bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanical Behaviour in the Mushy State during Isothermal Tensile Testing
Authors: Fabrègue Damien , Deschamps Alexis , Suéry Michel , Poole Warren J.
Published: March 2009

In order to improve the understanding of hot tearing during laser welding of aluminium
alloys, the rheology of the alloys in the mushy state must be characterized. The present work
investigates the mechanical behaviour of the aerospace alloy AA6056 using a specially designed
isothermal tensile test in the mushy state. Using a Gleeble thermo-mechanical machine, two
different tests have been performed: i) tests during partial remelting and ii) tests after partial
solidification at a high cooling rate. These tests have been carried out not only on the 6056 alloy but
also on a mix between 6056 and 4047 Al-Si alloy which corresponds to the composition of the
nugget of a laser using a filler wire.
The increase of the solid fraction results in an increase of the maximum stress and a change on the
fracture surface from a smooth dendritic to a more ductile one. Moreover, the alloys exhibit a
typical visco plastic behaviour with an increase of the maximal stress with the strain rate. When the
test is performed at a particular solid fraction of 0.97, the fracture is more erratic and the ductility is
low. The results show the existence of a ductile/brittle/ductile transition with the fraction of solid.
The fracture stress is shown to be higher when testing after partial remelting as compared to partial
solidification for the same solid fraction. This is due to the difference in microstructure of the
mushy zone and more particularly in the connectivity of the solid skeleton. An adapted creep law is
used to describe the mechanical behaviour of alloys during the partial remelting test using the
fraction of grain boundary wetted by the liquid given by Wray. This law is shown to be irrelevant to
the partial solidification tests, as a result of the modified geometry of the liquid phase. From these
tests, we have determined a new law relating the solid fraction to the fraction of grain boundaries
wetted by the liquid. This law is a useful tool to predict the mechanical behaviour when mechanical
loading occurs during solidification.
Modelling the Phase Transformation from Al6(Mn,Fe) to α-Al(Mn,Fe)Si Phase during Homogenization of AA3xxx Alloys
Authors: Li Yan Jun , Håkonsen Arild , Mortensen Dag , Pettersen Tanja , Furu Trond
Published: March 2009

A simplified numerical model for the solid state phase transformation from Al6(Mn,Fe)
to α-Al(Mn,Fe)Si phase in 3xxx alloys has been constructed. In this model, the phase
transformation is assumed to be initiated by the heterogeneous nucleation of α-Al(Mn,Fe)Si
dispersoids at the interface between Al6(Mn,Fe) particle and matrix and the growth of the α-
Al(Mn,Fe)Si phase into the Al6(Mn,Fe) particle is controlled by the diffusion of Si from the matrix.
The model has been implemented into a numerical homogenization model. The simulation results
show that the implementation of the phase transformation model improves much the prediction
results of the homogenization model on the evolution of solid solution level of alloying elements
and the volume fraction evolution of dispersoids in 3xxx alloys during homogenization.
Microstructural Interactions during Stress Ageing a 7475 Aerospace Alloy
Authors: Bakavos D. , Prangnell Philip B. , Bès Bernard , Eberl Frank , Grossmann J.G.
Published: March 2009

In industrial process, like creep-ageforming, materials are aged under load. To investigate
the influence of an applied stress on the ageing behaviour of Cu bearing Al-7xxx series alloys, a
7475 alloy was aged under a constant tensile stress and analysed by means of Small Angle X-ray
Scattering (SAXS) and TEM. Mechanical testing was also employed, to determine if there was any
effect on the materials strength. The results show that during the early stages of ageing significant
interactions takes place, which preferentially aligns one type of GP zone, as well as affecting their
size and volume fraction. During the second stage ageing treatment, the applied stress was observed
to cause more rapid over-ageing, by promoting the formation of the η phase.
Influence of Zinc to Magnesium Ratio and Total Solute Content on the Strength and Toughness of 7xxx Series Alloys
Authors: Clinch M.R. , Harris S.J. , Hepples W. , Holroyd N.J.H. , Lawday M.J. , Noble B.
Published: March 2009

A systematic study of the precipitation processes in high strength Al-Zn-Mg-Cu alloys has been conducted. A series of experimental alloys was prepared with varying Zn:Mg ratio, but equivalent total solute content, to be representative of those used in applications which demand a combination of strength, fracture toughness and resistance to environmentally sensitive cracking mechanisms. Artificial ageing curves were constructed for each alloy, based upon 7xxx series duplex treatments widely used in industry. Ageing kinetics were investigated beyond peak strength into the overaged condition, since this is known to promote the most favourable balance of properties. Differential scanning calorimetry (DSC) and transmission election microscopy (TEM) observations were made on the alloys throughout the ageing process to fully understand the precipitation events occuring. For a particular overageing treatment, higher Zn:Mg ratio alloys were consistently found to be at a more advanced stage of precipitation while higher strengths were retained at low Zn:Mg ratios. Grain boundary characteristics, such as particle size and precipitate free zone width, were also influenced by Zn:Mg ratio at a given strength level. This paper provides new understanding of precipitation kinetics and the control of important microstructural features which influence the balance of properties in 7xxx series aluminium alloys.
Age Hardening of Forged Aluminium Components – Mechanical Properties and Distortion Behaviour after Gas Quenching
Authors: Rose A. , Kessler O. , Hoffmann Fabian , Zoch H.W. , Krug P.
Published: March 2009

