Why titanium alloy is used for aerospace?

　　A titanium alloy commonly used for airframe structure parts is Ti-6Al-4V (acronym; Ti-64), which accounts for 80 to 90% of the titanium alloys generally used for aircraft. Ti-64 is the most widely usedα-βalloy,having well balanced characteristics with an abundance of data and application history.

　　Titanium alloy forgings are used for various parts of airframe structures and engines. In the case of the

　　Boeing 787, for example, titanium alloy accounts for approximately 15% of structural members, more than doubling the amount used for conventional aircraft. The amount (estimated) of titanium alloy used per unit has reached approximately 100 tonnes.

　　This is because titanium alloy has a high compatibility with carbon fiber reinforced plastic (CFRP), which is used in large amounts in place of aluminum alloy to reduce airframe weight and thus to improve fuel economy. When joined with CFRP members, titanium alloy is less likely to cause galvanic corrosion and inhibits strain due to temperature change, since its coefficient of thermal expansion is similar to that of CFRP.