bluuebunny/crossref_metadata_2025 huggingface dataset:
PRELIMINARY INVESTIGATION OF BILLET PROCESSING ROUTE ON MICROSTRUCTURE, TEXTURE AND FATIGUE RESPONSE OF Ti834 FORGED DISC PRODUCTS
Authors: Fernandez-Silva B. , Wynne B. P. , Jackson M. , Bodie M. , Fox K.
Published: October 2020

Non-standard processing routes for the manufacture of industrial scale Ti834 billet have been undertaken to investigate their effect on macrozones in final forged product. Microstructure, texture and dwell fatigue fracture surfaces were characterised from forged disc samples fabricated from these new billets. All processing routes showed a bimodal microstructure consisting of 25pct of primary alpha grains in a transformed beta matrix. Texture analysis has revealed variations in the presence and size of macrozones with relatively weak textures. Quasi-cleavage facets were present in all dwell fatigue samples although the fatigue life was doubled for the sample whose thermomechanical processing has the highest imposed strain.
Study on impact properties of Ti6211 titanium alloy at different temperatures
Authors: Tian Yanwen , Hao Fang , Xu Enen , Du Junqi
Published: October 2020

In this paper, Charpy notched pendulum test was used to study the impact properties of Ti6211 titanium alloy at -60 ℃, -40 ℃, -20 ℃, 23 ℃, 100 ℃, 200 ℃ and 300 ℃, respectively, and the fracture morphology was analyzed. The ductile and brittle transition temperature of the material was deduced from the area of the radiation zone. The results show that with the increase of temperature, the impact energy of the alloy increases continuously, and when the temperature reaches above 0 ℃, the impact energy increases obviously, and the area of the radiative area of the fracture surface increases gradually. Which can be inferred that the ductile and brittle transition temperature of the alloy is about 50 ℃.
TEM observation of precipitates and their role to mechanical properties in Ti-5553 alloy heated to some temperatures up to 923 K
Authors: Sukedai E. , Aeby-Gautier E. , Dehmas M.
Published: October 2020

A Ti-5553 specimen was continuously heated to 923 K and simultaneously in-situ HEXRD profiles were taken. In addition, specimens heated at the same rate to several temperatures up to 923 K and further quenched were observed by transmission electron microscopy. Based on both results obtained, transformation sequence was clarified, precipitations of ω-, α”iso- and α-phases were confirmed, and size and density of these precipitates were measured. Hardness values of those specimens were also measured. The hardening mechanism was considered as shearing-mechanism for specimens aged at lower temperatures and by-pass one for specimens aged at higher temperature. An attempt of distinction between α”iso - and α-precipitates was also tried. Both precipitates were in needle-like shape and a possibility was suggested by measuring angles between two needle-shape precipitates on {110} of the matrix and comparing with each other.
Electron Beam Cold Hearth Melted Titanium Alloys and the Possibility of Their Use as Anti-Ballistic Materials
Authors: Markovsky P.E. , Bondarchuk V.I. , Akhonin S.V. , Berezos A.V.
Published: October 2020

Three commercial titanium alloys: two-phase α+β Ti-6Al-4V (low alloyed), and T110 (Ti-5.5Al-1.5V-1.5Mo-4Nb-0.5Fe, higher-alloyed), and β-metastable Ti-1.5Al-6.8Mo-4.5Fe were melted using EBCHM approach in the form of 100 mm in diameter ingots with the weight of about 20 kg each. After 3D hot pressing at single β-field temperatures ingots were rolled at temperatures below β-transus onto plates with thickness varying from 3 mm to 25 mm. Different heat treatments, including annealing at α+β or β-field temperatures, and special strengthening Surface Rapid Heat Treatment (SRHT) which after final aging provided special gradient microstructure with a hardened surface layer over ductile basic core, were employed. Mechanical properties were studied with tensile and 3-point flexure tests. It was established that the best combination of tensile strength and ductility in all alloys studied was obtained after SRHT, whereas at 3-point flexure better characteristics were obtained for the materials annealed at temperatures of (α+β)-field. At the same time, ballistic tests made at a certified laboratory with different kinds of ammunition showed essential superiority of plates having upper layers strengthened with SRHT. The effect of microstructure of the alloys, plate thickness and type of used ammunition on ballistic resistance is discussed.
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.
Deformation mechanisms and effect of oxygen addition on mechanical properties of Ti-7.5Mo alloy with α” martensite
Authors: Ji Xin , Gutierrez-Urrutia Ivan , Emura Satoshi , Tsuchiya Koichi
Published: October 2020

