bluuebunny/crossref_metadata_2025 huggingface dataset:
Tensile Creep Behaviors of a P-Type Structure Single Crystal Nickel-Base Superalloy
Authors: Du Hong Qiang , Tian Su Gui , Yu Xing Fu , Wang Ming Gang , Meng Fan Lai
Published: March 2009

By means of pre-compressive stress treated, the cubic γ΄ phase in alloy is transformed into the P-type structure along the direction parallel to the applied stress axis. The influence of the P-type structure on the creep lifetimes of alloy has been investigated by means of the tensile creep testing and microstructure observation. Results show that, compared with the A structure alloy, the P-type γ′ rafted alloy displays a shorter creep lifetimes under the experimental conditions. The microstructure evolution of the P-type structure alloy occurs during tensile creep, in which the p-type γ′ rafted phase is transformed into the N-type structure. The microstructure evolution alloy reduces the creep resistance of the alloy, this is one of the main reasons for reducing the creep resistance of the one.
High Fugacity Hydrogen Effects in Beta-21S Titanium Alloy
Authors: Eliezer Dan , Tal-Gutelmacher E. , Wagner Lothar
Published: March 2009

Beta-21S titanium alloy is ranked among the most important advanced materials for a
variety of technological applications, due to its combination of a high strength/weight ratio, good
corrosion behavior and oxidation resistance. However, in many of these technological applications,
this alloy is exposed to environments which can act as sources of hydrogen, and consequently, severe
problems may arise. The objective of this paper is to investigate the influence of high fugacity
hydrogen on Beta-21S alloy in as-received (mill-annealed and hot-rolled) condition. Hydrogen effects
on the microstructure are studied using X-ray diffraction and electron microscopy, while the
absorption and desorption characteristics are determined respectively by means of a hydrogen
determinator and thermal desorption spectroscopy. Preliminary results at room temperature revealed
hydrogen-induced straining and expansion of the lattice parameters. However, neither second phases
formation (hydrides), nor hydrogen-induced cracking, were observed after hydrogenation. The main
characteristics of hydrogen absorption/desorption behavior, as well as hydrogen-induced
microstructural changes in both microstructures are discussed in detail.
Study on Combustion Synthesis and Densification Process for Titanium Diboride and Iron Layered Materials
Authors: Wang Kun , Liu Jian Ping , Fu Zheng Yi , Wang Wei Min , Wang Hao , Zhang Jin Yong , Peng Yong , Zhang Qing Jie
Published: March 2009

The combustion synthesis and densification process for titanium diboride and iron layered
materials in the process of Self-propagating high-temperature synthesis of titanium diboride,
variation of the initial temperature, amount of diluent and particle size of raw materials had effect on
the adiabatic temperature, fraction of melted product and propagation rate of the combustion process,
were studied by theoretical calculation and experimental analysis. The result showed that divided by a
combustion temperature 3050K, either in the high temperature range or in the low temperature range,
the calculated process activation energies were 140 KJ/mol or 355 KJ/mol respectively, which
revealed two different reaction process mechanisms. Interfacial bonding between TiB2+Fe cermet and
Fe substrate was analyzed by EPMA, which showed interfacial bonding of two-layered product was
obtained by the dissolution and the diffusion of Ti in the Fe substrate and joining of Fe binder with Fe
substrate. The fractures of joints took place in the TiB2+Fe cermet layer rather than at the interface.
A First Principle Study of the Effect of Nb on the Oxidation Behavior of NiTi Alloy
Authors: Wu Hong Li , Zhao Xin Qing , Xu Jian , Zhou Chungen , Xu Hui Bin
Published: March 2009

A first principle study was performed to discuss the high temperature oxidation mechanism
of NiTi alloys with the special emphasis on the effect of Nb on the oxidation behavior. The
calculation results suggest that the Nb atom prefers the Ti site in Ni(Ti,Nb). The addition of Nb will
not only reduces the electron density of Ti-d and Ni-d states near the Fermi energy level but the their
electron contributions to the p-orbital of Ti. In addition, the Nb atom increases the formation energy
of the Ti defect, which will decrease the diffusion of Ti atoms. All these Nb-induced effects account
for the improvement of high temperature oxidation resistance, which agrees well with the
experimental results.
Corrosion Properties of Inconel Alloy 600 Coated by Simultaneous Aluminizing-Chromizing Process
Authors: Moosa Ahmed , Ahmed Jalil Karim , Hoobi Ali
Published: March 2009

