bluuebunny/crossref_metadata_2025 huggingface dataset:
The Important Role of Dissolved Elements (Mn, Fe) in the Process of Rolled Products and Their Effects on Final Properties
Authors: Hasenclever Jochen
Published: March 2009

The important role of dissolved elements, such as manganese or iron, in the production process of
rolled material was in the focus of this investigation.
In the AlMn-alloys the content of manganese in solid solution is first controlled by other alloying
elements such as silicon and iron. The addition of silicon or / and iron reduces the level of
manganese in solid solution in the as-cast condition as well as in the following preheating process
step. Another major parameter is the final annealing treatment of the rolled products. The
preheating treatment and the final annealing are the key parameters to control the level of
manganese in solid solution and the size and distribution of the fine dispersoids.
In the AlFe-series alloys the iron content in solid solution is first controlled by the casting process
DC or CC and the amount of iron in the alloy composition. In the as-cast condition the dissolved
iron level is normally higher in the CC-material than in the DC-material. The intermediate
annealing treatment also has a great influence on the content of iron in solid solution.
They recovery and recrystallisation behaviour is controlled by the content of manganese or iron in
solid solution. The precipitation of manganese or iron during thermal treatment leads to optimum
dislocation pinning and results in a high thermal stability. On the other hand, if the precipitation of
manganese or iron interacts with the occurence of recrystallisation, the resulting grain structure can
show coarse grain.
Modelling Microstructure and Properties: The Contributions of Grain Size, DAS and Bifilms
Authors: Campbell John , Tiryakioğlu Murat
Published: March 2009

The modelling of microstructure, and hence the properties, of cast alloys has so far been attempted assuming the liquid metal is free from defects. The growing appreciation that bifilms, of size measured in millimeters, are usually abundant in liquid metals, and control many features of the casting, has led to this paper in which some of the known and some of the expected effects are reviewed. It is suggested that bifilms cause major effects on microstructure and properties and their presence can vastly overpower the effect of traditionally simulated structural features.
Effect of Thermomechanical Processing on Texture and Mechanical Properties of Al-Cu-Li Alloy Plate
Authors: Cho Alex , Long Z. , Lisagor B. , Bales T. , Domack Marcia S. , Wagner John A.
Published: March 2009

For 2195-T8 plate, design properties are based on the mechanical properties at the near surface location, corresponding to the load carrying thin membrane location in machined integrally stiffened structure. Mechanical properties at the near surface location are lower than those at the t/4 and t/2 locations. This work examined the effect of alternate temper and hot rolling practices on near surface strength levels. Results showed that alternate hot rolling practice were very effective in raising near surface strengths and improving property uniformity, and were well correlated with crystallographic texture measurements.
The Role of Copper in the Precipitation Kinetics of 6000 Series Al Alloys
Authors: Esmaeili S. , Lloyd David J.
Published: March 2009

The role of Cu in precipitation behavior of 6000 series aluminum alloys has been investigated by isothermal calorimetry and transmission electron microscopy. The newly developed analytical techniques have been used to evaluate the precipitation kinetics in alloys with or without an initial pre-aging history. It has been found that Cu addition results in increasing the rate of precipitation when artificial aging is applied immediately after solutionizing and quenching. However, Cu has no significant effect on the kinetics of precipitation in alloys with the pre-aging history, while it produces finer microstructures in the pre-aged and then artificially aged alloys. These observations have been explained by the effect of Cu on increasing the rate of precipitate nucleation in 6000 series alloys. It has also been suggested that the effect of Cu on nucleation arises from the role of Cu on the cluster formation during and/or immediately after quenching.
Grain Refinement Performance of Aluminium Cast-Alloy by Deformed Al-Al3Ti Alloy Refiner
Authors: Sato Hisashi , Ota Kentaro , Watanabe Yoshimi , Zhang Zuo Gui , Tsuzaki Kaneaki
Published: March 2009

Grain refining experiments for casting of pure Al were conducted to evaluate the grain
refinement performance of an Al-5mass%Ti alloy refiner before and after cold rolling. Al3Ti
particles in the Al-Ti alloy refiner were efficiently fragmented by cold rolling. The size of the
Al3Ti particles in cold rolled Al-Ti alloy refiner decreased from 280μm to 30μm with increasing
reduction ratio of cold rolling. Mean size of α-Al grains in pure Al cast refined by the cold rolled
Al-Ti alloy refiner decreased from about 500μm to 200μm with increasing the reduction ratio. In
order to investigate mechanical property of the pure Al cast refined by the cold rolled Al-Ti alloy
refiner, Vickers hardness test and tensile test were conducted. Strength of the pure Al cast refined
by the cold rolled Al-Ti alloy refiner increased with increasing the reduction ratio. The strength
improvement of pure Al cast refined by the cold rolled Al-Ti alloy refiner followed Hall-Petch
relationship. From obtained results, it was concluded that cold rolling for refiner is useful
practical application for pure Al cast.
Observations of Intermetallic Compound Formation of Hot Dip Aluminized Steel
Authors: Kim Kee Hyun , van Daele Benny , Van Tendeloo Gustaaf , Yoon Jong Kyu
Published: March 2009