Effect of oxygen content as an important interstitial solute on the microstructure and mechanical properties of Ti-7.5Mo alloy was investigated. With increasing the oxygen content, the yielding strength, ultimate tensile strength and Young’s modulus of Ti-7.5Mo-xO (x=0, 0.2, 0.3, 0.4, 0.5) alloys increased, while the elongation showing a decreasing tendency. Solid-solution strengthening by the oxygen atoms has been addressed as the main strengthening mechanism. Ti-7.5Mo-xO (x ≤ 0.3) alloys have been regarded with an excellent combination of high yield strength (~640 MPa) and elongation (~28%), as well as low Young’s modulus (~60 GPa). The deformation microstructure of orthorhombic-α” martensite in Ti-7.5Mo alloy was also investigated by tracking a change in the microstructure of a selected area upon tensile deformation. Deformation twins induced by 5% tensile straining was identified as {112}α”-type I twins, which had not been reported before in α”martensite in β-Ti alloys.
Microstructural evolution and Mechanical Properties of a Newly Developed Ti2AlNb-based alloy
Authors: HE Yongsheng , LUO Wenzhong , DU Yujun , WU Ming , Wang Kaixuan , LIU Xianghong , HU Rui
Published: October 2020

The effects of the microstructure on the tensile and creep properties of the alloy at room temperature and high temperature were investigated by controlling the microstructures of the alloy by different hot working processes. It is found that the lath microstructure obtained by forging in B2 single phase zone has high tensile strength. The tensile strength is 1188 MPa at room temperature and 950 MPa at high temperature. The equiaxed structure obtained by forging in O+B2 phase region has the characteristics of high plasticity, creep resistance and low tensile strength. The elongation at room temperature is 9.0%, and the elongation at high temperature is 36%. The ambient temperature, high temperature tensile properties of the dual microstructure obtained by forging in the three-phase zone of α2+O+B2 are between the lath and the equiaxed microstructure.
Coexistence of multi-deformation modes in beta Ti alloys with improved yielding strength and ductility
Authors: Chen Guanfang , Zhang Jinyong , Fu Yangyang , Chen Zheng , Sun Fan , Li Ju
Published: October 2020

By suppressing SIM (stress induced martensitic) phase transformations, a strong and ductile beta TWIP (twinning induced plasticity) Ti-Mo based alloy was achieved, thanking to the coexistence of mechanical twinning ({112}<111> mode and {332} <113> mode) and dislocation glide. The alloy displayed extra high yielding stress, stable strain-hardening rate and adequate ductility. In-situ traction/EBSD technique and TEM characterizations were employed to investigate the plastic deformation mechanism. The dislocation slipping was mediated by bimodal twinning mechanism, composed by high density nano-scale {112} twinning in micro {332} twinning grid. The study aims to exploit novel design strategy for strengthening ductile TWIP Ti alloys, attributed to multimodal twinning effects.
Dislocation interactions in near-alpha Titanium alloy Ti6242Si under LCF
Authors: Joseph Sudha , Lindley Trevor C. , Dye David
Published: October 2020

Dislocation interactions were investigated in near-alpha titanium alloy Ti6242Si after low cycle fatigue. Samples from the gauge section and the crack initiation site on the fracture surface were studied. Grain pairs with different crystallographic orientations were analysed from the gauge section to understand the dislocation interactions near the boundary. Deformation was primarily caused by planar slip, localized into slip bands in primary alpha (αp) grains. Direct slip transfer was observed within grains having similar orientations. In contrast, slip transfer resulted in a different kind of dislocation nucleation in the neighboring hard grain where there was misorientation between the grains, with the observation of cross-slip. Strain transfer was observed between highly misoriented grain pairs. Crack nucleation occurred on an αp grain by basal plane splitting, due to the large tensile stress developed by a double ended pile-up. This kind of pile-up is suggested to result from the incomplete reversibility of dislocation motion during load reversals. The observation of superjogs on the basal dislocations in the crack nucleated αp grain provides a rationale for why cracks nucleate near, rather than on, the basal plane.
Multi-strengthening-mechanisms in a novel titanium alloy with (TiHf)5Si3 particle-reinforcement
Authors: Du Yan , Lu Jinwen , Zhang Wei , Zhang Yusheng
Published: October 2020

The microstructure and mechanical properties of Ti-2Si-2Nb-2Fe-1Hf-1Ta-1W alloy with (TiHf)5Si3 particle-reinforcement and their underlying relations have been studied. Electron microscope observations and correlative statistical analysis have been made to analyze microstructure evolution with heat treatments. The (TiHf)5Si3 particles with 800 nm in diameter were found uniformly distributed at α/β boundaries and triple junctions and turned out to be stable even after heat treatments at high temperature for a long period, inhibiting grain growth and dislocation motion. In addition, multi-strengthening-mechanisms including particle strengthening, solid-solution strengthening, grain boundary strengthening and dislocation strengthening have been discussed.
Optimization of shot peening for titanium alloys Ti 10-2-3 in CONDOR project
Authors: DIDES Corentin , BILLOT Thomas , GUILLEMOT Nicolas
Published: October 2020

