Over the past two years the titanium metal industry has been a focus for dynamic change and rapid growth. Driven by the large number of defense and commercial aerospace programs brought on by global economic growth and an aging fl eet, titanium supply was tight and prices high. The supply situation improved and prices declined as mill utilization ramped up and new titanium sponge production capacity came on-line. At the same time, delays in the introduction of major airframe projects and a slowing global economy eased supply concerns by stretching out delivery schedules. The aerospace industry continues to consume roughly half of all titanium and titanium alloy products currently produced, and order books continue to grow. This has been buoyed by the increased use of composite materials in new airframes, which demands an increased overall content of titanium in the structure. As much as the industry focuses on pricing and supply issues, a key to the development of more applications for titanium is processing. Low-cost titanium synthesis approaches are being developed and have been the subject of more than one TMS Titanium Committee-sponsored symposium. But even with the widespread availability of such material, processes that minimize waste, tooling, and energy consumption must be employed to extract the value in this amazing metal. This issue of JOM takes a look at current research and practical approaches in diverse application areas of titanium products. The following four articles span the size scale from tonnes of industrial mill products to grams of medical implants. We look at ways to reclaim and use lower-quality aerospace alloy material, and a novel process for making composite alloys that could fi nd application in the transportation industry. The fi rst paper, by R.D. Goin, focuses on industrial applications for titanium. Titanium or zirconium is often the material of choice for demanding corrosion conditions such as seawater desalination, power generation, or chemical processing. Cost issues can sometimes preclude their use, however, in favor of less corrosion-resistant alloys. Fusion welding of titanium to lower-cost stainless steels to create linings is not practical. Solid-state joining processes such as extrusion bonding and inertia welding can be used to fabricate bimetallic components, such as pipe and tubing, that provide a corrosion-resistant process interface with a lower-cost structural material to maximize value. The next paper, by M. Garcia de Cortazar et al., outlines research for making discontinuously reinforced titanium composites using master compounds produced by the self-propagating hightemperature synthesis approach. These compounds would enable the manufacture of chemically homogeneous titanium composite components using low-cost near-net-shape processes such as investment casting. This route avoids the isotropic property conditions sometimes seen with fi ber-wound continuously reinforced titanium-matrix composites. A range of compositions based on the addition of titanium diboride are shown, along with properties of trial castings. The paper by H. Guo et al. examines a powder sintering and forging approach on the microstructure and properties of Ti-10V-2Fe-3Al alloy. Often used as a structural alloy in aerospace applications, ingots of Ti-10-2-3 can be subject to a condition known as “beta fl eck” from chemical segregation of alloy elements that stabilize the beta phase. This condition can be cause for rejection of an ingot or component on quality grounds. This paper explores a route for processing Ti-10-2-3 with beta fl eck by employing the hydridedehydride process to break the bulk material down into a powder form. The powder is then blended and processed by a variety of standard powder metallurgy (PM) techniques and isothermal forging to full density. Mechanical properties are compared with values from the literature. Finally, we take a trip inside the human body to explore new designs and production of customized Ti-6Al-4V dental implants with the paper by G. Chahine et al. This is a fascinating approach whereby researchers are creating replicas of a patient’s actual tooth, root and all, in titanium from a computer-assisted design fi le using a net-shape electron beam fabrication technique. This, along with the ability to customize the structure of the implant for optimal anchoring and bone in-growth, points to an improved approach to dental implants that speeds healing, improves comfort, and can provide longer service life of the prosthesis. Productivity can be maximized at low overall cost by taking advantage of the capability to fabricate a large number of custom implants simultaneously.
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Jul 1, 2009
Hitoshi Ozaki + 2
Open Access