bluuebunny/crossref_metadata_2025 huggingface dataset:
The Disk Substructures at High Angular Resolution Project (DSHARP). IX. A High-definition Study of the HD 163296 Planet-forming Disk
Authors: Isella Andrea , Huang Jane , Andrews Sean M. , Dullemond Cornelis P. , Birnstiel Tilman , Zhang Shangjia , Zhu Zhaohuan , Guzmán Viviana V. , Pérez Laura M. , Bai Xue-Ning , Benisty Myriam , Carpenter John M. , Ricci Luca , Wilner David J.
Published: December 2018

The Atacama Large Millimeter/submillimeter Array observations of protoplanetary disks acquired by the Disk Substructure at High Angular Resolution Project resolve the dust and gas emission on angular scales as small as 3 astronomical units, offering an unprecedented detailed view of the environment where planets form. In this Letter, we present and discuss observations of the HD 163296 protoplanetary disk that imaged the 1.25 mm dust continuum and 12CO J = 2–1 rotational line emission at a spatial resolution of 4 and 10 au, respectively. The continuum observations resolve and allow us to characterize the previously discovered dust rings at radii of 68 and 100. They also reveal new small-scale structures, such as a dark gap at 10 au, a bright ring at 15 au, a dust crescent at a radius of 55 au, and several fainter azimuthal asymmetries. The observations of the CO and dust emission provide information about the vertical structure of the disk and allow us to directly constrain the dust extinction optical depth at the dust rings. Furthermore, the observed asymmetries in the dust continuum emission corroborate the hypothesis that the complex structure of the HD 163296 disk is the result of the gravitational interaction with yet-unseen planets.
Literatura, cuerpo y animalidad
Authors: Seligmann-Silva Márcio
Published: December 2018

En la primera parte de este texto, se exploran los orígenes del topos de la animalidad en nuestra cultura moderna; para ello se recuperan temas tratados desde la creación de la estética, y se arroja luz sobre el encuentro de la reflexión estética con la ciencia (en especial con Darwin y su teoría del origen de las especies). En la segunda, el autor asume la identidad de Rotpeter, el personaje de Kafka, y presenta el tratamiento de los animales en el escritor de Praga. En el epígrafe final se retoma el debate en torno a la cuestión animal y a la “naturaleza” en el contexto de una biopolítica de la compasión; aquí el autor apoya la discusión en dos obras de J. M. Coetzee, con el objetivo de mostrar hasta qué punto la compasión y la beneficencia pueden hallarse en el origen de una simple tutela autoritaria ejercida hacia el “otro”.
La forma en acto: morfogénesis y ciencias de lo viviente en Paul Valéry
Authors: Dahan-Gaida Laurence
Published: December 2018

En esta contribución se exploran las relaciones entre estética y biología en dos textos de Paul Valéry: La introducción al método de Leonardo da Vinci (1894) y El hombre y la concha (1937). En estos ensayos, Valéry desarrolla una teoría morfogenética que atribuye al arte la función de reapropiarse de las fuerzas formativas que obran en la naturaleza con el fin de producir a su vez la misma variedad de formas, y restaura de este modo el lazo entre estética y ciencias de lo viviente que Goethe había sido el primero en establecer. La morfogenética valeryana es esencialmente dinámica, pues otorga privilegio al devenir de la forma, al movimiento de la producción que desembocará en la forma acabada. Pero ni la física ni la biología de esa época disponían de principios explicativos capaces de dar cuenta a la vez de la espontaneidad y de la organización de los procesos morfogenéticos en la naturaleza. Como se tratará de mostrar, los obstáculos epistemólogicos detectados por Valéry le llevarán a esbozar una morfología dinámica que anticipa las teorías de la complejidad desarrolladas a partir de los años 80.
Más allá de la representación. ¿Es visible la realidad? (Imágenes y conocimiento)
Authors: Català Josep Maria
Published: December 2018

El trabajo de la ciencia con las imágenes nos muestra procedimientos que se alejan, por un lado, de los rigores del estricto método científico, y que crean, por el otro, innumerables paradojas, cuya intensidad se acrecienta a medida que aumenta la complejidad del objeto estudiado. A las operaciones simbólicas y retóricas configuradoras de las imágenes científicas, la mayoría de carácter tecnológico, se añaden los procesos de visualización que ponen en escena, en muy diversos niveles, las relaciones fundamentales de aquellas. Los nuevos estudios sobre la representación científica hablan de imágenes cargadas de teoría que se acercan a la eventualidad de una ciencia poética, cuyo camino habría sido abandonado a partir del siglo XVII, cuando la ciencia moderna provoca la separación epistémica entre lo real y la realidad.
Putting Africa on the Black Death map: Narratives from genetics and history
Authors: Green Monica H.
Published: December 2018