CONDOR is an R&D project lead by IRT-M2P with different industrial partnership to increase knowledge and simulation models of shot peening. This surface hardening process aims to perform different shots with high velocity on metallic surfaces to introduce compressive stresses on it. Fatigue behavior of shot peened parts is significantly improved. During this research project a DOE has been carried out to optimize shot peening parameters on titanium alloys (surface roughness before shot peening, size and shot’s hardness, covering and intensity). The DoE is composed by more than 300 fatigue specimens. All this data allows us to define specifically each shot peening parameter influence on shot penned parts efficiency. CONDOR project allows simulation development of models to simulate shot peening effect by taking into account the parameters introduced above. Those models are used to evaluate residual stress level and fatigue lifetime after shot peening and to confirm models readiness level. This study has defined optimized machining and shot peening conditions in order to increase parts fatigue lifetime.
Deformation behaviour of beta phase with similar chemical composition in beta and alpha+beta titanium alloys
Authors: Xu Xin , Bantounas Ioannis , Dye David
Published: October 2020

Twinning-induced plasticity (TWIP) and transformation-induced plasticity (TRIP) in β titanium alloys have been attracting significant interest, since they offer the possibility to provide work hardening and thus, ductility. Here a quaternary Ti-Al-Cr-Mo metastable β alloy has been designed with an excellent combination of strength ductility that exploits the TWIP and TRIP effects. Its engineering yield strength, tensile strength and total elongation are 737 MPa, 999 MPa and 24%, respectively. In order to increase the yield strength but retain ductility, an attempt has been carried to design an α+β alloy with a bimodal microstructure. The composition of the β phase in the α+β alloy was tuned to provide deformation twinning of the β phase. The content of the major α and β stabilising elements, i.e. Al, Cr and Mo, in the β phase of the α+β alloy was similar to the β alloy, but the deformation twinning was not observed in the β phase. It is suggested that this may be due to over-stabilisation of the β phase and/or to the different stress/strain and dislocation distributions in the α+β alloy caused by the presence of β phase.
Data Driven Tools and Methods for Microtexture Classification and Dwell Fatigue Life Prediction in Dual Phase Titanium Alloys
Authors: Venkatesh V. , Noraas R. , Pilchak A. , Tamirisa S. , Calvert K. , Salem A. , Broderick T. , Glavicic M.G. , Dempster I. , Saraf V.
Published: October 2020

Microtexture has been linked to large reductions in cold dwell fatigue (CDF) life of specific dual phase titanium alloy aeroengine components. A recently completed Metals Affordability Initiative (MAI) funded program led by Pratt & Whitney (P&W) and includes ATI Forged Products, Boeing, GE Aviation, Rolls Royce (RR), Arconic, Titanium Metals Corporation (TIMET), PCC-Wyman Gordon (PCC-WG), Scientific Forming Technologies (SFTC), Materials Resources LLC (MRL) and The Ohio State University (OSU) has developed improved techniques for the characterization of microtexured regions (MTR) in titanium billet and forgings, and integrated computational materials engineering (ICME). These methods are aimed at developing and integrating process and property modeling tools for the prediction of microtexture and fatigue life in titanium components. These characterization and fatigue life prediction tools have near-term application off ramps that will enable use for process and product development and quality control. Key results for two widely used alloys, Ti-6242 and Ti-64, will be reviewed in this paper.
GAS NITRIDING INFLUENCE ON FATIGUE AND CREEP BEHAVIORS IN TITANIUM GRADE 2
Authors: KMS Palma, , GB Perina , VMO Velloso , CARP Baptista, , MJR Barboza,
Published: October 2020

The present work aims nitriding to investigate the effect on titanium grade 2 with rotating bending fatigue tests at room temperature and short-term creep tests at 500°C. The nitriding treatment was carried out at 850°C for 9 hours. After thermochemical treatment, XRD analysis revealed the formation layer composed of TiN and Ti2N. Microscopy analysis revealed the presence of a uniform layer with a mean thickness of 3.6 mM and 50% increase in surface roughness. Fatigue life (107 cycles) was reduced by 42% by increasing surface roughness. On the other hand, nitriding treatment increased creep life by at least two times due to oxidation rate reducion and blocking dislocations movement by nitrogen in solid solution during the plastic deformation process.
Effect of adiabatic heating on microstructure evolution in Ti-6Al-4V during high strain rate forging
Authors: Kulakov Mykola , Silva Laurie Da , Andreu Aurik
Published: October 2020

