bluuebunny/crossref_metadata_2025 huggingface dataset:
A Comparison of High Temperature Performance of SiC DMOSFETs and JFETs
Authors: Ryu Sei Hyung , Krishnaswami Sumi , Hull Brett A. , Heath Bradley , Husna Fatima , Richmond Jim , Agarwal Anant K. , Palmour John W. , Scofield James D.
Published: March 2009

High temperature characteristics of 4H-SiC power JFETs and DMOSFETs are presented
in this paper. Both devices are based on pn junctions in 4H-SiC, and are capable of 300oC operation.
The 4H-SiC JFET showed very predictable, well understood temperature dependent characteristics,
because the current conduction depends on the drift of electrons in the bulk region, which is not
restricted by traps in the MOS interface or at the pn junctions. On the other hand, in a 4H-SiC
DMOSFET, electrons must flow through the MOS inversion layer with a very high interface state
density. At high temperatures, the transconductance of the device improves and threshold voltage
shifts negative because less electrons are trapped in the interface states, resulting in a much lower
MOS channel resistance. This cancels out the increase in drift layer resistance, and as a result, a
temperature insensitive on-resistance can be demonstrated. The performance of the two devices are
compared, and a discussion of issues for their high temperature application is presented.
High Frequency 4H-SiC MOSFETs
Authors: Gudjónsson G. , Allerstam Fredrik , Nilsson Per Åke , Hjelmgren Hans , Sveinbjörnsson E.Ö. , Zirath Herbert , Rödle T. , Jos R.
Published: March 2009

We present new results on 4H-SiC RF power MOSFETs. By improvements in device
layout we obtain better high frequency performance compared to the first generation of devices. An
extrinsic transition frequency fT=11.4 GHz was achieved and fmax=11.2 GHz for a device with 0.5 µm
nominal channel length. Functional devices with 0.3 µm nominal channel length were also made.
These devices gave fT=15.1 GHz and fmax=19.5 GHz but they have lower breakdown voltages and
therefore lower overall performance. The measured devices are double fingered with 0.8 mm total
gate width.
Improvement of Electrical Characteristics of Ion Implanted 4H-SiC MESFET on a Semi-Insulating Substrate
Authors: Katakami S. , Ogata Makoto , Ono Shuichi , Arai Manabu
Published: March 2009

The electrical characteristics of a SiC-MESFET are affected by the channel structure
characteristics, such as impurity density and thickness. MESFETs fabricated with ion implantation
technique, can form thinner and higher doped channel layers than those fabricated with conventional
epitaxial growth, thus improve RF characteristics of MESFETs. We calculated the doping profile of
the channel layer for an ion implanted SiC-MESFET using a simulator and then fabricated a
SiC-MESFET with the same doping profile as obtained from the simulation. The ion implanted
SiC-MESFET operated successfully and had the same electrical characteristics as the epitaxial
SiC-MESFET. We demonstrated the effectiveness of one-step implantation channel layer for the ion
implanted SiC-MESFET.
Development of High Growth Rate SiC Epi-Reactor with Controlled Thermal Gradient
Authors: Ito Masahiko , Tsuchida Hidekazu , Kamata Isaho , Storasta L.
Published: March 2009

A vertical hot-wall type reactor, with a unique structure designed for controlling both gas
flow behavior and thermal gradient (T/mm) on the susceptor surface, was developed. The simulation
results indicate that depending on the height of the epitaxy room (h), the T/mm can be changed from
a negative to a positive value. Preliminary epitaxial growth experiments resulted in a maximum
growth rate of 51 μm/h, 4-inch area uniformity of σ/mean=1.7% for growth rate and σ/mean=21.5 %
for doping concentration, and Z1/2 trap concentration of 9×1012 cm-3 at a growth rate of 43 μm/h.
Lateral 4H-SiC MOSFETs with Low On-Resistance by Using Two-Zone Double RESURF Structure
Authors: Noborio Masato , Suda Jun , Kimoto Tsunenobu
Published: March 2009

4H-SiC lateral MOSFETs with a double reduced surface field (RESURF) structure have
been fabricated in order to reduce drift resistance. A two-zone RESURF structure was also employed
in addition to double RESURF structure for achieving both high breakdown voltage and low
on-resistance. After device simulation for dose optimization, 4H-SiC two-zone double RESURF
MOSFETs have been fabricated. The fabricated MOSFETs block 1380 V and exhibit a low
on-resistance of 66 m1cm2 (including a drift resistance of 24 m1cm2) at a gate oxide field of
3 MV/cm. The figure-of-merit of present device is about 29 MW/cm2, which is the best performance
among any lateral MOSFETs. The drift resistance of the fabricated double RESURF MOSFETs is
only 50 % or even lower than that of single RESURF MOSFETs. Temperature dependence of device
characteristics is also discussed.
600 V 100 A 4H-SiC Junction Barrier Schottky Diode with Guard Rings Termination
Authors: Yamamoto Tsuyoshi , Endo Takeshi , Kato Nobuyuki , Nakamura Hiroki , Sakakibara Toshio
Published: March 2009

4H-SiC SBDs have been commercialized for power application devices. However, the
maximum current of these SBDs is 20A. In this work, we designed a JBS (junction barrier
Schottky) diode structure and the fabrication processes to be optimized. The current and breakdown
voltage were over 100 A and 660 V at Ir = 1 mA/cm2, respectively. The recovery characteristics of
the JBS diode are much superior to those of the Si-FRD while it is comparable to those of the
commercially available SiC-SBD at elevated temperatures up to 125°C..
Bipolar SiC-Diodes – Challenges Arising from Physical and Technological Aspects
Authors: Bartsch Wolfgang , Mitlehner Heinz , Gediga S.
Published: March 2009

