bluuebunny/crossref_metadata_2025 huggingface dataset:
Processing Strategies for Hot-Rolled Medium-Mn Steels
Authors: Grajcar Adam , Adam Skowronek , Morawiec Mateusz
Published: January 2021

The study aims at reviewing manufacturing schedules for hot-rolled and intercritically-annealed and thermomechanically processed medium-Mn sheet steels. Major differences between these two types of processing are indicated. They include initial microstructure (low-C martensite for hot-rolled products and deformed austenite for thermomechanically processed products), partitioning of alloying elements (depending on intercritical annealing or batch annealing conditions) and microstructure prior to cooling (ultrafine-grained lath mixture of ferrite and austenite for hot-rolled, intercritically annealed products and deformed austenite for directly cooled products). The comparison of typical microstructures (LM, SEM) and phase transformation behavior are presented. A role of Mn as an austenite stabilizer in a range used for medium-Mn steels is explained. Some results are provided for economic steels containing 3% and 5% Mn.
Optimization of Preform for Stub Axle Forging Using Simulation Software
Authors: Dora T. Lachana , Singh Niranjan Kumar , Ohdar Rajkumar
Published: January 2021

There is a growing demand for more efficient and economic manufacturing process to improve product quality, reduce production cost, reduce lead time and increase productivity. The application of computer aided design and manufacturing (CAD/CAM) techniques to forging is becoming increasingly popular as the resulting improvements in yield and productivity. Modeling and simulation have become a major concern in recent and advanced research. In this paper die design for forging of an automobile component “Stub Axle” is presented. In die forging process, complex shape component cannot be made in one stage and therefore, the use of preform die becomes essential. The initial preform design was carried out by conventional method. The simulation has been carried out using software DEFORM-3D. The main goal of this study is to design an optimal preform shape resulting an optimal initial billet selection. Keywords:CAD/CAM, Preform, DEFORM-3D, Simulation, Forging
Microstructure and Shape Memory Behavior of Ti-18Nb-6Zr (at.%) Alloy
Authors: Song Xiao Yun , Ye Wen Jun , Hui Song Xiao
Published: January 2021

The microstructures and shape memory behaviors of Ti-18Nb-6Zr (at.%) alloy subjected to different heat treatments were investigated through optical microscopy (OM), X-ray diffraction (XRD), Transmission electron microscopy (TEM) and tensile tests. Recrystallization occurs in cold-rolled Ti-18Nb-6Zr alloy after solution treatment at 600~800 °C. The cooling rate after solution treatment at 800°C shows a dramatic effect on the microstructure of the alloy. The microstructures for the water quenching (WQ) and oil quenching (OQ) specimens are composed of single α'' martensite phase, while for the air cooling (AC) specimen, the microstructure consists of predominant β phase and a small amount of fine athermal ω phase. During tensile deformation, two-stage yielding is observed in the alloy subjected to 800°C/0.5h/WQ heat treatment. The stress for martensite variants reorientation and the yield stress for plastic deformation are 310MPa and 455MPa, respectievely, and the maximum shape memory strain of 3.1% is obtained with pre-strain of 6%.
Effect of Temperature and Humidity on Degradation Behavior of Cu/Epoxy Interface under High Temperature and High Humidity Aging
Authors: Suzuki Riku , Shohji Ikuo , Kobayashi Tatsuya , Tonozuka Yu
Published: January 2021

This article reports on the degradation behavior of adhesion strength of the resin/copper interface under aging in high temperature and high humidity environment. The adhesion strength of a Cu joint with resin was investigated by a tensile test. The fracture surface was analyzed by Fourier transform infrared spectroscopy to investigate the degradation mechanism. As a result, it was found that the degradation of the adhesion strength is mainly caused by water absorption and subsequent volume expansion of the resin, and embrittlement of hydrogen bonding in the joint interface. Evaluation of deterioration life of the joint revealed that the relationships between the deterioration life and the temperature and humidity are confirmed above the glass transition temperature.
Optimization of Molecular Characteristics via Machine Learning Based on Continuous Representation of Molecules
Authors: Sato Kyosuke , Tsuruta Kenji
Published: January 2021

We demonstrate an automatic materials design method using continuous representation of molecule and its atomic arrangement via a neural network algorithm. This method is applied to optimizing and predicting the HOMO-LUMO gap within the molecules composed of carbon, oxygen, nitrogen, fluorine, and hydrogen. Adopting the Quantum Machine 9 (QM9) dataset as a training dataset for the molecules, we first established a continuous representation of molecules in a latent space, then predicted molecules that have target values of the HOMO-LUMO gap. In the gap maximization calculation, the CF4 with the largest gap value in the QM9 dataset was automatically found despite there is no a priori data for the gap. In the case of a target gap value of 0.10 hartree, we found a new molecule whose gap value is closer to 0.10 hartree than any other molecules in the QM9 dataset.
Mechanical Properties of Interface Layers in SiC/TiAl Composite
Authors: Hashimoto Keizo , Jin Jiang
Published: January 2021

