bluuebunny/crossref_metadata_2025 huggingface dataset:
Extremely Compact Half-Bridge SiC Power Modules Built into EV In-Wheel Motor
Authors: Tanimoto Satoshi , Hara Ayane , Yamashita Mari , Suzuki Tatsuhiro , Araki Sawa , Sato Shinji , Akatsu Kan
Published: June 2018

Full SiC half-bridge power modules (HPMs) applicable to a real electric vehicle 40-kW permanent magnetic in-wheel motor with an internal diameter of 159 mm have been designed, prototyped and characterized for the first time in the NEDO-SIP program. The prototyped HPMs are extremely compact in size at D35.7×W18.8×H8.0 mm and capable of withstanding junction temperatures up to nearly 200°C. Double-pulse tests revealed that the tested HPM showed steady switching behavior even at 600 V/160 A.
SiC JBS Diode Symmetrical Voltage Doubler Represented as the Diffusion-Welded Stack
Authors: Korolkov Oleg , Land Raul , Toompuu Jana , Sleptsuk Natalja , Rang Toomas
Published: June 2018

In the present work, the prototype of a voltage multiplier represented as the diffusion-welded stack is presented. Two options of multiplier prototypes are considered: the scheme with external capacitors and the multiplier of the vertical composition using the diode's own capacitance. Oscillograms of input and output signals for both multiplier composition are presented.
The Development of High Thermal Conductivity SiC Power Modules through the Implementation of Advanced Cooling Techniques Coupled with High Heat Transfer Materials
Authors: Passmore Brandon , McPherson Brice , Simco David , Lostetter Alex
Published: June 2018

This paper discusses Wolfspeed’s advances in silicon carbide (SiC) power module packaging, focusing on recent developments in advanced power module heat transfer techniques, the integration of pinfin mechanical structures, and the implementation of advanced die attach materials. Heat spreader materials and novel cooling methods suitable for SiC power modules are presented, focusing on the thermal heat transfer properties and a discussion of the design and prototype experimental impacts.
Design of SiC-Based DC-DC Converters for Future Offshore Wind Power Applications
Authors: Sommer Christian , Mertens Axel , Kortazar Itziar , Larrazabal Igor
Published: June 2018

This work is a contribution to the design of high-power DC-DC converters for future wind power applications by use of new semiconductors made of silicon carbide. First, the application is introduced, that is selected for high performance SiC devices. The design methodology is presented and validated with measurements of a physical prototype.
High In-Wafer Uniformity of Growth Rate and Carrier Concentration on n-Type 4H-SiC Epitaxial Films Achieved by High Speed Wafer Rotation Vertical CVD Tool
Authors: Daigo Yoshiaki , Ishiguro Akio , Ishii Shigeaki , Ito Hideki
Published: June 2018

In this study, influence of both Si/H2 ratio and C/Si ratio on growth rate uniformity and carrier concentration uniformity of n-type 4H-SiC epitaxial films grown by high speed wafer rotation vertical CVD tool was investigated. It was found that changes in radial profile of the growth rate and the carrier concentration obtained by varying Si/H2 ratio showed quite similar behavior to those obtained by varying C/Si ratio. Such a similar trend would suggest that the distribution of local C/Si ratio near the wafer surface changes depending on total Si/H2 ratio similarly to total C/Si ratio. Additionally, by using this relationship, both the growth rate uniformity of 49.2 μm/h ±1.78% (1.15% σ/mean) and carrier concentration uniformity of 1.08 ×1016cm-3 ±6.15% (3.40% σ/mean) was achieved.
Ab Initio Theory of Si-Vacancy Quantum Bits in 4H and 6H-SiC
Authors: Ivády Viktor , Davidsson Joel , Son Nguyen Tien , Ohshima Takeshi , Abrikosov Igor A. , Gali Ádám
Published: June 2018

Point defects in wide band gap semiconductors have recently shown outstanding potential for implementing room temperature quantum bits and single photon emitters. These atomic scale tools can be used in various quantum information processing, sensing, and imaging applications. Silicon vacancy related photoluminescence centers in 4H, 6H, and 15R-SiC are among the most studied quantum bits that possess a particular spin-3/2 ground and excited state. The microscopic structures of these defects have been recently identified as isolated negatively charged silicon vacancy defects at the symmetrically non-equivalent silicon sites in SiC. Relying on this identification, here we carry out high precision ab initio simulations on negatively charged silicon vacancies in 4H and 6H-SiC and calculate the most important magneto-optical data, such as the zero-phonon photoluminescence energies, the zero-field-splitting, and the hyperfine tensors for the nearest and farther nuclear spins.
Analytical Model for the Influence of the Gate-Voltage on the Forward Conduction Properties of the Body-Diode in SiC-MOSFETs
Authors: Huerner Andreas , Heckel Thomas , Endruschat Achim , Erlbacher Tobias , Bauer Anton J. , Frey Lothar
Published: June 2018

