bluuebunny/crossref_metadata_2025 huggingface dataset:
H effect on the plasticity of Ti575 alloy
Authors: Zhang Zhenbo , Lunt David , Platt Philip , Preuss Michael
Published: October 2020

Adsorption of hydrogen (H) can result in severe performance degradation of Ti alloys. In this study, the effect of H on the plasticity of Ti-5Al-7 5V-0.5Si (Ti575) alloy is investigated. High resolution digital image correlation (HRDIC) is employed to elucidate the effect of H on the strain distribution and dislocation slip character of the alloy during mechanical loading. It is found that H enhances slip heterogeneity and promotes the formation of long and sparse prismatic slip bands in the α phase, which can extend to across several grains. Such heterogenous prismatic slip bands are likely to originate from the lenticular hydrides, which have the prismatic plane as their habit plane. In addition, H also shows considerable effect on the plasticity of β phase, which facilitates the slip transmission and enhances the slip localisation.
Synthetic rutile derived titanium alloy development utilising the Metalysis Process and field assisted sintering technology
Authors: Graham Simon J. , Benson Lyndsey L. , Jackson Martin
Published: October 2020

Utilising novel extraction and processing technologies allows for the realisation of an alternative titanium alloy production route, with many benefits over the traditional Kroll-based one. The route proposed has the potential to reduce the cost of titanium and offers the ability to create alloys which are difficult to make conventionally. It combines the Metalysis Process, an electrolytic metal extraction technique, with field assisted sintering technology (FAST), a rapid and effective solid-state sintering technique. The Metalysis Process reduces metal oxide powders directly into metal powders, which can then be consolidated using FAST. Using synthetic rutile (SR) as the feedstock, compared to pigment grade rutile and TiCl4, further reduces the cost of titanium produced via this route.

This research investigates the use of this route to create a range of pseudo-binary Ti-Fe alloys, by co-reducing SR with iron (III) oxide (Fe O ). Various techniques were used to analyse the feedstock, reduced alloy powders and consolidated material post-FAST to 23 determine chemistry and microstructure.
Investigation of α-Ti plastic anisotropy under thermomechanical loadings: temperature influence on deformation mechanisms
Authors: Agbovi K. E. , Fajoui J. , Girault B. , Gloaguen D. , Kabra S. , Kelleher J. , Kockelmann W.
Published: October 2020

In situneutron diffraction method has been used to investigate deformation mechanisms (slip and twinning deformation modes) during uniaxial tensile tests of extruded a-titanium alloy at room temperature, 100 and 300 °C. For this purpose, the prediction of an Elasto-Plastic Self-Consistent (EPSC) model was compared with the experimental data. Results show that there is a good agreement between the simulations and neutron diffraction measurements. The EPSC model enables realistic predictions of not only the elastic lattice strains developed in variously oriented grain families but also the macroscopic stress-strain response within the bulk material.
Production of spherical titanium alloy powders used in additive manufacturing from titanium scrap
Authors: Yanko Taras , Brener Viktor , Ovchinnikov Olexandr
Published: October 2020

The main materials for 3D printing of titanium are fine metal alloy powders from which produce final articles with required quality. These powders must have definite chemical compositions, physical/mechanical characteristics, and also necessary operational properties. Key parameters of titanium alloy powders are homogeneity of chemical compositions, microstructures as well as flow ability. Conventional atomisation methods for metal powders like GA, PREP, PA, etc, are complicated and sufficiently expensive. Alternative production route is usage of complex processing technology of titanium alloy scrap as initial raw material. Spheriodised powder manufacturing scheme which includes raw material preparation, preliminary and final treatments have been presented. At the first step titanium scrap was divided according to titanium alloy types, purified from contaminants and oxide films. Then prepared materials were converted to non-spherical powders with definite fractional compositions using hydrogenation/de-hydrogenation (HDH) method.

Experimental HDH equipment allows close cycle of hydrogen recovery almost without losses. Obtained non-spherical powders were treated in the plasma unit yielding spherical titanium alloy. Offered technical solutions permit production of raw materials for 3D printing from scrap with high actual yield of required fractional compositions.
Influence of bath composition on Ti metal deposition in molten CaCl2 containing calcium titanate
Authors: Takenaka T. , Okada H. , Shimokawa R. , Morishige T.
Published: October 2020

The dependence of the cathodic behavior of a Ti ion on the molar ratio of CaO to TiO2 (RCaO/TiO2) was investigated in molten CaCl2 above 1373 K, and the influence of RCaO/TiO2 on Ti metal deposition was discussed. The reduction mechanism changed at RCaO/TiO2 = 1.5; a three-step reduction of Ti was suggested in the melt of RCaO/TiO2 < 1.5, while a two-step reduction seemed to occur above RCaO/TiO2 = 1.5. Titanium metal deposition was also affected by RCaO/TiO2 as well as by the cathode potential, and the suitable RCaO/TiO2 was likely 1.5. Since this value was the same as the suitable value in the molten fluoride system, Ti metal was thought to be obtained only from Ti2O76-. Silicon and Al metal were obtained electrochemically in molten CaCl2 containing calcium silicate and aluminate more easily than Ti metal. The difficulty of the Ti metal deposition is likely to be caused by the so-called shuttle reaction; the shuttle reaction can occur in the Ti metal electrolysis because some ionic states of Ti are stable in the bath. To realize better Ti metal deposition, the control of the shuttle reaction should be important.
The effect of notch size on fatigue crack threshold and propagation in cast gamma titanium aluminide
Authors: Trant Claire , Martin Nigel , Dixon Mark , Saunders Edward , Lindley Trevor , Dye David
Published: October 2020