Although metal matrix composites (MMC) for the high temperature structural material have been investigated extensively for many years, applications of MMC have been still limited. Among many combinations between the ceramic fibers and the matrix materials, combination of SiC fiber and TiAl based intermetallic compounds has been expected to be one of the best combination, since both SiC fiber and TiAl have demonstrated the capabilities of the low density heat resistant materials. SiC fiber reinforced TiAl composites have been successfully fabricated using hot press method. Optimum temperature and pressure have been determined. SiC/TiAl composite having relatively low fiber volume fraction shows nearly an ideal elastic property applying the law of mixture. Effects of interface layers on the mechanical properties of composites have been studied in detail. Micro-indentation on a single fiber was carried out to examine the pull out strength of SiC fiber quantitatively. Estimated shear stress on the interface was 145-195MPa, those values are quite reasonable since the tensile strength of TiAl matrix was 420MPa and the maximum shear stress would be the half of tensile strength according to Schmid law. Three-point bending tests have been carried out to evaluate the mechanical properties of composites. Fiber volume fraction 8.9% specimen shows ideal bending stiffness compare with the calculated values based on the low of mixture. Reaction layers and the interface between SiC fiber and TiAl have been analyzed by SEM-EDS and XRD. At least two or more reaction layers have been identified. These reaction layers can be explained based on the Si-Ti-C ternary equilibrium phase diagram at 1373K. Optimum conditions of interface structure will be discussed
Bending and Welding of New High Oxidation Material - Thor™ 115
Authors: Urzynicok Miachal , Kwiecinski Krzysztof
Published: January 2021

Development of materials used in the power industry for the production of USC boilers poses new challenges. The introduction of new alloying agents intended at obtaining the best possible mechanical properties, including creep resistance, affects the fabricability of new steel grades. All new materials have to undergo a lot of tests, particularly as regards bending and welding processes, with the aim of enabling the development of technologies ensuring failure-free production and assembly of boiler components. Martensitic steels containing 9% Cr, used in the production of steam superheaters shall have good creep resistance and, at the same time, low oxidation resistance at a temperature above 600°C. In turn, steels with a 12% Cr content, for example, VM12-SHC or X20CrMoV12-1 are characterized by significantly higher oxidation resistance but have lower strength at higher temperatures, which translates to their limited application in the production of modern USC and A-USC boilers.X20CrMoV12-1 was withdrawn from most of the power plants across Europe and VM12-SHC was supposed to replace it, but unfortunately, it failed in regards of creep properties. To fulfill the gap a new creep strength-enhanced ferritic steel for service in supercritical and ultra-supercritical boiler applications was developed by Tenaris and named Thor™115 (Tenaris High Oxidation Resistance). This publication covers the experience obtained during first steps of fabrication which includes cold bending and TIG welding of homogenous joints.
Studies on Thermomechanical Cycling Characteristics of an Ni-Ti-Cu Shape Memory Alloy
Authors: Swaminathan Ganesan , Sampath Vedamanickam
Published: January 2021

Shape memory alloys (SMAs) find use in myriad medical and engineering applications. In these applications, the functional characteristics of the materials are capitalized on. SMAs are used repeatedly over a long period of time in service. With continued usage degradation occurs in their functional properties, leading to a change in recovery strain, recovery stress, phase transformation temperatures and hysteresis. The change in the functional characteristics of the alloys is known as functional fatigue. Functional fatigue affects the performance of the alloys with the alloys losing their intended functionality. This problem is to be addressed if the alloys are to be used effectively and efficiently throughout their lifespan. It is especially important when using the alloys within the human body, where such degradation can affect the performance of the biomedical devices and, in turn, human health and life. Till date not too many researchers have explored this area in greater detail. In order thereforeto better understand this behavior, in the present study, an Ni50Ti44.7Cu5.3 alloy wire with a d=1.43 mm and a l=100 mm was cycled (10,000) under constant stress (55 MPa) between its transformation temperatures, which were determined by DSC (without load). The effect of cycling on the shape memory properties (strain recovery, hysteresis, and transformation temperatures) after a specified number of cycles at regular intervals are considered. The results show that there is considerable difference in the properties obtained and are interpreted and discussed in detail in the paper.
Inferences of Baking Time on Hydrogen Embrittlement for High Strength Steel Treated with Various Zinc Based Electroplating
Authors: Hino Makoto , Mukai Shunsuke , Shimada Takehiro , Okada Koki , Horikawa Keitaro
Published: January 2021

The hydrogen embrittlement of SK85 high-strength steel sheets was evaluated using a three-point bending test. The effect of electroplating the metal with zinc-based coatings on hydrogen embrittlement was examined by baking treatment of differently electroplated steel specimens. After electroplating, all the specimens underwent hydrogen embrittlement, promoted by hydrogen incorporation into the metal frame, owing to the reduction of hydrogen ions during electroplating. The hydrogen embrittlement of both zinc-and zinc-SiO2-electroplated SK85 steel continued after baking for 24 hours at 473 K, but that of zinc-nickel-and zinc-nickel-SiO2-electroplated SK85 steel ceased. Furthermore, TDA revealed that the trapped hydrogen could be released from steel at approximately 473 K. However, after baking, hydrogen embrittlement did not completely disappear, and we suggest that the formation of hydrogen vacancy clusters also accounts for this fracture phenomenon. The hydrogen incorporated into steel during electroplating led to the formation of hydrogen vacancy clusters, which allowed the formation of embrittlement. However, zinc and zinc-SiO2 films were not permeable enough to release these voids; while the peculiar zinc–nickel and zinc-nickel-SiO2 film structure enabled the hydrogen vacancy clusters to diffuse from the substrate.
Effect of Cellular Dislocation Structure on the Strength of Additively Manufactured 316L Stainless Steel
Authors: Wang Min Shi , Fan Miles , Cruchley Sam , Chiu Yu Lung
Published: January 2021