In this work Inconel 600 alloy was coated with two different types of coatings, Crmodified
aluminide coating and Y- doped chromium modified aluminide coating . Diffusion coating
was carried at 1050 oC for 8 hrs under Ar atmosphere by single step aluminizing- chromizing process
and by single step aluminizing- chromizing- yttriumizing process. The cyclic hot corrosion tests of IN
600 and its coated systems deposited with 2 mg / cm2 NaCl / Na2SO4 (100/0, 50/50, and 0/100 wt. %)
deposits were conducted at 900 oC in air for 105 hrs at 15 hrs cycle.
The hot corrosion kinetic of uncoated Inconel 600 alloy follows parabolic rate law when oxidized
with 100% Na2SO4 deposits, whereas it follows a linear rate law when oxidized with 100% NaCl
deposits and with (50% NaCl + 50% Na2SO4) deposits. In cyclic hot corrosion tests, the parabolic rate
constant (kP) values for Cr- modified aluminide coating when oxidized with NaCl / Na2SO4
concentrations (100/0, 50/50, and 0/100 wt. %) deposits are: 2.67x10-6, 2.73x10-6, and 8.34x10-7
(mg2/cm4)/s. respectively. But for Y- doped chromium modified aluminide coating are: 2.10x10-6,
1.51x10-6, and 6.66x10-7 (mg2/cm4)/s. respectively, under the same test conditions. The kP values for
both coated systems oxidized with 100% Na2SO4 deposits are one order of magnitude lower than that
for 100% NaCl, and for (50% NaCl + 50% Na2SO4) deposits under the same test conditions.
Long-Term Oxidation Resistance of (Ti,Al,Y)N Coatings at 800 °C
Authors: Li Ming Sheng , Feng Chang Jie , Wang Fu Hui , Wu Wei Tao
Published: March 2009

Composite metastable Ti0.5Al0.5N, Ti0.49Al0.49Y0.02N and Ti0.48Al0.48Y0.04N coatings were
deposited on a wrought martensite steel 1Cr11Ni2W2MoV for aero-engine compressor blades by arc
ion plating respectively all coatings possessed a dense surface and the same B1NaCl phase structure
and the lattice parameter increased with increase of the incorporated element Y. Oxidation-resistance
of (Ti,Al,Y)N coatings at 800 for up to 500 hr was investigated and the results showed that the
introduction of yttrium into the coatings dramastically improved the oxidation-resistance of the
coatings in air. The presence of Y in the nitride coatings suppresses the outer diffusion of Fe through
the nitride coating. And the oxide of yttrium may segregate to the grain boundaries of oxides,
suppressing the outward diffusion of metallic elements in coating and the inward diffusion of oxygen.
Besides, the existence of adequate Y in the coatings is in favor of suppression of the growth of oxide
crystals, formation layered oxide scale and decrease of compressive stress of oxidation.
Structure and Anti-Corrosion of Tri-Layer Ni-P Amorphous Alloy Coating Prepared in the Same Bath
Authors: Zhu Li Qun , Du Yan Bin , Xue Zhen , Li Ying Xu
Published: March 2009

A tri-layer amorphous Ni-P alloy coating was prepared in the same bath by changing the
temperatures and currents, followed by heat treament. We studied the behavior of
corrosion-resistance of the tri-layer coating before and after heat-treatment at 360°C for different time
in the 5% NaCl solution. The result showed that: the tri-layer amorphous Ni-P coating has the
excellent performance of anti-corrosion compare with single electroless or electrodeposited Ni-P
amorphous coating. The performance of anti-corrosion of the coating was improved by controlling the
coating’s structure and the role of electrochemical protection. After being heat-treated at 360°C for 1
hour ,the coating’s structure changed from amorphous to crystalloid and the corrosion resistance of
the heat-treated coatings was higher than as-plated tri-layer Ni-P coating.
State of the Art in the Refining and Recycling of Magnesium
Authors: Zhang Li Feng , Dupont Tiphaine
Published: March 2009

In order for magnesium to continue to grow, all forms of magnesium scrap need to be
recycled – for both economic and environmental reasons. This paper extensively reviews the
techniques for the refining and recycling of magnesium. Removal of inter-metallic elements and
inclusions through gas fluxing, filtration and other methods are summarized. Flux refining technology
is the old but most common method to purify magnesium metal. Fluxless refining technologies are
under development, such as salt furnace technology, inert gas and filter refining, vacuum distillation
refining, and hydrometallurgical methods. Magnesium scraps recycling is discussed, techniques to
protecting Mg (or Mg alloy) melt with protective atmosphere and salt flux are briefly introduced.
Fluidity Evolution of an Al-10%B4C Metal Matrix Composite
Authors: Zhang Zhan , Chen X.-G. , Charette André
Published: March 2009

Aluminum boron carbide particulate reinforced composites are advanced materials which
have superior mechanical properties, and especially have the capability to capture neutrons. The
liquid mixing process is one of the methods to produce economically and effectively the metal matrix
composites. However, it was found that the fluidity of the composites was instable during liquid
holding and casting. To examine the fluidity evolution over the time, the melt of an Al-10%B4C
composite was hold at a constant temperature for a long period, and the fluidity was evaluated by
means of a vacuum fluidity test. The microstructure of the fluidity test samples was examined by
optical and electron microscopes. It is found that the interfacial reaction products between B4C and
Al-matrix play an important role for the deterioration of the composite fluidity.
Cracking Susceptibility and Joint Property Study of the 6061 Aluminum
Authors: Xue Xiao Huai , Du Hua , Yu Hai Liang , Yang Shu Fang , Deng Zheng Cai , Lou Song Nian
Published: March 2009

By means of FISICO test, the cracking susceptibility of the 6061 aluminum was
investigated, the experimental results showed that it is prone to form crater crack under restraint
condition comparison with that of the 3003 aluminum. So the crater fill-up technology need to be
employed accordingly during the field welding. The strength, elongation percentage and hardness of
the as welded joint was lowered 29.7%40%42% respectively, the former two is recovered to
73.4% and 81.7% of the base material respectively after natural aging 30days. This indicate that the
natural aging treatment can remedy part of the property loss during the welding.
Observation of As-Cast Microstructure Feature of Al Sheet Used for Can Manufacturing with High Forming Properties
Authors: Fu Gao Sheng , Chen Hong Ling , Chen Wen Zhe , Qian Kuang Wu
Published: March 2009