Did the Black Death, the famous, devastating plague pandemic that struck the Mediterranean and Western Europe in the mid-14th century and seeded new strains of the pathogen, Yersinia pestis, in new locales, also reach Sub-Saharan Africa? That it reached the Islamic North African littoral has never been in question: there is ample testimony from Arabic documentary sources for its devastating effects from Egypt to the Maghreb. But did it stop there? Archaeologists now have reason to believe that there was widespread abandonment of urban communities in West Africa in the 14th or 15th centuries. Focusing on the other side of the continent, the present essay argues that previously unutilized evidence—a “living archive” of genetic data combined with a new reading of linguistic and documentary evidence from the 14th through 20th centuries—suggests that plague did have a significant impact on pre-modern East Africa. The strains of Y. pestis currently found in East and Central Africa derive from one of the lineages involved in late medieval outbreaks in Central Eurasia. This post-Black Death strain, it is argued here, entered the continent most likely in the late 15th or early 16th century. This coincides with hitherto unexplained population migrations and other cultural signs of reactions to a deadly emerging disease. Although no aDNA (historical genetic material) for Y. pestis has yet been recovered from late medieval or early modern Africa, the present essay suggests that evidence for Y. pestis’s evolution and transcontinental movements, even those outside of Africa, can help archaeologists and historians draw Africa more centrally into the narratives of global history.
Nucleation and Growth of Oxide Particles on Fe-Mn (1 Wt.%) Binary Alloy during Annealing
Authors: Gong Li , Ruscassier Nathalie , Ayouz Mehdi , Giorgi Marie Laurence
Published: December 2018

The nucleation and growth of oxides formed on Fe-Mn (1 wt.%) binary alloy during annealing were investigated. The recrystallized samples were heated to 800°C and kept at this temperature for 60 s in N2 / H2 (5 vol.%) with a dew point of-40°C. The heating process was also interrupted at different temperatures, namely 650, 700, 750 and 800°C. The annealed samples were then observed by scanning electron microscopy. Image analysis was performed to obtain the surface density and size of the oxides. The influence of the ferrite grain orientation on the oxides’ nucleation and growth was studied by Electron Back Scattered Diffraction. The annealed Fe-Mn surfaces were covered by oxide crystals whose shape, surface density and size strongly depended on the underlying ferrite grain orientation. The oxides’ nucleation occurred first on Fe {110} grain, their surface density was the largest on Fe {100}, and their size was the largest on Fe {110}.
Influence of Precipitation on Twinning in a Mg-Al-Zn Alloy
Authors: Hidalgo-Manrique Paloma , Robson Joseph D.
Published: December 2018

A textured Mg-Al-Zn alloy rolled plate was solution treated and aged at 320 oC for 2 h and 116 h, respectively. Afterwards, the three conditions were compressed at room temperature along the transverse direction to activate {110} twinning. Ageing treatments were observed to strengthen the alloy in relation to the solution-treated condition. This has been mainly attributed to the restricted lateral growth of twins in the presence of particles and thus to the additional stress required for twin growth. Accordingly, a slightly reduced twin volume fraction, but an increased number of smaller twins was observed after compression in the aged samples.
Developing Superplasticity in High-Entropy Alloys Processed by Severe Plastic Deformation
Authors: Shahmir Hamed , Kawasaki Megumi , Langdon Terence G.
Published: December 2018

High-entropy alloys (HEAs) are currently attracting much interest because they offer unique properties and good ductility at low temperatures. These materials are of interest primarily because they contain five or more principal elements, with each element having a concentration between 5 and 35 at. %, and yet they have very simple structures based on solid solution phases. Superplasticity is defined formally as a tensile elongation without failure of at least 400% and very recent experiments have shown that the HEAs also have a potential for exhibiting superplastic ductilities when testing at elevated temperatures. Since superplasticity requires a very small grain size, typically <10 μm, it is feasible to process HEAs using severe plastic deformation in order to introduce significant grain refinement. The objective of this review is to summarize the recent results showing superplasticity in HEAs and to compare directly the superplastic flow in HEAs and superplasticity in conventional metallic alloys.
Strain Ratio Effect on the Low Cycle Fatigue Behavior and Microstructure of High-Mn Austenitic Alloy Undergoing the Strain-Induced ε-Martensitic Transformation
Authors: Nikulin Ilya , Sawaguchi Takahiro
Published: December 2018

The effect of the strain asymmetry on low-cycle fatigue properties and microstructure of Fe–15Mn–10Cr–8Ni–4Si (in. wt. %) alloy undergoing the strain-induced ε-martensitic transformation (ε-MT) were investigated at strain ratios, R, of-1, -0.2, 0.2 and 0.5 under total strain-control mode with total strain amplitude of 0.01. At studied strain ratios the clear asymmetry in tension and compression stress providing tensile mean stress was observed in alloy deformed at R of-0.2, 0.2 and 0.5. The mean stress rapidly decreases to ~ 100 cycles and remain almost zero until failure. It was found that strain-induced ε-martensitic transformation and lattice rotation of austenite provide cyclic hardening of the studied alloy leading to the mean stress relaxation and provides the stability in hysteresis loops behavior at studied R. As a consequence, the fatigue life, Nf, of the alloy remains on the level of the alloy deformed by LCF at R, of -1 (NfR=-1=9200 cycles). The details of the fatigue behavior, deformation mechanisms and microstructure evolution of the studied alloy are discussed.
Evaluation on Residual Stresses in Thick Titanium Welded Alloys
Authors: Zhao Hai Yan , Xie Pu
Published: December 2018

In this work, both Finite element simulated method and contour method experimental measurement are used to obtain residual stresses of different Titanium welded alloys, the results show that the maximum of the residual stress is mainly related to the internal restraint degree which formed inside of the thickness, the distribution of the residual stress depends primarily on the shape of weld shape. The heating stage plays a major role in relaxing the residual stress in this research. 95% of the residual stress is relieved in the temperature rising period, and about 75% of it is relieved in the temperature rising period when the temperature is above 500°C.
Yb: YAG Laser Welding of Aeronautical Alloys
Authors: Alexis Joel , Beguin Jean Denis , Cerra Pablo , Balcaen Yannick
Published: December 2018

