bluuebunny/crossref_metadata_2025 huggingface dataset:
Advanced Aluminium and Hybrid Aerostructures for Future Aircraft
Authors: Liu John
Published: March 2009

Alcoa has made a fundamental shift in its aerospace R&D program, broadening its scientific and engineering portfolio by creating an integrated, strategic, long-term initiative. The ultimate goal is to help re-define the future performance, cost and value of the metallic and hybrid aerostructures that the company feels will be required to meet the mission requirements of tomorrow’s aircraft. Having intensely studied various structural options, Alcoa believes Hybrid Structural Assembly optimized with a combination of Advanced Aluminum and Hybrid Components offer the best opportunities to maximize structural performance. Not only do the new alloys, notably 3rd Generation Al-Li alloys and high strength and high toughness 7xxx alloys provide structural performance enhancements, they also offer dramatic improvements in corrosion resistance. In this paper, several advanced alloys and structural concepts targeted for next generation wing and fuselage applications and large scale test article results supporting Alcoa’s optimism for Advanced Metallic and Hybrid Structures are reviewed.
New Light-Weight Aluminium Alloys with High Mg2Si-Content by Spray Forming
Authors: Stelling O. , Irretier A. , Kessler O. , Krug P. , Commandeur Bernd
Published: March 2009

Aluminum alloys with high Mg2Si-content (>10 %) offer the possibility of a significant decrease in density and an increase in stiffness at the same time. But these alloys can hardly be produced in casting processes, due to an oxidation and a generation of pores by hydrogen solubility of the melt. Furthermore, the usual solidification rate is not sufficient for a fine microstructure morphology. A fine distribution of Mg2Si is possible by spray forming, where a coarsening of the particles can be avoided due to a higher solidification rate. Different aluminum alloys with high Mg2Si-content (>10 %) have successfully been produced by spray forming, extrusion and age hardening. Mg-excess as well as Si-excess has been investigated. An additional alloying with copper leads to a further increase in strength by the precipitation sequence of Al2Cu. The new light-weight aluminum alloys have been investigated regarding age hardening, physical and mechanical properties. Densities of 2.5-2.6 g/cm3 and Young´s modulus of approx. 80,000 MPa have been found. Microstructures were dense, homogeneous and of fine morphology. The yield strength of these alloys reached values of approx. 400 MPa after artificial aging, whereby only a slight decrease for the hot yield strength was observed up to a temperature of 200 °C. Applications of the new light-weight aluminum alloys can be expected where a reduced density together with a high hot yield strength would lead to a more compact design in high temperature environments, e.g. in combustion engines.
Effect of Advanced Cooling Front (ACF) Phenomena on Film Boiling and Transition Boiling Regimes in the Secondary Cooling Zone during the Direct-Chill Casting of Aluminium Alloys
Authors: Caron Etienne J.F.R. , Wells Mary A.
Published: March 2009

Accurate knowledge of the boundary conditions is essential when modeling the Direct-Chill (DC)
casting process. Determining the surface heat flux in the secondary cooling zone, where the greater
part of the heat removal takes place, is therefore of critical importance. Boiling water heat transfer
phenomena are quantified with boiling curves which express the heat flux density as a function of
the surface temperature. Compilations of boiling curves for the DC casting of aluminum alloys
present a good agreement at low surface temperatures but a very poor agreement at higher surface
temperatures, in the transition boiling and film boiling modes. Secondary cooling was simulated by
spraying instrumented samples with jets of cooling water. Quenching tests were conducted first
with a stationary sample, and then with a sample moving at a constant “casting speed” in order to
better simulate the DC casting process. The ejection of the water film in quenching tests with a
stationary sample and the relative motion between the sample and the water jets both lead to an
Advanced Cooling Front (ACF) effect, in which cooling occurs through axial conduction within the
sample rather than through boiling water heat transfer at the surface. The heat flux density and
surface temperature were evaluated using the measured thermal history data in conjunction with a
two-dimensional inverse heat conduction (IHC) model. The IHC model developed at the University
of British Columbia was able to take into account the advanced cooling front effect. The effect of
various parameters (initial sample temperature, casting speed, water flow rate) on the rate of heat
removal in the film boiling and transition boiling regimes was investigated.
3D Microstructure Reconstruction of Aluminium Alloys Quenched during Solidification
Authors: Ruvalcaba D. , Eskin Dmitry G. , Katgerman Laurens
Published: March 2009

In the present research the possibility of studying the solidification of aluminum alloys
by using the quenching technique is analyzed. Since the quenching technique does not provide
reliable information (i.e. due to an overestimation of solid fraction) when measuring the solid
fraction over 2D images from samples quenched at high temperature, the overestimation problem is
investigated by analyzing 3D reconstructed microstructures from quenched samples. The 3D
reconstructed microstructure may provide better understanding about the cause of overestimation of
solid fraction when quenching at high temperatures. Consequently, the reconstruction of the
microstructure that has existed before quenching may be possible after identifying and removing
the solid phase that develops during quenching. In the present research, binary aluminum alloys are
solidified and quenched at different temperatures, and then 3D reconstructed images are analyzed.
The possibility of reconstructing the microstructure that develops during solidification before
quenching is discussed.
Effects of Solidification Range on the Structure of Aluminium Alloys Obtained under Conditions of Constant Melt Flow
Authors: Turchin A.N. , Eskin Dmitry G. , Katgerman Laurens
Published: March 2009