The as-cast microstructure feature of Al sheet with high forming properties used for
pressure can manufacturing pre-treated by different melt-treatment technique was observed and
analyzed by SEM, EDAX, TEM and selected area electron diffraction (SAED), etc. It was found that
the oxide inclusions in Al sheet were mainly γ-Al2O3, and the Fe-rich impurity phases in the sheet
mainly Al3Fe, T1(Al12Fe3Si) or (AlFeSiRE). The crystal structure of (AlFeSiRE) phase was too
complicated to be determined. The effect of melt-treatment technique on the as-cast microstructure of
the sheet was remarkable. There were a number of oxide inclusions in the Al sheet before or after
conventional melt-treatment, which distributed non-uniformly and gathered together in larger block
shape with the size of about 10-40μm. The Fe-rich impurity phases in the sheet were mainly Al3Fe
and T1, and a few of the meta-stable phase Al6Fe existed in the sheet. These Fe-rich impurity phases
appeared in a coarse, long needle/flake or skeletal form, and were easily to gather together with oxide
inclusions. When the Al sheet was treated by high-efficient melt-treatment, the amout of oxide
inclusions was decreased obviously, and these inclusions distributed more uniformly in the tiny
granular form (about or less than 4μm). The Fe-rich impurity phases were mainly (AlFeSiRE), and a
small amount of Al3Fe phases also existed in the material. The (AlFeSiRE) phases distributed
uniformly along grain boundary in tiny group/sphere or short stick form. No congregation of Fe-rich
phases with oxide inclusions was found in the material.
Slip Circle Constructions for Inhomogeneous Rotational Flow
Authors: Brown L.M.
Published: March 2009

Humphreys’ simple construction to aid understanding of the patterns of rotational plastic
flow observed near undeformable particles in a ductile plastically sheared matrix can be generalised
to predict flow under hardness indenters in crystalline metals. The consequences for internal stress
distributions and polycrystalline plasticity are briefly indicated.
Microstructure Evolution after Large Strain Deformation in Al-0.13%Mg
Authors: Bowen Jacob R. , Masui Toshiaki , Tsuji Nobuhiro
Published: March 2009

The effect of large strain deformation on microstructural refinement has been intensely investigated by many deformation processes. Two popular processes are equal channel angular extrusion (ECAE) and accumulative roll-bonding (ARB). This work presents the evolution of microstructure in Al-0.13%Mg as a function of von Mises strain for both ECAE and ARB in terms of high and low angle boundary spacing and relative fraction, as well as the stability of the deformed structures after a strain of 10, thereby allowing a direct comparison of the two processes. It is found that microstructural evolution as a function of strain is similar, and that ARB structures after a strain of 10 are more stable than ECAE on annealing.
Stimulated Grain Refinement in Ni-Fe Alloy by Coarse Particles during Warm Multi-Directional Forging
Authors: Miura Hiromi , Sakai Taku , Ueno Takanori , Fujita Nobuhiro , Yoshinaga Naoki
Published: March 2009

A Ni-30 mass% Fe alloy with dispersed coarse oxide particles, ranging from 1 to 3 μm in diameter, was multi-directionally forged (MDF) at temperatures between 773 K and 873 K at a true strain rate of 1 x 10-3 s-1 in vacuum. For comparison, a particle-free Ni-Fe alloy was also prepared and MDFed. At 873 K, an obvious flow softening occurred during MDF especially in the alloy with dispersed particles, while work hardening followed by steady-state flow appeared at 773 K in both alloys. With increasing cumulative strain, the average grain size became gradually finer. However, the evolved microstructure was quite different depending on temperature and dispersion of particles. At 873 K, in the alloy with particles, equi-axed fine grains of about 1.3 μm in average was uniformly evolved at a cumulative strain of Σε = 2.4, while at 773 K the microstructure was still inhomogeneous. The above experimental results suggest important role of coarse particles to stimulate grain refinement.
Comparison of Single Crystalline and Polycrystalline Behavior under High Pressure Torsion
Authors: Hafok Martin , Pippan Reinhard
Published: March 2009

By using techniques of severe plastic deformation a metallic material can be subjected to
an enormous strain that is not achievable by conventional methods of deformation. In this study
nickel single crystals with different crystallographic orientation and nickel polycrystals were
deformed by high pressure torsion. All nickel samples were processed up to the evolution of a
saturation microstructure where no further hardening of the material can be observed. In this region
all samples develop a similar microstructure and micro-texture. The differences in the fragmentation
of the microstructure and the micro-texture development between the single crystals and the
polycrystalline aggregate were examined using EBSD. A major difference between single crystals
and polycrystals was not only the microstructure evolution at low equivalent strains, but also the
development of a stable micro-texture, which is achieved earlier by the use of a polycrystalline
aggregate.
Annealing in a Natural Laboratory: an EBSD and Cl Study of Calcite and Quartz Growth from Volumes of Rock Heated by a Nearby Melt Intrusion
Authors: Piazolo Sandra , Prior David J. , Holness M.D. , Harstad Andreas O.
Published: March 2009