Interest in the use of laser technology is growing in the aeronautical sector. The implementation of new Yb: YAG solid laser sources and new optical generations (dynamic focal length; 2in1 fiber: Fiber core and ring core) offers advantages in terms of quality, accuracy, reproducibility and weld dimensions. The LASER beam Yb: YAG of these new sources is generated, no longer from a bar of yttrium-aluminum garnet but from a disk. Moreover, a top-hat shaped power distribution and a top-hat shaped power distribution with a sharply limited recess in the center (ring structure) may be at the focal point using respectively the inner fiber and the coaxial fiber. These technological innovations offer new possibilities for cutting and welding of sheet metal parts. The welding domains of EN AW-6061 aluminum alloy, Commercial Purity Titanium - Grade 2 (T40), AISI 321 stainless steel alloy, nickel based Hastelloy X and Inconel 625 and cobalt based Haynes 188 superalloys are defined according to process parameters such as power density, focal diameter, welding speed and fiber type. Optimal welding parameters are determined for each alloy. The evolution of the microstructures and the mechanical properties of each zone of the welds are explained according to the power density, the heat input energy and the welding speed.
Relationship between Microstructure and Mechanical Strength of Dental Semiprecious Alloys Subjected to Solution Treatment
Authors: Akahori Toshikazu , Mizuno Tusbasa , Niinomi Mitsuo , Fukui Hisao
Published: December 2018

Silver alloy is one of semi-precious alloys for dental prosthesis, which has been applied remarkably in Japanese dental field. Ag-20Pd-17.7Cu-12Au alloy (G12), which was newly developed for commercial dental silver alloy, shows the unique hardening mechanism after a simple solution treatment (ST) at relatively high temperature. However, the relationship between ST at various temperature and the mechanical strength of G12 has not been investigated fully. Therefore, the relationship between ST and mechanical properties of G12 after ST at various temperatures was investigated systematically in this study. G12 subjected to ST at relatively high temperature of 1173 K is composed of three kinds of phases with Ag-rich α2 phase, Cu-rich α1 phase and β phase of Pd-Cu intermetallic compound. Although nominal melting point of G12 was around 1233 K, the high Cu concentration area like α1 phase was partially dissolved and then the α1, α2 and partial β phases re-precipitated during cooling. On the other hand, the microstructure of G12 aged at 673 K after ST at 1023 K (STA) was mainly composed of two kinds of phases with α2 and α1 phases with a small amount of β phase, which was a typical microstructure of STA. The Vickers hardness of G12 subjected to ST at 1173 K was identical to that of the same alloy subjected to STA although the tensile strength, fatigue limit and ductility deteriorated to some degrees. The corrosion potential of G12 changed drastically with the temperature of ST. The potential may have been increased by the decrease in the volume fraction of the α1 phase with relatively high Cu content.
Effect of Al Content on Microstructure and Properties of AlxMoNbTiV RCCA’s Alloys
Authors: Lacour-Gogny-Goubert Antoine , Zhao-Huvelin Zhao , Bachelier-Locq Agnès , Guillot Ivan , Denquin Anne
Published: December 2018

The objective of this study is the evaluation of high entropy alloys for aeroengines applications up to 1000°C. AlxNbMoTiV alloys with 10 and 20 at.% Al have been produced by arc melting. As-cast microstructure and phase transformations during heat treatments have been investigated through SEM, DRX and TEM, revealing the possibility of homogenization at 1400°C and the stability of the BCC structure at 1000°C and 800°C for both alloys. Mechanical properties have been evaluated through micro-hardness and compression tests up to 800°C. It appears that, although both alloys show a similar microstructure and hardness evolution with heat treatment, the Alloy containing 10 at.% of Al show a higher yield strength at room temperature and 800°C, related to the brittle character of the alloy containing 20 at.% of Al.
Microstructure and Crystallography of β Phase Formed through Electric Current Pulse (ECP) Treatment in Cold-Rolled Cu-40%Zn Alloy
Authors: Liu Mei Shuai , Zhang Yu Dong , Wang Xin Li , Beausir Benoit , Liu Mao Lin , Zhao Xiang , Zuo Liang , Esling Claude
Published: December 2018

Most of the studies on phase transformation in metallic materials have focused on transformations during cooling processes due to the easiness of the conservation of the product phase. However, for phase transformation happening during heating processes, the experimental investigations have been indirect if the product high temperature phase could not be preserved to the convenient observation temperature, for example the room temperature. The high density Electric Current Pulse (ECP) treatment allows the phase transformation during heating process and the preservation of the high temperature phase to the room temperature, offering possibilities for direct experimental examinations. Thus, in the present work, a cold-rolled Cu–40%Zn alloy was ECP treated and the microstructure of the product phase and the transformation orientation relationship were investigated. Results show that during the ECP treatment, the high temperature beta phase with BCC structure formed in the parent alpha phase with FCC structure. Especially, two kinds of orientation relationships could be detected between the parent alpha phase and the product beta precipitates. The one is the Kurdjumov-Sachs orientation relationship (K-S OR), and the other is the Nishiyama-Wasserman (N-W). In addition, the amount of beta precipitates obeying the K-S OR is more than that of precipitates obeying the N-W OR. The results of this work provide new fundamental information on phase transformation of metallic materials.
Measurement of Thermal Expansion Coefficient of MgZnY Alloys with Synchronized Long-Period Stacking Ordered Phase
Authors: Kimura Shigeru , Yasuda Nobuhiro
Published: December 2018