In this study, the influence of the gate-source voltage on the forward conduction properties of the body-diode in SiC-MOSFETs is demonstrated experimentally and analyzed by numerical simulations. Thereby, it can be figured out that the conduction properties of the body-diode strongly depend on the operational state of the MOS-capacitor. In depletion case, the current via the body-diode is dominant, whereby in accumulation and inversion mode the current mainly flows through the MOS-channel.
3C-SiС Hetero-Epitaxially Grown on Silicon Compliance Substrates and New 3C-SiС Substrates for Sustainable Wide-Band-Gap Power Devices (CHALLENGE)
Authors: La Via Francesco , Roccaforte Fabrizio , La Magna Antonino , Nipoti Roberta , Mancarella Fulvio , Wellmann Peter J. , Crippa Danilo , Mauceri Marco , Ward Peter , MIGLIO Leo , Zielinski Marcin , Schöner Adolf , Nejim Ahmed , Vivani Laura , Yakimova Rositza , Syväjärvi Mikael , Grosset Gregory , Torregrosa Frank , Jennings Michael , Mawby Philip  Andrew , Anzalone Ruggero , Coffa Salvo , Nagasawa Hiroyuki
Published: June 2018

The cubic polytype of SiC (3C-SiC) is the only one that can be grown on silicon substrate with the thickness required for targeted applications. Possibility to grow such layers has remained for a long period a real advantage in terms of scalability. Even the relatively narrow band-gap of 3C-SiC (2.3eV), which is often regarded as detrimental in comparison with other polytypes, can in fact be an advantage. However, the crystalline quality of 3C-SiC on silicon has to be improved in order to benefit from the intrinsic 3C-SiC properties. In this project new approaches for the reduction of defects will be used and new compliance substrates that can help to reduce the stress and the defect density at the same time will be explored. Numerical simulations will be applied to optimize growth conditions and reduce stress in the material. The structure of the final devices will be simulated using the appropriated numerical tools where new numerical model will be introduced to take into account the properties of the new material. Thanks to these simulations tools and the new material with low defect density, several devices that can work at high power and with low power consumption will be realized within the project.
Lateral GaN MISFETs Fabricated in Mg Ion Implanted Layer
Authors: Sugamata Kota , Tsuge Hirofumi , Ikeda Kiyoji , Yoshino Michitaka , Kuriyama Kazuo , Nakamura Tohru
Published: June 2018

This paper demonstrates ion implanted lateral GaN MISFETs using double ion implantation technology, which enables us to form Si ion implanted source/drain regions in Mg ion implanted p-well fabricated on free-standing GaN substrates. Maximum drain current of 39 mA/mm and maximum transconductance of 4.5 mS/mm for GaN MISFET with a gate length of 2 μm at an estimated Mg surface concentration of 2.2 × 1018 cm-3 were obtained. A threshold voltage was-0.5 V for the device. These results show that we successfully formed Si ion implanted n-type regions in the Mg ion-implanted layer and achieved innovative performance.
Improved Uniformity of Silicon Carbide Epitaxy Grown in a High-Volume Multi-Cassette Epitaxy Reactor
Authors: MacMillan Michael F. , Oldham Tim , Rengarajan V. , Wu Ping
Published: June 2018

We report on the results of a Design of Experiments (DOE) matrix of growth runs used to tune and improve the uniformity of thickness and doping across both 100 mm and 150 mm SiC epiwafers in our epitaxy reactor. Improvement of uniformity beyond the initial process recipe from the tool vendor is shown. Temperature measurement along an entire wafer platter indicate that there is a gas cold region extending into the growth zone that maybe the root cause of the non-uniformity.
High Quality AlN Single Crystal Substrates for AlGaN-Based Devices
Authors: Dalmau Rafael , Craft H. Spalding , Britt Jeffrey , Paisley Elizabeth , Moody Baxter , Guo Jian Qiu , Ji Yeon Jae , Raghothamachar Balaji , Dudley Michael , Schlesser Raoul
Published: June 2018

Aluminum nitride (AlN) single crystal boules were grown by physical vapor transport (PVT). Diameter expansion during boule growth, without the introduction of low angle grain boundaries (LAGB) around the boule periphery, was confirmed by crossed polarizer imaging, synchrotron white beam x-ray topography (SWBXT), and synchrotron monochromatic beam x-ray topography (SMBXT). The densities of basal plane dislocations (BPD) and threading edge dislocations (TED) averaged from high-magnification topographs of five regions of a high-quality substrate were 0 cm-2 and 992 cm-2, respectively. Substrates fabricated from AlN boules possessed excellent surface finishes suitable for epitaxy.
Addressing the Properties of Ultranano- and Microcrystalline CVD Diamond Films Grown on 4H-SiC Substrates
Authors: Fraga Mariana A. , Contin Andre , Savonov Graziela S. , Barbosa Divani C. , Pessoa Rodrigo S. , Trava Airoldi Vladimir J.
Published: June 2018

The growth of diamond films on different substrates has been studied extensively to support the emerging technologies ranging from mechanical to nano/microelectronics. It is known that the performance of these applications is affected by diamond film properties, such as structure and morphology. Using chemical vapor deposition (CVD) technique, we have deposited ultrananocrystalline diamond (UNCD) and microcrystalline diamond (MCD) films on 4H-SiC substrates and investigated their basic material properties. The understanding and exploitation of the material properties are fundamental to evaluate the potential of UNCD-on-SiC and MCD-on-SiC structures for fabrication of electronic devices and sensors.
Electrical Properties of Schottky-Diodes Based on B Doped Diamond
Authors: Erlbacher Tobias , Huerner Andreas , Zhu Yi Lin , Bach Linh , Schletz Andreas , Zuerbig Verena , Pinti L. , Kirste Lutz , Giese Christian , Nebel Christoph E. , Bauer Anton J. , Frey Lothar
Published: June 2018