The effect of adiabatic heating on microstructure evolution during high strain rate subtransus forging of a Ti-6Al-4V alloy having equiaxed initial microstructure was studied through experiments and modelling. Ø45 × 67.5 mm cylindrical billets with embedded thermocouples were forged at four different α+β temperatures on a Schuler 2100t screw press to evaluate the extent of adiabatic heating in different parts of the billet. In the centre of the billet, the highest temperature increase due to adiabatic heating exceeded the β transus (~1000 °C) during forging. The microstructure of the forged billets was examined for any changes in β phase volume fraction due to adiabatic heating. The forging process was then simulated in Deform 2D/3D software. High strain rate compression testing in the α+β and β temperature fields was carried out using a Phoenix forge simulator to generate input mechanical properties for the model. The effect of the billet size on the α-β phase transformation during forging and post-forge cooling is also discussed.
Characterizing and Modeling the Precursors to Coarse Grain Formation during Beta-Annealing of Ti-6Al-4V
Authors: Pilchak A.L. , Srivatsa S. , Levkulich N.C. , Sinha V. , Payton E.J. , Semiatin S.L.
Published: October 2020

Coarse prior β grains exceeding 3 mm in diameter have been sporadically observed following β annealing of α+β forged titanium alloys. Recent work has shown that the occurrence of coarse grains may be due in part to the stabilization of a {001}<110> texture during hot working that was further enhanced in intensity at the expense of other texture components during the early stages of β annealing. With the majority of the material comprised of low misorientation subgrains of a single texture component, the nuclei for coarse grains was the minority fraction of grains that were highly misoriented, and therefore had boundaries with higher energy and mobility, compared to the average grain. In this work, Ti-6Al-4V bar was side-pressed to various reductions in the α+β phase field to further investigate the role of texture and the effects of strain, strain-path, and deformation heating on the propensity to form abnormally large grains during β-annealing. The experiments were interpreted in the context of a continuum finite element model and viscoplastic self-consistent crystal plasticity simulations. Based on the results from experiment and modeling, we make recommendations with respect to the α+β forging process to avoid the occurrence of excessively coarse β grains.
Development of CALPHAD database for both Ti- and TiAl-based alloys
Authors: Yang Yang , Chen Hai-Lin , Chen Qing , Engström Anders
Published: October 2020

Phase diagram calculations and phase transformation simulations have been widely employed to materials design and process optimization. Recent development of a 27-element thermodynamic database (TCTI2) together with a compatible mobility database (MOBTI3) for Tiand TiAl-based alloys is reported. The TCTI2 database has been developed in a systematic way in order to cope with the complexity in phase relations and phase transformations in both conventional Ti-based and newly emerging TiAl-based alloys. It can be used with Thermo-Calc and the add-on Diffusion Module (DICTRA) and Precipitation Module (TC-PRISMA) for calculations of multi-component alloys. Feasible calculations are ranging from the traditional stable and metastable phase equilibria (β-transus temperature, evolution of phase fractionsvs.temperature, martensitic temperature,etc.) to some thermophysical properties (density, thermal expansion,etc.). Using a combination of TCTI2 and MOBTI3, one can simulate diffusion-controlled phase transformation and precipitation kinetics. The intermetallic TiAl-based alloys are known for their own complexities and the present modeling for α2-Ti3Al and γ-TiAl based alloys will be discussed. Typical calculated examples for various properties in titanium alloys are presented with the emphasis on validation against experimental observations in multi-component commercial alloys. This database is expected to efficiently support further development of Ti- and TiAl-based alloys, as well as to promote process simulations with accurate prerequisites.
Microstructure-twinning relations in beta-Ti alloys
Authors: Gutierrez-Urrutia Ivan , Ji Xin , Emura Satoshi , Tsuchiya Koichi
Published: October 2020

We have investigated twinning-microstructure relations in β-Ti alloys by statistical analysis of the evolving twin structure upon deformation by in-situ SEM testing and electron backscattering diffraction (EBSD). In particular, we have analyzed the effects of crystallographic orientation, grain size and chemical gradient structure on the nucleation and propagation behavior of {332}<113> twins in a β-Ti-15 Mo (wt.%) alloy and a multilayered β-Ti-10Mo-xFe (x: 1-3 wt.%). Microstructural parameters such as number of twins per grain and number of twins per grain boundary area were statistically analyzed.
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.
Evolution of distance between ω particles in metastable β-Ti alloy determined from in-situ small angle neutron scattering
Authors: Zháňal Pavel , Ryukhtin Vasyl , Farkas Gergely , Kadletz Peter , Keiderling Uwe , Wallacher Dirk , Harcuba Petr
Published: October 2020