Additively manufactured (AM) 316L stainless steel (SS) often contains cellular dislocation structure which is a distinct microstructural feature compared with those fabricated traditionally, like casting and forging. The role of this unique cellular dislocation structure on the mechanical properties of the AM 316L SS needs to be determined to guide its further performance improvement. In this study, the effect of cellular dislocation structure on the strength of AM 316L SS was investigated via micro-mechanical compression test. Single crystalline micro-pillars were firstly prepared from both the as-built and annealed AM 316L SS bulk specimens, with and without cellular dislocation structure relatively. The results show a significant increase of the yield strength of the micro-pillars with the cellular dislocation structure. The micro-pillars containing cellular dislocation structure with different sizes and morphologies have been studied to evaluate the effect of cellular dislocation structure on the strength of AM 316L SS.
First-Principles Study of Epoxy Resin Adhesion to Tin Oxide Surface
Authors: Yamashita Jun , Nunomura Norio
Published: January 2021

A density functional theory (DFT) is used to investigate the energetics of an epoxy resin adhere on a tin oxide and a hydroxylated-alumina surface within a supercell approach. Self—consistent geometry optimization is performed for models of adhesion interface, which is comprised of a fragment of epoxy resin and hydroxylated-Al2O3 (001), and SnO2(001) and (110) surface. The epoxy resin studied was simplified fragment based on diglycidyl ether of bisphenol A (DGEBA). It is found that the distance between the resin and the surface where the adhesion force is maximized is substantially the same for all models. Analysis of the energy-distance plot reveals that the fragment of DGEBA molecule adhere most strongly to the SnO2(001) surface, suggesting that the adhesion force is induced by van der Waals (vdW) interaction.
Efficiency of Microstructure Refinement in Ti-Based Alloys
Authors: Zherebtsov Sergey , Stepanov Nikita , Salishchev Gennady
Published: January 2021

The influence of various factors on the efficiency of microstructure refinement in two-phase titanium alloys with respect to a well-known Ti-6Al-4V alloy was discussed. The kinetics of microstructure evolution in titanium alloys with a lamellar type α/β microstructure during large plastic deformation depends mainly on temperature and strain rate, type of the initial microstructure, thickness of the α lamellae, path of deformation and chemical composition. Each parameter should be controlled to provide the most efficient microstructure refinement during conventional metalforming methods.
Fabrication of Be-Ta Ti Alloys without Pre-Alloyed Powders via SLM
Authors: Todai Mitsuharu , Nagase Takeshi , Nakano Takayoshi
Published: January 2021

In this study, we sucsess the fabrication of dense compornent of Ti-20at.%X (X = Cr and Nb) alloys by Selected laser melting (SLM) pwocess, from a mixture of poweder element powders. The volume rasio of pore and non-molten particles is dependent of the enegy density. The difficulty of fabrication of Ti-X alloy comporment is dependent of melting temperature of X element. Thus, Ti-20at.%Cr alloys, which has the lowest melting temperature of X is easier to monufacture of dense comporment. The Ti-20at.%Cr alloys and Ti-20at.%Nb comprise β-Ti single-phase components without any non-molten particles and macroscopic defects. In addtion, the {001}〈100〉 crystallographic texture of these Ti-Cr and Ti-Nb alloys can be controlled effectively by optimizing the SLM parameters. This means that the SLM is key techmelogy of controlling of Young’s modulus and shape at the same time because Young's modulus of be-ta phase in Ti alloys is strongly related to the crystal orientation.
Improvement in Mechanical Performance of Biomaterial Ti Alloy by Controlling Volume Fraction of Martensite Phase
Authors: Akahori Toshikazu , Ino Shota , Hattori Tomokazu
Published: January 2021

Recently, biomaterial α + β type Ti alloys with relatively low Young’s modulus and high specific strength have been widely used all over the world. Martensite (M) phase in α + β type Ti alloy has been reported to improve the toughness and ductility, therefore, there is high possibility of improvement in the mechanical properties easily by controlling the volume fraction of M phase. In this study, the change in mechanical properties of α + β type Ti-6Al-7Nb (Ti67) with various volume fractions of M phase were systematically investigated through the various heat treatments and thermo-mechanical treatments. Microstructures of Ti67 subjected to ST at 1173 K to 1273 K below the temperature of β transus were composed of martensite and primary α phases. The volume fraction of M phase increased with an increase in ST temperature. Tensile strength increased simply with an increase in the volume fraction of M phase, while the elongation, reduction of area and Young’s modulus showed a reverse trend. Fatigue limit of Ti67 subjected to ST at 1243K showed the highest value of 880 MPa.
Effects of Tensile Testing Temperature on Mechanical Properties and Deformation Behavior in Medium Mn Steels
Authors: Kawasaki Yoshiyasu , Toji Yuki , Takeshi Yokota , Funakawa Yoshimasa
Published: January 2021

