bluuebunny/crossref_metadata_2025 huggingface dataset:
Electric Field Strength Dependent Electric Conductivity in Highly Insulating Materials
Authors: Neagu Eugen R. , Marat-Mendes José N.
Published: March 2009

The electric conductivity σ in highly insulating materials is determined by the
equilibrium thermally generated carriers and by the injected carriers. The injected excess electrons will dominate the thermally generated electrons when the total number of injected electrons substantially exceeds the total number of initially empty electron traps existing in the material. Under these circumstances the electrical charge transport mechanism is no longer ohmic. In order to analyze the dependence of σ upon injected/trapped charge, isothermal and non-isothermal currents
in Teflon FEP have been investigated at various temperatures, field strengths, in a vacuum or in ambient air conditions. At temperatures below 413 K, for charging times longer than about 10 s but shorter than about 600 s, the electric conductivity is almost electrical field strengths independent proving that the injected charge plays a minor role. For these conditions the charge is mostly trapped in superficial traps. At higher temperatures σ is field dependent. The final thermally stimulate discharge current has a peak around 500 K with a mean apparent activation energy
around 1.35 eV. For a well conditioned sample the peak current is strongly dependent on the charging electric field and on the mean trapping depth of the injected charge. The relaxation time of the trapped charge is around 106 s at 523 K, proving that the injected charge is very stable, a fact of significant importance for applications.
Thermoelectrets from Poly(acrylonitrile) Thin Films: A Trapped Charge Stability Study
Authors: Marat-Mendes José N. , Neagu Eugen R.
Published: March 2009

Thermoelectrets of poly(acrylonitrile) have been prepared for various electric field
polarization strengths. The thermally stimulated discharge current technique has been used to study the remanent charge (dipolar and/or trapped charge) stability. The measurements were carried out in a vacuum. Two overlapping peaks and a significant increase of the current at high temperature have been observed. The first peak is centered around 372 K and the second one is centered around the polarization temperature. When the polarizing field increases from 0.47 to 1.2
MV m-1 the apparent activation energy varies from 1.08 to 1.40 eV, revealing a weak polarization field strength dependence, while the relaxation time at infinite temperature τ0 decreases from 2.05 x10 –15 to 1.05 x 10-18 s. The relaxation time at 300 K increases from 3.48 x 106 to 1.7 x 109 s indicating that the trapped electric charge may be stable at room temperature for the given polarization conditions.
Immobilization of Thrombin Inhibitors on Polyesters Surface: An Original Approach towards Materials Blood Compatibilization
Authors: Salvagnini Claudio , Marchand-Brynaert Jacqueline
Published: March 2009

Piperazinyl-amide derivatives of N--(3-trifluoromethyl-benzenesulfonyl)-L-arginine were synthesized as graftable thrombin inhibitors. Their biological activity was evaluated in vitro, against human -thrombin, and in blood coagulation assay. The piperazinyl-amide derivatives were found to inhibit the activity of -thrombin in the micromolar range. The designed molecules were fixed on poly(ethylene terephthalate) (PET), and poly(butylene terephthalate) (PBT) by wet chemistry treatment (activation of hydroxyl chain-ends) and photochemistry (nitrene insertion by photoactivation of aromatic azide). The protocols were validated by X-ray photoelectron spectroscopy (XPS) and by radiochemical assay (liquid scintillation counting, LSC).
Effect of Thermal Treatment for Pd and PdSi Schottky Contacts on p-GaN
Authors: Tan C.K. , Aziz Azlan Abdul , Yam F.K. , Lim C.W. , Zainuriah Hassan , Hudeish A.Y.
Published: March 2009

Pd Schottky diode exhibited stable rectifying behavior up to 500°C for 35 minutes in
sequential annealing; with the Schottky barrier heights (SBHs), ΦB (I-V) of 0.6-0.7eV with the
leakage current (LC) of 20 A at -5V. With the same range of SBHs, PdSi diodes were stable up to
500°C for 5 minutes with the LC of 0.182mA at -5V. The electrical characteristics obtained in this
study are also compared with those obtained for Pd and PdSi Schottky diodes on p-GaN.
Influence of Carbon Concentration and Rotational Temperature on Fullerene Yield in RF Reactor
Authors: Todorović-Marković B. , Marković Z. , Mohai I. , Nikolić Z.M. , Farkas Z. , Szépvölgyi J.
Published: March 2009

In this paper, report on fullerene formation in a radio-frequency (RF) thermal plasma reactor has been presented. In order to determine the degree of evaporation of the graphite precursor used, analysis of SEM micrographs of deposited soot in different parts of RF reactor has been made. It was found that the degree of graphite evaporation and fullerene yield varied depending on the distance from the plasma torch nozzle. Carbon concentration and rotational temperature of C2 radicals in plasma flame have been calculated as well. The concentration of C2 radicals in plasma flame, which participated in fullerene formation, was in the range of (1.75-3.88)×1020 m-3.
Structural Effects in Electrocatalysis: Formic Acid Oxidation at Model and Real Pt Catalysts
Authors: Lović J.D. , Gojković S.Lj. , Popović K.Dj. , Tripković D.V. , Tripković A.V.
Published: March 2009

