Titanium alloy is a new important structural material used in the aerospace industry, with specific gravity, strength, and operating temperature between aluminum and steel, but with higher specific strength and excellent resistance to seawater corrosion and ultra-low temperature performance. In 1950, the United States first used it in non-load-bearing components such as thermal insulation panels, air ducts, and tail covers on the F-84 fighter-bomber. Starting in the 1960s, the use of titanium alloys shifted from the rear fuselage to the mid-fuselage, partially replacing structural steel in the manufacture of important load-bearing components such as frames, beams, and flap slide rails. The amount of titanium alloy used in military aircraft rapidly increased, reaching 20% to 25% of the aircraft's structural weight. From the 1970s, civil aircraft began to use titanium alloys in large quantities, with the Boeing 747 passenger aircraft using over 3,640 kilograms of titanium. For aircraft with a Mach number less than 2.5, titanium is mainly used to replace steel to reduce structural weight. For example, the U.S. SR-71 high-altitude, high-speed reconnaissance aircraft (with a flight Mach number of 3 and an altitude of 26,212 meters) has titanium accounting for 93% of the aircraft's structural weight, earning it the title of "all-titanium" aircraft. When the thrust-to-weight ratio of aircraft engines increased from 4-6 to 8-10, the compressor outlet temperature correspondingly increased from 200-300°C to 500-600°C, necessitating the replacement of aluminum-made low-pressure compressor disks and blades with titanium alloys, or using titanium alloys instead of stainless steel for high-pressure compressor disks and blades to reduce structural weight. In the 1970s, the amount of titanium alloy used in aircraft engines generally accounted for 20% to 30% of the total structural weight, mainly used for manufacturing compressor components such as forged titanium fans, compressor disks and blades, cast titanium compressor casings, intermediate casings, and bearing housings. Spacecraft mainly utilize the high specific strength, corrosion resistance, and low-temperature performance of titanium alloys to manufacture various pressure vessels, fuel tanks, fasteners, instrument straps, frameworks, and rocket casings. Artificial Earth satellites, lunar modules, manned spacecraft, and space shuttles also use titanium alloy plates and welded components.