bluuebunny/crossref_metadata_2025 huggingface dataset:
Cold Swaging and Recrystallization Annealing of Ti-Nb-Ta-Zr-O Alloy - Microstructure, Texture and Microhardness Evolution
Authors: Preisler Dalibor , Stráský Josef , Harcuba Petr , Halmešová Kristýna , Janeček Miloš
Published: December 2018

Metastable β-Ti alloy Ti-35.3Nb-7.3Zr-5.7Ta-0.7O (wt. %) shows properties desirable for use as an implant material. However, very large grains (with the size of 0.5 – 3 mm) negatively affect the strength and fatigue resistance. Combination of cold-swaging and recrystallization annealing is used to refine the microstructure. Microstructure after cold swaging and after annealing is studied using scanning electron microscope by electron back-scatter diffraction measurements. Grain size and texture is determined and homogeneity of deformation inside the grains is discussed. Microhardness maps are measured in the cold-swaged samples. It is found that microhardness and thus also the deformation is higher in the center of each rod however the grains retain their original size. Annealing leads to recrystallization that is complete or nearly complete at the temperatures of 1000°C and more. Annealing at 1000°C for 15 min yields grain size of around 100 μm. This grain size is believed to increase the fatigue performance to satisfactory values.
Laser Beam Welding of IN792 DS Superalloy
Authors: Barbieri Giuseppe , Cognini Francesco , Bonaiuto Vincenzo , Montanari Roberto , Richetta Maria , Varone Alessandra
Published: December 2018

The main purpose of the investigation is to develop reliable methods to repair IN 792 superalloy components by Laser Beam Welding (LBW). The jet engine structural components made of nickel-base superalloys are subjected to high stresses and severe environmental, therefore crack may occurs during in-service life. Considering the high cost of this components they are often repaired by welding. Welds must be made: (i) by altering as little as possible the original microstructure; (ii) without introducing in the molten (MZ) and heat affected (HAZ) zones relevant residual stresses; (iii) without producing cracks in MZ and HAZ; (iv) without massive chemical segregation; (v) without elemental diffusion changing the composition of g and g’ phases.LBW has been used to realize seams on 2mm-thick plates of directionally solidified (DS) IN792 superalloy. An Yb fiber laser has been employed in present experiments and the molten pool was shielded from oxidation through a patented equipment. A grid of samples has been prepared by varying the pass speed v from 1 to 2.0 m/min with pre-heating temperature of 200 °C. The microstructural changes occurring in the microstructure of molten zone (MZ) and heat affected zone (HAZ) have been investigated by optical and scanning electron microscopy (SEM) observations and energy dispersion spectroscopy (EDS).
Microstructure and Mechanical Properties of a Cu-Pd-Ag Alloy Wire with Aging Treatment
Authors: Iwamoto Chihiro , Watanabe Fumio , Koitabashi Risei
Published: December 2018

Cu-Pd-Ag alloy is widely used in electronic device applications due to its relatively low electric resistance. To obtain higher strength wire, age-hardening is usually conducted to this alloy wire. However, the detailed hardening mechanism of Cu-Pd-Ag alloy was not clarified enough. In the present paper, we investigated the microstructure and hardness of the Cu-Pd-Ag alloy wire with aging treatment. Original alloy contained many rods with an Ag-rich α phase extended along the wire direction in a Cu-rich α phase matrix. After heat treatment of 623K with 1 hour, the matrix was transformed to the β phase contained many elongated α2 phases as nanolamellar structure. Many β’ phase precipitated in the rods. Hardness measured with nanoindentation test showed that the matrix had a higher value than that of the rods. In the Cu-Pd-Ag alloy wire, the nanolamellar structure of the matrix was revealed to contribute to the hardening of the wire.
Microstructure of Co-Cr-Fe-Mn-Ni-Cu and Co-Cr-Fe-Mn-Ni-Ag High Entropy Alloys with Liquid Phase Separation
Authors: Nagase Takeshi
Published: December 2018

Liquid phase separation is a common phenomenon observed in various types of condensed matter, including metals. The microstructure of Co-Cr-Mn-Fe-Ni-Cu and Co-Cr-Fe-Mn-Ni-Ag high entropy alloys (HEAs) with liquid phase separation was investigated. Dual fcc phases were observed in CoCrFeMnNiAg, CoCrFeMnNiCu, and CoCrFeMnNiCu2 HEAs. A macroscopically phase separated structure formed via liquid phase separation was observed in CoCrFeMnNiAg HEA, and conventional dendritic structures were observed in CoCrFeMnNiCu and CoCrFeMnNiCu2 HEAs.
Prediction of the Hydrogen-Induced Damage to Ultra-High Strength Steel Concepts
Authors: Schaffner Tobias , Hartmaier Alexander , Pohl Michael , Kokotin Valentin
Published: December 2018

The hydrogen-induced damage behavior of ultra-high strength steels (UHSS) has been predicted by a combination of experimental and numerical investigations. Firstly, the resistance against hydrogen-induced failure was examined by slow strain rate tests (SSRT) using various sample geometries and hydrogen contents. Secondly, the hydrogen distribution and loading conditions during the tensile test were calculated by means of the finite element method (FEM). Finally, a combination of various damage models was applied and validated by further SSRT. The main result of this study is a failure prediction model, which considers local stress and strain conditions, as well as hydrogen content.
Activities of Non-Basal Slips in Deformation of Magnesium Alloy Single and Poly Crystals
Authors: Ando Shinji , Rikihisa Hiroaki , Tsushida Masayuki , Kitahara Hiromoto
Published: December 2018