Schottky diodes fabricated on free-standing B doped monocrystalline diamond substrate have been investigated. As expected, reverse leakage current due to Schottky barrier lowering has been observed due to the high electric field at the metal-semiconductor interface. Forward current is highest under operating temperatures between 400 and 450K due to incomplete ionization hole mobility dependence on temperature. It is demonstrated that the static device characteristics in the temperature range from 300K to 450K can be modelled by parametrizing an analytical introduced for unipolar SiC and Si diodes.
Analysis of ZrxSiyOz as High-k Dielectric for 4H-SiC MOSFETs
Authors: Cabello Maria , Varghese Aneesha , Montserrat Josep , Rebollo José , Decams Jean Manuel , Godignon Philippe
Published: June 2018

This paper deals with investigation and fabrication of 4H-SiC MOSFETs with a high-k dielectric close to ZrSiO4. We are looking for the optimal stochiometry in order to obtain full benefits of its large bandgap, a k value higher than that of SiO2, thermodynamic stability on SiC, a good interface quality and process compatibility with SiC technology. Several Si/Zr ratios have been tested with the purpose of obtaining the most favorable dielectric configuration. The first test devices have been manufactured successfully with a stack gate dielectric consisting of a thin SiO2 interlayer and a ZrxSiyOz (theoretical Si/Z=0.7) layer on top.
Electrochemical Formation of Porous Silicon Carbide for Micro-Device Applications
Authors: Gautier Gaёl , Defforge Thomas , Gommé Guillaume , Valente Damien , Alquier Daniel
Published: June 2018

Anodization of silicon carbide (SiC) in hydrofluoric acid (HF) solutions is a promising way to etch this material which is very resistant against traditional chemical etching methods. Moreover, it has been shown that several reproducible porous SiC morphologies can be performed varying anodization conditions (current density, electrolyte composition, UV lighting) and/or substrate properties (doping type and level). This paper proposes a state of the art of porous SiC etching in GREMAN and a presentation of the morphologies achievable using anodization in HF based electrolytes.
Design and Simulation of Bipolar 4H-SiC Memory Architecture for High Temperature Applications
Authors: Elgabra Hazem , Siddiqui Amna , Singh Shakti
Published: June 2018

The increasing demand for electronics in harsh environment applications has inspired investigation of silicon carbide (SiC)-based devices and circuits, due to its superior electrical properties. Several researchers have demonstrated the viability of 4H-SiC control circuitry by developing small scale logic circuits entirely in 4H-SiC. However, development and design of memory elements, which is a critical component in any electronic system, is still not fully explored. To bridge this gap, this paper presents, a complete bipolar, static random access memory (SRAM) column that includes the memory cell and the peripheral circuitry, designed to exploit the unique properties of SiC. Simulation results for the proposed memory show stable operation across a wide range of temperatures (27 °C – 500 °C) with good noise margins and access speeds while running at a supply voltage as low as 5 V. This work validates the potential of developing memory architectures in 4H-SiC, paving the way for realizing small-sized digital systems for harsh environments.
Electrical Characterization of Integrated 2-Input TTL NAND Gate at Elevated Temperature, Fabricated in Bipolar SiС-Technology
Authors: Shakir Muhammad , Elahipanah Hossein , Hedayati Raheleh , Zetterling Carl Mikael
Published: June 2018

This work presents the design and electrical characterization of in-house-fabricated 2-input NAND gate. The monolithic bipolar 2-input NAND gate employing transistor-transistor logic (TTL) is demonstrated in 4H-SiC and operates over a wide range of temperature and supply voltage.The fabricated circuit was characterized on the wafer by using a hot-chuck probe-station from 25 °C up to 500 °C. The circuit is also characterized over a wide range of voltage supply i.e. 11 to 20 V. The output-noise margin high (NMH) and output-noise margin low (NML) are also measured over a wide range of temperatures and supply voltages using voltage transfer characteristics (VTC). The transient response was measured by applying two square waves of, 5 kHz and 10 kHz. It is demonstrated that the dynamic parameters of the circuit are temperature dependent. The 2-input TTL NAND gate consumes 20 mW at 500 °C and 15 V.
Inclusion of Body Bias Effect in SPICE Modeling of 4H-SiC Integrated Circuit Resistors
Authors: Neudeck Philip G.
Published: June 2018

The DC electrical behavior of n-type 4H-SiC resistors used for realizing 500 °C durable integrated circuits (ICs) is studied as a function of substrate bias and temperature. Improved fidelity electrical simulation is described using SPICE NMOS model to simulate resistor substrate body bias effect that is absent from the SPICE semiconductor resistor model.
High Temperature Behavior Prediction Techniques for Non-Uniform Ni/SiC Schottky Diodes
Authors: Pristavu Gheorghe , Brezeanu Gheorghe , Badila Marian , Draghici Florin , Pascu Razvan , Craciunoiu Florea , Rusu Ion , Pribeanu Adriana
Published: June 2018