Formic acid oxidation was studied at low-index Pt single crystals (model systems) as well as at the platinum catalyst supported on high area carbon (real catalyst) in HClO4. The Pt single crystals were characterized by LEED. The LEED patterns obtained after a mild heating of flame-annealed crystals have shown clean, well ordered unreconstructured surfaces. Pt-C supported catalyst was analyzed by AFM and STM in air and by XRD. AFM and STM images revealed the presence of Pt-C agglomerates of several tenth of nm consisting of Pt particles ranged from 2 nm to 6 nm. The electrocatalytic activity of these catalysts in formic acid oxidation increased in a sequence: Pt(100) < Pt(110) < Pt-C/GC < Pt(111).
SEM and XRD Characterization of Ni-Hf Alloys at Low Hf Concentration
Authors: Umićević Ana , Mahnke H.E. , Cekić Bozidar , Grbović Novaković Jasna , Koteski V. , Belošević-Čavor J.
Published: March 2009

The alloying and phase formation in Ni-Hf samples with 0.2-, 2-, and 5-at.% Hf were
studied by X-ray diffraction (XRD) technique and scanning electron microscopy (SEM). Both
characterization methods, XRD and SEM, reveal the presence of the HfNi5 phase (fcc structure)
where the excess Ni atoms are present in the form of Ni or Ni-rich segregations in the sample
containing 5-at.% Hf. The sample with 2-at.% Hf is characterized by the presence of the two phases
present in the 5-at.% sample and by Hf atoms, which occupy substitutional lattice positions in the
Ni lattice. Finally, in the third sample with 0.2-at.% Hf, the Hf atoms mainly substitute the Ni atoms
in the lattice. This analysis is being complemented with additional information on the local structure
around Hf by extended X-ray absorption fine structure spectroscopy (EXAFS).
Modification of Dynamic Properties of SBR Rubber Composites with Silica Fillers
Authors: Lazić N.L. , Budinski-Simendić J. , Petrović Z.S. , Plavšić M.B.
Published: March 2009

Silica fillers are used in rubber composites to modify their dynamic-mechanical
properties. Three fillers are used: a commercial filler of precipitated silica type Vulkasil- S and two
fillers obtained by its treatment in different ways: thermally and hydrothermally. The purpose is not
only to obtain higher hysteresis of the composite at low temperatures and lower hysteresis at
elevated temperature (which is optimal for good tire performance), but to understand the reasons of
such changes in elastomer materials behavior and also possibilities to increase the corresponding
trends. Both modified fillers exhibited required trends in comparison with the original commercial
one. More detailed analyses of their dynamical behavior indicate interdependence between of filler
particle size, morphology of particle aggregates and ratio of elastic to loss moduli, influencing all
together the dynamic properties of products.
Desorption Behaviour in Nanostructured MgH2-Co
Authors: Montone Amelia , Grbović Novaković Jasna , Stamenković Lj. , Pasquini Luca , Fiorini Anna Lisa , Bonetti Ennio , Vittori Antisari Marco
Published: March 2009

The influence of the Co addition and synthesis route on desorption properties of MgH2
were investigated. Ball milling of MgH2-Co blends was performed under Ar using different
milling intensities and different weight ratios. Microstructural and morphological
characterization, performed by XRD and SEM, show a huge correlation with thermal stability
and hydrogen desorption properties investigated by DSC. A complex desorption behaviour is
correlated with the dispersion of the catalytic particles that appears to play a main role in
desorption performances. The optimum catalyst concentration was found to be around 10 wt.%,
while the optimum value of the ball to powder ratio was 10:1.
Three Dimensional Microstructures: Statistical Analysis of Second Phase Particles in AA7075-T651
Authors: Rollett Anthony D. , Campman Robert , Saylor David
Published: March 2009

This paper describes some aspects of reconstruction of microstructures
in three dimensions. A distinction is drawn between tomographic approaches that
seek to characterize specific volumes of material, either with or without diffraction,
and statistical approaches that focus on particular aspects of microstructure. A
specific example of the application of the statistical approach is given for an
aerospace aluminum alloy in which the distributions of coarse constituent particles are
modeled. Such distributions are useful for modeling fatigue crack initiation and
propagation.
Hydrogen Accumulation during Fatigue Deformation of Al-Mg-Si Base Alloys
Authors: Horikawa Keitaro , Kobayashi Hidetoshi
Published: March 2009

Hydrogen accumulation during fatigue of bake-hardened Al-Mg-Si alloys was investigated by means of hydrogen microprint technique. As a result of S-N curve relation as a function of testing frequency, effect of environmental hydrogen on fatigue properties was not clearly identified. Based on the low cycle fatigue test with 60MPa stress amplitude, it was revealed that hydrogen was preferentially accumulated on slip lines and that distribution of hydrogen emission was changed in the crack propagation direction. Hydrogen was preferentially accumulated at the coarse slip lines near the fatigue cracks where the separation of slip planes was observed in the fracture surface. On the other hand, hydrogen was observed on the slip lines arranged like steps where the fatigue striations were formed in the fracture surface. At near the final fracture area where the finer slip lines were formed on specimen surface, hydrogen was arranged on each slip lines formed by multiple slips. Morphology of hydrogen accumulation on slip lines was not changed when the testing frequency was changed from 2Hz to 15Hz.
Interfacial Microstructure of A6111/Steel Lap Joint Fabricated by Defocused Laser Beam Welding
Authors: Lee Kwang Jin , Kumai Shinji , Ishikawa Nobuhiro , Furuya Kazuo
Published: March 2009