For quenching of age hardenable aluminum alloys today predominantly aqueous quenching media are used, which can lead due to the Leidenfrost phenomenon to a non-uniform cooling of the parts and thus to distortion. In relation to the conventional quenching procedures in aqueous media, gas quenching exhibits a number of technological, ecological, and economical advantages. The quenching intensity can be adjusted by the variable parameters gas pressure, gas velocity as well as the kind of gas and thus can be adapted to the requirements of the component. By the higher uniformity and the better reproducibility, gas quenching offers a high potential to reduce distortion. Cost savings would be possible, because of reduced distortion and therefore less reworking. High-pressure gas quenching with nitrogen or helium, as well as air quenching at ambient pressure in a gas nozzle field was applied to the spray formed aluminum alloy Al-17Si-4Fe-3Cu-0.5Mg-0.4Zr (DISPAL S232). Hardness and tensile tests have been carried out to determine the mechanical properties after gas quenching and aging compared to water quenching. The distortion behavior of a forged aluminum component of the spray formed alloy was examined after gas quenching and after water quenching. Gas quenching showed remarkable advantages regarding distortion.
Microstructural Evolution during Ingot Preheat in 7xxx Aluminium Alloys for Thick Semiproduct Applications
Authors: Lim Seong Taek , Lee Yong Yun , Eun Il Sang
Published: March 2009

Recent 7xxx aluminum alloys have been designed for the finite use of thick semiproduct
with contolled amount of constituent phases which mostly evolve during ingot preheat. In this
study, the effects of constitutional change and preheat conditions of 7175 and 7050 type alloys on the
evolution of constituent phases [M-, T-, S-phase and dispersoid] are presented. The constiuents
evolve depending on the constitutional effect, primarily the change of Zn:Mg ratio, preheat condition
comprising temperature and cooling rate following preheat. T- and M-phase are reprecipitated during
cooling after preheat, depending on the alloy constitutions. S-phase is evolved depending on the
constitution and preheat temperature, rather than preheat cooling rate. Prominent precipitation
temperature interval of constituents are discussed in view of quaternary phase evolutions. In addition,
evolutions of dispersoids together with M-phase are discussed. Specific alloy designs and preheat
conditions could provide controlled microstructures for the thick 7xxx semiproducts.
The Influence of Silicon on Age Hardening Kinetics and Phase Precipitation in Al-Mg-Zn Alloys
Authors: Hansen Vidar , Vevecka-Priftaj Aferdita , Fjerdingen J. , Langsrud Y. , Gjønnes J.
Published: March 2009

Solid solution treatment at 450°C and 550°C and subsequent two step age hardening at
100°C and 150 °C up to 144 hrs. have been carried out for two conventional and four experimental
7xxx type of alloys with different Mg, Zn, Fe and Si content. The influence of silicon on phase and
kinetics of age hardening zones and particles has been followed. Increase in silicon required higher
solid solution temperature in order to achieve reasonable age hardening response. High silicon
alloys, solid solution treated at high temperature, have tendency to recrystallize during aging. The
GP-zone formation is affected by the ratio between Mg, Zn and Si. In alloys with Mg/Zn ratio in
the range 1:2 GP(I)-type zones are formed, at higher solid solution temperature also GP(II); low
Mg-content favor GP(II)- zones. In high silicon alloys GP-zones of b’’’-type (from the Al-Mg-Si)
system contribute to age hardening. The precipitation kinetics of the main hardening phase h’, is
influenced by the preceding GP-zone stage.
Influence of an Inclined Cooling Plate on the Production of A356/CNF and A356/SiC MMC by Compocasting
Authors: Mussi R.G.S. , Motegi Tetsuichi , Tanabe Fumi , Kawamura H. , Anzai K. , Shiba D. , Suganuma M.
Published: March 2009

The influence of an inclined cooling plate utilized as a modification in the compocasting process of aluminum alloy is studied in this paper. Based on the crystal separation theory, molten A356 is poured on the inclined copper plate in order to produce solidification nuclei inside the fluid metal, which is, then, mechanically stirred while reinforcement is added through its surface. Carbon nano fibers (CNF) and particulate SiC were utilized as reinforcement, in quantities varying from 0.5 to 15vol%. Dispersion of the reinforcements was observed by macro and microstructure analysis. For CNF, addition of quantities up to 1vol% resulted in homogeneous dispersion through the matrix, although SEM analysis showed the presence of clusters of up to 50μm in some points of the samples. SiC was properly mixed into matrix until 10vol%. Globular crystals were obtained, but some coarsening occurred, especially for small quantities of reinforcement. Utilization of the inclined cooling plate produced good inclusion and homogenization for two different reinforcements through an A356 matrix. The best results were obtained for a 180mm cooling plate, with inclination of 60o. The pouring temperature utilized was 10oC over the melting point of the alloy, and temperature of the tundish was kept around 598oC during stirring.
Filiform Corrosion on 6000 Series Aluminium: Kinetics and Inhibition Strategies
Authors: Coleman A.J. , McMurray H.N. , Williams G. , Afseth Andreas , Scamans Geoff M.
Published: March 2009