Cracks were initiated and grown from notched specimens with notch lengths of 0.03 (FIB), 0.06, 0.1 and 0.5 mm (diamond blade), in cast gamma titanium aluminide at 400 oC. Specimens with longer 0.1 and 0.5 mm notches initiated from the notch and show no effect from initial notch size on either crack growth threshold or propagation. Specimens with shorter 0.03 and 0.06 mm notches initiated naturally, cracking from microstructural features away from the notch. The fracture surfaces of these specimens were characterised to distinguish areas of initiation, fatigue and overload. Multiple initiation sites were observed on these fracture surfaces. It is inferred that, for this alloy and process route, microstructural initiation is dominant where notches are less than ~100 µm in size.
Impact of rolling conditions on the hydriding of grade 2 titanium welded tubes
Authors: LEPEMANGOYE La Chance , CRETON Nicolas , OPTASANU Virgil , DELOYE Elise , MONTESIN Tony , FUNDENBERGER Jean-Jacques , PERROUD Olivier
Published: October 2020

In this article, we study the impact of rolling conditions on the texture of the commercially pure titanium grade 2. In a previous work, NEOTISS in collaboration with ICB laboratory, shown that the texture highly influences the precipitation of hydrides in Titanium. In order to create different textures, Titanium sheets grade 2 are cold rolled asymmetrically and symmetrically with or without lubricant. The inverse pole figures and direct pole figures obtained allow us to deduce that symmetrical cold rolling does not change the grains orientation but generates a rotation of grains along c-axis (normal to basal plan). However, asymmetrical cold rolling leads to the formation of a new crystallographic texture, which could limit the formation of the hydrides in titanium grade 2 submitted to a hydrogen-rich environment.

Key words: asymmetrical rolling, symmetrical rolling, titanium, hydriding, texture
Characterization of the thermal flux transferred by the plasma arc to the surface of the liquid bath in the Plasma Arc Melting Cold Hearth Refining process (PAMCHR)
Authors: Décultot Léa , Jardy Alain , Hans Stéphane , Doridot Emiliane , Delfosse Jérôme , Ruby-Meyer Fabienne , Bellot Jean-Pierre
Published: October 2020

Europe is a major provider of titanium scrap but until now there has been no european facility dedicated to the production of aeronautical quality titanium alloys by recycling. UKAD, a joint-venture between Aubert & Duval and UKTMP, ADEME and Crédit Agricole Center France, created the company EcoTitanium, where the recycling of machining scraps is achieved using the Plasma Arc Melting Cold Hearth Refining (PAMCHR) process with the aim of producing such alloy ingots.

The determination of the heat flux transferred from the plasma column to the surface of the liquid bath is an important issue needed for the development of a future 3D process modeling based on Ansys-Fluent CFD software. With this preliminary aim of predicting the heat flux, a study coupling pilot furnace testing and numerical modeling has been performed. Melting tests were carried out in a pilot PAMCHR furnace in MetaFensch, with a stationary torch. In parallel, the different contributions of the heat flux transferred to the surface of the liquid bath were identified and implemented in a simple 2D axisymmetric heat transfer model. Numerical results are compared to the experimental measurements, in order to define the heat flux transferred from the plasma torch.
Electron beam melting toward defects-free titanium alloys
Authors: Funagane H. , Takeda Y. , Wada M. , Mizukami H. , Umeda S.
Published: October 2020

Titanium alloys used for rotating parts of aeroplanes must meet the strict standards of quality, so that it is required to demonstrate that electron beam melting is capable of producing defects-free ingots. However, complete elimination by dissolution of low density inclusions (LDI) having high nitrogen content would be difficult, so that a new way of eliminating LDI was needed. Therefore, control of a state of the molten titanium flow with the aide of Marangoni flow induced by electron beam has been studied, and the effects on eliminating LDI have been verified.
Revisited: gas-saturated defects in titanium alloys
Authors: Leder M.O. , Puzakov I.Yu. , Tarenkova N.Yu. , Kornilova M.A. , Rusakov K.A.
Published: October 2020

The simulation results of the internal defects generated during deformation by extrusion and rolling are presented herein. It was demonstrated that end-type deformation defects can result in the formation of internal gas-saturated defects not cropping out the surface under the specific deformation conditions. Key characteristics of the generated defects similar to those of the production defects that have been previously classified as metallurgical are determined.

Key words: defect, deformation, discontinuity.
Reactions of alkaline earth zirconate refractories with titanium alloys
Authors: Schafföner Stefan
Published: October 2020

The severe reactivity of titanium alloys with ceramics is a major challenge for their processing. Up to now refractories to melt and cast titanium alloys are selected on the basis of a low Gibbs energy of formation. This kind of selection assumes that an oxide should be stable if its Gibbs energy of formation is lower than the one of any titanium (sub)oxide. The present contribution reviews that these models trying to explain the stability of ceramic materials in contact with titanium alloys are often misleading. By contrast, a dissolution and evaporation based reaction model is more appropriate to describe the reaction of high temperature ceramics with titanium alloys. These explanations were exemplified by research findings of high temperature reactions of titanium alloys with calcium oxide and yttrium oxide. Based on the discussion on calcium and yttrium oxide, the reactions of alkaline earth zirconates such as calcium and barium zirconate with titanium alloys were discussed. The reaction of alkaline earth zirconates is also highly dependent on the titanium alloy composition. It was also demonstrated that not only thermodynamics but also kinetics should be considered to evaluate refractories for titanium processing.
Effect of stress relaxation on the evolution of residual stress during heat treatment of Ti-6Al-4V
Authors: Rae W. , Rahimi S.
Published: October 2020