We measured the thermal expansion coefficients of 18R-LPSO phase and α-Mg phase in a Mg97Zn1Y2 alloy polycrystal. This was achieved by using a Gandolfi camera, which was attached on a high precision diffractometer at SPring-8 BL40XU beamline. By using this system, fine diffraction data were obtained from a Mg97Zn1Y2 polycrystal at 6 different temperatures between 90 and 450 K. We succeeded to determine cell parameters of 18R-LPSO phase and α-Mg phase separately in the Mg97Zn1Y2 alloy polycrystal. The thermal expansion coefficients were determined from the refined cell parameters. The differences of the thermal expansion coefficients of 18R-LPSO phase and α-Mg phase in the Mg97Zn1Y2 alloy were much smaller than those of single-phase 18R-LPSO and α-Mg polycrystals.
Characterization and Modelling of the Precipitation Sequence of an Al-Mg-Si Alloy with Silicon Excess for the Prediction of the Mechanical Properties during Ageing
Authors: Massardier Veronique , Meyruey Gwenaelle , Perez Michel
Published: December 2018

The precipitation sequence of an Al-Mg-Si alloy with silicon excess was determined between 150°C and 300°C by combining ThermoElectric Power measurements and Transmission Electron Microscopy observations. From these studies, an experimental Isothermal Transformation Curve could be proposed in the investigated temperature range. After calibration of a model of KWN type allowing the simultaneous precipitation of two types of metastable rod-shaped precipitates to be taken into account, the same type of curve could be obtained and the yield strength evolution of the alloy during isothermal ageing treatments could be predicted.
Effect of Aluminum Concentration on Damping Capacity during Annealing in AZ-Series Magnesium Alloy
Authors: Ahn Jae Hyeon , Kwak Ju Ho , Kang Chang Yong , Kim Kwon Hoo
Published: December 2018

In a previous study, the damping capacity gradually increased with increasing annealing time and temperature in AZ31. Also, at damping capacity test under similar conditions, AZ61 with a higher solute content showed a more rapid microstructure change than AZ31. In this study, it was investigated damping capacity on various aluminum concentration conditions in order to damping capacity that was influenced by microstructure and solute content. Three types such as pure Mg, AZ31 and AZ61 alloy of specimens were rolled at 673K with a rolling reduction of 30%, respectively. The annealing were conducted at various temperature and time. In this study, static recrystallization was occurred under all annealing conditions. The hardness gradually decreased until 60 minutes after the heat treatment. All annealing conditions, the damping capacity gradually increased with increasing annealing time and temperature. Especially, damping capacity and C1 value were increased with a decreasing of solute content.
Microstructure, Texture, Mechanical and Corrosion Performance of the Stainless Duplex Steel UNS S32205 Submitted to Warm Rolling
Authors: Santos Dagoberto Brandão , Assumpção Raphael França , Perasoli Daniela Barçante , Sicupira Dalila Chaves
Published: December 2018

The UNS S32205 duplex stainless steel was warm rolled at 600°C with 60 and 80% of thickness reduction. The microstructure was characterized by optical, scanning and transmission electron microscopy, X-ray diffractometry and EBSD. The corrosion resistance was evaluated by electrochemical behavior in the chlorine ion environment using potentiodynamic polarization measurements. The tensile strength reached 1185 MPa and 1328 MPa, after warm rolling with 60 and 80%, respectively. In steel as-supplied, hot rolled and annealed, the tensile strength was 774 MPa. Ferrite microtexture presented the α-fiber and the rotated cube component, while the austenite enhanced the brass, copper, and cube components to a lesser extent. The substructure was characterized by intense formation of tangles and forests of dislocations and discrete subgrains in the ferritic phase and by planar gliding of dislocations and formation of dense dislocations walls in the austenite. Despite the existence of a certain similarity among the values of pitting potentials obtained for all samples, the number of pits observed was higher in the as-received sample, followed by the samples with 60 and 80% reduction. These results draw attention to innovative routes in the industrial production of duplex stainless steel of this class, even considering ductility lost. Keywords: Warm rolling; Mechanical strength; Texture; Substructure; Corrosion resistance
Texture Formation Behaviour during High-Temperature Plane Strain Compression Deformation in AZ91 Magnesium Alloy
Authors: Han Dong Keun , Park Min Soo , Kwon Han Sang , Kim Kwon Hoo
Published: December 2018

In previous study, it was investigated texture formation behaviour of high-temperature plane strain compression test at 723K, under a strain rate of 5.0. It was found that the main texture component and it was sharpness vary depending on deformation conditions. To clarify the characteristic of texture formation behaviour, it is necessary to investigate at various deformation condition. Therefore, in this study, is investigating the influence or texture formation behaviour and strain, strain rate at 673K. Three kinds of specimens with different initial textures were machined out from a rolled plate having a <0001> texture. The plane strain compression tests were conducted at a temperature 673K, and a strain rate of 5.0, with strain between-0.4 to-1.0. After compression tests, the specimens were immediately quenched in oil. The texture evolution was conducted by the Schulz reflection method using Cu Kα radiation and EBSD. Before the deformation, {0001} of specimen A was accumulated in the center of pole figure. The {0001} of specimen B was accumulated at the RD direction. The {0001} of specimen C was accumulated TD direction. As a result, work softening is observed in all the cases at the true stress – true strain curve for three types of specimens. After deformation, the maximum pole density of increases with increasing strain. In this study, it was found that the stable orientation was (0001)<100> and (0001)<110> during deformation.
Superplastic-Like Elongation by Transition of Deformation Mechanism from Grain Boundary Sliding to Solute Drag Creep in Fine-Grained Al-Mg Solid Solution Alloy
Authors: Ito Tsutomu , Mizuguchi Takashi
Published: December 2018