High levels of surface shear experienced during rolling, grinding or machining can cause 6000 series aluminium to develop an ultra-fine grained surface layers which dramatically increase susceptibility to filiform corrosion (FFC) under paint films. In-situ Scanning Kelvin Probe (SKP) measurements in humid air are used to compare the kinetics and mechanism of FFC on abraded and lacquer-coated samples of high copper containing AA6111 and low level copper AA6016. FFC is initiated by applying a small volume of aqueous HCl to a penetrative defect on polyvinylbutyral (PVB) coated alloy samples prior to placement in a chamber maintained at constant humidity and temperature. The SKP is then repeatedly scanned over a fixed surface area to produce a time-lapse animation showing the dynamic evolution of localized free corrosion potential patterns. The spatial distribution of potential variation provides insight into the FFC mechanism and the numerical integration of areas of dissimilar potential provides a measure of the time-dependent area of coating delamination. Various possible FFC inhibition strategies are investigated for use under circumstances where removal of the surface layer prior to application of an organic (paint) coating is not feasible. The two strategies shown in this paper are the use of an anti-corrosion pigments based on an intrinsically conducting polymer called polyaniline. An anion-exchange pigment called hydrotalcite is also used.
Properties of Oxide Formed on Aluminium in Aqueous Acetate Buffer
Authors: Giskeødegård N. , Blajiev O. , Hubin A. , Terryn H. , Hunderi Ola , Nisancioglu Kemal
Published: March 2009

The properties of oxide formed on pure aluminium in acetate buffers under controlled
potential, temperature, and pH are characterized by in situ electrochemical techniques and
spectroscopic visual ellipsometry (VISSE). Monitoring the current density (cd) during transition
between different applied potentials gives direct information about Faradaic changes in the oxide
properties, while the ellipsometer monitors the changes in the actual thickness and refractive
index of the film. Electrochemical impedance spectroscopy (EIS) reveals, in addition to film
properties, information about the charge transfer processes and adsorption at steady-state
conditions. VISSE and ex situ transmission electron microscopy (TEM) indicate the presence
of a two layered oxide structure, consisting of the barrier and a porous hydrated layer. The
thickness and density of these two layers are monitored in situ during growth and dissolution.
The thickness of the barrier layer depends reversibly on the applied potential, while the thickness
of the hydrated layer is less affected by the potential. The absorption sensitive parameter is
correlated with the buffer concentration and therefore believed to be related to the acetate.
A Novel Anti-Corrosion Coating for Aluminium Alloy
Authors: Huang Wei , Li Di , Zheng Tian Liang , Guo Min
Published: March 2009

A novel environmental protective water based metallic coating was developed for
aluminum alloys, which mainly contains metal flake, silicate and silane. The coating's properties
were investigated by neutral salt spray test, micro-hardness testing, adhesion test and electrochemical
technique etc. Meanwhile the coating's surface and microstructure was observed by scanning electron
microscopy (SEM). Furthermore, the film forming matter was examined by Fourier transform
infrared spectroscopy (FTIR) test. Results showed that an excellent adhesive, heat-resisting,
protective coating for aluminum alloy could be achieved by this technique. An interpenetrating
polymer network (IPN) was formed in the coating by means of cross linking reaction of
organosilicone and inorganic silicate. In thesis, the film forming mechanism and protection of coating
were also discussed.
Initial Pitting Behaviour of LY12 Aluminium Alloy in Simulated Marine Atmosphere
Authors: Han De Sheng , Guo Min , Li Di
Published: March 2009

By analyzing morphology, weight gain, pitting depth, potential and AC
impendence in corrosion course, initial pitting behavior of LY12 aluminum alloy in
simulated marine atmosphere was studied. Results indicated initial pitting of LY12
was affected much by Cl- sedimentation and atmosphere humidity, little by
temperature below 35°C. Weight gain and pitting depth increased with rising of Clsedimentation
quantity, humidity and temperature. Correlation of weight gain and
time fitted Model Boltzman. In initial pitting course of LY12, open circuit potential
changed little and Nyquist graph had the characteristic of adsorbent resist system.
Temperature and Strain Rate Effects on the Dynamic Strain Ageing of Aluminium Alloy AA7030
Authors: Hörnqvist Magnus , Karlsson Birger
Published: March 2009

The effects of temperature and strain rate on the mechanical properties of aluminium alloy AA7030 (Al-5.4Zn-1.2Mg) in naturally aged and peak aged condition are investigated, with emphasis on the relation to dynamic strain ageing. It is found that the naturally aged material shows more severe signs of dynamic strain ageing, including inverse strain rate and temperature dependence of flow stress, inverse temperature dependence of the ductility and serrated yielding. The peak aged material also shows signs of dynamic strain ageing, but to a lesser extent, most pronounced through serrated yielding. The observed effects can be qualitatively explained in terms of a thermal activation based model for dislocation glide. Furthermore, inhomogeneous deformation is observed on several size scales ranging from localized glide bands to surface deformation effects (orange peel surface) and macroscopic flow localization in shear bands.
Effect of Artificial Aging Temper on the Microstructure and Properties of 7B04 Pre-Stretched Thick Plate
Authors: Zhu Bao Hong , Zhang Yon Gan , Xiong Bai Qing , Li Zhi Hui , Wang Feng , Liu Hong Wei
Published: March 2009