Effects of solidification range on macro- and microstructure of pure aluminium and binary Al–Cu alloys obtained under conditions of constant melt flow are studied experimentally. The solidification range of binary alloys was varied by changing the concentration of the alloying element. An electromagnetic pump with a specially designed melt-guiding system is used to organize controlled unidirectional melt flow along the solidification front. Temperature and melt flow velocity are controlled during the experiment. It is observed that the extent of solidification range changes the macro– and microstructure, affects width and deflection angle of columnar grains, and alters the dendrite arm spacing in the presence of melt flow. The melt flow itself is found to change the macro- and microstructure, e.g. the increase of melt flow velocity clearly decreases the dendrite arm spacing.
The Effect of Intermediate Storage Temperature and Time on the Age Hardening Response of Al-Mg-Si Alloys
Authors: Røyset Jostein , Stene Tore , Sæter Jan Anders , Reiso Oddvin
Published: March 2009

Specimens of three Al-Mg-Si alloys, 6060, 6005 and 6082, were solution heat treated, stored at different temperatures for different time, and artificially aged. Properties were measured before and after artificial ageing. The natural ageing response of the alloys is dependent on the storage temperature. Decreasing storage temperature leads to a delayed onset of natural ageing, but also to a higher strength after prolonged ageing, particularly for lean alloys such as 6060. The temperature and time of intermediate storage between solution heat treatment and artificial ageing has a significant effect on the strength of the artificially aged material. For the 6005 and 6082 alloys the processes that take place during natural ageing lead to a reduced strength after artificial ageing.
Vacancy-Solute Aggregates in Al-Zn-Mg-(Cu, Ag)
Authors: Ferragut Rafael , Dupasquier A. , Iglesias M.M. , Macchi C.E. , Somoza Alberto , Polmear Ian J.
Published: March 2009

Positron annihilation spectroscopy in two versions (lifetime and coincidence Doppler
broadening) has been applied to investigate solute/vacancy interactions when minor amounts
(<1wt.%) of Ag or Cu are added to the alloy Al-4Zn-3Mg (wt.%) during ageing at 150°C. The
results show early clustering of vacancies with Zn (and with Cu, if present). Ag displays a strong
interaction with vacancies in competition with Mg and forms clusters that may help further
aggregation of the other alloying elements during artificial ageing. High Mg concentration is
observed at the misfit interfaces of semi-coherent or incoherent precipitates.
The Influence of Alloy Composition on Phase Transformations and Recrystallization in Twin-Roll Cast Al-Mn-Fe Alloys
Authors: Slámová Margarita , Sláma P. , Cieslar Miroslav
Published: March 2009

Twin-roll casting (TRC) is an advantageous substitution for Direct-Chill (DC) casting in
the manufacturing of rolled aluminium products. The results of a study of the phase transformations
and their interaction with recrystallization occurring during the annealing of TRC Al-Mn based alloys
are reported. Four alloys with different contents of Mn, Si and Fe were investigated. Precipitation was
studied by resistometric measurements in the course of a heating at linear rate. The microstructural
processes responsible for the observed changes in resistivity were identified by TEM examinations of
quenched specimens. The changes in the microstructure and solute content during homogenisations at
450°C and 610°C were monitored by conductivity and hardness measurements and polarised light
microscopy. It was elucidated that the temperature and kinetics of phase transformations are
influenced not only by the content of Mn, but also by Si content. In alloys with low Si content, the
decomposition of solid solution and the transformation of primary phases occur in much larger
temperature range than in the alloys with high Si content. The precipitation of Mn and Si, concurrent
to recrystallization, was observed to retard the latter, especially in alloys with high Mn and Si content.
The Development of New Al-Mg-Si Alloys for Thixoforming
Authors: Eidhed W. , Limmaneevichitr Chaowalit , Tezuka Hiroyasu , Sato Tatsuo
Published: March 2009

Al-Mg-Si based alloys have been developed to produce an advanced feedstock material for thixoforming. Effects of excess Si, Mn addition and deformation on microstructure evolutions during reheating and partial remelting were studied. The homogenized microstructures of the Mnadded Al-Mg-Si alloys consist of the Al12Mn3Si2 intermetallic compound along grain boundaries of equiaxed grains with fine-spherical and needle-like morphologies. The deformation by cold-rolling has a strong effect on the semi-solid microstructures of the Mn-added Al-Mg-Si alloys compared with the balanced and excess Si alloys. The Mn-added Al-Mg-Si alloys exhibit good features to produce the feedstock material for thixoforming.
Quantitative Correlation between Strength, Ductility and Precipitate Microstructures with PFZ in Al-Zn-Mg(-Ag, Cu) Alloys
Authors: Ogura Tomo , Hirosawa Shoichi , Cerezo Alfred , Sato Tatsuo
Published: March 2009

The quantitative correlation between strength, ductility and precipitate microstructures in the vicinity of grain boundaries with precipitate free zones (PFZ) was evaluated for Al-Zn-Mg(-Ag, Cu) alloys using transmission electron microscopy (TEM), three-dimensional atom probe (3DAP) and tensile test. In the Al-Zn-Mg ternary and Cu-added alloys aged at 433K, larger widths of PFZ were observed by TEM and resulted in lower elongations to fracture, independent of the size of grain boundary precipitates. On the other hand, the elongation of the Ag-added alloy was higher, if compared at the same levels of proof stress, due to the much smaller width of PFZ. This strongly suggests that PFZ is harmful to fracture of the investigated alloys. From a 3DAP analysis, furthermore, it was revealed that Ag and Cu atoms are incorporated in the nanoclusters from the initial stage of aging. In this work, the elongation was well correlated to the width of PFZ, size of grain boundary precipitates and the level of proof stress, enabling to predict ductility of the alloys from known microstructural factors.
Intergranular Corrosion and Stress Corrosion Cracking of Sensitised AA5182
Authors: Davenport Alison J. , Yuan Yudie , Ambat Rajan , Connolly Brian J. , Strangwood Martin , Afseth Andreas , Scamans Geoff M.
Published: March 2009