Two characterization methods are compared in terms of their suitability for predicting the electrical behavior of non-uniform Ni/4H-SiC Schottky contacts up to 450°C, using data measured at lower temperatures. These techniques are based on the established Gaussian distribution of barrier heights model and a recently proposed discrete barrier distribution model, respectively. Two samples with different degrees of contact inhomogeneity are measured and their forward characteristics are fitted using both techniques. The Gaussian distribution approach is shown to accurately fit experimental data only for the nearly-uniform sample, while requiring the extraction of two separate barrier height values from measurements in the room-250°C range, only. When attempting to use this method to characterize the sample with strong non-uniformity, fitting accuracy (given by R2) drops under 90%. In contrast, the discrete barrier distribution technique is proven able to forecast the electrical behavior of both samples (with R2 > 99% in most cases), over the entire room-450°C range, using a single Schottky barrier for each device (1.61V, corresponding to a Ni2Si Schottky contact and 0.9V, afferent to a Ni metallization).
Complementary p-Channel and n-Channel SiC MOSFETs for CMOS Integration
Authors: Soler Victor , Cabello Maria , Banu Viorel , Montserrat Josep , Rebollo José , Godignon Philippe
Published: June 2018

The fabrication of CMOS devices in SiC is important for both a higher operating temperature capability and the integration with SiC power devices. In this work, n-channel and p-channel signal MOSFETs have been successfully fabricated using a process technology fully compatible with our HV SiC VDMOS technology. A preliminary SiC CMOS inverter has been also integrated. The gate oxide configuration includes the use of Boron to improve SiO2/SiC. Electrical characterizations have been carried out at room temperature and a summary of the results is presented. The biggest challenge is to balance the n-type and p-type MOSFETs not only in area but also in Vth value.
An Improved I-V Model of GaN HEMT for High Temperature Applications
Authors: Yang Jie , Jia Ye Ting , Ye Ning , Yuan Zhen Yu , Shen Hong Yuan , Di Jia
Published: June 2018

The lack of the high temperature I-V model greatly restricts the application of GaN HEMT devices. In this paper, the characteristic variation of GaN HEMT device under high temperature condition is investigated, and an improved I-V characteristics model of GaN HEMT transistors over a wide temperature range from 25°C to 300°C is proposed based on the classic Statz model. The experimental results indicate that the improved spice model, by taking the self-heating effect into account, is more accurate compared to the original Statz model. The proposed I-V model should be an available tool for the simulation of GaN HEMT device in designing integrated circuits at high temperature.
High Current Silicon Carbide Diodes as Dose Detectors for Hard X-Rays
Authors: Pereira Nino R. , Hobart Karl D. , Koehler Andrew D. , Anderson Travis J. , Weber Bruce V. , Zier Jacob C. , Engelbrecht Joseph T.
Published: June 2018

The small community of physicists concerned with flash x-rays, short pulses of intense hard bremsstrahlung with photon energies exceeding hundreds of keV, is always on the lookout for new detector materials and protocols to diagnose such radiation pulses. Important parameters for the detector include rise time, sensitivity, size and cost. Silicon carbide has many of the right material properties for such a detector. In the exploratory test reported here, a high voltage SiC diode performe quite well, which suggests that success can be expected from a more extensive program that would find out what SiC is capable of in this application.
Evolution of the Macrostructure of Gray Cast Iron from Eutectic to Hypereutectic Composition
Authors: López Marcos , Massone Juan M. , Boeri Roberto Enrique
Published: June 2018

This work studies the evolution of the macrostructure of gray cast iron as the carbon equivalent (CE) increases from near-eutectic to highly hypereutectic values. The macrostructure of spherical samples of flake graphite irons of CE ranging between 4.24% and 5.23% was revealed by using direct austempering after solidification technique (DAAS). The results were analysed by applying the concept of coupled zone for gray cast irons. The coupled zone is a region in the stable Fe-C-Si diagram in which solidification proceeds as a cooperative growth of both austenite and flake graphite. The coupled zone for gray cast iron is claimed to be asymmetrical as the eutectic reaction is extended towards the prolongation of the austenite liquidus line. All the samples investigated in the present study show the presence of relatively large austenite grains, demonstrating that the number of active nucleation sites of austenite per unit volume is small. The observation of the microstructure shows the presence of several units of coupled growth inside each austenite grain, what proves that many eutectic colonies have grown from the same austenite nucleus, even for highly hypereutectic compositions. Colour etching was employed to reveal the “hidden” dendrites present in the microstructure. The results suggest that proeutectic graphite is not a good nucleating agent for austenite. These results contribute to the understanding of the solidification of hypereutectic gray irons and verify the earlier understanding of the solidification of eutectic gray irons and its extension to hypereutectic compositions.
Revisiting Models for Spheroidal Graphite Growth
Authors: Bjerre Mathias Karsten , Azeem Mohammed , Lee Peter D. , Hattel Jesper Henri , Tiedje Niels Skat
Published: June 2018

Recent experiments resolved nucleation and growth of graphite during solidification of ductile cast iron in 4D using synchrotron X-ray tomography. A numerical model for microstructure formation during solidification is compared with the experiments. Despite very good overall agreement between observations of spheroidal graphite growth and model results, significant deviations exist towards the end of solidification. We use the experimental observations to analyse the relation between graphite growth rate and the state of the particle neighbourhood to pinpoint possible links between growth rate of individual graphite spheres and the overall solidification state. With this insight we revisit existing models for growth of spheroidal graphite and discuss possible modifications in order to correctly describe the critical final stage of solidification.
Effect of Cooling Rate on the Eutectoid Transformation in Compacted Graphite Cast Iron
Authors: Lacaze Jacques , Thébault Yannick , Freulon Alexandre , Guesser Wilson Luiz
Published: June 2018