In this study, to investigate effects of yttrium and other elements for non-basal slips, magnesium alloy single crystals were stretched parallel to basal plane in various temperatures, and polycrystalline magnesium alloys were also tested to estimate contribution of non-basal slips to their tensile deformation behaviour. In pure magnesium single crystals, second order pyramidal (c+a) slip (SPCS) was observed at 298K. Above room temperature, first order pyramidal (c+a) slip (FPCS) was active. In the Mg - (0.6-0.9) Y alloy single crystals, FPCS was observed at 77K to 298K, while yield stress of the Mg-Y alloy single crystals was higher than that of pure magnesium. In tensile test of polycrystalline specimen, slips lines of non-basal slip systems such as SPCS, FPCS and prismatic slip were observed even at yielding in addition to basal slip lines. Among the non-basal slips, activities of FPCS and prismatic slips were increased with increasing strain in Mg - Y alloy polycrystals. Our study suggested that active non-basal slip system in tension parallel to basal plane is (c+a) pyramidal slip and enhanced ductility of magnesium - yttrium alloy would be caused from increased activity of FPCS by yttrium addition.
Study of Mechanical Degradation and Microstructural Characterization in a Ni-Based Superalloy Component of a Gas Turbine
Authors: Avila-Davila Erika O. , Lopez-Hirata Victor M. , Saucedo-Muñoz M.L. , Palacios-Pineda Luis M. , Ramirez-Vargas Ignacio , Cueto-Rodriguez Maria M. , Trapaga-Martinez Luis G. , Alvarado-Orozco Juan M.
Published: December 2018

The microstructural characterization of a blade made of Ni-based superalloy was carried out and discussed. The blade was removed from service, of a gas turbine, due to preventive maintenance. This component was studied on different cross sections according to the surface temperature obtained by ANSYS software. The cross sections were characterized by Optical Microscopy (OM), Scanning Electron Microscopy (SEM) and High Resolution Scanning Electron Microscopy (HR-SEM). It was determined that the maximum value of total deformation is 0.001717 mm, located in the surface upper section of the blade, which not correspond to the section with the highest value of temperature calculated with ANSYS software. These results were consistent with the rafted microstructure observed at the upper region of the blade. Microcavities close to the MC carbides with a size of about 40x10-6 m were also observed. The mechanical behavior of the Ni-based superalloy was studied by Rockwell Hardness testing (RHT). So, morphological changes were identified in the occurrence of the strengthening precipitated, γ', according to the operating conditions: stress and temperature. The average radius of the γ' precipitated was obtained by computer image analysis using ImageJ software. No clear relationship was found between the hardness values obtained and the coarsened γ' precipitated. A bimodal occurrence of coarsened γ' particles was identified distributed through γ matrix by HR-SEM. Thus, this study was carried out with the purpose to identify the critical parameters that promote microstructural changes in the Ni-based superalloy and therefore affect the mechanical behavior in this turbine blade.
Development of Low-Cost Titanium-Manganese Shape Memory Alloys
Authors: Ikeda Masahiko , Ueda Masato
Published: December 2018

Ti alloys are attractive materials for such applications, they are expensive due to the costly alloying elements such as Nb or Mo. The present authors have adopted Mn as a low-cost alloying element, and melted Ti-7, 7.5 and 8 mass%Mn-1.5 and 3mass%Al alloys using a laboratory-scale arc furnace. All specimens prepared from bottom ingots were heat treated at 1223 K for 3.6 ks and quenched in ice water. In the 7 and 7.5Mn-Al alloys, the β phase and orthorhombic martensite were identified using X-ray diffraction. In the 8Mn-Al alloys, only the β phase was identified. In the 7, 7.5, and 8Mn-Al alloys, the electrical resistivity at room and liquid nitrogen temperature increased with increasing Al content due to dissolution of Al into the β phase, whereas the Vickers hardness decreased with increasing Al content due to decreasing formation of athermal omega by the addition of Al. Heat treatment at 673 K for 60 s almost completely returned deformed Ti-7 and 7.5Mn-3Al specimens to their original shapes, and heat treatment at 773 K for 60 s almost returned deformed Ti-8Mn-Al specimens to their original shapes.
Ultra-Fine Grained Ti-15Mo Alloy Prepared by Powder Metallurgy
Authors: Veverková Anna , Kozlík Jiří , Bartha Kristína , Chráska Tomáš , Stráský Josef
Published: December 2018

Ti-15Mo alloy belongs to metastable β-Ti alloys that are currently used in aircraft manufacturing and Ti15Mo alloy is a perspective candidate for the use in medicine thanks to its biotolerant composition. In this study, Ti15Mo alloy was prepared by advanced techniques of powder metallurgy. The powder of gas atomized Ti-15Mo alloy was subjected to cryogenic milling to achieve ultra-fine grained microstructure within the powder particles. Powder was subsequently compacted using spark plasma sintering (SPS). The effect of cryogenic milling on the microstructure and phase composition of final bulk material after SPS was studied by scanning electron microscopy. Sintering at 750°C was not sufficient for achieving full density in gas atomized powder, while milled material could be successfully sintered at this temperature. Alpha phase particles precipitated during sintering and their size, as well as the size of beta matrix grains, was strongly affected by the sintering temperature.
Melting and Solidification Behavior of High-Strength Aluminum Alloy during Selective Laser Melting
Authors: Kyogoku Hideki , Yamamoto Kohei , Ikeshoji Toshi Taka , Nakamura Kazuya , Yonehara Makiko
Published: December 2018

