bluuebunny/crossref_metadata_2025 huggingface dataset:
Steel Production Technology Development for the Manufacture of Pipes Used in the Extraction and Transportation of Petroleum Products
Authors: Ogoltcov Alexey , Mitrofanov Artem V.
Published: January 2021

The technology has been developed for the production of low-carbon and microalloyed steel for the production of strips in order to manufacture small and medium-diameter pipes for the extraction and transportation of petroleum products. The developed technology allows to obtain stable corrosion properties, according to the NACE Standard TM 0284 technique, in a hot-rolled condition from slab with thickness more than 200 mm and with a content of more than 0.03% of carbon, which is very difficult in terms of ensuring the availability of inclusions and heterogeneity in the structure - as the main reasons for the reduced fracture toughness of steels working in acid media (in environments saturated with H2S). The obtained results allowed, with minimum costs, to prepare the previously developed integrated computer model (STAN 2000) for calculating the structure and mechanical properties. Calculations using the model made it possible to select such temperature-deformation regimes, which would be the minimum structural inhomogeneity over the section of the thickness of the hot-rolled strip. The results obtained: corrosion resistance repeatedly confirmed by the absence of cracks at the beginning after testing in accordance with the procedure Standard TM 0284.
Evaluation of Cu-Ni-Based Alloys for Thermoelectric Energy Conversion
Authors: Steinhoff Timon , Wolf Mario , Nürnberger Florian , Gerstein Gregory , Feldhoff Armin
Published: January 2021

The recent revitalization of Ioffe plots (entropy conductivity versus electrical conductivity) reminds us that Isotan (Cu55Ni44Mn1) is an outstanding thermoelectric material with a power factor of up to 60 W cm-1 K-2 at a specific electrical conductivity of almost 20,000 S cm-1 at elevated temperature. Even though, Isotan is widely used in thermoelements for temperature measurement, its high open-circuited thermal conductivity of approximately 70 W cm-1 K-2 [1] hindered further research as a promising thermoelectric material. Isotan was chosen as a starting composition. Influence of partial substitution of Cu and Ni with heavy elements (Sn,W) on the thermoelectric properties was studied. The alloys were fabricated by arc-melting and microstructurally characterized for grain size and elemental composition by scanning electron microscope (SEM) combined with energy-dispersive X-ray (EDXS). Lattice symmetry and parameters were estimated by X-ray diffraction (XRD). Functional properties as Seebeck coefficient, electrical conductivity and power factor were used to evaluate the thermoelectric performance.
A Novel Method for Evaluation of Chromium Evaporation from Solid Oxide Fuel Cells Interconnects: A Feasibility Study
Authors: Paravidino Daniele , Piccardo Paolo , Spotorno Roberto
Published: January 2021

The evaporation of volatile chromium species from ferritic stainless steels (FSSs) used as interconnect is well-known as degradation source for planar solid oxide fuel cell (SOFC) stacks. This work presents a feasibility study to quantify chromium evaporation from FSSs. It is based on measuring carbon dioxide produced by an intermediate reaction. Cr evaporated is collected by sodium carbonate forming sodium chromate and carbon dioxide. Measuring the resulting carbon dioxide allowed to quantify online the amount of reacted chromium with the carbonates. The post-experiment quantification of sodium chromate confirmed the applicability of the proposed method.
Microstructure Development in the Bonding Zone of Explosively Welded Ti and Cu Sheets
Authors: Paul Henryk , Bobrowski Piotr , Chulist Robert , Miszczyk Magdalena M. , Prażmowski M.
Published: January 2021

The interplay of various hardening and softening processes during explosive welding and post-processing annealing have been analysed in titanium/copper bimetallic sheets using scanning electron microscopy and microhardness measurements. Severe plastic deformation and intermetallics’ formation are typical processes leading to hardening, whereas dynamic/static recrystallization and the transformation of amorphous phases into crystalline ones lead to softening. In the as-welded state the interfacial layers of both parent sheets are severely deformed. However, they can undergo intense recrystalization in areas near large melted zones. Inside the melted zones a wide variety of chemical compositions can be detected, however, most of the phases do not appear in the Ti-Cu equilibrium phase diagram. The post-processing annealing at 973 K for 1 h leads to full recrystallization of severely deformed layers of parent sheets and transforms the non-equilibrium phases forming melted zone into the equilibrium TiCu4 and Ti3Cu4 ones via spinodal decomposition. Simultaneously, the growth of four intermetallic layers: Ti2Cu, TiCu, Ti3Cu4, TiCu4 situated along the whole interface was detected.
The Influence of the Sintering Temperature on the Properties of the 0.98Pb(Zr1-xTix)O3 - 0.02La(Fe3+0.5, Nb5+0.5)O3 Ceramic Systems
Authors: Dumitru Alina Iulia , Velciu Georgeta , Patroi Delia , Pintea Jana , Marinescu Virgil , Peter Ildiko
Published: January 2021