The evolution of distance between ω particles in metastable β Ti- 15Mo alloy (8.1 in at. %) was determined from in-situ small angle neutron scat- tering (SANS). SANS data were recorded during heating of the material from room temperature to 600 ◦C with the heating rate of 1 ◦C/min. The results agree with previously determined ordering of ω particles in a cubic three-dimensional array with the axes along the cubic axes ⟨100⟩β of the host lattice. The distance between particles, which increases with temperature, was investigated in three orientations with the incident beam parallel to [100]β, [110]β and [111]β.
Criteria for fast and selective α precipitation at β grain boundaries in Ti-alloys Consequence for in-service microstructures
Authors: Liu Tao , Germain Lionel , Teixeira Julien , Aeby-Gautier Elisabeth , Gey Nathalie
Published: October 2020

The potential for β grain boundaries (GBs) to give rise to large Widmanstätten colonies was determined through the observation of a large amount of precipitates at β GBs in a β-metastable titanium alloy using electron backscatter imaging and diffraction. The most critical boundaries are those which transform early and where a type of Variant Selection (VS) called double Burgers VS occurs. This mechanisms take place at ‘special’ β boundaries misoriented so that an α precipitate can be related to both grains through the Burgers relation. It was shown that the most critical GBs have a disorientation at an angle of less than 10° from 49.5°/<110> or 60°/<110>. A simulation study allowed those boundaries to be quantifed in crystallographic textures typical of industrial products. Those texture have then been discussed as a function of their potential to form large Widmanstätten colonies.
Origins and importance of fine secondary α in slowly cooled Ti6Al4V
Authors: Wang M. , Lu Y. , Pang B. , Kloenne Z. T. , Fraser H. L. , Chiu Y. L. , Loretto M. H.
Published: October 2020

It has been known for sometime that slowly cooled Ti6Al4V (Ti64) contains only about 10vol% of β and that this β takes three different forms. Firstly, there are thin volumes of interfacial β, between the grains of α, which are clearly the remains of the β present at high temperatures left when α replaces the β present at high temperatures, by diffusion and boundary migration. Secondly, there are regions of roughly equiaxed β at triple points, but some of this β contains very fine secondary α, whereas the other grains are retained β. Analytical transmission electron microscopy has been used in an attempt to understand the origin of these two different types of equiaxed β grains. It has been found that grains, which are retained β contain about 20wt%V, but the β grains that contain secondary α originate from parent β grains that have only about 14wt%V. The origin and the significance of these observations will be discussed in the presentation.
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.
Die Aus- und Weiterbildungssituation der Abdomensonografie an den deutschen Universitätskliniken. Eine Längsschnittstudie über 20 Jahre
Authors: Welle Reinhard , Seufferlein Thomas , Kratzer Wolfgang
Published: October 2020

Hintergrund Deutschlandweit ist die sonografische Ausbildung nicht einheitlich geregelt. Ziel der aktuellen Studie ist, eine aktuelle Bestandsaufnahme der Aus- und Weiterbildungssituation der Abdomensonografie an den deutschen Universitätskliniken zu leisten und die Ergebnisse mit den 1999 und 2009 durchgeführten Vorgängerstudien vergleichend auszuwerten.

Methoden Im Rahmen der postalisch durchgeführten Umfragestudie wurden die ärztlichen Leiter der gastroenterologischen Abteilungen der 34 deutschen Universitätskliniken zu den Themenkomplexen technische Ausstattung, Untersuchungszahlen, Rolle der Fachgesellschaften, Ausbildung der Studierenden und Gestaltung der ärztlichen Weiterbildung befragt. Die Rücklaufquote betrug 79 %. An einer ergänzenden Online-Lehrevaluation nahmen 1183 Studierende von 34 Fakultäten teil.

Ergebnisse An den Universitätskliniken findet der abdominelle Ultraschall zunehmend in einem interdisziplinären Rahmen statt; inzwischen sind an 29 % der Kliniken interdisziplinäre Ultraschallzentren etabliert. Eine quantitative Verbesserung der Gerätesituation konnte festgestellt werden, pro Klinik stehen 5,2 Systeme zur Verfügung. Dies entspricht einem Plus von 30 % im Vergleich zu 2009 und 27 % im Vergleich zu 1999. Die Investitionsbereitschaft in moderne Geräte hat hingegen abgenommen. Sowohl die Gesamtuntersuchungszahl als auch die Zahl durchgeführter Kontrastmittelsonografien sind in den vergangenen Jahren stetig gestiegen, zwischen 2009 und 2018 um maximal 28 %. Die DEGUM ist zunehmend an den Kliniken vertreten und hat ihre herausragende Rolle in Qualitätssicherung und Weiterbildung weiter ausgebaut. Inzwischen sind 96 % der ärztlichen Leiter Mitglieder der DEGUM und 89 % verfügen über eine Qualifikation des Mehrstufenkonzepts. Hinsichtlich Ausbildungszeit, abzuleistender Untersuchungen und Ausbildungstagen unter Supervision bestehen weiterhin große Unterschiede zwischen den Abteilungen. Durchschnittlich werden mehr Ärzte pro Abteilung und Jahr ausgebildet und eine kontinuierliche und ganztätige Ausbildungszeit von 6 Monaten hat sich an den meisten Kliniken etabliert. Unter Studierenden genießt die Sonografie hohes Ansehen, und es ist eine enorme Einsatzbereitschaft festzustellen. Die Zahl praktischer Kurse und unterrichteter Studierender hat in den vergangenen Jahren zugenommen. Oft besteht jedoch ein Ungleichgewicht von Angebot und Nachfrage nach Lehrveranstaltungen.