In single-phase austenitic steels, the optimum deformation temperature in the tensile test to obtain high tensile strength-elongation balance (TS×El) and work hardening rate (dσ/dε) depends on control of the stability of austenite. In order to clarify the effects of the deformation temperature in complex phase steels containing austenite, in this study, the effects of the tensile testing temperature on mechanical properties and deformation behavior were investigated in detail using steel A and steel B with a chemical composition of 0.15C-0.5Si-5.0Mn (wt%). Steels A and B consisted of ferrite and retained austenite, but contained different volume fractions of retained austenite, namely, 29 % and 17 % as a result of annealing at 660 °C and 620 °C for 2 h, respectively. The stability of the retained austenite of steel B was higher than that of steel A. In steel A, TS×El and dσ/dε achieved their maximum values at 20 °C, decreased from 20 to 100 °C, and then remained almost unchanged at more than 150 °C. On the other hand, in steel B, TS×El and dσ/dε achieved their maximum values at -40 °C, decreased from -40 to 50 °C and remained almost unchanged at more than 100 °C. These results can be explained by the stability of retained austenite and the transformation rate from retained austenite to martensite. It should be noted that control of the stability of retained austenite and the transformation rate from retained austenite to martensite led to an adjustment of the optimum deformation temperature to achieve the high TS×El and dσ/dε in medium Mn steels, in the same manner as in single-phase austenitic steels.
Energy Absorption of Additively Manufactured Porous Metals with Disordered Cells
Authors: Kitazono Koichi , Guo Shiyue , Zhu Ke , Hamaguchi Takuya , Fujimori Yuta
Published: January 2021

Lightweight porous metals are focused on as energy absorbing materials for automobiles. Open-cell porous metals were manufactured through additive manufacturing process. Their cell structures were designed based on Voronoi diagrams using a commercial 3D-CAD software. Both ordered and disordered cell structures with the same porosities were successfully designed in this study. Compression tests and explicit finite element analysis revealed heterogeneous deformation behaviors in ordered porous metals. On the other hand, the porous metals with disordered cell structure showed relatively isotropic and uniform deformation, which is suitable as energy absorbing materials. Controlling the disordered cell structure designed by 3D-Voronoi diagram enables to develop the advanced porous metals having various mechanical properties.
Microstructure Factor of Creep Behavior in Near-α Ti Alloy
Authors: Masuyama Haruki , Matsunaga Tetsuya , Toda Yoshiaki , Ito Tsutomu , Shimojo Masayuki , Yamabe-Mitarai Yoko
Published: January 2021

Heat-resistant Ti-Al-Nb-Zr alloys, which don’t contain Sn, have been designed to obtain good oxidation resistance above 600 °C. In addition, to design Ti alloys with best balance of creep and fatigue properties, prior β grain size which affects fatigue properties and lamellar microstructure which affects creep properties were controlled by heat treatment. In the present study, the effect of microstructure on creep properties of one of the alloys, i.e., Ti-7.5Al-4Nb-4Zr alloy, with the bimodal (B), the lamellar structures in small prior β grains (LS), and the lamellar in large prior β grains (LL) were investigated at 600 °C. The creep deformation mechanism for each microstructure was a power-law creep. However, the creep life varied depending on the microstructures. The longest creep life was obtained in LS with prior β grain size of 90 μm and interlamellar spacing of approximately 10 μm, while the shortest creep life was obtained in LL with prior β grain size of 550 μm and fine interlamellar spacing of less than 2~3 μm. This suggests that creep life is more affected by interlamellar spacing than by prior β grain size.
High Cycle Fatigue Behaviour of Cu/Sn Intermetallic Compounds Prepared by Transient Liquid Phase Bonding Process
Authors: Kotas Agnieszka Betzwar , Khatibi Golta , Khodabakhshi Farzad , Steiger-Thrisfeld Andreas
Published: January 2021

Transient liquid phase (TLP) bonds using Cu-Sn system have been suggested as high strength and temperature resistant joints for power electronics applications. While the physical and mechanical properties of these joints has been investigated to some extent, studies on fatigue properties and long term reliability of TLP joints are scarce. In this work TLP bonding was performed to produce thin Cu-Sn intermetallic joints by using Cu and 97Sn3Cu solder alloy as interlayer. Different processing conditions resulted in three types of thin joints consisting of three phases (Cu3Sn/Cu6Sn5/solder remnants), two phases (Cu3Sn/Cu6Sn5) and a single phase (Cu3Sn) with an overall thickness of ≤ 20 μm. The shear strength of the TLP joint containing one or two high melting point IMC layers showed a significant temperature resistance up to 200°C. Fatigue studies of TLP joints were conducted by using a 3-point-cyclic bending test system operating at 20 kHz. The highest fatigue resistance was obtained for the single-phase Cu3Sn joints with superior shear and flexural resistance. The two phase joints (Cu3Sn/Cu6Sn5) showed a slightly lower lifetime than the three phase system containing IMCs and residual solder. Fracture surfaces analysis in correlation with static and cyclic mechanical properties, provided insight into the failure mechanism of the Cu-Sn TLP joints.
Model Description of the Unusual Temperature Dependence of the Viscosity of Metallic Glass-Forming Liquids
Authors: Aniya Masaru , Ikeda Masahiro
Published: January 2021

The temperature dependence of the viscosity of some metallic glass forming liquids (MGFLs) exhibits an unusual behavior. At high temperature, the temperature dependence is quite weak, whereas at low temperature, the viscosity varies exponentially. Recently, this type of behavior are attracting much attention, because it can be considered as a manifestation of the fragile-to-strong transition. Well known classic viscosity models do not describe such kind of behavior over a wide temperature range. In the present report, it is shown that a modified version of the Bond Strength-Coordination Number Fluctuation (BSCNF) model describes the behavior observed in MGFLs. For the convenience of the readers, a brief review of the BSCNF model is also given.
Martensitic Transformation and Damping Behavior of Fe-Mn-Nb Damping Alloys
Authors: Chen Feng , Liang Fu Kuan , Ye Wei Lin , Tong Yun Xiang , Li Li
Published: January 2021