A hot dip aluminizing process to simulate the continuous galvanizing line (CGL) was
carried out in three successive steps by a hot dip simulator: the pre-treatment for removing scales on
the 200 × 250 mm2 and 1mm in thickness cold rolled steel sheet, the dipping in 660°C Al-Si melt for
3s and the cooling. In a pre-treatment, the steel specimen was partly coated by Au to confirm the
mechanism of intermetallic compound (IMC) formation. Scanning electron microscopy (SEM),
energy dispersive X-ray spectroscopy (EDX), and transmission electron microscopy (TEM) analyses
were followed to observe the cross-section and the distribution of the elements. The specimen was
analyzed in the boundary of the dipped-undipped part to see the formation mechanism of the
aluminized steel. An intermetallic compound (IMC) is rapidly developed and grown in the
steel-liquid interface. It has been usually reported that the IMC was formed by the dissolution of iron
in the steel substrate toward the melt and the diffusion of aluminum in an opposite direction. The
specimen is covered with aluminum-10 wt.% silicon, forms the IMC in the part that was not Au
coated. However, IMC is not formed in the Au-coated part. The interface of the dipped-undipped is
also analyzed by EDX. At the interface of the steel-IMC, it is clearly shown that the IMC is only
formed in the dipped part and exists in the steel substrate as well, and contributes by iron, aluminum
and silicon. The result clearly shows that only aluminum diffuses into the steel substrate without the
dissolution of iron and forms the IMC between the steel substrate and the melt. Au coating and the
short dipping time prevent the iron from dissolving into the aluminum melt. By TEM combined with
focused ion beam (FIB) sample preparation, the IMC is confirmed as Fe2SiAl8, a hexagonal structure
with space group P63/mmc.
Effect of Heat Treatment Condition and Alloy Composition on Hydrogen Content in Al-Mg Alloys
Authors: Umeda Hidetoshi , Itoh Goroh , Kato Yoshinori
Published: March 2009

The effect of heat treatment conditions such as atmosphere, temperature, annealing time
and alloying elements on the hydrogen content in Al-Mg based alloys was investigated. The
hydrogen content after annealing depends on the annealing atmospheres and alloying elements.
When annealed in a wet atmosphere, the release of the hydrogen in the Al-Mg alloys to outside and
the absorption of hydrogen from atmosphere into Al-Mg alloys are presumed to occur at the same
time. The oxide layer on the surface is revealed to prevent the hydrogen from being released to
outside. The spheroidal MgO particles can be seen on the surface of Al-Mg alloys after annealing at
550°C. The number of the MgO particles increases with increasing impurity elements such as Si and
Fe, reducing the shielding effect against hydrogen permeration. Therefore, the condensation of
hydrogen near the surface after annealing occurs more easily in an Al-Mg alloy of a high-purity than
that of an ordinary purity.
Characterisation of AlFeSi Intermetallics in 6000 Series Aluminium Alloy Extrusions
Authors: Couper Malcolm J. , Rinderer Barbara , Yao Ji Yong
Published: March 2009

Alloys designed to optimise strength and extrudability have a lower alloy Mg to Si ratio than has commonly been used in AA6060 and AA6063 alloys. Intermetallic phases have an impact on alloy design since they tie up some of the Mg and Si alloy content. The effect of Mg and Si alloy content on the type of intermetallic phases present has been investigated using TEM, SEM and Thermocalc analysis. Results for Al-Mg-Si-Fe alloys with 0.46 - 0.70 wt%Mg, 0.27 - 1.24 wt%Si and 0.09 - 0.22 wt%Fe are presented. The occurrence of a-AlFeSi (various stoichiometries), b- Al5FeSi, p-Al8FeSi6Mg3, Mg2Si and Si has been found to depend on alloy composition within the ranges examined.
Anisotropy Decrease in Sheets of 1424 Al-Mg-Li Alloy
Authors: Khokhlatova L.B. , Kolobnev N.I. , Fridlyander I.N. , Alekseev A.A. , Lukina E.A. , Ber L.B. , Tempus Gerhard
Published: March 2009

The fine-fibrous nonrecrystallized structure determines substantial tensile property anisotropy
of hot rolled 1424 alloy sheets. In the present work the possibility of producing a fully recrystallized
structure in cold rolled sheets was investigated. To improve a technological plasticity a
cold rolling was performed after preliminary annealing of hot rolled sheets. The technological plasticity
was studied by means of determination a critical deformation degree at plane strain compression
at room temperature. The phase composition of hot rolled and annealed sheets was investigated
using TEM and X-ray analysis.
The uniform fine-grained and fully recrystallized structure in sheets was obtained after rolling with
preliminary annealing at 350-380°C and final solid solution treatment. After the indicated above
annealing the maximum volume fraction of the equilibrium S1-phase precipitates was observed in
the alloy. After cooling in air from the annealing temperature it was found a very small quantity of
δ′-phase and after slow cooling with the furnace this phase was practically absent. The fully recrystallized
structure in sheets provides a substantial decrease of the tensile property anisotropy in three
d irections.
Through Thickness Microstructural Gradients in 7475 and 2022 Creep - Ageformed Bend Coupons
Authors: Bakavos D. , Prangnell Philip B. , Bès Bernard , Eberl Frank , Gardiner Simon
Published: March 2009

In creep-ageforming a material experiences continuously variable bending stresses
through its thickness, from tensile to compressive, which are maximum at the surfaces. This can
potentially result in through thickness microstructural gradients, due to interactions between the
bending stresses, creep, and precipitation occurring during ageing, that can alter a component’s
performance. The aim of the work reported here was to develop an understanding of these effects in
an industrial creep ageforming process. For this purpose two aerospace alloys, 7475 and 2022, were
ageformed by Airbus UK using industrial scale ageforming tools. Their microstructures were
analysed in detail by TEM, and SAXS, which revealed significant through thickness microstructural
changes after forming.
Effects of a Small Addition of Cu or Ge on the Microstructure and Mechanical Property of an Al-Si Alloy
Authors: Nakagawa Keiyu , Kanadani Teruto , Nakayama Kenich , Sakakibara Akira
Published: March 2009