In this contribution we summarize measurements on bipolar high voltage SiC-diodes
which were fabricated on 4H-SiC wafers preferentially cut 4° off the [0001] basal plane, whereas
the p-emitter thickness was varied in predetermined ratios to the n-base thickness. The switching
behaviour of optimized 6.5 kV-Diodes at a current level of 25 A is shown at DC link voltages up to
4 kV and at a junction temperature of 125°C. Experimental results are discussed in terms of
snappiness.
4H-SiC Schottky Array Photodiodes for UV Imaging Application Based on the Pinch-off Surface Effect
Authors: Sciuto Antonella , Roccaforte Fabrizio , Di Franco Salvatore , Raineri Vito , Liotta S.F. , Billotta Sergio , Bonanno Giovanni , Belluso Massimiliano
Published: March 2009

The fabrication of high sensitive diodes array is very attractive for spectroscopic and
astronomical UV imaging applications, particularly when visible light rejection is required. Wide
band gap materials are excellent candidates for UV “visible blind” detection. In this paper, we
demonstrate an array of Schottky UV-diodes on 4H-SiC with a single pixel area of about 1.44 mm2
and a total area of about 29 mm2. The Schottky photodiodes are based on the pinch-off surface
effect, the front electrode being an interdigit Ni2Si contact that allows the direct light exposure of
the optically active device area. For the proposed array, the optically active area is about the 48 %
of total area. The single pixel dark current was below 0.1 nA up to –50 V and a fabrication yield of
about 90 % was observed. The external quantum efficiency of the proposed array exhibits a peak of
45 % at the 289 nm wavelength and a visible rejection ratio > 4 ×103.
The Influence of the Extreme Fluences of 8 MeV Protons on Characteristics of SiC Nuclear Detectors Produced by Al Implantation
Authors: Ivanov Alexander M. , Strokan Nikita B. , Lebedev Alexander A. , Kozlovski Vitalii V.
Published: March 2009

The charge collection efficiency (ССЕ) of SiC-detectors preliminarily irradiated with
8 MeV protons at a fluence of 1014 cm-2 has been studied. Nuclear spectrometric techniques with
5.4 MeV α-particles were employed to test the detectors. The concentration of primarily created
defects was estimated to be 4×1016 cm-3. A strong compensation of SiC was observed, which
allowed connection of the structure in the forward mode. The experimental data obtained were
processed using a simple two-parameter model of signal formation. The model makes it possible to
separate the contributions of electrons and holes to the ССЕ. An additional irradiation at a fluence
of 2×1014 cm-2 reduced the ССЕ value by a factor of 2 and gave rise to polarization. The latter
indicates that radiation-induced centers are not only actively involved in carrier localization (with a
decrease in the lifetime), but also in transformation of the electric field within the detector.
Demonstration of High-Voltage SiC VJFET Cascode in a Half-Bridge Inverter
Authors: McNutt Ty , Reichl John , Hearne Harold , Veliadis Victor , McCoy Megan , Stewart Eric J. , Van Campen Stephen , Clarke Chris , Bulgher Dave , Katsis Dimos , Geil Bruce , Scozzie Skip
Published: March 2009

This work utilizes silicon carbide (SiC) vertical JFETs in a cascode configuration to
exploit the inherent advantages of SiC and demonstrate the device under application conditions. The
all-SiC cascode circuit is made up of a low-voltage normally-off vertical JFET, and high-voltage
normally on vertical JFET to form a normally-off cascode switch. In this work, a half-bridge
inverter was developed with SiC cascode switches for DC to AC power conversion. The inverter
uses high-side and a low-side cascode switches that are Pulse Width Modulated (PWM) from a
500 V bus to produce a 60 Hz sinusoid at the output. An inductor and a capacitor were used to filter
the output, while a load resistor was used to model the steady-state current of a motor.
Phase-Field Simulation of Cooperative Growth of Pearlite
Authors: Nakajima Katsumi , Tanaka Yasushi , Hosoya Yoshihiro , Apel Markus , Steinbach Ingo
Published: March 2009

Cooperative growth of pearlite is simulated for eutectoid steel using the multi-phase field
method. This allows to take into account diffusion of carbon not only in γ phase, but also in α phase.
The lamellar spacing and growth velocity are estimated for different undercoolings and compared
with experimental results from literature and theoretical results from analytical models. It is predicted,
that diffusion in ferrite and growth of cementite from the ferrite increase the kinetics of pearlitic
transformation by a factor of four as compared to growth from austenite only, which is assumed by the
classical Zener-Hillert model. Further on the effect of stress due to inhomogeneous carbon
distribution in austenite and due to transformation strain is discussed shortly.
Implementation of Twin Reorientation and Softening Schemes in a Polycrystal Plasticity Model for Mg Alloys
Authors: Choi Shi Hoon , Song Y.S. , Kim Jong Kweon , Jung B.J. , Park Yong Bum
Published: March 2009

Uniaxial compression tests on hot-rolled AZ31 Mg alloy were carried out at a temperature
of 300°C. In order to investigate work hardening and texture evolution during plastic deformation,
cylindrical specimens were compressed to the rolling direction. Experimental investigation reveals
that flow curves are strongly dependent on microstructure evolution such as deformation twinning
and softening phenomenon. The occurrence of deformation twinning and softening phenomenon was
revealed by the observation of microtexture using electron backscatter diffraction (EBSD). A
visco-plastic self-consistent (VPSC) polycrystal model was used to simulate the work hardening,
softening and texture evolution during the uniaxial compression. In order to calculate orientation of
deformation twins, predominant twin reorientation (PTR) scheme was implemented into the
polycrystal model. A softening scheme was also implemented in the polycrystal model to predict
softening phenomenon and texture evolution after a peak stress.
On the Validation of the Monte Carlo Technique in Simulation of Grain Growth in Small, Two-Dimensional Systems
Authors: Hunderi Ola , Marthinsen Knut , Ryum Nils
Published: March 2009