AA5182 (Al-4.5 wt% Mg) can become susceptible to intergranular corrosion (IGC) with
time at moderately elevated service temperatures owing to precipitation of Mg-rich β-phase at grain
boundaries, which can lead to stress corrosion cracking (SCC). The IGC and SCC susceptibility of
AA5182 was found to depend strongly on sensitisation heat treatments. AFM and TEM studies
demonstrated that the degree of precipitation and thus susceptibility to attack for a boundary can be
related to its crystallographic misorientation. Low angle boundaries (<20°) are most resistant to
attack as they do not show β-phase precipitation. However, higher angle boundaries show highly
variable precipitation and corrosion susceptibility: critical factors are the grain boundary plane and
precipitate/matrix crystallographic relationship.
Current Understanding of Steam Oxidation - Power Plant and Laboratory Experience
Authors: Saunders Stuart R.J. , McCartney Neil L.
Published: March 2009

This review discusses key papers presented at an EPRI sponsored Workshop on “Scale Growth and Exfoliation in Steam Plant” that was held at the National Physical Laboratory (NPL) in September 2003 [1]. Additionally, some more recent developments on modelling both scale growth and exfoliation are described. Scale exfoliation in the steam circuit of power plant boilers leads to tube blockages and, further downstream in the power plant, to erosion of the steam turbine blading; and this can have serious consequences for plant performance. Factors controlling this behaviour are reviewed. These include the thermochemistry of oxide formation as a function of operating conditions, scale microstructure and scale growth rates. It is well known that the oxidation rate of steels in steam is about an order of magnitude greater than that in air or oxygen, but the mechanism responsible for this increased rate is still unclear. Various hypotheses, which consider transport of volatile species through cracks and pores, diffusion of OH - or protons and direct access of steam to the metal oxide interface, are proposed to account for the increased rates of reaction in steam compared with air. Modelling exfoliation of thick oxide scales is considered in a number of ways. The basis of the original model by Armitt et al [2] has been extended and further developed. A popular approach is to assume that an oxide layer develops through-thickness cracks when a critical tensile stress (the oxide strength) or strain (the oxide strain to failure) is encountered. Another approach applies fracture mechanics principles to defects that are assumed to exist in the oxide layer, although there is great uncertainty regarding the relevant defect size distributions that control behaviour. A third lower bound (and conservative) approach is to consider the energetics of steady state through-thickness cracking that involves the fracture energy for through-thickness cracking and avoids the difficult issue of needing to know the defect size that initiates through-thickness cracking. Additionally, the need to incorporate kinetics of scale growth into the developing exfoliation models is briefly discussed.
Effects of Hydrogen on the Corrosion Resistance of Metallic Materials and Semiconductors
Authors: Hultquist Gunnar , Anghel C. , Szakàlos P.
Published: March 2009

For long time it is known that protons in aqueous solutions have a detrimental effect on
metallic materials. Relatively recently, it has also been observed in aqueous solution that the pitting
corrosion resistance of Cr, stainless steel 304 and 310 decreases and the anodic dissolution rate
increases due to the presence of hydrogen in the metal. In gas phase a high oxidation rate has been
observed for hydrogen containing Cr and Fe. Hydrogen in the substrate can also enhance the oxidation
of Fe in SS 316 and As in GaAs. All these results suggest enhanced dissolution in aqueous solution and
enhanced oxide growth at the oxide/gas interface in gas phase oxidation due to hydrogen promoted
outward-transport of substrate components. A possible mechanism for such out-transport is an
increased metal ion diffusivity in the metal-oxide due to a high abundance of metal ion vacancies
generated by hydrogen. In contrast to all the above examples, also positive effects of hydrogen have
been identified under certain conditions. In an attempt to understand both the negative and the positive
effects the concept of a beneficial, balanced oxide growth is used. In this concept a certain amount of
hydrogen can be beneficial in the oxidation by improving the balance between oxygen-ion and metalion
transport, leading to more dense and protective oxides. Depending on the temperature, H2 in air is
considered as either a sink or a source for hydrogen in materials.
Steam Oxidation Testing of Coatings for Next Generation Steam Power Plant Components
Authors: Agüero Alina , Gutiérrez Marcos , Muelas Raúl
Published: March 2009

To achieve higher power generation efficiency in steam turbines, operating temperatures are expected to rise from 550°C to 650°C. The use of oxidation resistant coatings on currently available materials, with high creep strength but inferior steam oxidation resistance, is being explored in order to accomplish this goal in the context of the European project “Coatings for Supercritical Steam Cycles” (SUPERCOAT). Coating techniques have been chosen on the basis of being potentially appropriate for coating steam turbine components: the application of metallic and ceramic slurries, pack cementation and the deposition of alloyed and cermet materials by thermal spray. The coatings were characterised by metallography, SEM-EDS and XRD and steam oxidation and thermal cycling laboratory testing was carried out at 650º C. In this presentation, the testing results of selected coatings will be shown including those which exhibit the most promising behaviour. For instance, slurry aluminides have been exposed to steam at 650°C for more than 38,000 h (test ongoing) without evidence of substrate attack. Some HVOF coatings such as FeAl, NiCr and FeCr also have shown excellent behaviour. The results have provided information regarding the mechanism of protection and degradation of these coatings as well as insight into new coating development.
Oxidation Behavior of Ru-Containing Ni-Base Single-Crystal Superalloys
Authors: Kawagishi Kyoko , Sato Atsushi , Sato Akihiro , Kobayashi Toshiharu , Harada Hiroshi
Published: March 2009