Schlussfolgerung Für das ärztliche Personal und die Studierenden hat sich die Ausbildungssituation tendenziell positiv entwickelt, wobei zwischen den Kliniken weiterhin große Qualitätsunterschiede bestehen. Die Abteilungen leisten eine stetig zunehmende Zahl an Ultraschalluntersuchungen; eine adäquate Verbesserung der Gerätesituation konnte nicht festgestellt werden. Die DEGUM hat ihre Bedeutung als wichtigste den Ultraschall vertretende Fachgesellschaft weiter ausgebaut.
The Effect of Pituitary Gland Disorders on Glucose Metabolism: From Pathophysiology to Management
Authors: Sydney Guy I. , Michalakis Konstantinos , Nikas Ilias P. , Spartalis Eleftherios , Paschou Stavroula A.
Published: October 2020

This review aims to explore, present, and discuss disorders of glucose metabolism implicated in pituitary gland diseases, the appropriate interventions, as well as the therapeutic challenges that may arise. Pituitary pathologies may dysregulate glucose homeostasis, as both the excess and deficiency of various pituitary hormones can affect glucose metabolism. Increased circulating levels of growth hormone, glucocorticoids or prolactin have been shown to mainly provoke hyperglycemic states, while hypopituitarism can be associated with both hyperglycemia and hypoglycemia. Addressing the primary cause of these disorders with the use of surgery, medical treatment or radiotherapy forms the cornerstone of current management strategies. Physicians should bear in mind that some such medications have an unfavorable effect on glucose metabolism too. When unsuccessful, or until the appropriate treatment of the underlying pituitary problem, the addition of established antidiabetic therapies might prove useful. Further studies aiming to discover more accurate and effective drug preparations in combination with optimal lifestyle management models will contribute to achieving a more successful glycemic control in these patients.
Correlation between Primary Myelofibrosis and the Association of Portal Thrombosis with Portal-Biliary Cavernoma: US, MDCT, and MRI Features
Authors: Girolamo Marco Di , Galassi Stefania , Merola Salvatore , Bonome Paolo , Conte Esmeralda , Iannicelli Elsa
Published: October 2020

Objective Myelofibrosis is a rare chronic myelolymphoproliferative disease and is associated with increased risk of venous thromboembolism. The objective of this study is to retrospectively evaluate patients with primary myelofibrosis who underwent abdominal US, MDCT and MRI, in order to identify the development of portal thrombosis and its correlation with portal-biliary cavernoma.

Methods We evaluated 125 patients with initial diagnosis of primary myelofibrosis and nonspecific abdominal pain who had undergone US with color Doppler. In 13 patients (8 men, 5 females; age: 45–85), US detected portal thrombosis with associated portal-biliary cavernoma. All patients subsequently underwent contrast-enhanced MDCT and MRI and 4 patients MR-cholangiography. The correlation between primary myelofibrosis and portal thrombosis and cavernoma respectively was calculated using χ2 test.

Results About 10% of patients with primary myelofibrosis preliminary evaluated with US had partial (8 pts) or complete (5 pts) portal thrombosis associated with portal-biliary cavernoma with a χ2 = 0. In all patients, US detected a concentric thickening of main bile duct (MBD) wall (mean value: 7 mm); color Doppler always showed dilated venous vessels within the thickened wall of the biliary tract. Contrast-enhanced CT and MRI confirmed thickening of MBD walls with their progressive enhancement and allowed better assessment of the extent of the portal system thrombosis. MR-cholangiography showed a thin appearance of the MBD lumen with evidence of ab extrinsic compression.