Additive manufacturing (AM) technology has been dramatically attracted attention because of advantages in building free-shaped parts and simplification of manufacturing process. Recently the most relevant alloys, such as TiAl6V4, Inconel 718, AlSi10Mg and so on, are able to manufacture the parts using metal AM technology. However high-strength 2024, 6061 and 7075 aluminum alloys are difficult to fabricate using selective laser melting (SLM) owing to solidification cracking during solidification. In this research, the melting and solidification behaviors of AlSi10Mg alloy during SLM process were observed under various fabrication conditions of laser power and scan speed using a high-speed camera. It was found that the melting and solidification behavior of the alloy is greatly different by the fabrication conditions. And also the mechanism of solidification cracking in 2024 and 6061 aluminum alloys is investigated by the observation of the surface morphology and microstructure of the alloys using OM, SEM and EDS, comparing with Al10SiMg alloy. As a result, crack-free 2024 and 6061 aluminum alloy parts can be obtained by fabrication at the higer enrgy density.
Impact of Hydrogen Content on the Thermal Stability of Hydride Phases in Zirconium Alloys
Authors: Conforto Egle , Girault Patrick , Berziou Cyril , Lotte Guillaume , Milet Rémy , Cohendoz Stephane , Feaugas Xavier
Published: December 2018

The fast and spontaneous hydrogen diffusion in HCP structures leads to the hydride precipitation. It is often pointed as causing embrittlement and rupture in zirconium alloys for applications in the nuclear industry. In our previous works TEM, DSC, SEM-EBSD and XRD were used to study the hydride stability after many precipitation-dissolution thermal cycles as well as the crystallographic hydride phase nature and the hydride-substrate crystallographic orientation relationships as a function of the hydrogen content. Results showed that the evolution of the dissolution and precipitation energies is correlated to the concentration of hydrogen atoms available to reprecipitate, which is submitted to a diffusion controlled by the misfit dislocation migration. In the present work in-situ TEM thermal cycling was performed in order to locally investigate the crystallographic stability of zirconium hydrides of different structures after many dissolution-reprecipitation cycles.
Temperature Dependence of Mechanical Properties in Dual Phase Ti-6Al-4V
Authors: Anne Bhargavi Rani , Tanaka Masaki , Morikawa Tatsuya
Published: December 2018

The temperature-dependent mechanical property of a forged Ti-6Al-4V (bimodal structure; α and α+ß phases) was investigated. Tensile test was performed at a wide range of temperatures between 77K to 550K. Fatigue test was also performed with corner notched specimens at the temperature range between room temperature and 550K. The temperature dependency of both the yield stress and activation volume was established from the tensile tests. The strong dependency of yield stress and activation volume was observed with respective to the temperature. At lower temperatures, from 77K to 250K, there was a decrease in yield stress with the increase in temperature, whereas abnormality in the yield stress was observed approximately at 275K, and the yield stress was decreased again with the increase in temperature at 325K. Activation volume was increased with increasing the temperature. The activation volume also shows abnormality at the temperatures where the abnormal trend was observed from yield stress. The reasons for the change in yield stress and activation volume with temperature were studied in detail.
Effect of Shearing Distance on Mechanical and Electrical Properties for Cu-11Mn-4Ni Thin Plate Formed by Compression Shearing Method at Room Temperature
Authors: Nakayama Noboru , Inoue Hayato , Kusunoki Hideharu , Horita Masaomi , Kumeda Yoshitaka , Nakamura Keishi
Published: December 2018

ince the temperature coefficient of resistance of Manganin (Cu-12Mn-2Ni) is extremely small, Manganin plate are used for resistors, especially shunts for current sensing.Generally, the melting and casting is used as a method to make an alloy such as Manganin. Further, the Manganin used as resistive material is produced by rolling after casting. Since such manufacturing processes have heating steps, long molding time is necessary and temperature control is important.In recent years, Cu-11Mn-4Ni powder has been developed. If manganin plate can be produced directly from alloy powder, simplification of the manufacturing process can be expected. A powder metallurgy is used as a method of solidifying and shaping the alloy powder. However many pores are generated in the sample because of using a binder. Therefore, the resistance value of the alloy fabricated through the method may not be stable.The Compression Shearing Method at Room Temperature (COSME-RT) is one of solutions to achieve the high density forming. In COSME-RT alloy powders are simultaneously loaded by a shearing force and a compressive stress in air at room temperature to form a plate. In the process, temperature control is unnecessary and the manufacturing time becomes shorter.In the present study, the fabrication of Cu-11Mn-4Ni plate is carried out by compression shearing method at room temperature and mechanical and electrical properties of the plate are evaluated.
Explosion Welding: Process Evolution and Parameters Optimization
Authors: Costanza Girolamo , Tata Maria Elisa , Cioccari Diego
Published: December 2018

