The high cost of titanium
As many people know, the main factor limiting the wider use of titanium is its cost. Since the cost is significantly higher than that of aluminum and steel alloys, the use of titanium must be justified for each application. There are many factors that cause this situation. Separation of metals from ore requires high energy. Ingot melting is also energy-intensive; in addition, its high reactivity requires the use of water-cooled copper tanks or hearth melting in an inert atmosphere, depending on the melting technology. The processing cost is also very high, about 10-100 times slower than aluminum alloy processing. Recently, Froes 7 pointed out that the purchase cost of one kilogram of aluminum plate is lower than the cost of one kilogram of titanium sponge (the starting material). This sponge must also be melted by adding a master alloy multiple times, forged or forged and rolled into a size suitable for the thin plate, placed in the package together with multiple thin plates, rolled to the appropriate thickness, etched and ground to the final thickness to obtain the titanium plate .
Taking these factors into account, most of the research and development of Boeing and other original equipment manufacturers and manufacturers are devoted to reducing the purchase-to-flight ratio of titanium parts. For example, a 40 kg plate can be used to process a 5 kg part, which means that almost 90% of the titanium will become fragments (scrap). Reducing the ratio of buying to flying means that people are purchasing a very expensive material that is lighter in weight, and it also reduces the amount of processing on that material. Various technologies are being researched to achieve this. These include welding, greater use of extrusion where appropriate, superplastic forming and superplastic forming and diffusion bonding, hot stretch forming to obtain more precise forming shapes, and even powder metallurgy. In terms of welding, both fusion welding and solid-state welding are under study. Figure 4 illustrates an example of the reduction in purchase to flight that can be achieved by laser welding. Electron beam and friction stir and linear friction welding are also under study. Alloys with improved machinability are also sought.
