Near netshape forming of Ti-Al based intermetallic alloys
Ruy Yang, Yuyou Cui, Lei Xu
Institute of Metal Research, Chinese Academy of Sciences, Shenyang
Intermetallic alloys of the Ti-Al system, such as gamma TiAl and orthorhombic Ti2AlNb, are promising materials to replace some nickel base superalloys to make aero engine components working in the temperature range of 600 to 900⁰C. TiAl based materials are hard to deform and difficult to machine compared to conventional alloys, and the high total cost from material to component must be reduced to facilitate wider application. We shall review efforts to developed a net-shape casting process of TiAl low pressure turbine blades that promises to remove the necessity of machining the aero foil and to significantly reduce the manufacturing cost of this type of components. On the other hand, some engine casings will benefit greatly in weight saving if made of Ti2AlNb base alloys instead of nickel alloys. The challenge is that large Ti2AlNb ingots exhibit elemental segregation which can only be minimised by expensive multiple forging operations. Powder metallurgy is a promising route to solve this problem. This talk will discuss recent progress and issues related to netshape forming by hot isostatic pressing of Ti2AlNb components of complex shape.
Rui Yang obtained his BSc from the Department of Mechanical Engineering, Wuhan Institute of Hydraulic and Electric Engineering in 1984 and read for his MSc in metallic materials at the Institute of Metal Research (IMR), CAS. He obtained a PhD in materials science from the University of Cambridge in 1992 and was elected a Title A Research Fellow of St John’s College Cambridge 1992-1995. He has been the head of Titanium Alloys Division of IMR since 1997. Under his leadership the laboratory developed a number of titanium based materials, including gamma and orthorhombic titanium aluminides, silicon carbide fibre reinforced titanium matrix composite, low modulus superelastic titanium alloys, as well as near net shape processes of powder metallurgy and investment casting. He has authored and coauthored more than 200 peer-reviewed papers and held more than 30 Chinese patents and 2 US patents. He was a recipient of the Applied Science Award from Zhou Guang Zhao Foundation (2010) and of the Metallurgy and Materials Technology Award from Ho-Leung Ho-Lee Foundation (2011).
Scientific and Technological Advances on Additive Manufacturing of High-Performance Large Critical Titanium Structural Components for the Aerospace Industries
H.M. Wang, D. Liu, H.B. Tang, S.Q. Zhang, J. LI, T. Wang, Y.Y. Zhu, X.J. Tian
The National Engineering Laboratory of Additive Manufacturing for Large Metallic Components (NELAM), Beihang University, Beijing
The additive manufacturing based on the rapid solidification layer-wise deposition principles is well-recognized as a revolutionary manufacturing technology to make high-performance large critical titanium aerospace structural components having unique advantages over conventional manufacturing processes. In this presentation, the technological and economic advantages of rapid solidification deposition-based additive manufacturing of high-performance large titanium critical components were briefly overviewed. The scientific and technological challenges hindering the technology from development and industrial applications were reviewed. Progresses on basic research on laser/metal interaction behaviors, melt-pool metallurgical thermodynamics and kinetics, forming mechanisms and mechanical behaviors of metallurgical defects, rapid solidification and grain morphological selection behaviors, cyclic solid-state phase transformation kinetics and post-AM heat-treatment microstructure evolution behaviors, non-linear thermal history/thermal stress coupling behaviors, etc. were reported during the layer-upon-layer melting deposition/rapid solidification materials processing process. Recent industrial applications of laser additive manufactured titanium components as critical large aerospace structural components were reported. The future impacts and development potentials of the technology for manufacturing large or super-large, complex or super-complex high-performance titanium critical structures are prospected.
Dr. Huaming Wang, academician of the Chinese Academy of Engineering and expert of metal additive manufacturing, is a professor of materials processing and manufacturing in the School of Materials Science and Engineering of Beihang University (BUAA) since 1995. He is the founder and director of the National Engineering Laboratory of Additive Manufacturing for Large Metallic Components (NELAM-LMC) and the National Research and Application Center of Laser Additive Manufacturing for Defense Industries (NRAC-LAMDI).