Conclusions The evidence of portal thrombosis and portal-biliary cavernoma in 10% of the patients with primary myelofibrosis indicates a close correlation between the two diseases. In the detection of portal thrombosis and portal-biliary cavernoma, US with color Doppler is the most reliable and economical diagnostic technique while contrast-enhanced MDCT and MRI allow better assessment of the extent of the portal vein thrombosis and of the complications of myelofibrosis.
Ruptured Pancreaticoduodenal Artery Pseudoaneurysm in an Unusual Location in a Patient with Chronic Pancreatitis: A Case Report
Authors: Wongwaisayawan Sirote , Papadatos Demetri , Aina Rima , Sheikh Adnan
Published: October 2020

Bleeding pseudoaneurysm is a rare but yet potentially lethal complication in a patient with chronic pancreatitis. It also poses a diagnostic challenge among the radiologists and the attending physicians. The mortality rate can be as high as 50% depending on the clinical status, patient hemodynamics, site, and characteristics of the bleeding pseudoaneurysm. Multidisciplinary team approach is essential to deliver the optimum treatment strategy to each individual patient. In this article, we present a case of chronic pancreatitis that presents with acute epigastric pain caused by ruptured pancreaticoduodenal artery pseudoaneurysm in an unusual location. This patient was successfully treated with transcatheter coil embolization.
Law-abiders, lame ducks, and over-stayers: the Africa Executive Term Limits (AETL) dataset
Authors: Cassani Andrea
Published: October 2020

Besides elections, the sub-Saharan wave of political reforms of the 1990s led several countries to introduce limits to the number of terms that a chief executive can serve, even though several leaders managed to bypass them. While Africa’s executive term limits (ETLs) politics has gained scholarly attention, the literature mostly consists of in-depth small-N analyses. Systematic comparative research is rare. To contribute filling this gap, this article presents a new Africa Executive Term Limits (AETL) dataset. Covering 49 sub-Saharan polities throughout the 1990–2019 period, AETL represents the most complete and updated collection of data on Africa’s ETLs politics, and a versatile research tool to address several questions on the present and future of this continent. A preliminary assessment of the new data finds ETLs to be increasingly respected, and to have positive returns for government alternation and development. These findings point to new research avenues that AETL may help travel.
Molecular beam epitaxy of the magnetic Kagome metal FeSn on LaAlO3 (111)
Authors: Hong Deshun , Liu Changjiang , Hsiao Haw-Wen , Jin Dafei , Pearson John E. , Zuo Jian-Min , Bhattacharya Anand
Published: October 2020

Materials with Kagome layers are expected to give rise to rich physics arising from band structures with topological properties, spin liquid behavior, and the formation of Skyrmions. Until now, most work on Kagome materials has been performed on bulk samples due to difficulties in thin film synthesis. Here, by using molecular beam epitaxy, layered Kagome-structured FeSn films are synthesized on the (111) oriented LaAlO3 substrate. Both in situ and ex situ characterizations indicate that these films are highly crystalline and c-axis oriented, with atomically smooth surfaces. The films grow as disconnected islands, with lateral dimensions on the micron meter scale. By patterning Pt electrodes using a focused electron beam, the longitudinal and transverse resistance of single islands have been measured in magnetic fields. Our work opens a pathway for exploring mesoscale transport properties in thin films of Kagome materials and related devices.
Thermal tomography 3D imaging of additively manufactured metallic structures
Authors: Heifetz A. , Shribak D. , Zhang X. , Saniie J. , Fisher Z. L. , Liu T. , Sun J. G. , Elmer T. , Bakhtiari S. , Cleary W.
Published: October 2020

Thermal tomography is a computational method for heat diffusion-based imaging of solids, which provides 3D visualization of data from flash thermography measurements. We investigate thermal tomography imaging and nondestructive evaluation of stainless steel and nickel super alloy metallic structures produced with the laser powder bed fusion (LPBF) additive manufacturing (AM) process. Metallic structures produced with LPBF contain defects, and there are limited capabilities to evaluate these structures non-destructively. Thermal tomography reconstruction of 3D apparent spatial effusivity provides information about AM structure geometry and internal material flaws. We study performance of thermal tomography in imaging of metallic structures through COMSOL computer simulations of transient heat transfer and through reconstruction of data obtained from experimental measurements. Thermal tomography reconstructions of structure shape and dimensions are shown for the Inconel 718 AM structure which has variations in the horizontal plane but is uniform along the depth dimension. Reconstruction of internal defects is investigated using a stainless steel 316L specimen with flat bottom hole (FBH) indentations, and the Inconel 718 plate is produced with the LPBF method, which contains imprinted hemispherical shape low density regions containing non-sintered metallic powder. The FBHs have the same sizes as the imprinted defects in the LPBF specimens but offer better imaging contrast. Thermal tomography reconstructions provide visualizations of internal defects and allow for estimation of their sizes and locations. Results of this study demonstrate that thermal tomography can be used for visualization and quality control in AM.
Fundamentals of light-cell–polymer interactions in photo-cross-linking based bioprinting
Authors: Nieto Daniel , Marchal Corrales Juan Antonio , Jorge de Mora Alberto , Moroni Lorenzo
Published: October 2020

