bluuebunny/crossref_metadata_2025 huggingface dataset:
Development and Improvement of 9-12%Cr Steels by a Holistic R&D Concept
Authors: Cerjak Horst , Dimmler Gerhard , Holzer Ivan , Kozeschnik Ernst , Mayr Peter , Pein Cornelia , Sonderegger Bernhard
Published: March 2009

The research activities on ferritic / martensitic 9-12% Cr steels at the Institute of
Materials Science, Welding and Forming (IWS) are represented by a network of interacting projects
focusing on mechanical properties of base and weld metal, microstructural characterisation of creep
and damage kinetics, weldability, microstructure analysis in the course of creep, modelling of
precipitation and coarsening kinetics, simulation of complex heat treatments and the deformation
behaviour under creep loading. The individual projects are briefly described and the conceptual
approach towards a quantitative description of the creep behaviour of 9-12% Cr steels is outlined.
Interaction of Recrystallization and Precipitation during Hot Forming of Alloy 80A
Authors: Sommitsch Christof , Poelt Peter , Rüf Guntram , Mitsche Stefan , Albu Mihaela
Published: March 2009

In the high temperature deformation window of the nickel base Alloy 80A the lower
temperature region during open die forging was examined with regard to the materials formability.
For that purpose, hot compression samples were investigated by means of EBSD and TEM in order
to look at recrystallization, precipitations and ductile damage as well as their reciprocal effects.
Further a microstructure model was used, which calculates the materials strengthening, softening
and the particle kinetics. A micro mechanical damage model of the effective stresses was coupled
with the grain structure development in order to describe a retarded damage rate due to the ongoing
recrystallization.
Improvement in Creep Strength of Heat-Resistant Ferritic Steel Precipitation-Strengthened by Intermetallic Compound
Authors: Toda Yoshiaki , Kushima Hideaki , Kimura Kazuhiro , Abe Fujio
Published: March 2009

The effects of nickel content and heat treatment conditions on the creep strength of
precipitation-strengthened 15Cr ferritic steel were investigated. The creep strength of the 15Cr ferritic
steel was drastically improved by solution treatment and water quenching. However, over the long
term, the detrimental effect of nickel on the creep strength was pronounced for water-quenched steels.
The volume fraction of martensite phase increased with increased nickel content in both the
furnace-cooled and water-quenched steels. The volume fraction of martensite phase in the
water-quenched steel was smaller than that in the furnace-cooled type, even for the same nickel
content. Fine particles, smaller than 500 nm, were precipitated homogeneously within the ferrite
phase of the water-quenched steel. On the other hand, coarse block-like particles 1 $m in size were
precipitated sparsely within the martensite phase. The creep strength of the steels decreased with
increased volume fraction of the martensite phase caused by furnace cooling and nickel addition. The
lower creep strength and microstructural stability of the martensite phase is attributable to less
precipitation strengthening. To enable this steel to be put to practical use, it will be necessary to
suppress the formation of the martensite phase caused by addition of nickel by optimizing the
chemical composition and heat treatment conditions.
On Bainite Transformation Kinetics and Mechanism
Authors: Zhao Si Xin , Wang Wei , Mao Da Li
Published: March 2009

The platelike bainitic ferrite growth rates were calculated by two modified diffusional
models. Good agreements between experimental and theoretical results are found in Fe-0.59C wt.%,
Fe-0.81C wt.% and Fe-0.478C-4.87Ni wt.% alloys. A slowing down effect due to the alloying
element Mo is emphasized in Fe-0.69C-1.8Ni-0.8Mo wt.% alloy. However, the experimental data
are lower than theoretical ones about two orders in Fe-C-8.7Ni wt.% alloys. According to the
discussion of the results, it is suggested that the bainite transformation mechanism may relates to
steel composition and transformation temperature.
Some Behaviors of Phosphorus in Several Typical Superalloys
Authors: Sun Wen Ru , Yang S.L. , Wei Z.G. , Guo Shou Ren , Hu Zhuang Qi
Published: March 2009

The effect of phosphorus in some typical wrought superalloys including IN718, GH761
and GH4133 has been studied. Phosphorus was not dissolved in the γ matrix of superalloys and was
segregated in the residual liquids seriously during solidification, and the solidification of the alloys
added with phosphorus was always finished by the precipitation of a phosphorus bearing phase.
Two factors controlling the segregation tendency of a minor element were determined, one is the
solubility of the element in the matrix, another is the precipitation temperature of a phase in which
the element is absorbed. The detrimental effect of phosphorus on the solidification could be
eliminated by a proper homogenization treatment. Phosphorus improved the stress rupture
properties of the alloys with a fine grain structure. By combining the grain refinement with
phosphorus addition, the properties of GH761 alloy was improved efficiently.
Time Dependence of γ/γ' Lattice Mismatch in Creep-Deformed Single Crystal Superalloy SC16 at 1173 K
Authors: Schumacher G. , Darowski N. , Zizak I. , Klingelhöffer Hellmuth , Chen W. , Neumann Wolfgang
Published: March 2009

