Wrought aluminum alloys: chemical composition and application

Categories and classes

Wrought and cast alloys

All aluminum alloys fall into two main categories:

  • wrought alloys and
  • casting alloys.

Heat-strengthening and deformation of the reinforcement

Further separation into two classes, each of these categories based on the main mechanism of improving their mechanical properties, namely, due to:

  • heat treatment or
  • deformation processing.

Many alloys have the ability to change its properties under the effect of heat treatment, which is based on the dependence of the solubility of the various phases of the temperature. These heat treatments include [1]:

  • heat treatment to create a solid solution (heating for hardening);
  • hardening (rapid cooling, usually to “room” temperatures (workshop temperatures));
  • hardening by aging (due to precipitation of hardening phases).

such alloys, as a deformable, and casting, called heat-reinforcing.

Many other wrought alloys prepared improving its properties is not by thermal treatment, and by strain hardening (work-hardening). This type of hardening is achieved as a result of plastic deformation of the product with a certain degree of plastic deformation (drawing). This typically occurs in combination with various embodiments of annealing to achieve the optimum combination for the product strength characteristics. These alloys are called strain hardening, and thermally neuprochnyaemymi.

Series wrought alloys

According to the international designation system, all wrought aluminum alloys are subdivided into eight series (groups), depending on the alloying system of these alloys: 1xxx, 2xxx, 3xxx, 4xxx, 5xxx, 6xxx, 7xxx and 8xxx.

series 1hhh

properties

  • Brands include unalloyed aluminum with a purity 99,00 % and higher (table 1).
  • Characterized by high corrosion resistance, high thermal and electrical conductivity, low mechanical properties and very good formability.
  • Iron and silicon are the major impurities.

Table 1 – Chemical composition of 1xxx series aluminum alloys [2]

application

Used mainly electrical and chemical industries.

series 2xxx

properties

  • The main alloying element is copper, often with magnesium as an additional supplement (table 2).
  • These alloys require quenching to obtain their optimal properties. In after quenching and natural aging of their mechanical properties are close, and sometimes exceed, properties of low-carbon steels.
  • Less heat treatment is applied to artificial aging to further enhance the mechanical properties. This treatment increases the yield strength with a noticeable loss in elongation, wherein the effect on tensile strength is small.

Table 2 – Chemical composition of 2xxx series aluminum alloys [2]

  • 2xxx series alloys do not have a high corrosion resistance, which is typical for most aluminum alloys, and under certain circumstances may be subjected to intergranular corrosion.
  • Therefore, the surface of sheets of these alloys is usually clad (coated) with aluminum grades, Aluminum-magnesium alloys of the 6xxx series or alloy, which contains 1 % zinc. such a coating, It is generally from 2,5 by 5 % the total thickness on each side, It provides galvanic protection within the sheet material and, thereby, significantly increases its resistance to corrosion.

application

  • 2xxx series alloys are particularly well suited for parts and structures, which require a high ratio of "strength-to-weight".
  • Used in the manufacture of wheels of trucks and planes, suspension parts truck, fuselages and wings of airplanes, bearing elements of buildings and structures, as well as those parts, which require high strength at temperatures up to 150 oC.
  • On the image 1 shows the relationship between some of the most commonly used alloys of the 2xxx series.


Figure 1 - Relationships between popular alloys in the 2xxx series (Al-Cu) [1]

series 3hhh

properties

  • The main alloying element is manganese (table 3).
  • These alloys are generally thermally neuprochnyaemymi, but have strength 20 % higher, what brand of aluminum from series 1xxx.
  • The effectiveness of adding manganese to aluminum is very limited – to about 1,5 %.
  • Therefore, manganese is the principal alloying element in minor amount only alloys.

application

  • popular alloy 3003, It is widely used as an alloy in a large number of products with medium requirements for strength and high requirements for forming ability.
  • They are also popular alloys 3004 and 3104. They are used for the manufacture of beverage cans buildings – “beer cans”. Covers made of these alloy cans 5182 5xxx series (cm. below).

Table 3 – Chemical composition of 3xxx series aluminum alloys [2]

series 4XXX

properties

  • The main alloying element is silicon, which is added in very large quantities (up to 12 %) (table 4). This is done, to significantly reduce the alloy melting range without embrittlement.
  • For this reason, aluminum-silicon alloys are used as wire and aluminum alloys for brazing, when it required a lower melting temperature interval, than that of base metal.