One- and two-step artificial aging had been performed on the 7B04 pre-stretch thick plate, whose nominal composition is similar to 7075 alloy with lower Fe and Si content. The effect of aging temper on the microstructure and properties has been studied. The research results show that T6 temper can improve the mechanical properties of the alloy greatly, yet the alloy have lower electron conductivity which is no more than 19Ms·s-1. When T73 and T74 tempers were performed on the alloy, the mechanical properties of the alloy decreased about 6~10% of the T6 strength while the electron conductivity was improved obviously. With the increasing of the aging temperature, the time that the alloy needs to get peak aging becomes shorter and the mechanical properties at peak aging status are lower. The electron conductivity of the alloy, however, becomes higher with the increasing of aging temperature. The main strengthen phase of 7B04 alloy is also η(MgZn2) phase which is same to other 7xxx series alloys.
Boss Formability of Nano-Structured Aluminium Alloys at Elevated Temperatures
Authors: Park Jong Woo , Chung Young Hoon , Lee Kyong Hwan
Published: March 2009

Together with conventional alloys, ultra-fine or nano-structured aluminum alloys were
prepared by equal channel angular rolling (ECAR) and pressing (ECAP). Formability of cylindrical
bosses was investigated by compression tests of a closed die. Finite element (FE) analysis was also
carried out to investigate the effect of die friction on the forming behavior. Cylindrical bosses with
the aspect ratio over three were formed in a closed die at elevated temperatures even under a
frictional condition, although more uniform deformation was expected under a frictionless condition
by the FE simulation. Boss formability increased with increasing temperature and decreasing strain
rate, and fine structured aluminum alloys had superior boss formability to the conventional alloys.
Near-net shape forming of a simplified cellular phone case was performed at elevated temperatures
using a set of closed dies. A nano-structured aluminum alloy showed higher formability in all
aspects of bosses, sidewalls and face thickness than conventional alloys.
An Analysis on the Forming Characteristics of AA 6063 Aluminium Alloy in Radial-Forward Extrusion Process
Authors: Lee G.M. , Koo H.S. , Choi H.J. , Hwang Beong Bok
Published: March 2009

In this paper, the forming process of a central hub by radial-forward extrusion has been
analyzed by the rigid-plastic finite element method. In this process, the material flows in radial
direction and then deflects 90 degrees into the same direction as that of punch movement. Radial
extrusion is used to produce parts that generally feature a central hub with radial protrusions. Design
factors such as mandrel diameter, punch nose radius, deflection corner radius, gap width in annular
direction, and frictional conditions are applied to the present study by simulation. AA 6063 aluminum
alloy is selected as a model material for analysis in the present study. The influence of these design
factors on the force requirement during the forming operation and the pressure exerted on the tooling
such as the punch and mandrel is investigated and the simulation results are quantitatively
summarized in terms of pressure distribution, force-stroke relationships, and maximum force
requirement, respectively. The main goal of this study is to investigate the effect of those process
parameters on the deformation pattern in radial-forward extrusion process, especially the effect of
deflection corner radius. It has been concluded from the simulation results that a) the frictional
condition between workpiece and tool does not affect the punch load very much, but the load
supported by mandrel is more or less significantly influenced by the frictional condition compared to
that of punch, b) the deflection corner radius turns out to be a major process parameter in terms of
maximum force requirement, and c) a similar trend is found in the punch and mandrel forces during
the radial extrusion process.
An Analysis on the Forming Load of AA 2024 Aluminium Alloy in Combined and Sequence Operation Process
Authors: Hwang Beong Bok , Shim J.H. , Seo Jung Min , Koo H.S. , Ok J.H. , Lee Y.H. , Lee G.M. , Min K.H. , Choi H.J.
Published: March 2009

This paper is concerned with the analysis of the forming load characteristics of a
forward-backward can extrusion in both combined and sequence operation. A commercially
available finite element program, which is coded in the rigid-plastic finite element method, has been
employed to investigate the forming load characteristics. AA 2024 aluminum alloy is selected as a
model material. The analysis in the present study is extended to the selection of press frame capacity
for producing efficiently final product at low cost. The possible extrusion processes to shape a
forward-backward can component with different outer diameters are categorized to estimate
quantitatively the force requirement for forming forward-backward can part, forming energy, and
maximum pressure exerted on the die-material interfaces, respectively. The categorized processes are
composed of combined and/or some basic extrusion processes such as sequence operation. Based on
the simulation results about forming load characteristics, the frame capacity of a mechanical press of
crank-drive type suitable for a selected process could be determined along with securing the load
capacity and with considering productivity. In addition, it is suggested that different load capacities
be selected for different dimensions of a part such as wall thickness in forward direction and etc. It is
concluded quantitatively from the simulation results that the combined operation is superior to
sequence operation in terms of relatively low forming load and thus it leads to low cost for forming
equipments. However, it is also known from the simulation results that the precise control of
dimensional accuracy is not so easy in combined operation. The results in this paper could be a good
reference for analysis of forming process for complex parts and selection of proper frame capacity of
a mechanical press to achieve low production cost and thus high productivity.
Work Hardening Behaviour of an Al-2.8Mg-0.16Sc Alloy
Authors: Fazeli F. , Poole Warren J. , Sinclair Chad W.
Published: March 2009