The profiles of 001 and 002 reflections have been measured at 1173 K as a function
of time by means of X-ray diffraction (XRD) on tensile-creep deformed specimens of single
crystal superalloy SC16. Decrease in line width (full width at half maximum: FWHM) by
about 7 % and increase in peak position by about 3x10-4 degrees was detected after 8.5x104 s.
Broadening of the 002 peak profile indicated a more negative value of the lattice misfit after
the same time period. The results are discussed in the context of the anisotropic arrangement
of dislocations at the γ/γ’ interfaces during creep and their rearrangement during the thermal
treatment at 1173 K.
Effect of Aging on Microstructure and Martensitic Transformation in Ti-Zr-Ni Shape Memory Alloys
Authors: Sandu Adrian , Tsuchiya Koichi , Yamamoto Shinya , Tabuchi Masayuki , Todaka Yoshikazu , Umemoto Minoru
Published: March 2009

Effect of isothermal aging on martensitic transformation temperatures, mechanical
properties and microstructure was investigated for a Ni-rich Ti-Zr-Ni shape memory alloy at
temperatures ranging from 673 K to 773 K. The aging behaviour was two stage process: the first stage
associated with an increase in the Vickers hardness and a decrease in martensitic transformation
temperatures and the second stage with a decrease in the hardness and increase in the transformation
temperatures. Second stage was also characterized by the appearance of nano-scale precipitates,
which has never been reported.
Functionally Graded Ti-Ni Shape Memory Alloys
Authors: Nam Tae Hyun , Yu Cheol Am , Lee Yun Jung , Liu Yinong
Published: March 2009

Shape memory characteristics and superelasticity of an temperature gradient
annealing(TGA) treated equiatomic Ti-Ni alloy have been investigated by means of differential
scanning calorimetry(DSC), thermal cycling tests under constant load and tensile tests. By
annealing 25% cold worked alloy under the temperature gradient from 658 K to 466 K, 7 K
variation in TR*and 19 K variation in Ms* were obtained along the length of sample(150mm).
Temperature dependence of transformation elongation(dε/dT) of TGA treated Ti-Ni alloy wires was
in the range of 0.05 %/K and 0.01 %/K depending on annealing temperature ranges. The dε/dT
obtained from TGA treated sample under the temperature gradient from 658 K to 466 K was
0.03 %/K. TGA treated alloy showed the clear superelastic recovery.
The Effect of Electromagnetic Vibration on the Structure Control of A356 Alloy
Authors: Choi Jung Pyung , Nam Tae Woon , Yoon Eui Pak
Published: March 2009

The structural control of A356 alloy, which was not studied among various
electromagnetic processing of materials, was considered applying the alternating current and direct
current magnetic flux density. The main aim of the present study is to investigate the effects of
electromagnetic vibration on the macro and microstructure of A356 alloy in order to develop a new
process of structural control in A356 alloy. When the electromagnetic vibration is conducted for
changing the shape of primary aluminum, at low frequency (≤60Hz), the shape of dendrite is changed
speroidal shape. When the electromagnetic vibration is conducted for changing the shape of eutectic
silicon, a morphological change of the eutectic silicon from coarse platelet flakes to fine fiber shape is
observed with EMV (Electro Magnetic Vibration) process at high frequency (≥500Hz).
Shape Memory Characteristics of Ti-Ni Alloy Using Mechanically-Alloyed Powder
Authors: Terayama Akira , Kyogoku H. , Komatsu S.
Published: March 2009

In this research, we investigated the fabrication conditions of Ti-Ni alloy powder by MA
process and the shape memory characteristics of the sintered alloy by a pulse-current sintering
equipment using mechanically alloyed powder (MA powder). The microstructure of the sintered
alloy of the MA powder was more homogeneous than that of the alloy of the elemental powders.
The application of the MA powder makes the width between transformation temperatures of the
shape memory treated alloy of the MA powder became narrower, that is, it improves the
temperature response of the compact. The tensile strength and elongation of the shape memory
compact of the MA powder were approximately 780 MPa and 7.5 %, respectively. This is one of
the superior tensile properties of SMA compact fabricated by powder metallurgy process. The
superelastic behavior took place in the alloy of the MA powder. Thus, the MA process in short
process time resulted in lower contamination of the MA powder and the application of the MA
powder resulted in superior shape memory characteristics of the sintered alloy.
On the Effect of Texture in Experimental Grades of High-Silicon Electrical Steel
Authors: Houbaert Yvan , Ros-Yáñez Tanya , Rodriguez-Calvillo Pablo , Barros José , Kestens Leo A.I.
Published: March 2009

Crystallographic texture has an important effect on the magnetic quality of electrical steel: a specific
texture parameter A is defined and used to estimate the magnetic quality of texture components. It is
shown that obtaining the best possible texture in non oriented electrical steel can reduce the losses
with 1,5 W/kg. Two production schemes for high silicon electrical steel are described: a
conventional processing through hot and cold rolling with adequate temperatures and cooling rates
and an immersion-diffusion process by hot dipping in a Si- and Al-rich bath followed by diffusion
annealing. The texture evolution in these experimental materials is under study and first results are
reported for conventional alloys (rolling procedure) and for immersion-diffusion alloys, which are
annealed after dipping in order to obtain a controlled concentration gradient with high Si and/or Al at
the surface or a homogeneous Si and/or Al-content over the thickness.
Sputtered Cu Films Containing Various Insoluble Substances for Advanced Barrierless Metallization
Authors: Chu J.P. , Lin C.H.
Published: March 2009