Annealing is an important mechanism of microstructural modification both in rocks and
metals. In order to relate directly changes in crystallographic orientation to migrating boundaries the
researcher has the option to investigate either samples where the grain boundary motion can be
directly tracked or a series of samples exhibiting successively higher degrees of annealing.
Here we present results from rock samples collected from two well characterised contact
aureoles (a volume of rock heated by the intrusion of a melt in its vicinity): One quartz sample in
which patterns revealed by Cathodoluminescence (CL) indicate the movement of grain boundaries
and a series of calcite samples of known temperature history. Electron backscatter diffraction
(EBSD) analysis is used to link the movement of grain, twin boundaries and substructures with the
crystallographic orientation / misorientation of a respective boundary.
Results from the quartz bearing rock show: (a) propagation of substructures and twin
boundaries in swept areas both parallel and at an angle to the growth direction, (b) development of
slightly different crystallographic orientations and new twin boundaries at both the growth
interfaces and within the swept area, and (c) a gradual change in crystallographic orientation in the
direction of growth. Observations are compatible with a growth mechanism where single atoms are
attached and detached both at random and at preferential sites i.e. crystallographically controlled
sites or kinks in boundary ledges. Strain fields caused by defects and/or trace element incorporation
may facilitate nucleation sites for new crystallographic orientations at distinct growth interfaces but
also at continuously migrating boundaries.
Calcite samples show with increasing duration and temperature of annealing: (a) systematic
decrease of the relative frequency of low angle grain boundaries (gbs), (b) decrease in lattice
distortion within grains, (c) development of distinct subgrains with little internal lattice distortion,
(d) change in lobateness of gbs and frequency of facet parallel gbs and (e) change in position of
second phase particles. These observations point to an increasing influence of grain boundary
anisotropy with increasing annealing temperature, while at the same time the influence of second
phase particles and subtle driving-force variations decrease.
This study illustrates the usefulness of using samples from natural laboratories and combining
different analysis techniques in microprocess analysis.
Pinning Forces Exerted by TiN Particles in Austenite of Structural Steels and Comparison with Driving Forces for Grain Growth and for Static Recrystallisation
Authors: Chaves J.I. , Medina S.F. , Gómez Manuel , Rancel L. , Valles Pilar
Published: March 2009

In this work the pinning forces exerted by TiN particles in the austenitic phase in two Ti microalloyed steels have been determined and compared with the driving forces for austenite grain growth and for static recrystallisation between hot rolling passes, respectively. TiN precipitate sizes were measured by transmission electron microscopy (TEM) and the precipitated volumes were calculated. These results were then used to calculate pinning forces. The driving forces for recrystallisation were found to be approximately two orders of magnitude higher than the pinning forces, which explains why the austenite in these steels barely experiences hardening during rolling and why the accumulated stress prior to the austenite→ferrite transformation is insufficient (low dislocation density) to refine the ferritic grain.
Temperature and Deformation Effects on the Recrystallization Microstructure and Texture of Wire Draw Steel
Authors: Zidani Mosbah , Boumerzoug Zakaria , Solas Denis , Baudin Thierry
Published: March 2009

In this work, the effect of the deformation, caused by cold wire drawing, on the
microstructure and the texture of low carbon steel wire (0.06 wt % C) is examined. The combined
influence of the deformation level and the recrystallization temperature on the development of new
grains is studied for all wires. Isothermal tests of annealing allow the determination of the critical
temperature of recrystallization estimated above 450°C. The temperature effect is studied below the
eutectoid level, at 500°C, 600°C and 680°C. The appearance of a homogeneous recrystallization is
noted over the section of the wire. The recrystallized grains keep the same orientation as the
deformed grains. The expansion of time of annealing lead to recrystallization in the ferritic grains
accompanied by a spheroidization of the lamellar pearlite. The kinetics of recrystallization and
spheroidization are accelerated by increasing of annealing temperature and the deformation level.
The experimental techniques used in this study are: the Scanning Electron Microscope (SEM),
the Electron Back Scattered Diffraction (EBSD), the X-ray diffraction and Vickers microhardness.
Texture Evolution during Recrystallization in Nonoriented Electrical Steels
Authors: Park Jong Tae , Choi Jae Young , Kim Jae Kwan , Szpunar Jerzy A.
Published: March 2009

In nonoriented electrical steels, the control of texture has received little attention, and hence there is an unexplored possibility to improve the magnetic properties of nonoriented steels through texture control. Furthermore, the formation of recrystallization texture in these steels has not yet been systematically studied. In this study, such systematic investigations are undertaken for nonoriented electrical steels with 2% Si. New information obtained from EBSD measurements on partially recrystallized specimens will allow us to know what is happening during the recrystallization stage. The formation of recrystallization texture is much better explained by oriented nucleation. This is supported by the fact that the area fraction of nuclei or recrystallized grains with specific orientations for all new grains remains almost constant during the progress of recrystallization. Most nuclei have a high misorientation relationship with the surrounding deformed matrix: 25~55. The main texture components of nuclei or recrystallized grains during the progress of recrystallization are Goss and {111}<112>. Deformed {111}<110> and {111}<112> grains generally disappear at the early stage of recrystallization whereas deformed {001}<110> and {112}<110> grains are mostly consumed at the late stage of recrystallization.
Modelling the Deformation and Annealing Processes: Physical and Regression Approaches
Authors: Somani Mahesh C. , Karjalainen L. Pentti
Published: March 2009