Differential thermal analysis has been used to characterize the effect of cooling rate on the eutectoid transformation of a compacted graphite iron. The samples were machined out from an as-cast thermal cup, austenitized at 950°C and then cooled to room temperature at various rates within the range 1−55.5°C/min. It was found that even at the highest investigated cooling rate, significant amounts of ferrite could be observed. When comparing the microstructure before and after Nital etching on samples cooled at intermediate cooling rates, it appeared that ferrite formed preferentially along the worms. This is discussed in terms of graphite shape and microsegregation and this latter seems prevalent. Finally, analysis of the thermal records was performed to characterize the temperatures for the start of the stable and metastable eutectoid reactions which confirms the eutectoid transformation sets up in compacted graphite irons as in lamellar and spheroidal graphite irons.
High Strain Rate Dynamic Deformation of ADI
Authors: Myszka Dawid , Ahmed Mostafa , Nofal Adel , Skołek Emilia , Hussein Abdelhamid
Published: June 2018

Engineering materials used in numerous applications, particularly in automotive crash loading and military ballistic purposes have to meet new demands, one of which is the resistance to dynamic loading. As the phenomena associated with such interaction is rather complex, non-static types of tests are applied to evaluate and compare between different potential materials. In this Work, different grades of ADI were produced under different austenitizing and austempering conditions different ausferrite morphologies. The effect of alloying elements such as Cu and Mo on the initial microstructure of the ductile iron was also studied. The initial amount of retained austenite was subjected to different dynamic strain rates. The hardness and strain induced martensitic transformation as a function of the microstructure and strain rate were evaluated. Extensive use of XRD and SEM was made to evaluate the high strain rate properties of the investigated grades.
Effect of Hot Working Parameters on Microstructure Evolution and Mechanical Properties of Ausformed Austempered Ductile Iron
Authors: Soliman Mohamed , Nofal Adel , Palkowski Heinz
Published: June 2018

Three ductile irons with different aluminum-and manganese-content were subjected to two thermo-mechanical schedules. In the first schedule, a total deformation of φt= 0.3 is applied on the ductile irons in the austenitic region before the austempering process. In the second schedule, the materials are subjected to deformation of 0.2 in the austenitic region and deformation of 0.1 during austempering (ausforming). Mechanical deformation of austenite prior to the transformation “stage I” pronouncedly accelerated the transformation due to increasing the nucleation sites of ausferrite. This increase has its impact on enhancing the microstructural uniformity and refining the ausferrite platelets. On the other hand, the retained austenite content was not significantly affected by the applied ausforming. Remarkable increase in hardness, strength and ductility of the ausformed ductile iron due to the latter effects is observed.
A Fatigue and Fracture Study on High Strength Cast Irons
Authors: Guesser Wilson Luiz , Guedes Luis Carlos , Müller Ailton L. , Demetrio Vagner B. , Rabelo Alexsandro
Published: June 2018

Fatigue strength and fracture of high strength cast irons, gray iron grade 300 and CGI grade 450, used for producing lightweight cylinder blocks, were studied. The results show endurance ratios of 0.27-0.28 and 0.38 for gray irons and CGI, respectively. The fracture surfaces in cast irons in general show the predominance of graphite and graphite/matrix interface; however, in CGI there is a larger proportion of fractured pearlitic matrix than in gray iron. This fact, and the differences in the morphology of the graphite/matrix interface, flat in gray iron, rough in CGI, explain the higher results of fatigue strength in CGI compared to gray iron. The results of fatigue strength are compared with the literature and with previous works.
Residual Stresses in Cast Iron Components - Simulated Results Verified by Experimental Measurements
Authors: Elmquist Lennart , Brehmer Aron , Schmidt Pål , Israelsson Björn
Published: June 2018

The aim of this work was to investigate how accurately residual stresses can be simulated in a cast component. The reason why this is important is that a simulation that also considers residual stresses can be used to design cast components more weight-and cost-efficient. The verification was done by comparing simulated results with physical measurements on cylinders made of ductile iron. The measurements were performed with two methods, sectioning and hole-drilling. These methods were applied on both as-cast and machined cylinders. The simulations were based on process data from casting trials and material data from the simulation software database. The material data for the heat conductivity of the molding sand was fitted to get a good conformity between measured and simulated temperatures. This was done to ensure that the residual stress simulation used a relevant temperature history. It turned out that the simulation was in good agreement with results from the sectioning measurements of the axial stress while results from the hole-drilling measurements were contradictive. These results were contradictive for both as-cast and machined cylinders. It can therefore be concluded that residual stresses measured by the sectioning method resulted in good conformity with the simulated σzstresses. It was also concluded that the feeders, acting as extra heat sources, affects residual stresses locally and contributes to differences in stresses beneath the feeders, compared to corresponding areas between the feeders. It was also found that the resolution of the mesh needs to be finer to take into account changes in the stresses with increments in depth when using hole drilling method.
Plastic Deformation and Creep of Two Ductile Cast Irons, SiMo51 and SiMo1000, during Thermal Cycling with Large Strains
Authors: Öberg Christian , Zhu Bao Hua , Jonsson Stefan
Published: June 2018