He received his Bachelor’s degree on Foundry Technology from Sichuan Institute of Technology in 1983, Master’s degree on Mechanical Engineering form Xian Jiaotong University in 1986 and Ph.D on Mining Mechanical Engineering form China University of Mining and Technology (Beijing) in 1989. He conducted his post-doctorate research on Rapid Solidification Laser Materials Processing and Unidirectional Solidification Processing of Single-Crystal Ni-Base Superalloy in the Institute of Metal Research of the Chinese Academy of Sciences in 1989-1992. Prof. Wang was granted a Humboldt Research Fellowship by the Alexander von Humboldt Foundation in 1992 and complted his research on Laser Surface Engineering in the Institute of Metals Science and Technology, University of Erlangen-Nurnberg, Germany in 1992-1994.
He has over 30 years’ research experience on rapid solidification materials processing and manufacturing and is a leading expert of Laser Additive Manufacturing for Large Metallic Components and Laser Cladding for Advanced Multi-functional Tribological Coatings and published over 200 referred papers in international journals. He was granted the First Grade Award of the National Technology Invention Award in 2012 owing to his pioneering achievements on laser additive manufacturing of large titanium aircraft structural components. He won the First Grade Award of the Natural Science Award of the Ministry of Education in 2014 owing to his innovative basic research on tribological behaviors of laser clad multi-components transition metal silicides coatings wear resistant coatings. Prof. Wang was awarded the “National May 1st Labor Medal” in 2005, the Aeronautical Golden Medal in 2013 and was elected as an Academician of the Chinese Academy of Engineering in 2015.
Titanium Applications in Shipbuilding and Other Engineering Applications
A.S. Oryshchenko, D.Eng.1, V.P. Leonov, D.Eng.1, V.I. Mikhailov, D.Eng.1, P.A. Kuznetsov, D.Eng.1, A.V. Alexandrov, PhD2
1- NRC “Kurchatov Institute” – CRISM “Prometey”, St. Petersburg, 191015, 49 Shpalernaya St.
2 – Interstate Association Titan, Moscow, 121596, 16/6 Govorova St.
The paper considers the issues of industrial titanium applications, except for aerospace, biomedical and healthcare applications to be presented at other technical sessions. Now, titanium is extensively used in the shipbuilding, nuclear power engineering, oil-and-gas production, chemical, pulp-and-paper and other industries. The quantities of titanium used in the above industries in various countries are different and generally dependent on its consumption in aerospace. In the USA and CIS with advanced aerospace, it makes up over 50%. The predominant titanium structures in shipbuilding and oil-and-gas production are tubing and fittings which are part of different-purpose systems for cooling, sewage water, fire extinguishing, seawater, primary petrochemical treatment, etc. Over the period following the 13th World Conference on Titanium (Ti-2015), these areas have been in progress in Russia. The production of titanium tubes, mainly concentrated in Ukraine before, has been nearly mastered. Research activities aimed at developing a new marine high-strength titanium alloy with yield strength exceeding 1000 MPa were continued for new-generation deep-water hull structures. In nuclear marine engineering titanium applications have practically remained, i.e., steam generators, condensers, heat-exchanging equipment for different purposes. For a higher efficiency to be provided a new alloy with increased heat conductivity characteristics is under development for the tubing of these structures. Work on the development of an alloy for low-power reactor pressure vessels are under way. One of the recent titanium applications which should be noted is its use in structures operating under severe climatic conditions in the Arctic Region. The main restriction in titanium use, especially in civil areas, is its high commercial cost. For this issue to be solved work on the development of low-cost titanium alloys using less labor-intensive technological processes of melting and manufacturing semi-finished products is under way.