Despite extensive studies on the aging behaviour of Al3Sc containing alloys, the underlying mechanism of the precipitation strengthening is still not well understood. In particular, the transition radius at which particles become non-shearable is not known. In this work, the work hardening behaviour of an Al-2.8Mg-0.16Sc (wt%) alloy has been characterized for different stages of aging and the corresponding slip line features at the surface of strained specimens have been examined using Nomarski interference contrast. Moreover, the work hardening behaviour is discussed in the framework proposed by Kocks, Mecking and Estrin. It is proposed that changes in macroscopic work hardening behaviour can be used as a signature of the shearable/non-shearable transition.
Experimental Study of the Stretch Flange Formability of Al-Mg Sheet
Authors: Chen Zeng Tao , Worswick Michael J. , Lloyd David J.
Published: March 2009

In this paper, stretch flange forming experiments were performed on the AA5182 and
AA5754 Al-Mg sheet materials. A triple-action servo-hydraulic press, developed at the University
of Waterloo, was used in the experiments. A z-flange tooling, which incorporates mating drawbeads
on the main and backup punches, was employed. Drawbeads are used in commercial stretch flange
operations to control or limit the rate of cutout expansion. Of interest in the current research are the
flange formability and the damage development induced by the bending-unbending of the sheet as it
passes through the drawbeads. Both AA5182 and AA5754 were tested with thickness of 1.6 mm.
Further tests were performed using 1.0 mm AA5182 to examine the effect of thickness. To examine
the effect of cutout size on the formability, cutout radii in the range 88 to 98 mm in increments of 2
mm were tested to failure.
The Die Forgings of High Corrosion Resistance, Wieldable, Super Light 1420 Aluminium Alloy
Authors: Fridlyander I.N. , Grushko O.E. , Denisov B.S. , Varganov V.A.
Published: March 2009

The increase of weight efficiency and flight-technical characteristics of the aircraft engineering is
presently the actual task, requiring the constant search for new materials. The aluminum alloys low
density (< 2500 kg/m3) based on Al-Mg-Li system developed allowed to solve the problem of creating
the pressurized sections of the aircraft airframe, where the basic semiproduct are die forgings
1420 alloy. The tensile mechanical properties, low cycle fatigue at axial loading (LCF), the critical
stress intensity factor under plain strain (K1C), fatigue crack growth (FCGR) were determined in
forgings of 1420 alloy and its weldments.
Precipitation Strengthening in AA7449 Aluminium Alloy: Understanding the Relationship between Microstructure, Yield Strength and Strain Hardening
Authors: Fribourg G. , Deschamps Alexis , Bréchet Yves
Published: March 2009

This paper presents a detailed study of the microstructure and mechanical properties of AA7449 alloy during the two step heat treatment leading to the industrial T7651 temper. It is first shown that reproducing the heat treatment without a deformation step as used in the T7651 industrial temper leads to 2-fold decrease of the precipitation kinetics due to the absence of dislocations, while the resulting mechanical properties (if this change in kinetics is accounted for) are very similar. The work hardening rate is shown to strongly evolve during the heat treatment, and this evolution has been correlated to the evolution of microstructure using a Kocks-Mecking-Estrin analysis. Finally, an analysis in terms of activation volume of the strain rate sensitivity allows for the determination of the dislocation / precipitate interaction in the overaged temper.
Early-Stage Oxidation Behavior of γ'-Ni3Al-Based Alloys with and without Pt Addition
Authors: Hayashi Shigenari , Narita Toshio , Gleeson Brian
Published: March 2009

The early-stage oxidation behavior of γ '-Ni3Al-based alloys of composition (in at.%) Ni-22Al and Ni-22Al with 10, 20, and 30Pt was investigated in terms of oxidation kinetics, scale evolution and resulting composition profiles during heating to 1150°C in air. Platinum addition did not appear to affect the nature of the native oxide layer present on the γ '-based alloys at room-temperature; however, it was found that the presence of increasing Pt content aided in promoting the establishment of a continuous Al2O3 scale during heating the γ '-based alloys through to about 700°C. This beneficial effect can be primarily ascribed to the fact that Pt is non-reactive and its addition decreases the chemical activity of aluminum in γ '. Related to the latter, Pt partitions almost solely to the Ni sites in the ordered L12 crystal structure of γ ', which has the effect of increasing the Al:Ni atom fraction on a given crystallographic plane containing both Al and Ni. Such an effective Al enrichment at the γ ' surface would kinetically favor the formation of Al2O3 relative to NiO. A further contributing factor is that the Pt-containing γ '-based alloys showed subsurface Pt enrichment during the very early stages of oxidation. This enrichment would reduce Ni availability and increase the Al supply to the evolving scale, thus kinetically favoring Al2O3 formation.
Preparation of Highly Oxidation-Resistant Surface by Molten Salt Electrodeposition
Authors: Hara Motoi , Fukumoto Michihisa
Published: March 2009

In order to prepare a highly oxidation-resistant surface for TiAl and SUS 304 stainless steel, the molten salt electrodeposition of Al or Y on these metals was carried out. The electrodeposition was conduced using a potentiostatic polarization method at constant potentials in an equimolar NaCl-KCl melt containing AlF3 or YF3 at 1023 K. After the Al electrodeposition, homogenous deposit layers were formed on the TiAl and the stainless steel. The deposited layer formed on the TiAl consisted of TiAl3. The deposited layer formed on the stainless steel consisted of some Fe aluminides. The TiAl and the stainless steel covered by the electrodeposited layers were far more resistant than the bare TiAl and stainless steel to high temperature oxidation. The Y electrodeposition on the stainless steel induced the deposition of Y particles on the stainless steel. The cyclic-oxidation resistance of the electrodeposited stainless steel was remarkably improved as compared to the untreated stainless steel.
In Situ Growth-Stress Measurement of Cr2O3 Scale Formed on Stainless Steels by Raman Spectroscopy
Authors: Kitamura Kazuyuki , Nishiyama Yoshitaka , Otsuka Nobuo , Kudo T.
Published: March 2009