Titanium alloys, such as Ti-6Al-4V, are extensively used in critical aerospace applications. Heat treatments are often conducted during forging processes to produce final microstructures which exhibit advantageous mechanical properties. However, high thermal gradients present during processing may lead to the generation of undesirable levels of residual stress. Stress relief can be achieved by conducting aging or annealing treatments at elevated temperatures, yet there is limited quantitative understanding of how holding temperature affects the evolution of residual stress. Stress relaxation testing was conducted between 500-750°C and the resulting response was modified to describe creep strain. This was implemented in DEFORM™ finite element analysis software to model the evolution of residual stress during solution treatment followed by aging between 500-750°C, with comparison against solutions which did not consider creep strain. Stress relaxation phenomena was found to have an important impact on the reduction of residual stress and needs to be considered when carrying out thermo-mechanical processing at elevated temperatures.
The Deformation Behavior of Oxygen-Modified Ti-29Nb-13Ta-4.6Zr(wt.%)
Authors: Khademi V. , Liu H. , Nakai M. , Niinomi M. , Boehlert C.J.
Published: October 2020

A series of Ti-29Nb-13Ta-4.6Zr(wt.%) {TNTZ} alloys containing either 0.1, 0.3 or 0.7(wt.%) oxygen (O) were room-temperature tensile tested inside a scanning electron microscope to evaluate the effect of O on the deformation evolution. The deformation modes observed for TNTZ-0.1O, which exhibited the largest elongation-to-failure and lowest strength of all the alloys, were deformation-induced α”-martensitic transformation, {332}<113> twinning, and <111> slip. For the other two alloys, <111> slip was the dominant deformation mode, where TNTZ-0.7O exhibited more homogeneous and extensive slip, a higher frequency of cross slip, and a higher work-hardening rate, all of which contributed to both its strength and elongation-to-failure being greater than that for TNTZ-0.3O. TNTZ-0.3O exhibited the greatest tendency for cracking, which generally occurred on grain boundaries perpendicular to the tensile axis, leading to the lowest elongation-to-failure of all the alloys.
Development of High Temperature Oxidation Resistant Titanium Alloy Arconic-THORTM
Authors: Sun Fusheng , Crist Ernie
Published: October 2020

The aeroengine and airframe applications of titanium alloys are often limited by their insufficient oxidation resistance to the aggressive environment at higher temperatures. A high temperature oxidation resistant titanium alloy (Arconic-THORTM) has been developed. This alloy is an alpha-beta alloy with superior oxidation resistance and improved creep resistance. The oxidation weight gain of Arconic-THORTM is much lower than Ti-6242 and Beta 21s in the temperature range up to 750˚C. The room and elevated temperature properties of Arconic-THORTM are comparable to those for Ti-6242. Arconic-THORTM also shows superior, post-thermal-exposure tensile strength, ductility, and fatigue properties, and is capable of being cold formed, hot formed, and superplastic formed, welded and heat treated to different product geometries. The microstructures and mechanical properties for sheet manufactured from the production ingots are presented and discussed in this study.
Effect of cross-sectional area reduction rate and alloy composition on the formation of <001>-fiber texture in Ti-Mo-Al-Zr alloy wire
Authors: Shinohara Yuri , matsumoto Yoshiki , Tahara Masaki , Hosoda Hideki , Inamura Tomonari
Published: October 2020

Texture formation in Ti-7Mo-8Al-6Zr cold-groove-rolled alloy wires was investigated and compared to that of Ti-5.5Mo-8Al-6Zr. Irregularly textured <001>-fiber was formed in Ti-5.5Mo-8Al-6Zr. The Ti-7Mo-8Al-6Zr cold-groove-rolled wire mainly composed of the β phase though α″ martensite was induced by cold-groove-rolling in the Ti-5.5Mo-8Al-6Zr alloy. From the TEM observations of the severely deformed cold-rolled sheet, α″ martensite was assumed to be induced during cold-groove-rolling and trace α″ was assumed to be retained after cold-groove-rolling. This texture is common in bcc metals and corresponds to the <010>α″ -fiber which is formed in the Ti-5.5Mo-8Al-6Zr alloy when the lattice correspondence between β and α″ is considered. On the other hand, the <001>-fiber was strongly developed in the cold-groove-rolled wire with a reduced cross sectional area of 98% following solution treatment, while this texture was not observed in the specimen with a 60% reduced cross sectional area. The texture formed in solution-treated Ti-7Mo-8Al-6Zr alloy wire was similar to that of the Ti-5.5Mo-8Al-6Zr alloy, although the dominant phase in the cold-groove-rolled specimen differed.
Influence of microtexture on ultrasonic reflection in Ti-6Al-4V alloy hot-forged in α+β region
Authors: Ito Yoshinori , Takamatsu Hiroyuki , Saeki Shogo , Tsuji Nobuhiro
Published: October 2020