The flow stress behaviour of ferrite under abruptly reduced strain rate has been modelled by employing the relatively simple approach of the Bergström’s model for plastic deformation of metals. This physical model considers the rate of change of dislocation density as a difference of the rate of dislocation immobilisation and remobilization, estimated as a function of a recovery parameter. The concept of average rest time of immobilized dislocations prior to remobilization has been suitably employed to estimate the transient times and the enhancement of recovery rates after the strain rate change. The transient friction stress was estimated by using equations given in the literature and some mathematical factors concerning the estimated dislocation densities and the net rates of dislocation immobilization at the high and low strain rates. The present authors have also developed a new unique regression model that is able to predict the static recrystallisation kinetics of most of the common carbon steel grades (including microalloyed steels). A linear regression equation was established to predict the activation energy of static recrystallisation for hot-worked austenite as sum effects of potent solute elements. Further, the power of grain size in the equation was found to be a strong grain-size dependent variable. The model was later validated for several special steel grades, as well as including the consideration for an upper limit for Nb and Si in retarding recrystallisation.
Fracture Toughness of Iron Boride Layers Obtained by Paste Boriding Process
Authors: Ramírez G. , Campos-Silva Ivan , Balankin Alexander S.
Published: March 2009

The fracture toughness of the Fe2B phase was evaluated in this study. Formation of the Fe2B boride is carried out though paste boriding process applied on AISI 1045 steel surface. The treatment was carried out at temperatures of 1193, 1223 and 1273 K for 6 h using a 5 mm thick boron paste. A Vickers microhardness tester was used to generate microcracks at a load of 200g. The indentations were made across the thickness of the iron boride layer at four different distances from the substrate. The experimental results show that the critical stress intensity factor KIC for the Fe2B phase shows a potential law dependence on crack length; this contradicts the concepts of Linear Elastic Fracture Mechanics, which establish that the fracture toughness value is a constant of the material.
Production of Zinc Oxide Nanoparticles by Liquid Phase Processing: an Investigation on Optical Properties
Authors: Vafaee Mehran , Youzbashizade Hossein
Published: March 2009

In the recent years, many researchers have been interested in nanoparticles because of their unique properties. In this study, a method for producing ZnO nanoparticle colloids is proposed. The colloids were characterized by spectroscopic analyzer. By absorption spectrum study, we found out that colloids were consisted of nanoparticles with less than 10 nanometer size. The quantum confinement effect in these spectrums was recognized through blue shift of onset absorption wavelengths. These wavelengths shift from 370 nm to 340 nm by decreasing the particles size. Transmittion electron micrographs showed formation of zinc oxide nanoparticles.
Vacuum Heat Treatment of MgO -Densified Pressureless Sintered Silicon Nitride Ceramics
Authors: Demir V. , Thompson Derek P.
Published: March 2009

Silicon nitride samples were pressureless sintered with up to 5 w/o MgO to give densities
in the range 98-99% of theoretical. After pressureless sintering, selected samples were placed in a
vacuum heat treatment furnace surrounded by a carbon bed in a carbon crucible at a pressure of less
than 4x10-4 mbar, and vacuum heat treated at different temperatures and times to remove grainboundary
glass. The results showed that this was substantially achieved at 1575oC for 3h and that
increasing the time to 5 hours gave still further improvement. SEM images, EDX analysis and
oxidation tests provided additional evidence for the removal of Mg from the samples.
Carbothermal Reduction and Nitridation of Quartz Mineral for the Production of Alpha Silicon Nitride Powders
Authors: Demir Adem , Tatli Zafer , Caliskan F. , Kurt A.O.
Published: March 2009

In this study, α-Si3N4 powder was produced by carbothermal reduction and nitridation
(CRN) of quartz from Can-Canakkale. Carbon with a specific surface area of 110 m2g−1 and quartz
powders were mixed then the powder mix was placed in an alumina tube furnace and reacted in
between 1300-1500°C for 4 hours under nitrogen flow. The quartz powder was carbothermally
reduced and nitrided to form silicon nitride powders. XRD results showed that the reaction product
was mainly α-Si3N4 and contained some β-Si3N4 and residual quartz. In order to reduce amount of
unreacted quartz, the raw materials mixture was grinded either with carbon black or with no carbon.
After CRN reactions of separate grinded quartz powders with carbon, residual quartz was
disappeared, reaction temperature was decreased and α-Si3N4 rate was increased. Hence, a better
mixing of carbon and fine silica enhanced the α phase formation. SEM images and XRD pattern
showed that sub micron particles (0.6–0.87m), high α-phase content Si3N4 powders can be
produced at 1450°C for 4 h in flowing nitrogen gas during the CRN process.
Time Dependent Trapping and Generation-Recombination of Interface Charges: Modeling and Characterization for 4H-SiC MOSFETs
Authors: Potbhare Siddharth , Goldsman Neil , Pennington Gary , Lelis Aivars J. , McGarrity J.M.
Published: March 2009