Biofabrication technologies that use light for polymerization of biomaterials have made significant progress in the quality, resolution, and generation of precise complex tissue structures. In recent years, the evolution of these technologies has been growing along with the development of new photocurable resins and photoinitiators that are biocompatible and biodegradable with bioactive properties. Such evolution has allowed the progress of a large number of tissue engineering applications. Flexibility in the design, scale, and resolution and wide applicability of technologies are strongly dependent on the understanding of the biophysics involved in the biofabrication process. In particular, understanding cell–light interactions is crucial when bioprinting using cell-laden biomaterials. Here, we summarize some theoretical mechanisms, which condition cell response during bioprinting using light based technologies. We take a brief look at the light–biomaterial interaction for a better understanding of how linear effects (refraction, reflection, absorption, emission, and scattering) and nonlinear effects (two-photon absorption) influence the biofabricated tissue structures and identify the different parameters essential for maintaining cell viability during and after bioprinting.
Basic Concepts
Authors: Meli Jerome A.
Published: October 2020

This chapter is a review of the basic principles of classical and modern physics that are used throughout the book. The classical two-particle collision is analyzed with emphasis on scattering angles and energy transferred from projectile to target. Electromagnetic radiation and its interactions with charged particles are reviewed. The behavior of relativistic kinetic energy and its implications for particle interactions are discussed. From modern physics there is a review of atomic structure, the photon concept, and nuclear and atomic sizes.
Stopping Power of a Medium for Charged Particles
Authors: Meli Jerome A.
Published: October 2020

The classical cross section for charged-particle interactions is used to estimate the ratio of hard to soft collisions. For fast charged particles, the cross section obtained from a straight trajectory approximation is used to derive an expression for the non-relativistic collision stopping power. This is extended to a discussion of stopping power for relativistic particles and radiative stopping power for light particles. The behavior of stopping power with particle energy and depth in a medium is also discussed.
Interactions of Photons: Cross Sections
Authors: Meli Jerome A.
Published: October 2020

In this chapter, cross sections are discussed for Rayleigh, Compton, photoelectric, and pair production interactions as well as the angular and energy distribution of Compton electrons. The role each interaction plays in attenuation of photon beams is energy dependent. This concept is discussed at length and applied to show that inherent contrast between two mediums increases with decreasing photon energy.
Dose in Photon Beams
Authors: Meli Jerome A.
Published: October 2020

Equations are derived for kerma and collision kerma in terms of average energy transferred to charged particles and in terms of the mass transfer coefficient and mass–energy absorption coefficient. Charged-particle equilibrium of primary electrons is described and the equality of dose and collision kerma under this condition is discussed. The relation between dose to two different mediums is derived. Examples are given.
Measuring Air Kerma, Exposure, and Dose in kV X-ray Beams
Authors: Meli Jerome A.
Published: October 2020

The free air ionization chamber and its use to determine exposure and air collision kerma are discussed. Practical chambers commonly used for dosimetry are discussed along with the method used by NIST to provide chamber calibration factors for kilovoltage x-ray beams. Applications of how these factors are used to measure exposure rates of beams are given along with corrections that have to be made for collection efficiency and temperature and pressure.
Ionization Chamber Measurement of Dose in MV Beams
Authors: Meli Jerome A.
Published: October 2020

The mass of an ionization chamber's gas is determined from a 60Co calibration factor and used to define the dose calibration factor, Ngas, as used in the TG-21 protocol. The NIST water calorimeter is described along with its use to obtain a water-to-dose calibration factor for chambers as used in the TRG-51 protocol.
Dosimeters Other Than Ion Chambers
Authors: Meli Jerome A.
Published: October 2020

The use of ferrous sulfate as an absolute dosimeter for dose to water is described. Calibration of detectors that are not absolute dosimeters, such as diodes, MOSFETS, film, and TLDs, is discussed with emphasis on the photon energy dependency of a detector's response.
The processing of case in intermediate L2 Spanish
Authors: Jegerski Jill
Published: October 2020

This self-paced reading study investigated the processing of case marking with the particle a in non-native Spanish. Experiment 1 tested online sensitivity to case marking on direct and indirect objects. Unlike native speakers, intermediate L2 learners showed effects only with indirect objects. For Experiment 2, direct objects were doubled with a preverbal clitic, to see if the addition was associated with more native-like processing, as has been shown in previous research with very advanced L2 learners (Jegerski, 2015). Again, online sensitivity to case marking was only observed with the ditransitive stimuli. Thus, clitic doubling only seems to make a difference at sufficiently high levels of proficiency, perhaps because of increasingly robust representations of grammatical forms in the developing L2 system.