In this study, we investigated the effects of a small addition of Cu (0.1%) or Ge (0.1%) on the
microstructure and mechanical property of Al-Si alloys. The results are as follows. The size of
precipitates in the Cu-added or Ge-added alloys is smaller than that in the binary alloy. The size of
the precipitates at the grain boundary in the Cu-added or Ge-added alloys is larger than the size of
the precipitates in the binary alloy. However, the number of the precipitates at the grain boundary in
the Cu-added and Ge-added alloys is smaller than that in the binary alloy. It was found that a small
addition of Cu or Ge has the effect of raising the fatigue strength under repeated tensile loading as
well as the tensile strength.
Effect of Small Additions of Fe on the Tensile Properties and Electrical Conductivity of Aluminium Wires
Authors: Shikagawa Takahiro , Itoh Goroh , Suzuki Shunsuke , Kuroda Hiromitsu , Horikoshi Toshiyuki
Published: March 2009

Although low-alloyed aluminum has been used as electric line and cable materials to date,
there still is a great demand for higher strength with retaining the good electrical conductivity and
ductility. In the study, iron has been chosen as an additive element and the addition effect on the
strength and electrical has been investigated since iron is reported to have a marked
solution-strengthening effect at a given addition amount. Aluminum with 99.99mass% purity and
Al-Fe alloys with iron up to 0.9mass% were induction-melted, continuously cast into a rod with
8mm diameter, and cold-drawn into a wire with 0.3mm diameter. Tensile test and electrical
resistivity measurement were carried out on the rod and wire after each pass. It was found that, in
the rod, the strength increased while the ductility and electrical conductivity decreased as the
addition iron amount was increased. Work hardening occurred clearly at an early stage of cold
drawing, while it became sluggish as the cold reduction increased in each material. At the early
stage, the strengths increased as the iron amount was increased, and at the later stage, the alloy with
iron addition of 0.9mass% had higher strengths and larger elongation to failure.
The Large Strain Flow Stress Behaviour of Aluminium Alloys as Measured by Channel-Die Compression (20-500°C)
Authors: Bacha A. , Maurice Claire , Klocker Helmut , Driver Julian H.
Published: March 2009

Two recent methods for obtaining flow stress-strain relations up to large strains of order 1.5 by channel-die compression are presented: i) for sheet metal formability tests, composite samples have been made of glued sheet layers and deformed at room temperature in a channel-die with the compression axis directed along one of the sheet metal edge directions, i.e. RD or TD. The sheet plane is parallel to the lateral compression die face. It is shown that, using a suitable lubricant, the sample deformation is homogeneous up to strains of 1.5. Tests carried out on 5xxx and 6xxx alloys to evaluate the stress-strain relations show that a generalized Voce law gives a good quantitative fit for the data. ii) for high temperature plate processing, quantitative flow stress data can be obtained up to 500°C with a rapid quench using a hot channel-die set-up. Some new results are presented here for high strain hot PSC tests on Al-Mn and Al-Mg alloys together with microstructure analyses.
TDS Measurement of Hydrogen Released from Stainless Steel Oxidized in H2O-Containing Atmospheres
Authors: Yamauchi Akira , Yamauchi Yuji , Hirohata Yuko , Hino Tomoaki , Kurokawa Kazuya
Published: March 2009

Hydrogen dissolved in the Cr2O3 scale formed on the stainless steel in the
H2O-containing atmospheres is observed by TDS (thermal desorption spectroscopy) measurements.
The amount of dissolved hydrogen in the Cr2O3 scale reaches a maximum about 0.32 mol% when
the H2O concentration in the gas reaches 20%. It was found from GDS (glow discharge
spectroscopy) measurements that hydrogen may exist at the oxide scale / substrate interface or in
Cr2O3 scale bounded that interface. However, results from the Vickers hardness and the observation
of scale morphology by SEM (scanning electron microscopy), hydrogen dissolved in the Cr2O3
scale would have little effect on a decrease in the mechanical property of the Cr2O3 scale. Therefore,
hydrogen dissolved in the Cr2O3 scale may not be main factor of the deterioration of the Cr2O3
scale.
The Relationship between High-Temperature Steam Oxidation and Hydrogen Dissolution in High-Chromium Ferritic Steels
Authors: Nagai K. , Nakai Masaaki , Kunieda Tomonori , Murata Yoshinori , Morinaga Masahiko , Matsuda S. , Kanno M.
Published: March 2009

The high-temperature oxidation in air and steam at 923 K was examined with pure iron, Fe-10Cr and Fe-10Cr-0.08C (0~0.03)S steels. The amount of hydrogen dissolved into samples during exposure to steam was measured with thermal desorption spectroscopy (TDS). It was found that the amount of dissolved hydrogen was related closely to the steam oxidation resistance of the steels. In case of pure iron, the thickness of the oxide scale formed in steam at 923 K for 360 ks was comparable to that of the scale formed in air. On the other hand, in case of the Fe-Cr binary alloy and the ternary ferritic steel, the oxide scale was much thicker in steam than in air. It was found that the amount of the dissolved hydrogen was much larger in both the binary alloy and the ternary ferritic steel than in pure iron, and then it leads to the more accelerated oxidation rate in the ternary steels in steam.
Oxidation Behavior of Pt+Hf-Modified γ-Ni +γ'-Ni3Al Alloys
Authors: Izumi Takeshi , Gleeson Brian
Published: March 2009