Lap joining of A6111 alloy and steel (SPCC: Steel Plate Cold-rolled C) plates was
performed using a defocused YAG laser beam. A detailed investigation was performed on the
intermetallic compound (IMC) layer formed at the weld interface. Two representative joints
fabricated under different welding conditions were selected and the effect of the welding conditions
on the kind and morphology of the IMC was investigated using a transmission electron microscope
(TEM). An electron diffraction pattern method was used to identify IMC. It was found that the
morphology and kind of IMC formed at the weld interface were strongly affected by the welding
conditions, in particular, by the amount of heat input during welding. The thickness of the IMC layer
formed at the weld interface was about 1 μm and the average grain size of the IMC in the layer was
less than 300 nm when the joining was carried out with a small amount of heat input. The IMC layer
was composed of Fe3Al, FeAl, Al2Fe, Al5Fe2 and Al13Fe4 in this case. However, the thickness of the
IMC layer was around 6 μm when the joining was carried out under high heat input conditions. In this
case, the IMC layer was composed of coarse Al5Fe2 (5 μm) and Al13Fe4 (1 μm). Therefore, it is
considered that the reduced bonding strength of the joint with a thick IMC layer is due not only to the
overall morphology of the IMC layer but also to the formation of coarse Al-rich IMCs in the layer.
Interface Reactions of Al and Binary Al-Alloys on Mild Steel Substrates in Controlled Atmosphere
Authors: Fragner Werner , Zberg Bruno , Sonnleitner Roman , Uggowitzer Peter J. , Löffler Jörg F.
Published: March 2009

To meet the requirements of weight-saving and low-cost production of components for
future transport vehicles, the concept of multi-material mix is of increasing importance. In this
context aluminum-iron compounds produced by means of compound casting are considered to be of
particular importance. An essential and critical aspect of such compound castings is the formation
of intermetallic phases (IMP) at the Al-Fe interface. Both the nature and the kinetics of potential
IMPs are not well understood and require a systematic investigation.
In this paper we document the interface formation of pure Al and binary Al-alloys on a mild steel
substrate by means of isothermal wetting experiments. Tests were carried out employing the sessile
droplet method in a controlled atmosphere. Using pure Al and Al7Si, Al7Cu, and Al7Zn alloys the
interface reactions were investigated by quantitative metallography (LOM, SEM/EDX). Special
attention was paid to the influence of the alloying elements on the type and sequence of IMPs at the
interface.
Designing Aluminium Alloys for a Recycling Friendly World
Authors: Das Subodh K.
Published: March 2009

Recycling aluminum alloys has been shown to provide major economic benefits, as a result it is appropriate for the aluminum industry and the United States as a whole to identify, develop, and implement all technologies that will optimize the benefits of recycling. This paper will focus primarily alloy design for optimizing the reuse of recycled metal; this is both the most forward looking as we move toward a more recycling friendly world and the most overlooked for its potential in maximizing the recycle loop. Some specific approaches to alloy design for recycling are put forth, and some specific compositions for evaluation are proposed. Options for moving forward to further capitalize of the advantages of aluminum recycling are also addressed.
Metallurgical Mechanisms Controlling Mechanical Properties of Aluminium Alloy 2219 Produced by Electron Beam Freeform Fabrication
Authors: Domack Marcia S. , Taminger Karen M. , Begley Matthew
Published: March 2009

The electron beam freeform fabrication (EBF3) layer-additive manufacturing process
has been developed to directly fabricate complex geometry components. EBF3 introduces metal
wire into a molten pool created on the surface of a substrate by a focused electron beam. Part
geometry is achieved by translating the substrate with respect to the beam to build the part one
layer at a time. Tensile properties have been demonstrated for electron beam deposited aluminum
and titanium alloys that are comparable to wrought products, although the microstructures of the
deposits exhibit features more typical of cast material. Understanding the metallurgical
mechanisms controlling mechanical properties is essential to maximizing application of the EBF3
process. In the current study, mechanical properties and resulting microstructures were examined
for aluminum alloy 2219 fabricated over a range of EBF3 process variables. Material performance
was evaluated based on tensile properties and results were compared with properties of Al 2219
wrought products. Unique microstructures were observed within the deposited layers and at
interlayer boundaries, which varied within the deposit height due to microstructural evolution
associated with the complex thermal history experienced during subsequent layer deposition.
Microstructures exhibited irregularly shaped grains, typically with interior dendritic structures,
which were described based on overall grain size, morphology, distribution, and dendrite spacing,
and were correlated with deposition parameters. Fracture features were compared with
microstructural elements to define fracture paths and aid in definition of basic processingmicrostructure-
property correlations.
Non Destructive Three Dimensional Imaging of Aluminium Alloys
Authors: Maire Éric , Buffière Jean Yves , Mokso R. , Cloetens P. , Ludwig Wolfgang
Published: March 2009

This paper generally presents different techniques available to image the microstructure of
materials in three dimensions (3D) at different scales. It then focuses on the use of the more
versatile of these techniques for aluminum alloys : X-ray tomography. The paper describes the
recent improvements (spatial and the temporal resolution, grain imaging). Electron tomography is
also presented as a promising technique to improve the spatial resolution.
Field Assisted Sintering Consolidation of Al-Si-Fe-X Alloy Powder/Flakes Produced through Air Atomization/Melt Spinning
Authors: Sastry K.Y. , Froyen Ludo , Vleugels Jef , Van der Biest Omer , Schattevoy R. , Hummert K.
Published: March 2009

Melt-spun flakes and air atomised powder of a multi-component Al-Si-Fe-X alloy were
consolidated by field assisted (FAST) or spark plasma sintering (SPS) in vacuum using steel dies
and punches. Experiments were carried out at 350, 400, 450 and 500°C under applied loads ranging
from 81 to 283 MPa. The resulting compacts were microstructurally and mechanically
characterized. Ultimate strength values up to 1000 MPa and plastic strains up to 20% were observed
during compression tests. The effect of the powder shape on the sintering behaviour is compared.
The effect of process parameters such as temperature and applied load on the densification and
mechanical properties is discussed. It was found that compacts sintered from melt-spun flakes
resulted in a higher strength and ductility than compacts produced from air-atomized powder,
sintered under identical conditions.
Impact and Fatigue Crack Growth Behaviour of a Yield Strength Graded Al-Zn-Mg Alloy
Authors: Bakshi Sarmistha , Kumar Subodh
Published: March 2009

