Aluminum (AI) die casting alloys have a specifc gravity of approximately 2.7 g/cC, placing them among the lightweight structural metals. The majority of die castings produced worldwide are made from aluminum alloys.
Six major elements constitute the die cast aluminum alloy system: silicon, copper, magnesium, iron, manganese, and zinc. Each element affects the alloy both independently and interactively.
This aluminum alloy subsection presents guideline tables for chemical composition, typical properties, and die casting machining and finishing characteristics for 11 aluminum die casting alloys. This data can be used in combination with design engineering tolerancing guidelines for aluminum die casting and can be compared with the guidelines for other alloys in this section and in the design engineering section.
Alloy A380 (ANSI/AA A380.0) is by far the most widely cast of the aluminum die casting alloys, offering the best combination of material properties and ease of production. It may be specifed for most product applications. Some of the uses of this alloy indlude electronic and communic ations equipment, automotive components, engine brackets, transmission and gear cases, appliances, lawn mower housings, furniture components, hand and power tools.
Alloy 383 (ANSV/AA 383.0) and alloy 384 (ANSUAA 384.0) are alternatives to A380 for intricate components requiring improved die flling characteristics. Alloy 383 offers improved re sistance to hot cracking (strength at elevated temperatures).
Alloy A360 (ANSU/AA A360.0) offers higher corrosion resistance, superior strength at elevated temperatures, and somewhat better ductility, but is more difficult to cast.
While not in wide use and difcult to cast, alloy 43 (ANSI/AA C443.0) offers the highest ductility in the aluminum family. It is moderate in corros ion resistance and often can be used in marine grade applications. Alloy A13 (ANSI/AA A41 3.0) offers excellent pressure tightness, making it a good choice for hydraulic cylinders and pressure vessels. Its casting characteristics make it useful for intricate components.
Alloy 390 (ANSUAA B390.0) was develloped for automotive engine
blocks. Its resistance to wear is excellent; its ductility is low. It is used for die cast valve bodies and compressor housings in pistons.
Alloy 218 ANSUAA 518.0) provides the best combination of strength, ductility, corrosion resistance and finishing qua lities, but it is more difficult to die cast.
Machining characteristics vary somewhat among the commercially available aluminum die casting alloys, but the entire group is superior to iron, steel and titanium. The rapid solidifcation rate associated with the die casting process makes die casting alloys somewhat superior to wrought and gravity cast alloys of similar chemical composition.
Alloy A380 has better than average machining characteristics. Alloy 218, with magnesium the major alloying element, exhibits among the best machinability. Alloy 390, with the highest silicon content and free silicon constituent, exhibits the lowest.
Surface Treatment Systems Surface treatment systems are applied to aluminum die castings to provide a decorative finish, to form a protective barrier against environmental exposure, and to improve resistance to wear. Decorative fnishes can be applied to aluminum die castings through
painting, powder coat finishing, polishing, epoxy finishing, and plating. Aluminum can be plated by applying an initial immersion zinc coating, followed by conventional copper-nickelchromium plating procedure similar to that used for plating zinc metal/alloys. Protection against environmental corrosion for aluminum die castings is achieved through painting, anodizing. chromating. and inidite coatings. Improved wear resistance can be achieved with aluminum die castings by hard anodizing.
Where a part design does not allow the production of a pressure-tight die casting through control of porosity by gate andoverflow die design, the location of ejector pins, and the reconfguration of hard-to-cast features, impregnation of aluminum die castings can be used. Systems employing anaerobics and methacrylates are employed to produce sealed, pressure tight castings with smooth surfaces.
| ALUMINUM ALLOY CHARACTORISTICS | ||||
|---|---|---|---|---|
| Aluminum die casting alloys | A360 | A380 | A383 | A413 |
| Hardness | 75 | 80 | 75 | 80 |
| Elongation (% in.2 in.) | 2.5 | 3.5 | 3.5 | 2.5 |
| Shear Strength (ksi) | 28 | 28 | - | 25 |
| Tensile Yield Strength (ksi) | 25 | 23 | 22 | 21 |
| Ultimate Tensile Strength (ksi) | 44 | 46 | 45 | 43 |
| Thermal Conductivity | 65 | 56 | 56 | 70 |
| Electrical Conductivity (% copper) | 30 | 27 | 23 | 0.099 |
| Density (weight) Lbs./ in.3 | 0.095 | 0.099 | 0.099 | 0.096 |
| ALUMINUM ALLOY ADVANTAGES | ||||
|---|---|---|---|---|
| Aluminum die casting alloys | A360 | A380 | A383 | A413 |
| (1= most desirable, 5= least desirable): | ||||
| Pressure Tightness | 2 | 2 | 2 | 1 |
| Die Filling Capacity | 3 | 2 | 1 | 1 |
| Anti-Soldering to Die | 2 | 1 | 2 | 1 |
| Corrosion Resistance | 2 | 4 | 3 | 2 |
| Machining ease & quality | 3 | 3 | 2 | 4 |
| Strength at high temperatures | 1 | 3 | 2 | 3 |
| Material cost | 3 | 1 | 2 | 4 |
| ALUMINUM ALLOY MATERIALS | ||||
|---|---|---|---|---|
| Aluminum die casting alloys | A360 | A380 | A383 | A413 |
| Silicon (Si) | 9.0-10.0 | 7.5-9.5 | 9.5-11.5 | 11.0-13.0 |
| Iron (Fe) | 2.0 | 2.0 | 1.3 | 2.0 |
| Copper (Cu) | 0.6 | 3.0-4.0 | 2.0-3.0 | 1.0 |
| Manganese (Mn) | 0.35 | 0.5 | 0.5 | 0.35 |
| Magnesium (Mg) | 0.4-0.6 | 0.10 | 0.10 | 0.10 |
| Nickle (Ni) | 0.50 | 0.50 | 0.30 | 0.50 |
| Zinc (Zn) | 0.50 | 3.0 | 3.0 | 0.50 |
| Tin (Sn) | 0.15 | 0.35 | 0.15 | 0.15 |
| Others | 0.25 | 0.50 | 0.50 | 0.25 |
| Aluminum (Al) | Balance | Balance | Balance | Balance |
Aluminum Die Cast Parts comply with the EU RoHS standards
| ALUMINUM ALLOY MATERIALS | ||||
|---|---|---|---|---|
| Tensile strength, psi x 1000 | A360 | A380 | A383 | A413 |
| Yield strength, psi x 100 (0.2 pct offset) | 75 | 80 | 75 | 80 |
| Shear strength, psi x 1000 | 23 | 30 | 23 | ？ |
| Fatigue strength, psi x 1000 | 28 | 37 | 20 | 31 |
| Elongation, pct in 2 in. | 20 | 25 | 14 | 7 |
| Hardness (Brinell) | 3.50 | 15 | 3.0 | 10 |
| Specific gravity | 80 | 91 | 63 | 82 |
| Weight, lb/cu. in. | 2.71 | 8.30 | 1.80 | 6.60 |
| Melting point (liquid), �F | 0.098 | 0.305 | 0.066 | 0.24 |
| Thermal conductivity, CG5 | 1100 | 1670 | 1105 | 728 |
| Thermal expansion, in./in./�F x 106 | 0.23 | 0.21 | 0.16 | 0.27 |
| Electrical conductivity, | 12.1 | 12.0 | 15.0 | 15.2 |
| pct of copper standard | 27 | 20 | 10 | 27 |
| Modulus of elasticity, psi x 106 | 10.3 | 15 | 6.5 | ？ |
| Impact strength (Charpy), ft/lb | 3.0 | 40 | 2.0 | 43.0 |
