Review of the application status and development trends of 16 major military new materials（1）

Materials technology has always been a very important field in the scientific and technological development plans of countries around the world. Together with information technology, biotechnology, and energy technology, it is recognized as a high technology that covers the overall situation of mankind in today's society and for a considerable period of time in the future. Materials high technology is also the key technology of modern industry that supports today's human civilization, and it is also the most important material basis for a country's national defense. The defense industry is often the priority user of new materials technology achievements, and the research and development of new materials technology plays a decisive role in the development of the defense industry and weapons and equipment.

The strategic significance of new military materials New military materials are the material basis of a new generation of weapons and equipment, and are also key technologies in the military field of today's world. Military new materials technology is a new material technology used in the military field, which is the key to modern sophisticated weapons and equipment and an important part of military high technology. Countries around the world have attached great importance to the development of new military materials technology. Accelerating the development of new military materials technology is an important prerequisite for maintaining military leadership.

Application status of new military materials New military materials can be divided into two categories: structural materials and functional materials according to their uses. They are mainly used in the aviation industry, aerospace industry, weapons industry and shipbuilding industry.
Military structural materials 1. Aluminum alloy Aluminum alloy has always been the most widely used metal structural material in the military industry. Aluminum alloy has the characteristics of low density, high strength and good processing performance. As a structural material, it can be made into profiles, pipes, high-ribbed plates of various cross sections due to its excellent processing performance, so as to give full play to the potential of the material and improve the rigidity and strength of the components. Therefore, aluminum alloy is the preferred lightweight structural material for weapon lightweighting. In the aviation industry, aluminum alloy is mainly used to manufacture aircraft skins, bulkheads, long beams and honing bars; in the aerospace industry, aluminum alloy is an important material for launch vehicles and spacecraft structural parts. In the field of weapons, aluminum alloy has been successfully used in infantry fighting vehicles and armored transport vehicles. The recently developed howitzer gun mounts also use a large number of new aluminum alloy materials. In recent years, the use of aluminum alloy in the aerospace industry has decreased, but it is still one of the main structural materials in the military industry. The development trend of aluminum alloys is to pursue high purity, high strength, high toughness and high temperature resistance. The aluminum alloys used in the military industry mainly include aluminum-lithium alloys, aluminum-copper alloys (2000 series) and aluminum-zinc-magnesium alloys (7000 series). The new aluminum-lithium alloys are used in the aviation industry, and it is predicted that the weight of aircraft will drop by 8~15%; aluminum-lithium alloys will also become candidate structural materials for spacecraft and thin-walled missile shells. With the rapid development of the aerospace industry, the research focus of aluminum-lithium alloys is still to solve the problem of poor toughness in the thickness direction and reduce costs. 2. Magnesium alloys As the lightest engineering metal material, magnesium alloys have a series of unique properties such as light specific gravity, high specific strength and specific stiffness, good damping and thermal conductivity, strong electromagnetic shielding ability, and good vibration reduction, which greatly meet the needs of military fields such as aerospace, modern weapons and equipment. Magnesium alloys are widely used in military equipment, such as tank seat frames, commander's mirrors, gunner's mirrors, gearbox housings, engine filter seats, water inlet and outlet pipes, air distributor seats, oil pump housings, water pump housings, oil heat exchangers, oil filter housings, valve covers, respirators and other vehicle parts; tactical air defense missile support compartments and aileron skins, wall panels, reinforcement frames, rudder plates, bulkheads and other missile parts; fighter jets, bombers, helicopters, transport aircraft, airborne radars, surface-to-air missiles, launch vehicles, satellites and other spacecraft components. Magnesium alloys are light in weight, good in specific strength and stiffness, good in vibration reduction, electromagnetic interference, and strong in shielding capabilities, which can meet the requirements of military products for weight reduction, noise absorption, shock absorption, and radiation protection. It occupies a very important position in aerospace and national defense construction, and is a key structural material required for aircraft, satellites, missiles, fighters, tanks and other weapons and equipment. 