Since the 20th century, the tide of space exploration has swept the world, and the world’s major powers have stepped into the field of space exploration.
From research on satellite manufacturing to manned spaceflight, the field of human space exploration has ushered in good development opportunities.
At the same time, although we have made many achievements, we are also facing many difficulties and challenges, and the research on various technologies is still in its infancy.
The selection of aerospace materials is one of the important difficulties in the aerospace field, which greatly restricts the development of the aerospace field.
This article provides convenience for exploring metal alloy materials suitable for the aerospace field.
After continuous exploration, magnesium alloy was finally selected as an important component of aerospace materials.
This article discusses the strict requirements of the living environment of spacecraft in space for spacecraft materials and various excellent properties of magnesium alloys, and finally explains the reason why magnesium alloys are suitable for spacecraft manufacturing in the aerospace field.
Let’s dive right into it.
Magnesium is one of the lightest metals commonly used in industry, so the developed magnesium alloy materials have become the lowest density of industrial metal alloy materials.
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Germany first started the industrial production of magnesium alloys in the 1980s, and first used 73.8kg magnesium alloys in automobile production in the 1930s.
In the mid-1930s, the Soviet Union applied magnesium alloys to the aircraft production industry.
Only a few years later, the demand for magnesium alloys rose rapidly.
Every world power has formulated and released research projects on magnesium metal, and attaches great importance to the development, research and use of magnesium alloy products.
Magnesium alloys have the advantages of low density, high specific strength, good thermal conductivity and light weight.
However, the general processing methods can not make magnesium alloy well formed, resulting in its poor plasticity.
Therefore, different magnesium alloy casting methods have been developed for different applications.
At present, magnesium alloys play a very important role in many research fields.
In the field of automobile manufacturing, magnesium alloy has been widely used in many developed countries for directional control system components, gearbox housing, automobile instrument panel, engine hood, frame, door and other components.
In the field of electronic communication, the characteristics of excellent magnesium alloys are conducive to mild products, which brings hope for the development of ultra-thin and ultralight products.
Many commonly used electronic components, such as cameras, televisions, laptops, plasma displays, mobile phones, are made of magnesium alloys.
In the medical field, the good corrosion resistance and chemical and physical stability of magnesium alloy ensure that its structure and function can remain relatively stable in the human body for a long time.
Therefore, magnesium alloys are often used for clinical medical implants.
In addition, magnesium alloy also plays a very important role in many other fields, and its value is difficult to estimate.
Space materials should have excellent anti-aging and anti-corrosion properties, and be able to withstand and adapt to the extreme space environment in space, so that spacecraft can survive stably in space.
The basic requirements for the materials used are: high density, high strength and high stiffness.
Using magnesium alloy material can reduce fuel consumption and improve flight distance and flight time.
In addition, the aircraft also needs higher specific strength and stiffness.
Aircraft must not only bear static loads, but also bear alternating loads caused by various factors such as takeoff and landing, maneuver flight and gust.
Therefore, people attach great importance to the fatigue resistance of aircraft materials.
Magnesium alloy materials meet the requirements of aerospace materials due to its light weight, specific strength, low density, good thermal conductivity and other excellent characteristics.
At present, Japan, the United States, Britain and other world powers are increasing their investment in magnesium alloy materials research.
At present, all countries in the world are increasing the output of magnesium alloys.
At present, China’s magnesium industry ranks first in the world in three aspects. China is a large country of magnesium resources, magnesium origin and export, and the reserves of magnesium metal rank first in the world.
However, there are still many shortcomings in the industrial production and manufacture of magnesium alloys in China.
The production technology of magnesium alloy in China is relatively backward, the productivity of magnesium alloy is low, the energy consumption is high, and the economic value is greatly reduced.
The export proportion of magnesium alloys in China is low;
At present, almost all magnesium alloys exported by China are produced according to foreign brands.
The key technologies and equipment used in magnesium alloy manufacturing and processing are rarely self-developed, but adopt foreign advanced technologies and equipment.
Performance requirements for aerospace materials
Materials should have the conditions that many places of aerospace materials usually need ultra-high temperature, high temperature and high vacuum.
Under extreme conditions, such as pressure, strong corrosion, and other people’s weight and holding space, the minimum volume and mass required are usually functionally equivalent.
Some of them need to operate in the atmosphere or in space for a long time, and cannot stop checking or replacing parts, so they need high reliability and quality assurance.
Different working environments have different requirements for the performance of aerospace materials.
The spacecraft has experienced aerodynamic heating in a high-temperature environment, and gas engines, and space due to the sun’s radiation, the spacecraft will fly in the air for a long period of time, some of which fly at speeds up to three times the speed of sound.
The use of high-temperature materials has good high-temperature endurance strength, creep strength, thermal fatigue strength, air and oxidation resistance and thermal corrosion resistance of corrosive media, and should have stable structures that work under high temperatures for a long time.