Raman spectroscopy was conducted to evaluate mechanical stress in growing α-Cr2O3 scale upon oxidation of austenitic 25mass%Cr-20mass%Ni and ferritic 17mass%Cr stainless steels at 1173 K in air for up to 24 h. Sintered α-Cr2O3 pellet was heated to 373-1173 K and examined in order to obtain the temperature dependence of the wave length of the major Raman peak. For 1.2 mm thick 25mass%Cr-20mass%Ni steel specimen, compressive growth stress was indicated for α-Cr2O3 scale right upon oxidation and the stress increased until oxidation for 3 h, but it saturated and remained constant thereafter. The growth stress of α-Cr2O3 scale was 0.7 ± 0.1 GPa at 1173 K. For 1.2 mm thick ferritic 17mass%Cr steel specimen, mechanical stress was compressive, but the saturated growth stress was around 0.2 GPa, considerably smaller than the “strong” 25mass%Cr-20mass%Ni steel specimen. For 0.1mm thick austenitic 25mass%Cr-20mass%Ni steel specimen, the test results were similar. These were attributed to the different high-temperature strength of the metal substrate. Hence, for high-temperature oxidation of thin foils and/or ferritic steels of which high-temperature strength of the metal substrate is relatively poor, stress relaxation of protective α-Cr2O3 scale can result and the growth stress of α-Cr2O3 scale may be lowered by the “weak” metal substrate. Raman spectroscopy can offer useful information on the mechanical stress of protective oxide scale even at high temperatures.
Effect of Alloying Elements on Corrosion Resistance of Ni-Base Cast Alloys in Waste Incineration Environments
Authors: Noguchi Manabu , Matsuoka Kei , Sakamoto Hideyuki , Ueta Shigeki , Sawada Yoshiyuki
Published: March 2009

After examining practical structural materials for use in the high-temperature environments
of waste incinerators, it was found that a Ni-Cr-W casting alloy is promising. However, the
corrosion reaches its peak in the vicinity of 900°C. This peak is related to the behavior of chlorides
that form in the interior of the alloy. As the chlorides continuously generate and decompose, the Cl
recycles, accelerating corrosion. It is thought that when the temperature rises, the chlorides vaporize
outside the alloy, suppressing Cl recycling and thus reducing the amount of corrosion. Adding Al to
the alloy generates highly volatile AlCl3, making it possible to prevent the accumulation of
chlorides in the vicinity of 900°C and lower the corrosion peak. As a result of conducting exposure
testing for a year at an actual incinerator, it was demonstrated that adding Al is an effective way to
improve corrosion resistance.
The Influence of Sulfur Additions on the Corrosive Environments in a Waste-Fired CFB Boiler
Authors: Pettersson J. , Pettersson C. , Folkeson Nicklas , Johansson Lars Gunnar , Skog Erik , Svensson Jan Erik
Published: March 2009

Corrosion/deposition field tests have been carried out in the superheater region of a commercial
waste-fired 75MW CFBC boiler using air cooled probes. The influence of material temperature
(450-500°C), flue gas temperature, temperature variations (i.e. thermal cycling) and additives to the
fuel (elemental sulphur and dolomite) on deposition and corrosion was studied. The results
presented here mainly consider the influence of sulphur additions to the fuel. The fuel was a
mixture of 50% household waste and 50% industrial waste. After exposure the samples were
analyzed by ESEM/EDX, XRD, AAS, FIB and IC. With no additional sulphur, alkali chlorides
made up a large part of the deposit/corrosion product layer and in some cases chromate (VI) was
detected. It is suggested that the chromate (VI) has formed by reaction of the protective oxide with
alkali chlorides in the deposit. Adding sulphur to the fuel changed the composition of the deposits,
alkali chlorides being largely replaced by alkali sulphates. No chromates(VI) were detected in the
sulphur-added runs. It is suggested that adding sulphur to the fuel may decrease fireside corrosion
because it changes the composition of the deposit. Alkali sulphates are much less corrosive than
alkali chlorides partly because they do not form chromate(VI).
An Overview of Metal Dusting in Synthesis Gas Environments
Authors: Szakàlos P.
Published: March 2009

This paper gives an overview of the different processes of metal dusting (MD) that operate on low and high alloyed iron and nickel base alloys exposed in CO+H2–containing environments with or without water vapour. MD of pure metals like iron and nickel occur with a solely carbon-induced corrosion mechanism. However, in high alloyed materials with strong oxide formers such as Cr and Al, a more complex MD-process takes place which involves both carbon and oxygen in close collaboration. The “alloyed” carbides, i.e normally Cr-containing carbides, formed in such materials are thermodynamically stable with respect to the carbon activity. However, in the reaction front of a MD-pit with non-protective spinel oxide, they destabilise and dissolve due to the influence of the low oxygen activity determined by CO-dissociation. Based on recent results in the field of MD a chart with tentative MD mechanisms is presented as a function of alloy composition and temperature.
Numerical Analysis and Control of Gas Carburizing under Changes in Gas Compositions
Authors: Yokoyama Yujiro , Mizukoshi Tomoyuji , Ishigami Itsuo , Usui Tateo
Published: March 2009