Impact properties and fatigue crack growth behavior of a newly developed Al-Zn-Mg
functionally graded material (FGM) is studied. The gradient in terms of hardness (about 85 to 130
VHN) and yield strength (about 260 to 360 MPa) is established along the width of the Charpy-impact
and Compact Tension specimens. In both these test specimens two types of FGMs, depending on the
direction of crack propagation, are produced. In the first case, FGM-I, the notched surface is made
harder and the hardness value decreases towards the other surface in the direction of crack growth. In
the second case, FGM-II, the hardness gradient is reversed and the crack propagation takes place from
the softer side to the harder side. The impact and fatigue crack growth experiments are also carried out
for the homogeneous materials with different hardness values and the results obtained from the FGMs
are compared with them.
The results of impact tests show that FGM-II absorbs about 20% greater energy than the highest
energy absorbed by any of the isothermally aged homogeneous materials. Fatigue crack growth studies
for the FGM-I show a reduction in crack growth rate as the crack propagates towards softer (ductile)
side and finally crack arrest is observed. On the other hand, for the case of FGM-II, where the crack
propagates towards the harder side, the crack growth rate first increases and then decreases. However,
in this case the crack follows a tortuous path and it starts bending upwards after about 20 mm crack
length, which might be responsible for higher energy absorption in impact tests.
Effect of Mn Intermetallic Particle on Microstructure Development of P/M Al-Zn-Mg-Cu-Mn Alloy
Authors: Morimoto Yoshifumi , Adachi Hiroki , Osamura Kozo , Kusui Jun , Okaniwa Shigeru
Published: March 2009

The Mesoalite alloy is formed using rapidly solidified powder metallurgy (RS-P/M) by hot extruding the RS powder produced by the atomization method. Meso20 is a Mesoalite alloy with a chemical composition of Al-9.5Zn3Mg-1.5Cu-4Mn-0.04Ag (mass%). Meso20 contains fine grains and precipitated intermetallic Mn compounds, and has a tensile strength of 910 MPa. During hot extrusion, dynamic recrystallization occurs and the fine grains develop. During heat treatment of Meso20, rod-like and granular Mn intermetallic compounds precipitate. The rod-like compounds are about 1 Ìm in length and the granular compounds are about 1 Ìm in diameter. X-ray diffraction measurement, transmission electron microscopy and energy dispersive X-ray (TEM/EDX) analysis and Rietveld analysis revealed the chemical composition of the granular and rod-like Mn intermetallic precipitates to be 86.5Al-10.9Mn-0.4Cu-0.9Zn-1.3Mg and 80.5Al - 10.3Mn-4.2Cu-2.5Zn-2.5Mg (mass%), respectively. The granular and rod-like compounds were identified as the Al6Mn and Q phases, respectively, with both belonging to the space group Cmcm. The lattice constants of Al6Mn were a=0.754 nm, b=0.648 nm c=0.855 nm and those of the Q phase were a=0.765 nm b=2.34 nm c=1.25 nm. Meso10, with a chemical composition of Al-9.5Zn-3Mg-1.5Cu-0.04Ag (mass%), contains no Mn and does not have fine grains, but rather coarse fibrous grains elongated along the extrusion direction. Thus the Mn intermetallic precipitates in Meso20 clearly affect the formation of fine grains. Microstructure development was studied during hot extrusion by observation using high resolution Electron Back Scattering Pattern method. Fine grains were found to develop in areas, which were relatively abundant in granular Mn intermetallic precipitates.
Effects of Alloy Chemistry and Solidification Rate on the Mechanical Properties of an Al-9Si-1Cu Alloy for Powertrain Applications
Authors: Emadi Daryoush , Mackay Robert , Whiting L.V. , Sokolowski Jerry , Sahoo Mahi
Published: March 2009

The potential use of an Al-9Si-1Cu alloy (W328 alloy) as a replacement for W319 alloy in engine blocks was investigated.. The ambient mechanical properties (tensile, hardness and fatigue) of sand and permanent mould cast test bars along with bars machined from a sand cast automotive component were studied. The tensile properties were evaluated in as-cast and T6 heat-treated conditions. The effects of Fe and Mn on properties were also investigated. The castings in W328 alloy exhibit lower porosity than W319 alloy, which is attributed to the smaller solidification range and feeding distance and larger volume fraction of the eutectic phase. Higher iron levels increased the level of intermetallics and reduced properties. The addition of Mn did not offset the effect of higher iron levels. The W328 alloy offers some advantages over the 319 alloy and is a potential candidate for production of automotive components such as engine blocks and cylinder heads.
Feeding Blockage of Aluminium Horizontal Continuous Casting
Authors: Chen X. Grant
Published: March 2009

In recent years, the horizontal continuous casting has been increasingly applied in a
variety of aluminum products such as busbars, T-bars, foundry ingots, small diameter extrusion
billets and forging feedstock, due to its high productivity and relatively low cost. By introducing the
continuous process for long cast periods, feeding blockage as a unique process-related complex
problem has emerged, which causes casting defects, a short cast duration and even an unexpected
interruption of the cast. A literature review of the feeding blockage phenomena during continuous
casting in the steel and aluminum industries is presented. The causes and mechanisms of feeding
blockage in the aluminum horizontal continuous casting are proposed and discussed. Typical
examples of feeding blockage from the industrial scale production with results of metallographic
examination are illustrated.
Rheo-Extrusion of A7075 Aluminium Alloy Utilizing Semi-Solid Slurry Manufactured by Simple Method
Authors: Nagata Ryotaro , Uetani Yasuhiro , Takagi Hidetoshi , Matsuda Kenji , Ikeno Susumu
Published: March 2009