The gas temperature of the rocket engine can reach more than 3000 ° C and the injection speed can reach more than 10 Mach numbers.
When the rocket engine is mixed with the solid rocket fuel gas and solid particles and the head of the ballistic missile enters the atmosphere again, the speed of more than 20 Mach numbers and the temperature can reach tens of thousands of degrees, sometimes affecting the erosion of particle clouds.
Therefore, the environment involving high temperature in the space technology field usually includes high temperature and high-speed airflow and particle erosion.
In case of the need to use materials and melting heat to generate heat, heat sublimation, decomposition heat, design high-temperature wear-resistant materials and sweating cooling materials in combination with physical properties such as heat and high viscosity to meet the needs of the environment.
High temperature and solar radiation will cause the temperature of satellites in space and airship surface to alternate.
Generally, temperature control and insulation coating are used to solve the problem, forming a low-temperature environment for natural and low-temperature propellants.
The surface temperature of the aircraft will drop to about 50 °C when flying in the stratosphere at subsonic speeds.
In winter, the ambient temperature of the polar circle can be lower than 40 ℃ at the airport in each region.
In this environment, the components need metal or rubber tires to not produce embrittlement. The liquid rocket uses liquid oxygen (boiling point – 183 °C) and liquid hydrogen (boiling point – 253 °C) propellants, which puts forward more severe environmental conditions for materials.
Metal materials and the vast majority of polymer materials will become brittle under these conditions.
By developing or selecting appropriate materials, such as pure aluminum and aluminum alloys, titanium alloys, low-temperature steel, polytetrafluoroethylene, polyimide and perfluoropolyether, the effects of various media and atmospheric environment on the corrosion and aging of materials in the temperature load bearing capacity and sealing problems of structures, and the fuels (such as gasoline and kerosene) contacted by the plane media of aerospace materials, rocket propellants, such as nitric acid, nitrogen tetroxide, hydrazine) and various lubricating oils, hydraulic oils, etc.
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Most of them have strong corrosion to metal and non-metallic materials.
They expand under the sun’s radiation in the atmosphere and are eroded by wind and rain.
The mold will accelerate the aging process of polymer materials when stored in the underground humid environment for a long time.
Corrosion resistance, aging resistance and mold resistance are good space environment characteristics that aerospace materials should have.
The main feature of their effect on materials is high vacuum (1.33 × 10 MPa) and cosmic ray irradiation.
Metal materials contact each other under high vacuum, because the surface is purified by high vacuum, speeding up the molecular diffusion process, and the “cold welding” phenomenon appears.
The non-metallic materials can accelerate volatilization and aging under high vacuum and cosmic ray irradiation.
Sometimes this phenomenon can cause the volatile deposition of optical lens to be polluted and seal to fail due to aging.
Space materials are usually selected and developed through ground simulation tests.
In order to adapt to the space environment and reduce the structural weight of the aircraft, it is considered as one of the goals of aircraft design to choose the smallest possible to achieve absolute reliability, safety and life safety margin.
When aircraft such as missiles or rockets are used once in a short period of time, people make limit of material performance.
In order to make full use of material strength and ensure safety, the “design principle of damage tolerance” has been used for metal materials, which requires that materials not only have high specific strength, However, there is also high fracture toughness.
Determine the crack initiation life, crack growth rate and other data of the materials used under simulated conditions, and calculate the allowable crack length and corresponding life.
As an important basis for design, for the production and use of organic non-metallic materials, natural aging and artificial accelerated aging tests are required to determine their life and insurance period.
Properties and Characteristics of Magnesium Alloys
(1) High density
The problem of reducing fuel load has always been an urgent problem in the aerospace field.
However, among the existing engineering metal alloys, magnesium alloy has the lowest medium density, about 1.8g/cm3, which is about two thirds of the aluminum density and one quarter of the steel density.
This advantage makes the application of magnesium alloy in the aerospace field possible.
The specific gravity of magnesium alloy is the lightest among all structural alloys, so the weight of aluminum or iron parts can be reduced without reducing the strength of parts.
Magnesium alloys are light in weight and used in aerospace.
It not only greatly reduces the weight of the aircraft fuselage, but also greatly reduces the burden of fuel, which is of great significance for aircraft flight.
(2) High strength ratio
Magnesium alloys have high specific strength and density.
Compared with aluminum alloy and steel, magnesium alloy has better properties in specific strength and density.
Therefore, magnesium alloy materials can be used in aircraft assembly to manufacture heavy load components, such as spacecraft cabins, engine working parts, etc.
(3) Good heat dissipation
Compared with other alloys, magnesium alloys have absolute advantages in heat dissipation.
This shows that the difference between the air temperature at the root and the air temperature at the top of the heat sink made of magnesium alloy materials is far greater than other alloy materials, thus accelerating the diffusion of air in the convection radiator, greatly improving the heat dissipation efficiency of the radiator.