The kinetics of grain growth in real systems is influenced by several unknown factors, making a theoretical treatment very difficult. Idealized grain growth, assuming all grain boundaries to have the same energy and mobility (mobility M = k/ρ, where k is a constant and ρ is grain boundary curvature) can be treated theoretically, but the results obtained can only be compared to numerical grain growth simulations, as ideal grain growth scarcely exists in nature. The validity of the simulation techniques thus becomes of great importance. In the present investigation computer simulations of grain growth in two dimensions using Monte Carlo simulations and the grain boundary tracking technique have been investigated and compared in small grain systems, making it possible to follow the evolution of each grain in the system.
Numerical Modelling of Plastic Deformation and Subsequent Recrystallization in Polycrystalline Materials, Based on a Digital Material Framework
Authors: Logé Roland E. , Bernacki M. , Resk H. , Digonnet H. , Coupez T.
Published: March 2009

The development of a digital material framework is presented, allowing to build virtual microstructures in agreement with experimental data. The construction of the virtual material consists in building a multi-level Voronoï tessellation. A polycrystalline microstructure made of grains and sub-grains can be obtained in a random or deterministic way. A corresponding finite element mesh can be generated automatically in 3D, and used for the simulation of mechanical testing under large strain. In the examples shown in this work, the initial mesh was non uniform and anisotropic, taking into account the presence of interfaces between grains and sub-grains. Automatic remeshing was performed due to the large strains, and maintained the non uniform and anisotropic character of the mesh. A level set approach was used to follow the grain boundaries during the deformation. The grain constitutive law was either a viscoplastic power law, or a crystallographic formulation based on crystal plasticity. Stored energies and precise grain boundary network geometries were obtained directly from the deformed digital sample. This information was used for subsequent modelling of grain growth with the level set approach, on the same mesh.
Modeling Recrystallization of Aluminum Alloys: A Refined Approach to Particle Stimulated Nucleation
Authors: Schäfer C. , Gottstein Günter
Published: March 2009

A refined view of particle stimulated nucleation of recrystallization is presented, which utilizes a combination of advanced modeling tools. FEM simulations were carried out in order to model the evolution of the deformation zone around particles for various particle sizes and shapes. The results of these simulations were complemented by EBSD measurements to determine the number and orientation of nuclei. Finally, this information on particle stimulated nucleation was incorporated into a 3D cellular automaton recrystallization model CORe to model microstructure evolution. From these simulations the dependence of grain size and texture on particles size and shape was derived.
Effect of Grain Orientation on the Abnormal Grain Growth with Magetoplumbite Crystal Structure
Authors: Park Sang Yeup , Song Jun Ho , Cho Young Jin
Published: March 2009

The nucleation and growth behavior of magentoplombite has been observed during the abnormal grain growth in the presence of liquid phase. Abnormal grain growth was explained in terms of grain orientation due to liquid phase. It has been observed that the nuclei formation for abnormal grain growth was driven by the capillary force due to the liquid phase. Because magnetoplumbite crystal structure has an anisotropic crystal nature, abnormal grain growth with faceted grain shape was observed depending on its chemical composition. The formation of nuclei and particle orientation was important for the occurrence of abnormal grain growth.
The Processing of Ultrafine-Grained Materials Using High-Pressure Torsion
Authors: Xu Cheng , Horita Z. , Langdon Terence G.
Published: March 2009

It is now well-established that processing through the application of severe plastic deformation (SPD) leads to a significant reduction in the grain size of a wide range of metallic materials. This paper examines the fabrication of ultrafine-grained materials using high-pressure torsion (HPT) where this process is attractive because it leads to exceptional grain refinement with grain sizes that often lie in the nanometer or submicrometer ranges. Two aspects of HPT are examined. First, processing by HPT is usually confined to samples in the form of very thin disks but recent experiments demonstrate the potential for extending HPT also to bulk samples. Second, since the strains imposed in HPT vary with the distance from the center of the disk, it is important to examine the development of inhomogeneities in disk samples processed by HPT.
X-Ray Diffraction Studies of Grain Growth in an Ultra-fine Grained 6060 Aluminium Alloy
Authors: Forbord Børge , Mathiesen Ragnvald H. , Roven Hans Jørgen
Published: March 2009

In-situ synchrotron X-ray diffraction has been applied in order to study grain growth in an ultra-fine grained (D~400 nm) 6060 aluminium alloy at 270°C. The submicron grain structure was produced by Equal Channel Angular Pressing (ECAP) to an effective strain of ~6 without rotation of the billet. As the material was textured after ECAP, the initial stages of grain growth were seldom detected, but in the grain size interval available for studies a grain growth exponent of 3.6±0.3 was obtained. By interpolation of the grain growth curves to D=D0 (determined by EBSD) the effect of growth on the softening of the alloy was estimated. The interpolated average curve indicates that the initial stages of softening are not due to uniform grain growth, but rather reconfiguration and annihilation of dislocations as well as overaging of hardening precipitates.
Formation of Ultra Fine Grained Structure during Annealing of Heavily Drawn Metastable Austenitic Steel Wire
Authors: Fukumaru T. , Inoue T. , Tsuchiyama Toshihiro , Takaki Setsuo
Published: March 2009