Morphological change in regions with microtexture, i.e., macrozones, in Ti-6Al-4V alloy after hot-forging in α+β phase region was analyzed using SEM/EBSD technique, and then the correlation with ultrasonic reflection was investigated. Starting material had colony-type microstructure consisting of lamellar-α with the same crystallographic orientation. Forging (cogging and upsetting) was conducted in α+β phase region to produce a cylindrical material with smaller cross section, followed by air cooling. Thus, resulting microstructure consisted of granular-α. To estimate local change in elastic modulus within the materials, we analyzed crystallographic orientations of α-phase using SEM/EBSD in terms of an inclination angle of c-axis. The regions having the nearly common crystallographic orientations of α-phase were found. Shapes of such regions with microtexture were elongated along the axial direction, which formed quasi-periodic variation of the inclination angle, i.e., elastic modulus, of α-phase along the radial direction of the forged material. Ultrasonic measurement was conducted at a frequency of 5 MHz along the radial direction and the axial direction. Relationship between the morphology of regions having microtexture and the amplitude of backscattered noises was evaluated. It was considered that the quasi-periodicity of the inclination angle correlated with the amplitude of backscattered noises in ultrasonic measurement.
Structure and Properties of Layered Ti-6Al-4V-Based Materials Fabricated Using Blended Elemental Powder Metallurgy
Authors: Prikhodko S.V. , Ivasishin O.M. , Markovsky P.E. , Savvakin D.G. , Stasiuk O.O.
Published: October 2020

Due to the high specific strength of Ti, materials on its base are indispensable when high-strength and low-weight requests are a chief demand from the industry. Reinforcement of Ti-alloys with hard and light particles of TiC and TiB is a credible pathway to make metal matrix composites (MMC) with enhanced elastic moduli without compromising the material’s low-weight. However, reinforcement of the alloy with hard particles inevitably lowers the value of toughness and plasticity of material. Yet, in many applications simultaneous high hardness and high plasticity are not required through the entire structure. For instance, parts that need enhanced wear resistance or resistance upon ballistic impact demand high hardness and strength at the surface, whereas their core necessitates rather high toughness and ductility. Such combination of mechanical properties can be achieved on layered structures joining two and more layers of different materials with different chemical composition and/or microstructure within each individual layer.

Multi-layered structures of Ti-6Al-4V alloy and its metal-matrix composites (MMC) with 5 and10% (vol.) of TiC and TiB were fabricated in this study using blended elemental powder metallurgy (BEPM) of hydrogenated Ti. Post-sintering hot deformation and annealing were sometimes also employed to improve the microstructure and properties. Structure of materials were characterized using light optical microscopy, scanning electron microscopy, electron backscattered diffraction, x-ray microscopy, tensile and 3-point flexural tests. The effect of various fabrication parameters was investigated to achieve desirable microstructure and properties of layered materials. Using optimized processing parameters, relatively large multilayered plates were made via BEPM and demonstrate superior anti-ballistic performance compared to the equally sized uniform Ti-6Al-4V plates fabricated by traditional ingot and wrought technology.
Experimental investigations for a postweld heat treatment on Ti-6Al-4V titanium welds with a defocused laser beam
Authors: Beguin J.D. , Balcaen Y. , Alexis J. , Andrieu E.
Published: October 2020

The purpose of this study is to apply a local heat treatment (LHT), in-situ, on the weld bead, using a defocused Yb: YAG laser beam on a continuous regime, in order to reduce residual stresses and decompose the brittle a’ martensite, into a lamellae and fine β phase. Laser scan experiments were firstly performed on a commercially pure titanium grade 2, with a wide range of parameters, in order to provide a “heat treatment window” without titanium melting. After optimization of the processing parameters, to obtain a sufficient width and depth for the scanning zone, experiments have been performed on a β-treated, fully martensitic Ti-6Al-4V sheet. For each processing experiments, the decomposition of a’, was studied based on metallographic cross sections. A local heating with a minimum energy density at 700 J.cm-2, has a sufficient effect to destabilize a’, while for an energy density at 1000 J.cm-2 , a diffusional transformation take place, with the formation of Widmanstätten microstructure. Finally, these optimized conditions were applied on a full penetration Ti-6Al-4V welds. The results of the LHT will be described in terms of the microstructural changes observed in the welded zone and hardness evolution.
Understanding strain localisation behaviour in a near-α Ti-alloy during initial loading below the yield stress
Authors: Dichtl Claudius , Lunt David , Thomas Rhys , Atkinson Michael , Thomas Matthew , Rugg Dave , Sandala Rebecca , Quinta da Fonseca Joao , Preuss Michael
Published: October 2020

Near-α Ti-alloys such as TIMETAL® 834 are known for their superior mechanical properties at high temperature, and as such are found in applications where high strength and improved fatigue performance at elevated temperatures (>450°C) are required. However, these alloys can be susceptible to cold-dwell fatigue; a failure mechanism that is not well understood. The present work investigates the strain localisation behaviour during cold creep and the implications it has in terms of dwell susceptibility for two different bi-modal microstructures. Slip traces and strain distributions have been analysed for different material conditions by employing High-Resolution Digital Image Correlation (HRDIC) in combination with orientation mapping. Using this approach, it was possible to distinguish deformation patterns in primary α grains and transformed-β colonies, loaded incrementally to stress levels of 70%, 80% and 90% of the yield stress. Different prior β-grain morphologies didn’t affect the average strains when stresses are low; but strain distributions have been affected by the β-grain morphology. Material with coarse transformation product accumulated larger amounts of plastic strain compared to material with fine transformation product, at the same relative stress levels. At low stress levels, slip bands have been detected both in primary α, as well in the transformed-β phase, cutting through the lamellae, for the material condition with a coarse transformation product; on the other hand, for the material conditions with a fine transformation product, slip bands are localised only in primary α grains at low stress levels. It was also found for both conditions that at low stress levels slip bands are found in grains that are well oriented for basal slip. Based on these observations it is discussed if b-ligaments are significant obstacles to dislocation movement. Finally, the requirement of crystal-plasticity modelling to take into account differences in crystallographic orientations and the elastic and plastic anisotropy of HCP-titanium will be discussed and considered.
Ti‐6Al‐2Sn‐2Zr‐2Mo‐2Cr Alloy for High Strength Aerospace Fasteners
Authors: Tamirisakandala Sesh A. , Kamal Manish
Published: October 2020

