"magnesium alloy"

Magnesium alloys are alloys based on magnesium added to other elements. Its characteristics are: low density (about 1.8g/cm3 magnesium alloy), high specific strength, large elastic modulus, good heat dissipation, good shock absorption, greater ability to withstand impact loads than aluminum alloys, and good corrosion resistance to organics and alkalis . The main alloying elements are aluminum, zinc, manganese, niobium, tantalum, and a small amount of zirconium or cadmium. Magnesium alloys are the most widely used at present, followed by magnesium-manganese alloys and magnesium-zinc-zirconium alloys. Mainly used in aviation, aerospace, transportation, chemical, rocket and other industrial sectors. The lightest metal in practical metals, the proportion of magnesium is about 2/3 of that of aluminum, which is 1/4 of that of iron. It is the lightest metal in practical metals, with high strength and high rigidity.

Magnesium alloy features

Its processing and corrosion and mechanical properties have many characteristics: good heat dissipation, light weight, good rigidity, a certain degree of corrosion resistance and dimensional stability, impact resistance, wear resistance, attenuation performance and easy recovery; there are also high Thermal and conductive properties, non-magnetic, good shielding and non-toxic characteristics.

Applications: Magnesium alloys are widely used in portable equipment and automotive industries for light weight

Although the specific gravity of magnesium alloys is heavier than that of plastics, the strength and elastic modulus per unit weight are higher than that of plastics. Therefore, in the case of the same strength components, the components of magnesium alloys can be made thinner and lighter than plastics. In addition, since the specific strength of the magnesium alloy is also higher than that of the aluminum alloy and iron, the weight of the aluminum or iron component can be reduced without reducing the strength of the component.

The relative specific strength (the ratio of strength to mass) of magnesium alloys is the highest. The specific stiffness (ratio of stiffness to mass) is similar to that of aluminum alloys and steels, which is much higher than that of engineering plastics.

In the elastic range, when the magnesium alloy is subjected to an impact load, the energy absorbed by the magnesium alloy is larger than that of the aluminum alloy by half, so the magnesium alloy has a good shock and noise reduction performance.

The melting point of magnesium alloy is lower than the melting point of aluminum alloy, and the die casting molding performance is good. The tensile strength of magnesium alloy castings is comparable to that of aluminum alloy castings, generally up to 250 MPA and up to more than 600 Mpa. Yield strength, elongation and aluminum alloy are also not much difference.

Magnesium alloys also have a good corrosion resistance, electromagnetic shielding performance, radiation protection performance, can be achieved 100%

The stability of the magnesium alloy parts is higher than that of the die casting castings, which enables high-precision machining.

Magnesium alloys have good die-casting performance, and the wall thickness of the die castings can be as small as 0.5mm. Adapt to manufacturing all kinds of automotive die castings.

However, the coefficient of linear expansion of magnesium alloys is large, reaching 25 to 26 μm/m°C, while that of aluminum alloy is 23 μm/m°C, brass is about 20 μm/m°C, structural steel is 12 μm/m°C, and cast iron is about 10 μm/ In m°C, rocks (granite, marble, etc.) are only 5-9 μm/m°C and glass is 5-11 μm/m°C.

Magnesium alloys are alloys based on magnesium added to other elements. Its characteristics are: low density, high specific strength, large elastic modulus, good shock absorption, greater ability to withstand impact loads than aluminum alloys, and good corrosion resistance. The main alloying elements are aluminum, zinc, manganese, niobium, tantalum, and a small amount of zirconium or cadmium. Magnesium alloys are the most widely used at present, followed by magnesium-manganese alloys and magnesium-zinc-zirconium alloys.

Since the specific gravity of magnesium alloys is the lightest of all structural alloys, the weight of aluminum or iron parts can be reduced without reducing the strength of the parts. The specific strength of magnesium alloys is significantly higher than that of aluminum alloys and steels, and the specific stiffness is comparable to that of aluminum alloys and steels. In the elastic range, when the magnesium alloy is subjected to an impact load, the absorbed energy is larger than that of the aluminum alloy member, so the magnesium alloy has a good shock and noise reduction performance. At the same load, vibration damping is 100 times that of aluminum and 300 to 500 times that of titanium alloy. Excellent electromagnetic shielding, 3C product casing (mobile phone and computer) should be able to provide superior anti-electromagnetic protection, and magnesium alloy shell can completely absorb the electromagnetic interference frequency of more than 100db. The texture is good, the appearance and touch texture of magnesium alloy are excellent, which makes the product more luxurious and less prone to corrosion in the air.

The heat dissipation of magnesium alloys has absolute advantages relative to the alloys: According to the formula: Q = dvC â–³ t where Q - heat; d = specific gravity; V = volume; C = specific heat capacity; â–³ t = (t1-t2) temperature changes When the same volume and shape of magnesium alloy and aluminum alloy, receive the same amount of heat Q, the temperature ratio of the two changes: â–³ t / â–³ t = 2.74x0.23/1.81x1.05 = 1/3; that is, magnesium The alloy is 1/3 of the aluminum alloy; the magnesium alloy thermal conductivity is 54W/mk; the aluminum alloy thermal conductivity is 100W/mk; the difference is twice. This means that for a heat sink with the same volume and shape of magnesium alloy and aluminum alloy material, the heat (temperature) produced by a heat source is more easily transferred from the root of the heat sink to the top, and the top is more likely to reach a high temperature. That is, the temperature difference between the root portion and the top portion of the aluminum alloy material is smaller than that of the magnesium alloy material. This means that the temperature difference between the air temperature at the root of the heat sink made of the magnesium alloy material and the temperature of the air at the top is larger than that of the heat sink made of the aluminum alloy material, so the diffusion convection of the air inside the heat sink is accelerated, and the heat radiation efficiency is improved. Therefore, the same temperature, magnesium alloy heat dissipation time is not half of aluminum alloy.