The oxidation behavior of Pt+Hf-modified γ-Ni+γ′-Ni3Al alloys containing up to 20 at.%
Pt and either 15 or 20 at.% Al was studied by oxidizing the alloys in air at 1150°C under both
isothermal and thermal cycling conditions. It was found that the co-addition of Pt and Hf was
extremely beneficial to oxidation resistance, to the extent that Ni-20Al-20Pt-Hf and Ni-20Al-10Pt-Hf
alloys (all compositions are in at.%) oxidized at significantly slower rates than that of a Ni-50Al-15Pt
β-NiAl alloy. A Ni-20Al-5Pt-Hf alloy also showed good oxidation resistance, with the steady-state
oxidation rate being almost the same as that obtained for the β alloy. Over a period of up to 500
one-hour oxidation cycles, no oxide spallation from the modified γ+γ′ alloys was observed. From
cross-sectional SEM examination coupled with X-ray diffraction analyses, it was found that a
compact and planar exclusive scale layer of α-Al2O3 formed on the Ni-20Al-20Pt-Hf alloy. By
contrast, the Ni-20Al-10Pt-Hf and Ni-20Al-5Pt-Hf alloys formed a very thin outer layer of NiAl2O4
and a planar inner layer of α-Al2O3. The thickness of the inner Al2O3 layer increased with increasing
oxidation time relative to that of the NiAl2O4 layer, meaning that the latter primarily formed during
the initial stages of scale formation. Both NiO and NiAl2O4 were found in the scales formed on the
Ni-20Al-Hf and Ni-15Al-0~10Pt-Hf alloys, with the thickness of these oxide layers decreasing with
increasing Pt content in the alloys. Further, it was found that the extent of internal HfO2 formation
decreased significantly with increasing Pt content, to the extent that no HfO2 was found in the
oxidized Ni-20Al-20Pt-Hf alloy. Inferences for the observed beneficial effects of Pt promoting
protective Al2O3 formation and decreasing the tendency for Hf to oxidize in γ+γ′ alloys are
discussed.
Development and Application of High Cr-High Si-Fe-Ni Alloys to High Efficiency Waste-To-Energy Boilers
Authors: Kawahara Yuuzou , Sasaki Kouji , Nakagawa Yuuji
Published: March 2009

In order to improve the durability of high efficiency waste-to-energy boilers, it is essential
to develop and apply high temperature corrosion-resistant materials having a long life time according
to the intensity of the corrosion conditions. Two types of high Cr-high Si-Fe-Ni base and high Cr-high
Si-Ni-Fe base alloy seamless tubes; MAC-N (26Cr-3.5Si-11Fe-Ni base) alloy and MAC-F
(23Cr-3.8Si-38Ni-Fe base) alloy respectively which contain no expensive Mo and have better
corrosion resistance than the existing alloys under severe corrosive environments of waste
combustion gas, have developed. The optimum alloy composition range were defermined by
confirming the effect of the alloying elements on the corrosion resistance in the laboratory corrosion
tests. Furthermore, the seamless tubes were mounted on the actual superheater of the 500oC/9.8MPa
high efficiency waste-to-energy boiler to examine the durability over a period of four years. As a
result, it was confirmed that the MAC-N and MAC-F alloys have better corrosion resistance than the
Alloy625 and 310HCbN. In addition, it has become clear that corrosion resistance of both alloys is
displayed through the formation of SiO2 rich protective scale due to the combined addition of the
principal elements, Si, Cr, Fe and Ni. Under conditions of high Cl content molten deposits and severe
thermal cycle, the corrosion rate increases as the results of deterioration of protective oxidation scale.
Experiences with Inconel 625 in Biomass and Waste Incineration Plants
Authors: Montgomery Melanie , Biede Ole , Larsen Ole Hede
Published: March 2009

Inconel 625 is utilised in both biomass and waste incineration plants in Denmark. In both cases, the performance is good however the morphology of corrosion attack is different which indicates different corrosion mechanisms. In waste incineration plants there is general attack and shallow pitting, and in some cases dendritic attack especially on the fins of waterwalls. The dendritic attack is in the dendritic core. The presence of pits or dendritic attack is linked to the temperature of the metallic surface and the molten salt composition. In a woodchip biomass plant, chromium depletion was observed on the surface of the weld overlay leaving behind a nickel and molybdenum rich porous structure. The corrosion attack was not related to the dendritic microstructure of the weld. In two straw-fired biomass plants, co-extruded Sanicro 63 (alloy 625 type) as well as Inconel 625 weld overlay revealed the same type of attack, again chromium depletion. This indicates that the corrosion mechanism in woodchip and straw power plants are similar. Another interesting result in straw-fired boilers was that Nibas welds (alloy 625 composition) could provoke excessive corrosion in adjacent 18-8 stainless steels indicating a galvanic reaction. The corrosion mechanisms observed in each case are discussed in relation to temperature and corrosive environment.
Behaviour of Copper and Nickel during High Temperature Oxidation of Steel Containing Them
Authors: Kondo Yasumitsu
Published: March 2009

Copper and nickel are accumulated in steels when steel scrap is used as steel sources. It is well known that copper causes hot shortness problem and nickel suppresses the effect of copper. In this paper, the behaviour of copper and nickel during oxidation is investigated. Steels containing copper and nickel were oxidized and the distribution of copper and nickel in the scale was examined. It was found that copper is not only enriched at the scale/metal interface but also exists in upper magnetite layer as a state of solid solution and along grain boundaries of the wustite layer as metal phase. From these results an assumption has been proposed that the liquid copper migrates from the scale/metal interface to the magnetite layer along the grain boundaries. On the other hand, nickel enriched in steel side near the scale/metal interface with copper. The metal particles containing nickel and copper remain inside the scale. Nickel also has an effect of the uneven scale/metal interface formation.
Microstructure and Oxidation of Al/BN Composites Fabricated by the Pressureless Infiltration Method
Authors: Lee Dong Bok
Published: March 2009