Table 4 – Chemical composition of 4xxx series aluminum alloys [2]

  • Most of the alloys in this series are thermally neuprochnyaemymi. However, when they are used for sealing of thermally hardened alloys, they capture their part of the alloying elements and to some extent also receive thermal hardening.
  • These aluminum alloys, that have a significant silicon content, after anodizing become dark, from dark gray to black. Therefore, they are not used for soldering products, subjected to anodization, if they are subject to requirements on appearance.

application

  • Main application – in the form of wire solder for svraki and aluminum alloys
  • Alloy 4032 It has a low coefficient of thermal expansion and high wear resistance. Therefore it is well suited for the manufacture of forged pistons engines.

5xxx series

properties

  • Magnesium is the main alloying element in 5xxx series alloys (table 5). When it is used as a main alloying element, or simultaneously with Mn, the result is a strain hardenable aluminum alloy with strength levels from medium to high.
  • Magnesium is significantly more effective for increasing the strength level, than manganese. Near 0,8 % magnesium equivalent 1,25 % manganese and, Moreover, Magnesium may be added in significantly higher quantities.

Table 5 – Chemical composition of 5xxx series aluminum alloys [2]

application

  • Alloys of this series exhibit good weldability and high corrosion resistance in sea atmosphere. However, there are some limitations on the amount of cold work hardening and a safe operating temperature, which are allowed for alloys with a high magnesium content (over ~ 3.5 % for operating temperatures above ~ 65 ºС) in order to, to avoid the tendency to cracking from stress corrosion.
  • On the image 2 shows the relationship between the most commonly used alloys 5xxx series.

Figure 2 - Relationships between popular 5xxx series alloys (Al-Mg) [1]

series 6hhh

properties

  • Alloys of this series contain silicon and magnesium approximately in the proportions, which are required for the formation of magnesium silicide (Mg2And), which makes them thermally hardened (table 6).

Table 6 – Chemical composition of 6xxx series aluminum alloys [2]

application

  • 6xxx series alloys are not as strong as most 2xxx series alloys and 7xxx. They have an average level of strength and are characterized by good moldability (including, compressibility), good weldability, good machinability and good corrosion resistance.
  • These heat-hardening alloys can achieve their strength properties:
    – able T4 - hardening, но без термической обработки на ускоренное старение (естественное старение); прочностные свойства не достигают максимально возможных значений;
    в состоянии Т6 – закалка и термическая обработка для ускоренного старения (искусственное старение); прочностные свойства достигают максимально возможных значений.
  • On the image 3 shows the relationship between the most commonly used aluminum alloys 6xxx series.

Figure 3 - Relations between the popular aluminum alloys
серии 6ххх (Al-Mg-Si)

series 7hhh

properties

  • Zinc in an amount of 1 by 8 % is the main alloying element of 7xxx series aluminum alloys together with a lower magnesium content (table 7).
  • These alloys are thermally hardening with a level of strength from medium to very high.
  • Usually other elements, such as copper and chromium are also added in small amounts.
  • Addition of small amounts of scandium as improve their properties.

application

  • 7xxx series alloys are used in load-bearing aircraft structures, heavy vehicles and other hard structures of loaded.

Table 7 – Chemical composition of 7xxx series aluminum alloys [2]

  • High strength 7xxx series alloys exhibit a reduced resistance to cracking due to corrosion under stress and are often used in perestarennom able to provide the best combination of strength, corrosion resistance and fracture toughness.
  • On the image 4 shows the relationship between some commonly used alloys of the 7xxx series.

Figure 4 - Relationships between popular 7xxx series alloys (Al-Zn-Cu-Mg-Cr)

series 8hhh

The 8xxx series combines alloys with different types of chemical composition (table 8).

Table 8 – The chemical composition of aluminum alloys of the 8xxx series [2]

Increased resistance to high temperatures is achieved through the use of dispersion-hardened Al-Fe-Ce alloys (example - alloy 8019) or Al-Fe-V-Si alloys (example - 8009), which are made of powder metallurgy technology.

Lower density and higher stiffness can be achieved in alloys, containing lithium (example - 8090). Alloy 8090, which is thermally hardenable due to aging, replaced medium and high strength alloys of the 2xxx and 7xxx series in some products of the aerospace industry (for example, components of helicopters).

alloys 8030 and 8176 specially designed for aluminum wires and cables (see. aluminum wiring)

European and American alloys

As can be seen, Not all aluminum alloys, are presented in Figures 1-4, present in the tables 1-8. This is due to the fact, that the European and American approaches are slightly different to the alloying of aluminum alloys. for instance, alloys 6060 and 6082 are “European” and are not used in North America. On the other hand alloys 6063 and 6061 They are popular in North America and much less used in Europe.

Sources:

1. Aluminum and Aluminum Alloys / J.R. Davis // Alloying: Understanding the Basics – ASM International, 2001

2. DIN EN 573-3:2009

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