In order to extrude A7075 aluminum alloy soundly from melt without using feed stock billet, rheo-extrusion was tried by utilizing semi-solid slurry with fine solid granules made by employing cooling tube. When the melt moving down inside thin tube was adequately cooled in different ways and introduced into an extrusion container kept at semi-solid temperature of 873K, structure of solidified slurries were granular and mean grain sizes of about 60 to 120μm could be obtained. Subsequently, these slurries were extruded to round bars at various extrusion ratios (28 to 64) and press ram speed of 10mm/s, just after cooling to 833K. The newly developed slurries could easily be extruded to bars with smooth surfaces at lower forces. Although every tensile strength of extruded bars were lower than that of hot-extruded one, there was a tendency that finer the solid granules in slurry, higher the tensile strength of extruded bar.
Nature of Formation of the Areas Having an Ultrafine Grain Structure in Al-Li-Mg System Alloys
Authors: Alekseev A.A. , Setjukov O.A. , Lukina E.A. , Fridlyander I.N.
Published: March 2009

The structure of Al-Li-Mg system alloy 1420, containing a small quantity of Sc, Zr, Ti was investigated in cast, homogenized, hot-pressed, quenched and aged conditions, using the methods of optical metallography, transmission electron microscopy and X-ray examination. An existence of areas, having fine grains (20-30 nm)- "Ultrafine Grain areas"(UFGA) was observed in all the investigated conditions. UFGA are located on the boundaries, sub boundaries and S1(Al2MgLi) phase particles. UFGA can also form near the particles of crystallization origin. These areas have a complex phase composition. Inside the UFGA the particles of S1(Al2MgLi) phase and also δnon-phase, investigated in [1] are always present whereas δ'(Al3Li) precipitations are absent. These areas are formed during crystallization and hot deformation. Their composition changes during the treatment. The nature of these changes is considered.
Key Microstructural Features Responsible for Improved Stress Corrosion Cracking Resistance and Weldability in 7xxx Series Al Alloys Containing Micro / Trace Alloying Additions
Authors: Mukhopadhyay A.K. , Prasad K. Satya , Kumar Vikas , Reddy G. Madhusudhan , Kamat S.V. , Varma V.K.
Published: March 2009

The commercial 7xxx series Al alloys are based on medium strength Al-Zn-Mg and high strength Al-Zn-Mg-Cu systems. The medium strength alloys are weldable, whilst the high strength alloys are nonweldable. On the other hand, the Cu-free, weldable alloys suffer from poor SCC resistance. It is the purpose of this article to provide quantitative data and microstructural analysis to demonstrate that small additions of either Ag or Sc to Al-Zn-Mg and Al-Zn-Mg-Cu alloys bring about very significant improvement in SCC resistance and weldability, respectively. The improvement in SCC resistance of the Cu-bearing alloys due to over aging and retrogression and reaging (RRA) is further discussed in light of a similar improvement in the SCC resistance of these alloys, when peak aged, due to Ag and Sc additions.
Microstructure and Phase Composition of Al-Ce-Cu Alloys in the Al-Rich Corner
Authors: Belov Nikolay A. , Khvan A.V. , Alabin A.N.
Published: March 2009

Al–Cu–Ce alloys have been studied in the Al-rich corner using the microstructural (LM and SEM), thermal (direct and DSC), X-ray diffraction and electron probe microanalysis techniques. Three cross-sections were of particular interest: (a) at 20%Cu (up to 12.5%Ce), (b) at 14%Cu (up to 10%Cu) and (c) at a ratio Cu:Ce=2:1 (up to 10%Ce and 20%Cu). As-cast alloys and those after annealing at 540 and 590°C were studied. Boundaries of appearance of the Al8CeCu4 primary crystals and ternary eutectic involving the phase Al2Cu were determined. The radial cross section (Cu:Ce=2:1) is supposed to be of quasibinary type as ternary eutectic does not form. The temperature and concentrations of the eutectic reaction L–(Al)+CeCu4Al8 were found to be 610°C, 14%Cu and 7%Ce. This binary eutectic has fine microstructure and is capable to fragmentation and spheroidization during heating. The paper considers possibility of using the Al–Cu–Ce system for developing novel Al casting alloys with significantly improved casting properties (hot tearing and fluidity) in comparison with 2xx commercial alloys.
Effect of Al3Ni and Mg2Si Eutectic Phases on Casting Properties and Hardening of an Al-7% Zn-3% Mg Alloy
Authors: Belov Nikolay A. , Cheverikin V.V. , Eskin Dmitry G. , Turchin A.N.
Published: March 2009

The formation of eutectics in Al–Zn–Mg–Ni and Al–Zn–Mg–Si systems is studied by means of metallography, DSC, EPMA, X-ray spectroscopy and thermodynamical calculations. Polythermal sections of the corresponding phase diagrams are constructed. The concentrations and temperatures of binary eutectic reactions L → (Al) + Al3Ni and L → (Al) + Mg2Si in quaternary alloys are determined. Nonequilibrium solidification in Al–7% Zn–3% Mg-based alloys ceases at approximately 480 °C. The alloys close by composition to binary eutectics have considerably improved casting properties as compared to the base Al–7% Zn–3% Mg composition. In particular, hot tearing susceptibility is much less in alloys with Al3Ni or Mg2Si. These results are corroborated by measurements of thermal contraction during solidification. The alloys containing binary eutectics exhibit much lower temperatures of contraction onset and less thermal strain is accumulated in the solidification range. Fine eutectic morphology enables fragmentation and spheroidization of intermetallic particles during annealing. The presence of Al3Ni and Mg2Si particles does not decrease the precipitation hardening effect associated with precipitation of the T′ (AlMgZn) phase. Improved casting properties and good mechanical properties of castings allow the application of Al–Zn–Mg alloys with binary eutectics formed by Al3Ni or Mg2Si as foundry alloys.
The Effect of Alloy Addition on the High Temperature Properties of Over-Aged Al-Si(CuNiMg) Cast Alloys
Authors: Cho Young Hee , Joo Dae Heon , Kim Chul Hyun , Lee Hu Chul
Published: March 2009

