bluuebunny/crossref_metadata_2025_split huggingface dataset:
SCaLAr – A surrounding spherical cap loudspeaker array for flexible generation and evaluation of virtual acoustic environments
Authors: Pausch Florian , Behler Gottfried , Fels Janina 
Published: October 2020

Introduction: Surrounding spherical loudspeaker arrays facilitate the application of various spatial audio reproduction methods and can be used for a broad range of acoustic measurements and perceptual evaluations.Methods: Installed in an anechoic chamber, the design and implementation of such an array of 68 coaxial loudspeakers, sampling a spherical cap with a radius of 1.35 m on an equal-area grid, is presented. A network-based audio backbone enables low-latency signal transmission with low-noise amplifiers providing a high signal-to-noise ratio. To address batch-to-batch variations, the loudspeaker transfer functions were equalised by individually designed 512-taps finite impulse response filters. Time delays and corresponding level adjustments further helped to minimise radial mounting imperfections.Results: The equalised loudspeaker transfer functions measured under ideal conditions and when mounted, their directivity patterns, and in-situ background noise levels satisfy key criteria towards applicability. Advantages and shortcomings of the selected decoders for panning-based techniques, as well as the influence of loudspeaker positioning errors, are analysed in terms of simulated performance metrics. An evaluation of the achievable channel separation allows deriving recommendations of feasible subset layouts for loudspeaker-based binaural reproduction.Conclusion: The combination of electroacoustic properties, simulated sound field synthesis performance and measured channel separation classifies the system as suitable for its target applications.
Advances and Breakthroughs in Titanium forgings for critical structural parts
Authors: Lecadet J. , Forestier R. , Delaborde P. 
Published: October 2020

Assuming the high level of properties and reliability of titanium forgings, strong drivers of research and development for forgings are the pressure on cost, the buy to fly ratio reduction and the life cycle. This presentation discusses the potential of optimizations to address these challenges. The first way to concretely answer the question of the cost and of the life cycle is the recycling of manufacturing scrap and end-of-life products, using the concept of circular economy and implementing a short loop from end user to melters. This is a considerable opportunity to mitigate the risks related to the supply of primary material and to the erratic fluctuations of raw material prices.The second step to optimize both the added value and the material consumption consists in adapting accurately the melting and ingot conversion processes to the actual needs of the application and the subsequent transformation processes.Considering the close die forging step, the use of the concept of Design for forging has also a great potential to optimize the cost and the functions of the forgings. Near Net Shape Forging of titanium, using high temperature close die forging is a great opportunity to make a breakthrough in terms of buy to fly ratio. In addition to all these improvements, the use of high-power hydraulic presses is a key element to take full advantage of them and to manufacture large critical parts with more functions.All together these levers could provide drastic cost reductions, and a considerable reduction in the environmental impact, keeping the advantages of titanium forgings in terms of metallurgical integrity, residual stresses and properties. The implementation of these improvements will require continuous efforts of development from the whole titanium supply chain, and collaboration between integrated titanium forgings suppliers and the OEMs.
Impact of process parameters and heat treatment on mechanical properties of Ti64 LBM
Authors: BERNARD Pierre 
Published: October 2020

Titanium is a very useful material for aerospace part manufacturing due to its mechanical properties and its lightness. Additive layer manufacturing (ALM), and amongst it Laser Beam Melting (LBM), is a new tool to manufacture parts that have a certain degree of complexity. It allows for the reducing of lead time, as well as reduces the development cycle. The aerospace industry is using more and more this tool to manufacture parts, either for development or for production.
With that in mind, Ti64 was developed in Vernon in order to manufacture parts for the Ariane propulsion engines. Certain parameters have been modified from the standard EOS set of parameters in order to gain in elongation at cryogenic temperatures. Also, a special work was performed in order to define the best heat treatment for Ariane’s applications. The main parameters adjusted were linked to the baseplate temperature during building, as well as the use of HIP. The gain was not only on elongation, but also on porosity rate and mechanical properties (tensile, fatigue) at cryogenic temperatures. Other parameters are being studied today in order to increase productivity.
SERIES PARTS MANUFACTURING BY INFRARED SUPERPLASTIC FORMING WITH NUMERICAL TECHNIQUES FOR THERMAL REGULATION
Authors: Elise LAMIC , Damien MAUDUIT , Fabien NAZARET , Rémi GILBLAS , Thomas POTTIER , Thierry CUTARD 
Published: October 2020