Next generation demanding aerospace systems requirements are pushing the titanium alloy performance needs beyond the upper limits of the workhorse alloy Ti 6Al-4V (Ti 6-4), necessitating the use of advanced solutions. This paper provides an overview of Arconic’s lightweight solution to address the needs of future aerospace fastening systems. The key attributes for aerospace fasteners are strength (tensile, double shear, and fatigue) and manufacturability (ability to forge heads and roll threads while meeting metallurgical and dimensional requirements) at an affordable cost. In particular, increasing double shear strength (DSS) while meeting other requirements is very challenging. Typically, DSS is about 60% of the tensile strength for Ti 6-4, restricting Ti applications to moderate strength levels. Limited deep hardenability of Ti 6-4 (≤0.5”) also restricts the usage to smaller diameter fasteners. Beta Ti alloys (e.g. Beta C) capable of achieving high tensile strengths suffer from shortfalls in DSS and producibility. There is a need for an affordable high strength Ti alloy that can extend titanium fastener usage to higher strength levels and larger size (up to 1”), which will enable reduction in number of joints and weight reductions by replacing higher density nickel/steel fasteners. Ti 6Al-2Sn-2Zr-2Cr-2Mo (Ti 6-22-22), a judiciously balanced α + β Ti alloy, designed and developed by RMI Titanium Company in the early 1970s for thick-section aerospace structural applications with a need for higher strengths than Ti 6-4, is capable of meeting demanding fastener requirements of next generation aerospace systems. Superior producibility and ability to tailor processing-microstructure-property relationships in Ti 6-22-22 for achieving performance improvements will be discussed in this paper.
Fatigue Performance of the Novel Titanium Alloy TIMETAL®407
Authors: Davey W. , Bache M.R. , Davies H.M. , Thomas M. , Bermant-Parr I.
Published: October 2020

TIMETAL®407 (Ti-407) is a novel titanium alloy formulated as a medium strength, highly ductile alloy offering a range of manufacturing cost reduction opportunities. It can be used as a direct replacement for Ti-6Al-4V or Ti-3Al-2.5V alloys, particularly in applications where energy absorption during fracture or HCF endurance are the key design criteria. The effect of thermo-mechanical processing on microstructure has been characterised and the room temperature high cycle, low cycle and dwell cycle fatigue properties of Ti-407 containing 30-40% primary alpha volume fraction are presented and discussed. These results are compared with data generated from Ti-6Al-4V processed to provide a similar but non-standard microstructure and demonstrate that Ti-407 shows superior HCF endurance strength, despite having a significantly lower tensile and yield strength.
A Comparative Study on the Substructure Evolution and Mechanical Properties of TIMETAL® 407 and Ti-64
Authors: Kloenne Zachary , Viswanathan Gopal , Thomas Matt , Lorreto M.H. , Fraser Hamish L.
Published: October 2020

Titanium and titanium alloys are excellent candidates for aerospace applications owing to their high strength to weight ratio. Alpha/beta titanium alloys are used in nearly all sections of the aircraft, including the fuselage, landing gear, and wing. Ti-6Al-4V is the workhorse alloy of the titanium industry, comprising of nearly 60% of total titanium production. TIMETAL® 407, Ti-0.85Al-3.9V-0.25Si-0.25Fe (Ti-407) is an excellent candidate for alloy applications requiring excellent machinability and increased energy absorption. These properties are a result of the alloy’s increased ductility while maintaining moderate levels of strength. In this study, the deformation mechanisms of Ti-407 have been studied at high strain rates using split-Hopkinson bar testing. Utilizing post-mortem characterization, Ti-407 has been shown to deform significantly by ⟨c+a⟩ slip and deformation twinning. The observation of ⟨c+a⟩ slip is in contrast with other studies and will be discussed further.
Effect of normal annealing and solution temperature on the microstructure and properties of TC4 bar
Authors: Nan YANG , Yong REN , Linlin CUI , Biao JU , Jinwen LEI , Shaoqiang LI
Published: October 2020

The engine is one of the core components of aircraft, and the demand of mechanical properties of its raw materials is higher. The microstructure and properties of the raw materials could be improved by optimizing heat treatment systems. In this paper, the effects of annealing and solution aging on tensile properties of TC4 bar were compared, and the effect of solution temperature on microstructure and tensile properties of bar were studied. The results show that compared with annealing treatment, the tensile strength of bar is improved by 80MPa after solution aging treatment. And with the increase of solution temperature, the content of primary α phase is decreased, the content of secondary α phase is increased, the tensile strength is increased, and the maximum value reaches 1093MPa. Finally, it is determined that the heat treatment system of bar is ℃， ℃， 965 /1h WQ+720 /2h AC.
The Nature of the β→α″ Transformation in Ti-Nb Alloys
Authors: Hildyard E.M. , Connor L.D. , Martin N. , Rugg D. , Stone H.J. , Jones N.G.
Published: October 2020