Metal matrix composites (MMCs) consisting of an Al matrix reinforced with initially
added BN particles and newly formed AlN dispersoids were fabricated using the pressureless
infiltration method. This method led to the incorporation of Mg and nitrogen into the Al matrix. In the
retained BN dispersoids, the depletion of nitrogen and enrichment of Al and Mg occurred. The more
Mg available, the more AlN formed in the MMCs. The oxidation resistance of the prepared MMCs at
773 and 823 K in air was not satisfactory, owing to the formation of MgO-rich scale. Mg, which was
used as an infiltration enhancer precursor, oxidized preferentially, and thereby decreased the oxidation
resistance of the prepared MMCs.
Gas-Tight Oxides - Reality or Just a Hope
Authors: Anghel C. , Hultquist Gunnar , Dong Qian , Rundgren J. , Saeki Isao , Limbäck Magnus
Published: March 2009

A better understanding of the transport properties of gases in oxides is certainly very
important in many applications. In the case of metals, a general protection measure against
corrosion implies formation of a dense metal oxide scale. The scale should act as a barrier against
gas transport and consequently it needs to be gas-tight. This is often assumed but rarely, if ever,
confirmed. Hence there is a need for characterization of micro- and/or meso- pores formed
especially during the early oxidation stage of metallic materials. This paper presents a novel and
relatively straightforward method for characterization of gas release from an oxide previously
equilibrated in a controlled atmosphere. The geometry of the sample is approximated to be a plate.
The plate can be self-supporting or constitute a scale on a substrate. A mathematical model for
calculation of diffusivity and gas content is given for this geometry. A desorption experiment,
involving a mass spectrometer placed in ultra high vacuum, can be used to determine diffusivity
and amount of gas released with aid of the mathematical model. The method is validated in
measurements of diffusivity and solubility of He in quartz and applied in characterization of two Zroxides
and one Fe oxide. From the outgassed amounts of water and nitrogen the H2O/N2 molar ratio
can be used to estimate an effective pore size in oxides.
Aspects of Residual Stress Determination Using Energy-Dispersive Synchrotron X-Ray Diffraction
Authors: Steuwer Axel , Peel Matthew J. , Buslaps Thomas
Published: March 2009

In this paper we discuss certain aspects of residual stress measurements
using energy-dispersive synchrotron X-ray diffraction using very high X-ray energies
in the range up to 200keV. In particular, we focus on the strain resolution and its
relation to the geometric contribution to the instrumental resolution. This energy
range together with the brilliance of insertion devices allows measurements in bulk
materials with penetration approaching those of neutrons, and the technique is
demonstrated to have a high potential for residual stress determination. However, the
use of high X-ray energies implies a relatively small diffraction angle and in turn a
relatively elongated gauge volume, which favours the application of the technique to
essentially 2D problems.
Effect of Residual Stress on High Temperature Deformation in a Weld Stainless Steel
Authors: Wimpory Robert C. , Biglari Farid R. , Schneider Rainer , Nikbin Kamran M. , O'Dowd N.P.
Published: March 2009

This paper considers the measurement of residual stresses induced by mechanical loading in a weld
Type 347 stainless steel. The work is based in part on an ongoing Round Robin collaborative effort
by the Versailles Agreement on Materials and Standards, Technical Working Area 31, (VAMAS
TWA 31) working on ‘Crack Growth of Components Containing Residual Stresses’. The specific
objective of the work at Imperial College London and HMI, Berlin is to examine how residual
stresses and prior straining and subsequent relaxation at high temperature contribute to creep crack
initiation and growth for steels relevant to power plant applications. Tensile residual stresses have
been introduced in the weld by pre-compression and neutron diffraction measurements have been
carried out before and after stress relaxation at 650 oC. Significant relaxation of the residual stresses
has been observed, in agreement with earlier work on a stainless steel. Preliminary results suggest
that the strains local to the crack drop by over 60% after 1000 h relaxation at 650 oC for the weld
steel. The results have been compared with finite element studies of elastic-plastic pre-compression
and stress relaxation due to creep.
Feasibility of Thermal Strain Measurements during Quasi-Steady State Using Neutron Diffraction
Authors: Woo W. , Feng Zhi Li , Wang X.L. , An K. , Bailey W.B. , David S.A. , Hubbard C.R. , Choo Hahn
Published: March 2009

Localized heating was imposed on a 6061-T6 aluminum alloy plate to cause thermal strains,
and simultaneously interplanar spacing changes were measured using in-situ time-resolved neutron
diffraction techniques. Two different methods were used: 1) direct real-time measurements of the
transient behavior and 2) a series of measurements based on the quasi-steady state (QSS) principle.
A comparison of the two results shows that the QSS method can represent the transient behavior
under the current experimental conditions.
X-Ray Diffraction Analysis of Nonuniform Residual Stress Fields σii(τ) under Difficult Conditions
Authors: Klaus Manuela , Denks Ingwer A. , Genzel Christoph
Published: March 2009

Thin hard coatings for wear protection usually do not consist of single layers but of
stacks of alternating sublayers which have to meet different demands. With respect to X-ray residual
stress analysis (XSA) such multilayer systems pose a series of challenges. In addition to those
problems which generally arise in thin film diffraction like small layer thickness or strong texture,
neighbouring sublayers with similar chemical composition may superimpose each other, or sublayers
of identical structure and composition, which contribute to the same diffraction line, are separated
by other sublayers. Starting from a formalism that yields the X-ray penetration depth τ in multilayer
systems of arbitrary sublayer sequences, we show how a combination of measurements using
‘conventional’ photon sources available at any X-ray lab and synchrotron radiation allowing for
wavelength tuning near the TiKβ absorption edge, can be used to evaluate the residual stress state in
the top sublayer stack of a hard coating multilayer system deposited by chemical vapour deposition.
Determination of Welding Residual Stresses with Help of the Micromagnetic Measurement Method
Authors: Bruns Markus , Nitschke-Pagel Thomas
Published: March 2009

