bluuebunny/crossref_metadata_2025 huggingface dataset:
Industrial Application of Through-Process Modelling I: Microstructural Descriptors Required from the Casting Model for Downstream Process Stages
Authors: Quested Tom , Crumbach Mischa , Hamerton Richard
Published: March 2009

This paper contains a review of microstructural through-process modelling (TPM) and the particular role of ingot metallurgy from an industrial perspective, focusing on recent advances in solidification theory, solidification and homogenisation software, and software environments that allow models to interface. To illustrate how as-cast microstructure can impact on downstream processing steps, a sensitivity analysis has been performed on an AA1xxx alloy using an in-house homogenisation model. Thus, knowledge gaps in theory and model application are highlighted.
The Effect of Aging Processes on the Structure and Properties of Rapidly Solidified Al-Sc, Al-Zr and Al-Hf Alloys
Authors: Berezina A.L. , Segida O.O , Nosenko V.K. , Schmidt U. , Kotko A.V.
Published: March 2009

Structural states of Al-Sc, Al-Hf and Al-Zr alloys rapidly quenched from the liquid state
have been studied. Features of structures in dependence on the nature of alloying elements, on the
quenching temperature and the cooling rate by the crystallization of ribbons have been investigated.
Fractal structures are formed by the quenching from the certain temperature-concentration region.
The change of the morphology of structures has been researched during the aging process.
Effect of an Addition of Silver on the Age Hardening and the Formation of a Soft Surface Layer in an Al-12mass%Zn Alloy
Authors: Kanadani Teruto , Nakagawa Keiyu , Hosokawa Norio , Sakakibara Akira , Murakami Koji , Hino Makoto
Published: March 2009

The aging of Al-Zn alloys has been vastly studied for decades. In the previous paper, 0hta
et al. studied carefully the hardness of the alloy during aging and revealed the existence of softer
regions near the surface and the grain boundary than the interior of the specimen even after aging
for a long time. Electrical resistivity measurement and X-ray small angle scattering experiment
together with hardness test suggested that in these regions vacancy decay to the surface and grain
boundaries was severe, thus the growth of GP zones were suppressed and therefore age hardening
was retarded. Also, it is well-known that an addition of a small amount of Ag raised solvus
temperature of GP zones. In this paper, soft surface layer formed in an Al-12mass%Zn alloy is
studied by adding small amount of Ag by means of hardness test and resistometry. Addition of Ag
more than 0.1% decreases the thickness of soft surface layer as well as accelerates age hardening
rate and suppresses the formation of soft region near the grain boundaries. Higher quenching
temperature also reduces the thickness of soft surface layer. Together with the behavior of aging
curves of the specimen with various thicknesses, the origin of the soft surface layer is confirmed to
be the effective role of surface as sinks for vacancies.
Delineating the Role of Second Phase Particles in AA6111
Authors: Wang Xi , Poole Warren J. , Embury J. David , Lloyd David J.
Published: March 2009

The application of 6000 series alloys is widespread and of particular importance to the
automotive sector. Their functionality depends on the detailed behaviour of the strengthening phases.
In this study, transmission electron microscopy (TEM) supplemented with a variety of mechanical
tests were used to examine the precipitates and their role in aspects such as the Bauschinger effect,
damage and fracture events, and in recovery and recrystallization processes.
Improvement of Bake-Hardening Response of Al-Mg-Cu Alloys by Means of Nanocluster Assist Processing (NCAP) Technique
Authors: Hirosawa Shoichi , Omura Tomoya , Suzuki Yoshikazu , Sato Tatsuo
Published: March 2009

In this work, the bake-hardening (BH) response of an Al-3.0Mg-1.0Cu (in mass%) alloy
has been improved by the small addition of Ag as a good example of our proposed Nanocluster Assist
Processing (NCAP) technique. From the detailed observation through high resolution transmission
electron microscopy (HRTEM), it is found that the origin of the increased hardness in the Ag-added
alloy is attributed to the densely and uniformly formed Z phase at the expense of Guinier-Preston-
Bagaryatsky (GPB) zones and the S’ phase. It is new findings that the Z phase is formed even in the
ternary alloy although the chemical composition lies in the (α+S+T) phase field. Based on the threedimensional
atom probe (3DAP) results, furthermore, it is suggested that nanoclusters of Mg, Ag
and/or Cu provide effective nucleation sites for the Z phase, whereas nanoclusters of Mg and Cu do
less. Such unique characteristics of Ag are clearly seen in the newly constructed interaction energy
map (IE map).
First Principles Calculations for Alloy Design of Moderate Temperature Age-Hardenable Al Alloys
Authors: Zhu Ai Wu , Shiflet Gary J. , Starke E.A. Jr.
Published: March 2009

For aerospace structural applications of age-hardenable aluminum at temperatures above 100°C, a primary alloy-design criterion is creep resistance which depends on the strengthening effect and thermal stability of the second phases.. First principle calculations can be used to study fundamental properties of these phases and, therefore, help to identify the desired ones and their precipitate structures. In order to produce the desired phases, which are usually thermodynamically metastable, and to suppress the undesired phases, computational analysis (combining first principle calculations, cluster variation methods and CALPHAD) can assist in identifying beneficial trace additions and deleterious impurities that must be eliminated. This paper, using Al-Cu-Mg as an example, illustrates this approach, which if successful, should shorten the normal alloy development period.
Properties of Rolled and Extruded Semiproducts Made of New Al-Cu-Mg-Ag Heat-Resistant B-1213 Alloy
Authors: Fridlyander I.N. , Antipov V.V. , Fedorenko T.P. , Jakimova E.G.
Published: March 2009

