Sponsored by: SMD Titanium Committee and TMS/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
Tuesday, PM Room: B5-6
February 6, 1996 Location: Anaheim Convention Center
Session Chairpersons: P.L. Martin, Rockwell Science Center, 1049 Camino Dos Rios, Thousand Oaks, CA 91360; J.C. Fanning, Henderson Technical Laboratory, Timet, P.O. Box 2128, Henderson, NV 89015
2:00 pm Invited
COLD EXTRUSION OF TITANIUM ALLOYS AND TITANIUM MMCs: Hans W. Wagener, Joachim Wolf, Metal Forming Laboratory, University of Kassel, 34109 Kassel, Germany
The following metals were tested by the basic cold extrusion processes, forward bar extrusion, forward tube extrusion, and backward cup extrusion: pure titanium, Ti-6Al-4V, Ti-13Al-11Cr-3Al, Ti-3Al-8V-6Cr-4Mo-4Zr (Betal-C) and two MMCs, Ti - 99.9 + 10% TiC and Ti-6Al-4V + 10% TiC. The manufacturing techniques, tooling, and the optimum coating and lubrication systems for cold extrusion of these metals are described. Deformation force vs. punch travel digrams are plotted. The values of the coefficient of friction acting between material and tool surface are determined experimentally and by computer simulation. In the case of Ti-6Al-4V the high strength combined with the small ductility makes cold forming problematic. The same problem exists for the MMCs. The fibrous and particle strengthening act like material seperation in the matrix. The MMCs are considered being brittle materials. To increase the workability the state of stress in the forming zone is shiften more to the compressive side by applying a counter pressure.
COLD WORKING OF Ti 13Nb-13Zr: C.M. Bugle, E.W. Robare, Dynamet Inc., 195 Museum Road, Washington, PA 15301; K.P. Daigle, J.A. Davidson, Smith and Nephew TransTech, 1450 Brooks Road, Memphis, TN 38116
Ti-13Nb-13Zr (Ti-13-13`) is a new titanium alloy which has a unique combination of properties that may make it an attractive choice for a variety of applications. Originally developed for use in biomedical implants, this alloy combines a low elastic modulus, high strength, excellent hot and cold workability, superior corrosion resistance, and the ability to be surface hardened to improve wear properties. Research on this age-hardenable alloy has shown that the mechanical properties can be controlled over a significant range through hot working, heat treatment and cold working. The elastic modulus of Ti-13-13 can be varied between approximately 6 and 12 Msi, and strengths as high as 190 ksi have been achieved. Some typical combinations of properties for various material forms and conditions will be presented. Further, the material does not seem to exhibit some of the typical processing difficulties encountered in some age-hardenable beta-Ti alloys. For example, in wire drawing trials, Ti-13-13 yielded exceptionally good surface finish in the "as-drawn" condition with over 85% cold work. Some examples of processing behavior will be discussed.
TITANIUM ALUMINIDE FOIL PROCESSING: C. C. Wojcik, Teledyne Wah Chang, P. O. Box 460, Albany, Or 97321; R. Roessler, R. Zordan, Allison Engine Co., P. O. Box 420, S. C. WO5, Indianapolis, In 46206-0420
Orthorhombic titanium aluminides based on the Ti2AlNb composition are of interest for high temperature composite applications because of their excellent strength and compatibility with SiC fibers. The performance improvements attainable with this new type of titanium alloy will only be realized if orthorhombic alloy foil and SiC fibers can be produced economically. Fabrication of these alloys into thin (i.e., 0.10 mm thick) foil presents some difficult problems. We will report on our experience fabricating Ti-22Al-26Nb into foil. The effects of hot working and annealing temperature have profound influences on microstructure and properties. Additionally, this alloy is sensitive to cooling rate which may be used to quench in metastable structures that are more workable than ordered orthorhombic or ordered alpha phases. The effects of heat treatment on microstructure, hardness and cold workability will be discussed.