The role of alloying elements in the improvement of the high temperature
strength of Al-12Si(CuNiMg) cast alloys used for automotive piston applications was
investigated. The addition of alloying elements such as Mn, Cr, Ti and Ge was studied
and the detailed characterization of the composition and morphology of the
constituent phases after over aging at 350 for 1000 hrs was performed. The
compositions and volume fractions of the equilibrium phases determined by
thermodynamic calculation were compared with the experimental results. The
addition of transition elements, including Mn, Cr and Ti, increased the volume
fraction of the intermetallic phases, which effectively enhanced the high temperature
strength of the alloys. Among these transition elements, Mn turned out to be the most
effective alloying element. After adding up to 0.5wt% of Mn, a large number of
intermetallic phases, α-Al(Mn,Fe)Si as well as fine Al6(Mn,Fe) particles were
precipitated and a significant improvement in the elevated temperature properties was
achieved. The addition of Ge promoted the precipitation of the θphase (metastable
phase, θ-Al2Cu), due to the formation of GeSi precipitates, thereby improved the
mechanical properties of the alloy after T6 heat treatment. However, the presence of
these GeSi precipitates did not affect the coarsening of the θ phase to form Qphase(
Al5Cu2Mg8Si6) during aging and, thus, the elevated temperature properties were
not improved by the addition of Ge.
Age-Hardening Behaviour and HRTEM Observation of Precipitates in Excess Mg Type Al-Mg-Si-Ag Alloy
Authors: Furihata Azusa , Matsuda Kenji , Nakamura Junya , Ikeno Susumu , Uetani Yasuhiro
Published: March 2009

In this work, the age-hardening of Al- 1.0 mass% Mg2Si- 0.4 mass% Mg – 0.5 mass% Ag
(ex.Mg-Ag alloy) alloy has been investigated. It showed increase of hardness and age-hardening
response. Precipitates in this alloy aged at 523 K have been observed by high resolution
transmission electron microscopy (HRTEM) and classified into five types based on characteristics
in their HRTEM images.
An Investigation of the Solubility of Scandium in Iron-Bearing Constituent Particles in Aluminium Alloys
Authors: Røyset Jostein , Leinum J.R. , Øverlie H.G. , Reiso Oddvin
Published: March 2009

Twelve different aluminium alloys with constant iron (Fe) and scandium (Sc) contents of 0.5 wt.% and 0.2 wt.%, respectively, were cast and subsequently homogenised. The distribution of Sc in the microstructure was examined by means of Energy Dispersive X-ray Spectroscopy (EDX) in Scanning Electron Microscope (SEM). Emphasis was put on measuring the solubility of Sc in the Fe-bearing phases of the investigated alloys. It was found that the amount of Sc tied up in Febearing phases is so low that it can be regarded as negligible, with the possible exception of α- AlFeMnSi (Al15(Fe,Mn)3Si2) and the π-phase (Al8FeMg3Si6). A quaternary AlFeSiSc phase with a composition close to Al10Fe3Si5Sc2 may have been discovered.
Corrosion of Painted Aluminium Sheet
Authors: Scamans Geoff M. , Afseth Andreas , Thompson George E. , Liu Y. , Zhou Xiao Rong
Published: March 2009

Over the past ten years a detailed understanding of the dominant factors controlling the corrosion susceptibility of painted aluminium alloy sheet used for architectural and automotive applications has been developed. Work carried out in this field will be reviewed and the different modes of cosmetic corrosion that can occur-, the mechanisms of surface activation, and the role of different thermo-mechanical processing steps on controlling corrosion susceptibility for different alloy systems, including Al-Mn, Al-Mg and Al-Mg- Si-(Cu) will be discussed. The critical role of chemical or electro-chemical cleaning prior to pre-treatment and coating will be highlighted and prospects for meaningful accelerated testing will be discussed.
Surface Segregation of Indium by Heat Treatment of Aluminium
Authors: Graver Brit , van Helvoort Antonius , Walmsley John Charles , Nisancioglu Kemal
Published: March 2009

High temperature heat treatment of aluminium alloys causes surface enrichment of the trace elements in Group IIIA - VA, specifically the low melting point elements Pb, Bi, In and Sn. The phenomenon has practical significance in promoting certain types of localised corrosion, such as galvanic and filiform corrosion, while mitigating other types, such as pitting corrosion of the bare surface. The purpose of this paper is to investigate the surface enrichment and microstructure of indium relative to the available data for Pb. Model binary AlIn alloys, containing 20-1000 ppm of In, were used after heat treatment at various temperatures. In addition to electrochemical investigations, the microstructures were characterised by field emission scanning electron microscopy (FEG SEM) and field emission transmission electron microscopy (FEG TEM). Heat treatment at temperatures as low as 300°C gave significant segregation of In as opposed to 600°C for Pb. As a result of this and yet unresolved oxide film breakdown mechanism on aluminium, In was significantly more effective than Pb in anodically activating aluminium. These results suggest the possibility that significant activation earlier observed on certain commercial alloys as a result of low temperature heat treatment may be due to the trace elements In.
Surface Modification of Aluminium Alloys
Authors: Wada Tadahiro , Fujiwara Junsuke
Published: March 2009