Main properties and structure of 2 mm thick sheets and 20×100 mm extruded strips made under industrial conditions from Al-Cu-Mg heat-resistant B-1213 alloy with Ag, Cr, Mn and Zr additions were investigated. It was stated that wrought B-1213 alloy semiproducts are superior to analogous semis made of widely used commercial heat resistant AK4-1ch-type alloys (analogues - AU2GN, 2618 alloys) in strength properties and heat resistance characteristics (by 10-20 %) as well as in crack resistance and fatigue life (by 20-40 %). B-1213 alloy is intended for replacement of traditional heat-resistant alloys of system Al-Cu-Mg-Fe-Ni in advanced aircraft primary structure components subjected heating at elevated temperatures (up to 200-250 oC) and allows one to increase weight efficiency, service life and reliability.
Study of the Nanostructures Formed in 2024 Alloy during Thermomechanical Treatments
Authors: Tolley Alfredo , Ferragut Rafael , Somoza Alberto
Published: March 2009

A study on the microstructures developed during artificial aging of the 2024 alloy in nondeformed and 8% pre-deformed specimens is presented. The microstructural characterization was carried out using transmission electron microscopy (TEM), specifically, diffraction contrast and highresolution imaging. The S phase was found to precipitate heterogeneously on dislocations in both nondeformed and pre-deformed alloys. After the same artificial aging time, a larger density of S phase precipitates was obtained in the pre-deformed specimens. In non-deformed specimens, a high density of small nanometer-sized aggregates was found, that was absent in the pre-deformed specimens, that were identified as GP zones. To further analyze the small sized aggregates, artificially aged specimens with no previous deformation were also studied with Coincidence Doppler Broadening (CDB) of positron annihilation radiation. With this technique, information on the chemical environment around vacancy sites contained in the GP zones was obtained. Specifically, a composition close to (AlCu)2Mg was derived.
The Effect of Ag-Addition on Crystal Structure of β'-Phase in Al-Mg-Si Alloy
Authors: Nakamura Junya , Matsuda Kenji , Nakamura Yoshio , Sato Tatsuo , Ikeno Susumu
Published: March 2009

The purpose of this study is identity the crystal structure of metastable phase in Ag added
Al-Mg-Si alloy by comparing the β’-phases in Al-Mg-Si alloy without Ag, using images of high
resolution transmission electron microscope (HRTEM), selected area electron diffraction patterns
(SADPs) and an energy dispersive X-ray spectroscopy (EDS). The result of SADPs and HRTEM
images have been simulated and compared with images and SADPs obtained from actual
precipitates. SADPs and HRTEM images obtained from metastable phase in the Ag added Al-Mg-Si
alloy showed similar to those of β’-phase in Al-Mg-Si alloy without Ag and had different lattice
spacings because of the effect of Ag.
The Role of Alloying Elements on the Surface Treatment and Finishing of Aluminium
Authors: Thompson George E.
Published: March 2009

The influence of alloying elements, deliberate or otherwise, and material processing on
the performance of aluminium during surface treatment and finishing are considered. Thus, with a
significant focus on copper, but with consideration of other elemental additions, the behaviour of
aluminium during growth of oxide at ambient temperature, etching or pickling, conversion coating
and anodizing, essential processes for generation of fit-for-purpose products, is highlighted.
Further, such processes generate, modify or transform the initially present air-formed alumina film.
Consequently, with knowledge of the phenomena proceeding at the alloy/film and
film/environment interfaces and those within anodic or other films, the possibility of controlling
features of nanoscale dimensions for improved performance arises. For example, deliberate
selection of alloying elements enables control of nanotextures formed at treated surfaces, and
formation of compositionally and morphologically modified films as well as generation of
nanoparticles with various functional properties.
Fracture Mechanical Testing of Adhesion of Organic Coatings on Aluminium
Authors: Rodahl Silje , Nisancioglu Kemal , Knudsen Ole Øystein
Published: March 2009

Applicability of the wedge test and the accompanying fracture mechanical data analysis,
commonly used for testing of adhesively bonded joints, was inestigated in an attempt to
develop a quantitative laboratory test for evaluating paint adhesion on aluminium. The test
was further used, along with a relatively better accepted laboratory test for filiform corrosion
of painted aluminium to study the mutual effects of corrosion and adhesion of various pretreatments
and paint systems on extruded AA 6082 T6 aluminium alloy. Pretreatments used
were commercial processes for deoxidising, chromating, hot AC anodising and Ti/Zr
conversion coating. The paints were polyester TGIC and epoxy DICY, both pigmented
commercial products. In particular, the compatibility of pretreatment-paint combinations were
investigated The wedge test methodology and sample preparation developed proved to be a
satisfactory approach for quantitative evaluation of pretreatment-paint combinations for
aluminium. Ti/Zr treatment gave exceptionally good adhesion and corrosion results when
coated with polyester. Epoxy coated Ti/Zr bars failed completely. However, hot AC
anodising, although in general significantly more robust than Ti/Zr, was more compatible
with the polyester than polyester coating. With the advent of chromate-free pre-treatments,
the need to establish the compatibility of the modified aluminium surface and applied organic
coating was demonstrated.
Scanning Kelvin Probe Studies of Cosmetic (Filiform) Corrosion on AA6016
Authors: McMurray H.N. , Coleman A.J. , Williams G. , Afseth Andreas , Scamans Geoff M.
Published: March 2009