It is widely accepted that the dominant deformation mechanism of fine-grained superplasticity is through grain boundary sliding (GBS) that occurs in fine-grained materials. However, it has been reported that in “Class I” solid solution alloys, superplastic-like behavior controlled by trans-granular deformation occurs by solute drag creep. In this study, we have investigated superplastic behavior in a fine-grained aluminum solid solution alloy with a thermally unstable microstructure. To obtain fine-grained microstructure, friction stir processing (FSP) was applied to a commercial 5083 aluminum (Al−Mg) alloy. An equiaxial fine-grained microstructure with a grain size of 7.4 μm was obtained after FSP; however, this microstructure was unstable at high temperatures. Generally, for fine-grained superplasticity or GBS to occur or continue, the fine-grained microstructure must be smaller than 10 μm during high-temperature deformation. However, a large elongation of over 200% was observed at high temperatures despite the occurrence of grain growth. From microstructural observations, it was determined that a fine-grained microstructure is maintained in the early stage of deformation, but at strain levels greater than 100%, trans-granular deformation occurs. The microstructural feature of this trans-granular deformation is similar to the deformation microstructure of solute drag creep observed in “Class I” solid solution alloys. This indicates that a change in the deformation mechanism from GBS to solute drag creep takes place during high-temperature deformation. Here, based on our observations on our model system, which is a thermally unstable aluminum solid solution alloy, we discuss the possibility of a superplastic elongation occurring by means of a transition of the deformation mechanism.
Spontaneous Microstructural Evolution and Magnetic Properties of Nano-Scale Particles Comprising Ferromagnetic Element Atoms in Cu-Ni-Fe and Cu-Ni-Co Alloys
Authors: Sakakura Hibiki , Matai Shintaro , Takeda Mahoto
Published: December 2018

Nano-scale granular magnetic material is a core component in next-generation recording devices. We investigated the influences of element species and composition of ferromagnetic atoms in copper-nickel base nanogranular magnetic materials. In this work, the authors focused on how microstructural evolution and magnetic properties are correlated in Cu-20at%Ni, Cu-15at%Ni-5at%Co and Cu-15at%Ni-5at%Fe alloys. We used Magneto-thermogravimetry (MTG), superconducting quantum interference device (SQUID) magnetometry and first-principles calculations based on the method of Koster-Korringa-Rostker (KKR) with the Coherent Potential Approximation (CPA) in order to investigate magnetic properties. Transmission electron microscope (TEM) observations revealed that ferromagnetic element atoms were precipitated with annealing at 973K, but microstructures were changed, depending on the combination and composition of the solute atoms. The magnetic property measurements and first-principles calculations have confirmed that magnetic precipitates are responsible for the magnetic properties of the Cu-Ni-Co and Cu-Ni-Fe alloys.
Phase Stability and Mechanical Properties of Metastable Ti-X-Sn-Zr (x=Cr, Nb or Fe) Alloys
Authors: Murayama Yonosuke , Shioiri Hiroto
Published: December 2018

Metastable beta Ti-Cr-Sn-Zr alloys used as biomaterial show low Young’s modulus and super-elasticity according to the phase stability of their beta phase. In this study, we substituted Nb and Fe for Cr in metastable beta Ti-2Cr-6Sn-45Zr alloy and investigated their effect. We investigated how the added amount of Cr, Nb and Fe influences the phase stability and the properties of low Young’s modulus and super-elasticity in Ti-x-Sn-Zr (x=Cr, Nb or Fe) alloys. The Young’s modulus of a Ti-x-Sn-Zr (x=Cr, Nb or Fe) alloy decreases with the addition of Cr, Nb or Fe. However, the Young’s modulus of a Ti-x-Sn-Zr (x=Cr, Nb or Fe) alloy increases with the addition of Cr, Nb or Fe after showing own minimum value respectively. Minimum Young’s modulus of several Ti-x-Sn-Zr (x=Cr, Nb or Fe) alloys were under 50GPa. The required amount of Cr, Nb or Fe in the Ti-x-Sn-Zr (x=Cr, Nb or Fe) alloy having minimum Young’s modulus is different according to the beta stabilizing ability of each element. Fe amounts were the smallest and Nb amounts were the largest. Ti-x-Sn-Zr (x=Cr, Nb or Fe) alloy with minimum Young’s modulus shows a stress-induced martensitic transformation. However, only Ti-Cr-Sn-Zr alloys showed definite super-elasticity. The recovered strain by super-elasticity is small in Ti-Nb-Sn-Zr alloy. Ti-Fe-Sn-Zr alloy didn’t show super-elasticity or large elongation.
Synthesis and Characterization of Nanostructured Mechanical Cu-Fe-Co Alloy
Authors: Biserova-Tahchieva Alisiya , López-Jiménez Isabel , Llorca-Isern Nuria
Published: December 2018