Prof. Kuznetcov specialist in the field of amorphous, nanocrystalline and metastable alloys and technologies of creation on their basis of magnetic and electromagnetic shields; amorphous solders alloys on the Ti-Zr and Fe base, for creation of permanent diverse «steel-titanium», «titanium ceramics» connections, etc.; powder materials on the base of titanium, aluminum and iron by method of high-speed mechanical synthesis and universal desintegrator-activated processing; additive technologies of selective laser melting and direct laser deposition of metal powders on the base of stainless steels, titanium and aluminum alloys; functional and gradient coatings on the base of aluminum, nickel and titanium by methods of high-speed heterophase powder transfer; the author of 75 scientific works and 4 engineering developments. The main scientific results of Pavel Kuznetsov are focused on the development of the controlled crystallization from an amorphous condition theory and also forming of structure and properties of bulk metallic materials on the base of steel, titanium and aluminum alloys by selective laser melting of powders. The scientific principles and technological approaches of forming of amorphous and nanocrystalline structure in amorphous soft magnetic alloys and also composite structure in metal additive bulk materials and functional and gradient coatings for achievement of high values of properties, such as: hardness, wear resistance, durability, magnetic permeability, etc. are proposed by him.
Progress in Wrought Processing of Titanium
M.O.Leder, V.A. Kropotov, A.V. Volkov, D. A. Piskunov
VSMPO-AVISMA Corporation, Parkovaya St. 1, Verkhnaya Salda, Sverdlovsk region
Manufacturing of products that are competitive in terms of price and quality is maintained primarily by means of process optimization at all stages of semi-finished products manufacturing: optimization of alloy compositioning; conditions and methods of melting; billet forging, rolling, die forging, machining processes; optimization of stages, scopes and methods of product and process control. Following the example of serial high-strength alloy VST5553, high-temperature alloys VT18U, VT20 and Ti6242, as well as new compositions of alloys based on Ti, it is shown that the process development based upon advantages and disadvantages of a specific alloy and choosing optimal temperature-deformation conditions facilitate the increase of production efficiency on the one hand, and in some cases - achieving brand new condition of the metal
Mikhail O. Leder, Science and Technology Director of VSMPO-AVISMA Corporation. He has over 28 years of experience in titanium industry. He started as ordinary research engineer and was gradually promoted to the position of the Head of Research and Development Center. In the Corporation, he supervises all processes related to the development, implementation and follow-up of melting, forging, heat treating and machining practices employed during production of ingots, billets, slabs, bars, plates, sheets, tubes, rings, die forgings from a variety of titanium alloys, ranging from CP titanium to high strength near beta alloys and intermetallics.
Innovative Aerospace and Space Structures made by Additive Manufacturing of Titanium Alloys and Titanium Aluminides
C. Leyens1,2, F. Brückner2,3, E. López2, A. Seidel2, M. Riede2 and A. Marquardt1,2
1 TU Dresden, Institute of Materials Science, Germany
2 Fraunhofer Institute for Material and Beam Technology IWS, Dresden, Germany
3 Luleå University of Technology, Sweden
Additive manufacturing of metals is currently paving its way into industrial applications at high pace. While in medical applications there is already a widespread use of AM for customized solutions, the strongest innovation boost in AM is coming from aviation industry, followed by the energy sector, automotive industry, space and toolmaking industry. The focus of this keynote lecture is on aerospace and space applications that have recently attracted major attention, some of the already being in series production.
Using powder bed-based and nozzle-based (wire and powder) AM processes a large variety of customized solutions is feasible, ranging from micrometer-size parts with filigree features to the meter scale of large-size components. With regards to the processing requirements either high accuracy or high productivity can be achieved, whereas a combination is difficult. Among others, examples of industrialized solutions of micro-AM structures for aeroengine use will be given as well as a demonstrator component for space applications with a total diameter of 3 meters.
The presentation will highlight recent developments in AM related to different processes, titanium alloys, titanium aluminides and part sizes/geometries. Unlike any other manufacturing technology, AM of high quality parts requires an in-depth understanding of the close relationship between the AM process, the material and the resulting component properties. As a matter of fact, customized hardware, online diagnostics and control systems are required for robust processing of AM parts. Moreover, the effects of defects on part quality must be studied in detail. Some of the results presented are derived from a 80 Mio. Euro research project on AM, initiated and coordinated by the presenting author.