One of the surface modification methods is proposed in this report to improve the wear
resistance of light metal such as aluminum alloys. At first alumite layer is formed on the surface of
aluminum alloy JIS A6061 which was used as the substrate with anodic oxidation treatment method.
Then thin layer of CrN is coated with sputtering method, and diamond like carbon (DLC) layer is
finally coated with ion plating method. The influence of the thickness of the alumite layer on
wear-resistance is experimentally investigated. The critical load of the coated aluminum alloy in
scratch test is measured with the surface property tester, and the wear amount of the coated
aluminum alloy is measured with the SUGA abrasion tester. The main results obtained are as
follows: (1) The critical load of coated aluminum alloy with the alumite layer in the scratch test is
higher than that without the alumite layer. (2) The wear amount of the coated aluminum alloy
increased with the increase of the thickness of the alumite layer. (3) This combined surface
treatment method can become new surface modification method because this method provided
excellent adhesive strength and good wear-resistance.
Advanced Coatings on High Temperature Applications
Authors: Narita Toshio , Izumi Takeshi , Nishimoto Takumi , Shibata Yoshimitsu , Thosin Kemas Zaini , Hayashi Shigenari
Published: March 2009

To suppress interdiffusion between the coating and alloy substrate in addition to ensuring slow oxide
growth at very high temperatures advanced coatings were developed, and they were classified into four groups,
(1) the diffusion barrier coating with a duplex layer structure, an inner σ−(Re-Cr-Ni) phase as a diffusion barrier
and outer Ni aluminides as an aluminum reservoir formed on a Ni based superalloy, Hastelloy X, and Nb-based
alloy. (2) the up-hill diffusion coating with a duplex layer structure, an inner TiAl2 + L12 and an outer β-NiAl
formed on TiAl intermetallic and Ti-based heat resistant alloys by the Ni-plating followed by high Al-activity
pack cementation. (3) the chemical barrier coating with a duplex layer structure, an inner* γ + β + Laves three
phases mixture as a chemical diffusion barrier and an outer Al-rich γ-TiAl as an Al reservoir formed by the two
step Cr / Al pack process. (4) the self-formed coating with the duplex structure, an inner α-Cr layer as a
diffusion barrier and an outer β-NiAl as an Al-reservoir on Ni-(2050)at% Cr alloy changed from the δ-Ni2Al3
coating during oxidation at high temperature. The oxidation properties of the coated alloys were investigated at
temperatures between 1173 and 1573K in air for up to 1,000 hrs (10,000 hrs for the up-hill diffusion coating). In
the diffusion barrier coating the Re-Cr-Ni alloy layer was stable, existing between the Ni-based superalloy (or
Hastelloy X) and Ni aluminides containing 1250at%Al when oxidized at 1423K for up to 1800ks. It was
found that the Re-Cr-Ni alloy layer acts as a diffusion barrier for both the inward diffusion of Al and outward
diffusion of alloying elements in the alloy substrate. In the chemical barrier coating both the TiAl2 outermost
and Al-rich γ-TiAl outer layers maintained high Al contents, forming a protective Al2O3 scale, and it seems that
the inner, γ, β, Laves three phase mixture layer suppresses mutual diffusion between the alloy substrate and the
outer/outermost layers.
Effect of Chromium Content on the Oxidation Behaviour of High-Speed Steels under Dry and Moist Air Environments
Authors: Monteiro Mauricio J. , Rizzo F.C.
Published: March 2009

Development and use of high-speed steels for manufacturing the roll outer shell of hot
strip mills represented a major recent technological advancement in the hot rolling field. However,
it was observed that the oxidation behavior of these steels was different from that of conventional
rolls. The high-speed steel oxidation rate is about four times higher than the alloys previously used.
Furthermore, the rolling conditions are quite aggressive. Contact of the roll with the hot strip, air
and water of the cooling system is expected to increase the oxidation of the roll surface in this wet
atmosphere. Therefore, it is necessary to study their oxidation behavior in order to achieve the full
potential of high-speed steel rolls for hot strip mills. In the present work, the oxidation behavior of
three high-speed steels with differences in chromium content was studied. Corrosion tests were
carried out in a thermobalance under dry and moist (12.5 % H2O) atmospheres at 765oC for 240
minutes. The corroded samples were examined by X-ray diffraction, scanning electron microscopy
and energy dispersive micro-analysis. It was found that the variation of chromium content of the
high-speed steels studied was sufficient to influence the oxidation behaviour. Samples with high
chromium contents presented smallest final mass gain. The presence of humidity had a significant
effect on the oxidation behavior.
Strain Tolerance and Microstructure of Thermal Barrier Coatings Produced by Electron Beam Physical Vapor Deposition Process
Authors: Wada Kunihiko , Ishiwata Yutaka , Yamaguchi Norio , Matsubara Hideaki
Published: March 2009