Scanning Kelvin Probe (SKP) potentiometry is used to systematically investigate the effect of surface abrasion and subsequent heat-treatment on the open-circuit potential in humid air of the AA6016 surface. SKP is also used to follow the kinetics of filiform corrosion and to determine characteristic potentials associated with the electrolyte-filled filiform head and dry filiform tail. It is shown that simply abrading with 180 grit SiC produces a surface potential up to 0.5V lower than the bulk. When the abraded sample is overcoated with a 30 micron layer of PVB (polyvinyl butyral) and exposed to HCl a fast, superficial filiform corrosion (FFC) is observed in which metal loss is limited to the thickness of the surface layer. Filiform head OCP values are similar to that of the surface layer, whereas filiform tail OCP values are similar to the bulk. A mechanism is proposed in which the ultra-fine grain structure of the surface layer produces an anodic activation and the potential difference between the surface layer and the bulk provides and increased thermodynamic driving force for corrosion. For post-abrasion heat treatment temperatures up to 350°C the fast filiform process is followed by a slower, deeper form of FFC.
Surface Treatment for Corrosion Resistant Aluminium Alloys by Removing Intermetallic Phases
Authors: Seri Osami
Published: March 2009

It is well known that the Al-Fe system intermetallic compound particles on the aluminum
and its alloys are detrimental to the corrosion for aluminum materials. Trial and error efforts reveal
that Al3Fe intermetallic compound particles exposed on aluminum are preferentially and selectively
removed by electrochemically treatment in cathodic current. These treatment combined by two steps:
the first step is selective dissolution of aluminum component in the Al3Fe intermetallic compound by
electrochemical reaction. The second step is intensive removal of the iron-enriched intermetallic
particles on which vigorous hydrogen bubbling has been took place. The electrochemical
measurement and surface observation show that the aluminum and its alloys with free intermetallic
compound particles treated by aboves have excellent corrosion resistance in a NaCl solution. It is
also found that the intermetallic compound-free surface is preferable for the pretreatment surface for
the surface finishing.
Surface Science Studies of the Effect of Mn2+ on Zinc Phosphating of 2024-T3 Al Alloy
Authors: Akhtar A.S. , Susac D. , Wong K.C. , Wong P.C. , Mitchell K.A.R.
Published: March 2009

The present work is part of a broader investigation of the effects of additives in zinc
phosphate (ZPO) coating solutions that are designed for specific applications to Al and its alloys.
ZPO conversion coatings improve the corrosion resistance of the Al substrate and increase the
adhesion of paint. Coatings formed on 2024-T3 aluminum alloy, after dipping in ZPO coating
baths containing Mn2+, have been studied by X-ray photoelectron spectroscopy (XPS), SEM, and
scanning Auger microscopy (SAM). Variations are observed in coating morphology and
composition as the amount of Mn2+ in the coating solution increases through the 0 to 2500 ppm
range. Adhesion tests give information on the relative strength of the coating-substrate interaction
at different microstructural areas.
A Comparison of Flow Stress and Microstructure Development of Al Alloys in Plane Strain Compression and Multiple Forging
Authors: Ringeval S. , Driver Julian H.
Published: March 2009

Multiple forging (MF) can be used to attain large plastic strains in bulk alloys by
successive forging along three orthogonal directions to retain the initial sample shape. An original
multiple forging technique enabling 3-D cross forging at constant temperature up to 500°C has been
applied to two Al alloys (Al-1%Mn and Al-3%Mg-Sc,Zr). Their rheology, texture and
microstructure evolution are compared with those obtained in plane strain compression (PSC). The
results are interpreted in terms of slip activity behaviour during both deformation modes. They can
also be correlated with the contributions of free dislocations and sub-boundaries.
Characterisation and Modelling of the Three Dimensional Propagation of Short Fatigue Cracks
Authors: Buffière Jean Yves , Ferrié Emilie , Ludwig Wolfgang , Gravouil Anthony
Published: March 2009

This paper reports recent results on the characterisation and modelling of the three
dimensional (3D) propagation of small fatigue cracks using high resolution synchrotron X ray
micro-tomography. Three dimensional images of the growth of small fatigue cracks initiated
in two Al alloys on natural or artificial defects are shown. Because of the small size of the
investigated samples (millimetric size), fatigue cracks grown in conventional Al alloys with
a grain size around 100 micrometers can be considered as microstructurally short cracks. A
strong interaction of these cracks with the grain boundaries in the bulk of the material is
shown, resulting in a tortuous crack path. In ultra fine grain alloys, the crack shapes tend
to be more regular and the observed cracks tend to grow like ”microstructurally long cracks”
despite having a small physical size. Finite Element meshes of the cracks can be generated from
the reconstructed tomographic 3D images. Local values of the stress intensity factor K along
the experimental crack fronts are computed using the Extended Finite Element method and
correlated with the crack growth rate.
Beneficial Effect of Impurity Sulfur on High-Temperature Steam Oxidation of High Chromium Ferritic Steels
Authors: Murata Yoshinori , Nakai Masaaki , Nagai K. , Morinaga Masahiko , Sasaki Y. , Hashizume Ryokichi
Published: March 2009

