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.
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.
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.
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