Several kinds of thermal barrier coatings (TBCs) deposited by electron beam physical vapor deposition (EB-PVD) were produced as a function of electron beam power in order to evaluate their strain tolerance. The deposition temperatures were changed from 1210 K to 1303 K depending on EB power. In order to evaluate strain tolerances of the EB-PVD/TBCs, a uniaxial compressive spallation test was newly proposed in this study. In addition, the microstructures of the layers were observed with SEM and Young’s moduli were measured by a nanoindentation test. The strain tolerance in as-deposited samples decreased with an increase in deposition temperature. In the sample deposited at 1210 and 1268 K, high-temperature aging treatment at 1273 K for 10 h remarkably promoted the reduction of the strain tolerance. The growth of thermally grown oxide (TGO) layer generated at the interface between topcoat and bondcoat layers was the principal reason for this strain tolerance reduction. We observed TGO-layer growth even in the as-deposited sample. Although the thickness of the initial TGO layer in the sample deposited at high temperature was thicker, the growth rate during aging treatment was smaller than those of the other specimens. This result suggests that we can improve the oxidation resistance of TBC systems by controlling the processing parameters in the EB-PVD process.
High Temperature Passive Oxidation Mechanism of CVD SiC
Authors: Goto Takashi
Published: March 2009

The passive oxidation mechanism of CVD SiC was discussed from experimental
results with high-temperature thermogravimetry and thermodynamic analyses. The bubble
formation temperature around 1900 K could be too low for an oxygen inward diffusion limited
process but conform to a CO outward diffusion limited process. The parabolic rate constant
(kp) had weak oxygen partial pressure (PO2) dependence, kp ∝ PO2
n where n = 0.09 to 0.12.
These n values may be consistent with the CO outward diffusion limited process. The
activation energy of kp obtained in the present study, 210 kJ/mol, could suggest a different
mechanism from the well-approved oxygen molecule permeation limited process at lower
temperatures below 1600 K. Amorphous phase was significantly contained in SiO2 scales
formed in an N2-O2 atmosphere. No effect of the amorphous formation on kp was identified.
The Materials Science Beamline EDDI for Energy-Dispersive Analysis of Subsurface Residual Stress Gradients
Authors: Genzel Christoph , Denks Ingwer A. , Klaus Manuela
Published: March 2009

In April 2005 the materials science beamline EDDI (Energy Dispersive DIffraction),
which the HMI operates at the Berlin synchrotron storage ring BESSY, started user service. The
high energy white synchrotron beam up to about 150 keV used for the diffraction experiments is
provided by a superconducting 7 Tesla multipole wiggler. Starting with some basic information on
the technical parameters of the beamline, its set-up and measuring facilities, the paper focuses on
the application of white beam diffraction to the analysis of residual stress fields in the near surface
zone of polycrystalline materials. The concept of a program system is introduced, which we offer to
our users for preparing and evaluating their measurements performed at the EDDI beamline.
Residual Stress in High-Pressure Water Jet Assisted Turning of Austenitic Stainless Steel
Authors: Habak Malek , Lebrun Jean Lu , Waldmann Stefan , Robert Patrick , Fischer Cyril
Published: March 2009

In this paper, the effect of a high pressure water jet, directed into the tool chip interface,
on surface residual stresses and chip shape, in face turning of AISI 316L stainless steel has been
investigated. Tests have been carried out with a standard cutting tool. This tool is not specifically
meant for the machining of this type of material. The cutting speeds used were 80 m/min and
150 m/min, with a constant feed rate of 0.1 mm/rev and a constant cutting depth of 0.1 mm. Three
jet pressures were used: 20, 50 and 80 MPa. Residual stress profiles have been analysed using the
X-ray diffraction method in both longitudinal and transversal directions. The results show that by
using a high pressure jet directed into the tool-chip interface, it is possible to create a well
fragmented chip in contrast to the continuous chip formed using dry turning. It is also possible to
control the chip shape and increase tool life. When the jet pressure is increased the residual stress at
the surface decreases however it is increased by an increase in cutting speed. It can be concluded
that surface residual stresses can be reduced by the introduction of a high pressure water jet. A
reduction in the residual stress value by about 20 to 40 % can be observed when using high pressure
water jet assisted turning compared to dry turning. Also, it has been observed that the jet pressure
does not have a great influence on the depth affected by residual stress and by hardening.
Residual Stresses in Sintered Diamond-Cobalt Composites
Authors: Crostack H.A. , Selvadurai-Lassl Ursula , Tillmann Wolfgang , Gathen Miriam , Kronholz Christian , Wroblewski Thomas , Rothkirch André
Published: March 2009

Manufacturing diamond-cobalt composites by sintering results in residual stresses due to
the mismatch of thermal expansion coefficients mainly. To understand the influence of
manufacturing process parameters on residual stresses of sintered diamond-cobalt composites
samples are produced by different process parameters. The investigated diamond composites are
pressureless sintered as well as pressureless sintered combined with hot isostatically pressing. Here
the influence of powder characteristics and process parameters like compaction pressure and
sintering temperature on the residual stresses and microstructure was analysed by X-ray diffraction,
microscopy and tomography. The aim of this study is to correlate residual stresses with
manufacturing parameters and to give hints for optimising the residual stress state and for
improving the lifetime of diamond-cobalt composites.
Where Would the Electronic States of a Small Graphite-Like Carbon Island Contribute to the SiC/SiO2 Interface State Density Distribution?
Authors: Thill Christoph , Knaup Jan , Deák Peter , Frauenheim Thomas , Choyke Wolfgang J.
Published: March 2009

The high density of interface electron traps in the SiC/SiO2 system, near the conduction
band of 4H-SiC, is often ascribed to graphitic carbon islands at the interface, although such clusters
could not be detected by high resolution microscopy. We have calculated the electronic structure of
a model interface containing a small graphite-like precipitate of 19 carbon atoms, with a diameter
of ~7 Å, corresponding to the experimental detection limit. The analysis of the density of states
shows only occupied states in the band gap of 4H-SiC near the valence band edge, while carbon
related unoccupied states appear only well above the conduction band edge.