Materials used for Superplastic forming (SPF) are mainly titanium alloys which are good candidates to produce lightweight complex-shaped components for high performance aerospace applications. SPF process has limitations because it involves a high-temperature furnace with poor heat efficiency and expensive tooling with low management flexibility. Enhancing this manufacturing process is a major challenge for the aerospace industry which is facing to important production ramp-up and cost reductions. Direct heating combined with tool heat management result in significant savings of SPF process: production time savings by drastically reduce the heating time, reduction of maintenance costs and energy savings by significant heat efficiency improvement.
Aurock developed direct heating by Infrared emitters and succeed in forming series 1.5x1m² Ti6Al-4V blanks. A key point with this new technology is to ensure a homogeneous blank temperature all along the forming. This point is achieved thanks to lamp power modulations and numerical techniques to secure the blank thermal regulation with a full radiative flux control at different forming stages. Results obtained are stable and repeatable regarding to dimensional criteria, post-forming thicknesses distribution and microstructure. Numerical predictions are in very good agreement with the experimental results, enabling robust machine setup for series Infrared SPF parts production.
Numerical simulation of Rapid Additive Forging (RAF) process
Authors: Depradeux Lionel , Robitaille Corentin , Duval Gilles , Eckenfelder Luc , Locatelli Camille 
Published: October 2020

The Rapid Additive Forging (RAF) process is a Direct Energy Deposition (DED) Additive Manufacturing (AM) process, based on the deposition of a Titanium alloy on a substrate plate. This process has been developed for the production of Titanium parts of aeronautic components. In this study, a Finite Element (FE) numerical simulation methodology has been established to perform a fast analysis of the RAF process, including full 3D-transient thermal-metallurgical and mechanical numerical simulations. Thus, residual stresses and distortions caused by the process can be estimated. Different modelling strategies have been compared in order to find a balance between computation time and accuracy. Analyses include the effects of phase transformations in the Titanium alloy. First analyses have been performed on a simple geometry of welding wall. The influences of the material activation modelling strategy on the thermal and mechanical results have been investigated. The effects of phase transformations on residual stresses and distortions are also discussed.
Then a specimen with a more complex geometry has been considered in the analysis, including the effect of different deposition paths. A full 3D simulation of the whole deposition process has been compared with several simplified computation procedures, including a reduction of the number of layers considered in the simulation.
Effect of silicon on creep properties of titanium 6Al-2Sn-4Zr-2Mo alloy
Authors: Anti M-L , Collado Ciprés V , Mouzon J , Åkerfeldt P. , Pederson R 
Published: October 2020

The alloy Ti-6Al-2Sn-4Zr-2Mo is a titanium alloy for elevated temperatures often used in aerospace applications. Minor additions of silicon have proven to improve the creep resistance of this alloy. In this work, three different amounts of silicon (0.015, 0.07 and 0.162 wt% Si) were added to cast Ti-6242 and creep tests were performed at different temperatures and loads. Creep resistance increased significantly with silicon addition by means of silicide precipitation hindering dislocations movement. Silicon rich nanoparticles in the microstructure were detected and their effect on creep resistance was investigated. The instruments used in this study were light optical microscope (LOM) and scanning electron microscopy (SEM).
Precipitates larger than 150 nm were found to be located heterogeneously in the microstructure, whereas smaller precipitates, ranging from 20-100 nm were homogeneously spread in the material. All silicides were predominantly situated next to the beta-phase in the alloy, either at the prior-beta grain boundaries or the beta-phase in between the alpha-colonies.
Second-generation Titanium alloys Ti-15Mo and Ti-13Nb-13Zr: A Comparison of the Mechanical Properties for Implant Applications
Authors: Brunke Florian , Siemers Carsten , Rösler Joachim 
Published: October 2020