The 4th and advanced generation Ni-base single crystal superalloys, which contain large amounts of refractory metals for strengthening and platinum group metals, e.g., Ru, for TCP-phase prevention, show excellent high-temperature strengths. However, these alloying elements seem to decrease high-temperature oxidation resistance. In this study, Ni-base superalloys with various amounts of Ta, Re and Ru were examined in isothermal and cyclic exposures at 1373K to investigate the effect on the oxide growth rate and resistance to scale spallation. Structures of the oxide for the alloys were analyzed by XRD, SEM and EDX, and the oxidation kinetics is discussed. Ru and Re were found to degrade the oxidation resistance by the vaporization of their oxide. Ta-rich oxide in the spinel layer affects to stabilize ruthenium and rhenium oxide in the scale and improve the oxidation resistance of Ru-containing Ni-base superalloys.
Novel Electrodeposited Ni-Based Nanocomposite Precursors for Nitriding and Low Temperature Chromizing
Authors: Peng X. , Zhao J. , Zhang Hong Yan , Wang Fu Hui
Published: March 2009

Two types of Ni-base nanocomposites were prepared by co-deposition of Ni with
nano-sized particles of Cr or CeO2, respectively. Both Ni-Cr and Ni-CeO2 nanocomposites were
mainly composed of nanocrystalline Ni matrix, in which certain content of nanoparticles of Cr or
CeO2 randomly dispersed. The Ni-Cr nanocomposite was used as a precursor for preparing a novel
hard Ni/CrN coating by plasma nitriding at 560oC. The Ni-CeO2 nanocomposite was used as a
precursor to develop a novel oxidation-resistant chromia-forming coating by low temperature
chromizing using a conventional pack-cementation method. The microhardness of the nitrided layer
on the Ni-Cr nanocomposite and the oxidation resistance of the chromizing coating on the Ni-CeO2
nanocomposite were both greatly increased, in comparison to the corresponding counterparts, which
were obtained by plasma nitriding on a conventional coarse-grained Ni-Cr alloy with similar Cr
content and by chromizing on a coarse-grained Ni metal, respectively. The relationships among the
microstructures of the nanocomposite precursors and the nitrided/or chromized coatings, and their
properties were investigated and discussed.
Effect of Zirconium on Cyclic-Oxidation of Ni-40Cr-3Re Alloys with α-Cr / β-NiAl Coatings
Authors: Shibata Yoshimitsu , Hayashi Shigenari , Narita Toshio
Published: March 2009

A coating with duplex structure of a outer β-NiAl and an inner α-Cr layer, was formed
on a Ni-40Cr-3Re (in at%) alloy with or without Zr addition, and the coated alloys were
oxidized under thermal cycling in air for up to 2300ks. The coated alloys containing Zr
showed a two-step parabolic oxidation, the kp1st in the early stage of oxidation was
2.6~5.4×10-11 kg2
m-4
s-1 for four alloys tested, and kp 2nd for the longer oxidation increased
with increasing Zr content from 2.6~5.4×10-11 for the alloy with 0.1at%Zr to 9.6×10-11 kg2

m-4
s-1 for the alloy with 1.0at%Zr. The rapid oxidation for the alloy with 1.0at%Zr is due to
the formation of ZrO2 as an internal oxide. The oxide scale in the 1st stage consisted of both
α- and θ- Al2O3 with whiskers, and with further oxidation the α-Al2O3 became the major
product in the 2nd stage. After the oxidation for 2300ks the as-prepared, outer β-NiAl was
changed into a mixture of β-NiAl and γ’-Ni3Al for the Ni-40Cr-3Re alloy containing Zr, while
in the coated Ni-40Cr-3Re alloy the outer layer became a mixture of γ’-Ni3Al and γ-Ni(Al,Cr).
It was concluded that the addition of Zr into the coated Ni-40Cr-3Re alloy helps maintain
high Al contents in the outer Ni-aluminide layer by forming a protective Al2O3 layer.
Mechanical Properties and Adherence of Oxide Scales
Authors: Schütze Michael , Malessa M. , Renusch Daniel , Tortorelli P.F. , Wright Ian G. , Dooley R.B.
Published: March 2009

In the high temperature oxidation of metallic alloys oxide scale strains and in particular critical scale strains play a key role with regard to scale adherence. Scale spallation/exfoliation is a vital issue for not only long term alloy performance but also steel sheet production. In many cases materials selection is based on thermodynamic considerations and short term laboratory data, not taking into account changes in the oxidation mechanisms resulting from stresses induced by thermal cycles, oxide growth, specimen or component geometry, or other operational factors. This paper presents a very concise summary of the present knowledge in the form of an approach to a comprehensive scale failure model which is based on a number of microscopic and macroscopic system parameters. This failure model is part of an on-going work which aims at a computer-assisted assessment of oxide scale mechanical reliability.
Effect of Scale Microstructure on Scale Adhesion of Low Carbon Sheet Steel
Authors: Kobayashi Akio , Seto Kazuhiro , Urabe Toshiaki , Yamada Katsumi , Sato Kaoru
Published: March 2009