In the present study, the microstructure, martensitic transformation and damping characteristics of Fe-17Mn-xNb (x = 0, 0.5, 1, 2, 4 wt. %) alloys were investigated. Nb addition leads to the variation in both the volume fraction and the size of ε martensite, in addition, the formation of Fe2(Nb, Mn) precipitates. The martensitic transformation exhibits a tiny dependence on the content of Nb. The addition of Nb helps to enhance the damping capacity of Fe-17Mn. The maximum value of tan δ = 0.054 is achieved in Fe-17Mn-1Nb alloy, which is increased by 42% over Fe-17Mn. The damping mechanism caused by adding Nb is discussed in terms of the volume fraction and the size of ε martensite. Besides, the role of Fe2(Nb, Mn) is also taken into account.
Mechanical Stress Issues of La0.6Sr0.4Co0.2Fe0.8O3-δ
Authors: Araki Wakako , Arai Yoshio
Published: January 2021

Ionic devices consisted of ion-conductive ceramics such as solid oxide fuel cells (SOFC) and oxygen separation membranes have been developed in the last decades. La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF), which is a mixed ionic-electronic conductive ceramics, is especially expected to play an important role in those ionic devices and so its electrochemical properties have been intensively studied.
Changes in Mechanical and Microstructural Properties of Magnesium Alloys Resulting from Superimposed High Current Density Pulses
Authors: Demler Eugen , Diedrich Alexander , Dalinger Andrej , Gerstein Gregory , Herbst Sebastian , Zaefferer Stefan , Maier Hans Jürgen
Published: January 2021

Magnesium alloys are important engineering materials due to their good combination of strength and very low densities. However, the low ductility imposed by the hcp-lattice has thus far limited the application of magnesium alloys as sheet material. The use of the electroplastic effect offers a route to increase formability of magnesium alloys while being more energy efficient than conventional hot forming. The underlying mechanism (s) of this effect have not yet been fully understood. This study investigates the impact of high current density electrical pulses on magnesium alloys. Special consideration was given to the effect of the orientation of the applied electric current relative to the mechanical loading of the specimens. The results show that the mechanical properties of coarse-grained materials are more strongly affected by the current pulses than finer grained material. Applying the current parallel to the compressive load shows a more pronounced softening of the material than pulses applied perpendicular to the mechanical stress. Microstructure investigations revealed the formation of twinning solely in the interior of grains even at stresses below the yield point for both configurations.
Mechanical Properties of Selective Laser-Melted Components of Alsi10mg for Prototype Vehicles
Authors: Egger Christoph , Grünbart Florian , Silvayeh Zahra , Šulcová Olga , Seper Christoph , Pfeifer Tanja , Sommitsch Christof , Domitner Josef
Published: January 2021

Fabrication of aluminum alloy components by traditional high-pressure die casting (HPDC) requires cost- and time-consuming tooling of steel dies, which makes HPDC uneconomic for producing low-volume components or prototypes. In comparison, powder bed-based additive manufacturing, e.g. selective laser melting (SLM), enables rapid prototyping and production of even complex-shaped components directly from computer-aided design models without needing expensive tools. However, SLM prototype components must have almost identical mechanical properties to HPDC serial components in order to emulate their functionality under different load conditions. In this work uniaxial tensile properties of cast alloy AlSi10MnMg (EN AC-43500) in condition T7, i.e. with 120-170 MPa yield stress, 200-240 MPa tensile strength and 9-12 % strain at fracture, shall be attained using selective laser melting of powder alloy AlSi10Mg (EN AC-43000). These properties were achieved by tailored heat treatment. Furthermore, the effect of hot isostatic pressing (HIP) was investigated. The results of the tensile tests confirmed the basic feasibility of substituting HPDC components with SLM components for prototyping. In particular, similar tensile strength and uniform strain were achieved for SLM samples in condition O, i.e. for SLM samples which were only annealed.
Effects of Al, Si and N Content on the Formation of M-A Constituent and HAZ Toughness of Ti-Containing Low-Carbon Steel
Authors: Bang Kook Soo , Cha Joo Hyeon , Han Kyu Tae , Jeong Hong Chul
Published: January 2021

The present work investigated the effects of Al, Si, and N content on the impact toughness of the coarse-grained heat-affected zone (CGHAZ) of Ti-containing low-carbon steel. Simulated CGHAZ of differing Al, Si, and N contents were prepared, and Charpy impact toughness was determined. The results were interpreted in terms of microstructure, especially martensite-austenite (M-A) constituent. All elements accelerated ferrite transformation in CGHAZ but at the same time increased the amount of M-A constituent, thereby deteriorating CGHAZ toughness. It is believed that Al, Si, and free N that is uncombined with Ti retard the decomposition of austenite into pearlite and increase the carbon content in the last transforming austenite, thus increasing the amount of M-A constituent. Regardless of the amount of ferrite in CGHAZ, its toughness decreased linearly with an increase of M-A constituent in this experiment, indicating that HAZ toughness is predominantly affected by the presence of M-A constituent. When a comparison of the effectiveness is made between Al and Si, it showed that a decrease in Si content is more effective in reducing M-A constituents.
Aging Response in Selective Laser Melted AlSi10Mg Alloy as Function of Distance from the Substrate Plate
Authors: Ghio Emanuele , Cerri Emanuela
Published: January 2021

