Sponsored by: SMD Titanium Committee, MDMD Shaping and Forming Committee
Program Organizers: Prof. Isaac Weiss, Prof. Raghavan Srinivasan, Mechanical and Materials Engineering Dept., Wright State University, Dayton, OH 45435; Dr. Paul Bania, Timet Corporation, Timet-Henderson Technical Laboratory, P.O. Box 2128, Henderson, NV 89009; Prof. Daniel Eylon, Graduate Materials Engineering, University of Dayton, Dayton, OH 45409
Thursday, AM Room: B5-6
February 8, 1996 Location: Anaheim Convention Center
Session Chairpersons: G. Welsch, Case Western Reserve University, Cleveland, OH 44106; V.K. Sikka, Oak Ridge National Laboratory, PO Box 2008, Oak Ridge, TN 37831-6083
8:30 am Invited
JOINING OF ADVANCED TITANIUM-BASED MATERIALS - PRESENT CHALLENGES AND APPROACHES: W.A. Baeslack III, College of Engineering, The Ohio State University, Columbus, OH 43210; T.J. Kelly, GE Aircraft Engines, Cincinnati, OH 45215-6301
The effective application of advanced titanium-based materials such as gamma and orthorhombic titanium aluminides, metal-matrix composites and conventional alloys in aerospace and non-aerospace applications will require the development and application of joining processes, procedures, and postweld processing techniques that produce high integrity (i.e. defect free) joints exhibiting acceptable mechanical properties. The inherent metallurgical nature of these materials commonly precludes the application of conventional welding processes and/or procedures currently utilized in the joining of monolithic Ti-6Al-4V, and has required new joining approaches. This presentation will describe current requirements for the joining of several advanced titanium-based materials and approaches utilized by investigators in the USA to meet these challenges. Material/process combinations described will include the high-energy density, friction and diffusion welding of Ti-48Al-2Nb-2Cr gamma titanium aluminide, the resistance and conventional diffusion welding and diffusion brazing of monolithic (neat) and SiC-reinforced Ti-20Al-23Nb orthorhombic titanium aluminide, the gas tungsten-arc and electron-beam welding of Alloy C and the gas tungsten-arc and laser welding of Ti-6-22-22Si. The dissimilar joining of these materials to titanium and ferrous-based materials using principally solid-state joining processes will also be presented. Approaches to joining process selection and process optimization via the development and application of physical and welding metallurgy principles for each of these materials will be described.
JOINING OF DISSIMILAR TITANIUM ALLOYS FOR DUAL ALLOY COMPRESSOR STAGE CONSTRUCTION: Prabir Bhowal, James A. Hall, Allied Signal Engines, Phoenix, AZ 85072
The call for increased stage performance in the high pressure compressor of advanced gas turbine engines has led to increasing demands on the strength and temperature capabilities of the materials from which the disks in these rotating stages are constructed. The use of titanium alloys in these applications is met with a challenge that alloys and microstructures idealized for the high strength requirements of the bore material are divergent with the alloys and microstructures suitable for the higher temperature creep requirements at the outer, or rim regions of a disk or impeller. The use of dual alloy impeller construction is one possible solution to the problem. Allied Signal work on the development of effective joining methods for dissimilar titanium alloys is discussed. Demonstration of effective joining methods for conventional alloy pairs in impeller configuration will be presented. Also, work in progress, on the joining of advanced alloy pairs incorporating Ti3Al base [[alpha]]2, Ti2AlNb base [[sigma]](orthorhombic) and TiAl base [[gamma]](gamma) combinations, will be discussed.
A STUDY OF DIFFUSION BRAZING OF DISSIMILAR TITANIUM ALLOYS: Gopal Das, Carter Barone, Pratt & Whitney, PO Box 109600, West Palm Beach, FL 33410-9600
The diffusion brazing of dissimilar titanium alloys-a beta titanium alloy (trade name Alloy C) and a gamma titanium aluminide (trade name XD) was assessed using commercially available Ticuni filler metal. The effect of process parameters such as temperature, time as well as initial filler metal interlayer thickness on the microstructure of brazements have been evaluated. Post-braze heat treatments were employed to achieve homogeneity across the brazements both in terms of microstructure and chemical composition. Phase identification including composition gradient across the brazements for as-brazed and post-braze heat treated samples were achieved by TEM and EMPA studies. Microhardness technique was used to study the effects of process parameters and post-braze heat treatments on the mechanical properties of the brazements. In addition. three-point bend strength and tensile strength of brazed samples were determined at RT and 1200deg.F. Attempts will be made to establish microstructure/property relationships and the results will be discussed in terms of present understanding of diffusion brazing of dissimilar materials.