For industrial purposes, the adhesion control of secondary scale on hot rolled steel sheet is important. A basic study was carried out to clarify the effect of scale microstructure on the scale adhesion of low carbon steel (0.03%C-0.2%Mn). When scale of FeO (about 8μm thickness) was generated at 800°C and transformed by continuous cooling from 250~600°C to 200°C, the scale transformed from 400°C showed good adhesion. The scale consisted of magnetite seam from the steel substrate, lamellar structure of magnetite and α-Fe, and magnetite layer from the scale surface. The orientation analysis by TEM showed the relationship {110}Fe // {100}Fe3O4, <110>Fe // <100>Fe3O4, and the lattice strain was calculated as 4%. On the other hand, FeO/Fe substrate showed the relationship {100}Fe // {110}FeO, <110>Fe // <110>FeO, and 25% lattice strain was calculated. It is considered that the adhesion of scale should be affected by the lattice strain, thus Fe3O4/Fe substrate showed better adhesion than FeO/Fe substrate. The temperature of FeO formation also affects the scale adhesion through the extent of Fe super saturation in FeO.
Effect of Cr Content and Water Vapor on Fracture Behavior of the Scales Formed on Fe and Fe-Cr Alloy
Authors: Yanagihara Katsuyuki , Renusch Daniel , Röhrig M. , Schütze Michael
Published: March 2009

Isothermal oxidation was carried out on Fe and Fe-(1.0 and 5.0mass%)Cr alloy at 800°C and
1000°C in dry (PH2O=1x10-4 atm) and wet (PH2O=0.035 atm) air. Fracture behavior of the scale was
investigated using acoustic emission (AE) analysis during cooling. The water vapor content of the
atmosphere has a major influence on the oxidation of the Fe-Cr alloys, whereas it has virtually no
effect on the oxidation of Fe. During cooling, significant AE activity starts at about 450°C on the
Fe and Fe-Cr alloys oxidized in wet air. This critical temperature is independent of sample
composition, oxidation temperature and scale thickness. In the case of the oxidation of the Fe-Cr
alloys in dry air, however, the critical temperature shifts to higher temperatures with increasing
scale thickness and Cr content. Fracture behavior of the scale should be related to scale structure
caused by sample composition and oxidation condition.
Microstructures of SiO2 Scales Formed on MoSi2
Authors: Kurokawa Kazuya , Goto Daichi , Kuchino Jyunichi , Yamauchi Akira , Shibayama Tamaki , Takahashi Heishichiro
Published: March 2009

The microstructures of oxide scales formed on MoSi2 at medium-high temperatures in air
were observed by TEM. Based on the observation, relationships between oxidation temperature and
formation of MoO3 and crystallization of amorphous SiO2 scales were investigated. At 1273 K and
1373 K, the oxide scales had a structure consisting of amorphous SiO2 with small amounts of fine
MoO3 particles. The oxide scales at 1573 K and 1773 K had a structure consisting of amorphous
and crystalline SiO2. Growth rate of the oxide scale formed at 1773 K appreciably increased due to
crystallization of amorphous SiO2. It was thought that the increase in the oxidation rate at 1773 K
was caused by a change in the diffusion mechanism from O2 diffusion to lattice diffusion of O2-
through SiO2. In addition, the diffusion coefficient of oxygen was estimated from the growth rate of
SiO2 scale.
Oxidation of a Low Carbon, Low Silicon Steel in Air at 600-920°C
Authors: Chen Rex Y. , Yuen W.Y.Daniel
Published: March 2009

The oxidation behaviour of a commercial low carbon, low silicon steel in
flowing air at 600-920°C was investigated. Parabolic oxidation kinetics was observed
at all temperatures. Three oxidation kinetics zones with different oxidation activation
energies were identified. The mechanisms responsible for the different oxidation
kinetics are discussed.
Review of Residual Stress Determination and Exploitation Techniques Using X-Ray Diffraction Method
Authors: Belassel M. , Pineault J. , Brauss M.E.
Published: March 2009

Although x-ray diffraction techniques have been applied to the measurement of residual
stress in the industry for decades, some of the related details are still unclear to many
production and mechanical testing engineers working in the field. This is because these
details, specifically those associated with the transition between diffraction and mechanics,
are not always emphasized in the literature. This paper will emphasize the appropriate
calculation methods and the steps necessary to perform high quality residual stress
measurements. Additionally, details are given regarding the difference between mechanical
and x-ray elastic constants, as well as the true meaning of stress and strain from both
diffraction and strain gage point of view. Cases where the material is subject to loading above
the yield limit are also included.
Residual Stress Stability in High Temperature Fatigued Mechanically Surface Treated Metallic Materials
Authors: Altenberger I. , Nikitin Ivan , Juijerm P. , Scholtes Berthold
Published: March 2009

Different classes of metallic materials (aluminum alloys, steels, titanium alloys) were
mechanically surface treated by deep rolling and laser shock peening and isothermally fatigued at
elevated temperature under stress control. The fatigue tests were interrupted after different numbers
of cycles for several stress amplitudes and residual stresses and FWHM-values were measured by
X-ray diffraction methods at the surface and as a function of depth. The results summarize the
response of the surface treatment induced residual stress profiles to thermomechanical loading
conditions in the High Cycle Fatigue (HCF)- as well as in the Low Cycle Fatigue (LCF) regime.
The effects of stress amplitude, plastic strain amplitude, temperature and frequency are addressed in
detail and discussed. The results indicate that residual stress relaxation during high temperature
fatigue can be predicted for sufficiently simplified loading conditions and that thermal and
mechanical effects can be separated from each other. A plastic strain based approach appears to be
most suitable to describe residual stress relaxation. Frequency effects were found to be not very
pronounced in the frequency range investigated.
Measurement of Residual Stresses in Thin Films by Two-Dimensional XRD
Authors: He Bob B.
Published: March 2009