The ferroelectric solid solutions described by a general formula 0.98Pb(Zr1-xTix)O3 – 0.02La(Fe3+0.5, Nb5+0.5)O3 have been obtained by solid state reaction technique, where x assumes the following values: 0.42, 0.48 and 0.58. The structure of these ferroelectric compositions has been investigated in detail using X-ray diffraction analysis (XRD) and Scanning Electron Microscopy (SEM). The results obtained by XRD have evidenced that all obtained samples have a perovskite structure. The influence of the sintering temperature on the degree of incorporation of the elements in the solid solution have been studied too. The dielectric and piezoelectric constants have been determined and the influence of temperature on obtained values are presented and discussed. The performed experimental results have pointed out that the materials are characterized by a high anisotropy. Furthermore, the obtained values of the electromechanical coupling factor (kp) is situated between 0.40÷0.65 depending on the composition and the sintering temperature too.
The Influence of Process Parameters on Structure of YSZ Coating Deposited by Plasma Spraying on AISI 316L Stainless Steel Surface by APS Method and on Ti6Al4V Titanium Alloy Surface by PS-PVD Method
Authors: Pytel Maciej , Kubaszek Tadeusz , Pędrak Paweł , Góral Marek , Drajewicz Marcin
Published: January 2021

The plasma spraying is commonly used in medical application. The Atmospheric Plasma Spray (APS) method was applied for production of yttria-stabilized zirconia (YSZ) on AISI 316L stainless steel surface and also on Ti6Al4V titanium alloy surface. In present article two examples of coatings production were presented. In first experimental the YSZ was plasma sprayed (APS) on 316L stainless steel surface. The coating was deposited using A60 (Thermico) plasma torch. The initial parameters were selected and it was concluded that minimal power current was 500A. The thickness of obtained coating was in range 100-150 micrometers. The X-ray phase analysis showed the presence of tetragonal t-phase of ZrO2. The lamellar structure of coatings with large porosity was observed. In second experimental the newly developed Plasma Spray Physical Vapor Deposition method (PS-PVD) was used. The YSZ coating was deposited on titanium Grade 5 surface. The conducted research showed the formation of two types of coatings structure. When the power current was lower (2000 A) the dense lamellar-like coatings was obtained. If the power current was increased (up to 2200A) the columnar ceramic coating was observed.
Near-Threshold Fatigue Crack Growth Behavior of ECAPed Ultrafine-Grained Copper
Authors: Qu Shou Dao , You Ze Sheng
Published: January 2021

Fatigue crack growth resistance of ultrafine grained Cu processed by equal channel angular pressing (ECAP) was investigated. Particular emphasis was devoted to the effects of microstructure evolution on fatigue crack growth in the near-threshold regime. The ultrafine grained Cu exhibits a lower fatigue threshold than coarse-grained Cu at stress ratios of 0.1 and 0.7. Fatigue induced coarsening of the UFG structure near the fatigue crack and intergranular fatigue crack growth are observed.
Influence of Heat and Surface Treatments on the Fatigue Response of DMLS Manufactured AlSi10mg
Authors: Croccolo Dario , de Agostinis Massimiliano , Fini Stefano , Olmi Giorgio , Paiardini Luca , Robusto Francesco , Bonomo Antonio
Published: January 2021

The aim of this study is to analyze how the fatigue behavior of DMLS built AlSi10Mg may be affected by heat and surface treatments. A three-by-three factorial plan has been arranged for this purpose. Particularly, regarding the heat treatment, three levels were considered (as built, age hardening and stress relief), whereas, for the surface treatment, three levels were investigated (micro shot-peening, micro shot-peening plus fine blasting and DMLS production, machining and lapping). Ten specimens per type were built with vertical orientation and with a cylindrical smooth geometry. 90 samples were tested on a four-point rotating bending machine, aiming at the determination of S-N curves in the finite life domain. The experimental results were statistically processed and compared. The outcome was that heat treatment significantly affects the fatigue response and stress relief may have a detrimental impact. Fractographic studies were performed as well, to individuate the crack initiation points. Finally, density measurements were carried out to quantify the porosity level.
Standardization of Cosα Method for X-Ray Stress Measurement
Authors: Sasaki Toshihiko , Mizuno Ryoji , Takago Shigeki , Mishima Yoshihisa
Published: January 2021

Performing X-ray stress measurement by a new method called the cosα method is spreading in Japan. The cosα method is characterized in that the entire diffraction ring is used and analysed. As a result, the measurement speed is fast, and the device can be downsized. On the other hand, the conventional sin2ψ method requires precise measurement of diffracted X-rays at several X-ray incident angles, which increases the measurement time and the size of the device. In addition, since only a small part of the diffraction ring generated during the X-ray irradiation is used, some of the information on the diffraction ring cannot be used so it is a wasteful method. In 2012, cosα method equipment was released in Japan. Since then, cosα method X-ray stress measurements have been performed at more than 300 facilities. In response to this situation, the Japan Society for Nondestructive Inspection (JSNDI) together with public and private institutions established a study group on the cosα method in 2014, and examined the cosα method and its appropriate use. In this paper, we report the results of this study group.
Miniaturized Blood Sampling System with Integrated Sample Preparation
Authors: Schlegel Susanne , Krumnow Erik , Böhme Andrea , Minieri Marilena , Foitzik Andreas H.
Published: January 2021