3. Titanium alloy Titanium alloy has high tensile strength (441~1470MPa), low density (4.5g/cm³), excellent corrosion resistance, certain high temperature endurance strength at 300~550℃ and good low temperature impact toughness, and is an ideal lightweight structural material. Titanium alloy has the functional characteristics of superplasticity. By using superplastic forming-diffusion bonding technology, the alloy can be made into products with complex shapes and precise dimensions with little energy and material consumption. The application of titanium alloy in the aviation industry is mainly to make aircraft fuselage structural parts, landing gear, support beams, engine compressor discs, blades and joints; in the aerospace industry, titanium alloy is mainly used to make load-bearing components, frames, gas cylinders, pressure vessels, turbine pump casings, solid rocket engine casings and nozzles and other parts. In the early 1950s, industrial pure titanium was used to manufacture heat shields, tail covers, speed brakes and other structural parts of the rear fuselage on some military aircraft; in the 1960s, the application of titanium alloys in aircraft structures expanded to flap sliding, load-bearing bulkheads, landing gear beams and other major load-bearing structures; since the 1970s, the use of titanium alloys in military aircraft and engines has increased rapidly, from fighters to large military bombers and transport aircraft. Its use in F14 and F15 aircraft accounts for 25% of the structural weight, and its use in F100 and TF39 engines reaches 25% and 33% respectively; after the 1980s, titanium alloy materials and process technologies have achieved further development, and a B1B aircraft requires 90402 kg of titanium. Among the existing titanium alloys for aerospace, the most widely used is the multi-purpose a+b type Ti-6Al-4V alloy. In recent years, the West and Russia have successively developed two new types of titanium alloys, namely high-strength, high-toughness, weldable and formable titanium alloys and high-temperature, high-strength, flame-retardant titanium alloys. These two advanced titanium alloys have good application prospects in the future aerospace industry.

With the development of modern warfare, the army needs a multifunctional advanced howitzer system with great power, long range, high accuracy and rapid response capability. One of the key technologies of advanced howitzer systems is new material technology. The lightweighting of self-propelled artillery turrets, components, and light metal armored vehicles is an inevitable trend in the development of weapons. Under the premise of ensuring dynamics and protection, titanium alloys are widely used in army weapons. The use of titanium alloy in the 155 artillery recoil brake can not only reduce weight, but also reduce the deformation of the gun barrel caused by gravity, effectively improving the shooting accuracy; some complex-shaped components on main battle tanks and helicopter-anti-tank multi-purpose missiles can be made of titanium alloy, which can not only meet the performance requirements of the product but also reduce the processing costs of components. For a long time in the past, the application of titanium alloys was greatly restricted due to the high manufacturing cost. In recent years, countries around the world are actively developing low-cost titanium alloys, while reducing costs, they also need to improve the performance of titanium alloys. In my country, the manufacturing cost of titanium alloys is still relatively high. With the gradual increase in the use of titanium alloys, seeking lower manufacturing costs is an inevitable trend in the development of titanium alloys. 4. Composite materials 4.1 Resin-based composite materials Resin-based composite materials have good forming processability, high specific strength, high specific modulus, low density, fatigue resistance, shock absorption, chemical corrosion resistance, good dielectric properties, low thermal conductivity and other characteristics, and are widely used in the military industry. Resin-based composite materials can be divided into two categories: thermosetting and thermoplastic. Thermosetting resin-based composite materials are a type of composite material that is based on various thermosetting resins and added with various reinforcing fibers; while thermoplastic resins are a type of linear polymer compound that can be dissolved in solvents, softened and melted into a viscous liquid when heated, and hardened into a solid after cooling. Resin-based composite materials have excellent comprehensive properties, easy preparation technology, and abundant raw materials. In the aviation industry, resin-based composite materials are used to manufacture aircraft wings, fuselages, canards, horizontal tails and engine ducts; in the aerospace field, resin-based composite materials are not only important materials for rudders, radars, and air inlets, but can also be used to manufacture the thermal insulation shell of the combustion chamber of solid rocket engines, and can also be used as ablative heat-resistant materials for engine nozzles. The new cyanate resin composite materials developed in recent years have the advantages of strong moisture resistance, good microwave dielectric properties, and good dimensional stability. They are widely used in the manufacture of aerospace structural parts, primary and secondary load-bearing structural parts of aircraft, and radar antenna covers. 