It is well known that the ultra grain refinement can be achieved by sever cold rolling, followed
by reversion treatment in metastable austenitic stainless steel plate. In this study, the cold rolling was
replaced by cold drawing. This procedure was applied to a metastable austenitic steel (Fe-16Cr-10Ni
alloy) thin wire, and then the microstructure development during cold drawing and annealing was
investigated. The austenite phase transformed to martensite during the drawing. Vickers hardness of the
wire markedly increased with increasing the drawing strain. When the drawing strain reached about 4.5,
the wire exhibited martensite single structure and had high hardness of Hv4.4GPa. Annealing of the
heavily drawn wire at around 900K for 0.6ks leads to the formation of reversed austenite with the
diffusional reversion mechanism. As a result, ultra fine-grained austenitic single structure with the grain
size of about 0.6μm was obtained. It was also found that the wire has an excellent combination of a
strength and ductility.
Texture Evolution during Annealing of Warm Rolled Cr-Containing Low Carbon Steels
Authors: Pereloma Elena V. , Gazder Azdiar A. , Jonas John J. , Davies Chris H.J.
Published: March 2009

Two low carbon steels alloyed with 0.48wt% and 0.78wt% Cr were warm rolled to 65%
reduction at 640°C. Annealing was carried out at 710°C to achieve a range of recrystallized volume
fractions up to 100%. Texture analysis was performed by X-ray diffraction and Electron Back
Scattering Diffraction. During the initial stages of recrystallization, more recrystallized grains
nucleated at shear bands than at grain boundaries in the 0.48wt%Cr steel, whereas this was not the
case in the 0.78wt%Cr steel. This is associated with a decrease in the propensity to form shear
bands due to the lower amount of C in solid solution in the high-Cr steel. Additionally, the nuclei
showed a preference to develop the same fiber as the deformed region within which they nucleated.
In both steels, an increase in the annealing time led to the deterioration of the ND (or γ) –fiber and a
strengthening of both the RD (or α) –fiber and Goss component. In the fully recrystallized samples,
the ND component was somewhat stronger in the steel with the higher Cr content.
Effects of High Magnetic Field and Field Direction on Recrystallization and Recrystallization Texture in Cold-Rolled IF Steel Sheet
Authors: Wu Yan , He Chang Shu , Zhao Xiang , Zuo Liang , Watanabe T.
Published: March 2009

The effects of magnetic annealing on recrystallization and texture evolution in asannealed interstitial-free (IF) steel sheet were investigated by means of X-ray diffraction ODF analysis, SEM-EBSD analysis, and optical microstructure observation. During the magnetic annealing, specimens were placed at the center of the applied magnetic field, with their rolling planes parallel to the field direction (MD) and their rolling direction (RD) normal to the field direction (MD). It was found that the magnetic annealing retards the recrystallization process, but promotes the nucleation at the initial stage of recrystallization. Magnetic annealing did not change the mechanism of recrystallization texture evolution but improved the development of γ-fiber texture during the process of recrystallization, and the magnetically annealed specimen had stronger γ-fiber texture compared with the conventionally annealed specimen; this interesting finding is quite different from the previous work on magnetically annealed IF steel.
Application of FIB-EBSD Tomography for Understanding Annealing Phenomena in a Cold Rolled Particle-Containing Nickel Alloy
Authors: Xu Wan Qiang , Ferry Michael , Cairney Julie M. , Humphreys John F.
Published: March 2009

A typical dual-beam platform combines a focused ion beam (FIB) microscope with a field emission gun scanning electron microscope (FEGSEM). Using FIB-FEGSEM, it is possible to sequentially mill away > ~ 50 nm sections of a material by FIB and characterize, at high resolution, the crystallographic features of each new surface by electron backscatter diffraction (EBSD). The successive images can be combined to generate 3D crystallographic maps of the microstructure. A useful technique is described for FIB milling that allows the reliable reconstruction of 3D microstructures using EBSD. This serial sectioning technique was used to investigate the recrystallization behaviour of a particle-containing nickel alloy, which revealed a number of features of the recrystallizing grains that are not clearly evident in 2D EBSD micrographs such as clear evidence of particle stimulated nucleation (PSN) and twin formation and growth during PSN.
Grain Size in Mg Alloys: Recrystallization and Mechanical Consequences
Authors: Barnett Matthew R. , Atwell Dale , Beer Aiden G.
Published: March 2009

The present paper examines the development of grain size during the recrystallization of magnesium alloys and the influence the grain size has on the mechanical response. In magnesium alloys grain refinement improves the strength-ductility balance. This simultaneous increase in both strength and ductility is ascribed to the impact the grain size has on deformation twinning. The mechanisms by which the grain size is established during hot working are shown to be conventional dynamic recrystallization followed by post-dynamic recrystallization. The role of alloying addition on both of these reactions is briefly considered.
Effects of Precipitation during Dynamic Recrystallization of Copper with Different Oxygen Levels
Authors: García V.G. , Cabrera Jose María , Prado Jose Manuel
Published: March 2009

Previous research works assert that the observed increase in hot flow stress of commercially pure copper is attributed to the interactions between solute atoms and dislocations, specifically by interstitial oxygen. This work shows TEM images of the formation of Cu2O precipitates after warm working temperatures that in part help explain the increase of stress during hot compression of 99.9% pure copper. Three commercially pure large-grained coppers with 26, 46 and 62ppm of oxygen were tested at different temperatures (600°C-950°C) and strain rates (0.3s-1- 0.001s-1). At temperatures below 850°C, the stress differences between coppers, tested at same the strain rate, became increasingly higher. A correlation between stress increase and oxygen content was found. Precipitation of nanometric Cu2O did not show any difference in dynamically recrystallized grain size; however hardness tests showed that the final properties were modified. This work discusses the effect precipitation of Cu2O has on the hot flow curve and the final microstructure of hot formed 99.9% pure copper with different oxygen levels.
Orientation Distribution of Σ3 Grain Boundary Planes in Ni before and after Grain Boundary Engineering
Authors: Miller Herbert M. , Kim Chang Soo , Gruber Jason , Randle Valerie , Rohrer Gregory S.
Published: March 2009