Blood sampling as well as sample preparation are time consuming and requires a strict procedure, which is generally performed by medical trained personal. Not carrying out the procedure correctly could result in an infection of the patient or contamination of the sample itself. These limitations should be especially considered in case of pandemic outbreaks. In order to handle such a high number of patients a novel sample preparation system paired with modern blood sampling procedure is necessary. For this reason, a new device for blood sampling and preparation is designed containing an integrated microfluidic system. The fabrication is carried out by utilizing micro moulding of PDMS as well as micro milling. A first set of initial experiments as part of a first-generation study shows promising results. However, further steps of optimisation considering flow time and preparation cycle are part of a second-generation study.
High Energy Surface Implantation by Ion Nitrogen of Ultra- Fine Grained Ti-6Al-4V Alloy for Engineering Application
Authors: Semenova Irina P. , Smyslova Marina , Selivanov Konstantin , Sitdikov Vil , Valiev Roman
Published: January 2021

This paper aims to study the peculiarities of a modified layer in the surface of ultrafine-grained (UFG) Ti-6Al-4V alloy after high energy ion nitrogen implantation. The UFG structure in the alloy was produced by equal channel angular pressing. X-ray diffraction analysis and scratch-testing were applied for the investigation. The influence of low-temperature annealing (400°C during 1 hour) on the substructure parameters and phase composition of the surface layer depending on a number of cycles of ion implantation with annealing was shown in the research. The effect of the UFG structure on mechanisms and strengthening degree of the surface after ion implantation is discussed.
Spinning Formability of Al-Mg-Si Alloy
Authors: Seta Shota , Kobayashi Junya , Itoh Goroh
Published: January 2021

Spinning is a type of plastic forming in which a tool such as a roller is pressed against a rotating plate or tube to gradually deform the shape and obtain a product with the same shape as the forming die. This processing method has the advantage that it can be processed seamlessly but has the drawback of causing internal defects due to deformation. In this study, the purpose is to obtain basic knowledge about the internal defect generation mechanism in spinning, and to perform cold and hot spinning with high diameter reduction under various conditions on Al-Mg-Si alloy tube. From the experimental results, it was confirmed that the inner defects increased as the diameter reduction ratio increased. It was considered that the main cause of the occurrence of inner defects was that, at a high diameter reduction ratio, the amount of processing was large, so that the increase of material flow led to increase of wall pressure.
Effect of Interstitial Elements on the Cryogenic Mechanical Behavior of FCC High Entropy Alloys
Authors: Semenyuk Anastasia , Klimova Margarita , Zherebtsov Sergey , Stepanov Nikita
Published: January 2021

High entropy alloys (HEAs) with face-centered cubic (fcc) structure, namely equiatomic CoCrFeMnNi alloy, have attracted considerable attention because of impressive cryogenic mechanical properties – strength, ductility, and fracture toughness. Further increase of the properties can be achieved, for example, by proper alloying. A particularly attractive option is the addition of interstitial elements like carbon or nitrogen. In present work, a series of CoCrFeMnNi-based alloys with different amounts of C and N (0-2 at.%) was prepared by induction melting. The alloys doped with C had lower Cr content to increase the solubility of carbon in the fcc solid solution. It was revealed that the solid solution strengthening effect of both C and N is significantly increased when the testing temperature decreases from 293K to 77K. The effect of thermomechanical processing on the structure and mechanical properties of the alloys is analyzed.
Microstructure Refinement Effect on EUROFER 97 Steel for Nuclear Fusion Application
Authors: Stornelli Giulia , Montanari Roberto , Testani Claudio , Pilloni Luciano , Napoli Giuseppe , di Pietro Orlando , Di Schino Andrea
Published: January 2021

In Europe EUROFER 97 has been recognised as reference steel for the nuclear costructions under high radiation density for first wall of a fast breeder reactors as well as in other high stressed primary structures such as the divertors, blanklet and vessels. Following to this a EUROFER 97 detailed knowledge of the microstructure evolution after thermo-mechanical processing is required, because the material mechanical properties are interesting also for innovative solar plants, i.e. NEXTOWER project. A detailed knowledge of process optimisation is mandatory because EUROFER 97 steel mechanical properties and microstruture are heavily influenced and improved (and easily affeted) by thermomechanical treatments. In this paper the effect of thermo-mechanical parameters on the grain refinement of EUROFER 97 has been investigated by cold rolling and heat treatment on pilot scale.
Structure and Microstructure of Advanced Materials Characterized by Neutron Diffraction
Authors: Strunz Pavel , Kocich Radim , Beran Přemysl , Kunčická Lenka , Mukherji Debashis , Gilles Ralph , Hofmann Michael
Published: January 2021

Characterization of advanced materials by neutron powder diffraction provides information not accessible by other techniques. Thanks to the low absorption of neutrons, the bulk of the material and large-grain samples can be investigated, moreover in situ at elevated temperatures. The neutron diffraction use is demonstrated on two types of technologically important materials: Ti-Zr alloy and Co-Re high temperature alloy. In Ti-Zr alloy, the residual stress relief and microstrain evolution after ECAP was established. Boron influence on TaC strengthening precipitates in Co-Re high temperature alloys was shown not to be significant at the foreseen alloy operation temperatures, although boron content has a strong influence on the matrix phase.
Performance of a Matrix Type High Speed Steel after Deep Cryogenic and Low Tempering Temperature
Authors: Worasaen Kaweewat , Stark Andreas , Tuchinda Karuna , Suwanpinij Piyada
Published: January 2021