Born in 1967, Dr. Christoph Leyens studied physical metallurgy and materials technology at RWTH Aachen, Germany, where he earned his diploma in 1993 and his Ph.D. in 1997. He is currently a full professor for materials science at TU Dresden, Germany, director of the Fraunhofer Institute of Materials and Beam Technology IWS, Dresden, Germany, and an adjunct professor at RMIT University, Melbourne, Australia. Dr. Leyens has covered a wide range of research topics with a focus on high temperature and light weight materials, functional materials, laser processing, surface technology, coatings and additive manufacturing. He has published more than 200 papers, seven books and holds eleven patents. Dr. Leyens is initiator and coordinator the R&D project »AGENT-3D«, Europe’s largest single project on AM. Out of a total of 120 partners, the consortium comprises more than 100 companies, aiming at the industrial implementation of AM as an enabling technology for advanced manufacturing.
Titanium Aluminides – Status of the Production of Ingots, Semi-Finished Products and Powders
Volker Güther and Melissa Allen
GfE Metalle und Materialien GmbH, Nuremberg, Germany
Low Pressure Turbine blades made of TiAl alloys are successfully used in aircraft engines for regular commercial service for more than eight years. Due to the strongly increasing number of aircraft engines, particularly for powering the B737max and the A320neo, the total need for TiAl materials and semi-finished products has been increased by approximately 15 times compared to 2012. As a consequence, TiAl materials production technologies was adjusted to both small sized semi-finished products and larger volumes.
The vast majority of TiAl is being produced via Vacuum Arc Remelting (VAR) and subsequent homogeneization in a VAR Skull Melter followed by centrifugal casting in permanent moulds. Larger production volumes generated a reasonable amount of valuable revert which can be directly converted into semi-finished products by remelting the revert in an Induction Skull Melter (ISM) followed by the approved centrifugal casting technology of the VAR production line. Industrial TiAl recycling was a key for decreasing production costs.
Both, the “virgin” production route and the “recycling” production route result in technically indistinguishable semi-finished products with low impurity level and outstanding homogeneity. Such products can also be used as feed stocks for gas atomization in order to provide spherically shaped powders for Additive Manufacturing based on powder bed fusion technologies.
The presentation gives an overview on the metallurgical technologies for the production of TiAl ingots, semi-finished products and powders. AMG Titanium Alloys and Coatings operates a well balanced set of VAR furnaces, VAR Skull Melters, Induction Skull Melters and EIGA Gas Atomizers for the production of Titanium Aluminides in order to strengthen its position as the technology and market leader in this materials segment.
Volker Güther is the Head of R&D of the Business Unit Titanium Aluminides of AMG Titanium Alloys and Coatings (legally GfE Metalle und Materialien GmbH, Nuremberg, Germany). After graduation in solid state physics in 1983, he started his industrial career in the R&D on powder metallurgy of high melting refractory metals. In 1992 he joint GfE as the R&D Manager. His work is focused on the metallurgy of specialty alloys and intermetallic materials. The achievements on the development of metal hydrides for hydrogen storage applications have been recognized by the Paul-Grünfeld-Award in 2004. In 2015 he received the Intermetallics Award for his substantial contributions particularly in the industrialization of manufacturing technologies for Titanium Aluminides.
Application of Titanium and its Alloys for Automobile Parts
Kazuhiro Takahashi, Kenichi Mori, Hidenori Takebe
Steel Research Laboratories, Nippon Steel & Sumitomo Metal Corporation
Titanium and its alloys have been applied to motorcycles and automobiles in order to reduce weight of their component parts. In recent years, titanium exhaust systems such as muffler, engine valves and connecting rods are widely applied mainly in sports type or large motorcycles. In addition to Ti-6Al-4V, Ti-Al-Fe alloys utilized Fe as inexpensive and common alloying element are used in engine valves and connecting rods. In exhaust systems such as mufflers, at first, commercially pure titanium Gr.2 sheets have been mainly used because of their high cold formability. Furthermore, several titanium alloys to which Cu, Al, Si and Nb are added have been actively developed in order to improve strength and creep properties, oxidation resistance and so on as service temperature becomes higher. Also, due to the development of utilization processing technologies, the same methods and process used in steel parts were applied to titanium ones, and then application of titanium expanded to fracture-split connecting rods and fuel tank. Newly, titanium foil has been adopted as a separator of PEFC used in fuel cell vehicles from the viewpoint of excellent corrosion resistance and cold formability. As mentioned above, in this presentation, we will review technical contents of titanium products and parts developed for motorcycles and automobiles.
