Properties of Aluminum Alloys : 1xxx - 8xxx series

Edit: Wuxi XSX Metal Materials Co.,Ltd    Date:Feb 20, 2017

铝棒.jpgPure aluminum is relatively soft. To overcome this, the metal can be alloyed with other metals (alloying elements). Most of the aluminum reaching the marketplace has been alloyed with at least one other element. Depending on alloying elements and heat treatment, aluminum alloy series can exhibit a wide variety of properties, from good appearance, ease of fabrication, good corrosion resistance, to high strength-to-weight ratio, good weldability and high fracture toughness. Selection of the proper alloy series ultimately depends on the application needed and working conditions.

Aluminum Alloy Series 1xxx

This Series (1050, 1060, 1100, 1145, 1200, 1230, 1350 etc.) contains no alloying elements. The proportion of aluminum is 99.3 – 99.9% and the rest is formed by tiny impurities. 1xxx are characterized by excellent corrosion resistance, high thermal and electrical conductivities, low mechanical properties, and excellent workability. Materials of this series are considered non-hardenable alloys and have tensile strengths of 40 – 60 MPa. Moderate increases in strength may be obtained by strain hardening, iron and silicon are the major impurities.

Aluminum Alloy Series 2xxx 

These aluminum alloys (2011, 2014, 2017, 2018, 2124, 2219, 2319, 201.0; 203.0; 206.0; 224.0; 242.0 etc.) main alloying element is copper. Alloys of this series are high strength alloys. The optimum properties such as “strength” is achieved by the heat treatment process. The tensile strength is about 400 MPa on completion of hardening. 

In the solution heat-treated condition, mechanical properties are similar to, and sometimes exceed, those of low-carbon steel. In some instances, precipitation heat treatment (aging) is employed to further increase mechanical properties. This treatment increases yield strength, with attendant loss in elongation; its effect on tensile strength is not as great.

The aluminum alloys in the 2xxx series do not have as good corrosion resistance as most other aluminum alloys, and under certain conditions they may be subject to intergranular corrosion. Aluminum grades in the 2xxx series are good for parts requiring good strength at temperatures up to 150°C (300°F). Except for the code 2219, these aluminum alloys have limited weldability, but some alloys in this series have superior machinability. Code 2024 is the most popular alloy and is commonly used in aircraft construction.

Aluminum Alloy Series 3xxx

These aluminum alloys (3003, 3004, 3105, 383.0; 385.0; A360; 390.0) main alloying element is manganese, generally are non-heat treatable but have about 20% more strength than 1xxx series aluminum alloys. Because only a limited percentage of manganese (up to about 1.5%) can be effectively added to aluminum, manganese is used as a major element in only a few alloys.

Aluminum Alloy Series 4xxx

The major alloying element in 4xxx series alloys (4032, 4043, 4145, 4643 etc.) is silicon, which can be added in sufficient quantities (up to 12%) to cause substantial lowering of the melting range. For this reason, aluminum-silicon alloys are used in welding wire and as brazing alloys for joining aluminum, where a lower melting range than that of the base metal is required. The aluminum alloys containing appreciable amounts of silicon become dark gray to charcoal when anodic oxide finishes are applied and hence are in demand for architectural applications.

Aluminum Alloy Series 5xxx

The major alloying element is magnesium; when it is used as a major alloying element or with manganese, the result is a moderate-to-high-strength work-hardenable alloy. Magnesium is considerably more effective than manganese as a hardener – about 0.8% Mg being equal to 1.25% Mn – and it can be added in considerably higher quantities. Aluminum alloys in this series (5005, 5052, 5083, 5086, etc.) possess good welding characteristics and relatively good resistance to corrosion in marine atmospheres and seawater

However, limitations should be placed on the amount of cold work and the operating temperatures (150°F) permissible for the higher-magnesium aluminum alloys to avoid susceptibility to stress-corrosion cracking.

Aluminum Alloy Series 6xxx

Aluminum alloys in the 6xxx series (6061, 6063) contain silicon and magnesium approximately in the proportions required for formation of magnesium silicide (Mg2Si), thus making them heat treatable. Although not as strong as most 2xxx and 7xxx alloys, 6xxx series aluminum alloys have good formability, weldability, machinability, and relatively good corrosion resistance, with medium strength. Aluminum grades in this heat-treatable group may be formed in the T4 temper (solution heat treated but not precipitation heat treated) and strengthened after forming to full T6 properties by precipitation heat treatment.

Aluminum Alloy Series 7xxx

Zinc, in amounts of 1 to 8% is the major alloying element in 7xxx series aluminum alloys (7075, 7050, 7049, 710.0; 711.0 etc.), and when coupled with a smaller percentage of magnesium results in heat-treatable alloys of moderate to very high strength. The tensile strengths ranging between 450 – 500 MPa may exceed 600 MPa in some cases. These alloys prone to stress corrosion, especially when welded.

Usually other elements, such as copper and chromium, are also added in small quantities. 7xxx series alloys are used in airframe structures, mobile equipment, and other highly stressed parts. Higher strength 7xxx aluminum alloys exhibit reduced resistance to stress corrosion cracking and are often utilized in a slightly overaged temper to provide better combinations of strength, corrosion resistance, and fracture toughness.

Aluminum Alloy Series 8xxx

The 8xxx series (8006; 8111; 8079; 850.0; 851.0; 852.0) is reserved for alloying elements other than those used for series 2xxx to 7xxx. It is mainly used in heat-sink device, lid stock, aluminium foil, and so on. Iron and nickel are used to increase strength without significant loss in electrical conductivity, and so are useful in such conductor alloys as 8017. Aluminum-lithium alloy 8090, which has exceptionally high strength and stiffness, was developed for aerospace applications. Aluminum alloys in the 8000 series correspond to Unified Numbering System A98XXX etc.

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