The distribution of grain boundary plane orientations in polycrystalline Ni has been measured before and after grain boundary engineering. The grain boundary engineered microstructure has a relatively higher concentration of Σ3 grain boundaries and, when compared to the initial structure, more of these boundaries have orientations that are inclined by more than 10° from the (111) orientation of the ideal coherent twin. Although the conventionally measured grain size is not affected by the grain boundary engineering process, the average size of the regions containing only Σ3n grain boundaries increases by nearly a factor of two. The observations indicate that the increase in the relative population of Σ3 grain boundaries results both from the preferential elimination of random grain boundaries and the generation of new Σ3 grain boundaries which do not have (111) grain boundary plane orientations.
Limit for Controlling Stabilization of Cu Powder Prepared from Cu2o-H2O System
Authors: Hai Hoang Tri , Kim Dong Jin , Kim Y.D. , Kim Chong Oh , Chung Hun Saeng , Ahn Jong Gwan
Published: March 2009

Ultrafine dispersed copper powders were prepared from copper (I) oxide (Cu2O) slurry by a wet chemical reduction with hydrazine as a reductant. Palladium chloride (PdCl2) was used as a nucleator along with its polymer stabilizer, polyvinylpyrrolidone (PVP). Sodium pyrophosphate (Na4O7P2) was added as a surfactant. It was found that the use of Cu2O and Na4O7P2 exhibit very strong impact on dispersity of the prepared Cu powders. In this study, we indicate the critical conditions at which the particles aggregation still occurs even though the powders produced at high zeta potential resulted from an appropriate addition of Na4O7P2.
Cold-Rolled Micro-Texture in Polycrystalline 3%Si-Fe
Authors: Imamura Takeshi , Hayakawa Yasuyuki , Muraki Mineo
Published: March 2009

Cold-rolled micro-texture of polycrystalline 3%Si-Fe was investigated using high-resolution Electron BackScattering Patterns (EBSP) method. There were deformation bands near grain boundaries. The orientation relationship between the deformation bands and the surrounding deformed grains is explained by the orientation rotation around a <211> axis. The activated slip to generate these deformation bands is estimated from the <211> rotation. The S-value, which is a geometrical index of slip operation against applied stress, of this slip system was not maximum value of all, but it had a common slip plane with an adjacent grain. A hypothesis that the slip system having a common slip plane with an adjacent grain is activated was proposed from the present results.
A Novel Laser Powered Heating Stage for In Situ Investigations in a SEM
Authors: Kirch Dirk M. , Ziemons A. , Lischewski I. , Molodov Dmitri A. , Gottstein Günter
Published: March 2009

A novel high temperature heating method in combination with automated EBSD-data acquisition is presented. A commercially available infrared laser is utilized to heat samples up to a temperature of about 1000°C in high vacuum in a SEM while acquiring EBSD-data of the microstructure. First results on the γ-α-γ phase transformation between 840°C and 865°C in a microalloyed ferritic low carbon steel is presented.
In Situ Time-Resolved X-Ray Diffraction Investigation of the ω→ψ Transition in Al-Cu-Fe Quasicrystal-Forming Alloys
Authors: Otterstein E. , Nicula R. , Bednarčík J. , Stir M. , Burkel E.
Published: March 2009

Quasicrystals are aperiodic long-range ordered solids with a high potential for many modern applications. Interest is nowadays paid to the development of economically viable large-scale synthesis procedures of quasicrystalline materials involving solid-state transformations. The kinetics of the high-temperature phase transition from the complex ω-phase to the icosahedral quasicrystalline (iQC) ψ-phase in AlCuFe nanopowders was here examined by in-situ time-resolved X-ray diffraction experiments using synchrotron radiation. In-situ XRD experiments will allow insight on the influence of uniaxial applied pressure on the kinetics of phase transitions leading to the formation of single-phase QC nanopowders and further contribute to the optimization of sintering procedures for nano-quasicrystalline AlCuFe alloy powders.
Microstructure and Mechanical Properties of Al/Sicp Composites with Multimodal Size Distribution of Reinforcements
Authors: Montoya-Dávila Miguel , Pech-Canul Max A. , Pech-Canul Martin I.
Published: March 2009

The effect of particle size distribution and particle size ratio of SiCp in SiCp/SiO2
preforms on the microstructure, microhardness of SiCp reinforcements, modulus of rupture,
and superficial hardness of Al/SiCp composites produced by pressureless infiltration has been
investigated. SiCp/SiO2 preforms in the form of plates (4cm x 3cm x 0.5cm) have been
pressureless infiltrated by the alloy Al-15.52 Mg-13.62 Si (wt. %) at 1100 oC for 60 min
under inert atmosphere. SiC powders with average particle size of 10, 68 and 140 μm are
mixed with SiO2 powders and preforms of 40 % porosity with unimodal, bimodal and
trimodal size distributions are prepared by uniaxial compaction. The bimodal (small: large)
and trimodal (small: medium: large) preforms are prepared with different particle size ratios
in the following levels: 1:1, 3:1, 1:3, 2:2:2, 3:2:1, 3:1:2. Results from characterization by
XRD, SEM and energy dispersive X-ray spectrometry show that the typical microstructure of
the composites contains the MgAl2O4 (spinel), AlN and MgO phases formed during
processing as well as partially reacted silica, SiC, Si and Al. It is found that the density,
reinforcement microhardness, modulus of rupture and superficial hardness of the composites
increase all with wider particle size distribution. However, whilst the modulus of rupture is
mainly affected on going from unimodal and bimodal to trimodal distribution, superficial
hardness and microhardness are mostly influenced on going from unimodal to bimodal and
trimodal distribution.
The Role of Ti Inoculation of Al-Zn-Si Coating Alloys on the Formation of Intermetallic Compounds by Interaction with Solid Steel
Authors: García Felipe , Salinas-Rodríguez Armando , Nava-Vázquez Enrique
Published: March 2009