Dr. Kazuhiro Takahashi is a chief researcher in the Steel Research Laboratories of Nippon Steel & Sumitomo Metal Corporation. He obtained M.S. in Science and Engineering from Tokyo University of Science graduate school in 1991, and a PhD in Engineering from Kanazawa University in 2016. He has been carried out research and development on titanium and its applications in Nippon Steel & Sumitomo Metal Corporation since 1991. His current research interests include microstructure control, surface modification and application technologies for automobile parts and architectural material and so on in titanium and titanium alloys.
Recent Studies and Developments Concerning Titanium Biomaterials
Department of Chemistry and Materials Engineering, Kansai University
Titanium and its alloys have a high specific strength, excellent corrosion resistance, and good biocompatibility. Therefore, these materials are often used for the fabrication of artificial bones and joints, in addition to their applications in dental surgery. There has recently been a great deal of interest in beta titanium alloys, which possess a lower Young’s modulus than alloys such as Ti-6Al-4V alpha-beta alloys. This has led to the development of titanium-niobium-tantalum and zirconium-based materials such as Ti-29Nb-13Ta-4.6Zr, which exhibit a low Young’s modulus, good biocompatibility and superior mechanical properties. Other active areas of investigation include surface modifications such as alkaline heat treatment, wet processing, and electrochemical treatment for the formation of hydroxyapatite (HAp), which is an important biocompatible surface coating. Other approaches involve direct formation of HAp using methods such as plasma spraying, ion plating, RF magnetron sputtering, pulse laser deposition such as dry processing, and ion-beam dynamic mixing. Indirect methods include calcium ion implantation and calcium ion mixing. In the present study, we focus on the topics of additive manufacturing, bone orientation, and the development of zirconium alloys. Additive manufacturing refers to 3-dimensional printing, wherein metal powder is built up using a layer-by-layer process to fabricate products without the need for a mold. This has attracted a great deal of attention in many fields, particularly in the fabrication of porous biological implants with a low Young’s modulus. Also, it has recently been recognized that in addition to bone mineral density, the crystalline orientation of biological apatite (BAp) is important for bone regeneration. In living bones, the c-axis in Bap tends to be aligned along the principal stress direction. Finally, magnetic resonance imaging has become a powerful diagnostic tool in orthopedics. However, problems arise due to the presence of metallic implants in the body, because they can become magnetized under the intense magnetic field, which can lead to image artifacts and inaccurate diagnoses. This problem can be mitigated by the use of Zr alloys, whose magnetic susceptibility is lower than that for Ti-6Al-4V, Co-Cr-Mo alloys, or SUS 316L stainless steel.
Masahiko Ikeda is a professor in the Department of Chemistry and Materials Engineering, Kansai University. He obtained a Masters in Engineering from Kansai University graduate school in 1981, and a PhD in Engineering in 1991. From 1979 to 1986, he was employed at a private company, and carried out research and development. In 1986, he moved to Kansai University as a Research Associate. From 1986 to 2002, he was a Research Associate, a lecturer and then an Associate Professor. In 1995, he was an Academic Visitor in the Materials Department at Imperial College, London. His research interests have been in the area of phase transformations in beta titanium alloys. Since 2002, he has been a Professor at Kansai University. His recent research is focused on the development of cost-efficient beta titanium alloys for health care and medical applications.