Sputtered Cu films containing various insoluble substances, such as Cu(W2.3), Cu(Mo2.0),
Cu(Nb0.4), Cu(C2.1) and Cu(W0.4C0.7), are examined in this study. These films are prepared by
magnetron sputtering, followed by thermal annealing. The crystal structure, microstructure, SIMS
depth-profiles, leakage current, and resistivity of the films are investigated. Good thermal stability
of these Cu films is confirmed with focused ion beam, X-ray diffractometry, SIMS, and electrical
property measurements. After annealing at 400°C, obvious drops in resistivity, to ~3.8 μ-cm, are
seen for Cu(W) film, which is lower than the other films. An evaluation of the leakage current
characteristic from the SiO2/Si metal-oxide-semiconductor (MOS) structure also demonstrates that
Cu with dilute tungsten is more stable than the other films studied. These results further indicate
that the Cu(W) film has more thermal stability than the Cu(Mo), Cu(Nb), Cu(C), Cu(WC) and pure
Cu films. Therefore, the film is suitable for the future barrierless metallization.
The Role of Segregation in InGaAs Heteroepitaxy
Authors: Litvinov D. , Gerthsen D. , Rosenauer A. , Schowalter M. , Passow Thorsten , Hetterich Michael
Published: March 2009

We investigated InGaAs layers grown by molecular-beam epitaxy on GaAs (001) with
transmission electron microscopy (TEM) and photoluminescence spectroscopy. InGaAs layers with
In-concentrations of 16, 25 and 28 % and respective thicknesses of 20, 22 and 23 monolayers were
deposited at 535 °C. Island formation is observed for the layer with the highest In-concentration. Inconcentration
profiles were obtained from high-resolution TEM images by composition evaluation
by lattice fringe analysis. The measured profiles can well be fitted applying the segregation model of
Muraki et al. [Appl. Phys. Lett. 61 (1992) 557] and are in excellent quantitative agreement with the
photoluminescence peak positions. From our data we conclude that island formation occurs when
the amount of Indium in the In-floating layer reaches 1.1±0.2 monolayers indium.
In Situ Scanning Electron Microscopy Observation of the Pattern Formation on the Surface of Al/Ge Bilayer Films
Authors: Kumagai H. , Shibata M. , Moritani Tomokazu , Kozakai Takao , Doi Minoru , Takagi Makoto , Imura Toru
Published: March 2009

When the Al/Ge/SiO2 bilayer films are annealed in-situ in a scanning electron microscope
(SEM) at the temperatures lower than the crystallization temperature of amorphous Ge itself, the
so-called metal-mediated-crystallization (MMC) takes place. In the course of MMC, crystalline Ge
aggregates (Ge clusters) form in the bilayer films, which results in the formation and the evolution of
impressive fractal patterns with branching on the free surface. In-situ SEM observations of annealed
Al/Ge/SiO2 bilayer films indicate that the grain size of polycrystalline Al-layer influences the
nucleation of Ge clusters and hence of fractal patterns. For the bilayer films containing larger Al
grains, the nucleation rate of fractal patterns (Ge clusters) is faster and the number of patterns is larger.
Effect of Surface Oxide Films on Degradation of Titanium
Authors: Asaoka Kenzo , Maejima Kunimitsu
Published: March 2009

Thermal desorption spectroscopy (TDS) was applied to measure the hydrogen in titanium
(Ti). Because fracture by hydrogen embrittlement for medical/dental devices of Ti and Ti alloys
was reported, dependence of surface oxidation film on hydrogen absorption and desorption
behaviors of cp-Ti was carried out. To form the surface oxide film (rutile), the Ti wire samples were
annealed in an ambient air at 800oC for 2 hours. Half of the specimens were immersed in a mixed
solution of NaF and H3PO4 (APF). The part of the specimens were removed the surface films by
abrasion after the heat and the immersion in the APF solution. TDS analysis was applied to detect
released ions/molecules during heating from room temperature to 1200oC in a high vacuum vessel
for the TiH2 powders, the Ti samples with and without the above treatments. High ion intensity was
detected for hydrogen (m/z = 2), and ion intensities of the other ions/molecules were almost the
background level in measurements. The concentration of hydrogen in the samples related with heat
and chemical process was determined quantitatively, and was not significantly increased by the
annealing and the immersion in APF solution if the sample had the tough surface film. However,
the sample, which had been removed the surface films before the immersion in APF, showed
typical chemical degradation after the immersion in APF for 7 days, that is, high ion intensities of
hydrogen, fluoride, water and hydroxyl ions were detected. It was concluded that the control of the
surface oxide film on the medical/dental Ti devices is important in determining its longevity.
Optimization of the Equal Channel Angular Pressing (ECAP) Process for Strain Homogeneity
Authors: Cherukuri B. , Srinivasan R.
Published: March 2009