Cyclic deformations of two ferritic, ductile cast irons, SiMo51 and SiMo1000, were studied in air and Ar using a new method, SRTC (stress relaxation with thermal cycling). Locked specimens were thermally cycled up to 800°C with isothermal holds, varying temperature interval, heating/cooling rates and hold times. A description of the mechanical response to thermal cycling of a locked specimen is given.
High-Temperature Corrosion-Fatigue Behavior of Ductile Cast Irons for Exhaust Manifolds Applications
Authors: Xiang Sheng Mei , Zhu Bao Hua , Jonsson Stefan
Published: June 2018

In the present study, low-cycle fatigue (LCF) tests and oxidation tests in controlled atmospheres are carried out at 800°C on two ductile cast irons SiMo51 and SiMo1000. The LCF tests are carried out in argon and synthetic exhaust gas, whereas oxidation tests are carried out in the latter atmosphere. S-N curves and weight-gain curves are presented. The crack growth mechanisms and oxidation mechanisms are investigated, as well as the synergetic effects. A surprising finding of increased fatigue resistance in oxidizing atmosphere is partly explained.
High Temperature Strength of Cast Irons for Cylinder Heads
Authors: Guesser Wilson Luiz , Cabezas Carlos S. , Guedes Luis Carlos , Zanatta André M.
Published: June 2018

Hot strength and fracture mechanisms in high quality cast irons were studied, comparing the standard gray iron Grade 300, alloyed with Mo, typically used for cylinder heads in high power engines, with other two materials: one gray iron Grade 300, obtained through graphite refinement and one compacted graphite iron, Grade 450. In these last two materials, the strength increase was obtained by changing the graphite structure, not by hardening the matrix. The experimental results with tensile tests carried out up to 500 °C show that the different strengthening mechanisms, use of Mo or modification of the graphite structure, are both efficient for increasing the strength at room temperature as well as at high temperatures. The CGI has a lower strength reduction with temperature than the gray irons, which shows the significant impact of the compacted graphite shape in reducing the notch effect. These results show the enormous potential of CGI in cylinder heads for high-performance engines.
Effect of C Content on High Temperature Erosive Wear Characteristics of Fe-Based V Containing Multi-Component Cast Steel with Ni
Authors: Shimizu Kazumichi , Kusumoto Kenta , Nakamura Kimitoshi , Kiguchi Shoji , Shirai Masato , Ito Jun
Published: June 2018

Hot hardness and oxidation property of target material influences greatly on the erosion behavior at elevated temperature. The correlation between hot hardness and oxidation property of multi component white cast irons and its erosion resistance were investigated, and try to estimate the high temperature erosion behavior in the study. Nine kinds of multi component white cast iron and cast steel were used in this study. Specimen were machined into a flat plate with dimension of 50×50×10 mm. High temperature erosion test machine was used to investigate the erosive wear property of experimental materials at 1173K. Alumina grits (average diameter: 1.16 mm, hardness: 1250 HV1) which were used as impact particles were heated to 1073K and shoot on the heated specimen by hot air at the velocity of 100 m/s. The total particle loading was 2 kg. In order to clarify the correlation of hot hardness, oxidation property and the erosion resistance of specimens, hot hardness test was carried out specimens, to estimate erosion damage caused by solid particle. Hot hardness of specimens showed a value comparable to 200～250HV1. Result of erosion and oxidation tests, erosion rate and amount of oxidation of the specimen were suppressed by Ni addition. It suggested that the more amount of Ni contents, the lower the erosion rate and the less the amount of oxidation.
Effect of the Cooling Rate on the Graphite Nodule Count and Size Distribution in Nodular Cast Iron
Authors: Muhmond Haji Muhammad , Fredriksson Hasse
Published: June 2018

The graphite nodule count, size distribution and homogenization of the nodules distribution are the factor which are of more significance for the properties of the material. By just increasing the inoculants or Mg will not help to get rid of problems like the un-even size distribution and or increasing the nodule count. The cooling conditions of the melt prior to solidification and during solidification can control these two parameters to a large extent. In this research, it is more emphasized on the nucleation sequence of MgO particles and on the cooling rates. The nucleation of MgO at different temperatures and at different cooling rates was found to have a great influence on the nodule size distribution and the homogenization of the microstructure. A mathematical model was derived to relate the Mg concentration in the liquid to the cooling rate, prior to solidification. The MgO particles count was calculated as a function of cooling rate. It was found that at higher cooling rates, MgO can be nucleated in multi steps during cooling process, which can increase the nodule count tremendously.
Residual Stresses around Individual Graphite Nodules in Ductile Iron: Impact on the Tensile Mechanical Properties
Authors: Andriollo Tito , Thorborg Jesper , Tiedje Niels Skat , Hattel Jesper Henri
Published: June 2018

Residual stresses in ferritic ductile iron castings have been studied for decades. However, little attention has traditionally been given to the local residual stresses which may arise in the microstructure as a result of the thermal contraction mismatch between the matrix and the graphite nodules during solid-state cooling. Recent synchrotron X-ray measurements performed by the authors have demonstrated that in the ferritic phase these local stresses can be in the order of 100-150 MPa, hence of the same order of magnitude as the material macroscopic yield stress. This suggests that they might have a significant influence on the mechanical properties of ductile iron components. However, no systematic research appears to have been conducted so far to investigate this aspect. The present work takes a first step in this direction by presenting an integrated theoretical analysis which addresses both the formation of these local residual stresses at the microscopic level and their role during mechanical loading at the macro-scale.
Pressing Control Design Based on Analysis of Metal Temperature and Flow in Sand Mold Press Casting
Authors: Tasaki Ryosuke , Seno Hideto , Hashimoto Kunihiro , Terashima Kazuhiko
Published: June 2018