Advances and Breakthroughs in Titanium forgings for critical structural parts
R&D Director ERAMET Alloys
Following several decades of experience in titanium close die forging of structural parts, Aubert&Duval has implemented during the last ten years a fully integrated manufacturing process in order to propose cost optimizations of forgings to its customers. Assuming the high level of the properties and reliability of titanium forgings, strong drivers of research and development for forgings are the pressure on cost, the buy to fly reduction and the life cycle. This presentation discusses the potential of optimizations to address these challenges. The following levers of improvement are presented. The first way to concretely answer the question of the cost and of the life cycle is the recycling of manufacturing scrap and end-of-life products, using the concept of circular economy and implementing a short loop from end user to melters. This is a considerable opportunity to mitigate the risks related to the supply of primary material and to the erratic fluctuations of raw material prices. The second step to optimize both the added value and the material consumption consists in adapting accurately the melting and ingot conversion processes to the actual needs of the application and the subsequent transformation processes. These adaptations can bring significant savings to the cost of billets. Considering the close die forging step, the use of the concept of Design for Manufacturing, or Design for forging in the present case, has also a great potential to optimize the cost and the functions of the forgings. This requires a close cooperation of engineering teams to better manage the constraints of design, integration of functions and manufacturing process. Near Net Shape Forging of titanium, using high temperature close die forging, is also an opportunity to make a breakthrough in terms of buy to fly and to integrate more complex functions in forged parts. In addition to all these improvements, the use of high-power hydraulic presses is a key element to take full advantage of them and to manufacture large critical parts with more functions. All together these levers could provide drastic cost reductions, discussed in this paper, and a considerable reduction in the environmental impact, keeping the intrinsic advantages of titanium forgings in terms of metallurgical integrity, residual stresses and properties. The implementation of these improvements will require continuous efforts of development from the whole titanium supply chain, and collaboration between integrated titanium forgings suppliers and the OEMs.
Research and Development ERAMET Alloys & Aubert&Duval, since 2013 Elaboration Director, Aubert & Duval (2005 - 2013) In charge of production facilities: Steel shops, VIM and remelting facilities for special steels and superalloys
Design and development of strain-transformable titanium alloys for improved resistance/ductility trade-off
Materials Science in Chimie Paristech
Owing to their high specific properties, titanium alloys have been, for a long time, highly competitive materials in fields such as aerospace industry. Among these alloys, research efforts were recently dedicated to design approaches for improved strength/ductility trade off. Guided by electronic parameters calculations, new “strain-transformable” Ti alloys have been developed and both single phase and dual phase materials have been optimized. Thanks to the synergy between stress induced martensitic transformation (TRIP effect), intense mechanical twinning (TWIP effect) and dislocations glide, these new materials display a combination of high fracture strength (up to 1400MPa), extra-large work-hardening and superior ductility (up to 45% at fracture). In this talk, design strategy and microstructural optimization approaches of this new family of alloys will be discussed regarding the occurrence, chronology and synergy of the different deformation mechanisms. From this work, future directions towards both compositional and microstructural optimization pathways will be drawn and discussed.
Frédéric Prima is Professor of Materials Science in Chimie Paristech, Paris, Fr. He graduated from Institut National des Sciences Appliquées (INSA Lyon) in 1995 and obtained his PhD in Materials Science in INSA Rennes, in 2000. He worked as a postdoctoral fellow in Oxford University Materials Department (UK) from 2000 to 2003. The work of his research group in mainly dedicated to the investigation of phase transformations and microstructures/properties relationships in titanium-based alloys. Recently, his recent research has been focused on the design strategies and the development of new high-performance titanium alloys for aerospace applications, in close collaboration with Timet/PCC and SAFRAN. His group works, as well, in the development of beta alloys for biomedical applications. He has published over 100 journal articles, 5 patents and participated to more than 120 national and international conferences (16 as invited speaker).
Environmental effects on fatigue and SCC
Imperial College London
Dwell fatigue, stress corrosion cracking and interstitial contamination are three fatigue-related issues that have caused significant concern in recent years. Cold dwell fatigue is a low-load fatigue cracking phenomenon associated with load holds at near-ambient temperatures. We have been able to elucidate that the ‘bad neighbour’ model of dwell fatigue crack nucleation is broadly correct, and to understand why this is only an issue at low temperatures and holds in load. Microstructures that lead to dwell fatigue at low load can be created that reproduce spin test experience, which otherwise cannot be recreated by specimen testing due to stressed volume effects. Interstitial contamination is a persistent issue in Ti alloys, as these are fabricated and used in service at elevated temperatures. These issues both concern manufacture and service performance. Questions related to the effects of interstitial O and N on fatigue behaviour will be explored. Stress corrosion cracking is another issue which has been of recurrent concern to users of titanium alloys for over 50 years; some case studies of recent service experience will be reviewed. These problems can be avoided by careful choice of the operating envelope, but the underlying issue of hydrogen embrittlement has until recently been relatively impervious to study, because hydrogen cannot be directly detected in the electron microscope. Recent developments with deuteration and cryo-FIB preparation are leading to success in FIB-SIMS and atom probe tomography, and this is allowing the elucidation of the mechanisms of both the corrosion step and hydrogen embrittlement.
