Magnesium Alloy
Magnesium and magnesium-based alloys
Magnesium (Mg) is a silver-white metal; melting point is 648.8°C and boiling point is 1107°C. The density is 1.74 g/cm3 which is only 2/3 of aluminum, 2/5 of titanium, and 1/4 of steel;
The mechanical properties of pure magnesium are low. Its tensile strength is about 165~205MPa, its yield strength is about 69~105MPa, and its elongation after fracture is about 3~10%. Its corrosion resistance is also very low and it cannot be directly used as a structure. Material.
Therefore, various magnesium alloys can be manufactured by adding alloying elements such as aluminum, zinc, zirconium, and cerium to magnesium.
Magnesium alloys
Magnesium alloy is an alloy composed of magnesium as a matrix and the addition of other elements. Magnesium alloy is the lightest metal among practical metals, with a density of only about 1.8 g/cm3, and the lightest can be less than 1 g/cm3. Magnesium alloy has high strength and can be widely used as structural materials.
According to process performance, it can be divided into two categories: Cast magnesium alloy and Wrought magnesium alloy; according to different chemical compositions, there are mainly Mg-Al-Zn-Mn series (Az series), Mg-Al-Mn series (AM), Mg-Al -Si-Mn series (AS), Mg-Zn-Zrn (ZK), Mg-Zn-RE series (ZE) and other alloys.
Magnesium alloy grades
In ASTM standards, the main varieties of magnesium alloys are AZ31B, AZ91D, AM60B, AM50A and AS41B. Taking AZ91D as an example, A and Z represent the main added elements aluminum and zinc respectively, 9 represents the weight proportion of the first added element aluminum, which is about 9%, 1 represents the weight proportion of the second added element zinc, which is about 1%, D Indicates the alloy development serial number. When other trace amounts of added elements and impurities are not considered, the weight ratio of magnesium in magnesium alloys is the balance after deducting the added elements.
Fig1 Stress-strain curve of high-strength and tough magnesium alloy
From internal test data
Stress-strain curve of high-strength and tough magnesium alloys
Typical mechanical properties of magnesium alloys include tensile strength between 115 and 600 MPa, yield strength between 70 and 400 MPa, elongation at break usually around 8% to 20%, and Brinell hardness between 50 and 120 HB.
The specific strength of magnesium alloy is higher than that of aluminum alloy and steel, and slightly lower than that of fiber-reinforced plastics with the highest specific strength; the specific stiffness is equivalent to that of aluminum alloy and steel;
The wear resistance of magnesium alloy is much better than that of low carbon steel and exceeds that of die-cast aluminum alloy A380;
The vibration damping performance of magnesium alloy is 30 times higher than that of aluminum alloy;
The impact resistance is significantly better than that of die-cast aluminum alloy, and the dents caused by collision are smaller than other metal materials.
The elongation of magnesium alloy is greater than that of aluminum alloy; magnesium alloy has good creep resistance and has smaller dimensional creep as time and temperature change.
Magnesium alloy has very good machinability and is more suitable for die-casting large parts than aluminum;
The production cost per kilogram of magnesium die-casting is almost the same as that of aluminum; magnesium alloy has low cutting resistance, and during machining, the processing speed is faster, shortening the processing cycle. If the cutting resistance of magnesium alloy is set to 1.0, then the cutting resistance of aluminum alloy, brass and cast iron are 1.8, 2.3 and 3.5 respectively.
It has good electromagnetic wave shielding performance and its magnetic shielding performance is much better than that of aluminum alloy. The electromagnetic wave shielding performance of magnesium alloy is better than that of electroplated shielding film on plastic.
Compared with other metals, magnesium alloy has a lower melting point, smaller specific heat, and thermal conductivity 200 times higher than plastic; its thermal expansion performance is only 1/2 that of plastic. The energy used in the regeneration and melting process is 4% of the energy used to create new materials. Therefore, magnesium alloys are known as "green" environmentally friendly recyclable materials.
Magnesium is very cheap to make. Although the price per kilogram of magnesium ingots is more expensive than that of aluminum and iron, the price per unit volume of the finished product is almost the same.
Magnesium alloys have wide applications in many fields, including:
Automotive industry, communications electronics industry, aerospace industry, medical field, military industry, other fields, etc.
Magnesium alloys are developing rapidly and are used more and more widely. The research on magnesium alloys can be roughly divided into two categories: structural materials and functional materials.
In the technology market, there are many basic theoretical studies on the strengthening and toughening mechanism and plastic deformation mechanism of magnesium alloys. There are many studies on rare earth alloys to improve the strength and corrosion resistance of magnesium alloys.
Revealed the broad application prospects of magnesium alloys in various fields.