A matrix type high speed steel YXR3 designed for a combination of wear resistance and toughness is investigated for its mechanical properties after hardening by deep cryogenic treatment follow by tempering. The deep cryogenic quenching carried out at -200 °C for 36 hours and the single step tempering results in an obvious improvement in wear resistance while balancing the toughness, comparing with the conventional quenching followed by a double tempering treatment. The quantitative image analysis reveals little difference in the MC carbide size distribution between tempering at different temperatures. The synchrotron high energy XRD confirms the MC type carbide with some evolution in its orientation together with tempered martensite approaching the BCC structure at higher temperatures. In contrary to the conventional quenching and tempering, the lowest tempering temperature at 200 °C yields a moderate drop in hardness with increase in surface toughness proportionally while exhibiting exceptional wear resistance. Such thermal cycle can be recommended for the industry both for the practicality and improved tool life.
Effect of Microshot Peening on Fatigue Strength of Austenite Stainless Steel
Authors: Harada Yasunori , Takahashi Katsuhiko
Published: January 2021

The effects of the peening conditions on the surface characteristics and fatigue strength of stainless steel were investigated by microshot peening (MSP). In recent years, MSP technology has attracted attention. The use of MSP technology with minute media has become more widespread in consideration of the reduction of the notch effect in the material surface. However, the effect of MSP technology on stainless steel has not been much studied. In the present study, an air-type machine was used. The media used was high-carbon cast steel (490 HV) and Fe-Cr-B alloy (1130 HV), with an average diameter of 0.1 mm. The peening time was in the range of 0 - 100 s. Four types of stainless steels, SUS304, SUS304L, SUS316, and SUS316L, were tested. The workpieces were annealed at 1100 K for 1.2 ks in air. In the measurement of fatigue strength, the workpieces were machined in hour-glass shape. As the results, surface roughness of the workpieces treated by MSP was small. Work hardening was evident to the depth of approximately 0.2 mm from the surface. This depth was about twice the diameter of shot media. However, the effect of the peening time on the hardness distribution was not large. The compressive residual stress was added in the surface vicinity. It is assumed that the fatigue limit had increased because the work hardened layer was formed near the workpiece surface.
Deformation Property of Dense Oxide Coated Magnesium Alloy Surface
Authors: Watazu Akira , Sonoda Tsutomu
Published: January 2021

Dense oxide coated AZ 31 magnesium alloy surfaces were uniformly formed using a radio frequency magnetron sputtering method. The magnesium oxide thin film thickness was about 240 nm. XRD results of the film indicated that film of magnesium oxide single phase was deposited. The surface of the film was uniform and no crack was observed. The Vickers hardness measured by the nanoindenter was about Hv80 and Hv200 for the AZ31 substrate and the sample coated with the thin film, respectively. The dynamic hardness of the AZ31 substrate and the sample coated with the thin film were almost the same. In the curve at the time of pressurization, a step was observed in the sample coated with the thin film. On the other hand, many steps were observed in the data curve for the thin film deposited on the glass substrate.
The Influence of HPT on Microstructure and Wear Resistance of Al-7wt%Si-2wt%Fe Alloy
Authors: Wongsa-Ngam Jittraporn , Xu Jie , Phongphisutthinan Chakkrist , Langdon Terence G.
Published: January 2021

An aluminum silicon-based alloy Al-7wt%Si-2wt%Fe, was processed by severe plastic deformation technique in high-pressure torsion (HPT) at room temperature under a pressure of 6.0 GPa and rotational speed of 1.0 rpm with various numbers of turns up to five. Microstructure evolution, especially iron-containing intermetallic phases, was observed using an optical microscope and a scanning electron microscope (SEM). The microstructure results demonstrate that the large strains introduced by HPT at ambient temperature cause fragmentation of iron-intermetallic particles. The degree of fragmentation increases with increasing numbers of turns so that the intermetallic particles decreased in size with increasing imposed strain. In addition, the wear properties were evaluated using ball-on-disc dry sliding testing for both the as-cast material and the alloy processed by HPT using micro-tribometer UMT-2 (CETR Co., USA) following the ASTM G99-05 (2010) standard. The wear tests were conducted on the surface of the samples at 1.5 mm from the disc center under a normal load of 5 N with a rotational speed of 60 rpm and sliding time of 10 min. The friction coefficient and wear volume loss were examined to evaluate the effect of HPT on wear resistance. The results show that the samples processed by HPT have lower average values for the COF and wear volume loss than that of unprocessed samples.
Mechanical Behaviour of Rubber Material with Consideration to Mullins Effect
Authors: Woo Chang Su , Park Hyun Sung
Published: January 2021