The sand mold press casting method is a novel iron casting process, which has developed by our group in recent years. The proposed method can cast iron into complex shapes with a high yield over 90% and produces high-quality products by filling control of molten metal during pressing motion. However, molten metal inside mold is cooled down by heat transfer to the molds and atmosphere, and often causes solidification before the end of press. Then, the pressing movement of the upper mold is blocked by the solidified metal. Therefore, to avoid the solidification during pressing sand mold, metal temperature must be heated properly to estimate the filling temperature decrease behavior based on analysis results of CFD simulator, FLOW-3D. The necessary condition not to solidify molten metal before the end of press has been found. It was made clear that the mold must be heated up to the necessary temperature beforehand in the pressing process. Furthermore, optimum velocity reference with specified pressure constraints has been designed to prevent casting defect such as penetration and also to minimize the temperature decrease. In this paper, optimum velocity control of servo cylinder considering the both of allowable pressure of molten metal and starting time of solidification is proposed by using a theoretical approach of Model Predictive Control: MPC method. The effectiveness of the proposed control system has been demonstrated by computer simulation and experiments using a laboratory scale machine with molten metal of casting iron.
New Possibilities with Improved Green Sand Testing Equipment
Authors: Kerber Hubert , Jakesch Philipp , Schindelbacher Gerhard , Schumacher Peter
Published: June 2018

The quality of green sand moulds is paramount for the casting quality and reduction of surface defects. The general knowledge within foundries on green sand properties and its influence on casting defect behaviour has significantly decreased as a result of outsourced external sand testing and dependence on external consultants. Moreover, academic R&D activities targeting studies on green sand properties could not attract significant funding and have hence been limited to small extents. It cannot be stressed enough that in sand casting the majority of casting defects can be related to an insufficient green sand management. Recent research and development has been only supported by suppliers of the foundry industry, however, with a major emphasis on anorganic water glass binder systems and the reduction of phenolic binders in organic binders to reduce emission and unpleasant smells while simultaneously increasing e.g. fluidity or strength. In most industrial environments hand-operated sand testing machines, whose basic concepts of operation were developed in the middle of the last century, are still used. While these old fashioned apparatuses can help to maintain quality in a foundry they are not suited to provide additional information on the green sand quality. Therefore, any developments on different mould materials were mainly performed with very old fashioned manually operated sand testing equipment and a significant aspect of the development of more accurate modern sand testing equipment was neglected. Nevertheless, these manually operated sand testing apparatuses represent the current state-of-the-art of sand testing equipment. In order to improve green sand properties and gain additional knowledge it is essential to develop new testing methods. This paper will give information on the development of novel green sand testing equipment for compaction, pressure, as well as wet strength testing development at the ÖGI and gives comparison to values obtained by manually operated machines. The main advantage of modern electronical testing machines is a higher accuracy of measurement in general and the possibility of recording stress-strain-curves. This work shows characteristic stress-strain-curves for all mechanical green sand testing methods as well as the influence of water content on the progression of mechanical properties. As a result the area with the best handling properties of green sand is shown. Furthermore negative influences of defective sand specimens and marginal deviations in the testing process on the testing result have been investigated.
Degenerated Graphite Growth in Ductile Iron
Authors: Tonn Babette , Lacaze Jacques , Duwe Stephanie
Published: June 2018

As part of a study devoted to the effect of trace elements on graphite degeneracy, near-eutectic ductile iron melts were prepared to which minute amounts of lead and of both lead and cerium were added. The melts were cast into an insulated Y4 mould, giving a solidification time of about 1 hour and a cooling time to room temperature of about 15 hours. In the thermal centre of the Pb containing sample graphite spheroids as well as intergranular lamellar graphite have been found. At the same location of the casting containing both Pb and Ce, exploded as well as chunky graphite could be observed, while the formation of intergranular lamellar graphite has been suppressed. Deep etching of the samples allowed reaching the following conclusions: i) intergranular graphite in the SG-Pb sample often, if not always, originates on graphite nodules and extends towards the last to freeze areas; ii) in one location of the SG-PbCe sample, chunky graphite strings were observed to originate on an exploded nodule, thus confirming the close relationship between these two forms of graphite. Because of the over-treatment in cerium of the SG-PbCe sample, other unusual degenerate graphite was observed which appears as coarse aggregates of "porous" graphite after deep etching.
Effect of Si and Ni Addition on Graphite Morphology in Heavy-Section Spheroidal Graphite Iron Parts
Authors: Bauer Branko , Mihalic Pokopec Ivana , Petrič Mitja , Mrvar Primož
Published: June 2018