Due to their outstanding mechanical properties, excellent corrosion resistance and biocompatibility titanium and titanium alloys are the first choice for medical engineering products. Alloys currently used for implant applications are Ti-6Al-4V (ELI) and Ti-6Al-7Nb. Both alloys belong to the class of (α+β)-alloys and contain aluminium as an alloying element. Aluminium is cytotoxic and can cause breast cancer. In addition, the stiffness of (α+β)-alloys is relatively high which can lead to stress shielding, bone degradation and implant loss. For this reason, second-generation titanium alloys like Ti-15Mo (solute-lean metastable β-alloy) and Ti-13Nb-13Zr (β-rich (α+β)-alloy) have been developed. However, their application in medical implants is limited due to a relatively low strength.Therefore, in the present study, the mechanical properties of Ti-15Mo and Ti-13Nb-13Zr have been optimised by thermomechanical treatments to achieve high strengths combined with low stiffnesses. Different phase compositions have been used, namely, α-, β- and ω-phase in Ti-15Mo and α-, β- and αʺ-phase in Ti-13Nb-13Zr. For Ti-15Mo, the required mechanical properties’ combination could not be achieved whereas Ti-13Nb-13Zr showed high strength and a low Young’s modulus after a dedicated thermo-mechanical treatment. This makes the latter alloy a good option for replacing the (α+β)-alloys in implant applications in the future.
Atomization of Ti-64 alloy using the EIGA process: comparison of the characteristics of powders produced in labscale and industrial-scale facilities
Authors: Drawin Stefan , Deborde Agathe , Thomas Marc , Pierronnet Michel , Sasaki Layla , Delfosse Jérôme , Godde Olivier 
Published: October 2020

Titanium alloy powders, mostly the Ti-64 alloy with composition Ti-6Al-4V (wt.%), are extensively used for biomedical and high-demanding applications, e.g. in aeronautics. Advanced powder metallurgy processes like additive manufacturing are strong drivers for the production of high quality powders, insuring a good rheological behavior, a low porosity level in the parts and an adequate roughness. Ideally, fine spherical particles with no volume and surface defects are aimed at.
Inert gas atomization is a process that is able to produce clean powders for such applications, especially for AM. To avoid the chemical reaction of titanium with the commonly used alumina crucibles, a crucible-free configuration has been designed in the EIGA process (Electrode induction melting Inert Gas Atomization). Two EIGA facilities are currently available in France for R&D purposes: a one-liter (nominal rod diameter/length (mm): 50/500) labscale facility at ONERA and an eight-liter capacity (100/1000) industrial-scale facility at the MetaFensch Institute. Using the smaller facility to screen and optimize atomization parameters and transfer them to the bigger facility is a tempting approach. This communication will show the characteristics of Ti-64 powders produced in both facilities, in terms of particle shape, particle size distribution, presence of satellites and porous particles.
Forecast of the fatigue crack initiation site of commercially pure Titanium miniature specimens with local surface topography data
Authors: Böhme L. , Ströer F. , Keksel A. , Seewig J. , Kerscher E. 
Published: October 2020