The effect of S in steels on high-temperature steam oxidation resistance was investigated with
respect to the content and the state in high Cr ferritic steels. The beneficial sulfur effect on
high-temperature steam oxidation resistance was verified in high Cr ferritic steels. It was
considered that Cr was enriched in the vicinity of the segregated S on the specimen surface
because of a strong affinity between Cr and S atoms, resulting in the easy formation of the
passive Cr2O3 oxide layer on the surface even after the steam oxidation test for a short time. It
was found that the precipitated S operated more effectively to the improvement of the steam
oxidation resistance compared to the solid-solution state of S in the steels. Furthermore, the
sulfur effect on the high temperature steam oxidation resistance was related strongly to the
amount of dissolution hydrogen in the high Cr ferritic steels.
Corrosion Rate and Oxide Scale Characteristics of Austenitic Alloys in Supercritical Water
Authors: Watanabe Yutaka , Daigo Yuzo
Published: March 2009

Corrosion properties were investigated on stainless steels and Ni base alloys in
supercritical water containing 0.01mol/kg-H2SO4 at 400°C/30MPa as a function of oxygen
concentration ranging from 3ppb to 800ppm. Alloys with high Fe content showed an interesting
contrast in corrosion property in sulfuric acid-containing supercritical water between at the high
oxygen condition (800ppm) and at the lower oxygen conditions (3ppb and 8ppm). At 8ppm of
oxygen concentration or lower, corrosion rate was a unique function of Cr content of the alloys
including both Ni base alloys and stainless steels. However, corrosion resistance of the iron-based
alloys (316 stainless steels) was remarkably improved when oxygen concentration was increased up
to 800ppm. Corrosion rate of alloy C-276, which contains 5.7% of iron, was also somewhat reduced
under the high oxygen condition, while corrosion rate of the other “iron-less” Ni base alloys was
accelerated as oxygen level was increased. Characteristics of oxide scales, in terms of chemical
composition and compound structure, have been examined in connection with the corrosion
properties of the alloys.
Interdiffusion between Ni Based Superalloy and Diffusion Barrier Coatings at 1423K
Authors: Matsumaru Hiroyuki , Hayashi Shigenari , Narita Toshio
Published: March 2009

A diffusion couple study was carried out with Ni-based superalloy / γ’-Ni3Al with or without a Re-based alloy layer. The Re-based alloy containing Re, W, Cr, and Ni was formed on a second generation, single crystal Ni-based superalloy by using electroplating processes to form films of 70at%Re-Ni and Ni-20at%W, followed by Cr-pack cementation at 1573K for 36ks. The superalloy with or without the Re-based alloy layer was bonded to a γ’−Ni3Al alloy in vacuum. Diffusion couples were annealed in an evacuated quartz ampoule at 1423 K for 90 and 360ks. After the 360ks diffusion treatment the Re-based alloy remained sound and suppressed inward Al diffusion from the γ’-Ni3Al, it was further found that outward diffusion of alloying elements from the alloy substrate to the γ’-Ni3Al was also significantly reduced by the Re-based alloy layer.
Oxidation Property of CoNiCrAlY Coatings Prepared by Various Thermal Spraying Techniques
Authors: Shibata Mitsuhiro , Kuroda Seiji , Watanabe Makoto , Sakamoto Yukihiro
Published: March 2009

To protect various gas turbine components against high temperature in the hot sections of power generation plants and aircraft engines, thermal barrier coatings (TBC’s) have been developed and widely used. Conventional TBC’s consist of a MCrAlY (M: Ni, Co, NiCo, etc,) bond coating for oxidation resistance and a ceramic top coating for thermal insulation. High quality coatings of MCrAlYs have been produced mostly by low pressure plasma spraying but other more economical processes are also used depending on the operating conditions of the component to be coated. In this study, CoNiCrAlY powders were deposited on Inconel 718 substrate with three types spraying system, i.e., low pressure plasma spraying, high velocity oxy-fuel spraying, and atmosphere plasma spraying. Specimens were isothermally tested for up to 100 h in air at 1373 K. Mass gain of the coatings was measured. Microstructure of the coating cross sections and the surface oxides were observed with SEM. To identify the crystal structure of the formed oxides, the specimens were analyzed by XRD from the surface.
The New Materials Science Diffractometer STRESS-SPEC at FRM-II
Authors: Hofmann Michael , Seidl Günther A. , Rebelo-Kornmeier Joana , Garbe Ulf , Schneider Rainer , Wimpory Robert C. , Wasmuth Uwe , Noster Ulf
Published: March 2009

In response to the development of new materials and the application of materials and
components in new technologies the direct measurement, calculation and evaluation of textures and
residual stresses has gained worldwide significance in recent years. Non-destructive analysis for
phase specific residual stresses and textures is only possible by means of diffraction methods. In
order to cater for the development of these analytical techniques the new Materials Science
Diffractometer STRESS-SPEC at FRM-II is designed to be equally applied to texture and residual
stress analyses by virtue of its flexible configuration. The system compromises a highly flexible
monochromator setup using three different monochromators: Ge (511), bent silicon (400) and
pyrolitic graphite (PG). This range of monochromators and the possibility to vary the take-off angles
from 2θM = 35º to 110º allows wavelength adjustment such that measurements can be performed
around a scattering angle of 2θS ~ 90º. This is important in order to optimise neutron flux and
resolution, especially for stress analysis on components, since the gauge volume element in that case
is cubic and large vertical divergences due to focusing monochromators do not affect the spatial
resolution.
The instrument is now available for routine operation and here we will present details of recent
experiments and instrument performance.
A Comparative Study of Microstructure and Residual Stresses of CMT-, MIG- and Laser-Hybrid Welds
Authors: Pinto Haroldo , Pyzalla Anke , Hackl Heinz , Bruckner Jürgen
Published: March 2009