This paper introduces the recent progress in two-dimensional X-ray diffraction as well as
its applications in residual stress analysis in thin films. The stress measurement with twodimensional
x-ray diffraction can be done with low incident angle and is not limited to the peaks
with high two-theta angles like the conventional method. When residual stresses of thin films are
measured, a low incident angle is preferred to maximize the diffraction signals from the thin films
surfaces instead of from the substrates and matrix materials. Since one stress measurement at one
fixed incident angle is possible, stress gradients in depth can be measured by series of incident
angles. Some experimental examples are given to show the stress measurement at low and fixed
incident angle.
Evaluation of Deformation Behavior in Cu Thin Film under Tensile and Fatigue Loading by X-Ray Method
Authors: Akiniwa Yoshiaki , Suzuki Tsuyoshi , Tanaka Keisuke
Published: March 2009

Two kinds of electrodeposited copper foils (thickness is 8 and 20 μm) were loaded
statically, and the deformation behavior was observed. In-situ X-ray stress measurement was carried
out under tensile loading. Fatigue tests were also conducted to observe the effect of the thickness on
the fatigue strength. Change in the line broadening with stress cycles was observed to evaluate the
fatigue damage. The tensile strength of 8 μm foil was higher than that of 20 μm foil. When the foils
were loaded within elastic region, the stress measured by the X-ray method agreed with applied stress.
When the plastic deformation occurred, difference between the measured stress and the applied stress
became large. The difference of 20 μm foil was larger than that of 8 μm foil. Fatigue strength of 8 μm
foil was also higher than that of 20 μm foil. The value of the full width at half maximum, FWHM,
increased rapidly at the first cycle, and then the value became nearly constant. Just before fracture, the
value increased again. The change in FWHM corresponded to the change in the accumulated ratchet
strain.
On the Development of Grain-Orientation-Dependent and Inter-Phase Stresses in a Super Duplex Stainless Steel under Uniaxial Loading
Authors: Peng Ru Lin , Wang Yan Dong , Chai Guo Cai , Jia Nan , Johansson Sten , Wang Gang
Published: March 2009

Microstresses due to intergranular and inter-phase interactions in an austenitic-ferritic
super duplex steel (SAF 2507) under uniaxial compressive deformation have been studied by in-situ
neutron diffraction experiments. Lattice strains of several hkl planes of austenite respective ferrite
were mapped as a function of sample direction at a number of load levels during loading into the
plastic regime and unloading. The analysis of the experimental results has shown that during
loading both grain-orientation-dependent and inter-phase stresses were generated under plastic
deformation that was inhomogeneous at the microstructural level. Residual stresses depending on
the grain-orientation and phase have been found after unloading. The results also indicate stronger
intergranular interactions among the studied hkl planes of austenite than those of ferrite.
Influence of the Machining Parameters on Workpiece Roundness Error during Turning Operations
Authors: Núñez López Pedro Jose , Simao Jorge , Rubio Alvir E.M. , Rincón J.L.
Published: March 2009

During turning operations, the workpiece clamping system and the selection of the
cutting conditions are of prime importance. They both have a significant influence on workpiece
roundness error ER, due to the dynamic behaviour of the chuck-axis-workpiece system. This
dynamic behaviour is conditioned by selected machining parameters (cutting speed v, depth-of-cut
d, feed rate f) and the design of the workpiece (length L and diameter φ). The main aim of the work
was to evaluate the influence of the aforementioned parameters (v, d, f, L/φ) on workpiece
roundness error ER during turning AISI-1045 steel material, for a range of machining conditions
(v=150, 200, 250 m/min, f=0.15, 0.20, 0.25 mm/rev, d=1, 2, 3 mm). Furthermore, the cutting force
signals were monitored throughout the tests in order to control the process and the correlation of the
three force components (depth Fd, tangential Ft, feed Ff) with workpiece roundness error ER was
analysed. Of all the various operating process parameters that were evaluated, the machined
workpiece length L and the depth-of-cut d were shown to have the most significant influence on ER
variation. The highest ER values were obtained when the highest depth-of-cut d, feed rate f, cutting
speed v and length L values were employed and combined. Little effect on the output measure ER
was observed when cutting speed v and feed rate f parameters were individually increased.
Moreover, an increase in the cutting force (Fd, Ft y Ff) values showed to produce a significant
increase in workpiece roundness error ER.
Modelling of Surface Roughness (Ra and Rq) in the EDM of Reaction-Bonded Silicon Carbide
Authors: Puertas Ignacio , Luis-Pérez C.J.
Published: March 2009

In this work, a surface roughness study on the die-sinking electrical discharge machining
(EDM) of siliconised silicon carbide (SiSiC) has been carried out. The selection of the abovementioned
conductive ceramic was made taking into account its wide range of applications in the
industrial field: high temperature gas turbines, bearings, seals and lining of industrial furnaces. This
study was made only for the finish stages, due to the enormous importance that a good surface
quality has over such important properties as, in the case of ceramic materials: corrosion, fatigue
and wear resistance. The present study has been carried out on the influence of five design factors:
intensity supplied by the generator of the EDM machine (I), pulse time (ti), duty cycle (η), opencircuit
voltage (U) and dielectric flushing pressure (P), which are the most relevant parameters to be
controlled by the EDM process machinists, over two roughness parameters such as Ra and Rq. The
study of the behaviour of the two previously mentioned parameters has been done by means of the
technique of design of experiments (DOE), which allows us to carry out the previous analysis
performing a relatively small number of experiments. In this case, a 25-1 fractional factorial design,
whose resolution is V, has been selected due to the number of factors considered in the study.
Surface Roughness Characterisation Using Cutting Force Analysis, Regression and Neural Network Prediction Models
Authors: Núñez López Pedro Jose , Simao Jorge , Reina José M. Arenas , de la Cruz C.
Published: March 2009

