With the improvement of people's quality of life, the requirements for product aesthetics and quality are also constantly improving. More and more consumer products are made of alloy materials. Metal materials give people a sense of high-end, sturdy, and durable quality, while traditional plastic shell products are gradually labeled as "cheap" and "low-quality" in consumers' minds.
For consumer products, commonly used alloy materials are aluminum alloys, zinc alloys and magnesium alloys. Titanium alloys are commonly used in the medical field due to their good biocompatibility. This article will take a look at the characteristics of these alloy materials and make a comparison.
Among the four alloys, titanium alloy is the hardest and has the highest strength. In terms of hardness, titanium alloy is much harder than the other three alloys. In terms of tensile strength, titanium alloys are stronger than zinc alloys, followed by magnesium alloys, and the lowest strength is aluminum alloys.
However, as far as product structure design is concerned, weight also needs to be considered. If specific gravity is taken into account, zinc alloy has the smallest specific strength because of its highest density. Titanium alloys and magnesium alloys have high specific strength, but titanium alloys are expensive and have poor processing performance. Therefore, magnesium alloys are often used in structural parts that require comprehensive consideration of weight and strength.
Magnesium and Magnesium Alloys
01. Mg
Magnesium has low density and is easy to burn, which is determined by its physical and chemical properties. At 20°C, the density of metallic magnesium is 1.738g/cm3, and the density of liquid metallic magnesium is 1.58g/cm3; under standard atmospheric pressure, the melting point of metallic magnesium is (650±1)°C, and the boiling point is 1090°C. When heated in air, metallic magnesium begins to burn at 632°C to 635°C. Therefore, it is determined that the preparation and alloy smelting process of magnesium are relatively complicated. The purity of magnesium for industrial use can reach 99.9%, but pure magnesium cannot be used as a structural material. Magnesium alloys formed by adding elements such as aluminum, zinc, lithium, manganese, zirconium and rare earth to pure magnesium have high strength. Magnesium-aluminum alloys are the most widely used, followed by magnesium-manganese alloys and magnesium-zinc-zirconium alloys. Mainly used in aviation, aerospace, transportation, chemical industry, rocket and other industrial sectors.
02. Characteristics of magnesium alloy
① light weight
The specific gravity of magnesium is only 1.8G/CM3, and that of aluminum alloy is 2.7G/CM3. Magnesium alloy is 30% lighter than aluminum alloy and 80% lighter than steel. Therefore, magnesium alloys in automobiles and portable electronic products have become ideal materials for parts manufacturing.
②Strength
Magnesium alloys have excellent strength-to-weight ratios among engineering materials such as metals and plastics. Yield strength 160MPa, tensile strength 240MPa.
③Die casting
Under the condition of maintaining a good structure, the magnesium alloy allows the wall thickness of the casting to reach a minimum of 0.6mm, which cannot be achieved by plastics at the same strength. The die-casting performance of aluminum alloy can only be compared with magnesium alloy when it is above 1.2-1.5mm. Magnesium alloy is easier to die-cast and is suitable for mass die-casting production (production speed can reach 1.5 times that of aluminum). In addition, the wear of magnesium alloy die is also lower than that of aluminum. The main reason is the high viscosity of aluminum.
④Shock absorption
Magnesium has excellent hysteresis shock absorption performance, can absorb vibration and noise, and can be used as equipment casing to reduce noise transmission, prevent shock and prevent dent damage. It is good as a backplane for LCD or LED.
⑤ Rigidity
Magnesium is twice as rigid as aluminum and higher than most plastics. Magnesium has good resistance to stress.
⑥ High electromagnetic interference barrier
Magnesium alloy has a good function of blocking electromagnetic waves and is suitable for the production of electronic products.
⑦Good cutting performance
Magnesium has better machinability than aluminum and zinc, making magnesium an easier machinable metallic material.
⑧The specific heat capacity of magnesium alloy is small, and the cooling speed of the alloy liquid is fast.
⑨The affinity between magnesium alloy and mold steel is small, and it is not easy to adhere to the mold.