Two-Dimensional finite element analysis was carried out to optimize the equal channel
angular pressing process (ECAP) for strain homogeneity under frictionless and frictional conditions.
The effect of outside corner angle (Ψ), inner radius (r) and shear friction (m) on the strain
homogeneity was investigated. The strain homogeneity can be increased by correcting the outside
corner to eliminate the corner gap between the sample and the die at the expense of average strain.
Small inside radius and outside corner radius would provide large deformations without much loss
in the strain homogeneity under frictionless conditions. The work piece deformation is by bending if
the inner radius exceeds a critical value. No improvement in strain homogeneity was observed
under frictional conditions.
A Physically Based Flow Rule for the Simulation of Ti-6Al-4V Forging in the α - β Range
Authors: Colin A. , Desrayaud Christophe , Mineur Marie , Montheillet Frank
Published: March 2009

The aim of this work is to study the flow instabilities occurring during hot forging of
titanium alloy blades. In this view, the viscoplastic deformation behaviour of Ti-6Al-4V alloy is
investigated by means of torsion tests under isothermal hot working conditions at temperatures
ranging from 800 to 1020 °C and strain rates of 0.01, 0.1 and 1s−1. The thermomechanical
processing is performed up to a true strain of 10.
The flow stress data are analysed in terms of strain rate and temperature sensitivities. A
constitutive equation that relates not only the dependence of the flow stress on strain, strain rate
and temperature, but also for the fraction of each phase α and β is proposed. Two mechanical
models are compared : the uniform strain rate model (Taylor) and the uniform plastic energy
model (IsoW). The usual strain rate sensitivity and activation energy values of Ti-6Al-4V alloy
are obtained by fitting the experimental data. Furthermore, specific values of strain rate
sensitivities and activation energies are calculated for the α and β phases providing thus a
constitutive law based on the physics of the α / β phase diagram. The flow stress is then related
to strain by an empirical equation taking into account the flow softening observed after a true
strain of 0.5 and the steady state flow reached after a true strain of 4. Comparison of the
calculated and measured flow stresses shows that the constitutive equation predicts the
experimental results with a reasonable accuracy.
The above constitutive equation is then used for simulating forging processes by the finite
element method. The calculations exhibit the localisation of deformation produced by shearing
effects in the form of the classical X shape.
On the Nature of the Growth of Bainitic α plates in Metastable β Ti Alloys
Authors: van Bohemen S.M.C. , Sietsma Jilt , van der Zwaag Sybrand
Published: March 2009

The growth mechanism of bainitic α plates in Ti-4.5Fe-6.8Mo-1.5Al, a metastable β Ti
alloy, has been investigated by optical microscopy, electron probe microanalysis (EPMA) and
dilatometry. The observations are compared with the transformation characteristics of primary α
plates, which form at relatively high temperatures. The primary α plates form predominantly on β
grain boundaries, whereas the bainitic α plates nucleate both at grain boundaries and
intragranularly. It is shown that the morphological transition with decreasing temperature is
associated with a change in transformation mechanism. The EPMA results show that the primary α
plates are formed by a partitioning transformation. In contrast, the growth of the bainitic α plates is
partitionless, followed by a post-transformation redistribution of Fe. This mechanism is similar to
bainite in steel. The Fe diffusion from the supersaturated bainitic α plates to the β matrix causes the
observed dilatation signal. The results of dilatometry in conjunction with optical microscopy
indicate that a low misfit between the lattice structures exists, which is favourable for a partitionless
transformation to occur at a low undercooling below T0.
Microstructure and Mechanical Properties of an Advanced Niobium Based Ultrahigh Temperature Alloy
Authors: Guo X.P. , Gao L.M. , Guan Ping , Kusabiraki K. , Fu Heng Zhi
Published: March 2009

The microstructure and mechanical properties including room temperature fracture
toughness Kq, tensile strengthσb and elongationδ at 1250°C of the Nb based alloy directionally
solidified in an electron beam floating zone melting (EBFZM) furnace have been evaluated. The
microstructure is primarily composed of Nb solid solution (Nbss), α-(Nb)5Si3 and (Nb)3Si phases.
After directional solidification with the moving rate of electron beam gun R being respectively 2.4,
4.8 and 7.2 mm/min, the primary Nbss dendrites, Nbss + (Nb)5Si3/(Nb)3Si eutectic colonies
(lamellar or rod-like) and divorced Nb silicide plates align along the longitudinal axes of the
specimens. When R = 2.4 mm/min, the best directional microstructure is obtained. Directional
solidification has significantly improved theσb at 1250°C and Kq. The maximumσb occurs for the
specimens with R = 2.4 mm/min and is about 85.0 MPa, meanwhile, the Kq is about 19.4 MPam1/2.
Microstructural Evolution of Cast Mg-Al-Ca Alloy during Friction Stir Processing
Authors: Zhang Da Tong , Suzuki Mayumi , Maruyama Kouichi
Published: March 2009

A thixomoulded magnesium alloy containing thermally stable Al2Ca phase was friction
stir processed, and its microstructure and mechanical property were investigated. In friction stir
zone, the cast structure of the base metal is replaced by fine magnesium grains containing fine
dispersoides of Al2Ca. Due to the refined grain size of 0.8-1 μm, hardness of friction stir zone is
higher than that of base metal. Texture was developed at top and bottom surfaces, (0002) being
parallel to the plate surface, whereas (0001) plane is randomly oriented in the center of friction stir
zone.
Experimental Thermal Analysis of Friction Stir Processing
Authors: Darras Bassil M. , Omar M.A. , Khraisheh Marwan K.
Published: March 2009