4.2 Metal-based composite materials Metal-based composite materials have high specific strength, high specific modulus, good high temperature performance, low thermal expansion coefficient, good dimensional stability, and excellent electrical and thermal conductivity. They have been widely used in the military industry. Aluminum, magnesium, and titanium are the main matrices of metal-based composite materials, and the reinforcing materials can generally be divided into three categories: fibers, particles, and whiskers. Among them, particle-reinforced aluminum-based composite materials have entered model verification, such as being used in F-16 fighters as ventral fins instead of aluminum alloys, and their stiffness and life are greatly improved. Carbon fiber reinforced aluminum and magnesium-based composite materials have high specific strength, close to zero thermal expansion coefficient and good dimensional stability, and are successfully used to make artificial satellite brackets, L-band planar antennas, space telescopes, artificial satellite parabolic antennas, etc.; silicon carbide particle reinforced aluminum-based composite materials have good high temperature performance and wear resistance, and can be used to make rockets, missile components, infrared and laser guidance system components, precision avionics devices, etc.; silicon carbide fiber reinforced titanium-based composite materials have good high temperature resistance and oxidation resistance, and are ideal structural materials for high thrust-to-weight ratio engines. They have entered the test stage of advanced engines. In the field of weapons industry, metal-based composite materials can be used for large-caliber tail stabilized discarding sabot armor-piercing projectiles, anti-helicopter/anti-tank multi-purpose missile solid engine shells and other parts to reduce the weight of the warhead and improve combat capabilities. 4.3 Ceramic-based composites Ceramic-based composites are a general term for materials that are reinforced with fibers, whiskers or particles and combined with ceramic matrices through a certain composite process. It can be seen that ceramic-based composites are multiphase materials composed of a second phase component introduced into a ceramic matrix. It overcomes the inherent brittleness of ceramic materials and has become one of the most active aspects of current material science research. Ceramic-based composites have the characteristics of low density, high specific strength, good thermomechanical properties and thermal shock resistance, and are one of the key supporting materials for the future development of the military industry. Although ceramic materials have good high-temperature performance, they are very brittle. Methods to improve the brittleness of ceramic materials include phase change toughening, microcrack toughening, dispersed metal toughening and continuous fiber toughening. Ceramic-based composites are mainly used to make nozzle valves for aircraft gas turbine engines, which play an important role in improving the thrust-to-weight ratio of engines and reducing fuel consumption. 4.4 Carbon-carbon composites Carbon-carbon composites are composites composed of carbon fiber reinforcements and carbon matrices. Carbon-carbon composites have a series of advantages such as high specific strength, good thermal shock resistance, strong ablation resistance, and designable performance. The development of carbon-carbon composite materials is closely related to the stringent requirements of aerospace technology. Since the 1980s, the research on carbon-carbon composite materials has entered the stage of improving performance and expanding applications. In the military industry, the most eye-catching application of carbon-carbon composite materials is the anti-oxidation carbon-carbon nose cone cap and wing leading edge of the space shuttle, and the largest carbon-carbon product is the brake pad of supersonic aircraft. Carbon-carbon composite materials are mainly used as ablative materials and thermal structural materials in aerospace. Specifically, they are used as nose cone caps of intercontinental missile warheads, solid rocket nozzles and wing leading edges of space shuttles. At present, the density of advanced carbon-carbon nozzle materials is 1.87~1.97 g/cubic centimeter, and the hoop tensile strength is 75~115 MPa. The recently developed long-range intercontinental missile end caps are almost all made of carbon-carbon composite materials. With the development of modern aviation technology, the loading mass of aircraft is increasing, and the flight landing speed is increasing, which puts higher requirements on the emergency braking of aircraft. Carbon-carbon composite materials are lightweight, high temperature resistant, absorb large amounts of energy, and have good friction properties. Brake pads made of them are widely used in high-speed military aircraft. 