The micromagnetic measurement method is a well known technique for a qualitative estimation of
residual stresses in ferromagnetic materials. The application due to the advantages of a fast and
manageable use is hindered by the high complexity of the calibration procedure for the quantitative
residual stress determination when additionally a changing microstructure influences the measured
signals. Therefore basic investigations were performed for the residual stress determination of
welded joints by the micromagnetic method. A multi-parameter approach by using different
micromagnetic techniques was evaluated by a linear regression analysis. For each structural steel a
regression polynomial can be calculated for the residual stress determination of differently welded
specimens. The accuracy of the prediction depends on the magnetization direction. The
experimental results show, that this strategy enables a useful possibility of an easier method for the
determination of residual stresses in welded joints.
Evaluation of Subsurface Distribution of Residual Stress in Austenitic Stainless Steel Using Strain Scanning Method
Authors: Shobu Takahisa , Konishi Hiroyuki , Mizuki Jun'ichiro , Suzuki Kenji , Suzuki Hiroshi , Akiniwa Yoshiaki , Tanaka Keisuke
Published: March 2009

The strain scanning method was applied to the evaluation of the subsurface distribution of
the residual stress beneath the shot-peened surface of an austenitic stainless steel SUS304L which had
coarse grains and preferred orientation. The experiment was performed at beam line BL22XU at
SPring-8 using monochromatic X-rays of 70.14 keV and a Ge (111) analyzer. The sizes of both
incident and receiving slits were 2 × 0.2 mm2. The specimens were annealed or shot-peened and had
the dimensions of 20 × 20 × 5 mm3. The grain size was about 37 μm. In order to obtain the diffractions
from an enough number of grains, various types of oscillation methods, which were translation,
rotation and tilting of the specimen, were examined. The translational oscillation was found to be
enough to obtain the accurate strain distribution. By combining the translational oscillation method
with the correction to the surface aberration, the subsurface distribution of the residual stress of
shot-peened austenitic stainless steel was successfully determined.
Improving NC Milling Skills through Practise of Simulated Work
Authors: Gilles P. , Redonnet J.M. , Lagarrigue P. , Beceril R. , Fraysse B. , Boucharessas V.
Published: March 2009

To allow for enhanced quality while reducing machining time, machines have become increasingly complex, thus leading to an increase in purchase, running and operator training costs. In what follows in the present paper, we shall firstly show how a virtual machine tool can be developed. Secondly, we shall study the influence this tool can have on teaching methods..
Analysis and Validation of Cutting Forces Prediction Models in Micromachining
Authors: Perez H. , Idoipe Antonio Vizan , Perez J. , Labarga J.
Published: March 2009

Many investigations have been developed related to precision machining with features in
the millimetre scale. In this paper different cutting force models for micromilling are analyzed and
compared. A new model based on specific cutting force that also considers run-out errors has been
developed. The estimated cutting forces obtained with this model had good agreement with the
experimental data. Also, the proposed model allows to be implemented within the machine control
for the on-line optimization of the micromilling process.
Surface Roughness Improvement Using Laser-Polishing Techniques
Authors: Lamikiz Aitzol , Sánchez Jose Antonio , López de Lacalle Luis Norberto , del Pozo D. , Etayo J.M.
Published: March 2009

A laser polishing method applied on metallic surfaces is presented in this work. One of the most important applications of this technique is the small-medium injection mould polishing manufactured by rapid manufacturing processes (RM) such as selective laser sintering. The polishing method has been applied to different surfaces including a laser-sintered part. Topography and roughness parameters measurements show that laser polishing can achieve surface improvements up to three times in mean roughness parameter with no macro-geometric deviations.
Forming Gas Annealing of the Carbon PbC Center in Oxidized Porous 3C- and 4H-SiC: An EPR Study
Authors: Cantin J.L. , von Bardeleben Hans Jürgen
Published: March 2009

Previous Electron Paramagnetic Resonance (EPR) studies identified the carbon dangling
bond center as the main paramagnetic interface defect in 3C, 4H, 6H-SiC/SiO2. We demonstrate
that this defect, called PbC center, can be passivated by forming gas annealing at 400°C. We have
measured the PbC density at annealed 4H- and 3C-SiC/SiO2 interfaces and attributed its reduction to
the transformation of the dangling bonds into EPR inactive C-H bonds. We have also studied the
reverse phenomenon occurring during vacuum annealing at temperatures ranging from 600°C up to
1000°C and have determined a dissociation energy of ≈4.3 eV for the 3C and 4H polytypes.
Hybrid Physical-Chemical Vapor Transport Growth of SiC Bulk Crystals
Authors: Fanton Mark A. , Li Qiang , Polyakov A.Y. , Cavalero R.L. , Ray R.G , Weiland B.E. , Skowronski Marek
Published: March 2009

The effects of H2 addition to the growth ambient during physical vapor transport
(PVT) growth of 6H and 4H SiC were investigated using SIMS, DLTS and Hall effect
measurements. Using this hybrid physical-chemical vapor transport (HPVT) approach, boules were
grown using Ar-H2 and He-H2 mixtures with H2 concentrations up to 50 at%. Thermodynamic
modeling suggests that addition of H2 improves the carbon transport in HPVT compared to standard
PVT. This should lead to a substantial decrease in the concentration of residual N donors and the
concentration of electron traps. This is confirmed by the experimental results. As expected, the
source transport rate increased as H2 was added to the growth environment due to increased C
transport. The background nitrogen concentration and the free electron density decreased
significantly with increasing H2 concentration. The formation of electron traps (activation energies
of 0.4 eV, 0.6-0.65 eV, 0.7 eV, 0.9 eV and 1 eV) was also strongly suppressed. These changes were
observed for H2 concentrations as low as 4 at%. The decreased N concentration improves the
ability to produce high resistivity SiC material, and for H2 concentrations as high as 10-25%, the
very first wafers cut from the seed end of the boules have a resistivity exceeding 106 cm.
Characterization of Low Stress, Undoped LPCVD Polycrystalline SiC Films for MEMS Applications
Authors: Dunning J. , Fu Xiao An , Mehregany Mehran , Zorman Christian A.
Published: March 2009