Despite the large number of studies that are being conducted to advance the friction stir
processing (FSP) technology, the effects of FSP on various mechanical and microstructural
properties are still in need for further investigations. In addition, correlations between FSP
parameters, mechanical properties and microstructural characteristics are not yet well understood.
Accurate correlations are needed for successful modeling and process optimization. It is established
that the temperature generated during FSP plays an important role in determining the microstructure
and properties of the processed sheet and defining the tool life. Process parameters must be
carefully chosen to allow the generation of enough heat to soften the material while limiting
significant grain growth. Accurate measurement of the temperature distributions during processing
are essential to understand the complicated deformation and associated mechanisms and to allow
for effective process optimization. In this work, a dual-band thermography approach is used to
measure the temperature distributions of AA5052 sheet during FSP. The setup utilizes two infrared
detectors, to neutralize the emissivity and the facial effects, with 30 Hz acquisition rate. The
variation of temperature with process parameters and their correlation to the resulting
microstructure are discussed.
A Thermo-Fluid Analysis of the Friction Stir Welding Process
Authors: Jacquin D. , Desrayaud Christophe , Montheillet Frank
Published: March 2009

The thermo-mechanical simulation of Friction Stir Welding focuses the interest of the
welding scientific and technical community. However, literature reporting material flow modeling
is rather poor. The present work is based on the model developed by Heurtier [2004] and aims at
improving this thermo-fluid simulation developed by means of fluid mechanics numerical and
analytical velocity fields combined together. These various velocity fields are investigated
separately and especially according to the power dissipated during the flow. Boundary conditions
are considered through a new approach based on the kinematic analysis of the thread of the pin. An
equilibrium is established between the vertical motion of the bulk material dragged in the depth of
the metal sheet, and its partial circulation around the pin. The analyses of the obtained velocity
fields enable the understanding of the welded zone asymmetry and highlights the bulk material
mixing between the welded coupons in the depth of the sheet. A regression is performed on the
relative sliding velocity of the aluminium according to the surface of the tool: shoulder and pin.
Two dimension flow lines in the depth of the metal sheet are then obtained and successfully
compared with the results obtained by Colegrove (2004) [1].
Modeling of Molten Drop Oscillation in Gas Shielded Metal Arc Welding
Authors: Hirata Yoshinori , Tsujimura K. , Yudodibroto B.Y.B. , Hermans M.J.M. , Richardson I.M.
Published: March 2009

In Gas shielded Metal Arc Welding process, the molten drop at the electrode wire tip is
detached and transferred into the weld pool by various driving forces, which have been discussed
mainly focusing on gravity force, electro-magnetic force, surface tension force and plasma drag
force. In this paper the oscillation phenomena of metal drop and their numerical model are
described. The numerical model developed is an axial symmetrical 2D model which enables to
calculate and visualize time-change of the drop shape and the flow in the drop using VOF-CSF
method. The validity of the model is verified through the comparison between calculations and
experiments using waterdrop. It is shown that the natural frequency of the pendant drop decreases
with increase of the drop size. And the numerical simulation predicts that it is possible to detach
the molten drop from the electrode wire by exciting the forced oscillation around the natural
frequency with pulsed current.
Electron Beam Welding of Crack Sensitive Nickel Super Alloy MAR-M-002
Authors: Mitchell Tim P. , Sanderson Ruth , Dance Bruce G.I.
Published: March 2009

There is an ongoing drive to reduce the operating costs of aero-engines and this may be
achieved partially via an increase in engine efficiency. To achieve this, industry needs to utilise new
materials that can withstand higher operating temperatures and stresses. Many of the nickel-based
alloys suitable for these applications, eg MAR-M-002, are difficult to join using conventional
welding techniques. This paper describes a technique used to successfully weld 2.5 mm thick plates
of cast MAR-M-002. The technique used FEA modelling to analyse stresses during welding and
multiple axis electron beam deflection to alter the temperature and stress distribution around the
fusion zone to prevent the initiation or propagation of cracks. FEA modelling of the process has
been used to reduce the total number of practical tests, and hence, to conserve the limited material
supply. This technique has made it possible to produce crack free welds in what is usually classed
as an 'impossible to weld' alloy.
Laser Hybrid Welding in Stainless Steels and in High Strength Steels
Authors: Stridh Lars Erik
Published: March 2009

Laser welding is a well known process, so is GMAW. But the joining of the processes,
the so called laser hybrid welding is not that known, yet. Looking into the laser welding we realise,
after many years use that there are some limitations to the process. One of the most significant is
that the process deals poorly with the ability to bridge gaps between plates that are to be joined.
This has its drawbacks on welding economy, the tolerances on ingoing parts has to be very high, the
laser process can not tolerate more than 0,1 mm gap between the plates. The GMAW process on the
other hand has the ability to deal with the joint tolerances in a better way, the backside is of course
the productivity and the penetration properties. In the laser hybrid process where the two processes
are joined in the same welding head, we are experienceing a great improvement in several
properties. Gaps are no longer a big problem, the process can deal with gaps up to 2,0 mm with the
present technology, (it is possible to coop with larger gaps using an oscillation of the laser beam,
but this is only on experimental stage yet). This now means that costs for ingoing parts will be
reduced. Process stability at high welding speeds is acchived.
There are many advantages in high strenght steels that are sensitive to heat input; better mechanical
properties are possible to obtain. Looking at the stainless materials the process has many
advantages, one of the most important is the joint volume reduction in thicker materials, another is
the ability to weld in duplex stainless steels.
Modeling of Steel Weld Microstructure Using Monte Carlo and Finite Difference Hybrid Method
Authors: Koseki Toshihiko , Araki Toshio
Published: March 2009