A stress softening known as the Mullins effect is observed usually in rubberlike material after the first load. This paper describes an experimental test method for defining the nonlinear properties of rubber materials used for finite element analysis. Experimental observations have shown that the Mullins effect induces a permanent set and some anisotropy. To test the Mullins effect the mechanical preconditioning is suggested to stabilize the properties of rubber material. A stress-strain curve will change significantly when the rubber material is strained greater than the previous stabilized level. Therefore, material properties at maximum strain level are obtained to predict behavior of rubber products. To obtain the rubber material constants used for finite element analysis to understand the characteristics of automotive rubber parts, mechanical properties tests such as uniaxial tension, equ-biaxial tension and pure shear tests are required. When the load was repeatedly applied to the rubber specimen, the stress-strain relationship was greatest in the first and second cycles, and the larger the strain range, the more the stress was reduced. The material constants were obtained using the stress-strain data after the rubber specimen was stabilized. The value of stiffness decreased as the maximum strain range increased. The static stiffness of an automotive engine mount is calculated by nonlinear finite element analysis using the experimentally determined material constants and compared with the experimental results considering the mechanical preconditioning effect resulting in a good correlation.
Correlation of Segregation Energies of Ni and Fe with Mendeleev Number
Authors: Wunderlich Wilfried
Published: January 2021

The needs for advanced functional materials are expected to provide a boost in powder metallurgy, where impurities on powder surfaces are incorporated as grain boundary segregation. This paper has three aims. After the consistency check, we analyze whether the reported data of Ni and Fe hosts can be correlated to the Mendeleev number of chemical elements. The data of the solvents were analyzed using the software R for principal component analysis (PCA). We grouped and correlated the data to Mendeleev number. The third aim is correlation with other element data such as solubility. As a result, we found that the embrittlement depends strongly on the chemical bonding. Surprisingly, the geometry of the grain boundary type such as interlayer distances, and local atomic volumes has only a minor influence.
Operando Monitoring of Charging Processes in Battery Cathodes by Magnetometry and Positron Annihilation
Authors: Klinser Gregor , Krenn Heinz , Würschum R.
Published: January 2021

Research in the field of modern battery materials demands characterization techniques which allow an inspection of atomistic processes during battery charging and discharging. Two powerful tools for this purpose are magnetometry and positron-electron annihilation. The magnetic moment serves as highly sensitive fingerprint for the oxidation state of the transition metal ions, thus enabling to identify the electrochemical ”active” ions. The positron lifetime on the other hand, is sensitive to open volume defects of the size of a few missing atoms down to single vacancies providing an unique insight into lattice defects induced by charging and discharging. An overview will be given on operando magnetometry studies of the important class of LiNiCoMn-oxide cathode materials (so-called NMC with Ni:Co:Mn ratios of 1:1:1 and 3:1:1) as well as of sodium vanadium phosphate cathodes. First operando positron annihilation studies on a battery cathode material (NMC 1:1:1) demonstrate the capability of this technique for battery research.
The Impact of Interface Characteristics on Mechanical Performance of a Hot-Forged Cu/Ti-Coated-Diamond Composite
Authors: Lei Lei , Bolzoni Leandro , Yang Fei
Published: January 2021

The Cu/55vol.%diamond (Ti) composites were fabricated by hot forging of the cold-pressed powder preforms, consisted of elemental copper powders and Ti-coated diamond particles, at 800 °C (800C-Cu/55Dia composite) and 1050 °C (1050C-Cu55Dia composite), respectively. Well bonded interface was achieved between the diamond and the copper matrix for the 800C-Cu/55Dia composite, and the coverage of diamond by interface was about 96%, attributed to homogeneously distributed nanospherical TiC interface formed on the diamond surface. However, obvious coarse TiC particle size and spallation of the formed interface were observed in the 1050C-Cu55Dia composite, implying that the composite had a relatively low bonding strength. The formed chemical bonding, good wettability and strong mechanical interlocking between the diamond and the copper matrix enable the 800C-Cu/55Dia composite having a high tensile strength of 145 MPa and a strain at fracture of 0.35%, which are about 260% and 170% higher than those of the 1050C-Cu55Dia composite, suggesting that the 800C-Cu/55Dia composite has the potential to have a high thermal conductivity and use as high-performance heat sink materials.
Layer-Thickness Dependence of Hardness and Local Bucking Behavior in Electrodeposited Ni-Co-Cu/Cu Multilayered Films
Authors: Kaneko Yoshihisa , Kubomae Tomohiro , Kawakami Naofumi , Hagiwara Hiroyuki , Uchida Makoto
Published: January 2021

The effect of layer thickness on hardness and buckling behavior was investigated on Ni-Co-Cu/Cu multilayered films. The Ni-Co-Cu/Cu multilayered films were grown on annealed copper substrates by electrodeposition. We fabricated the multilayered films with various layer thicknesses ranging from 10 nm to 1000 nm. First, dependence of Vickers hardness on the Cu layer thickness was investigated. When the Ni-Co-Cu layer had the constant thickness of 75 nm and the Cu layer thickness was smaller than 75 nm, the hardness increased rapidly with decreasing Cu layer thickness. Subsequently, compressive tests were conducted on the multilayered films having the component layers ranging from100 nm to 1000 nm, where the hardness values did not change rapidly with layer thickness. The copper substrates coated with the multilayered films were compressed until 20% strain. From SEM surface observations after the compressive tests, formations of band-like structures having a certain thickness were recognized. Cross-sectional observation revealed that some band-like structures were formed as a result of local buckling of the multilayered film. The vertical thickness of the bank-like structures increased linearly with increasing component layer thickness.
Thermal Degradation Behavior of Hydrogen Permeability of Pd-Coated V-Alloy Membrane for Hydrogen Separation and Purification
Authors: Yukawa Hiroshi , Nambu Tomonori , Matsumoto Yoshihisa
Published: January 2021