Nanocrystalline structure of CuFeCo (50:25:25 wt%) alloy has been obtained by high energy mechanical milling from elemental metal powder mixture during large hours of work. Phase transformations and diffusion in the system subjected to heat treatment are discussed. Thermal stability at high temperatures is analysed and considered of importance for several applications. The nanostructure was studied by employing X-Ray diffraction and electron microscopy. It has been determined the reduction in crystallite size and the induced microstrain by the milling time. The solid solution achievement through the increment of defect density was confirmed by Mössbauer analysis. Magnetic behaviour was analysed through magnetization technique entailing their soft ferromagnetic behaviour related to the microstructural changes.
Fabrication of the Beta-Titanium Alloy Rods from a Mixture of Pure Metallic Element Powders via Selected Laser Melting
Authors: Todai Mitsuharu , Nagase Takeshi , Hori Takao , Motoki Hiroyuki , Sun Shi Hai , Hagihara Koji , Nakano Takayoshi
Published: December 2018

The powder-bed additive manufacturing (AM) process offers advantages in terms of reduced material waste, ability to create complex shape and a decrease in the lead time from design to manufacturing. Recently, custom-made implant of Ti alloys is being developed by selective laser melting (SLM) in additive manufacturing (AM) process. However, the difficulty in the fabrication of titanium alloys due to their pre-alloyed powder cost, resulting in a limited usage of titanium alloys. To overcome this disadvantage, it is effective to fabricate the Ti alloys by SLM from mixture of pure elemental powders. In this case, it is avoided the preparing of the pre-alloyed powders. Therefore, the purpose of the present study is the trying to the fabrication of the Ti-20at.%X (X = Cr, Nb) alloys from the mixture of pure elemental powders by SLM.
From Pre-Alloyed Rod to Gas-Atomized Powder and SPS Sintered Samples: How the Microstructure of an Nb Silicide Based Alloy Evolves
Authors: Drawin Stefan , Malard Virgil , Denquin Anne , Monchoux Jean Philippe , Couret Alain
Published: December 2018

This work investigates the evolution of the microstructure of an Nb-23Ti-20Si (at.%) based alloy, from the primary plasma-melted material that is gas-atomized towards the consolidated material (here using SPS). The nature, morphology and size of the solid solution and the various silicides are followed by SEM, EDS and EBSD. Homogenous and fine microstructures are obtained after the SPS step and are improved by a subsequent heat treatment (1500°C, 100 h). However blocky silicides, already present in the powder particles, cannot be eliminated. A better control of the primary material’s microstructure would improve the microstructure of the final material.
Forming Behaviour at Elevated Temperature of a Laser Heat-Treated AZ31 Magnesium Alloy Sheet
Authors: Sorgente Donato , Palumbo Gianfranco , Fortunato Alessandro , Ascari Alessandro , Kaya Ali Arslan
Published: December 2018

The tailoring of mechanical and technological properties of the initial material in sheet metal forming has been widely investigated and successfully applied. The benefits of such an approach can be found in the improvement of both the post-forming performances of the manufactured component and the forming process capabilities. Different strategies can be found and most of them involve a microstructural alteration by a selective heat source (e.g. laser, induction, UV light). The use of aluminium alloys combined with these strategies has been extensively investigated, while magnesium alloys are almost not yet considered from this viewpoint. In this work, we investigated the effect of a selective laser heat treatment on an AZ31 magnesium alloy sheet. After laser heat treating a single track in the centre of a blank with different heat input values, bulge tests at elevated temperatures were conducted. The dome height evolution was continuously acquired during the tests and differences between the untreated specimen and the laser treated ones have been characterized. The effect of the laser treatment was evaluated also in terms of thickness distribution of the formed specimens. A thickness discontinuity was found along the treated specimens in the transition zone between the treated and the untreated material. Results highlighted that an effective change in the forming behaviour can be induced in the treated zone depending on the laser heat input. It has thus been shown that this approach can be employed for tailoring the magnesium alloy blank properties prior to the gas forming at elevated temperatures.
The Influence of Alloy Composition and Heat-Treatments on the Shape Memory Properties in a Cu-Sn-X Alloy
Authors: Kaneko Daisuke , Takeda Mahoto , Nakajima Takanari , Muramatsu Naokuni
Published: December 2018

We have focused on shape-memory properties of Cu-Sn based ternary alloys in this study. We have attempted to suppress degradation at room temperature aging and to improve the amount of shape recovery by adding the third element to a binary Cu-Sn alloy. The attempt has successfully conducted in Cu-Sn-Mn alloy, the degradation due to aging at room temperature was suppressed and the thermal stability was improved. Furthermore, the present study revealed that Cu-Sn-Mn alloy exhibited a large super elastic recovery in three point bending tests. We have also investigated the shape-memory properties of Cu-Sn-Si alloys and revealed that the ternary alloy has achieved super-elastic recovery better than the Cu-Sn-Mn alloy in the three-point bending tests.
Residual Stress Analysis of A362 Aluminum Alloy Gear Case Using Neutron Diffraction
Authors: Sediako Dimitry , Stroh Joshua , McDougall Alexandra , Aghaie Ermia
Published: December 2018