Monte Carlo (MC) and finite difference (FD) hybrid method is applied to numerically
model the growth of austenite grains caused by welding thermal cycle in the heat affected zone
(HAZ) of steel welds. The grain growth behaviors and pinning effects by dispersed particles are
modeled by MC method while steep changes in temperatures with time and over space are by FD
method. The connection of the two methods is made possible by correlating MC step to the real
time through the grain growth theory. The model results are in a good agreement with experiments
as well as previous experimental results published, and it is indicated that the developed model can
be used to obtain a better understanding of the austenite grain structure development in HAZ and
even to improve the grain refinement technology using dispersed particles.
Microstructure of Brazing Joint of Silicon Nitride / 40CrMo Steel
Authors: Zhang Jie , Zhu Lin Bin , Zhang Bao You , Yang Shi Wei
Published: March 2009

Si3N4 and 40CrMo steel was joined using Ag-Cu-Ti-Pd brazing filler. Microstructure of
the joint and bonding interface was studied by SEM and EDS, and the phase structure was analyzed
by XRD. The results indicate that reaction layers at ceramic/ filler alloy and filler alloy/steel
interfaces are formed. There is a reaction layer containing TiN and Ti5Si3 between ceramic and filler
alloy, while the reaction layer between filler alloy and steel is composed of Fe-Ti compound. The
middle part of the joint is an eutectic structure composed of Ag-riched and Cu-riched solid solutions.
With the increase of the brazing temperature, the thickness of the joint seem decrease, the thickness of
the reaction layer between Si3N4 and filler alloy increases and then decreases, and the thickness of
the reaction layer between filler alloy and steel increases.
Evaluation of Physical Parameters in Modelling Softening-Precipitation Interaction in Hot Worked Nb Microalloyed Austenite
Authors: Iparraguirre C. , Fernández-Calvo Ana Isabel , Rodriguez-Ibabe J.M. , López Beatriz
Published: March 2009

The interaction between softening and precipitation mechanisms in hot worked Nb
microalloyed austenite is analysed with the help of a physically based model. The model is able to
calculate the evolution over time of the dislocation density (stress), stored energy and precipitate
pinning force, the recrystallized fraction, the average precipitate diameter and precipitate number
density, as well as the concentrations of the precipitating Nb over time. It is assumed that nucleation
of precipitates occurs heterogeneously at dislocations with recovery producing a continuous
decrease in dislocation density. This results in a reduction of the available nucleation sites for
precipitation as well as a decrease in the driving force for recrystallization along time. By
comparing the model predictions and the experimental results the values of several physical
parameters involved in the model are discussed.
Deformation Banding and the Role of Transition Bands between α-Fibre Components on Recrystallization in Low Carbon Steels Studied by EBSD
Authors: Díaz-Fuentes M. , Iza-Mendia Amaia , Gutiérrez Isabel
Published: March 2009

In extra-low carbon steels, the generation of specific nucleation sites in the deformed
microstructure determines the formation of an optimum recrystallization texture. In particular,
during the cold rolling of the steel sheets, transition bands are generated in order to accommodate
the different deformation paths followed by the deformation bands (DB-s) within the grains. -fibre
grains (ND-fibre grains) are, in general terms, more fragmented than -fibre grains (RD-fibre
grains). Consequently, the higher orientation gradients and stored energy levels of the -fibre grains
determine the ND-fibre annealing texture. Nevertheless, during recrystallization of the ELC steel,
nucleation in different type of transition bands (TB-s) between α-fibre components has also been
observed in the present work. From a previous crystallographic classification of transition bands
done by the authors, the effect of the lattice curvature, either by gradual or sharp orientation
gradients, is studied during early recrystallisation stages.
Specifically, the crystallographic characteristics of recrystallized nuclei formed at transition bands
generated between α-fibre components are analyzed using electron back-scatter diffraction (EBSD).
This technique enables the orientation of deformation bands, the misorientation across them, the
orientation of the new recrystallized grains and the misorientation of those grains with the adjacent
matrix grains to be determined. Recrystallization of components different to α at the expense of α
components has also been found.
Microstructural Development in Bearing Steel during Rolling Contact Fatigue
Authors: Mitamura N. , Hidaka H. , Takaki Setsuo
Published: March 2009