This paper details the characterization of polycrystalline SiC (poly-SiC) thin films
deposited by low pressure chemical vapor deposition. Films were deposited on both Si and SiO2-
coated Si substrates using dichlorosilane (SiH2Cl2) and acetylene (C2H2) as precursor gases. Low
residual tensile stress films were deposited at 900°C at a pressure of 2 Torr using SiH2Cl2 and C2H2
(5% in H2) flow rates of 35 sccm and 180 sccm, respectively. XRD analysis of these films
indicated a (111) 3C-SiC orientation regardless of substrate material. Both resistivity (1.3 -cm)
and residual stress gradient (17 MPa/μm) were found to be relatively low and decreased as the film
thickness increased. Unintentional nitrogen doping is responsible for the low resistivity
measurements and its concentration in the films was about 1.86 x 1016 cm-3. Poly-SiC films
exhibiting near-zero residual tensile stress, low stress gradient and relatively low resistivity have
favorable properties for design and fabrication of MEMS devices.
Growth of SiC Single Crystal from Si-C-(Co, Fe) Ternary Solution
Authors: Yashiro Nobuyoshi , Kusunoki Kazuhiko , Kamei Kazuhito , Hasebe Mitsuhiro , Ujihara Toru , Nakajima Kazuo
Published: March 2009

We carried out the growth of single crystalline silicon carbide (SiC) from Si-C-X (X= Co,
Fe) ternary solutions. These ternary solutions are expected to show large carbon solubility
compared with Si solvent (self-flux) by means of CALPHAD (CALculation of PHAse Diagrams)
method. We investigated the growth rate and the polytype of the grown crystal from the ternary
solutions. Then we found that the growth rate from the ternary solutions is much larger than that
from the self-flux. The growth rate from Si-C-Co (Si-C-Fe) system was about 6mm/hr (12mm/hr)
while that from the self-flux was only 2mm/hr. The grown crystal from the ternary solutions is
classified into 6H that takes over the seed polytype.
4.5 kV-8 A SiC-Schottky Diodes / Si-IGBT Modules
Authors: Tournier Dominique , Waind Peter , Godignon Philippe , Coulbeck L. , Millan José , Bassett Roger
Published: March 2009

Due to the significant achievements in SiC bulk material growth and in SiC device
processing technology, this semiconductor has received a great interest for power devices,
particularly for SiC high-voltage Schottky barrier rectifiers. The main difference to ultra fast
Si pin diodes lies in the absence of reverse recovery charge in SiC SBDs. This paper reports
on 4.5kV-8A SiC Schottky diodes / Si-IGBT modules. The Schottky termination design and
the fabrication process gives a manufacturing yield of 40% for large area devices on standard
starting material. Modules have been successfully assembled, containing Si-IGBTs and
4.5kV-SiC Schottky diodes and characterized in both static and dynamic regimes. The
forward dc characteristics of the modules show an on-resistance of 33mohm.cm2 @ room
temperatue (RT) and a very low reverse leakage current density (JR < 10 5A/cm2 @ 3.5kV).
An experimental breakdown voltage higher than 4.7kV has been measured in the air on
polyimide passivated devices. This value corresponds to a junction termination efficiency of
at least 80% according to the epitaxial properties. These SiC SBDs are well suited for high
voltage, medium current, high frequency switching aerospace applications, matching perfectly
as freewheeling diodes with Si IGBTs.
10 kV, 87 mΩcm2 Normally-Off 4H-SiC Vertical Junction Field-Effect Transistors
Authors: Li Yu Zhu , Alexandrov Peter , Zhang Jian Hui , Li Larry X. , Zhao Jian Hui
Published: March 2009

SiC JFET, compared with SiC MOSFET, is attractive for high power, high temperature
applications because it is free of gate oxide reliability issues. Trenched-and-Implanted VJFET (TIVJFET)
does not require epi-regrowth and is capable of high current density. In this work
we demonstrate two trenched-and-implanted normally-off 4H-SiC vertical junction field-effect
transistors (TI-VJFET), based on 120μm, 4.9×1014cm-3 and 100μm, 6×1014cm-3 drift layers. The
corresponding devices showed blocking voltage (VB) of 11.1kV and specific on-resistance (RSP_ON)
of 124m7cm2, and VB of 10kV and RSP_ON of 87m7cm2. A record-high value for VB
2/RSP_ON of
1149MW/cm2 was achieved for normally-off SiC FETs.
Low On-Resistance in 4H-SiC RESURF JFETs Fabricated with Dry Process for Implantation Metal Mask
Authors: Masuda Takeyoshi , Fujikawa Kazuhiro , Shibata Kaoru , Tamaso Hideto , Hatsukawa Satoshi , Tokuda Hitoki , Saegusa Akihiko , Namikawa Yasuo , Hayashi Hideki
Published: March 2009