The development of explosion welding (EXW) technology underwent a stop as soon as it was introduced, however, in the recent years an increasing interest was found due to the wide range of materials which can be welded, similar and especially dissimilar ones. In addition to the high quality, such welded joints show a good compromise among the involved materials properties. Literature does not provide a comprehensive understanding of the whole mechanism and occurring phenomena but is mostly limited to analyse just some process parameters, like the investigations on joint properties that can be achieved if process takes place under vacuum or open air. In this work some key points are discussed to describe the evolution step of the process and the innovations introduced like the MIL (metallic-intermetallic laminate) composites for aerospace industry. Process parameters are analyzed to highlight the positive and negative aspects, the experiments in the laboratory will be described to confine the explosion to the joint and in particular to minimize the explosion energy and to improve the efficiency of the technique. At last some significant applications where this technique is widely used are showed.
Deformation Twinning Behavior in High Ni-Austenitic Materials
Authors: Nordström Joakim , Siriki Raveendra , Moverare Johan , Chai Guo Cai
Published: December 2018

Deformation twinning behaviors have been studied in high Ni alloys, Alloy 28 or Sanicro 28 and Alloy 625 at RT and at cryogenic temperature. The microstructures were evaluated using SEM-EBSD. Some constitutive approach has also been used in the discussion on the deformation twinning in high Ni-alloys. The results show that deformation twinning can occur in high Ni alloys depending on the chemical composition, strain range and stress conditions. TWIP can occur in the Ni based superalloy Alloy 625 at cryogenic temperature, which increases both strength and ductility. This is the first report of this phenomena for this alloy. Deformation twinning in high Ni alloys occurs heterogeneously in the material, depending on crystallographic parameters such as grain orientation and Schmid factor. Formation of deformation twins can lead to high texture in the material, which will contribute to the increase of strength. The mechanisms for the formation of deformation twins in high Ni alloys have been discussed.
Micro-Nanostructured Silicone Rubber Surfaces Using Compression Molding
Authors: Maghsoudi Khosrow , Momen Gelareh , Jafari Reza , Farzaneh Masoud , Carreira Tony
Published: December 2018

A facile method is introduced for production of micro-nanostructured silicone rubber surfaces by means of direct replication using a compression molding system. The fabricated samples possessing surface roughness display water contact angle of more than 160o and contact angle hysteresis (CAH) and sliding angle of less than 5o. Such low surface wettability of silicone specimens verifies the induced superhydrophobic property. Chemically etched aluminum surfaces could work excellently as templates whose patterns were replicated on the rubber surfaces successfully. Various etching conditions were examined. Surface characterization techniques revealed the presence of micro-nanostructures on the produced silicone surfaces.
Effects of Surface Structure and Hydrogen on the Fatigue Strength of Electroless Nickel-Phosphorus Plated Al-2%Cu Alloy
Authors: Kanadani Teruto , Nagata Norihito , Horikawa Keitaro , Nakagawa Keiyu , Hino Makoto
Published: December 2018

In this study, the effect of the surface structure and hydrogen on the fatigue strength of electroless Ni-P plated Al-2%Cu alloy was investigated. As the results, the following points were clarified. Large precipitates were recognized near the specimen surface of the furnace-cooled Al-Cu alloy, but these were not recognized in the aged Al-Cu alloy. Fatigue strength of the Al-Cu alloy specimen subjected to Ni-P plating after a furnace cooling treatment was overall reduced rather than one of the non-processed specimens. Fatigue strength of the Al-Cu alloy specimen subjected to Ni-P plating after the aging treatment showed a clear increase in comparison to one of non-processed materials. In the Al-2%Cu alloy specimens subjected to Ni-P plating after the furnace cooling treatment or aging treatment, a clear hydrogen desorption was recognized. On the other hand, there was only hydrogen desorption from a few of the non-processed specimens. It is considered that the poor fatigue strength of the plating materials is mainly due to the interaction between the surface precipitates and hydrogen gas.
A Laser Shock Approach to Cold Spray
Authors: Delloro Francesco , Zagouri Didier , Boustie Michel , Jeandin Michel
Published: December 2018

Cold spray utilizes supersonic jets of compressed gas to accelerate powder particles at high velocities. A coating is formed on a substrate by the impact and deformation of particles. Laser Shock consists in illuminating a sample with a pulsed laser to generate a high pressure shock. Cold spray and laser shock are extremely dynamic processes (time scales of about 10-100 ns). In this paper, applications of laser shock for the study of cold spray are presented. A powder particle of a given size and morphology can be laser shock accelerated at cold spray velocities, finally hitting a substrate in a controlled experimental simulation of the process. Results allow also the characterization of powder materials, through the comparison of deformed particles with numerical impact simulations and the fitting of a plasticity model. Two main advantages compared to the split-Hopkinson pressure bar emerge: deformation rates are closer to cold spray conditions and powders are directly tested, rather than macroscopic cylinders. Laser shock can also be used to measure adhesion and internal cohesion of cold-sprayed coatings (LAser Shock Adhesion Test, LASAT). Cold LAser Shock Spray (CLASS), consisting in laser shocking a coating to re-spray it, can be used to characterize property gradient within a coating or as a new spraying process. Laser shock techniques can prove beneficial for the knowledge of powder materials, which is key for advances in cold spray and other powder based processes. Moreover, the combination of the two techniques could lead to hybrid processes.
Foaming and Compressive Properties of A359/SiCP Metal Matrix Composites
Authors: Nadella Ravi Kumar , Ginuga Jagan Reddy , Pati Sampath , Gokhale Amol
Published: December 2018