SiC MOSFETs have very large interface trap densities which degrade device performance. The effect of traps on inversion layer mobility and inversion charge concentration has been studied, and mobility models suitable for inclusion in Drift-Diffusion simulators have been developed for steady state operation of SiC MOSFET devices. Here, we attempt to model the transient behavior of SiC MOSFETs, and at the same time, extract the time constants for the filling and emptying of interface traps. As compared to the inversion layer, interface traps in SiC MOSFETs are slow in reacting to change in gate bias. So, at the positive edge of a gate pulse, we see a large current in the MOSFET, which then decays slowly to the steady state value as the interface traps fill up. We have developed a generation/recombination model for minority carriers in a SiC MOSFET based on the Shockley-Read-Hall recombination model for electrons and holes. In our model, the generation/recombination takes place between minority carriers in the inversion layer, and the traps at the SiC-SiO2 interface. Comparing our simulated current vs. time curves to experiment, we have been able to extract time constants for the filling and emptying of traps at the SiC-SiO2 interface.
Theory of Grain Growth in the Presence of Atoms Drag Effects
Authors: Abbruzzese Giuseppe Carlo , Buccioni Massimiliano
Published: March 2009

The statistical model of grain growth is able to predict the effect of Zener drag on the grain size distribution evolution and on grain growth kinetics [1, 2]. This paper, in the same framework, will treat the case of atoms drag on grain boundary movement. The mechanism by which atoms drag operates is significantly different by that of Zener. The corresponding peculiar features will result in a specific grain size distribution evolution with considerable change of grain growth kinetics and distribution shape from that of normal grain growth case as a function of the intensity of the pinning conditions.
Effects of Al, Si and Mn on the Recrystallization Behaviors of Fe Containing 70B Brass
Authors: Akbari G.H. , Abbaszadeh H. , Ravandi H. Ghotbi
Published: March 2009

The effects of alloying elements and impurities on the microstructure and properties of metals and alloys are important. Understanding of these effects may help to control and produce products with desired properties at lower cost. In the present work the effects of Al, Si and Mn on the recrystallization behavior, hardness and microstructural changes of an Fe- containing brass during annealing were studied. The results show that alloying elements strongly affect recrystallization kinetics and resulted finer microstructures. Hardness variations during annealing are consistent with microstructural observations and the presence of alloying elements. All elements slow down recrystallization progress and increase resulted hardness values. The resulted microstructures in the presence of alloying elements are much finer than that of plain 70B brass. It was concluded that the present alloying elements affect the recrystallization behavior of 70B brass in a similar manner. Their mechanism of interactions is solute drag effect and their effects sum up when they present together.
Abnormal Grain Growth during Annealing in Nanocrystalline Fe-Ni Alloys
Authors: Seo J.H. , Kim Jong Kweon , Park Yong Bum
Published: March 2009

The texture evolution due to grain growth that takes place during annealing was investigated in nanocrystalline Fe-Ni alloys fabricated by using an electroforming method. In the current materials, the as-deposited textures were of fibre-type characterized by strong <100>//ND and weak <111>//ND components, and the occurrence of grain growth during annealing resulted in the strong development of the <111>//ND components with a significant decrease of the <100>//ND components. It was clarified that abnormal grain growth plays an important role on the evolution of the microstructures and textures. The abnormally grown grains were observed using orientation imaging microscopy in the early stages of grain growth, and their morphological features have been discussed.
Nucleation and Grain Growth Kinetics of Amorphous to Nanocrystalline Ceria Solid Solutions
Authors: Rupp Jennifer L.M. , Scherrer Barbara , Gauckler Ludwig J.
Published: March 2009

Nanocrystalline ceria-based thin films are of potential interest for use as gas-sensing layers and
electrolytes in micro-Solid Oxide Fuel Cells (micro-SOFC) used for energy supply of next
generation portables. In these devices the thin films have to be operated at intermediate to high
temperatures (500 - 1000 °C) to be sufficiently high electrical conductive. However, only little is
known on the nucleation and grain growth kinetics of pure ceria and its solid solutions when present
as nanocrystalline thin film microstructures (average grain size < 100 nm). In this study amorphous,
dense and crack-free CeO2 and Ce0.8Gd0.2O1.9-x thin films have been deposited by spray pyrolysis on
sapphire. These films were crystallized to biphasic amorphous-nanocrystalline and fully
nanocrystalline microstructures upon annealing with respect to time, temperature, heating rate and
doping. Nucleation and grain growth kinetics were studied by differential scanning calorimetry, Xray
diffraction analysis with in-situ heating chamber and scanning electron microscopy.
Crystallographic Texture Change of Pilgered Zirconium Alloy Tubes with Heat Treatment
Authors: Choi Y. , Inoue Hirofumi
Published: March 2009

Crystallographic texture of pilgered zirconium alloy tubes was analyzed by neutron diffraction, electron
backscatter diffraction (EBSD) and X-ray techniques to study bulk and local texture change with pilgering
and heat treatment above re-crystallization temperature. Pilgering resulted in slightly inclining (001) planes
to sample normal direction, and aligning effectively (100) planes to the normal of radial direction,
respectively. (001) planes of the zirconium tube uniformly exist in radial and tangential directions, however,
the (001) planes moved from tangential to radial directions after pilgering followed by heat treatment for 20
hours at 540°C. Some of (001) and (100) planes of pilgered tube were paralleled to longitudinal direction by
re-crystallization.
Understanding a Microstructure Using GOS (Grain Orientation Spread) and Its Application to Recrystallization Study of Hot Deformed Al-Cu-Mg Alloys
Authors: Cheong Soon Wuk , Weiland Hasso
Published: March 2009