Therefore, magnesium alloys are ideal for LED and other lighting applications, automotive applications, and other accessories that require high quality, high strength, and high toughness.

Magnesium alloy application

Application in aerospace

Magnesium alloys are the lightest metal structural materials used in the aircraft, spacecraft and rocket manufacturing industries. Magnesium is lighter than aluminum and has a specific gravity of 1.8 and a low strength of only 200 to 300 MPa (20 to 30 kg/mm2). It is mainly used to make low-load parts.

Magnesium alloys tend to oxidize and corrode in moist air, so the parts need to be chemically treated or painted before use. Germany first produced and used aluminum-containing magnesium alloys on aircraft. Magnesium alloys have high anti-vibration ability, can absorb large energy under impact load, and have good heat absorption performance, and thus are ideal materials for manufacturing aircraft hubs. Magnesium alloys are stable in gasoline, kerosene, and lubricating oils and are suitable for the manufacture of engine gearboxes, oil pumps, and tubing. They are also used to make rocker arms, flaps, and flaps because of the small inertial forces generated during rotation and reciprocation. Doors and rudder surface and other moving parts. Civilian and fighter aircraft, especially bombers, use magnesium alloy products extensively. For example, the fuselage part of the B-52 bomber used 635 kg of magnesium alloy plates, 90 kg of extrusions, and more than 200 kg of castings. Magnesium alloys are also used in ** and some components on satellites, such as the Chinese “Red Flag” underground space, instrument capsules, tail cabins, and engine mounts that use magnesium alloys. China's rare earth resources are abundant. It has been developed in the 1970s as a cerium-added magnesium alloy, which has improved room temperature strength and can be used at 300°C for a long period of time. It has been widely used in the aerospace industry.

At present, the application components of magnesium alloys in automobiles can be classified into two categories.

(1) Shell class. Such as clutch housing, valve cover, instrument panel, gearbox body, crankcase, engine front cover, cylinder head, air conditioner housing, etc.

(2) stents. Such as steering wheel, steering bracket, brake bracket, seat frame, mirror bracket, distribution bracket and so on.

According to relevant research, 60% of the fuel used in automobiles is consumed by the vehicle's own weight, and the fuel efficiency can be increased by more than 5% for each 10% reduction in the vehicle's own weight, and the fuel consumption per 100km can be reduced by about 0.7L for each 100kg of vehicle's own weight. Saving 1 L of fuel can reduce CO2 emissions by 2.5 g, and annual emissions can be reduced by more than 30%. Therefore, reducing the impact of vehicle weight on the environment and energy is very large, and the lightweighting of automobiles becomes an inevitable trend.

In mobile phones, the size of LCD screens on laptops has been increasing year by year. Magnesium alloys have been used on their branch frame and on the back of the case.

Although the thermal conductivity of magnesium alloys is less than that of aluminum alloys, it is several tens of times higher than that of plastics. Therefore, magnesium alloys are used in electrical products and can effectively dissipate the heat inside.

Magnesium alloys are used on housings and heat sinks such as computers and projectors that generate high temperatures inside. The use of magnesium alloy on the outer cover of the TV allows for no vents.

Electromagnetic wave shielding: The electromagnetic shielding performance of magnesium alloy is better than plating the shielding film on plastic. Therefore, the use of magnesium alloy can eliminate the electroplating process of the electromagnetic wave shielding film.

Magnesium alloys are used for parts near vibration sources such as reading devices of hard disk drives. If magnesium alloys are used on the fan blades, vibrations can be reduced to a low level. In addition, magnesium alloys are used on steering wheels and seats in order to increase impact absorption and reduce weight after the car is hit.

Alloy Name Characteristics Application Range

AZ91D high strength and corrosion resistance of electrical products such as the shell

AM60B Elongation and Impact Resistance on Large Cars with Steering Wheels, Seats, etc.

AM50A Elongation and impact resistance on large car steering wheel and seats

AS41B Creep-Reducing Cars, etc.

Machinability: Magnesium alloys have lower cutting resistance than other metals and can be machined at higher speeds during machining.

Compared with other metals, the alloy has a large deformation resistance, and the depression caused by collision is smaller than other metals.

Absorption to vibrations and shocks: Since magnesium alloys have good absorption of vibrational energy, vibrations can be reduced by using components for driving and transmission. In addition, magnesium alloys with better impact energy absorption performance and better elongation than aluminum alloys can absorb impact energy without cracking after being impacted.

Regeneration: Unlike magnesium alloys and plastics, it can be simply regenerated without reducing its mechanical properties, while plastics are difficult to regenerate without reducing their mechanical properties. Compared with other metals, magnesium alloys have a low melting point and a low specific heat. The energy consumed for regenerative melting is 4% of the energy consumed by new materials.