The martensitic transformation in Ti-Nb alloys can result in superelastic and shape memory behaviour but significant discrepancies exist between the transformation conditions reported for a given composition. To elucidate the reasons for these variations, in situ synchrotron diffraction experiments have been performed on Ti-24Nb (at.%) in two different microstructural conditions. Markedly different transformation behaviour was observed between these two conditions, including fully reversible superelastic behaviour below the apparent martensitic start temperature. These results could not be rationalised using thermally based transformation descriptions. As such, a new approach is introduced based upon the total stress level in a material.
Local Fatigue Crack Propagation Resistance Relevant To Microstructure Uniquely Developed In A Friction Stirred Ti-6Al-4V Alloy Joint
Authors: Okazaki M. , Muzvidziwa M. , Hirano S.
Published: October 2020

The local resistance to fatigue crack propagation (FCP) in a friction stir welded (FSWed) Ti-6Al-4V alloy joint was investigated, by extracting the miniature CT specimens. Special attention was paid to the role of specific microstructures developed accompanying with a transformation induced lamellar structure (TILS) during the stirring process. Experimental works indicated that the FCP rates were higher in the stirred zone, especially in the coarse TILS zone which consisted of the prior non-transformed duplex structure and the beta-transformed coarse structure, compared with those in the base metal. These backgrounds were discussed on the basis of fracture mechanics with Reference to the measurement of residual stress.
Effect of Stress Ratio(R) and Stress Concentration Factor (Kt) on Fatigue Properties of WSTi6211 Titanium Alloy
Authors: Fang Hao , Yong Feng , Yuxuan Du , Yue Wang , Enen Xu , Kaixuan Wang , Yanwen Tian
Published: October 2020

In this paper, the author studied the effects of different stress ratios（R） and stress concentration factors(Kt) on the fatigue properties of WSTi6211 titanium alloy.Through S-N curve, the author obtained the fatigue ultimate strength of the material under different conditions and analyzed characteristics of fatigue fractures, including the crack source sourse, the crack growth region and the final rupture region. The results show that when Kt=1, R=0.5, the fatigue ultimate strength σD is 626MPa; when Kt = 1, R=0.06, the fatigue ultimate strength σD is 527.5MPa; when Kt=3, R=0.06, the ultimate fatigue strength σD is 267MPa. Fatigue performance is very sensitive to R and Kt. The larger R is, the larger the fatigue ultimate strength is. The larger Kt is, the smaller the fatigue limit strength is. The fracture morphology shows typical fatigue fracture morphology. Most of the cracks originate on the surface of specimens and have typical fatigue bands. With the decrease of stress, the area of crack growth zone increases.
The rupture life prediction in cold dwell fatigue of Ti-6Al-4V based on the creep deformation
Authors: Ota Yutaro , Ozaki Tomomichi , Kubushiro.O Keiji
Published: October 2020

Titanium a lloys have been found that the fatigue strength of Ti alloys decreases due to cold dwell fatigue (CDF) at room temperature. Ti and Ti alloys generate creep deformation at room temperature (T/Tm = 0.15). Thus, it is considered that creep affects the reduction in fatigue life in CDF tests. This research intends to clarify the effects of long time dwell under tensile stress and rupture life prediction from the view of creep deformation in CDF characteristics of Ti-6Al-4V. Rupture cycle decreased with increase of dwell time. Additionally, lower limit of rupture life ratio “NCDF/NLCF” was defined from rupture in creep test if it was assumed that creep test was extremely long time dwell CDF test. When strain change in whole dwell time was extracted in CDF tests, strain change was like creep curves and minimum creep rate changed depending on dwell time. Minimum creep rate was calculated by the formula based on experimental results, and then rupture time was calculated by Monkman-grant relationship. All of rupture cycle predictions were in factor of 2. Therefore, rupture cycle and time can be calculated if dwell time is known in CDF tests.
Influence of microstructure evolution during thermal aging on tensile properties of β-type Ti-12V-2Fe-Al alloy
Authors: Wang Weilin , Zhang Xianbing , Sun Jian
Published: October 2020

The evolution of the ω phase and its influence on tensile properties in β Ti-12V-2Fe-1Al alloys aged at temperature from 373 to 573 K were investigated. The results show that the formation of the thermal ω phase starts to take place at temperature between 393 and 423 K in the alloy. The growth of the thermal ω particles is accompanied by a rejection of V, Fe and Al solute atoms from the growing thermal ω particles into the surrounding β matrix. Tensile properties of the β Ti-12V-2Fe-Al alloy are strongly dependent on aging temperature. The plastic deformation mode changes from fully {332} deformation twinning in the ST alloy, to dislocation slip mixed with partially {332} twinning in the alloy aged at 393 K and to dislocation slip associated with stress-induced ω phase transformation in the alloy aged at 423 K. Particularly, the alloys aged at 523 K and above exhibit a brittle fracture without any elongation. It is suggested that the occurrence of the coherent elastic strain between the ω and β phase results in stabilization effect on the β matrix, which may account for the drastic change in plastic deformation mode and tensile properties in aged Ti-12V-2Fe-Al alloys with an increase of aging temperature.
Cyclic creep behaviour of two-phase Ti-6Al-2Mo-2Cr alloy
Authors: Ziaja Waldemar , Motyka Maciej , Kubiak Krzysztof , Sieniawski Jan
Published: October 2020

One of the important criteria for selection titanium alloys for discs and blades of turbine engine compressor is their fatigue and creep strength at room and elevated temperature. Fatigue and creep properties of two-phase titanium alloys show strong dependence on microstructure, especially morphology of the α and β phases which can be controlled to certain extent by proper selection of hot working and heat treatment conditions. Quantitative description of two-phase titanium alloys behaviour under loading and environmental conditions leading to combined creep and fatigue processes has been always very challenging task due to large number of factors affecting deformation and fracture behaviour of the material.