ABRASIVE WATER JET CUTTING OF TITANIUM VENT SCREENS FOR THE F-22 ADVANCED TACTICAL FIGHTER: H.R. Phelps, Lockheed Aeronautical Systems Co., Marietta, Georgia
The F-22 Advanced Tactical Fighter (ATF) has several titanium vent screens. These screens will be fabricated using abrasive water jet (AWJ) cutting to produce up to 27,000 densely packed, rhombus shaped holes. This paper will compare the potential methods of producing these screens, why AWJ was selected as the primary method, and issues associated with aerospace applications.
CRYOGENIC MACHINING OF TITANIUM 6-4 ALLOY: Shane Y. Hong, Dept. of Mechanical & Materials Engineering, Wright State University, Dayton, OH 45435
Due to its abrasiveness, low thermal conductivity, and chemical reactivity, titanium has been long classified as a difficult-to-machine material. Cutting tool wears rapidly and tool life is extremely short. For this the cutting speed of 200 to 300 feet per minute is used for machining titanium in the industry, compared to a spee 10 times faster used in machining steels. The slow cutting process and the rapid tool wear makes the productivity very low and the production cost very high. This paper presents a new cutting process that uses liquid nitrogen to cool the high temperature usually generated in conventional machining. It enables higher speed cutting and better the productivity. On the other side, the production cost has been much reduced. In addition, this is an environmental safe manufacturing process.
3:50 pm BREAK
CRYOGENIC MILLING OF TITANIUM 6-4 ALLOY: Shane Y. Hong, Dept. of Mechanical & Materials Engineering, Wright State University, Dayton, OH 45435
As part of effort of environmental conscious manufacturing, milling of titanium is one of the needed areas for the researcher to focus on. Due to the extremely short tool life in dry cutting of titanium alloys, cutting fluid is necessary in the milling process to remove the heat generated in the cutting process. But conventional coolant is not environment friendly, and costs at least double the purchasing price to dump it. This paper introduces a cryogenic milling process which is essentially a dry cutting process. Liquid nitrogen is injected to the milling tool cutting tips through a rotary distribution ring. It evaporates at the cutting tool tips and absorbs the high heat generated in the cutting process. No residue is left in the work piece and the chips. The effects of this neat and clean process include longer tool life and better work quality. This new cryogenic milling system features a low nitrogen consumption so that the production cost is competitive compared to conventional milling process.
HYDROGEN INFLUENCE ON MACHINING OF TITANIUM ALLOYS: B. A. Kolachev, Y. B. Egorova, Moscow State Aviation Technological University after Tsiolkovsky, Petrovka 27, 103767 Moscow K-31, Russia; V. D. Talaev, Scientific-Production Association "AVITOM", Ulanskyi pereulok 16, 101000 Moscow, Russia
Titanium alloys are difficult to machine. The working hours of machining of titanium alloys is 7-8 times more than for aluminum alloys and 4-5 times more than for carbon steels. The machinability of titanium alloys may be improved essentially by reversible hydrogen alloying. In this paper detailed investigations of hydrogen influence on machining of titanium alloys have been carried out. It has been shown that hydrogen alloying of titanium alloys leads to significant increasing of tool life (2-10 times). The specific tool life has a maximum value at hydrogen concentration 0.1-0.5 wt% depending on composition of alloys. The favourable influence of hydrogen on machining of titanium alloys is diminished with the growth of cutting rates. Hydrogen alloying causes changes of chip-forming: chip become fragile. The improvement of machinability of titanium alloys by hydrogen alloying is due to microstructure refinement, decrease of metal flow stresses and impact ductility, increase of thermal conductivity and changes in tool wear characteristics. When machining titanium alloys with iniatial hydrogen content (0.003-0.005%wt) wear of cutter occurs on the front face as well as on the back one. The wear on the back face of cutter takes place mainly at machining of hydrogenated metal. The machined hydrogenated details should be vacuum annealed to reduce hydrogen content in a metal to safe level which is not followed by hydroden embrittlement during operation.
TEMPERATURE DISTRIBUTION IN TITANIUM MACHINING BY FINITE ELEMENT ANALYSIS: Shane Y. Hong, Y. C. Ding, Dept. of Mechanical & Materials Engineering, Wright State University, Dayton, OH 45435
Temperature distribution in the cutting tool and chips will be analyzed
using the finite element method, and will be presented in terms of various
machining parameters, such as feed speed, depth of cut for both dry and
cryogenic machining conditions.
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