03. Advantages of magnesium alloy materials
① light weight
The proportion of magnesium alloy is the lightest among all structural alloys. Its proportion is 68% of aluminum alloy, 27% of zinc alloy, and 23% of steel. In addition to being used as the shell and internal structural parts of 3C products, it is also used in automobiles. , aircraft and other parts of the excellent material.
②High specific strength and specific stiffness
The specific strength of magnesium alloy is significantly higher than that of aluminum alloy and steel, and its specific stiffness is equivalent to that of aluminum alloy and steel, but far higher than that of engineering plastics, which is 10 times that of ordinary plastics.
③Good vibration resistance
Under the same load, the damping performance is 100 times that of aluminum and 300-500 times that of titanium alloy.
④Excellent electromagnetic shielding
The shell of 3C products (mobile phone and computer) should be able to provide superior anti-electromagnetic protection, and the magnesium alloy shell can completely absorb electromagnetic interference with a frequency exceeding 100db.
⑤ Good heat dissipation
The thermal conductivity of ordinary metals is hundreds of times that of plastics. The thermal conductivity of magnesium alloys is slightly lower than that of aluminum alloys and copper alloys, and much higher than that of titanium alloys. The specific heat is close to that of water, which is the highest among commonly used alloys.
⑥ good texture
The appearance and touch texture of magnesium alloy are excellent, which makes the product more luxurious.
⑦ Good recyclability
As long as the cost is equivalent to 4% of the price of new materials, magnesium alloy products and waste materials can be recycled.
⑧Stable resource provision
The reserve of magnesium element in the earth's crust ranks eighth, and most of the magnesium raw materials are extracted from seawater, so its resources are stable and sufficient.
04. Advantages of magnesium alloy die casting
① High productivity
②High precision
③Good surface quality
④ fine casting grain
⑤Products with thin walls and complex structures can be die-casted
Aluminum alloy
01. Aluminum alloy
The general term for alloys based on aluminum. The main alloying elements are copper, silicon, magnesium, zinc, manganese, and the secondary alloying elements are nickel, iron, titanium, chromium, lithium, etc.
Aluminum alloy has low density, but high specific strength, which is close to or exceeds that of high-quality steel. It has good plasticity and can be processed into various profiles. It has excellent electrical conductivity, thermal conductivity and corrosion resistance. It is widely used in industry, and its usage is second only to steel. .
02. Aluminum alloy classification
Aluminum alloys are divided into two categories: cast aluminum alloys, which are used in the cast state; deformed aluminum alloys, which can withstand pressure processing and have higher mechanical properties than the cast state. It can be processed into aluminum alloy materials of various shapes and specifications. It is mainly used in the manufacture of aviation equipment, daily necessities, doors and windows for construction, etc.
03. Aluminum alloy processing method
Aluminum alloy can be divided into deformed aluminum alloy and cast aluminum alloy according to the processing method. Deformed aluminum alloys are divided into non-heat-treatable aluminum alloys and heat-treatable aluminum alloys. The non-heat-treatable type cannot improve the mechanical properties through heat treatment, but can only be strengthened through cold deformation. It mainly includes high-purity aluminum, industrial high-purity aluminum, industrial pure aluminum, and anti-rust aluminum. Heat-treatable and strengthened aluminum alloys can improve mechanical properties through heat treatment such as quenching and aging. It can be divided into duralumin, wrought aluminum, super duralumin and special aluminum alloys.
Aluminum alloys can be heat treated to obtain good mechanical properties, physical properties and corrosion resistance.
Cast aluminum alloys can be divided into aluminum-silicon alloys, aluminum-copper alloys, aluminum-magnesium alloys and aluminum-zinc alloys according to their chemical composition.
04. Comparison of aluminum alloy and magnesium alloy
There is not much difference between aluminum alloy and magnesium alloy, except that aluminum alloy is slightly heavier. Processability is relatively sticky. Moreover, since the die-casting aluminum alloy contains a relatively high content of Si, it directly reacts with the chemical solution when performing Anodizing (anodizing). so as to fail. Magnesium alloy is acceptable, and the color is brighter, and Anodizing can be used for the post-appearance process. However, not everyone can do it.