Recently a new welding technique, the so-called ‘Cold Metal Transfer’ (CMT) technique
was introduced, which due to integrated wire feeding leads to lower heat input and higher
productivity compared to other gas metal arc (GMA) technique. Here microstructure formation and
residual stress state in aluminum CMT welds are characterized and compared to those produced by
pulsed MIG- and Laser-hybrid techniques. The results show a small heat affected zone (HAZ) in the
MIG weld, the HAZ in the CMT and the laser hybrid welds was not visible by optical and scanning
electron microscopy. Compared to the MIG welding the CMT process appears to introduce slightly
smaller maximum tensile residual stresses into the weld.
High Productivity Machining Centre Evaluation in Collaborative Engineering Environment
Authors: Siller Hector , Vila C. , Rodríguez Ciro
Published: March 2009

This study shows a methodology for characterizing high speed machining centres, in
terms of their capabilities, to reach programmed feed rates while the machining of complex
sculptured surfaces. The impact on the cycle time of the whole operation has been evaluated making
a parametric variation of the geometries to be machined. Therefore, for a distributed and
simultaneous characterization of machining centres located in different places, tools for
Collaborative Engineering have been used (PLM and CAD/CAM/CAE).
Multi-Parameter Modeling of Surface Texture in EDMachining Using the Design of Experiments Methodology
Authors: Petropoulos G. , Vaxevanidis N. , Iakovou A. , David Kostas
Published: March 2009

This study concerns the formulation of a multi-parameter surface texture model in
EDMachining of AISI D2 tool steel. The model is developed in terms of pulse current and pulse-on
time which are the dominant machining conditions, via factorial design of experiments. By applying
analysis of variance and statistical multi-regression analysis to the experimental data close
correlation is proved between certain surface finish parameters and the machining conditions, with
pulse current exerting the strongest influence. By applying this model the appropriate conditions for
successful finish can be selected, as well as functional surface characteristics can be quantified.
Study with Stainless Steel AISI 630 of Tool Wear in External Turning Operations
Authors: Ortiz Marzo Jose Antonio , Rio Carlos , Salueña Berna Xavier , Casals Terré Jasmina , Capilla Ana I.
Published: March 2009

This study starts from a firm’s needs to improve manufacturing costs and times in an
external turning operation with the material according to the standard AISI 630 (martensitic
stainless steel, hardened by precipitation), with a hardness of 355 HB. It has been developed a basic
factorial design of experiments with two factors (cutting speed and feed per revolution), with
constant depth of cut and two levels, with three central points. This experiment has resulted in the
obtaining of the machined meters from a tool life criterion, which has limited basically the tool
flank wear, VB = 0,2 mm. The balance between the tool wear, maximum machining length and the
minimum machining time has been considered from the analysis of the results.
The Mathematical Modeling of the Compressive Stresses on the Cutting Tool in Machining of Inconel 718
Authors: Şeker Ulvi , Kurt Adem
Published: March 2009

In this paper, a mathematical model has been developed for the cutting tool stresses in machining of nickel-based super alloy Inconel 718 used in aircraft and spacecraft industries, nuclear power systems and steam generators etc. necessitating oxidation and corrosion resistance, high temperature and strength. The cutting forces were measured by a series of experimental measurements and stress distributions on the cutting tool were analyzed by means of the finite element method using Ansys software. The mathematical modeling process of the compressive stresses in x, y and z directions was carried out with multiple regression analysis regarding to Ansys stress results depending on the cutting forces and the chip–tool contact area. It is found that model results had good agreement with the Ansys stress results.
Analysis of the Behaviour Effect of Face Cutting Edge Inserts on Surface Roughness when Milling Steels with MQL Lubrication
Authors: Salueña Berna Xavier , Ortiz Marzo Jose Antonio , Casals Terré Jasmina
Published: March 2009

The main objectives of this work are the study of the obtained surface roughness on
steels, using face cutting edge inserts milling tools in finishing face milling operations with
microlubrication (MQL), and comparison of the results obtained with the widely-used radius
inserts. This experimental study analyzes the roughness and surface appearance obtained with both
sort of inserts. The interest about this study is to determine the steel types and the optimal cutting
conditions for milling with this face cutting edge inserts. Another result analysed is the utility of the
MQL implementation compared to the dry system.
Real Time Observation of SiC Oxidation Using an In Situ Ellipsometer
Authors: Kakubari K. , Kuboki R. , Hijikata Yasuto , Yaguchi Hiroyuki , Yoshida Sadafumi
Published: March 2009

Real time observation of SiC oxidation was performed using an in-situ ellipsometer over
the temperature range from 900°C to 1150°C. The relations between oxide thickness and oxidation
time were obtained precisely by virtue of the real time measurements. We analyzed the relations
between oxide thickness and oxidation time by applying the Deal and Grove model to obtain the
linear and parabolic rate constants. Taking advantage of in-situ measurements, we successfully obtained
the oxidation rate constants with high accuracy.
Fast Non-Contact Dielectric Characterization for SiC MOS Processing
Authors: Hoff A.M. , Oborina E.
Published: March 2009

Non-contact corona-voltage metrology is utilized to characterize as-grown thermal oxide
films on 4H SiC substrates. Contact potential difference mapping is coupled with incremental
application of corona charge to provide whole-wafer images of process related effects and multiplepoint
capacitance-voltage characteristics respectively. Correspondence between wafer VCPD images
and process details is suggested along with examples of fast electrical dielectric thickness
determination and non-contact C-V characteristic acquisition.
PECVD Deposited TEOS for Field-Effect Mobility Improvement in 4H-SiC MOSFETs on the (0001) and (11-20) Faces
Authors: Pérez-Tomás Amador , Godignon Philippe , Camassel Jean , Mestres Narcis , Soulière Véronique
Published: March 2009

