and the moving heat source were verified
with temperature measurements and the computed residual stresses were verified with hole
drilling measurements. Then residual stress relaxation analyses were carried out on the tubular
structure, with similar load cases as in earlier fatigue testing on the same tubular joint
structures.
Numerical and Experimental Analysis of Residual Stress Induced by Elastic-Plastic Bending, Tension or Torsion Loading
Authors: Lahlal A. , Sprauel Jean Michel , Michaud H.
Published: March 2009

In this work a complete analytical model of elastic-plastic bending, tension and / or
torsion has been developed to simulate the manufacturing of leaf springs and coil suspensions. A
special procedure was also implemented to simulate mechanical surface treatments such as shot
peening. These models allow predicting the plastic strains and residual stresses induced by
successive loadings of the part. Our approach required first defining the mechanical behaviour of
the material. The constitutive laws of the employed steels were therefore identified starting from
cyclic loops recorded for tests carried out at various imposed strains. These laws were introduced
in the plasticity model to simulate the different steps of manufacturing: forming of the part,
presetting operations, shot peening, elastic-plastic shake down produced by the first cycles of
fatigue. In order to validate the model, residual stress maps were also characterized by X-Ray
diffraction. However, to retrieve the maximum of information from this kind of measurement, the
experimental data has been analysed through a global method which processes the whole acquired
diffraction peaks at once.
Analysis of the Impact of a Shot at Low Velocity Using the Finite Element Method. Application to the Ultrasonic Shot-Peening Process
Authors: Cochennec Florent , Rouhaud Emmanuelle , Retraint Delphine , Rouquette Sébastien , Roos Arjen
Published: March 2009

Shot-peening is a surface treatment widely used in the industry to improve fatigue life of
mechanical components by introducing compressive residual stresses. Ultrasonic shot-peening is a
recent development of this process. While the classical shot-peening process uses pneumatic energy
to project the shots, ultrasonic peening uses high-power ultrasounds. This energy source allows the
use of larger shots projected at lower velocity as compared to classical shot-peening. This work
aims at studying the mechanical response (restitution coefficient, residual stress field) of a surface
impacted by a shot at low velocity using the finite element method and experimental analysis. This
paper presents the simulation of a single elastic steel shot normally impacting an Aluminum alloy
plate considered to exhibit a linear-elastic behavior and non-linear isotropic work hardening
characteristics. The numerical simulations are carried out for different impact velocities in order to
take into account the heterogeneous shot velocity field observed in an ultrasonic shot-peening
chamber. We compare the simulated rebound energy and the indentation profiles obtained for
different impact velocities to experimental results. The simulated residual stress field topology
shows a strong dependence on the shot velocity. While numerical results obtained at high impact
energy agree well with literature results, the residual stress distribution simulated for low impact
energies shows a tensile layer below the impacted area. The restitution coefficients and the
indentation profiles compare well with the experiments.
Residual Stresses due to High Temperature Annealing. Mathematical Model and Calculations
Authors: Hachkevych O.R. , Mykhailyshyn V.S. , Ravska-Skotnichna A.
Published: March 2009

The mathematical model is developed for description of thermomechanical processes at
cooling during high temperature annealing with the known initial temperature distribution (the
temperature of holding) and stresses (acquired stresses at the final of a holding). It is taken into
account the thermal sensitivity and material hardening at elasto-plastic solid deforming. The
methodology based on the finite element method is proposed for solving thermomechanics
problems of wide range. The suitable software is developed. At the final stage of annealing a
cylindrical solid it is investigated residual stresses being formed on the cooling stage.