A series of accelerated degradation experiments at high temperatures have been performed for Pd-coated V-10 mol% Fe alloy membranes in order to investigate the degradation behavior of hydrogen permeability. The degradation of the membrane becomes severer with increasing testing temperature. The temperature dependence of the 20% degradation rate almost obeys the Arrhenius relationship, suggesting that the degradation phenomenon occurs by a kind of thermal activation process. It is found that the addition of a small amount of W into Pd overlayer improves the durability of the membrane significantly.
Analysis of Different Thermal Conductivity Measurements for Al-Si Casting Alloys
Authors: Zhou Yu Li , Zhong Gu , Wang Zhan Kun , Lin Shi Peng , Zhang Jun Chao
Published: January 2021

Three types of methods, including Laser flash, Hot-Disk, and Wiedemann-Franz law, have been applied for thermal conductivity measurements of Al-Si casting alloys. The first two methods can obtain the thermal parameter directly for specific samples, while the third one calculates the target value by formula containing the electrical conductivity. Thus, the latter is widely used in the foundries because of its convenient and rapid characteristics. The purpose of this paper was to make a polite comparison among them and optimize the key constant C in the Wiedemann-Franz law to improve the calculation accuracy for Al-Si alloys. Measurements were conducted on the same set of specimens of Al-Si-xCu alloys (x ranges from 0.1 wt.% to 2.0 wt.%) at room temperature. The results showed that the measured value of Laser Flash method was well consistent with Hot Disk. While that of the Wiedemann-Franz law was different with them, the average deviation percentages were 2.17% and 2.36% when using empirical constant C (12.6 W/m·K) in the formula. Then, the constant C was modified to 8.4 W/ m·K and the average deviation percentage were decreased to 0.4% and 0.2% respectively. The reason for the differences was analyzed and a thermal conductivity evaluation model was proposed.
Hardness Development of Mechanically-Bonded Hybrid Nanostructured Alloys through High-Pressure Torsion
Authors: Kawasaki Megumi , Langdon Terence G.
Published: January 2021

Processing through the application of high-pressure torsion (HPT) provides significant grain refinement in bulk metals at room temperature. These ultrafine-grained (UFG) materials after HPT generally demonstrate exceptional mechanical properties. Recent reports demonstrated the bulk-state reactions for mechanical bonding of dissimilar lightweight metal disks to synthesize hybrid alloy systems by utilizing conventional HPT processing. Accordingly, the present report provides a comprehensive summary of the recent work on processing of several UFG hybrid alloy systems including Al-Mg and Al-Cu by HPT under 6.0 GPa at room temperature and a special emphasis was placed on understanding the evolution of hardness. This study demonstrates a significant opportunity for the application of HPT for a possible contribution to current enhancements in diffusion bonding, welding and mechanical joining technologies as well as to an introduction of hybrid engineering nanomaterials.
Evaluation of Color Tone and Exfoliation Resistance of Porcelain-Firing Ti with White Oxide Coating as an Opaque Layer
Authors: Kuratani Taro , Miura-Fujiwara Eri , Yamasaki Tohru
Published: January 2021

One of the applications of titanium in the dental field is a porcelain-fired-metal crown. It is made by firing porcelain multiple times with different composition of ceramics on a metallic abutment tooth. Regarding firing process to metallic abutment, a primer is generally required to be applied in advance of a porcelain firing and the opaque porcelain is applied to cover the metallic color of the abutment. By the way, our recent research shows that white oxide films formed on the Ti substrate have a color tone similar to opaque porcelain. Therefore, porcelain-fired-Ti samples replacing primer and opaque porcelain firing with the TiO2 oxide layer were fabricated and evaluated in this study. Color tone and peel strength were evaluated, and cross-sectional observation was observed by SEM and EPMA.
Grey-Fuzzy Logic Based Approach in Multi-Response Optimization of Semi-Solid Forging of A356 Aluminium Alloy
Authors: Ohdar Rajkumar , Singh Niranjan Kumar , Kumari Archana , Kumar Randhir
Published: January 2021

This paper presents an effective approach for the optimization of the semi-solid forging process of A356 Al-alloy based on the orthogonal array with the grey relational analysis and fuzzy logic analysis. Through the grey-fuzzy logic analysis, the optimization of complicated multiple performance characteristics can be converted into the optimization of a single grey-fuzzy reasoning grade. In this semi-solid forging process of A356 Al-alloy, the forging process parameters, namely the forging temperature, percent deformation, and die temperature are optimized with considerations of multiple performance characteristics including the tensile strength and hardness. The experimental results for the optimal setting have shown that the above performance characteristics in the semi-solid forging process of A356 Al-alloy can be improved effectively together through this approach.
Influence of Strain-Hardening and Dynamic Recovery on DDRX Steady State
Authors: Montheillet Frank , Piot David
Published: January 2021

Relationships between macroscopic and microscopic constitutive parameters associated with steady state DDRX are derived for a material in which strain-hardening and dynamic recovery are described by the Yoshie-Laasraoui-Jonas equation. First examples are given for illustration.
Effect of Particle Morphology on Thermal Properties of TiB2 Particle Dispersed Pure Aluminum Composites
Authors: Sasaki Gen
Published: January 2021