4H-SiC MOSFET devices with low temperature dry thermal oxidation (1050 °C 1 h) and
TEOS plasma enhanced CVD deposited oxides on 4H-SiC substrates have been analysed in this
paper. MOSFET transistors have been fabricated on the 4H-SiC (0001) Si face. The mobility
improvement (up to 38-45 cm2/Vs) is remarkable compared with standard oxidation (<10 cm2/Vs).
In addition, very high (but controversial) field-effect mobilities of around 216 cm2/Vs have also
been extracted for MOSFETs fabricated on the (11-20) face. Taking into account the threshold
voltage and the sub-threshold slope (S), we can see that we have three different ways to increase the
mobility. First, by using (11-20) face material as already proposed. Second, by reducing the
interface trap density as done with the low temperature thermal oxidation plus deposited oxide. And
third, under the most favorable conditions with adequate TEOS deposition conditions. In this last
case, the mobility improvement seems to be related with the gate current leakage more than (or
together with) an interface traps reduction of the gate insulator.
Gamma Irradiation Effects on 4H-SiC MOS Capacitors and MOSFETs
Authors: Ahyi Ayayi Claude , Wang S.R. , Williams John R.
Published: March 2009

The effects of gamma radiation on field effect mobility and threshold voltage have been
studied for lateral n-channel 4H-SiC MOSFETs passivated with nitric oxide. MOS capacitors (n
and p) and n-channel lateral MOSFETs were irradiated unbiased (floating contacts) for a total
gamma dose of 6.8Mrad (Si). The MOS capacitors were used to study the radiation-induced
interface traps and fixed oxide charge that affect the performance of the MOSFETs. Radiationinduced
interface traps were observed near the SiC valence band edge and just above mid-gap, and
field effect channel mobility was reduced by 18-20% following irradiation. Even so, 4HMOSFETs
appear to be more radiation tolerant than Si devices.
SiC HTCVD Simulation Modified by Sublimation Etching
Authors: Kito Yasuo , Makino Emi , Ikeda Kei , Nagakubo Masao , Onda Shoichi
Published: March 2009

High temperature chemical vapor deposition (HTCVD) simulations of silicon carbide
(SiC) were demonstrated with experimental results. A vertical cylindrical reactor was used in an RF
inductive heating furnace and the temperature was more than 2200. SiH4 and C3H8 were used as
source gases and H2 as carrier gas. A gas phase reaction model from the literature was used on the
condition that the gas phase reaction is a quasi-equilibrium state. It was found that the major species
were Si, Si2C, SiC2 and C2H2 in the gas phase reaction model as well as in the thermodynamic
equilibrium calculation. Sublimation etching was considered in the surface reaction rates by
modifying partial pressures of species with equilibrium vapor pressures. CFD-ACE+ and MALT2
software packages were used in the present calculation. The sticking coefficients were determined
by fitting the calculated growth rates to the experimental ones. The simulated growth rate in a
different reactor is in good agreement with the experimental value, using the same sticking
coefficients. The present simulation could be useful to design a new reactor and to find optimum
conditions.
Deep Reactive Ion Etching (DRIE) of High Aspect Ratio SiC Microstructures Using a Time-Multiplexed Etch-Passivate Process
Authors: Evans Laura J. , Beheim Glenn M.
Published: March 2009

High aspect ratio silicon carbide (SiC) microstructures are needed for microengines and
other harsh environment micro-electro-mechanical systems (MEMS). Previously, deep reactive ion
etching (DRIE) of low aspect ratio (AR ≤1) deep (>100 *m) trenches in SiC has been reported.
However, existing DRIE processes for SiC are not well-suited for definition of high aspect ratio
features because such simple etch-only processes provide insufficient control over sidewall
roughness and slope. Therefore, we have investigated the use of a time-multiplexed etch-passivate
(TMEP) process, which alternates etching with polymer passivation of the etch sidewalls. An
optimized TMEP process was used to etch high aspect ratio (AR up to 13) deep (>100 *m) trenches
in 6H-SiC. Power MEMS structures (micro turbine blades) in 6H-SiC were also fabricated.
Energy Efficiency: The Commercial Pull for SiC Devices
Authors: Palmour John W.
Published: March 2009

As SiC devices begin to become commercially available, it is becoming clear that
electrical efficiency improvement is one of the key drivers for their adoption. For RF applications,
SiC MESFETs have the ability to be easily linearized via digital pre-distortion to offer a 47%
improvement in efficiency. In broadband WiMax applications, SiC MESFETs offer more than
double the efficiency versus using GaAs MESFETs. SiC Schottky diodes are allowing up to a 25%
reduction in losses in power supplies for computers and servers when used in the power factor
correction circuit. For motor control, SiC Schottkys allow up to a 33% reduction in losses, as
demonstrated for a 3 HP motor drive. Even higher efficiencies can be obtained when the Schottkys
are combined with a SiC switch. A 400 W boost converter has been demonstrated using a SiC
MOSFET and Schottky diode, operating at >200° C, with an extremely high efficiency of 98%.
These improvements in electrical efficiency can have a significant impact in reducing overall
electricity consumption worldwide, impacting virtually every aspect of electrical usage, ranging
from information technology to motor control, with potential savings of $35 billion/yr.
Almost Ideal Thermionic-Emission Properties of Ti-Based 4H-SiC Schottky Barrier Diodes
Authors: Stephani Dietrich , Schörner Reinhold , Peters Dethard , Friedrichs Peter
Published: March 2009