David Dye is a Professor of Metallurgy in the Department of Materials at Imperial College, London, UK. He mostly works on the fatigue mechanisms, micromechanics and design of titanium and nickel/cobalt superalloys. In Ti he collaborates with Rolls-Royce and Timet/PCC, working on alloy and microstructure design and on the micromechanics of fatigue, particularly as it pertains to in-service performance. Prior to moving to Imperial in 2003, he worked at the neutron spectroscopy facility in Chalk River, Canada. His undergraduate degree and PhD were from Cambridge University, on the weldability of nickel-base superalloys. He has received a number of awards for his work and has published over 100 journal articles. He was an EPSRC Leadership Fellow, 2010-15 and is presently a Royal Society Industry Fellow.
Exploitation of field assisted sintering technology (FAST) for titanium alloys
Department of Materials Science and Engineering, The University of Sheffield
Spark plasma sintering (SPS) or field assisted sintering technology (FAST) is increasingly being applied to engineering alloys and metal-based composites powders and particulates including titanium alloys. FAST is currently being used as (1) a rapid and cost-effective process to consolidate powders of new alloy compositions, in order to investigate phase transformations and deformation mechanisms. This is largely conducted on the small scale by research institutes and universities. However increasingly, (2) FAST is being used to produce aerospace and automotive demonstrator parts such as rocker arms, blades and brake calipers from titanium-based powders, as an alternative to hot isostatic pressing or conventional melt-wrought processing.
FAST has been demonstrated to be an effective intermediate solid-state process for consolidating powder into pre-forged billets from a range of feedstocks including recycled material. Processes such as FAST-forge and FAST-DB have been developed to be hybrid processes that can produce affordable titanium components with forged properties in two steps.
In this paper the current status, the emerging developments and challenges of FAST for titanium-based powders and particulates are presented.
Nicholas Weston is a Research Associate in the Department of Materials Science and Engineering at the University of Sheffield. He obtained an MEng in Aerospace Engineering in 2011 and a PhD in Metallurgy in 2017, both from the University of Sheffield. He became a Research Associate in 2016 working as part of the Sheffield Titanium Alloy Research group. His principal research interest is the solid-state downstream processing of titanium alloy powders and particulates, to produce low-cost titanium alloy components. Research undertaken during his PhD developed FAST-forge; a cost‑effective processing route that can turn titanium alloy powder feedstock into a near net shape component with forged properties in two steps. The first step uses FAST to produce a shaped preform billet, which can then be forged in one operation to near net shape in the second step. His post‑doctoral focus has involved two collaborative research and development projects part-funded by InnovateUK, where he has worked with industrial partners to further develop the FAST-forge process for aerospace and automotive applications.