Metallographic analysis is applied to the study of the chunky graphite morphology in heavy-section castings of spheroidal graphite cast irons. Three castings with different Si and Ni content were prepared. Three positions in casting from the edge to the centre, with different cooling rates, were chosen for microstructure observation. The effect of the Si and Ni content on the graphite morphology and mechanical properties of heavy-section spheroidal graphite cast iron parts were investigated. Cerium containing commercial inoculant was used for in-stream inoculation. Chunky graphite area was estimated in micro-and macrostructure. Mechanical properties were determined on tensile test bars taken from the centre of the casting. Macro-and microstructure examination showed that the castings with high Si-content and Ni addition had chunky graphite present, while the castings produced by use of low Si and Ni containing charge had no chunky graphite. High Si-content is strong chunky graphite promoter, especially in castings with slow cooling rate. Ni addition also promotes chunky graphite formation, but only in thermal centre of the casting (where the cooling rate is the lowest). The elongation is severely lowered when chunky graphite appears in the microstructure.
The Influence of Trace Elements on the Nature of the Nuclei of the Graphite in Ductile Iron
Authors: Alonso Gorka , Ştefănescu Doru Michael , de La Fuente Esther , Larrañaga Pello , Suárez Ramón
Published: June 2018

Nucleation mechanisms and the effect of minor elements added with the inoculants are still a subject of extensive research in ductile iron. Oxides, sulfides, silicates and nitrides have been reported to be nuclei for graphite precipitation. Those compounds originate both from the nodulizing treatment and the inoculation process. Previous research works have shown that titanium nitrides or carbonitrides play an active role in graphite nucleation. In order to determine the efficiency and nature of nitrides that can act as nuclei for graphite, and the possible effect of the trace elements added with the inoculant, melts with titanium contents ranging from 0.007% to 0.036% were produced and poured into standard thermal analysis cups, with and without inoculation. Different inoculants rich in titanium, cerium, aluminum or zirconium were used. Two cups were produced with each inoculant, one cooled down to room temperature, and the other quenched in brine immediately after pouring. Nucleation sites were characterized through detector, spectrum, mapping and line scans of a FEG-SEM equipment. Most of the analyzed nuclei exhibited two or three different inclusions: magnesium sulfides or Mg-Ca oxy-sulfides, Mg or Al oxides, and Ti carbo-nitrides or Mg-Si-Al nitrides. The appearance of each type of nitrides is directly related to the titanium content in the base melt. When titanium was added in the inoculant, no titanium nitrides were noticeable. The zirconium added with the inoculant promoted more complex nitrides that appeared in higher amount. Cerium appears occasionally forming sulfides. Aluminum stimulates the formation of complex nitrides. No differences in the nature of the nuclei were observed between the samples quenched and the ones obtained at room temperature, which assures the methodology approach.
Stereological Analysis of the Statistical Distribution of the Size of Graphite Nodules in DI
Authors: Burbelko Andriy A. , Gurgul Daniel , Guzik Edward , Kapturkiewicz Wojciech
Published: June 2018

The estimate of a distribution law of the nodule diameters in a volume of cast iron provides information about the graphite nucleation kinetics, and also about the crystallization kinetics. This information is essential for building more accurate mathematical models of the alloy crystallization. The mapping of a Cumulative Distribution Function (CDF3) of radii for graphite nodules in ductile iron is presented on the base of a Probability Density Function (PDF1) of the chord length distribution for random sections of the sample at the planar cross-section.
Preliminary Study on Deformation and Recrystallization Behavior of Pure Tin for Mitigation of Whisker Growth
Authors: Kuwano Noriyuki , Binti Lias Marina , Binti Nordin Nur Azmah , Soejima Youhei , bin Nayan Ahmad Rafiqan
Published: June 2018

Since the mechanism of Sn-whisker growth is closely related with the behavior of deformation and recrystallization, understanding of the behavior is very important to establish the measure for mitigation of whisker growth. In this work, microstructural changes after heavy deformation by scratching were characterized by EBSD for a single crystal of β-Sn, and the following results were obtained. Three types of crystal grains appear immediately after the deformation; small grains in aggregation, large serrated grains and rim-grains. The small grains are considered to be formed by dynamic recrystallization. They continue to grow at a room temperature over a lengthy period of time. The large grain has a certain crystallographic relationship with the matrix where <100> axes of the large grain and the matrix are almost parallel to each other. The serrated boundaries of large grain are so stable that the large grain does not show a grain growth process. The stable boundary is considered to promote a continuous growth of whiskers.
Evaluation of ICP-OES Method for Heavy Metal and Metalloids Determination in Sterile Dump Material
Authors: Ilieva Darya , Surleva Andriana , Murariu Manuela , Drochioiu Gabi , Abdullah Mohd Mustafa Al Bakri
Published: June 2018

This study is aimed at development of an analytical method for the determination of heavy metals and arsenicin waste material from barite recovery by dual view inductively coupled plasma optical emission spectrometry (ICP-OES) after wet digestion. Aquaregia open digestion method was used for sample preparation. A soil certified reference material was used to study the efficiency of wet digestion procedure applied to sterile dump material. The sensitivity, accuracy, and precision of the method were determined. The achieved detection limits are: Arsenic (As) 0.80; Copper (Cu) 0.29; Lead (Pb) 0.29; Zink (Zn) 0.30; Cadmium (Cd) 0.11; Chromium (Cr) 0.09; Nickel (Ni) 0.02, mg.kg-1.The developed method is applied for the determination of hazardous metals and arsenic in sterile dump material from closed barite mine in the region of Tarnita-Suceava, Romania.