In this work, a commercial MMC (A359-20% SiCP) was remelted, diluted to different particle contents (5 to 20 vol. %), and foamed at a fixed temperature using titanium hydride. In general, excellent foamability could be obtained for all SiC contents. Foam stability (retention of expansion), on the other hand, depended on SiC content. Remelting and diluting procedures also influenced the foam stability on account of varied oxide contents generated upon impeller stirring. The foam quality, in terms of cell wall integrity, improved with increasing SiC content. Despite the defect levels, good compression properties were obtained in these foams, which are close to model predictions. Overall, this system is very promising for producing good quality foams by melt processing technique.
Effect of Processing Route on Microstructure and Mechanical Properties of a Ti-3Al-2.5V/TiB Composite
Authors: Ropars Ludovic , Dehmas Moukrane , Aeby-Gautier Elisabeth , Tricker David , Schuster Dominique , Gourdet Sophie
Published: December 2018

A Ti-3Al-2.5V matrix composite reinforced with 8.5 vol.% TiB was produced using a powder metallurgy route. Processing included the mechanical alloying of Ti-3Al-2.5V and TiB2 powders and Hot Isostatic Pressing (HIP) of the resultant composite powders, to produce a dense billet. These billets were subsequently extruded and/or subjected to various Conversion Heat Treatments (CHT), to complete the transformation of the TiB2 particles into TiB needles. The CHT was performed either before or after extrusion. Microstructures and tensile properties of the materials at each stage of the processing routes were investigated and compared to those of a non-reinforced Ti-3Al-2.5V material, manufactured by the same powder metallurgy route. It has been demonstrated that the processing routes have a great impact on the mechanical properties, through modifications of the matrix and reinforcement characteristics. Well-chosen processing routes lead to more ductile composites, though this gain in ductility leads to slightly lower stiffness and strength values. This study clearly demonstrates the possibility to produce, at an industrial scale, a ductile version of a highly reinforced titanium matrix composite, showing important application potential.
Joining of AlN and Al with Compositional Graded Layer by Centrifugal Mixed-Powder Method
Authors: Watanabe Yoshimi , Murase Masaki , Sato Hisashi , Tsukamoto Hideaki
Published: December 2018

In this study, joining of AlN and Al with compositional graded layer is made by centrifugal mixed-powder method (CMPM). The mixed-powder of AlN particles and Al particles is inserted into a spinning mold with bulk-shaped AlN, and then molten Al is poured into the spinning mold with the mixed-powder and bulk-shaped AlN. As a result, the molten Al penetrates into the space between the mixed-powder by the centrifugal force, and at the same time, the Al particles can be melted by heat from the molten Al. Then AlN and Al can be joined with compositional graded layer after solidification. Micromechanics-based analysis is also employed to understand the thermal stress relaxation by the compositional graded layer.
Tribological Properties of Aluminum and Silicon Borides at High Temperatures
Authors: Murakami Takashi , Korenaga Atsushi , Ohana Tsuguyori , Inui Haruyuki
Published: December 2018

In our present study, AlB12 and SiB6 plate specimens prepared by spark plasma sintering AlB12 and SiB6 powders, respectively, and their tribological properties were investigated in the temperature range of 25°C to 1000°C in air. Also, the micro Vickers hardness of the AlB12 and SiB6 plate specimens were evaluated in the temperature range of 25°C to 1000°C in an Ar gas atmosphere. It was found that both the steady friction coefficients of the AlB12 and SiB6 plate specimens were as low as 0.07 to 0.08 at 1000°C. According to XPS analyses, it was found that Al2O3 and B2O3 films were observed on the worn surfaces of the AlB12 plate specimens after sliding at 1000°C. On the other hand, SiO2 and B2O3 films were observed on the worn surfaces of the SiB6 plate specimens after sliding at the same temperature. It was also found that both the boride plate specimens exhibited micro Vickers hardness as high as 20 GPa in the temperature range of 25°C to 1000°C.
Spark Plasma Sintering of High-Energy Ball-Milled ZrB2 and HfB2 Powders with 20vol% SiC
Authors: Seetala Naidu , Prevo Cyerra L. , Matson Lawrence E. , Key Thomas S. , Park Ilseok I.
Published: December 2018

ZrB2 and HfB2 with incorporation of SiC are being considered as structural materials for elevated temperature applications. We used high energy ball milling of micron-size powders to increase lattice distortion enhanced inter-diffusion to get uniform distribution of SiC and reduce grain growth during Spark Plasma Sintering (SPS). High-energy planetary ball milling was performed on ZrB2 or HfB2 with 20vol% SiC powders for 24 and 48 hrs. The particle size distribution and crystal micro-strain were examined using Dynamic Light Scattering Technique and x-ray diffraction (XRD), respectively. XRD spectra were analyzed using Williamson-Hall plots to estimate the crystal micro-strain. The particle size decreased, and the crystal micro-strain increased with the increasing ball milling time. The SPS consolidation was performed at 32 MPa and 2,000°C. The SEM observation showed a tremendous decrease in SiC segregation and a reduction in grain size due to high energy ball milling of the precursor powders. Flexural strength of the SPS consolidated composites were studied using Four-Point Bend Beam test, and the micro-hardness was measured using Vickers micro-indenter with 1,000 gf load. Good correlation is observed in SPS consolidated ZrB2+SiC with increased micro-strain as the ball milling time increased: grain size decreased (from 9.7 to 3.2 μm), flexural strength (from 54 to 426 MPa) and micro-hardness (from 1528 to 1952 VHN) increased. The correlation is less evident in HfB2+SiC composites, especially in micro-hardness which showed a decrease with increasing ball milling time.
Development of Ultra-High Temperature Ceramics: From Monoliths to Composites
Authors: Julian-Jankowiak Aurélie , Mathivet V. , Justin Jean François , Guérineau Vincent
Published: December 2018