5. Ultra-high strength steel Ultra-high strength steel is a steel with a yield strength and tensile strength exceeding 1200 MPa and 1400 MPa respectively. It is researched and developed to meet the requirements of high specific strength materials in aircraft structures. Due to the expansion of the application of titanium alloys and composite materials in aircraft, the amount of steel used in aircraft has decreased, but the key load-bearing components on aircraft are still made of ultra-high strength steel. At present, the internationally representative low-alloy ultra-high strength steel 300M is a typical steel for aircraft landing gear. In addition, low-alloy ultra-high strength steel D6AC is a typical solid rocket engine casing material. The development trend of ultra-high strength steel is to continuously improve toughness and stress corrosion resistance while ensuring ultra-high strength. 6. Advanced high-temperature alloys High-temperature alloys are key materials for aerospace power systems. High-temperature alloys are alloys that can withstand certain stresses at high temperatures of 600~1200℃ and have oxidation and corrosion resistance. They are the preferred materials for aerospace engine turbine discs. According to the different matrix components, high-temperature alloys are divided into three categories: iron-based, nickel-based and cobalt-based. Before the 1960s, engine turbine discs were made of forged high-temperature alloys, with typical grades being A286 and Inconel 718. In the 1970s, GE of the United States used rapidly solidified powder Rene95 alloy to make CFM56 engine turbine discs, which greatly increased its thrust-to-weight ratio and significantly increased its operating temperature. Since then, powder metallurgy turbine discs have developed rapidly. Recently, the United States has adopted a high-temperature alloy turbine disc manufactured by a spray deposition rapid solidification process. Compared with powder high-temperature alloys, the process is simple, the cost is reduced, and it has good forging processing performance. It is a preparation technology with great development potential. 7. Tungsten alloy Tungsten has the highest melting point among metals. Its outstanding advantage is that the high melting point brings good high-temperature strength and corrosion resistance to the material, and it has shown excellent characteristics in the military industry, especially in weapons manufacturing. In the weapons industry, it is mainly used to make warheads of various armor-piercing projectiles. Tungsten alloys refine the grains of materials and elongate the orientation of grains through powder pretreatment technology and large deformation strengthening technology, thereby improving the toughness and penetration power of materials. The tungsten core material of the 125Ⅱ armor-piercing projectile for main battle tanks developed in my country is W-Ni-Fe. It adopts a variable density compact sintering process, and the average performance reaches a tensile strength of 1200 MPa and an elongation of more than 15%. The combat technical index is to penetrate 600 mm thick homogeneous steel armor at a distance of 2000 meters. At present, tungsten alloys are widely used in main battle tanks with large aspect ratio armor-piercing projectiles, small and medium caliber air defense armor-piercing projectiles, and hypervelocity kinetic energy armor-piercing projectiles. This makes various armor-piercing projectiles have more powerful penetration power. 8. Intermetallic compounds Intermetallic compounds have long-range ordered superlattice structures and maintain strong metal bond bonding, which gives them many special physical and chemical properties and mechanical properties. Intermetallic compounds have excellent thermal strength and have become an important new high-temperature structural material that has been actively studied at home and abroad in recent years. In the military industry, intermetallic compounds have been used to manufacture parts that bear heat loads, such as the JT90 gas turbine engine blades manufactured by the American company Puao, the rotor blades of small aircraft engines manufactured by the US Air Force using titanium aluminum, etc., and Russia uses titanium aluminum intermetallic compounds instead of heat-resistant alloys as piston tops, which greatly improves the performance of the engine. In the field of weapons industry, the material of the tank engine supercharger turbine is K18 nickel-based high-temperature alloy. Because of its high specific gravity and large starting inertia, it affects the acceleration performance of the tank. The application of titanium aluminum intermetallic compounds and their oxidation products has greatly improved the performance of the tank.