Particle size and distribution affect the thermal properties such as thermal conductivity, thermal expansion, and mechanical properties. In this study, TiB2 particles were used for the dispersant of pure aluminum composites because of high thermal conductivity and low thermal expansion of TiB2. Composites with different dispersibility and volume fraction of particles were prepared by spark plasma sintering. The effect of particle dispersibility in composites on thermal conductivity was estimated quantitatively by the simulation and experiments. As increasing dispersibility, the thermal conductivity was decreased and Vickers's hardness increased, but alternation for thermal conductivity was very small. With increasing volume fraction of particles, the effect of the particle dispersion on the change of the thermal conductivity increased. In addition, the empirical equation of the thermal conductivity considering dispersibility was estimated. The coefficient of thermal expansion decreased with increasing the particle volume fraction, and the experimental value quite accorded with a result provided by the rule of mixture.
Additive Manufacturing of Ti6Al4V with Wire Laser Metal Deposition Process
Authors: Ayed Achraf , Bras Guénolé , Bernard Henri , Michaud Pierre , Balcaen Yannick , Alexis Joel
Published: January 2021

Additive manufacturing (AM) using wire as an input material is currently in full swing, with very strong growth prospects thanks to the possibility of creating large parts, with high deposition rates, but also a low investment cost compared to the powder bed fusion machines. A versatile 3D printing device using a Direct Energy Deposition Wire-Laser (DED-W Laser) with Precitec Coaxprinter station to melt a metallic filler wire is developed to build titanium parts by optimizing the process parameters. The geometrical and metallurgical of produced parts are analyzed. In the literature, several authors agree to define wire feed speed, travel speed, and laser beam power as first-order process parameters governing laser-wire deposition. This study shows the relative importance of these parameters taking separately as well as the importance of their sequencing at the start of the process. Titanium deposit are obtained with powers never explored in bibliography (up to 5 kW), and wire feed speed up to 5 m.min-1 with a complete process repeatability.
Influence of Elastic Modulus of Matrix on Conductivity of VGCF Dispersed in Plastic Matrix
Authors: Aoki Toi , Nakayama Noboru , Horita Masaomi , Fukui Hiroaki
Published: January 2021

Pressure-sensitive conductive material is used for various pressure sensors consists of a polymer nanocomposite with carbon nanotubes (VGCF). And the resistance in it were changed by adding applied load. Recently, carbon nanotubes (VGCF) has drawn attention as a function filler that imparts various functions to a resin, including electrical properties. In polycarbonate (PC) composite with VGCF, the resistance decreases with increase in applied load. And increase of the addition amount of VGCF was enhanced the mechanical properties and electronic properties. In addition, this conclusion suggested that strain of PC/VGCF caused reducing the resistance. Therefore, changing matrix is predictably effective on electrical properties in pressure-conductive materials. In the present study, we used various matrix had different elastic modulus. The addition amount of VGCF was 12.5% volume rate. We made silicone/VGCF and polyethylene (PE)/VGCF and polycarbonate (PC)/VGCF by twin screw extruder and injection moldings. To clarify the influence of elastic modulus of matrix on conductivity of VGCF dispersed plastic matrix composites. The experimental results showed that conductive property of pressure-sensitive conductive materials is related to elastic modulus of them.
Thermomechanical Processing without Accelerated Cooling to Achieve an As-Rolled Yield Strength of 400MPa in C-Mn Steel Plate
Authors: Banks Kevin Mark , Maubane Dannis Rorisang Nkarapa , Coleman Michelle
Published: January 2021

Thermomechanical (TM) rolling schedules have been developed using mathematical modelling, physical simulation and industrial trials to produce C-Mn steel plate with yield strengths of 400MPa and good impact toughness without the need of expensive micro-alloying additions or accelerated cooling. The process relies on careful selection of delay times to accumulate sufficient retained strain during austenite conditioning for enhanced nucleation of ferrite. An integrated heat transfer-austenite processing model was used to predict the final microstructure and mechanical properties. The extent of strain accumulation and progress of recrystallisation during rolling were confirmed by laboratory simulation. Based on these results, carefully controlled industrial TM rolling trials were performed on C-Mn steels. Adequate grain refinement and properties are achieved through suppression of recrystallisation and strain accumulation in the low austenite temperature region after a sufficient delay period prior to finishing.
Extended Model for Prediction of Transition from Internal to External Oxidation in Steels: Comparison between Analytical/Semi-Analytical and Numerical Approaches
Authors: Darghoum Ikram , Leblond Jean-Baptiste , Huin Didier , Bergheau Jean-Michel , Bertrand Florence
Published: January 2021

The aim of this paper is to present a model that predicts the transition from internal to external oxidation. This variant is based on the simultaneous resolution of the diffusion equations and the equilibrium equation that stems from the assumption of the local instantaneous thermodynamic equilibrium. It accounts for the possible formation of large precipitates fractions that may act as diffusion barriers. This effect is modeled by introducing a dependence of the diffusion coefficients upon the mass fraction of precipitates. As a counterpart, it is generally impossible to solve the non-linear equations of the model analytically. Thus, a semi-analytical and a finite elements models are presented.
The Isothermal Oxidation of MCrAlY Protective Coatings
Authors: Drajewicz Marcin , Kubaszek Tadeusz , Kościelniak Barbara , Góral Marek , Dziadosz Dawid
Published: January 2021