At the same temperature, the radiator made of magnesium alloy takes only half as long as that made of aluminum alloy.
(4) Good shock absorption effect
In the elastic range, when the magnesium alloy is impacted, the elastic deformation is relatively small, and the energy absorbed during the impact is relatively large, which makes the magnesium alloy material vibrate less during the impact.
The magnesium alloy material has good shock absorption capacity.
At the same time, due to the absorption of a large amount of collision energy, the noise generated by the collision will also be significantly reduced, making magnesium alloys have good noise reduction performance, which can greatly reduce various adverse effects of noise on aircraft.
The excellent shock absorption and noise reduction performance of magnesium alloy provides an important guarantee for aircraft safety.
(5) Good remolding
In the early 19th century, die casting technology was used to form magnesium alloy materials.
Because of the shortcomings of traditional die casting methods in eliminating surface defects and improving the internal quality of castings, people have continuously improved the process, and developed advanced magnesium alloy die casting technology on this basis.
Magnesium alloys have good remolding properties, which can be used to manufacture structural parts with complex shape and small bearing capacity, such as engine accessory brakes.
(6) Corrosion resistance
The influence of various media and atmospheric environment on materials is mainly manifested as corrosion and aging.
The contact medium of aerospace materials is aircraft fuel (such as gasoline, kerosene), rocket propellant (such as concentrated nitric acid, nitrogen tetroxide, hydrazine), various lubricants, hydraulic oil, etc.
Most of them have strong corrosion or expansion effects on metal and non-metallic materials.
The aging process of polymer materials can be accelerated by long-term storage of molds in the atmosphere exposed to the sun, molds eroded by wind and rain, and molds in the underground humid environment.
Corrosion resistance, aging resistance and mold resistance are excellent properties of aerospace materials.
Magnesium is the most active metal, and magnesium alloys are prone to corrosion due to the reaction on the surface of the primary battery, causing great losses.
Therefore, the surface protection of magnesium alloys is highly valued.
In the past, the surface protection of magnesium alloys was mainly carried out by chemical oxidation.
In the 1980s, the rapid development of anodic oxidation technology replaced the traditional chemical oxidation method.
In the research on the atmosphere casting technology of CO2+SF6 gas and the protection mechanism of the SF6 gas magnesium alloy matrix, it is found that a layer of priority and the film form of Mg will be generated on the magnesium alloy surface.
F ions can be used as the medium particles of MgO and the internal liquid Mg to further generate MgF2.
The material will protect the existence between the film and the matrix, making the protective film more compact.
Due to environmental problems, researchers are further looking for other gases with less pollution and also containing F to replace SF6.
Magnesium alloys are highly corrosive to many alkaline substances, and spacecraft has strong stability in alkaline environment.
(7) Some chemical properties are stable
Magnesium alloys have strong stability in some organic compounds, such as gasoline, kerosene and other fuels.
Therefore, magnesium alloys can be used to manufacture fuel tanks such as gasoline and kerosene, as well as various components that need to contact with gasoline, such as engine gears and brakes.
Magnesium alloy products are widely used in various civil and military aircraft, especially bombers.
For example, the body of B-25 is made of magnesium alloy, with 90kg extruded parts and more than 200kg castings.
Magnesium alloy is also used for missile and some satellite components, such as instrument cabin, tail cabin and engine support of China Red Flag surface to air missile.
(8) Temperature resistance Magnesium alloy has certain resistance to high temperature and low temperature, and can generally adapt to the living environment of spacecraft in the air.
Other metal materials are easy to melt in space due to the high temperature in some places.
The high temperature resistance of magnesium alloys can ensure that magnesium alloys can withstand high temperatures.
At the same time, aluminum alloy can adapt to low temperature environment, with strong thermal insulation effect, and can protect the normal operation of internal parts of the aircraft.
Magnesium alloy has good mechanical properties at high temperature, and can show excellent mechanical properties in space, which lays the foundation for space flight of spacecraft.
In the field of aerospace, the material requirements for aircraft production are extremely strict, and all parts of aircraft have extremely strict requirements.
Industrial materials are difficult to achieve the performance we need in the aerospace field. This problem has puzzled us for a long time.
However, the excellent properties of magnesium alloy are very consistent with the requirements of aerospace for spacecraft manufacturing materials.
Magnesium alloys are very suitable for applications ranging from body parts to engine parts.
The high density of magnesium can greatly reduce the fuel load of spacecraft, enabling spacecraft to fly longer and longer.
The high specific strength and specific stiffness ensure the stability of the spacecraft, making the spacecraft have excellent defense capability in space.
Good modification performance is conducive to the production of spacecraft components.
The effect of high damping provides a reliable guarantee for spacecraft.
Corrosion resistance, high temperature resistance and aluminum alloy materials can have strong vitality in space.
The excellent properties of magnesium alloy are very suitable for it to play an important role in the aerospace field.