We have carefully investigated a number of more than 120 selected chips fabricated on
one wafer, by I-V measurements at two different precisely controlled temperatures and precision CV
measurements at room temperature. From these measurements the net-doping concentration, the
C-V (flat-band) barrier ΦCV, the ideality n, the apparent Richardson constant Aapp and the apparent
I-V barrier Φapp have been extracted for each chip. An extremely unique C-V barrier was
determined showing a relative standard deviation (sigma over mean) of only 0.086%. Moreover, the
average ideality n was found to be as low as 1.028 exhibiting a relative standard deviation of only
0.35%. A clear linear correlation (ρ2 = 0.968) between ideality n and apparent I-V barrier was
observed. The effective Richardson constant A** of 4H-SiC in 〈0001〉 directions could therefore be
extracted to be most likely in the interval 70 Acm-2K-2 < A** < 80 Acm-2K-2.
A Surge Current Stable and Avalanche Rugged SiC Merged pn Schottky Diode Blocking 600V Especially Suited for PFC Applications
Authors: Treu Michael , Rupp Roland , Tai Chee Siew , Blaschitz Peter , Hilsenbeck Jochen , Brunner Helmut , Peters Dethard , Elpelt Rudolf , Reimann T.
Published: March 2009

Today silicon carbide (SiC) Schottky diodes are mainly used in the power factor control
(PFC) unit of high end switched mode power supplies, due to their outstanding switching
performance compared to Si pn diodes. In the case of the PFC it is required that the diodes are
capable of handling surge currents up to several times the current of normal operation. The paper
shows the surge current capability of a merged pn Schottky diode where the p-areas are optimized
as efficient emitters. During normal operation the diode is behaving like a normal Schottky diode
whereas during surge current condition the diode is behaving like a pn diode. For a sine half wave
of 10 ms we achieved a non repetitive peak forward current capability of about 3700 A/cm2 which is
about ten times rated current (for comparison: destructive current density of a standard Schottky
diode ~ 1650 A/cm²). Additionally the device shows a stable avalanche and is able to withstand a
single shot avalanche of 9.5 3s and 12.5 mJ.
Fabrication of 4H-SiC Floating Junction Schottky Barrier Diodes (Super-SBDs) and their Electrical Properties
Authors: Ota Chiharu , Nishio Johji , Hatakeyama Tetsuo , Shinohe Takashi , Kojima Kazutoshi , Nishizawa Shin Ichi , Ohashi Hiromichi
Published: March 2009

4H-SiC floating junction Schottky barrier diodes (Super-SBDs) were fabricated. It was
found that their properties are closest to the theoretical limitation, defined by the relationship between
specific on-state resistance and breakdown voltage of 4H SiC-unipolar devices. They have a p-type
floating layer designed as line-and-spacing. The specific on-state resistances of Super-SBDs with a
few micrometers of spacing width were found to be nearly equal to those of conventional SBDs
without p-type floating layer. The breakdown voltages of Super-SBDs were higher than those of
conventional SBDs. Accordingly the properties of Super-SBDs have improved the trade-off between
specific on-state resistance and breakdown voltage, and the highest value to date for Baliga’s Figure
of Merit (BFOM) has been obtained.
Fast Switching (41 MHz), 2.5 mΩ•cm2, High Current 4H-SiC VJFETs for High Power and High Temperature Applications
Authors: Cheng Lin , Casady Janna R. B. , Mazzola Michael S. , Bondarenko V. , Kelley Robin L. , Sankin Igor , Merrett J. Neil , Casady Jeff B.
Published: March 2009

In this work we have demonstrated the operation of 600-V class 4H-SiC vertical-channel
junction field-effect transistors (VJFETs) with 6.6-ns rise time, 7.6-ns fall time, 4.8-ns turn-on and
5.4-ns turn-off delay time at 2.5 A drain current (IDS), which corresponds to a maximum switching
frequency of 41 MHz – the fastest ever reported switching of SiC JFETs to our knowledge. At IDS
of 12 A, a 19.1 MHz maximum switching frequency has been also achieved. Specific on-resistance
(Rsp-on) in the linear region is 2.5 m·cm2 at VGS of 3 V. The drain current density is greater than
1410 A/cm2 at 9 V drain voltage. High-temperature operation of the 4H-SiC VJFETs has also been
investigated at temperatures from 25 °C to 225 °C. Changes in the on-resistance with temperature
are in the range of 0.90~1.33%/°C at zero gate bias and IDS of 50 mA. The threshold voltage
becomes more negative with a negative shift of 0.096~0.105%/°C with increasing temperature.
Analytical Modelling of I-V Characteristics for 4H-SiC Enhancement Mode VJFET
Authors: Bhatnagar Praneet , Horsfall Alton B. , Wright Nicolas G. , Johnson C. Mark , Vassilevski Konstantin , O'Neill Anthony G.
Published: March 2009

Physics-based analytical models are seen as an efficient way of predicting the
characteristics of power devices since they can achieve high computational efficiency and may be
easily calibrated using parameters obtained from experimental data. This paper presents an
analytical model for a 4H-SiC Enhancement Mode Vertical JFET (VJFET), based on the physics of
this device. The on-state and blocking behaviour of VJFETs with finger widths ranging from 1.6+m
to 2.2+m are studied and compared with the results of finite element simulations. It is shown that
the analytical model is capable of accurately predicting both the on-state and blocking
characteristics from a single set of parameters, underlining its utility as a device design and circuit
analysis tool.
Design Considerations of a New 4H-SiC Enhancement-Mode Lateral Channel Vertical JFET for Low-Loss Switching Operation
Authors: Choi Y.C. , Cha Ho Young , Eastman Lester F. , Spencer Michael G.
Published: March 2009