The thermal barrier coatings (TBC) are commonly used for protection of jet engine parts. In presented article the influence of chemical composition of TBCs bond coats on isothermal oxidation resistance was analysed. The bond coat was plasma sprayed (APS) using different MCrAlY alloys produced by Oerlikon-Metco: Metco 4451, AMDRY 997, AMDRY 962, AMDRY 365-1, AMDRY 995C. The conducted research showed big difference in coating thickness despite the same spraying parameters. The difference in porosity was not observed. The isothermal oxidation test was conducted during 500h at 1100°C in static laboratory air. The obtained results showed, that degradation mechanism of MCrAlY bond coats regardless of chemical composition is similar. The formation of scale contained aluminium and chromium oxides was observed. The internal oxidation effect was also observed in produced coatings.
Evolution of the Microstructure and Mechanical Properties of the Ultrafine-Grained VT8M-1 during Isothermal Die Forging and Thermal Treatment
Authors: Dyakonov Grigory , Yakovleva Tatyana Vitalyevna , Stotskiy Andrey , Ibatullin Askar , Semenova Irina P.
Published: January 2021

The work addresses the microstructural evolution and mechanical properties of the ultrafine-grained (UFG) VT8M-1 subjected to isothermal die forging (IDF) and subsequent thermal treatment. An UFG microstructure with a mean size of secondary grains of about 0.3 μm was processed by a rotary swaging (RS) at Т=780°С. The ultimate tensile strength (UTS) of the alloy increased by 23% as compared to an initial state due to the formation of an UFG microstructure. It has been shown that isothermal die forging of the UFG alloy at Т=780°С leads to the growth of secondary phase grains by 0.7 μm. Subsequent heat treatment of the forged billets leads to hardening of 11%, which can be attributed both to the formation of additional interphase α/β boundaries at the precipitation of a tertiary α-phase and silicide dispersion.
Tensile Deformation Behavior of Magnesium Single Crystals with Different Yttrium Concentrations
Authors: Hanada Tomohiro , Tsushida Masayuki , Kitahara Hiromoto , Ando Shinji
Published: January 2021

Tensile tests of Mg-Y single crystals with different yttrium concentrations: 0.07 and 0.3 at.% were carried out to investigate effects of yttrium on pyramidal  slip system. In Mg-0.07at%Y alloy single crystals, {11 2}< 23> second order pyramidal  slip was activated and yield stress increased, compared to pure Mg single crystals. On other hand, in Mg-0.3at%Y alloy single crystals, {10 1}< 23> first order pyramidal  slip was activated and yield stress increased, compared to Mg-0.07at%Y alloy single crystals. The change in slip system by yttrium addition would be caused by increasing critical resolved shear stress (CRSS) for second order pyramidal slip.
Quantitative Detection of Hydrogen Gas Release during Slow Strain Rate Testing in Aluminum Alloys
Authors: Horikawa Keitaro , Arayama Michiko , Kobayashi Hidetoshi
Published: January 2021

We have developed a new testing device which is capable of detecting hydrogen gas release during slow strain rate tensile testing (SSRT) under ordinary pressure. The device is composed of an SSRT machine equipped with a closed chamber with an inspection window that is connected to gas chromatography with a semiconductor hydrogen sensor. Local strain distribution in the specimen during the SSRT is monitored dynamically with a digital image correlation (DIC) method. Hydrogen was pre-charged to aluminum alloys by means of friction in water process. Using the device, it was shown that hydrogen was released particularly in the stage of plastic deformation and fracture. In addition, the hydrogen gas release at the moment of fracture was clearly increased when the alloys were hydrogen-charged and tested at a slow strain rate. When we calculated hydrogen gas release from the fracture surface in Al-Zn-Mg base alloys tested at 3.3×10-6 s-1, the hydrogen amount was estimated to be 6.24×10-10 mol /mm2 in a hydrogen-uncharged alloy, and 1.30×10-9 mol / mm2 in a hydrogen-charged alloy.
Optimization of Slab Edge in Roughing of Stainless Steel
Authors: Ilmola Joonas , Seppälä Oskari , Haapala Olli , Puukko Esa , Larkiola Jari
Published: January 2021

To reach high demands of a stainless steel surface quality the location of a slab edge is optimized utilizing multiphysical finite element (FE) analysis. The slab edge forms in roughing process when the longitudinal edge of the stainless steel slab moves parallelly towards the center of a transfer strip surface due to several rough and edge rolling passes. Strip spreading and location of the slab edge are managed by edge rolling process which is accomplished concurrently with roughing. Deformation resistance has a significant role characterizing the strip spreading and material flow in the roll bite, thus experimental material compression testing was carried out and the results fitted to the Hensel-Spittel equation. Multiple edger roll profiles were designed, and the most feasible details of the roll profile were iteratively utilized for the new profiles. In this way the location of the slab edge was optimized closer to the edge of the transfer strip by developing a new edger roll profile and resetting edge rolling passes according to results of FE-simulations. To mimic an industrial-scale roughing process an automated pass schedule control was developed in the FE-model. Therefore, multipass simulations require only a pass schedule data to run simulation.