The reaction between solid steel and liquid Al-Zn-Si alloy leads to the formation of a
solid intermetallic interfacial layer. In the case of industrial Al-43.5Zn-1.5Si coated steel strips, the
thickness of the intermetallic layer is on average 1.35 μm and the kinetics of the reaction is
controlled by the effect of Si on Al and Fe diffusivities through the solid intermetallic layer. In this
paper it is shown that the thickness of the intermetallic interfacial layer decreases as the Si content
in the liquid alloy increases. EDXS microanalysis at the interface of industrial coated steel strips
shows that the interfacial intermetallic compounds are chemically similar to those formed in the
bulk of Al-43.5Zn-1.5Si liquid baths in continuous coating lines. Differential acid dissolution of the
coatings reveals that the intermetallic layer is not planar at the interface with the coating overlay
and is formed by grains of different size and chemical composition. Addition of minute quantities of
Ti to the Al-Zn-Si liquid alloy causes changes in the morphology of the intermetallic layer and an
overall refining of the microstructure.
Intensifying Smelting Synthesis Technique of 2500m3 Blast Furnace
Authors: Chu Bin , Xiao Yang , Tang Pei Hua
Published: March 2009

Based on the existing smelt condition, after exploring and practicing, 2500m3BF of the
Stainless Steel Branch of Baosteel procured breakthrough on the intensifying smelting. By
researching technologies of compounding many coke kinds for lessening the effect to the BF,
adjusting the proportion of each ore to optimize the structure of charging, increasing the gas using
ratio for cutting down fuel ratio, and taking low silicon smelting to optimize BF operation, the general
indicators in the top position among the same type blast furnaces in china.
Thermal Behavior of Electron Irradiation Defects in CZ-Si
Authors: Cui Hui Ying , Li Yang Xian , Chen Gui Feng , Cai Li Li , Zhao Ermin
Published: March 2009

Behavior of the irradiation defects after annealing in electron irradiation CZ-Si has been
studied by Four-Point Probe Measurement, Fourier Transform Infrared Absorption Spectrometer
(FTIR) and Optical Microscope. The resistivities of irradiated silicon would decline under annealed at
750°C, it is considered that the oxygen related defects which present donor state were produced after
annealed.
Mechanics of Asymmetric Rolling of Thin Strip with Effect of Work Roll Edge Contact
Authors: Jiang Zheng Yi , Xie Hai Bo , Yang L.M. , Zhu Hong Tao , Wei Dong Bin , Tieu A. Kiet
Published: March 2009

Asymmetric rolling of thin strip has become important due to a significant decrease of
rolling force, which contributes to obtain the extremely thin strip, to reduce the rolling passes, and
to save the energy by a decrease of anneal treatment. In asymmetric rolling of thin strip, edges of
work rolls may contact and deform when no or small work roll bending force is applied. Work roll
edge contact forms a new deformation feature. In this paper, the effects of initial thickness of strip
and friction coefficient on the rolling pressure, roll edge contact length and strip crown during
asymmetric rolling of thin strip with work roll edge contact effect has been discussed, and the
calculated rolling force with work roll edge contact is compared with the measured value.
Structural and Mechanical Properties of AlN Films by Pulsed Bias Arc Ion Plating
Authors: Zhang Min , Lin Guo Qiang , Wu Ai Min , Hao Sheng Zhi , Dong Chuang , Wen Li Shi
Published: March 2009

AlN thin films have been deposited on p-(100) Si and glass substrates by pulsed bias arc ion
plating at different negative substrate biases. The crystal orientation, deposition rate and mechanical
property of the films were investigated by X-ray diffraction, nanoindenter and UV-VIS
spectrophotometer. The results reveal that pulsed bias has a large influence on film preferred
orientation, deposition rate and mechanical property. A preferred (110) orientation is observed in the
film deposited at a bias of -50V. With the increase of the bias, film deposition rate decreases first
sharply then wildly; Film hardness and elastic modulus first increase, then decrease and finally
increases. Higher value of film harness obtained at the bias of -50V and -500V relates to the (110)
preferred orientation and grain refinement respectively.
Structural Evolution Upon Annealing of Multi-Layer Si/Fe Thin Films Prepared by Magnetron Sputtering
Authors: Li Xiao Na , Hu Bing , Dong Chuang , Jiang Xin
Published: March 2009

Fe/Si multi-layer films were fabricated on Si (100) substrates utilizing radio frequency
magnetron sputtering system. Si/β-FeSi2 structure was found in the films after the deposition.
Structural characterization of Fe-silicide sample was performed by transmission electron microscopy,
to explore the dependence of the microstructure of β-FeSi2 film on the preparation parameters. It was
found that β-FeSi2 particles were formed after the deposition without annealing, whose size is less
than 20nm ,with a direct band-gap of 0.94eV in room temperature. After annealing at 850°C, particles
grow lager, however the stability of thin films was still good.
Investigation of Mechanical and Structural Properties of AlN Thin Films Prepared by Mid-Frequency Pulsed Magnetron Sputtering
Authors: Mu Zong Xin , Wu Ai Min , Jia Li , Wang Zhen Wei , Zhao Hua Yu , Liu Shen Guang
Published: March 2009