It is well known that microstructural changes occur in a steel bearing, when the bearing is
operated under conditions involving high cyclic stresses. When combined with relatively high
temperatures, such microstructural changes result in the flaking of the bearing raceway. In this paper,
microstructural changes that occurred during rolling contact fatigue were investigated, and the
relationship between these changes and fatigue life are discussed in association with the
recrystallization behavior of martensite. Conventional bearing steel SUJ2 (SAE52100) was
subjected to partial solution treatment at 1133K for 2.4ks followed by oil quenching. The quenched
material with a martensitic structure was tempered at 443K for 7.2ks, and then subjected to rolling
contact fatigue testing. The testing was performed at temperatures ranging from 373K to 443K
and surface pressures of 4.6GPa or 5.5GPa. During testing at 373K, flaking occurred from the
surface of the raceway due to non-metallic inclusion and without any marked microstructural
changes. On the other hand, in the case of testing at 403K or more, flaking occurs after obvious
microstructural changes. Firstly, dark etching constituent (DEC) formed around the area of
maximum shear stress, which was followed by the formation of white etching constituent (WEC)
within the DEC at 80 and 30 degrees to the rolling direction. TEM observations showed the change
from martensite lath to dislocation cell structure within the DEC, and also the existence of fine
ferrite grains of 20nm through 100nm within the WEC. Arrhenius plots for the fatigue life indicated
that the activation energy of the fatigue process corresponded to that of carbon diffusion in bcc
ferrite. These results suggest that rolling contact fatigue originated from the WEC is controlled by
the diffusion of carbon in the ferrite matrix.
Ultrasonic Leak Test for Automotive Brake Caliper
Authors: Johnson C.H. , Druschitz E.A. , Druschitz A.P.
Published: March 2009

Leak path defects in brake caliper castings were observed and an efficient method of
detecting them was needed. The standard detection technique used a differential decay method at
pressures up to 1000 psi but this technique could not detect all of the leak path defects. The only
known method that could detect all of the leak path defects was a technique that used brake fluid,
and required pressures up to 3,000 psi. Because a fluid medium used to conduct this test,
regulations precluded the calipers from being used on a vehicle after the inspection process. This
was the motivation for a Capstone Project in the Mechanical Engineering Technology Program at
Central Washington University.
For safety and economic reasons, a nondestructive test which utilized acoustics was chosen. It
was decided that the main focus for this project would be the design of the fixture. The prototype
fixture was designed to utilize a toggle clamp and a backing plate (manifold) with O-rings. The
clamping system was produced at INTERMET Corporation. After the fixture was completed it was
sent to Central Washington University. To verify predictions, strain gauges were used at different
parts of the system during normal use. Then the placement of the acoustic listener was determined,
completing the test fixture.
In order to obtain a good seal (O-ring to cavity lip) the fixture required deflections less then
.0045” (as determined by tolerance stacking and O-ring deformation requirements). A magnetic pin
gauge was used to measure this displacement as it the fixture was pressurized to 82psi (available
shop pressure). To demonstrate the safety of the device, a strain gauge was mounted on the backing
plate to measure the force being counteracted by the toggle clamp. The maximum stress on the
backing plate was approximately 10% of the material's yield strength (~ 36 ksi for A36 steel);
producing a safety factor of about 10. No more than 3750 psi was measured. The maximum strain
of the backing plate was 0.003 in/in. Upon completion, the fixture was sent back to INTERMET
Corporation where a production model was designed and implemented.
Thixoforming of Steels - A Status Report
Authors: Bleck Wolfgang , Hirt Gerhard , Püttgen Wolfgang
Published: March 2009

The Thixoforming of metals is a new forming technology, which combines the advantages
of casting and forging. This technology focuses on structural components with complex shapes,
which can not be manufactured using conventional processing methods. Different components made
of aluminum and magnesium are already industrially produced. Apart from this, the use of steels in
the Thixoforming processes is still being researched and developed. During the last years it became
obvious that the Thixoforming of steels may not be a complete substitution for highly automated
die-casting or forging processes, but rather a new process route to produce special components with
high quality and geometrical demands. Special interest lies in the development and production of
filigree components, parts with voids or undercuts, integrated elements such as tubes or tube-systems
and joining pieces or products made of different materials. Beside the design of suitable tool
materials and tool concepts, the development of homogeneous heating strategies and the
development of thixoformable steels is at the center of current research. Therefore, this paper focuses
on material requirements which are needed for the Thixoforming of steels and on the production of
components and occurring problems. By use of a failure catalogue for Thixoforming of steels,
reasons for characteristic failures and suggestions are given to avoid them, so that the quality of
thixoformed parts can be improved.
Size Distribution of Retained Austenite in Phosphorus-Containing TRIP Steels
Authors: Zhao L. , van Dijk Niels H. , Peekstok E.R. , Tegus Ojin , Brück Ekkes , Sietsma Jilt
Published: March 2009

The present work investigates the influence of phosphorus addition on the size
distribution of retained austenite in TRIP steels containing 0.01%, 0.09% and 0.14% phosphorus.
The size of retained austenite is measured by means of neutron depolarization technique and optical
microscopy. It is found that the addition of phosphorous increases the size of the larger
intergranular and inter-ferritic austenite grains and therefore also increases the volume fraction of
retained austenite due to the strengthening effect of phosphorous on the surrounding ferrite and
bainite grains. For all phosphorous additions the most frequently observed austenite size is around
0.2 μm, which is probably corresponds to the interlath film-type retained austenite. The average
grain size from the neutron depolarization technique agrees in general with that from the optical
microscopy and it is suggested that the accuracy can be improved by further development of the
data analysis by taking into account the preferred shape and orientation of the austenite grains.
Low-Carbon Manganese TRIP Steels
Authors: Merwin Matthew
Published: March 2009