Surfaces of technical components rarely appear in perfectly smooth condition. During fatigue loading, stress concentrations at surface asperities cause localized plastic deformation that can lead to crack initiation. Therefore, we have established a computer-aided method based on material ratio curves to investigate the possibility to predict the crack initiation site in fatigue tests by using detailed information on the local surface topography.The present study shows the results of investigations on the mutual influence of the average grain size and the surface condition on the fatigue behavior of commercially pure Titanium (cp-Ti) miniature specimens. Three cp-Ti states were investigated: two types of coarse-grained cp-Ti Grade 2 with 35 µm and with 100 µm average grain size and one ultrafine-grained cp-Ti Grade 4 state with less than 2.5 µm average grain size. Confocal microscopy provided the surface topography data of all specimens and data post-processing was applied to the topography in order to locate critical areas where crack initiation may preferentially occur. These areas were compared with the actual crack initiation areas in fatigue test. Finally, scanning electron microscopy (SEM) images of the fracture surfaces were studied to analyze fatigue crack initiation site and crack path of the three microstructural states.
Mechanical properties and deformation mechanisms in microscale Ti-55531 alloy
Authors: Kou Wenjuan , Sun Qiaoyan , Xiao Lin , Sun Jun 
Published: October 2020

The mechanical behaviors and deformation mechanisms of solution treated and 450°C aged Ti-55531 alloy microsamples are investigated by the micro-compression and micro-bending. The results show that the dislocation slip is a concentrated movement in the solution treated microsamples which containing nanoscale ω phase. Under the tensile and compressive stress, there were serious strain bursts occurred in the plastic deformation of solution treated microsamples. But the dislocation slip is transmit at the phase interface in the 450°C aged microsamples which containing high density of α phase. The deformation behavior exhibits high strength and excellent stability in the micro-compression and micro-bending process. The different mechanical behaviors and deformation mechanisms of Ti-55531 alloy containing different second phase have significant guidance for tailoring the microstructure and mechanical properties.
Key words: Titanium, Micro-compression, Micro-bending, Dislocation, Mechanical behavior
Study on Microstructure and Mechanical Properties of Low Cost Ti-Fe-B Alloy
Authors: Sun Yangyang , Chang Hui , Fang Zhigang , Dong Yuecheng , Dan Zhenhua , Guo Yanhua , Zhou Lian 
Published: October 2020

Microstructure evolution and mechanical properties of low cost Ti-2Fe-0.1B alloy under different heat treatment were studied. Results indicated that two kinds of equiaxed microstructures with different characteristics were obtained in conventional and double annealing, and typical lamellar microstructure was obtained in β annealing. Tensile test results shown that as-received rolled alloy possess highest strength and plasticity simultaneously due to fine and entangled microstructure. Uniform equiaxed dimples were observed in microstructure, which revealed ductile fracture morphology.
Key words: titanium alloy; microstructure; heat treatment; mechanical properties
Alloy Development and Optimisation Informed by an Understanding of Cold Dwell Fatigue Sensitivity
Authors: Bache M.R. , Thomas M. 
Published: October 2020

Near α titanium alloys have demonstrated a sensitivity to fatigue loading when incorporating a dwell period at peak applied stress under room temperature. Historically, this was first reported for the relatively coarse grained variant IMI685 and later exemplified when characterising TIMETAL® 834 (Ti-834). Various mechanical factors have been identified as key drivers for the phenomenon, including time on load and high R ratios. This indicates that sub-critical damage is accumulated via creep style mechanisms and has led to analogies with “cold creep” behaviour. The propensity of quasi-cleavage faceting at the initiation sites of fatigue cracks formed under dwell conditions eventually led to an understanding of stress redistribution between strong and weak grains. This mechanism can be accentuated by more extensive regions of common crystallographic grain orientation in the form of “macrozones”. Through this fundamental understanding, new alloys can now be developed with the intent to circumvent dwell sensitivity.
The present paper will focus on the fatigue performance of TIMETAL® 575 (Ti-575), a recently developed alloy optimised for aero-engine applications. Ti-575 was designed for improved strength and fatigue performance. The alloy’s susceptibility to dwell fatigue has been avoided through control of the microstructural evolution kinetics and associated thermo-mechanical process route to induce fine scaled, bi-modal microstructure containing equiaxed primary grains and secondary α laths with inherent random grain orientations, thus minimising the formation of macrozones. This work will detail the dwell fatigue testing, interpretation of data and associated microstructural characterisation, including EBSD, and compare this analysis with similar results from more conventional alloys such as Ti-6Al-4V and Ti-834.
Study of harmonic microstructure development during Spark Plasma Sintering (SPS) of β-CEZ titanium alloy
Authors: Denand Benoît , Sharma Bhupendra , Geandier Guillaume , Dirras Guy , Ameyama Kei , Zhang Yudong , Aeby-Gautier Elisabeth 
Published: October 2020