We fabricated 4H-SiC lateral JFETs with a reduced surface field (RESURF) structure,
which can prevent the concentration of electric field at the edge of the gate metal [1]. Previously, we
reported on the 4H-SiC RESURF JFET with a gate length (LG) of 10 μm [2]. Its specific on-resistance
was 50 mΩcm2, which was still high. Therefore, a Ti/W layer was used as an ion implantation mask
so as to decrease the thickness of the mask and to improve an accuracy of the device process. A
RESURF JFET with the gate length (LG) of 3.0 μm was fabricated, and the specific on-resistance of
6.3 mΩcm2 was obtained. In this paper, the fabrication process and the electrical characteristics of the
device are described.
Fabrication of 700V SiC-SIT with Ultra-Low On-Resistance of 1.01mΩ•cm2
Authors: Tanaka Yasunori , Yano Koji , Okamoto Mitsuo , Takatsuka Akio , Fukuda Kenji , Kasuga Masanobu , Arai Kazuo , Yatsuo Tsutomu
Published: March 2009

Silicon carbide static induction transistors with submicron buried p+ gate (SiC-BGSITs)
have been successfully developed through innovative fabrication process. A submicron buried p+
gate structure was fabricated by the combination of submicron trench dry etching and epitaxial
growth process on a trench structure. As the device performance is mainly determined by the width
of the p+ gate region and the spacing between two adjacent p+ gate regions, corresponding to the
width of n- channel, we have optimized these parameters carefully using a device simulator. The
breakdown voltage VBR and specific on-resistance RonS of the fabricated BGSIT were 700 V at a
gate voltage VG = –12 V and 1.01 m/·cm2 at VG = 2.5 V and a drain current density JD = 200 A/cm2,
respectively. This RonS is the lowest on-resistance for ~ 600V class power switching devices,
including other wide-bandgap materials such as GaN.
Growth of Cubic Silicon Carbide Crystals from Solution
Authors: Eid Jessica , Santailler Jean Louis , Ferrand Bernard , Ferret Pierre , Pesenti J. , Basset Alain , Passero Antoine , Mantzari Alkyoni , Polychroniadis Efstathios K. , Balloud Carole , Soares P. , Camassel Jean
Published: March 2009

Cubic-silicon carbide crystals have been grown from solution by using the traveling-zone
method. In this technique a molten silicon zone heated by induction coils is held between two rods
of polycrystalline silicon carbide. Due to the growth set-up and boundary conditions, different mass
transfer mechanisms are operative : diffusion, buoyancy, Marangoni convection and forced
convection. The growth experiments have been performed on various seed crystals. Cubic SiC
crystals were grown with a [111] habit on the [0001] silicon faces of 4H SiC seeds. The polytype
3C-SiC was identified by Transmission Electron Microscopy. Micro Raman spectroscopy and
photoluminescence analyses showed good crystalline quality with few 6H inclusions.
Time Domain and Frequency Analysis of Random Telegraph Signal and the Contributions of G-R Centres to I-V Instabilities in 4H-SiC MESFETs
Authors: Trabelsi Mohamed , Sghaier Nabil , Bluet Jean Marie , Yacoubi Noureddine , Guillot Gérard , Brylinski Christian
Published: March 2009

Our work is focused on the identification of defects responsible for current fluctuations at
the origin of low frequency noise or random telegraphic signals in 4H-SiC MESFETs on semiinsulating
(SI) substrates. We show that devices having instabilities have DC output characteristics
with random discrete fluctuations of the drain current. The RTS noise parameters analysis
(amplitude, high and low state time durations) as a function of temperature and bias voltage
provides the signature of the involved traps (activation energy and cross section both for emission
and capture). From the power spectral density of the drain current noise (PSD) we have measured
the cut-off frequency of a single trap even at very low frequencies (from 0.1 Hz) and we propose
that the noise responsible of RTS fluctuations is a generation-recombination noise. Finally, it is
shown that the frequency analysis of the random telegraphic signal is a well-suited tool for the study
of single defects in very small devices.
A Study on the Reliability and Stability of High Voltage 4H-SiC MOSFET Devices
Authors: Krishnaswami Sumi , Ryu Sei Hyung , Heath Bradley , Agarwal Anant K. , Palmour John W. , Geil Bruce , Lelis Aivars J. , Scozzie Charles
Published: March 2009

Gate oxide reliability measurements of 4H-SiC DMOSFETs were performed using the
Time Dependent Dielectric Breakdown (TDDB) technique at 175°C. The oxide lifetime is then
plotted as a function of the electric field. The results show the projected oxide lifetime to be > 100
years at an operating field of ~3 MV/cm. Device reliability of 2.0 kV DMOSFETs was studied by
stressing the gate with a constant gate voltage of +15 V at a temperature of 175°C, and monitoring
the forward I-V characteristics and threshold voltage for device stability. Our very first
measurements show very little variation between the pre-stress and post-stress conditions up to
1000 hrs of operation at 175°C. In addition, forward on-current stressing of the MOSFETs show the
devices to be stable up to 1000 hrs of operation.
Optimisation of 4H-SiC MOSFET Structures for Logic Applications
Authors: Horsfall Alton B. , Prentice C.H.A. , Tappin Peter , Bhatnagar Praneet , Wright Nicolas G. , Vassilevski Konstantin , Nikitina Irina P.
Published: March 2009

Although Silicon Carbide has become the material of choice for high power applications
in a range of extreme environments, the interest in creating active chemical sensors requires the
development of transistors for additional control circuits to operate in these environments. Despite
the recent advances in the quality of oxide layers on SiC, the mobility of inversion layers is still low
and this will affect the maximum frequency of the operation for these devices. We present
simulation results which indicate that a delta channel, in both n-channel and p-channel structures, is
suitable for transistors used with these low level signals. By varying the doping levels of the device
we have shown that the optimum delta doping for this application is 1.43x1019 cm-3 for both n and p
channel devices. We then show the effects of high temperatures on the delta FET devices and make
comparisons with standard SiC MOSFET devices.