The development of TRansformation Induced Plasicity (TRIP) steels has seen much activity in
recent years, due to the promise of very high formability combined with high strength. The
accepted method for production of as-hot-rolled TRIP steel employs multistage runout table cooling
and coiling in the bainitic transformation temperature regime. As an alternative to confronting the
production difficulties the accepted strategy presents, a program was begun to evaluate the potential
of 0.1C-6.0Mn steels processed in a more conventional manner. Three laboratory heats were
melted to consider the effect of manganese content on processing and properties. The steels were
found to be fully hardenable with conventional hot-strip mill processing and subsequent batch
annealing simulations produced significant retained austenite levels. The combination of the prior
martensitic microstructure in the as-hot-rolled condition, and austenite created during annealing,
resulted in remarkable combinations of strength and ductility. In the as-hot-rolled condition, tensile
strengths exceeding 1400 MPa were observed, with total elongations of approximately 10 percent.
Optimum properties were found when samples were annealed at approximately 650°C. While this
treatment reduced the tensile strength to 800-1000 MPa, the total elongation increased to between
30 percent and 40 percent. UTS*TE products exceeding 30,000 MPa-% were observed, making
these materials attractive for high strength, high ductility applications.
Creep Property Evaluation of Heat-Resistant Steels by Small Punch Creep Test
Authors: Komazaki Shinichi , Nakata T. , Sugimoto Takayuki , Kohno Yutaka
Published: March 2009

The recently developed small punch (SP) creep test was applied to four different heatresistant
ferritic steels, namely, two kinds of conventional ferritic steels which had been actually
used in the high-temperature components for long periods and two advanced high chromium ferritic
steels for fusion reactor materials to investigate the applicability of the SP creep test. The ratio of
the load of SP creep test to the stress of standard uniaxial creep test was calculated so that both the
creep rupture curves (load/stress versus Larson-Miller parameter curves) were overlapped to
convert the results of SP creep test into those of standard test. As a result, the ratio was determined
to be 2.4, irrespective of the kind of ferritic steel. This result indicates that the creep rupture strength
of heat-resistance ferritic steels can be estimated using a miniaturized plate-type specimen and this
conversion coefficient 2.4 independent of the kind of ferritic steel.
Quenching and Partitioning of Ni-Added High Strength Steels
Authors: Rizzo F.C. , Martins A.R. , Speer John G. , Matlock David K. , Clarke A. , De Cooman Bruno C.
Published: March 2009

High strength steels containing significant fractions of retained austenite have been
developed in recent years, and are the subject of growing commercial interest when associated with
the TRIP phenomenon during deformation. A new process concept “quenching and partitioning”
(Q&P) has been proposed by CSM/USA, and the results show the potential to create a new kind of
steel microstructure with controlled amounts of retained austenite, enriched by carbon partitioning.
Four steels containing C, Si, Mn, Ni, Cr and Mo, were designed with variation in the Ni and C
content, aiming to decrease Bs temperature and to suppress carbide formation during the
partitioning treatment. Several heat-treatment procedures were performed in specimens previously
machined for tensile testing, while x-ray diffraction was used to determine the fraction of retained
austenite. The tensile test results showed that except for the high C high Ni alloy, most of the
processing conditions resulted in strengths superior to those of advanced high strength steels
(AHSS), although it is importantly recognized that higher alloy additions were used in this study, in
comparison with conventional AHSS grades.. A variety of strength and ductility combinations were
observed, confirming the potential of the Q&P process and illustrating the strong influence of the
final microstructure on the mechanical properties. Experimental results for samples partitioned at
400 °C indicate that higher ultimate tensile strength is associated with higher fraction of retained
austenite for multiple heat treatments of each alloy investigated. The amount of retained austenite
obtained was generally lower than that predicted by the model. Further studies are in progress to
understand the influence of alloying and processing parameters (time/temperature) on the
partitioning of carbon and precipitation of transition carbides.
The Ultra-Fine Bainitic Steels and Refinement Technology
Authors: Wang Xue Min , He Xin Lai , Yang Shan Wu , Shang Cheng Jia
Published: March 2009

By employing the new developed relaxation-precipitation-controlling phase
transformation (RPC) technique in large scale production the bainitic steels with ultra fine bainite
has been obtained. These bainitic steels have good synergistic properties. With the aid of thermal
simulation the refinement mechanism of RPC technique has also been investigated. The optical
microscope, scanning electron microscope, transmission electron microscope and Electron back
scattering diffraction technique were employed to study the features of microstructure produced by
RPC technique, precipitation and the evolution of dislocation configuration during the relaxation.
The results show that when produced by RPC technique the microstructure of the steel is mainly
ultra-fine lath bainite packets, and these bainite packets block each other. It is also found that during
the relaxation the dislocation cells form and strain induced precipitation occurs, the dislocation cell
pinned by the precipitates can confine the bainite transformation. After the relaxation during the
cooling the acicular ferrite forms at first and in succeeding the bainite transformation is blocked by
the acicular ferrite and the bainite is refined effectively.