Die casting alloy classification and main properties
Die-casting alloys are typically categorized based on the type of base metal, falling into four main groups: aluminum alloys, zinc alloys, magnesium alloys, and copper alloys. Each alloy type is further subdivided into multiple grades based on its composition. These alloys exhibit significant differences in their primary properties, making them suitable for different die-casting scenarios. This classification facilitates rapid selection of appropriate alloy materials based on the performance requirements and application environment of the casting, improving the relevance and efficiency of die-casting production.
Aluminum alloys are the most widely used type of die-casting alloy. Based on their chemical composition, they can be divided into Al-Si, Al-Si-Cu, Al-Si-Mg, and Al-Mg series. Al-Si alloys are the most commonly used aluminum die-casting alloys, typically containing 6%-12% silicon. They offer excellent fluidity, low shrinkage, and good airtightness, making them suitable for the production of complex, thin-walled castings such as automotive engine blocks and transmission housings. For example, ADC12 alloy (Al-Si-Cu series) contains 9.6%-12.0% silicon and 1.5%-3.5% copper, with a tensile strength of 220-280 MPa and an elongation of 2%-5%, offering excellent castability and machinability. A380 alloy (Al-Si-Cu series) boasts even higher strength, reaching a tensile strength of 310 MPa, making it suitable for parts subject to high loads. Al-Mg alloys (such as 518 alloy) are known for their high corrosion resistance. They have a magnesium content of 4%-5%, but have poor fluidity and are suitable for the production of thick-walled castings that require corrosion resistance.
Zinc alloys can be divided into Zn-Al series, Zn-Al-Cu series, Zn-Al-Cu-Mg series, etc. according to their chemical composition. Among them, the Zn-Al-Cu series is the most commonly used die-cast zinc alloy. According to the different aluminum and copper content, it can be divided into multiple grades, such as Zamak3, Zamak5, Zamak7, etc. Zamak3 alloy contains 3.5%-4.3% aluminum, ≤0.03% copper, and 0.03%-0.08% magnesium. It has excellent fluidity and surface finish and is suitable for the production of small precision castings. Its tensile strength is 280MPa, elongation is 10%, and hardness is 75HB; Zamak5 alloy contains 3.5%-4.3% aluminum and 0.7%-1.2% copper. Due to the increase in copper content, the strength and hardness are improved. The tensile strength is 320MPa, the elongation is 7%, and the hardness is 82HB. It is suitable for parts that bear a certain load; Zamak7 alloy reduces the aluminum content (2.0%-3.0%), increases the purity of zinc, has better dimensional stability, and is suitable for the production of parts requiring high precision.
Magnesium alloys can be classified by chemical composition into Mg-Al, Mg-Zn-Zr, and Mg-RE (rare earth magnesium alloys). Mg-Al alloys (such as the AZ series) are the most commonly used die-cast magnesium alloys. Depending on the aluminum and zinc content, they are classified into grades such as AZ91D, AM60B, and AM50A . AZ91D alloy contains 8.3%-9.7% aluminum, 0.3%-1.0% zinc, and 0.17%-0.4% manganese. It exhibits excellent casting and mechanical properties, with a tensile strength of 230 MPa and an elongation of 3%, making it suitable for the production of automotive parts and 3C product casings. AM60B alloy contains 5.5%-6.5% aluminum and ≤0.2% zinc, achieving an elongation of up to 10% and exhibiting improved toughness, making it suitable for parts subjected to impact loads. Mg-RE alloys (such as WE43) offer excellent high-temperature performance, maintaining high strength at temperatures between 150-250°C. They are suitable for parts in high-temperature environments such as engines, but their higher cost limits their application.
Copper alloy die-casting can be divided into brass ( Cu-Zn alloy) and bronze ( Cu-Sn alloy, Cu-Al alloy, etc.) based on chemical composition. Brass is widely used due to its excellent casting properties. For example, HPb59-1 brass contains 57%-60% copper , 1%-2% lead , and the balance zinc. It has good fluidity and machinability, a tensile strength of 400-450 MPa , and a thermal conductivity exceeding 100 W/(m · K) , making it suitable for the production of parts such as radiators and valves. Tin bronze (such as ZCuSn10Pb1 ) contains 9%-11% tin and 0.5%-2% lead . It has excellent wear and corrosion resistance, a tensile strength of 310 MPa , and is suitable for wear-resistant parts such as bearings and gears. However, its poor fluidity makes die-casting difficult. Copper alloys are primarily characterized by their high melting point and high thermal and electrical conductivity. However, die-casting requires high energy consumption and has a short mold life, limiting their application.
The key properties of various die-cast alloys vary significantly, and selection requires comprehensive consideration of factors such as the casting’s mechanical properties, operating environment, process requirements, and cost. For example, magnesium or aluminum alloys are preferred for lightweight automotive parts; zinc alloys can be selected for small parts requiring high precision and low cost; and copper alloys are used for parts requiring high thermal conductivity and high wear resistance. Furthermore, different grades of the same alloy also exhibit performance differences, such as Zamak3 and Zamak5 zinc alloys. The appropriate grade must be selected based on the part’s strength requirements. When producing 5G base station radiators, an electronic equipment manufacturer compared the performance of aluminum and copper alloys and ultimately selected HPb59-1 brass. This brass has a thermal conductivity 1.5 times that of aluminum alloy, better meeting heat dissipation requirements and ensuring stable operation of base station equipment.