Low carbon steel, S15CK, was carburized at 1203K up to 12.93ks in a commercial furnace where
RX gas converted from propane was employed as carrier gas. Gas compositions in the furnace
were changed intentionally; consequently carbon potential changed from 0.8 to 1.2 mass%. The
carbon content profiles were determined by a succession of grindings and carbon analyses of the
ground surfaces with a vacuum type emission spectrometer. A mathematical model for calculation
of carbon content profiles is proposed to describe carburizing behavior under time-variant gas
compositions in a furnace. The calculated profiles were in good agreement with the experimental
ones except the surface and its vicinity. This result indicates that the present model can be applied
to gas carburizing in the furnace where gas compositions were changed.
Influence of the Third Element on the High Temperature Oxidation Behavior of γ'-Ni3Al Alloys
Authors: Mikuni Shinya , Hayashi Shigenari , Narita Toshio
Published: March 2009

The effects of the third element on the high temperature oxidation of γ'-Ni3Al with
5at%X (X=Ti, Ta, Nb, Cu, Co and Fe) alloys were investigated at 1173K in air, and oxidation
behavior could be classified into three groups. The first group, comprised of alloys with Cu and Co,
showed good oxidation performance with Al2O3 formation. A second group contains Ti, Ta, and Nb
as alloying elements, and showed poor oxidation performance. With Fe or Mn addition the alloy
oxidation performance was intermediate between the first and second group. The effects of these
elements are discussed associate with partitioning factors for each element in the γ'-phase.
Influence of Ion Implantation of Several Elements on Oxidation Behavior of TiAl
Authors: Yoshihara Michiko , Taniguchi Shigeji , Furumaki D. , Aono M.
Published: March 2009

TiAl-based alloys have attractive properties as light weight heat-resisting material. In the present work, the influence of Cu, Zn, Ag and Se on the oxidation behavior of TiAl was investigated by ion implantation at acceleration voltage of 50 kV and ion doses of 1019 to 2x1021 ions/m2. The oxidation behavior was assessed by a cyclic oxidation test at 1200 K in a flow of purified oxygen under atmospheric pressure. The oxidation products were analyzed by conventional methods including X-ray diffractometry, SEM and EPMA. The implantation of Zn and Cu improves the oxidation resistance significantly by forming virtually Al2O3 scales, while Ag and Se enhance the oxidation. The improvement by Zn is attributable to the formation of complex oxide of Zn in the initial stage of oxidation. The oxygen partial pressure under the layer seems to be very low, resulting in the formation of alumina scale due to a selective oxidation of Al. The influence of Cu is not certain. The influence of Ag and Se is explained in terms of Al depletion in the implanted layer.
Micro-Area Analysis of the Corrosion Products Formed on Alloy 825 Exposed to Simulated Waste Incineration Boiler Conditions
Authors: Sato Ayako , Takahashi Hideyuki , Yoshiba Masayuki
Published: March 2009

An analytical study of high-temperature corrosive failure in a waste incineration plant
was conducted using a new type EPMA equipped with a Schottky type field emission gun. For
sample preparation, a cross-section polisher that uses an argon ion beam was applied. Both the
element distribution through the alloy substrate to the scale and the chemical states of sub-micron
sized corrosion products were revealed, leading to inferences about the corrosion mechanism.
FibDAC - Residual Stress Determination by Combination of Focused Ion Beam Technique and Digital Image Correlation
Authors: Keller J. , Gollhardt A. , Vogel Dietmar , Auerswald E. , Sabate N. , Auersperg J. , Michel Bernd
Published: March 2009

New challenges for design, manufacturing and packaging of MEMS/NEMS arise from
the ongoing miniaturization process. Therefore there is a demand on detailed information on
thermo-mechanical material properties of the applied materials. Because of size effects and the
strong dependency of the thermo-mechanical behavior of active and passive components on process
parameters often unsolved questions of residual stresses lead to system failure due to crack
formation. With the fibDAC (Focused Ion Beam based Deformation Analysis by Correlation)
method which is presented in this paper the classical hole drilling method for stress release
measurement has been downscaled to the nanoscale. The ion beam of the FIB station is used as a
milling tool which causes the stress release at silicon microstructures of MEMS devices. The
analysis of the stress release is achieved by digital image correlation (DIC) applied to load state
SEM images captured in a cross beam equipment (combination of SEM and FIB). The results of the
DIC analysis are deformation fields which are transferred to stress solution by application of finite
element analysis. In another step the resolution of the method has been improved by the application
of trench milling instead of hole milling. Thereby deformation measurements in the nm range are
established. The method is also a powerful tool for the analysis of sub-grain stresses of engineering
materials.
A Heuristic Approach for Decision-Making on Assembly Systems for Mass Customization
Authors: Calvo R. , Domingo Rosario , Rubio Alvir E.M.
Published: March 2009