Mercury Marine has used a new alloy, Mercalloy A362, for the manufacturing of a re-designed lower unit transmission gearcase. The enhanced strength of the alloy allowed for a substantial weight reduction in the new design. The purpose of this study was to examine and determine why cracking may develop in the gear casing during in service testing. Two types of material states, (i) as cast and (ii) heat treated were compared. Metallography and neutron diffraction analysis was carried out at locations identified as being areas of high stress by Magma software – which was performed in a separate study. Microstructural characterization at these locations revealed microstructural and the compositional differences. Differences in the porosity, eutectic phase, and volume fraction of the precipitates were observed at various locations of interest in each material state. The residual stress analysis was performed with application of neutron diffraction and revealed that the stresses in the as-cast component reached a maximum value of 120 MPa, which is below the yield strength of the alloy. The heat treatment applied to the castings reduced the stress by approximately 50 MPa. Based on the microstructure and neutron diffraction results, it is likely that performing a heat treatment process extends the lifetime of the component, however, it may not completely eliminate the cracking problem. Farther studies are currently nearing completion, targeting the mass production of the redesigned gearcase.
Wide Scale Approach in Aluminium Alloys Microstructure Analyses from Component to Atom Scale in Order to Understand Behavior of New Alloys
Authors: Bassani Paola , Albu Mihaela , Gariboldi Elisabetta
Published: December 2018

Aluminium alloys are somehow the workhorse among light metals: spreading from castable, work hardenable to age-hardenable alloys, a wide panel of alternatives is available for the users. Nevertheless, continuous improvement of these alloys is ongoing, looking for higher strength, wider service temperature ranges, and suitability for new manufacturing processes.Likewise, a better knowledge of microstructure and ‘finer’ effects have to be encompassed.A proper multiscale approach and competent preparation are advisable for the best interpretation of the performances of new or ‘revised’ alloys.In this work a case study is presented in which multiscale approach has been used in order to explain the behavior of relatively widely used alloys, and also the problems and solution adopted in order to obtain the best results from microstructural analyses.Wrought age hardenable alloys were analyzed to have a better comprehension of ‘high temperature’ evolution of microstructure. The overall appearance of the microstructure was first identified by optical microscopy. Scanning Electron Microscopy (SEM) was involved to analyze grain size, type and size of secondary phases and texture. The results supported modeling studies related to the effect of grain size and texture. Finally, High Resolution Transmission Electron Microscopy (HR-TEM) investigations helped to understand the modification in the decay of mechanical properties upon extended overaging.
Study of Asymmetric Rolling to Improve Textures and r-Values of Aluminium Deep Drawing Alloys
Authors: van Houtte Paul , Shore Diarmuid , Van Bael Albert
Published: December 2018

The typical textures developed in aluminium alloys for deep drawing applications are less favourable as those in competing steel sheet material. The {111} fibre texture in steel, associated to high r-values, is favourable to this purpose, but the typical textures of the aluminium materials, the {001}<100> "cube" texture component and the β-fibre component, are not. Asymmetric rolling (ASR) as part of the production process generates a shear component at the expense of the unfavourable components. Modelling was tried out as a possible tool to fine-tune the process parameters. A multiscale FEM model (with a built-in polycrystal deformation model to predict the texture) was used to this purpose. The effect of the shear component on the resulting texture is discussed in function of the values of the process variables, as well as its effect on the resulting plastic anisotropy parameters (r and q values).
Recrystallization and Grain Growth Phenomena in Stainless Steels for Different Thermo-Mechanical Processes
Authors: Napoli Giuseppe , Grimozzi Stefano , Rocchi Claudia , Di Schino Andrea
Published: December 2018

The mechanical properties of steels are strictly connected to chemical composition as well as to microstructural features obtained after thermo-mechanical processing. As a consequence, recrystallization and grain growth are relevant to the mechanical properties of steels, thus suggesting the necessity of mathematical models able to predict the microstructural evolution after thermo-mechanical cycles. In particular, in stainless steel grades, mechanical characteristics, and a proper microstructure with an adequate grain size distribution, are very important in order to achieve the required formability and deep drawing properties for many applications. This paper deals with the study of microstructural changes, such as grain size variations and recrystallized volume fraction in stainless steels during isothermal treatments through the application of a mathematical model, able in general to describe the primary recrystallization and grain growth in metals. The developed model takes into account the recrystallization phenomenon and Zener drag effect. A general continuity equation is proposed describing in continuous way recrystallization and grain growth phenomena without taking into account textures effect. The influence of input parameters is analyzed.
Numerical Analysis of Horizontal Twin-Roll Casting for Mg-AZ31
Authors: Park Jong Jin
Published: December 2018

Molten Mg-AZ31 cools and solidifies to a sheet in horizontal twin-roll casting. In the present investigation, this process was numerically analyzed in two dimensions under various conditions. Steady-state solutions were obtained including plastic deformation after solidification. Based on results of the analyses, an optimum process schedule was proposed for production of a sheet of 1 mm in thickness where the sheet thickness decreased from 3 mm through a couple of transitions during operation. However, the schedule was recommended up to 2 mm in thickness due to the restriction in strength of the sleeve material.
Development of an Optimised Shielding Strategy for Laser Beam Welding of Ti6Al2Sn4Zr2Mo
Authors: Burkhardt Irmela , Ventzke Volker , Riekehr Stefan , Kashaev Nikolai , Enz Josephin
Published: December 2018