The softening process consists of recovery and recrystallization. Despite the significant effect of recovery on the softening, recovery has not enjoyed the attention as much as recrystallizaion has mostly due to difficulties in the microstructural characterization of recovery. The present study introduced GOS qualitatively and quantitatively to gauge the microstructural evolution occurring during annealing. Then the GOS analysis was applied to discern alloying effects on recrystallization in hot deformed Al-Cu-Mg alloys. Recovery seems accountable for the retardation of recrystallization in the Mn containing alloys. By adding Zr to Al-Cu-Mg-Mn, recrystallization could be further inhibited.
The Effect of Grain Size and Rolling Reduction on the Texture Development of a Metastable Austenitic Stainless Steel
Authors: Han S.Y. , Higginson R.L. , Palmiere Eric J.
Published: March 2009

It is well known that the deformation and recrystallisation of metals and alloys are accompanied by changes in texture and microstructure. These changes can lead to anisotropy in metal flow and affect the formability of sheet metals. Therefore, a significant amount of research on the development of textures and the principles governing them has been conducted in recent years. One of the most important factors contributing to the texture development of materials is the initial grain size. Unlike other factors such as stacking fault energy, strain and deformation temperature, relatively little work has been carried out on the effect of grain size on texture development, even though a considerable understanding exists regarding the effect of grain size on work hardening and recrystallisation kinetics upon annealing. Hence, this research describes the effect of the initial hot band grain size on the development of texture during cold rolling and subsequent annealing.
Recrystallization Textures of Al-Mg-Si Alloy Sheets Produced by Symmetric and Asymmetric Combination Rolling
Authors: Inoue Hirofumi , Hori M. , Komatsubara Toshio , Tanaka Hiroki , Takasugi Takayuki
Published: March 2009

In order to improve deep drawability of 6000 series aluminum alloys for automotive body
panels, texture control for increasing r-value of the sheets was attempted by combination of
symmetric and asymmetric rolling. Asymmetric warm rolling at relatively low reduction after
symmetric rolling made it possible to form TD-rotated β-fiber texture including {111} components.
Recrystallization textures of the T4-treated materials varied significantly depending on roll speed
ratio and reduction in asymmetric warm rolling. On appropriate rolling conditions, {111}<110>
orientation with high r-value was formed as a main component of recrystallization texture. On the
other hand, two-stage heat treatment consisting of low temperature annealing and subsequent
T4-treatment led to a significant change in recrystallization texture. In the sample annealed for long
time at a low temperature, TD-rotated β-fiber rolling texture was retained even after solution
treatment at a much higher temperature, because recovery or recrystallization took place to some
extent during low temperature annealing.
The Evolution of Texture and Stored Energy during Recrystallization of IF High Strength Steel Investigated by Means of Orientation Imaging Microscopy
Authors: Lee Kyoo Young , Kim Gyo Sung , Chin Kwang Geun , Kestens Leo
Published: March 2009

The evolution of texture and stored energy was studied for Ti bearing and Ti-Nb bearing IF high strength steel undergoing a double cold rolling and annealing treatment by using Orientation Imaging Microscopy. Ti bearing IF high strength steel showed a similar texture evolution of the α and γ fiber components to that of IF steel. On the contrary, Ti-Nb bearing IF high strength steel displayed a different texture evolution from the one observed in the former steels. The difference in texture and stored energy evolution between both high strength steels seemed to be affected by the segregation behavior of solute alloying elements such as P.
Effect of Changing Homogenization Treatment on the Particle Structure in Mn-Containing Aluminium Alloys
Authors: Pettersen Tanja , Li Yan Jun , Furu Trond , Marthinsen Knut
Published: March 2009

During casting and homogenisation of aluminium the microstructural fundament for
further processing is made. Particle structure (dispersoids and primary particles), grain structure and
level of elements in solid solution govern the mechanical and annealing properties of the material.
In 3xxx-alloys, Mn in solid solution and Mn-containing dispersoids formed during homogenisation
play an important role in controlling the recrystallization behaviour of the material [e.g. 1, 2, 3].
Other elements, such as Si, will have an influence on the formation of dispersoids [4, 5]. Hence, to
control the annealing behaviour of the material, it becomes important to control the particle
structure. In the present investigation, an AA3103 alloy, and modified versions of this alloy, have
been investigated. Various homogenisation treatments have been performed and the resulting
material has been studied. Electrical conductivity has been measured and microstructural
investigations have been carried out.
Relation between Initial Texture and Microstructure and Nucleation and Growth Mechanisms in Metals
Authors: Bacroix Brigitte , Brenner Rénald , Zhu K. , Réglé Hélène , Wauthier Aurelie , Chaubet D. , Castelnau Olivier
Published: March 2009

Nucleation and normal or abnormal grain growth of new grains have been observed in several metals and alloys during annealing after various levels of strain (from few percents for abnormal grain growth in steel and aluminium to 90 % strain for static recrystallization of highly deformed copper, zirconium and steel). For each of these cases, the links between the initial deformation state of the polycristalline samples and their final textures after annealing are analyzed in some details, by taking into acount the distribution of orientations and misorientations within the samples, as well as the repartition of stored energy . With the help of polycristalline models for the simulation of deformation and recrystallization processes, some general conclusions regarding the nucleation and growth processes are finally drawn.
Microstructure Evolution during Warm Deformation of Low Carbon Steel with Dispersed Cementite
Authors: Gallego J. , Jorge Alberto Moreira , Balancin O.
Published: March 2009