The paper evaluates the feasibility of monitoring cutting forces for in-process prediction
of the workpiece surface roughness, using regression based models (RG) and artificial neural
network (ANN) techniques. The three orthogonal cutting force components (Fx, Fy, Fz) and the
machined length L have been chosen as input variables. In the experimental test, AISI-1045 steel
material was turned using a TiN coated carbide tool and employing a range of machining conditions
(cutting speed: v=150, 200, 250 m/min; feed rate: f=0.15, 0.20, 0.25 mm/rev; depth-of-cut: d=1, 2, 3
mm). The results provided a wide range of measured cutting force and surface roughness values (Ra
and Rq), which were used for adjustment and validation of the prediction models. Two prediction
models were developed and subsequently the model accuracy was assessed by comparing the
surface roughness predicted by the models with that measured by a 2D profilometer. The results
highlighted the reasonably good fit given by both models, with the ANN based model providing best
accuracy for surface roughness prediction. The prediction of the output surface roughness in an
automated turning process was established and was found to be feasible by the monitoring of
cutting forces.
Comparative Study of the Machinability of a Sintered Steel and a Nodular Graphite Iron Using a Constant Axial Force Drilling Test
Authors: Costa Herrero Lluis , Sierra Alcolea Cayetano , Vivancos Calvet Joan
Published: March 2009

The objective of this study is to compare the machinability of a sintered steel sample with
that of a nodular graphite iron sample. We have developed a method that not only allows us to study
the machinability, but also enables us to determine the optimum cutting conditions to suit criteria
for maximum production or maximum quality. The method is based on a drilling test using constant
axial force at the tip of the drill.
Design of Optimum Planetary Electro Discharge Machining Strategies
Authors: Sánchez Jose Antonio , López de Lacalle Luis Norberto , Lamikiz Aitzol
Published: March 2009

The use of Electrical Discharge Machining (EDM) for the manufacturing of moulds and
dies is generally accomplished by using different cutting regimens, from roughing to finishing, until
the specified surface finish and dimensional tolerances are met. Multistage planetary EDM can be
used to simplify the production process. Benefits such as the reduction of machining time, the need
for less electrodes, electrode wear minimization and the improvement of the final surface finish of
the component can be obtained. Design of multistage planetary EDM strategies requires a sound
knowledge of the optimum radius for each orbit that assures surface roughness and dimensional
accuracy together with a minimum machining time. Therefore, it is necessary to know the “exact”
value of the gap at each stage. In this paper the influence of different process variables on the design
of multistage planetary EDM strategies is analyzed.
Experimental Methodology Destined to Establish the Frequency Response Function (FRF) between a Dynamic Force and the Signals Emitted by a Piezoelectric Dynamometer
Authors: Castro L. , Viéville P. , Lipiński Paul
Published: March 2009

This paper proposes an experimental method for obtaining the Frequency Response
Function (FRF) between a dynamic force and the signals emitted by a piezoelectric dynamometer.
This function is known as Transmissibility. In the FRF obtaining stage, different configurations of
mounting and excitation have been compared to improve the function quality. The method has been
developed with a three components dynamometer fixed on a milling machine. The FRF has two
principal applications: it is used to evaluate the measurement system accuracy and to correct the
measurements, if necessary. The method has been developed with the purpose of studying the
cutting forces in machining process. Furthermore, it has been identified the influence of the parts of
the measurement chain in the measuring system response.
Scanning Tunnenling Spectroscopy of Oxidized 6H-SiC Surfaces
Authors: Nie S. , Feenstra R.M.
Published: March 2009

Scanning tunneling microscopy and spectroscopy have been used to study the electronic
states of oxidized 6H-SiC interfaces. The SiC surfaces were oxidized by annealing in an ultra-high
vacuum chamber at 600−800°C under 1×10-7 Torr pressure of molecular oxygen. Tunneling spectra
revealed two dominant states at –1.8 and 1.5 eV relative to the Fermi level, which lie outside the
band gap region but are inhomogeneously broadened such that they extend into the gap, together
with additional features within the band gap.
High Temperature Reliability of SiC n-MOS Devices up to 630 °C
Authors: Ghosh Ruby N. , Loloee Reza , Isaacs-Smith Tamara , Williams John R.
Published: March 2009

SiC based field-effect devices are attractive for electronic and sensing applications above
250 °C. At these temperatures the reliability of the insulating dielectric in metal-oxidesemiconductor
(MOS) structures becomes an important parameter in terms of long-term device
performance. We report on the reliability of n-MOS SiC capacitors following thermal stress cycling
in the 330 to 630 °C range. As the primary mode of oxide breakdown under these conditions is
believed to be due to electron injection from the substrate, the gate leakage current was measured as
a function of temperature. The gate dielectric was grown using dry oxidation with a post oxidation
NO passivation anneal. For large area, 1 mm diameter, 6H-SiC capacitors we obtain current
densities as low as 5nA/cm2 at 630 °C. In addition, gate leakage measurements from arrays of 300 to
1000 2m diameter devices fabricated on different 1cm2 6H-SiC substrates are presented. These are
encouraging results for the long-term reliability of SiC field-effect sensors.
Low Temperature Deposition of HfO2 Gate Insulator on SiC by Metalorganic Chemical Vapor Deposition
Authors: Hino Shiro , Hatayama Tomohiro , Miura Naruhisa , Ozeki Tatsuo , Tokumitsu Eisuke
Published: March 2009