Regarding materials development, our studies have been mainly focused on ZrB2-SiC and HfB2-SiC compositions with TaSi2 or Y2O3 additions using hot pressing and spark plasma sintering. These additives have been used to decrease the sintering temperature and to improve the oxidation resistance. Interesting mechanical properties at room and high temperature have been measured. Moreover, excellent oxidation behaviors have been observed up to 2000-2200°C with Y2O3. Last developments are centered on the manufacturing of ultrahigh temperature ceramic matrix composites (UHTCMC) using slurry infiltration and pyrolysis for example. First results are encouraging.
Wear Behavior of Cenosphere Dispersed Titanium Composite Foam Developed by Powder Metallurgy Route
Authors: Majumdar D. Dutta , Mondal D.P. , Ghosh M. , Roy Choudhury Amit
Published: December 2018

The present study includes a detailed analysis of titanium based composite foam developed by powder metallurgy route and to understand the role of process parameters and the particle size of the space holder (cenosphere) on the kinetics and mechanism of wear. Cenosphere of varying particle size (<150 μm; 150-212 μm; > 212 μm) were mixed with titanium in a ratio of 1:3, compacted at 100 MPa and sintered at 1000°C and 1200°C for a period of 2,4 & 6 hrs in each temperature. The kinetics of wear and frictional coefficient of sintered composites were evaluated by reciprocating wear testing machine against diamond indenter at applied load of 10 N. The mechanism of wear was studied by a detailed analysis of the post wear microstructure. The composite foam with cenosphere particle size in the range of 150-212 μm showed minimum wear rate. The mechanism of wear was found to be a combination of adhesive and abrasive.
Additive Manufacturing of a CNT/Al6Si Composite with the Nanolaminated Architecture via Cold Spray Deposition
Authors: Xie Xin Liang , Xie Ying Chun , Tan Zhan Qiu , Chen Chao Yue , Wang Jiang , Li Zhi Qiang , Li Xiao Peng , Ji Gang , Liao Han Lin
Published: December 2018

Cold spraying (CS) is a solid-state layer-by-layer deposition technique, allowing to fabricate complex-shaped metallic components, such as metal matrix composites (MMCs). It has been demonstrated that introduction of a nacre-like nanolaminated architecture in man-made MMCs can perfectly beat the conflict between strength and ductility (toughness). In this work, the fully dense carbon nanotubes (CNTs) reinforced Al6Si (hereafter called CNT/Al6Si) MMC with the nanolaminated architecture is successfully realized by flake powder metallurgy followed by CS. It is revealed that the nanolaminated architecture, containing nanosized grains, is properly created in the CNT/Al6Si flaky powder by ball milling, which is then conserved in the CS-processed component. The harmful excessive formation of Al4C3 due to interfacial reaction is limited and structural integrity of initially incorporated CNTs is well retained.
Analyses of Texture and Deformation Mechanism in Fine-Grained Austenitic Stainless Steels by Electron Back Scatter Diffraction
Authors: Ishida Kyoichi , Matsuo Taku , Imafuku Muneyuki
Published: December 2018

We investigated texture evolution features in fine-grained austenitic stainless steels (JIS-SUS304) under tensile deformation. Three kinds of fine-grained specimens having average grain sizes, d =0.5 μm, 2 μm and 9 μm were prepared. The mechanical properties and phase transformation behaviors of fine grained specimens were compared to those of commercially available SUS304 ( d =16 μm). Tensile test showed increase of yield and tensile strength and decrease of work hardening rate and significant martensitic phase transformation in earlier stage of deformation for 2 μm specimen. These results suggest that simultaneous progress of the dynamic recovery of dislocations in γ-phase and the evolution of harder α’-phase owe the elongation and hardening respectively in fine-grained specimen. From the result of texture analysis, the texture evolution process was different from for each specimen, although the final orientation was almost the same. At the plastic instability stage, an increase of {112}<111>γ phase and a decrease of {112}<113>α’ phase occurred simultaneously for fine-grained 2 μm specimen whereas the opposite tendency was observed for 16 μm specimen. Such a grain size dependence of texture affects an extra ductility of SUS304 at the latter stage of deformation.
Engineering Solutions in Scale-Up and Tank Design for Metal Hydrides
Authors: Capurso Giovanni , Jepsen Julian , Bellosta von Colbe José M. , Pistidda Claudio , Metz Oliver , Yigit Deniz , Cao Hu Jun , Hardian Rifan , Strauch Anselm , Taube Klaus , Klassen Thomas , Dornheim Martin
Published: December 2018

A holistic approach is required for the development of materials and systems for hydrogen storage, embracing all the different steps involved in a successful advance of the technology. The several engineering solutions presented in this work try to address the technical challenges in synthesis and application of solid-state hydrogen storage materials, mainly metal hydride based compounds. Moving from the synthesis of samples in lab-scale to the production of industrial sized batches a novel process development is required, including safety approaches (for hazardous powders), and methods to prevent the contamination of sensitive chemicals. The reduction of overall costs has to be addressed as well, considering new sources for raw materials and more cost-efficient catalysts. The properties of the material itself influence the performances of the hydride in a pilot storage tank, but the characteristics of the system itself are crucial to investigate the reaction limiting steps and overcome hindrances. For this, critical experiments using test tanks are needed, learning how to avoid issues as material segregation or temperature gradients, and optimizing the design in the aspects of geometry, hull material, and test station facilities. The following step is a useful integration of the hydrogen storage system into real applications, with other components like fuel cells or hydrogen generators: these challenging scenarios provide insights to design new experiments and allow stimulating demonstrations.
Superhydrophobic and Highly Oleophilic Polystyrene Fibers (PS) with Delayed Freezing Time and Effective Oil Adsorption
Authors: Jafari Reza , Chameau Marc , Farzaneh Masoud , Momen Gelareh
Published: December 2018