The microstructure evolution and mechanical behavior during large strain of a 0.16%CMn
steel has been investigated by warm torsion tests. These experiments were carried out at 685 °C
at equivalent strain rate of 0.1 s-1. The initial microstructure composed of a martensite matrix with
uniformly dispersed fine cementite particles was attained by quenching and tempering. The
microstructure evolution during tempering and straining was performed through interrupted tests.
As the material was reheated to testing temperature, well-defined cell structure was created and
subgrains within lath martensite were observed by TEM; strong recovery took place, decreasing the
dislocation density. After 1 hour at the test temperature and without straining, EBSD technique
showed the formation of new grains. The flow stress curves measured had a peculiar shape: rapid
work hardening to a hump, followed by an extensive flow-softening region. 65% of the boundaries
observed in the sample strained to ε = 1.0 were high angle grain boundaries. After straining to ε = 5.0,
average ferrite grain size close to 1.5 1m was found, suggesting that dynamic recrystallization took
place. Also, two sets of cementite particles were observed: large particles aligned with straining
direction and smaller particles more uniformly dispersed. The fragmentation or grain subdivision that
occurred during reheating and tempering time was essential for the formation of ultrafine grained
microstructure.
Kinetics of a Grain in a Textured Matrix
Authors: Glicksman Martin E. , Rios Paulo Rangel , Lewis Daniel
Published: March 2009

The multiplicity and variety of grain shapes in three-dimensional polycrystalline metals makes their energetic and kinetic analyses difficult. To help simplify the analysis of isotropic polycrystals, average N-hedra (ANHs) (N=3,4,5,…∞) were created as a set of regular polyhedra, consisting of N identical faces, which act as topological “proxies” for analyzing the corresponding class of irregular grains containing mixed faces of the same number. This paper outlines a further generalization of the ANH concept that extends three-dimensional analysis to include the growth or shrinkage of a small population of grains embedded in a textured matrix.
Processing of FeCo Nanosized Soft-Magnetic Material by Powder Metallurgy Technique
Authors: Daoush W.M.
Published: March 2009

A nanosized cobalt-based alloy containing 20 wt % Fe was synthesis by electroless chemical reduction method using alkaline tartarate bath and sodium hypophosphite as a reducing agent . The powder was investigated by optical microscope, SEM and XRD to identify the powder shape, size and the chemical composition. The prepared powder has a spherical shape with a particle size of about 200 nm. The investigated powder was cold compacted at 600 MPa and then sintered in hydrogen atmosphere at 1050 0C. Metallographic, physical, magnetic and electrical properties investigations were carried out for the prepared powder and its sintered compacts. The prepared powder has 2.5% phosphorus content which was liberated by heating the compacts to the sintering temperature in hydrogen atmosphere. From the results of the density measurements we can observe that the prepared sintered FeCo material had a relative density about 96% to the theoretical. But the results of the electrical properties measurements give an indication of the decreasing in the electrical resistivity than the materials produced by the traditional methods. On the other hand the magnetic measurements, of the FeCo powder has a lower specific saturation induction, Bs, than the sintered one which was due to the presence of the paramagnetic metal phosphides in the powder but after rising the temperature to sintering the, Bs, values is increased due to the conversion of the phosphides to the metallic state and the phosphorus was liberated, but the coercive force was decreased by sintering of the powder compacts by lowering the porosity of the materials with sintering and the formation of the soft magnetic materials Fe-Co solid solution which was investigated by XRD having the highest specific saturation induction value. Also the magnetic permeability of the prepared sintered material was increase with increasing the applied field until 50 Oe which has the highest value and decreased with increasing the field more than 50Oe. From the magneto-resistance measurements, it was shown that the sintered material has a positive magneto-resistance in the field direction but a negative one in the direction perpendicular to the current and the field.
Improvement of the Fatigue Characteristic of AZ31 Magnesium Alloy by Microstructures Control
Authors: Nagata Yasuaki , Noda M. , Shimizu Hideharu , Funami Kunio , Mori H.
Published: March 2009

High-strain conditions as a means of microstructure control have recently been investigated to improve the ductility and enhance the strength of magnesium alloys. The level of superplastic deformation and the fatigue properties of the wrought materials have also been studied. In comparison, only a small number of such reports are available on cast materials. As a part of the search for applications of magnesium alloys, comparisons of structural changes and mechanical properties should be made between wrought and cast materials. In the present study, the grain refinement of cast and extruded materials made from commercially available AZ31 magnesium alloy was conducted using a multi-axial alternative forging method. The relationships between the structural changes and working processes and the relationships between changes in the mechanical properties as well as grain sizes and fatigue properties are discussed. Both the cast and the extruded materials tended to exhibit uniform crystalline structures with an increasing number of working cycles. Dynamic recrystallization was observed during both working and static recrystallization during both reheating and holding. When an equivalent strain of 0.6 was applied, the localized formation of ultra-fine grains of 0.5 μm was observed. The tensile strength and yield stress had maximum values in the initial stage of the multi-axial alternative forging. Although ductility improved with higher numbers of working cycles, the strength decreased. This can be explained by the dynamic and static recrystallization processes and work softening.