A New Process for Production of Low Cost Ti Powder and the Sintering of Ti alloy Powder to Achieve Wrought-Like Microstructure and Mechanical Properties
Z. Zak Fang
University of Utah
The high cost of titanium has challenged the Ti industry and is a major focus of the research community globally for several decades. Although the powder metallurgy (PM) of Ti has shown promise to be a low cost approach, it has not gained significant market acceptance because the performance-to-cost ratios of PM Ti cannot compete with that of the wrought alloys. In order to compete, the cost of Ti and Ti alloy powders must be drastically reduced and the mechanical properties of sintering Ti alloys must be drastically improved. This presentation introduces both a low cost powder production process and a sintering technology that can produce Ti-6Al-4V with wrought like microstructure and mechanical properties. The strong affinity of titanium to oxygen makes the conventional Ti metal production by either the Kroll or the Hunter process energy-intensive and costly. A new approach is designed to prepare high-purity Ti metal powder from commercial purified TiO2. Pure TiO2 is subjected to Mg reduction, followed by a de-oxygenation process using Mg. Both the Mg reduction and the deoxygenation processes are carried out in hydrogen atmosphere. It has been shown that hydrogen can destabilize Ti-O system and enable Mg to reduce oxygen content in Ti to very low levels. This is a fundamental breakthrough that makes the direction production of Ti metal and alloy from TiO2 by magnesium reduction possible. This talk will present elaborate the design of the hydrogen assisted Mg reduction process (HAMR) and the results that demonstrate HAMR process can produce low oxygen Ti metal powder with oxygen content as low as a few hundred ppm. HAMR process can be used produce both low oxygen CP-Ti and Ti alloy powders. The second part of this presentation introduces a new approach for sintering Ti alloy powders. A hydrogen sintering and phase transformation process is designed to produce Ti-6Al-4V alloy with wrought-like microstructure and mechanical properties via simple press-&-sitnering and heat treatment. Titanium powder is typically sintered in high vacuum to achieve high density and low oxygen. Sintered materials usually have coarse grain size and lamellar structure in the case of sintered Ti-6Al-4V alloys. In this work, a novel process is designed to take advantage of both the higher sintered density for using TiH2 as raw material and the phase transformation induced by hydrogen that produces fine grain sizes. The process can produce near-fully dense (>99%Ti-6Al-4V) Ti materials with very fine grain size (~<1.0µm) in as-sintered state. The refined microstructure has advantages over coarse lamellar structure of conventional sintered Ti materials from the stand point of mechanical properties. The as-sintered Ti-6Al-4V can also be heat treated to obtain wrought-like equi-axial globular or bi-model microstructure and mechanical properties. This presents a new opportunity for low cost manufacturing of PM Ti materials with both static and fatigue mechanical properties equivalent to that of wrought Ti materials. This presentation will show the results of microstructure and mechanical properties of as-sintered, heat treated, and those with an additional pore closing treatment. The results demonstrate that PM Ti-6Al-4V can be made to have equivalent mechanical properties, including fatigue strength, to that of wrought Ti.
• Professor of Metallurgical Engineering at the University of Utah since 2002 • He worked in the industry for ten years prior to coming back to academia • Obtained his Ph.D degree from the University of Alabama at Birmingham, • MS and BS from the University of Science and Technology Beijing • Expertise in metallic materials, metallurgy, and manufacturing including extractive metallurgy of Ti, sintering and mechanical properties of Ti, and low-cost production of Ti metal powders. • He is the author or co-author of over 360 technical publications • He is the inventor or co-inventor of 50 US patents • Fellow of the National Academy of Inventors and Fellow of American Society of Metals
Opportunities and Challenges for the Industrial Titanium Market
Manager, Business Development, VSMPO Tirus US
The industrial titanium market is the second largest segment of the titanium industry and currently comprises less than 20 % of the overall titanium market. In spite of a more than 50 year history of successful application in corrosive environments myths about availability, fabrication, pricing and corrosion resistance are still part of the conversation and culture with many potential customers. The author will discuss these issues and present comparisons with other common materials of construction to demonstrate the business case for titanium. With seawater/brackish water being the most common corrosive environment where titanium is applied examples of current applications will be presented. By highlighting the characteristics of titanium that led to the material choice in these examples potential new applications can be identified. These examples will come from application on offshore platforms, LNG liquefaction plants, power generation, desalination and petroleum refining operations. Against the backdrop of the application analysis the author will also explore regulatory, market influences and new technology impacting the industrial titanium market segment. Drawing on statistics from the Titanium Association and other resources a projection for industrial growth will be presented for the next decade.
Hershel Robert (Rob) Henson began his career working in corrosion research at Teledyne Wah Chang under the direction of Dr. Te Lin Yau in the early 1980s. Henson holds a Bachelor of Science Degree in Business Management from Linfield College and has authored and co-authored many publications. Henson led the development of Ti-45Nb as an ignition resistant titanium alloy for gold pressure oxidation application and was a co-inventor of titanium alloy Ti-35Zr-10Nb. Henson continues to work in business development and sales of titanium products for industrial application. He is currently Chairman of the International Titanium Association Industrial Applications Committee and a member of NACE active in the TEG 120X Reactive Metal Forum.
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