We present an efficient and simple approach for preparing superhydrophobic-superoleophilic polystyrene (PS) fibers via electrospinning. Bead-on-string fibers from a 5% PS solution and micro-sized fibers from a 20% PS solution were combined to achieve a surface having very high contact angle (about 160°) and low contact angle hysteresis. The presence of bead-on-string fibers increases the superhydrophobicity of the sorbent. The micro-sized PS fibers improve the mechanical properties of the electrospun mat through their elastic and flexible behavior. An evaluation of wettability at a low temperature (-10 oC) showed a delayed freezing time for water droplets on the superhydrophobic surface. Water droplets on a polished aluminum surface froze more quickly (about 6 seconds) than droplets on the fabricated superhydrophobic surface (about 500 seconds). Finally, the oil adsorption capacity of the developed superhydrophobic PS fibers, which have a porous surface structure, showed values of 69.1, 69.3 and 61.2 g/g for canola oil, olive oil and motor oil, respectively.
The Avrami Kinetics of Dynamic Recrystallization in Nickel-Niobium Alloys
Authors: Matougui Nadjoua , Piot David , Fares Mohamed Lamine , Montheillet Frank , Jonas John Joseph
Published: December 2018

The flow curves determined on a series of Ni-Nb alloys are analysed. Six alloys containing Ni–0.01, 0.1, 1, 2, 5 and 10 wt. % Nb with pure Ni were tested in torsion at various strain rates within the hot forging temperature range. Under these conditions, large strains were attained, which permitted steady state flow to take place. The double-differentiation method is employed to define the critical strain for the initiation of DRX, leading to the evaluation of the strain hardening and dynamic recovery parameters. The relations obtained are compared to ones determined earlier using a least squares approach. It is shown that the two sets of relations do not differ appreciably. These results are employed to predict the Avrami kinetics of a range of Ni-Nb alloys strained at different temperatures and strain rates. The Avrami time exponents all fall in the range 1.0 to 5.0. The dependence of the time of half-softening, t50, on Nb content, strain rate and temperature is also derived under the same conditions.
A First-Principles Study of the Al (001)/Fe(0-11) Interface
Authors: Khalid Muhammad Zeeshan , Friis Jesper , Ninive Per Harald , Marthinsen Knut , Strandlie Are
Published: December 2018

Using a first-principles methodology we have investigated the interfacial and bonding characteristics of the Al(001)/Fe (0-11) interface. The Al/Fe interface model was developed using a face-to-face matching method. Among many possible interface structures, the Al (001)/ Fe(0-11) orientation relation gave the minimum lattice misfit along the a and b directions (a=b= -0.47%). Hence, this interface structure provided the minimum energy value and was used for this study. To predict the interface strength and stability, the work of separation and interfacial energy were calculated. Here, all systems were calculated under exactly the same conditions (k-point mesh, cutoff energy, lateral lattice strain etc). In order to predict the bonding nature at the interface, charge density difference plot was evaluated, which showed charge gain at the interface. The aim of this study is to describe the adhesive behavior between Al and Fe, provide some insights about strength and stability of this interface structure for galling, and provide reference interface system for Al/Fe welding.
3D FEM Simulation of the Effect of Cooling Rate on SDAS and Macrosegregation of a High Strength Steel
Authors: Brionne Gary , Loucif Abdelhalim , Zhang Chunping , Lapierre-Boire Louis Philippe , Jahazi Mohammad
Published: December 2018

Secondary dendrite arm spacing (SDAS) is a macrosegregation parameter directly linked to content of macrosegregation through cooling rates. The aim of this paper is to highlight the effect of cooling rate on the SDAS and macrosegregation patterns in a high strength steel. For this purpose, directionnal solidification in a cylinder was modeled with a plane-front solidification. Two cylinders were modeled with different boundary conditions (Tsurface = 1000°C and 1200°C). Using the FEM software Thercast, 3D macrosegregation maps were generated with thermomechanic algorithm taking into account metal shrinkage. Using Won’s equation, the influence of cooling rates in the mushy zone on SDAS was determined. The results indicated that a 72% lower difference in the area of negative macrosegregation zone (macrosegregation ratio (rseg) < -0.016%) for lower cooling rate (Ts = 1200°C). The difference of the area for positive segregation was 85% lower for higher cooling rates.
Analyte Tracking for Novel Bio-Applications
Authors: Gloes Franziska , Böhme Andrea , Liebscher Thilo , Zinn Steffen , Richetta Maria , Foitzik Andreas H.
Published: December 2018