The present study focuses on the formation of harmonic microstructures in a metastable β titanium alloy, the β-Cez alloy (Tβ =890°C). Previous studies showed that harmonic structures obtained by a powder metallurgy route led to an increase in mechanical properties. In this study, the harmonic structure was obtained after a Mechanical Milling of the Initial Powder followed by Spark Plasma Sintering.
The phase transformations occurring in the Initial Powder and Mechanical Milled powders during a heat treatment similar to the SPS one were studied. Electrical resistivity, high energy XRD and SEM-EBSD were used to characterize the evolution of phases and microstructures and highlight the effect of the thermal treatment and the milling. It was shown that after thermal treatment of Mechanical Milled powders, a harmonic α + β microstructure is obtained consisting of nodular α grains in the powder shell and α lamellae in the powder core. The stress/strain induced martensite formed during the milling associated with the heavier deformation at the powder surface areas contributes highly to the formation of network arrangement of nodular α grains by a recovery/recrystallization phenomenon of β and α phases during the heating.
Thermomechanical process route to achieve high fracture toughness in Ti-17 forgings for high temperature applications
Authors: Balzer Mario , Witulski Thomas 
Published: October 2020

Mechanical properties of Ti-17 are typically strongly influenced by different thermomechanical process parameters such as applied strain, cooling rates and heat treatment temperatures and times. A variation of theses parameters allows the optimization of material properties. Today Ti-17 is mainly used for aero engine applications, where a high strength and good low cycle fatigue properties are needed up to 450°C. For structural parts damage tolerance properties are the main focus and therefore fracture toughness and fatigue crack propagation are the main driving factors for the design.
In large forgings such as aero structural parts, the tempering cross section generally varies significantly, which makes it extremely challenging to achieve uniform properties in each area of the forging especially in case of low buy-to-fly ratio. The aim of this work is to develop a robust thermomechanical processing route for large Ti-17 die forgings with complex geometry and high fracture toughness requirements.
Hand forging trials with four different thermomechanical processing routes resulting in a lamellar microstructure have been performed and their strength and fracture toughness properties were studied. In addition, one die forging using a promising process route was manufactured and strength and fracture toughness were compared with values typically achieved for Ti6-4.
Microstructure-Property Relationships in Cold Rollable, High-Strength α/β Alloys
Authors: Foltz John W. 
Published: October 2020

For decades Ti-6Al-4V has been the workhorse alloy for aerospace sheet applications due to its good balance of properties and the known ability to hot roll it with relative ease. Sheet of Ti-6Al-4V is made by hot pack rolling, which is a costly and time consuming process, due to the alloy having insufficient room-temperature workability to support significant cold reduction or forming. Consequentially, Ti-6Al-4V is not typically offered in foil gauges, since the direct product of hot pack rolling contains an undesirable surface finish and insufficient gauge control. Hot pack rolling also limits the maximum sheet size and annual capacity.
As a world leader in advanced sheet alloys of titanium, nickel, cobalt, and specialty stainless steels, ATI is developing new titanium alloys with improved strength compared to Ti-6Al-4V that take advantage of a recent understanding of cold workability in high-strength alpha-beta titanium. These α+β alloys exceed Ti-6Al-4V strength while being highly cold formable. Cold rolling via coil processing also enables longer lengths of sheet with significantly improved gauge control and surface finish.
Results from pilot scale ingots will be presented upon, including final properties of these unique alloys and microstructure-property correlations developed through modelling.