In an increasing competitive market where offer exceeds demand, developing customer value is nowadays a key driver of industrial activities. Reducing costs, increasing quality, deliver on time and the introduction of the right product quickly are unavoidable elements to succeed. A higher product variety for mass production and short lead-time are main features of mass customization. Flexibility arises as a productive and competitive factor to face it, of particular interest in assembly systems, which allow the postponement of final variety, integrating all former tasks of the supply chain. In this scenario, flexibility helps to face uncertainty in decision-making, while the increase of system complexity requires extra control and management efforts. Both flexibility and complexity are briefly reviewed. Next, it is introduced a joint analysis of flexibility and complexity useful for decision-making. Both are linked to the uncertainty of the possible states of the system and a quantitative approach of general application is presented. Finally, based on a model simulation, a first case application illustrates product variety increase in an assembly system and some decisionmaking trade-offs.
Fixture Design Process Automation for Coordinate Measuring Machines: A Knowledge-Based Approach
Authors: Perez J. , Hunter R. , Hernandez J.C. , Idoipe Antonio Vizan
Published: March 2009

Nowadays, the inspection process is an essential part of the manufacturing process, where a
product is subjected to verification of the geometric features, dimensions and tolerance
specifications with respect to the product design specifications. One of the most interesting topics in
the automation of the inspection process is the right fixture design. In the fixture design process we
have used the information provided by the part design and manufacturing process. However, the
lack of integration and structuring of this information results in one of the most important problems,
producing an increase in the time and cost implied in the development of the fixture design and its
implementation.
For this reason, this work presents a knowledge model for the inspection fixture design process
for a Coordinate Measuring Machine (CMM), which allows the automation of the inspection fixture
design process to be made easier, reducing time and cost associated to the inspection process and to
the manufacturing process in general.
Manufacturing Processes Analysis by Virtual Reality
Authors: Sanz Alfredo , Rubio Alvir E.M. , Martínez Murillo Carmen , Sebastián M.A.
Published: March 2009

Present work shows many of Virtual Reality (RV) developments carried out in
manufacturing processes field by the collaboration between Aerospace Materials and Production
Department at the UPM University and Manufacturing and Construction Engineering at the UNED
university. Most of them have been directed towards Numerical Control Machine Tools field and
towards equipment that configure automated manufacturing systems like Flexible Manufacturing
Systems (FMS).
The Combined Effect of Modifier and Grain Refiner AlTiBSr Master Alloy on Microstructure and Porosity of Aluminum Alloys
Authors: Moldovan Petru , Popescu Gabriela , Cuhutencu Marilena
Published: March 2009

The aim of the paper is to present the influence of a new multifunctional material, a
master alloy named Al-Sr-Ti-B, in aluminum foundry alloys. The Al-Sr-Ti-B master alloy
represents a new combination of two master alloys, already known in aluminum industry, AlTiB
and AlSr, used in treatment of aluminum alloys for grain refining and modification. As Strobloy,
our master alloy contain fast dissolving SrAl4 particles and also nucleating particles as TiB2 and
(Al,Ti)B2 which are important first in modification and second in grain refining of aluminum alloys.
The paper presents optic and electron microscopy studies realized on AlSi7Mg alloy treated with
this new multifunctional material
Thermal Analysis of Honing Process
Authors: González-Rojas Hernan A. , Vivancos Calvet Joan , Coba Salcedo Milton
Published: March 2009

The objective of this work is to develop thermal simulation software of the honing process applied to metallic cylinders. The proposed thermal model is based on the action of heat impulses generated by the abrasive bars that are in contact with the cylinder internal surface. A onedimensional heat diffusion equation, with variable properties and solved by the finite difference method, is the fundamental part of the mathematical model. The model is implemented in friendly software, which allows to study, for example, the influence of the convective cooling effect on the temperature range in the internal cylinder wall, as well as the dependence of the temperature of nonlinear thermal properties. The software outputs are the temperature distributions in space and time, which are represented on automatically generated graphs. It has been possible to verify the correct operation of the simulator contrasting it with experimental data.
Design of a Computer Vision System to Estimate Tool Wearing
Authors: Alegre E. , Barreiro Joaquín , Cáceres H. , Hernández L.K. , Fernández R.A. , Castejón M.
Published: March 2009

Wear level of tool inserts in automated processes is tried using techniques of artificial
vision. An application has been developed in Matlab that allows the acquisition of images with
different resolutions and later on to process them. It is explained how the vision system used has
been designed and implemented. The method for acquiring tool insert images and their treatment in
the pre-processing, segmentation and post-processing is commented. First results are also presented
using diverse texture descriptors. These first results must be corroborated carrying out new
experiments with a bigger number of images.
Sintering of a Gamma Ti-Al Alloy
Authors: Henriques Vinicius André Rodrigues , Cairo Carlos Alberto Alves , Almeida D.S. , de Alencastro Graça Mario Lima
Published: March 2009

Gamma-TiAl alloys are potential replacements for nickel alloys and conventional
titanium alloys in the cooler sections of turbine engines, as well as in orbital platform vehicles. The
combination of high specific stiffness and good oxidation resistance at intermediate temperatures
can provide significant weight savings. However, they have a limited plasticity at room temperature
and the tendency to brittle fracture. Powder metallurgy is a near net shape process that allows the
parts production with complex geometry at low costs. An improved plasticity of the Ti-Al alloys is
received by adding alloying elements and by microstructure modification. An alloy of two-phase
structure Ti–48Al–2Cr–2Nb (at.%) was investigated using the blended elemental technique.
Samples were produced by mixing of initial metallic powders followed by uniaxial and cold
isostatic pressing with subsequent densification by sintering at 1500 °C, in vacuum. It was shown
that the samples presented a two-phase structure consisting of lamellar colonies of alternating layers
of gamma and α2 phase.