A new silicon carbide (SiC) enhancement-mode lateral channel vertical junction fieldeffect
transistor (LC-VJFET), namely “source inserted double-gate structure (SID-gate) with a
supplementary highly doped region (SHDR)”, was proposed for achieving extremely low power
losses in high power switching applications. The proposed architecture was based on the
combination of an additional source electrode inserted between two adjacent surface gate electrodes
and a unique SHDR in the vertical channel region. Two-dimensional numerical simulations for the
static and resistive switching characteristics were performed to analyze and optimize the SiC LCVJFET
structures for this purpose. Based on the simulation results, the excellent performance of the
proposed structure was compared with optimized conventional structures with regard to total power
losses. Finally, the proposed structure showed about a 20 % reduction in on-state loss (Pon)
compared to the conventional structures, due to the effective suppression of the JFET effect.
Furthermore, the switching loss (Psw) of the proposed structure was found to be much lower than the
results of the conventional structures, about a 75 % ~ 95 % reduction, by significantly reducing both
input capacitance (Ciss) and reverse transfer capacitance (Crss) of the device.
SiC Smart Power JFET Technology for High-Temperature Applications
Authors: Sankin Igor , Bondarenko V. , Kelley Robin L. , Casady Jeff B.
Published: March 2009

Wide bandgap semiconductor materials such as SiC or GaN are very attractive for use in
high-power, high-temperature, and/or radiation resistant electronics. Monolithic or hybrid
integration of a power transistor and control circuitry in a single or multi-chip wide bandgap power
semiconductor module is highly desirable for such applications in order to improve the efficiency
and reliability. This paper describes a new monolithic SiC JFET IC technology for high-temperature
smart power applications that allows for on-chip integration of control circuitry and normally-off
power switch. In order to demonstrate the feasibility of this technology, hybrid logic gates with
maximum switching frequency > 20 MHz and normally-off 900 V power switch have been
fabricated on alumina substrates using discrete enhanced and depletion mode vertical trench JFETs.
Current Sensing for SiC Power Devices
Authors: Tournier Dominique , Vellvehi Miquel , Godignon Philippe , Montserrat Josep , Planson Dominique , Sarrus F.
Published: March 2009

High voltage, high current capabilities of SiC based devices has been already
proved, and high current SiC devices working at high temperature are likely to be on the
market soon. SiC power integration will have to be considered as a further development step
to discrete power devices. Packaging and device integrated protections remain the main
constraints for high temperature operation and system integration. In case of short-circuit or
over-current, SiC devices can reach high temperature values, and the die might be subjected
to high stresses. In order to address such critical requirements, current sensing and real time
temperature monitoring are mandatory. The structure proposed in this paper, derived from Si
technology, provides a protection feature to SiC power devices to get reliable high
temperature electronics. Concretely, an integrated current sensor has been implemented in a
vertical power SiC JFET and its fabrication is reported for the first time. The current sensor
layout and process technology are presented. An experimental current sensing validation is
also reported.
RF and DC Characterization of Self-Aligned L-Band 4H-SiC Static Induction Transistors
Authors: Merrett J. Neil , Sankin Igor , Bondarenko V. , Smith C.E. , Kajfez D. , Casady Janna R. B.
Published: March 2009

Trenched, vertical SiC static induction transistors (SIT) for L-band power amplification
were fabricated with implanted p-n junction gates on conducting n-type 4H-SiC substrates using a
self-aligned fabrication process. The self-aligned fabrication process required no critical alignments
and allowed for high channel packing densities ranging from 2.9x103 to 5x103 cm/cm2. Devices
were fabricated with a range of finger widths. Devices with the narrowest fingers were able to block
up to 450 V with VGS = -3 V. Devices with wider fingers required higher gate voltages ranging
from -10 V to -25 V to achieve similar blocking. Devices were packaged and small-signal and loadpull
measurements were taken with the devices externally matched. Devices having the narrowest
finger design had a small-signal power gain of over 9 dB at around 1.3 GHz. Load-pull
measurements of packaged SITs with 1 cm gate periphery yielded a maximum power gain of ~ 8.2
dB at 1 GHz, VDD = 100 V, and VGS = 1.2 V. Due to the high packing density, these results translate
to power densities of 22 kW/cm2.
RF Characteristics of a Fully Ion-Implanted MESFET on a Bulk Semi-Insulating 4H-SiC Substrate
Authors: Ogata Makoto , Katakami S. , Ono Shuichi , Arai Manabu
Published: March 2009

We fabricated a 0.5-μm gate MESFET on a bulk semi-insulating 4H-SiC substrate by
using ion implantation for the channel layer and contact region. Nitrogen ions were implanted to
obtain a 0.25-μm-thick box-shaped profile with a doping density of 3.0×1017/cm3 for the channel
region and to obtain a 0.2-μm-thick box-shaped profile with a doping density of 2.0×1020/cm3 for
the contact region. Activation annealing is done in argon ambient at 1300 °C for 30 minutes. A 0.5-
μm gate MESFET with 100-μm gate width showed a cut-off frequency of 7.5 GHz and a maximum
oscillation frequency of 22.2 GHz. And its saturated output power was 25 dBm (3.16 W/mm), power
gain was 6.7 dB and PAE was 15.7%.