Modern cell culture as well as sophisticated bio-applications involve complex biochemical processes, which are required to induce growth, product development or material degradation. Tracking the reaction processes inside the application presents a major challenge due to its complexity. The development of new analysis and tracking mechanisms for such application presents a solution to fully understand the process. In addition, the applied sensors are required to monitor the reactions enable a live tracking of the process. Furthermore, this gives the opportunity to influence and manipulate reactions to further enhance the application of the process. Possible analytes for tracking during processes can be chemical origin such as glucose, cytokines, antibiotics and growth factors, which are included in the culture medium. Based on the complexity of the culture or bio-application the sensor tracking mechanism has to be adapted to ensure full process control. A variety of different approaches can be used for the tracking mechanism.
Numerical Analysis of Temperature Rise during Dynamic Loading for Dissimilar Steel Joint Specimen
Authors: Takashima Yasuhito , Minami Fumiyoshi
Published: December 2018

In this study, dynamic temperature field in a dissimilar steel joint specimen was numerically analyzed by means of three-dimensional explicit finite element analysis. Fully coupled thermal stress analysis was performed by using FE-code Abaqus/Explicit ver. 6.12. It was assumed that 90% of the plastic work was transferred to heat. Furthermore, dynamic loading tests were conducted with three-point bending specimen extracted from the dissimilar steel joint between a mild steel and a high tensile strength class steel. The specimen included a U-shape notch in the bonded interface. A high-speed infrared camera was used to measure the temperature field near the bonded interface. The temperature field was recorded at a frame rate of 200 Hz during the dynamic loading test. The numerically calculated temperature field near bonded interface showed reasonable agreement with the temperature field measured by the high-speed infrared thermography. The temperature in the soft steel particularly increased during the dynamic loading. On the other hand, the increase in temperature in the hard steel area was relatively few.
Influence of Starting Microstructure on Dilatation Behavior during Tempering of a High Strength Steel
Authors: Talebi Seyyed Hesamodin , Ghasemi-Nanesa Hadi , Jahazi Mohammad , Melkonyan Haikouhi
Published: December 2018

The aim of this study was to determine the effect of non-isothermal tempering on microstructure evolution in large-size slabs. Using high-resolution dilatometry, three different cooling rates (from 0.08 to 3°C/s) representative of different regions from the surface to the core of the slab were experimentally simulated, and then tempering was carried out for each starting microstructure. A combination of light and electron microscopy and X-ray diffraction analyses were employed to accurately analyze different phenomena occurring during the tempering process, specially, the identification of different microstructures (bainite, martensite and retained austenite), and the determination of the percentage of retained austenite for each experimental condition were considered. Experimental results revealed that the microstructure after the cooling rate of 0.08°C/s consisted of bainite and some retained austenite. For the cooling rate of 0.3°C/s, martensite plus bainite was detected, and when the cooling rate was increased to 3°C/s, a martensitic microstructure was obtained. Analysis of dilatometry curves indicated that tempering behavior varied significantly with the starting microstructure. Martensite tempering was accompanied with a length decrease due to the decomposition of medium-carbon martensite to low-carbon martensite plus carbides. Tempering of bainite and retained austenite resulted in a remarkable length increase.
Isothermal Transformation, Microstructure and Mechanical Properties of Ausformed Low-Carbon Carbide-Free Bainitic Steel
Authors: Meng Jiang Ying , Zhao Lei Jie , Huang Fan , Zhang Fu Cheng , Qian Li He
Published: December 2018

In the present study, the effects of ausforming on the bainitic transformation, microstructure and mechanical properties of a low-carbon rich-silicon carbide-free bainitic steel have been investigated. Results show that prior ausforming shortens both the incubation period and finishing time of bainitic transformation during isothermal treatment at a temperature slightly above the Ms point. The thicknesses of bainitic ferrite laths are reduced appreciably by ausforming; however, ausforming increases the amount of large blocks of retained austenite/martenisite and decreases the volume fraction of retained austenite. And accordingly, ausforming gives rise to significant increases in both yield and tensile strengths, but causes noticeable decreases in ductility and impact toughness.
Physical Simulation Methods Applied to Hot Rolling of Linepipe Steels
Authors: Siciliano Fulvio , Allen Brian J. , Rodrigues Samuel F. , Jonas John Joseph
Published: December 2018

The simulation of industrial rolling processes has been shown to be an important method to optimize rolling parameters, reduce production costs and improve product quality. Previous works have shown the value of hot rolling simulation by means of torsion tests where the mean-flow-stress (MFS) can be successfully predicted. In the present work, three rolling schedules are simulated by hot torsion tests and compared. It is important to note this methodology provides the flexibility to test different ideas without the risk of downtime or damage to plant equipment that could result from an unsuccessful industrial trial. The simulation analysis considered the production steps from reheating through the final accelerated cooling as well as the final product microstructures. The study provides important information to the production of various steel grades such as pipeline, shipbuilding, structural and other high-end products.
Possibilities with Use of Electron Beam Welding of Very High Strength Steel
Authors: Hansson Per , Areskoug Magnus
Published: December 2018

Welding of very high strength quenched and tempered steel, Rp0.2 ≥ 900 MPa, put high demands on choice of welding process, consumables and also on the heat input. Such steels commonly have a quite narrow tolerance box for a suitable weld heat input to control the cooling time, Δt8/5, pertaining to minimize the risk for generating weld defects such as undercut, a too soft weld heat affected zone, delayed cracking etc. When welding very high strength steel is the risk for cold cracking in the weld metal not negligible due to the high alloy content of such high strength filler wires used. Furthermore, filler metal wires having equal strength levels to very high strength steel are hard to find which, together with the above described drawbacks, favour use of under-matching filler wires.