Commonly used die-casting alloys and their main characteristics
Die-casting alloys are the core materials of die-casting production. Different alloys exhibit unique performance characteristics due to their compositional differences, adapting to different application scenarios. Currently, the four main types of die-casting alloys commonly used in industry include aluminum alloys, zinc alloys, magnesium alloys, and copper alloys. These alloys each have their own advantages in terms of fluidity, mechanical properties, and cost, and together constitute the core of the die-casting material system.
Aluminum alloys are the most widely used alloys in die-casting. Their excellent comprehensive properties have earned them a dominant position in industries such as automotive and consumer electronics. Commonly used die-cast aluminum alloys include Al-Si (such as YL113 and ADC12), Al-Si-Cu (such as YL112 and ADC10), and Al-Mg (such as the die-cast variant of 5083). Al-Si alloys contain 8% to 12% silicon and exhibit excellent fluidity (spiral length ≥ 650mm), making them suitable for forming complex, thin-walled parts. They offer tensile strengths of 200 to 280 MPa and elongations of 3% to 5%. They are widely used in automotive engine blocks and transmission housings. Al-Si-Cu alloys, with the addition of 2% to 4% copper, increase their strength to 250 to 320 MPa. They can be further strengthened through T6 heat treatment, but their corrosion resistance is slightly reduced. They are primarily used in load-bearing components such as steering knuckles. Al-Mg alloys contain 3% to 5% magnesium, have excellent corrosion resistance (no red rust after 1000 hours of salt spray test), and have an elongation of 10% to 15%, but have poor fluidity and are suitable for manufacturing corrosion-resistant parts such as marine equipment accessories.
Zinc alloys, with their low melting point, high fluidity, and excellent surface quality, have become the material of choice for small precision parts. Common die-cast zinc alloys include the Zn-Al-Cu system (such as Zamak3 and Zamak5) and lead-free zinc alloys (such as ZA8). Zamak3 contains 3.5%–4.3% aluminum and ≤0.03% copper, with a melting point of 380–400°C and excellent fluidity (for spiral lengths ≥900mm). After die-casting, it achieves a tensile strength of 180–220 MPa without heat treatment, making it suitable for manufacturing lightly loaded parts such as toys and decorative items. Zamak5, with its 0.7%–1.2% copper content, increases its strength to 220–260 MPa, its hardness to 80–90 HBW, and its wear resistance is enhanced. It is often used in parts requiring a certain level of strength, such as zipper pulls and bathroom accessories. The lead-free zinc alloy ZA8, with a lead content of ≤0.004%, meets environmental requirements and offers mechanical properties similar to Zamak5, making it suitable for food contact components and medical device housings. The disadvantages of zinc alloy are its high density (6.6~6.8g/cm³) and poor high-temperature performance (strength drops significantly above 100°C), which limits its application in high-temperature environments.
Magnesium alloy is the lightest die-cast alloy, with a density of only 1.7-1.8 g/cm³. Its specific strength and stiffness surpass those of aluminum alloys, making it an ideal choice for lightweighting. Commonly used die-cast magnesium alloys include the Mg-Al-Zn series (such as AZ91D) and the Mg-Al-Mn series (such as AM60B). AZ91D contains 8.3%-9.7% aluminum and 0.3%-1.0% zinc, offering a tensile strength of 230-280 MPa, an elongation of 3%-5%, and medium fluidity (with a spiral length of 500-600 mm). It is suitable for manufacturing lightweight parts such as automotive instrument panels and laptop casings. AM60B, containing 5.5%-6.5% aluminum and 0.2%-0.5% manganese, has an increased elongation of 6%-10% and improved impact toughness. It is often used in components subject to impact loads, such as automotive seat brackets. The disadvantage of magnesium alloy is its poor corrosion resistance (white rust appears after only 24 hours of salt spray test if it is not treated). It needs to be improved through surface treatment (such as anodizing and electroplating), and the smelting needs to be carried out in a protective atmosphere (such as SF6+N2) to prevent oxidation and combustion.
Copper alloys, with their excellent thermal and electrical conductivity and high-temperature strength, are irreplaceable in specific applications. Commonly used copper alloys for die-casting include tin bronze (such as ZCuSn10Pb1 ) and brass (such as ZCuZn38Pb2 ). Tin bronze contains 9%-11% tin and 0.5%-1.5% lead , with a melting point of 900-950 °C, a thermal conductivity of 50-60 W/(m · K) , and a tensile strength exceeding 250 MPa at 300 °C , making it suitable for manufacturing high-temperature and high-pressure components such as radiators and hydraulic valves. Brass, containing 36%-39% zinc and 1%-3% lead , exhibits superior fluidity to tin bronze, excellent processability, and a tensile strength of 300-350 MPa . It is commonly used in plumbing fittings and electrical contacts. The main disadvantages of copper alloys are their high melting point, severe die wear, and die-casting costs three to five times that of aluminum alloys, limiting their use to applications with specialized performance requirements.