Low temperature deposition of HfO2 films on 4H-SiC(0001) substrates by pulse
introduced metalorganic chemical vapor deposition (MOCVD) using tetrakis-diethylamido-hafnium
[Hf[N(C2H5)2]4, (TDEAH)] and H2O has been investigated. HfO2 films with relatively low leakage
current density of 10-4 A/cm2 were obtained even at a deposition temperature as low as 190 °C. We
demonstrate that the HfO2/SiC interface, where the HfO2 was deposited at 190 °C, has lower interface
state density than a typical thermally-grown SiO2/SiC interface. It is also shown by X-ray
photoelectron spectroscopy (XPS) that the HfO2/SiC structure fabricated at 190 °C has lower SiOx
count than the HfO2/SiC structure fabricated at 400 °C.
Correlation between Leakage Current and Ion-Irradiation Induced Defects in 4H-SiC Schottky Diodes
Authors: Raineri Vito , Roccaforte Fabrizio , Libertino Sebania , Ruggiero Alfonso , Massimino V. , Calcagno Lucia
Published: March 2009

The defects formation in ion-irradiated 4H-SiC was investigated and correlated with the
electrical properties of Schottky diodes. The diodes were irradiated with 1 MeV Si+-ions, at fluences
ranging between 1×109cm-2 and 1.8×1013cm-2. After irradiation, the current-voltage characteristics
of the diodes showed an increase of the leakage current with increasing ion fluence. The reverse
I-V characteristics of the irradiated diodes monitored as a function of the temperature showed
an Arrhenius dependence of the leakage, with an activation energy of 0.64 eV. Deep level transient
spectroscopy (DLTS) allowed to demonstrate that the Z1/Z2 center of 4H-SiC is the dominant defect
in the increase of the leakage current in the irradiated material.
Design and Analysis of a Dual-Step Field-Plate Terminated 4H-SiC Schottky Diode Using SiO2/High-K Dielectric Stack
Authors: Kumta A. , Rusli E. , Tin Chin Che
Published: March 2009

Silicon carbide (SiC) field plate terminated Schottky diodes using silicon dioxide (Si02)
dielectric experience high electric field in the insulator and premature dielectric breakdown,
attributed to the lower dielectric constant of the oxide. This problem can be addressed by using
high-k dielectrics such as silicon nitride (Si3N4) that will reduce the field, increase the breakdown
voltage and consequently improve the lifetime of the devices. While the advantages of single step
field-plate terminated diodes are well-known, the breakdown voltage can be improved even further
using a dual-step field-plate termination. Our 2D-numerical simulations using MEDICI have shown
an improvement in breakdown voltages in excess of 25% compared to the traditional single-step
field-plate terminated diodes.
High Power High Efficiency Lateral Epitaxy MESFETs in Silicon Carbide
Authors: Konstantinov Andrey O. , Svedberg J.O. , Ray I.C. , Harris Chris I. , Hallin Christer , Larsson B.O.
Published: March 2009

High power high efficiency silicon carbide RF MESFETs are fabricated using a novel
structure utilizing lateral epitaxy. The MESFET employs buried p-type depletion stoppers grown by
lateral epitaxy with subsequent planarization. The depletion stopper is epitaxially overgrown by the
channel layer. The depletion stopper suppresses short channel effects and increases the operation
voltage and the RF signal gain at high voltage operation. High breakdown voltages of over 200
Volts are achieved for single-cell components, however large-area transistors are limited to around
150 Volts. Single-cell components measured on-wafer demonstrate an Ft of 10 GHz and high
unilateral gain. Packaged 6-mm RF transistors in amplifier circuits feature a saturated power of 20
W and a P1dB of 15W with a linear gain of over 16 dB at Vdd of 60 V for 2.25 GHz operation.
Maximum drain efficiency is 56% for class AB operation, 48% at 1 dB compression point and 72%
for class C at 2.25 GHz.
Development of 8 mΩ-cm2, 1.8 kV 4H-SiC DMOSFETs
Authors: Ryu Sei Hyung , Krishnaswami Sumi , Hull Brett A. , Heath Bradley , Das Mrinal K. , Richmond Jim , Agarwal Anant K. , Palmour John W. , Scofield James D.
Published: March 2009

8 mΩ-cm2, 1.8 kV power DMOSFETs in 4H-SiC are presented in this paper. A 0.5 μm
long MOS gate length was used to minimize the MOS channel resistance. The DMOSFETs were
able to block 1.8 kV with the gate shorted to the source. At room temperature, a specific onresistance
of 8 mΩ-cm2 was measured with a gate bias of 15 V. At 150 oC, the specific onresistance
increased to 9.6 mΩ-cm2. The increase in drift layer resistance due to a decrease in bulk
electron mobility was partly cancelled out by the negative shift in MOS threshold voltage at
elevated temperatures. The device demonstrated extremely fast, low loss switching characteristics.
A significant improvement in converter efficiency was observed when the 4H-SiC DMOSFET was
used instead of an 800 V silicon superjunction MOSFET in a simple boost converter configuration.
Realization of Large Area Vertical 3C-SiC MOSFET Devices
Authors: Schöner Adolf , Bakowski Mietek , Ericsson Per , Strömberg Helena , Nagasawa Hiroyuki , Abe Masayuki
Published: March 2009

Vertical DMOSFET devices with varying size from single cell to 3x3 mm2 large devices
have been realized. The investigated devices had hexagonal and square unit cell designs with 2 $m
and 4 $m channel length. The p-body was aluminum implanted and the source was nitrogen or
phosphorus implanted. Low temperature Ti/W contacts were evaluated.