In the course of the research cyclic creep behaviour of Ti-6Al-2Mo-2Cr alloy (VT3-1) was investigated and compared to low-cycle fatigue and static creep properties at the temperature of 450°C. Microstructure of the alloy was varied by means of the heat treatment. Constant load tensile creep tests were carried out. Tension-tension cyclic loading was applied at the constant stress ratio with and without hold time at maximum load. The effect of test parameters on the creep-fatigue life at elevated temperature was estimated. Characteristic features of fracture surfaces were identified by scanning electron microscopy methods.
Advanced Titanium Alloy Fatigue Modeling
Authors: Glavicic Michael G. , Broderick Tom , Venkatesh Vasisht , Cernatescu Iuliana , Legzdina Daira , Barrie Fatmata , Burns Elizabeth , Demptster Ian , Saraf Vikas , Calvert Kayla , Tamirisakandala Seshacharyulu , Shankar Ravi , Salem Ayman , Ghosh Somnath , Almer Jon , Mulsinski William , Shade Paul
Published: October 2020

A summar y of the final progress achieved in two Metals Affordability Initiative (MAI) programs (RR-12 and RR-13) that were funded by the US Air Force to develop the necessary integrated computational materials engineering (ICME) framework, knowledge, and supporting database to model and predict location-specific fatigue properties across the entire titanium supply chain is presented. Validation of this ICME framework which allows for the prediction of location specific low cycle fatigue (LCF) and high cycle fatigue (HCF) behavior on complex production components in electro-polished and shot peened surface conditions will be presented. In addition, validation of a new shot peening capability embedded with the commercial software package DEFORM™ will be presented.
In-situ measurement of the β to α phase transformation kinetics in a Ti-5553 alloy using laser ultrasonics
Authors: Rodrigues M. C. M. , Garcin T. , Militzer M.
Published: October 2020

Ti-5553 alloy (Ti-5Al-5Mo-5V-3Cr wt.%) is one of the newest high strength metastable β-titanium alloys to be used in large section components of aircraft structures. Like other Ti-alloys, Ti-5553 can be strengthened by precipitation of the α-phase during aging heat treatments. In the present study, we explored the potential of laser ultrasonics for metallurgy (LUMet) as an in-situ tool to measure the α precipitation kinetics during high temperature isothermal aging in a Ti-5553 alloy. The observed change in longitudinal ultrasound velocity was seen to be linearly correlated with the α-phase fraction measured via post-mortem electron microscopy. The results are promising for a wider use of LUMet to design optimized heat treatment schedules for commercial Tialloys. Laser ultrasonics offers the potential for real-time monitoring of microstructure evolution in industrial production lines.
Phase field modeling of deformation twinning in β-metastable titanium alloys
Authors: HAMMA Juba , APPOLAIRE Benoît , LE BOUAR Yann , FINEL Alphonse
Published: October 2020

A multi-phase field model describing the anisotropic growth of the {332}<113> twinning system in β-metastable titanium alloys is hereby presented considering the geometrically linear and non-linear frameworks. Phase fields are associated with each twin variant of the {332}<113> system. The lattice transformation describing the twinning systems is incorporated in the model via relevant eigenstrain tensors. We illustrate the capability of our model by investigating the formation of twins networks, within both geometrically linear and non linear frameworks. In particular, it is shown that the predicted microstructures exhibit strong differences, resulting from a difference in the selection of the variant habit planes.
Microstructure and texture in cryomilled and spark plasma sintered Ti Grade 2
Authors: Kozlík Jiří , Stráský Josef , Harcuba Petr , Chráska Tomáš , Janeček Miloš
Published: October 2020

Titanium (Grade 2) was processed by cryogenic milling and subsequently sintered by spark plasma sintering (SPS) method with the aim of creating and preserving the ultra-fine grained (UFG, < 1 μm) microstructure. Microstructural investigation was performed after both cryogenic milling and spark plasma sintering. An advanced technique of transmission Kikuchi diffraction (TKD) was used to characterize the individual milled powder particles.

Investigations of milled powders showed significant grain refinement down to 50 nm after milling in liquid argon with tungsten carbide balls. We assume that this is the equilibrium grain size resulting from the balance of deformation, recovery and dynamic recrystallization. A texture, resembling the rolling texture in Ti, was also found in the milled particles, which can be explained by the nature of deformation during milling.

UFG microstructure was not maintained after sintering, with the mean grain size of 2.6 μm. Although the grains are completely recrystallized, a texture, similar to the powder texture, was also found in these samples as a result of packing of the powder particles and the nature of the recrystallization process (continuous static recrystallization).
Ultrasonic velocity variation of Ti6Al4V Ti-alloy bars under conventional forging combined with triple heat treatment
Authors: Han Feixiao , Hou Fengqi , Sun Xiaoping , Liu Zhixia , He Yonggang , Wang Kaixuan
Published: October 2020

In this paper, the microstructure evolution and ultrasonic velocity variation of Ti6Al4V Ti-alloy bars under different conventional forging deformation degrees and triple heat treatment were investigated, it was found that the the orientation of microstructure is the main factor influencing the ultrasonic velocity. Meanwhile, taking the ultrasonic velocity as target, the ultrasonic velocity variation under given conventional forging process combined with different triple heat treatment conditions (heating temperatures, holding time) were revealed, it was found that the α-β phase ratio, the volume fraction and morphology of equiaxed αp and lamellar αs are also influencing the ultrasonic velocity.
Evolution of α phase in metastable β titanium alloys studied by small-angle X-ray scattering
Authors: Šmilauerová Jana , Harcuba Petr , Stráský Josef , Stráská Jitka , Janeček Miloš , Ilavský Jan , Holý Václav
Published: October 2020