INFRARED TRANSIENT LIQUID-PHASE JOINING OF SCS-6/ß21S TITANIUM MATRIX COMPOSITE: C.A. Blue, V.K. Sikka, Oak Ridge National Laboratory, PO Box 2008, Oak Ridge, TN 37831-6083; R.A. Blue, R.Y. Lin, Department of Materials Science and Engineering, ML 12, University of Cincinnati, Cincinnati, OH 45221
Fiber reinforced titanium matrix composites (TMC) are one of the advanced materials being considered for use in the aerospace industry due to its light weight, high strength, and high modulus. In order to use TMC as structural components with complicated geometry, the successful development of joining techniques which provide strong bonds and do not weaken the base materials being joined is essential. A successful TMC joining method must be developed which will limit the reaction between the matrix and reinforcement during joining. This may be accomplished by minimizing the liquid pool during liquid state processes and minimizing time in the case of solid and liquid-solid state processing. In an effort to minimize processing time in transient-liquid-phase, solid-liquid state, joining of TMC, a rapid infrared joining (RIJ) technique has been developed. The application of the RIJ technique for joining a 16 ply SCS-6/ß21S titanium matrix composite will be discussed.
Ti75 ALLOY AND ITS WELDING BEHAVIOR: Zhao Yongqing, Li Zuochen, Li Changliang, Wu Qingzhi, Northwest Institute for Nonferrous Metal Research, P.O. BOX 51 Xian, China, 710016
In order to meet the requirement for new materials for marine, chemical industry and genetic engineering applications, the Ti75 alloy, a new middle strength, high toughness and corrosion resistant near -[[alpha]] titanium alloy, was designed and developed by NIN. Its main properties are as follows:[[sigma]]b>730MPa, [[sigma]]s>630MPa, d >13%, [[psi]] >30%, [[alpha]]k>600KJ m-2, KJ0.2>100MPa m-1/2 and KIscc>85MPa m1/2.. The alloy used in this experiment was hot rolled commercial plate of 14mm thickness. The results indicated that T75 alloy had good welding behavior. The k value of welding seam changed with increasing distance between melting line and welding seam. In any conditions [[alpha]]k was greater than 500KJ m-2. Tensile properties of welding seam was as follows: [[sigma]]b >= 750MPa, [[sigma]]s >= 650MPa, d >= 10%, [[psi]] > 25%. The microstructure of the weld and fractograph were examined by means of SEM and optical microscopy.
EXPLOSION WELDED TRANSITION JOINTS FOR WELDS BETWEEN TITANIUM AND DISSIMILAR METALS: John G. Banker, Dynamic Materials Corp., Explosive Fabricators Div., 551 Aspen Ridge Drive, Lafayette, CO 80026
Explosion welded transition joints provide a means for making fully welded connections between titanium and dissimilar metals such as aluminums, stainless steels and nickel alloys. The manufacturing process is briefly discussed. Mechanical test data is presented on several metal combinations. Frequently thin interlayers of other metals are employed in the bonding operation to enhance product features, such as strength, toughness or leak tightness. Data on performance of specific interlayer metals is presented. Potential applications for both the aerospace and process industries are reviewed.
TITANIUM/STEEL EXPLOSION BONDED CLAD FOR AUTOCLAVES AND REACTORS: John G. Banker, Dynamic Materials Corp., Explosive Fabricators Div., 551 Aspen Ridge Drive, Lafayette, CO 80026
Titanium provides excellent performance in many highly corrosive process industry environments. Titanium clad steel offers a cost effective means for manufacture of vessels for high pressure and high temperature applications. Explosion bonded titanium clad steel has been used extensively for reliable clad vessel fabrication for nearly 30 years. The explosion bonding process and characteristics of titanium explosion clad are discussed. Titanium clad reactor fabrication methods and experience are reviewed in detail. Specific applications of titanium explosion clad in hydrometallurgical autoclaves are discussed.
LASER WELDING OF TIMETAL LCB ALLOY: I. Weiss, N. Stefansson, M. Saqib, Mechanical and Materials Engineering Dept., Wright State University, Dayton, OH 45435; W.A. Baeslack III, College of Engineering, The Ohio State University, Columbus, OH 43210
Laser welding was used to obtain high integrity welds in Timetal LCB sheet. These welds are characterized by narrow fusion and heat affected zones, as well as finer microstructure. The objective of this paper is to evaluate the laser welding of 0.060 in. LCB sheet in the as-solution treated condition. The effect of heat treatment on weld microstructure and mechanical properties will also be discussed.
BONDING OF PORCELAIN TO TITANIUM COMPONENTS FOR DENTAL RESTORATION: O.R. Monteiro, I. G. Brown, Lawrence Berkeley Laboratory, Berkeley, CA 94720; R.R. Wang, School of Dentistry, Case Western Reserve University, J. Chung and G. Welsch, Materials Science & Engineering, Case Western Reserve University, Cleveland, OH 44106
The bonding of porcelain to titanium components used in dental restorations requires heating to around 1000[[ring]]C. Direct application of porcelain to titanium results in poor adherence and spallation because of a weak interfacial rutile layer. Specimens were coated with thin layers of chromium and silicon using sputter and plasma immersion deposition methods. The purpose of the coatings is prevention of rutile formation. A chromium oxide or silica surface film is to be formed with good adherence to both the substrate and the porcelain overlayer. Results of microstructure and mechanical evaluations of titanium/coating/porcelain specimens will be presented.