Selective Laser Melting (SLM) builds a metallic part in a layer-by-layer mode with growth occurring along the vertical axis. Metallic powder layers are melted by a laser beam by programmed scan sequences inducing specific mechanical properties in the as-built samples according to process parameters. Post heat treatments are usually performed to optimise the mechanical behaviour. In this work, the effects induced by heat treatments at 175°, 200° and 225°C on SLMed bars of Al10SiMg were investigated as function of distance from the substrate plate. The bars were 300 mm height and in the as-built condition, Vickers microhardness and tensile strength decreased along the built direction, while the elongation increased from the bottom to the top of the billet. After heat treatments, Vickers microhardness resulted lower of 10HV at the top of the bar compared to its bottom in contact with the hot substrate; microhardness decreased with time at constant temperature compared to the as-built. Tensile properties showed variations of 50 MPa and 1% elongation between the top and the bottom of the billet when aging was performed at 175°C for 4h; the strength and ductility gradients were reduced to 20 MPa and 0,5% respectively by increasing the aging time to 6h. Microstructure investigations performed by scanning electron microscopy confirmed the different evolution of Silicon particles and precipitated particles at different height of the bars.
Non-Vacuum Fabrication of Bandgap-Controlled CZTGS Alloy Films Using CZTS+CZGS Mixed Nanoparticle Inks
Authors: Hamanaka Yasushi , Matsumoto Kojiro
Published: January 2021

Semiconductor alloy films of Cu2ZnSn1-xGexS4 (CZTGS) were prepared by deposition and sintering of mixed nanoparticle suspensions composed of Cu2ZnSnS4 (CZTS) and Cu2ZnGeS4 (CZGS) nanoparticles with 1-dodecanethiol surfactant. Colloidal CZTS and CZGS nanoparticles were synthesized via the liquid-phase route and used without post-processing treatment. The CZTGS films are crystallized in the form of kesterite structures and form an alloy of CZTS and CZGS without an apparent phase separation. The Sn/Ge ratios in the alloy films were finely controlled by tuning a mixing ratio between CZTS and CZGS nanoparticles. The bandgap energy of the CZTGS film systematically increased from 1.6 to 2.1 eV as the Ge-substitution for Sn in the films proceeded, which indicates the potential of the fabrication method in the manufacture of bandgap-tuned multinary semiconductor thin films.
Effect of the Morphology, Size, Distribution and Homogeneity of Carbides and Matrix on Wear Resistance in High Cr-Alloys White Cast Iron
Authors: Camurri Carlos , Maril Jasmín , Romero Eric
Published: January 2021

The aim of this work was to study the wear behavior of high-chromium white cast iron of families ASTM A-532 II (B, D) and III A, used in mining equipment, in order to establish relationships between the wear resistance, hardness and microstructure of the alloys, with the ultimate purpose of predicting their resistance to abrasion. Samples from these cast irons were subjected to mechanical wear tests by rotating drum, then their micro/macro hardness was measured and microstructure analyzed by optical and scanning electron microscopy .It was found that when the macroscopic hardness differences were significant there was a strong correlation between the hardness and the loss of mass due to abrasion-impact wear. By contrast, when the alloys had similar hardness, the wear resistance was determined by morphology, size, and the distribution and connectivity of carbides and matrix and therefore was not predictable by an only simple hardness test.
Corrosion Resistance of Mg Alloy with High Zn Concentration Including Impurity Cu
Authors: Ikoma Masato , Morishige Taiki , Kikuchi Tetsuo , Yoshida Ryuichi , Takenaka Toshihide
Published: January 2021

Mg alloys are very attractive materials for transportation industry due to their toughness and lightness. Recycling Mg alloys is desired for energy saving that otherwise would be required to produce its primary metal. However, secondary produced Mg tends to contain a few impurity elements that deteriorate its corrosion resistance. For example, contamination of Mg alloy by Cu induces second phase of Mg2Cu and it works as strong cathode, resulting in the corrosion rate rapidly increasing. It was previously reported that the corrosion resistance of Mg with impurity Cu was remarkably improved by addition of alloying element Zn. Addition of Zn into Mg formed MgZn2 phase and incorporated Cu into MgZn2 phase instead of Mg2Cu formation. In this way, since Zn serves to improve the corrosion resistance of Mg, Mg alloy with high Zn concentration may form a lot of MgZn2 and may have better corrosion resistance even with high Cu concentration. In this work, the corrosion behavior of Mg-6mass%-1mass%Al (ZA61) with different Cu content up to 1mass% was investigated. As a result, ZA61-1.0Cu had much lower corrosion rate compared to Mg-0.2%Cu and the corrosion rate was almost the same as that of pure Mg.
Parametric Study of Pulse Arc Welding (PAW) and Laser Beam Welding (LBW) Techniques for Electrical Vehicle Battery Cells
Authors: Iqbal Naveed , Nath Subhasisa , Coleman Alison E. , Lawrence Jonathan
Published: January 2021