Small-angle X-ray scattering (SAXS) is a technique which makes use of elastic scattering of X-ray radiation on inhomogeneities in electron density in the studied material In particular, a difference in chemical compositions between individual phases can be detected. In this research, SAXS was used to study the evolution of α particles in aged samples of a metastable β titanium alloy, Ti-6.8Mo-4.5Fe-1.5Al (LCB). In order to obtain scattering patterns for a known crystallographic orientation, the experiments were carried out on single crystals grown by a floating zone technique. Aged single-crystalline samples were measured in three different orientations, namely (001), (110) and (111) planes of the bcc β matrix oriented perpendicularly to the primary beam. Resulting scattering patterns exhibited symmetries which correlated with the orientation of the studied sample. A simple theoretical model was developed to interpret the shape and orientation of the observed scattering streaks. Good qualitative agreement between experimental data and simulation was found and the first results of the model are presented in this paper.
Phase separation and up-hill diffusion in the ordered α2 compound of a γ- Ti-Al-Nb alloy
Authors: Gabrisch Heike , Krekeler Tobias , Lorenz Uwe , Rackel Marcus Willi , Ritter Martin , Pyczak Florian , Stark Andreas
Published: October 2020

γ-TiAl alloys are intermetallic materials that are designed for applications in air craft engines. Oftentimes alloying elements are added to improve the corrosion resistance and mechanical properties. Here we investigate microstructural changes that take place when Nb is added to a binary γ-TiAl alloy. Previous studies of the alloy Ti-42Al-8.5Nb have shown that upon Nb addition the orthorhombic O-phase forms out of the parent α2 phase within the alloy’s microstructure. During annealing Nb segregates to the newly formed O-phase while Al and Ti partition to the remaining α2-like matrix phase. The changes these newly formed O-phase domains undergo with time at elevated temperature are not known. Here we use Transmission Electron Microscopy techniques to monitor the distribution of Nb and the size of O-phase domains during long-term annealing between 1 week and 4 weeks at 550°C. The results show that the size of O-phase domains shrinks with annealing time. At the same time the Nb concentration remains largely constant or possibly shows a small decrease.
Wie wirkt Psychotherapie aus Sicht der Patienten?
Authors: Wucherpfennig Felix
Published: October 2020

Die Wirksamkeit von Psychotherapie konnte in einer Vielzahl empirischer Studien belegt werden. Weiterhin fehlt jedoch ein umfassendes Verständnis dafür, warum Psychotherapie wirkt und durch welche Prozesse die Wirksamkeit vermittelt wird. Die meisten Erklärungsmodelle wurden aus der Perspektive des Forschers entwickelt. Um diese Perspektive zu erweitern, untersuchten die Autoren die Wirkungsweise von Psychotherapie aus Sicht der Patienten.
Therapie von Harnwegsinfektionen bei Nierentransplantierten
Authors: Fischereder Michael
Published: October 2020

Harnwegsinfektionen mit gramnegativen Erregern sind auch bei Empfängern von Nierentransplantaten ein häufiges Problem. Die aktuelle Resistenzlage limitiert die zur Verfügung stehenden Substanzen. Zudem sollte der Einsatz der bisher bevorzugten Fluorochinolone aktuell wegen der damit verbundenen Nebenwirkungen kritisch geprüft werden. Fosfomycin trometamol gilt als Antibiotikum der ersten Wahl bei Patienten ohne Immunsuppression.
Herausforderungen in der Behandlung später antikörpermediierter Abstoßung
Authors: Eskandary Farsad-Alexander , Böhmig Georg A.
Published: October 2020

Derzeit gibt es keine Behandlung, die nachweislich in der späten und/oder chronischen antikörpervermittelten Abstoßung (ABMR) wirksam ist. Für Bortezomib und die kombinierte Anwendung von intravenösen Immunglobulinen (IVIG)/Rituximab haben doppelblinde randomisiert-kontrollierte Studien (RCTs) keine signifikante Wirkung auf deren Progression nachgewiesen. Der Antikörper Eculizumab konnte in einer kontrollierten Pilotstudie keine oder nur marginale klinische Wirkungen zeigen. Die größte Hoffnung stellen derzeit Therapien dar, welche die IL-6/IL-6R-Achse (IL-6R: Interleukin-6-Rezeptor) blockieren oder in der Lage sind, CD38-positive Zellen wie Plasma- und natürliche Killer-Zellen (NK-Zellen) zu depletieren.
Immunmodulatoren (Biologicals) in der Therapie von Patienten mit chronischen Dermatosen in der dermatologischen Praxis
Authors: Jahn S. , Föhr J. , Herbst M.
Published: October 2020

Wir fassen Erfahrungen zusammen, die in unserer dermatologischen Praxis in den letzten Jahren, besonders seit der Einrichtung einer Spezialsprechstunde Immundermatologie, mit dem Einsatz von Biologicals gemacht wurden. Dazu charakterisieren wir mittels retrospektiver Auswertung die behandelten Patienten mit Psoriasis (mit und ohne Psoriasis-Arthritis), Neurodermitis, Urtikaria und Akne inversa. Es werden klinische Aspekte der Immunmodulation mittels der Blockade von Zytokinen (TNFα, IL-17, IL-23), deren Rezeptoren (IL-4/13R, IL-17R) bzw. IgE analysiert. Wir zeigen, dass der konsequente Einsatz von Biologicals eine klare organisatorische Entscheidung mit mannigfaltigen Konsequenzen für die gesamte Praxis und das Team darstellt.