Airbus's A380, Boeing's B77X, Comac's C919, and the CR929, a Sino-Russian joint venture, all use a proportion of titanium as structural components.
The development of the China-developed C919 large passenger jet began in 2008. On November 2, 2015, the first prototype in Shanghai commercial aircraft corporation of China rolled off the production line and test, on May 5, 2017, has carried on the first ferry flight on November 10, 17 December second C919 large aircraft and successfully in Shanghai Pudong airport first flight, marked the domestic large aircraft entering a new stage test flight. Although all the materials used in the prototype are foreign goods, it is mainly to obtain the need for airworthiness evidence. Since the second aircraft, the amount of domestic materials has been more than one batch, and more than one year.
Titanium and titanium alloy materials have been widely used in the manufacture of large civil aircraft. For example, some key parts of landing gear and wheels are forged with titanium alloy, and a small number of parts are forged with aluminum alloy. In THE C919, the net mass of titanium alloy parts accounts for about 10% of the total net mass of the aircraft, which is the most titanium material used among the civil aircraft made in China. Which parts are made of titanium (see Figure 1): the nose is forged with TI-6Al-4VEVI; the Hanging, using Ti-6Al-4V alloy forging, plate, and titanium alloy 55531 forgings; The outer wing is made of Ti-6Al-4V alloy forgings and plates; The central wing was forged with Ti-6Al-4V ELl alloy; Ti-6al-4v alloy forgings are used for the tail fins; The landing gear system uses Ti-6Al-4V alloy forgings.
Ti-6al-4v (TC4, GB/T3620) is a kind of α+β alloy with medium strength (> 900MPa). It was developed by Watertown Arsenal in the United States in 1954 and is widely used in the aerospace field. Its semi-finished products account for 55%-65% of the total output of titanium materials in the world. Used in the production of various aerospace and spacecraft forgings and plates, because it has excellent comprehensive performance, moderate price, early molding, the most in-depth research, the longest use time, and the most extensive application in the field, so the alloy has been born 67 years ago has maintained a vigorous vitality. The alloy's brand name is TC4 in China, GR.5 (Ti-6Al-4V) from American Titanium Company (Timet), RMI 6Al4V from American Active Metal Company, IMI318 from Britain, BT6 from Russia, ST-AI40 from Sumitomo Metal Company of Japan and TA6V from France. Krupp LT31. TC4 alloy can be strengthened by heat treatment in an annealing state, but its weldability is poor. The "ELI" in Ti-6Al-4V ELI indicates that the extra-low Interstitial titanium alloy is a kind of α and α+β titanium alloy suitable for use at low temperatures. Their strength properties increase with the decrease of temperature, and their toughness rarely decreases with the decrease of temperature. Can be used to manufacture low-temperature structural parts. Low-temperature titanium alloy oxygen content is very low, from the ordinary grade of 0.2% oxygen to ≤0.12%, and can be used at very low temperatures (< 77K), typical alloys are Ti-5Al-2.5Sn (ELI) and Ti-6AI-4V (ELI). Ti-5al-2.5sn ELI is a KIND of American alloy, which was introduced in the early 1960s and successfully copied by China in the late 1970s. The brand is TA7 (Chinese military standard GJ B495). Ti-5al-2.5sn ELI alloy is particularly suitable for liquid fuel tanks operating at -255℃.
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