Electrical vehicles (EV) offer the automotive industry the potential to meet future emission targets by developing large battery systems. These battery systems require several thousand single battery cells to be connected together. The battery cells are complex assemblies of dissimilar materials with very low thicknesses, which presents a significant challenge during the joining process, especially welding. We have investigated the performance of laser beam welding (LBW), as well as pulsed arc welding (PAW) for joining 0.3mm thickness nickel coated copper to 0.7mm thickness mild steel. The parametric study for good quality lap welds based on high tensile strength, was performed. The weld microstructure was investigated using optical, as well as scanning electron microscopy (SEM). The mechanical performance of the weld samples was characterized through tensile testing and micro hardness measurements to establish the microstructure property relationship. The maximum tensile strength measured for specified weld geometries was 660N for LBW and 496N for PAW. A significant increase in the hardness was measured in the weld nugget due to the formation of Cu-Fe composite microstructure
Promising Bendability of a New As-Rolled Medium-Carbon, Low-Alloy Steel with Isothermal Upper and Lower Bainitic Microstructure
Authors: Javaheri Vahid , Kaijalainen Antti , Pallaspuro Sakari , Porter David A. , Kömi Jukka I.
Published: January 2021

Bending behavior of a new thermomechanically processed low-alloy steel containing 0.40 wt.% carbon has been investigated. The processing included laboratory hot rolling to 10 mm thick strips followed by direct quenching to different quench-stop temperatures followed by slow furnace cooling to room temperature stimulating hot strip mill processing. The final microstructures were upper and lower bainite with yield strengths of a ~700 and ~1200 MPa, respectively. Local microstructures were characterized using a field-emission scanning electron microscope, microhardness profiles were measured, and bendability was determined using three-point brake press bending. The minimum applicable punch radius for a defect-free bend was 28 mm (2.8 times thickness) for the high-strength lower bainitic microstructure, while it was much smaller, i.e. 20 mm (2.0 times thickness) for the lower strength upper bainitic microstructure. Fractographic examination of the cracked surfaces revealed a more ductile fracture behavior for the upper bainitic microstructure.
Study on Forging Permeability of 06Cr19Ni9NbN Steel during Hot Deformation
Authors: Jiao Yong Xing , Liu Jian Sheng , Zhang Xue Zhong
Published: January 2021

The hot compression tests of 06Cr19Ni9NbN steel were conducted at strains rate of 0.005-5s-1 and temperature of 900-1200 °C on Gleeble1500 thermal mechanical simulation tester. Based on stress-strain data, processing maps of the steel were established. According to the results of processing maps, the optimal process parameters of hot compression were obtained, which lies in the temperature range of 1000-1200°C and strain rate of 0.005-0.1s-1. And then, the process of plane strain compression of 06Cr19Ni9NbN steel was investigated and carried out at the temperature of 1000-1200 °C and reduction ratio of 10%-50%. After the hot compression tests, the room temperature tensile tests were carried out. The results indicated that the grain size and the mechanical properties gradually become stable when the reduction ratio increases to 30%, 34% and 40% at 1200 °C, 1100 °C and 1000 °C, respectively. Finally, a new model was presented to describe critical forging penetration efficiency, which is significant to optimize the steel forging process. Furthermore, the calculated results based on this new model were consistent with experimental results, indicating that the model is suitable to predict the critical FPE for the steel.
Optimising Computational Fluid Dynamic Conditions for Simulating Copper Vertical Casting
Authors: Jones Thomas David Arthur , Strachan Richard I. , Mackie David M. , Cooper Mervyn , Frame Brian , Vorstius Jan B.
Published: January 2021

A 2-D finite volume Computational Fluid Dynamic (CFD) model, using Ansys Fluent vR.1 of a vertically oriented upwards continuous casting (VUCC), was investigated for 8 mm, oxygen free copper (OFCu). The simulations enabled the mapping of the cast OFCu solidification front (SF) interface from liquid to solid. Optimisation of the simulation parameters were investigated which included mesh size and the Ansys specific ‘mushy zone’ constant (Amush), which is used to account for fluid flow dampening at SF within the model. Observations of the SF, the change in fluid volume in the die, the simulation convergence and the total simulation time, revealed that the optimised casting parameters were for mesh size 1×10-4 m and Amush 106 kg/m3s. These parameters were compared with the cast rod and highlighted qualitatively the relationship between grain growth direction and SF position during a casting pulse cycle.
Austenitic Grain Size Effect on the Phase Transformation of a 7.0% Cr Steel for Forging
Authors: Coletti Roberto , Di Schino Andrea , Mengaroni Sabrina , Neri Stefano
Published: January 2021

In this paper the effect of normalizing and tempering (N&T) thermal treatment on mechanical properties of a novel 7.0% Cr steel for forged components is studied. The main innovation is in the increased hardenability following the higher Cr content with respect to the more common 5% Cr steel allowing to lower the content of other chemical elements aimed to achieve the target mechanical properties. Results show that in the case of 7.0% Cr steel, following the high intrinsic hardenability, the austenitic grain size effect on microstructure after cooling is really poor.
Effect of Microstructure on Joint Strength of Fe/Al Resistance Spot Welding for Multi-Material Components
Authors: Kumamoto Koki , Shohji Ikuo , Kobayashi Tatsuya , Iyota Muneyoshi
Published: January 2021