Ti6Al2Sn4Zr2Mo exhibits improved oxidation and creep properties compared to Ti6Al4V. Laser beam welding (LBW) is an approved process to receive narrow weld seams at high welding speeds with low heat input. Almost distortion free complex shaped structures can be joined with optimal parameters. For the optimisation of the LBW process the most relevant parameters are the welding speed, the laser input power and the gas shielding strategy. Using a fibre laser, the laser radiation is attenuated by a welding plume the so-called metal-vapour cloud (MVC). The MVC has a large influence on the laser input power. Therefore, an approach for reducing the MVC by optimising the shielding strategy using an additional gas flow in opposite welding direction is examined. Utilizing high-speed camera records, the effectiveness of the approach is assessed. Welded samples are evaluated by visual and radiographic inspection, metallographic assessment as well as microhardness measurements with regard to weld seam geometry, defects, microstructure and local mechanical properties. The obtained results are correlated to the used laser welding parameters.
Microstructure and Texture of MX20 after Conventional Rolling and Rolling from Twin Rolled Cast Strip
Authors: Kurz Gerrit , Petersen Tom , Hoppe Roland , Bohlen Jan , Letzig Dietmar
Published: December 2018

Two main impediments are currenty discussed with respect to the industrial application of magnesium sheets. First, the low formability of magnesium sheets requires many rolling passes to roll cast slabs to final gauge, which leads, second, to high costs for the production of magnesium sheets. An alternative cost-saving process chain for magnesium sheets with enhanced properties is the feedstock production by twin roll casting (TRC). In the TRC process, liquid metal proceeds from a furnace over a pipe into a crucible and then flows between a pair of counter rotating, internally cooled rolls. The metal solidifies upon touch with the cooled rolls and gets rolled to a strip. This paper refers to the comparison of the two processing routes on the example of the aluminum-free magnesium alloy MX20 (2 wt% Mn and 0.5 wt% Ca). Both kinds of production processes like casting and twin roll casting have an influence on the microstructure and texture of the feedstock material for the subsequent rolling process. The paper reports on the results of casting and twin roll casting experiments of this alloy. Furthermore, rolling trials are conducted and the deformation behavior of the sheets are presented and discussed with respect to the developed microstructures and textures. The different morphology of precipitates in the cast and twin roll cast feedstock material is used to improve the ductility of the magnesium alloy MX20.
Magnesium Twin-Roll Casting Technology for Flat and Long Products - State of the Art and Future
Authors: Kawalla Rudolf , Ullmann Madlen , Henseler Thorsten , Prahl Ulrich
Published: December 2018

Due to their advantageous strength-weight ratio, good recyclability, excellent noise and vibration damping properties as well as excellent dent resistance, magnesium materials offer a variety of uses in modern lightweight structures. As a result, a comeback of magnesium alloys is to be seen in multiple industrial applications, especially in the automotive industry, as the potential for lightweight, cost-effective lightweight industrial construction associated with the lightest metallic engineering material helps to meet even stricter energy and environmental efficiency guidelines. Traditionally, casting processes have been the dominant magnesium manufacturing processes, but in the last decade, an increasing number of lightweight structural applications have been implemented with magnesium wrought alloys. In this paper, the current state of developments focusing the twin-roll casting (TRC) of semi-finished products of magnesium alloys will be presented. By reducing the number of process steps in combination with a unique microstructure, the near-net-shape TRC process offers new options to provide magnesium materials meeting current and future requirements for semi-finished products, constructions and moldings in terms of type, quantity and quality.
Microstructure Characterization of AlSi10Mg Fabricated by Selective Laser Melting Process
Authors: Maeshima Takashi , Oh-Ishi Keiichiro , Kadoura Hiroaki , Hara Masashi
Published: December 2018

Multi-scale microstructure observation and three dimensional finite element thermal analysis of AlSi10Mg alloy fabricated by selective laser melting (SLM) process were demonstrated in order to understand the microstructure formation process during SLM fabrication. The unique hierarchically microstructures were observed: (1) the “fish scale” microstructure corresponding to a part of molten pool consists of columnar and equiaxed grains and (2) these grains contain a substructure of α-Al surrounded by Si particles. It is revealed that a supersaturated Si concentration due to the predicted rapid cooling rate on the order of 106 oC/s. In addition, the base temperature during the fabrication increases gradually with some peak temperature of each laser path as the laser scan has proceeded on a powder layer. Although the thermal changes cause no melting of the AlSi10Mg except directly fused region by selective laser so called molten pool, those are capable of causing precipitation and/or clustering.
Microstructure Evolution of Ti-5Al-5V-5Mo-3Cr after Hot Deformation at Large and Moderate Strains
Authors: Poletti Cecilia , Buzolin Ricardo H. , Kumar Sanjev , Wang Peng , Simonet-Fotso Thierry Franz Jules
Published: December 2018

This work deals with the analysis and modelling of the microstructural evolution of the metastable titanium alloy Ti-5Al-5V-5Mo-3Cr during hot deformation up to moderate and large strains. Experimental flow curves and deformed samples are obtained by hot compression and hot torsion tests using a Gleeble ® 3800 device. The samples are deformed above and below the beta transus temperature and in a wide range of strain rates. Microstructures are characterized after deformation and in-situ water quenching using light optical and scanning electron microscopy and electron back scattered diffraction (EBSD). Dynamic recovery of the beta phase is found to be the main deformation mechanism up to moderated strains. By increasing the strain, continuous dynamic recrystallization (cDRX) is confirmed by the progressive conversion of low angle boundaries into high-angle boundaries. Alpha phase plays a secondary role in the deformation of the material by pinning the movement of beta high angle grain boundaries (HAGB). The evolution of the microstructure is modelled using dislocation density as internal variable in the single β field.