MICROSTRUCTURE EVOLUTION IN THE FUSION ZONE OF TI-48AL-2NB-2CR GAMMA TITANIUM ALUMINIDE WELDMENTS: J. S. Lee, W.A. Baeslack III, College of Engineering, The Ohio State University, Columbus, OH 43210;. T.J. Kelly, GE Aircraft Engines, Cincinnati, OH 45215
Achieving acceptable mechanical properties in gamma titanium aluminide weldments requires optimization of the weld fusion zone microstructure. Microstructure evolution in this weld region is complex due to the inherently complex nature of solidification and on-cooling solid-state phase transformations in this alloy system and the potentially wide range of solidification and cooling rates experienced during arc and high-energy density fusion welding processes. This presentation will describe fusion zone solidification and on-cooling solid-state phase transformations for laser welds produced in a series of Ti-(45-49)Al-2Nb-2Cr alloys that experienced fusion zone cooling rates ranging from about 50 to 5000deg.C/s. Effects of aluminum content and weld cooling rate on the fusion zone solidification mode (BCC vs. HCP) and on-cooling solid-state phase transformations will be described. Effects of postweld heat treatment on the modification and normalization of the as-welded fusion zone microstructures will also be presented.
INFRARED TRANSIENT-LIQUID-PHASE JOINING OF GAMMA TITANIUM ALUMINIDE: C.A. Blue, V.K. Sikka, Oak Ridge National Laboratory, PO Box 2008, Oak Ridge, TN 37831-6083
Ordered intermetallic compounds based on aluminides such as Ti3Al, TiAl, and Ni3Al are emerging as attractive materials for high-temperature applications. The actual industrial use of these intermetallic alloys has been slow due to their poor ductility and problems of weld cracking while being joined into a complicated geometry. In this study, the reaction between titanium aluminide and a liquid titanium alloy, 70Ti-15Cu-15Ni in wt%, was investigated in order to reveal the behavior of TiAl during solidification. Issues of concern in this study include: (1) the solidification process of the melt upon termination of heating, and (2) the diffusion of Cu and Ni into the substance during processing. To accurately control the extent of reaction, an innovative rapid infrared joining (RIJ) technique was used. Infrared processing can produce heating rates exceeding 100deg.C/sec up to the processing temperature. The cooling rate is also rapid due to it being a cold wall process. Such rapid rates of processing decreases or eliminates the adverse effects associated with prolonged heating. In this study, experiments were conducted at various heating times in order to investigate to solidified zone microstructure, melt affected zone thickness, and base material microstructure. The system investigated in this study is directly related to joining of gamma titanium aluminide with a titanium brazing alloy. Results show that the joint show strengths as high as 220 MPa can be achieved with minimal effects on the mechanical properties of the gamma titanium aluminide.
THE RELATIONSHIP BETWEEN MICROSTRUCTURE AND CRACKING IN GAMMA TITANIUM ALUMINIDE WELDS: Mary C. Juhas, Edison Welding Institute, 1100 Kinnear Road, Columbus, OH 43212; William A. Baeslack, The Ohio State University, College of Engineering, 2070 Neil Ave., Columbus, OH 43210; Hamish L. Fraser, The Ohio State University, Department of Materials Science and Engineering, 116 W. 19th Avenue, Columbus, OH 43210
Gamma titanium aluminides have recently emerged as strong candidates to
supplant titanium and nickel-base superalloys in high temperature gas turbine
engines. Solid state joining of titanium aluminides is often accompanied by
cracking in the weld heat and deformation zone (HDZ) under certain conditions.
The focus of this work was to determine the relationship between weld HDZ
microstructures and cracking behavior. Preliminary pilot welds using the
continuous drive friction process were first prepared in order to characterize
the location and nature of cracking. The thermal profiles across the joint
interface during welding were then measured by thermocoupling weld samples.
The temperature excursions derived from the thermocoupled weld were used in
combination with the parameters total plastic strain and strain rate to
simulate various regions of the HDZ. The corresponding microstructures were
evaluated for relative cracking behavior and deformation features using optical
metallography and transmission electron microscopy (TEM). In addition to the
HDZ simulations, friction welded samples were tensile tested at ambient and
elevated (700deg.C) temperatures and compared with similarly tested base
material. The fracture surfaces and underlying deformation microstructures were
characterized as a function of temperature and deformation level. It was
observed that the HDZ cracking occurred along gamma grain boundaries and lath
boundaries as observed in the elevated temperature tensile tests. Ambient
temperature fractures were transgranular in nature.
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