The effects of welding conditions such as the electrode type and welding current were investigated on the microstructure and joint strength of the resistance weld of A5052 and GA590. The reaction layer formed at the joint interface was inferred to consist of Fe-Al based intermetallic compounds (IMCs) which are FeAl, FeAl2, Fe2Al5 and FeAl3 by quantitative analysis. Although the thickness of the IMCs layer decreased from the center of the nugget towards the edge of it. When the DR type electrode was used, the cross tensile force became higher than those of the joints formed with the R type one. This is because the thickness of the reaction layer formed at the nugget end of A5052 was thin in the case of the DR type electrode. Also, it was found that cross tensile force increases when the thickness of the reaction layer is thin by multiple regression analysis.
Dynamic Recrystallization Mechanisms of Nickel Niobium Alloys during Hot Working
Authors: Matougui Nadjoua , Fares Mohamed Lamine , Piot David
Published: January 2021

This present work examines the influence of niobium in solid solution on the microstructural evolution of pure nickel at various deformation conditions. On this purpose, high-purity nickel and six model nickel-niobium alloys (Ni–0.01, 0.1, 1, 2, 5 and 10 wt. % Nb) were subjected to hot torsion test to large strains within the temperature range from 800 to 1000 °C at strain rates of 0.03, 0.1 and 0.3 s–1. Microstructural analyses were carried out using both optical and scanning electron microscopy-based electron back-scattered diffraction technique. The overall results showed the key role played by the Nb amount when coupled with various DRX mechanisms involved, i.e. DDRX, CDRX, and GDRX with respect to the prescribed deformation conditions, in reducing grain size and retarding DRX kinetics from which the microstructures of the examined materials such as Ni 2 and 10 wt. % Nb were seen evolving in different ways. In all these deformed materials, a transition from discontinuous dynamic recrystallization to continuous dynamic recrystallization was observed at low temperature and high strain rate whereas only discontinuous dynamic recrystallization occurred at high temperature.
Improving Mechanical Properties of Twin-Roll Cast AZ31 by Wire Rolling
Authors: Moses Marie , Ullmann Madlen , Kawalla Rudolf , Prahl Ulrich
Published: January 2021

Since 2018, the institute of metal forming has been studying the novel twin-roll casting (TRC) of magnesium wire at the pilot research plant set up specifically for this purpose. Light microscopic and scanning electronic investigations were carried out within this work and show the unique microstructure of twin-roll cast AZ31 magnesium alloy with grain sizes of about 10 μm ± 4 μm in centre and 39 μm ± 26 μm near the surface of the sample. By means of a short heat treatment (460 °C/15 min), segregations can be dissolved and grain size changes in centre to 19 μm ± 12 μm (increase) and near the surface to 12 μm ± 7 μm (decrease). Further, the mechanical properties of the twin-roll cast and heat-treated wire were analysed by tensile testing at room temperature. By heat treatment, the total elongation could be increased by a third whereas the strength decreases slightly. In heat-treated state, no preferred orientation is evident. In addition to the twin-roll cast and the heat-treated condition, the rolled state was analysed. For this purpose, the twin-roll cast wire was hot rolled using an oval-square calibration. After hot rolling, a dynamic recrystallization and grain refinement of the twin-roll cast wire could be achieved. It can be seen, that an increase in strength as well as in total elongation occur after wire rolling. Beside this, a rolling texture is evident.
Preliminary Development of Cold Spray Procedures for Nickel Aluminum Bronze Casting Repair
Authors: Munro Cameron , Vo Phuong , Guerreiro Bruno
Published: January 2021

Nickel aluminum bronze (NAB) castings possess favourable combinations of strength and resistance to corrosion, biofouling and cavitation/erosion, and so have long been used in naval applications. Nonetheless, in seawater environments NAB castings are susceptible to selective phase corrosion and so such components periodically require either replacement, which is very costly, or repair. However, repairs involving traditional, high heat input welding operations can lead to distortion and microstructural changes that unacceptably degrade NAB corrosion performance, and so repairs are not commonly performed. In the present work, cold spray is explored as an alternative for NAB (alloy CuAl9Fe5Ni5) repair without excessive distortion or base metal degradation, and preliminary results of its performance reported. Suitable cold spray parameters have been determined using an iterative approach by analyzing deposits in terms of microstructure, porosity and adhesion to the substrate. It is intended that these parameters will later be used to create simulated repairs which can be more thoroughly characterized for strength, toughness and corrosion performance.
Implementation of Mental Health Services in Conflict and Post-conflict Zones: Lessons From Syria
Authors: Hamza Mohammad Khalid , Hicks Madelyn Hsiao-Rei
Published: January 2021

Objective: We describe the challenges confronted and lessons learned in implementing mental healthcare during the Syrian war to inform effective services for conflict-affected Syrian populations. Materials and Methods: We searched the academic and gray literature. We draw on the experiences of Syrian-American mental health professionals with nine years of experience providing clinical and programmatic mental healthcare in combat settings, siege, internally displaced person camps, and refugee camps. Results: Collaboration with nonprofessional personnel was essential due to the shortage of formally trained mental healthcare professionals in Syria. The use of psychological and diagnostic terms increased stigma, whereas asking about the patient’s identified problem, “suffering,” or “challenges” supported engagement. War-related trauma and horizontal violence commonly affect Syrian children, adolescents, and adults. Resilience and engagement were enhanced by sensitivity to patients’ dignity, religious acceptance, and faith. Conclusions: The Syrian war remains an ongoing public health and humanitarian crisis in which mental healthcare must adapt rapidly to specific needs and resources of the patient and community. Psychiatrists can increase the acceptability and efficacy of their care by being sensitive to Syrian patients’ experiences of horizontal violence, loss of dignity, stigma, worldviews in which religion and faith may be important sources of resilience, and culturally acceptable modes of communication.