In this work, we investigated the deposition of the AlN thin films on silicon (100)
substrates by mid-frequency pulsed magnetron sputtering of a metal Al target in an Ar-N2 gas
mixture at room temperature. The films were characterized by various means for the composition,
the crystal structure, the surface morphology, and the hardness and Young’s modulus. AFM surface
RMS (root mean square) roughness analysis revealed that the surface morphology has relation with
the nitrogen flow rate in the Ar–N2 gas mixture. The highest surface smoothness was observed at the
nitrogen flow rate of 30-50%. The phenomenon was interpreted by the action of the vapor-solid
interface on the film growth, as well as the nonequilibrium processes occurred in the film growth.
Electrical Properties and Microstructures of Ultraviolet Transparent Ga2O3 Thin Films
Authors: Shigetoshi Yasuhiro , Tsukimoto Susumu , Takeda Hidehisa , Ito Kazuhiro , Murakami Masanori
Published: March 2009

The electrical and optical properties, and microstructures of 100 nm-thick Ga2O3 films
fabricated on Al2O3(0001) substrates by a sputtering deposition were investigated. The partial
pressure of oxygen was controlled and the substrate temperature was kept to be 500 °C during
deposition. With increasing the oxygen partial pressure, the structures of the Ga2O3 films deposited
on the substrates were observed to change from amorphous to crystalline (monoclinic β-type Ga2O3).
The transmittance of the Ga2O3 films was measured to be more than 80 % at the visible and ultraviolet
regions although the electrical resistivity was high. In order to obtain both low electrical resistivity
and high transmittance at the ultraviolet regions, the addition of active dopant elements such as Sn
into the Ga2O3 films would be required.
Ultrasonic Properties of a Ti47.4Zr5.3Ni5.3Cu42 Glassy Alloy during Progressive Devitrification
Authors: Seki Ichiro , Fukuhara Mikio , Inoue Akihisa
Published: March 2009

Although a Ti47.4Zr5.3Ni5.3Cu42 glassy alloy does not occur precipitation of crystalline in
annealing of prolonged time below glass transition temperature, it shows slightly embrittlement
during passing through devitrification process. The embrittlment behavior may be connected to
structural relaxation. Using ultrasonic, in this study, acoustic characteristics of the glassy alloy during
progressive devitrification were examined in terms of structural relaxation. The structural changes
are characterized by decreases in specific volume, bulk modulus, Lamè parameter and Poisson ratio,
accompanied by structural relaxation.
Synthesis of New Ni-Ta-Based Bulk Glassy Alloy with High Fracture Strength of over 3000 MPa
Authors: Zhang Wei , Arai Kunio , Qiang J. , Qin C. , Jia F. , Inoue Akihisa
Published: March 2009

The addition of Ti and Zr to Ni-Ta binary alloys is effective for the increase in
stabilization of supercooled liquid and glass-forming ability (GFA). As the Ti content increases, the
supercooled liquid region Tx and reduced glass transition temperature (Tg/Tl) of Ni60Ta40-xTix
glassy alloys increase, show maximum values of 63 K at 20 at.%Ti and 0.589 at 25 at.%Ti,
respectively, and then gradually decrease. The addition of 5 at.% Zr to Ni-Ta-Ti alloys lowers
liquidus temperature (Tl), resulting in the higher Tg/Tl values of 0.600. The best GFA were obtained
for Ni60Ta15Ti20Zr5 and Ni60Ta20Ti15Zr5 alloys and the glassy alloy samples with a diameter of 1.0
mm were fabricated. The new Ni-Ta-based bulk glassy alloys exhibit high Tg of ~897 K, large ΔTx
of ~74 K, high strength of over 3180 MPa with plastic strains of ~0.4% and excellent corrosion
resistance in 1 N HCl solution.
Behavior and Preparation of Single Crystal of Cu-Al-Ni-Be SMA
Authors: Xu Hua Ping , Hu Hui , Song Gao Feng , Li Chong He , Mao Xie Min
Published: March 2009

In this paper, single crystal of CuAlNiBe shape memory alloy (SMA) was prepared
in a high temperature gradient directional solidification furnace with a selective growing
crystallizer. And its performance characters were systematically studied. The results show that
the mechanical and shape memory properties of the single crystal of CuAlNiBe SMA alloy has
much better than that of the polycrystalline material. This may be explained that the stress
concentration at grain boundary caused by the difference of bilateral strains is the dominant
reason of deterioration of fatigue properties; therefore single crystal alloy possesses the
excellent properties duo to its elimination of grain boundary.
Effect of Heat Treatment Temperature on the Mechanical Property in Cast TiNi Shape Memory Alloy
Authors: Kitamura Kazuhiro , Sawada Yutaka , Kuchida Toshio , Inaba Tadashi , Tokuda Masataka , Yoshimi Yukiharu
Published: March 2009

