Cast aluminum alloys

Dr. Dmitri Kopeliovich

• Properties of aluminum and its alloys favorable for casting applications
• Disadvantages of aluminum castings
• Classification of cast aluminum alloys
• Characterization of aluminum alloys
• Chemical compositions of some cast aluminum alloys
• Properties of some cast aluminum alloys

• Low melting point;

• Good fluidity of most of the alloys;

• Capability to control grain structure;

• Good surface finish;

• Low solubility of gases (except Hydrogen);

• Ability to be strengthened by heat treatment (precipitation hardening).
  

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• High shrinkage (4-8%) and susceptibility to shrinkage defects (shrinkage porosity);

• High hydrogen solubility;

• Susceptibility to hot cracking;

• Low ductility.

The following casting methods are applicable for casting aluminum alloys:

Sand casting, permanent mold casting, die casting, investment casting, centrifugal casting, squeeze casting and continuous casting.

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Classification of cast aluminum alloys is developed by the Aluminum Association of the United States:

Each cast alloy is designated by a four digit number with a decimal point separating the third and the forth digits.

• The first digit indicates the alloy group according to the major alloying element:

1xx.x aluminum, 99.0% minimum;

2xx.x copper (4%...4.6%);

3xx.x silicon (5%...17%) with added copper and/or magnesium;

4xx.x silicon (5%...12%);

5xx.x magnesium (4%...10%);

7xx.x zinc (6.2%...7.5%);

8xx.x tin;

9xx.x others.

• The second two digits identify aluminum alloy or indicate the alloy purity.

In the alloys of the 1xx.x series the second two digits indicate the level of purity of the alloy – they are the same as the two digits to the right of the decimal point in the minimum concentration of aluminum (in percents): 150.0 means minimum 99.50% of aluminum in the alloy, 120.1 means minimum 99.20% of aluminum in the alloy.

In all other groups of aluminum alloys (2xx.x through 9xx.x) the second two digits signify different alloys in the group.

• The last digit indicates the product form: casting (designated by “0”) or ingot (designated by “1” or “2” depending on chemical composition limits.)

A modification of the original alloy or impurity limits is indicated by a serial letter before the numerical designation. The serial letters are assigned in alphabetical order starting with A but omitting I, O, Q, and X (the letter “X” is reserved for experimental alloys).

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Aluminum-copper cast alloys (2xx.x series)

• Heat-treatable;

• High strength;

• Low corrosion resistance (susceptible to stress-corrosion cracking);

• Low fluidity;

• Low ductility;

• Susceptible to hot cracks.

Applications:

Cylinder heads for automotive and aircraft engines, pistons for diesel engines, exhausting system parts.

Aluminum-silicon-copper/magnesium cast alloys (3xx.x series)

• Heat-treatable;

• High strength;

• Low ductility;

• Good wear resistance

• Decreased corrosion resistance (in copper containing alloys);

• Good fluidity;

• Good machinability (in copper containing alloys).

Applications:

Automotive cylinder blocks and head, car wheels, aircraft fittings, casings and other parts of compressors and pumps.

Aluminum-silicon cast alloys (4xx.x series)

• Non-heat-treatable;

• Moderate strength;

• Moderate ductility;

• Good wear resistance;

• Very good cast properties;

• Good corrosion resistance.

Applications:

Pump casings, thin wall castings, cookware.

Aluminum- magnesium cast alloys (5xx.x series)

• Non-heat-treatable;

• High corrosion resistance;

• Good machinability;

• Good appearance when anodized;

• Moderate cast properties.

Applications:

Sand cast parts.

Aluminum-zinc cast alloys (7xx.x series)

• Heat-treatable;

• Good dimensional stability;

• Good corrosion resistance;

• Poor cast properties;

• Good machinability (in copper containing alloys).

Aluminum-tin cast alloys (8xx.x series)

• Non-heat-treatable;

• Low strength;

• Very good wear resistance;

• Good machinability.

Applications:

Monometal (solid) and bi-metal slide bearings for internal combustion engines and other slide bearings applications.

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(concentration of aluminum - balance)

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(Materials Data)

• Cast aluminum alloy 201.0
• Cast aluminum alloy 208.0
• Cast aluminum alloy 222.0
• Cast aluminum alloy 333.0
• Cast aluminum alloy 356.0
• Cast aluminum alloy 413.0
• Cast aluminum alloy 443.0
• Cast aluminum alloy 514.0
• Cast aluminum alloy 518.0
• Cast aluminum alloy 705.0
• Cast aluminum alloy 713.0
• Cast aluminum alloy 852.0

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• Classification of aluminum alloys
• Temper designation of aluminum alloys
• Effects of alloying elements on properties of aluminum alloys
• Wrought aluminum alloys
• Sintered aluminum alloys
• Fluxes for melting aluminum
• Degassing treatment of molten aluminum alloys
• Aluminum extrusion
• Continuous casting of aluminum based bearing alloys

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