The heat treatment effect of a cast shape memory alloy (SMA) from self-propagating high
temperature synthesis (SHS) ingot was investigated. The composition of SHS ingot was
Ti-50.8at%Ni. DSC and Tensile test specimens were cast by lost-wax process from SHS ingot. The
heat treatment conditions were 400°C-60min., 500°C-60min. and 600°C-60min. for DSC and
400°C-60min. and 500°C-60min. for tensile test. Transformation temperatures were measured by
differential scanning calorimetry (DSC). Mechanical properties were measured by a tensile test at
several temperatures. The effects of heat treatment temperatures were same as a general TiNi wire
material.
Characterization of Intermetallic Phases and Planar Defects in Mg-Y-Zn Alloys
Authors: Zhu Yu Man , Morton A.J. , Nie Jian Feng
Published: March 2009

The structure of intermetallic phases and planar defects in the as-cast and the solutiontreated
microstructures of a Mg-8Y-2Zn-0.6Zr (wt%) alloy are characterized using transmission
electron microscopy. The alloy was produced by permanent mould casting and solution treated at
500 °C. It is found that the intermetallic particles in the as-cast microstructure have a monoclinic
structure. An appreciable amount of intermetallic particles is still retained along grain boundaries
after solution treatments for up to 60 hrs. However, the structure of the retained intermetallic
particles changes gradually from monoclinic to hexagonal during the solution treatments. Some
planar defects are also detected in the as-cast and the solution-treated (1 hr) microstructures. These
defects have characteristic features of stacking faults.
Nano-HA Coating on Titanium Surface Fabricated by Modulation of Self-Assembled Monolayer and Bovine Serum Albumin
Authors: Feng Bo , Liu A. , Wu N. , Weng Jie , Qu Shu Xin , Wang Jian Xin , Lu Xiong
Published: March 2009

Bone-like hydroxyapatite (HA) coatings were fabricated on titanium implants by a
self-assembled technique and biomimetic method. After titanium plates were oxidized in a mixture of
H2SO4/H2O2, a hexadecanoic acid self-assembled onto titanium surfaces. Contact angles of water and
tricresyl phosphate on the surfaces were measured to characterize the self-assembled monolayer
(SAM) and confirm the presence of the functional group. The titanium plates with SAM were used to
fabricate HA coatings. In the simulate body fluid (SBF) with and without bovine serum albumin
(BSA), Ca2+ and PO4
3- ions could spontaneously deposit onto the titanium surfaces and form
bone-like HA coatings. The morphology, component and structure of samples were examined by
scanning electronic microscopy, X-ray photoelectron spectroscopy, X-ray diffraction and attenuated
total reflection Fourier transform infrared spectroscopy. The results suggested that the SAM can
induce the formation of the nano-HA coating with a network and microporous structure. For the
biomimetical HA coating induced by HDA-SAM, BSA could modulate the growth of HA crystal and
decreased the grain size.
A Constitutive Equation Coupling the Grain Size during the High Temperature Deformation of Ti-6.62Al-5.14Sn-1.82Zr Alloy
Authors: Luo Jiao , Li Miao Quan , Hu Y.Q.
Published: March 2009

A constitutive equation has been established to describe the effect of grain size on the
deformation behavior of Ti-6.62Al-5.14Sn-1.82Zr alloy during the high temperature. In this paper,
firstly a steady flow stress model is proposed, and a function relating to the grain size is introduced
to modify the steady flow stress model. Meanwhile, a microstructure model established by the fuzzy
neural network method is applied to calculate the grain size of prior α phase during the high
temperature deformation of Ti-6.62Al-5.14Sn-1.82Zr alloy. The calculated flow stress using the
present constitutive equation shows a good agreement with the experimental flow stress of the
Ti-6.62Al-5.14Sn-1.82Zr alloy. The relative maximum error was not more than 15%.
A Molecular Dynamics Study of Helium-Vacancy Clusters Production due to Cascades in α-Iron
Authors: Yang Li , Zu Xiao Tao , Xiao Haiyan , Gao Fei , Wang X.Y. , Liu Ke Zhao
Published: March 2009

Molecular dynamics (MD) methods are utilized to study the displacement cascades in α-Fe
containing different concentrations of substitutional He atoms. Primary knock-on atom (PKA)
energies, Ep, from o.5 keV to 20 keV are considered at a temperature of 100 K and 600 K, and the
results are compared with those performed in pure α-Fe. There are distinct differences in the number
and size of defect clusters within displacement cascades with and without substitutional helium
atoms. Particularly, the number and size of helium-vacancy clusters generally increase with
increasing helium concentration and PKA energy. However, the number of He-vacancy (He-V)
clusters increases with increasing temperature, the mean size of He-V clusters is independent on
temperature for the same He concentration and energy recoils.
Influence of Extrusion Temperature on Microstructure, Texture and Fatigue Performance of AZ80 and ZK60 Magnesium Alloys
Authors: Shahzad Muhammad , Eliezer Dan , Gan Wei Min , Yi Sang Bong , Wagner Lothar
Published: March 2009

The wrought magnesium alloys AZ80 and ZK60 were extruded at 175°C ≤ T ≤ 350°C at
an extrusion ratio of ER = 12. With decreasing extrusion temperatures a marked refinement in grain
size was found for both alloys resulting in higher values of yield stress while UTS values were
hardly affected. As opposed to AZ80, a marked yield stress differential between loading in tension
and compression was observed in ZK60, this effect being explained by the differences in
crystallographic texture.
Modeling and Experimental Observation of the Plastic Anisotropy and Damage of CP-Ti during Multi-Pass ECAE
Authors: Jiang Hong , Fan Zhi Guo , Xie Chao Ying
Published: March 2009

In this paper, 3-dimension finite element model was applied to analyze the commercial
pure Ti billet subjected to four-pass equal channel angular extrusion process at 400°C with Bc route.
The effective strain distribution and the damage within up to four-pass were described with friction
conditions in 3D. The propensity for cracks was predicted, which did correlate approximately to the
experiment.