Thermal hardening of aluminum alloys 6xxx

Tempering aluminum profiles on the press

cooling rate aluminum profiles – quenching – immediately after exiting the press should be fast enough, to delay the magnesium and silicon in solid solution. This achieves the maximum mechanical property profile of the material due to their isolation in the subsequent hardening of aging.

The required rate of cooling of the solid solution alloying elements – magnesium and silicon in aluminum – для обеспечения эффекта закалки зависят от размеров поперечного сечения алюминиевого профиля и способов его охлаждения:

  • calm air,
  • fans,
  • water mist,
  • water cooling or spreyernym
  • in water stream.

Figure and table shows the minimum allowable cooling rate profiles for various aluminum alloys of the 6xxx series. For aluminum alloy profiles 6060 (aluminum alloy AD31) обычно бывает достаточно охлаждения на спокойном воздухе или вентиляторами, whereas the profiles of alloy 6061 spreyernoe necessary cooling water or cooling water flow.

закалка алюминиевых профилей из сплавов 6060/АД31 и 6061/АД33

закалка алюминевых профилей из сплавов 6060/АД31, 6061 и др.

Aging aluminum alloys

Aging 6xxx series alloys produced to improve the mechanical properties of aluminum profiles. The degree of this increase depends on the properties of the alloy and aging conditions. Эти условия различаются для:

  • natural aging, that occurs “by itself” at room temperature, and
  • artificial aging, is conducted at elevated temperatures, near 160-200 oC.

Strength alloys 6xxx series is directly related to their ability to resist the movement of dislocations during deformation. Upon the application of stress to the material formed in it and move dislocation. With increasing number of stress and dislocation density, moving in the material, increases until, till, finally, the material is not destroyed.

The movement of dislocations is inhibited due to the presence of particles Mg2Si and thus the strength of aged aluminum alloy increases. The dimensions and density of these particles are controlled aging parameters. A small amount of fine particle β”-Mg2Si little can be done, to stop the deployment of, which move through the material, but when a lot of them, they hinder the movement of dislocations, and this increases the strength of the material.

Если же частицы вырастают слишком большими (β’-Mg2Si и b-Mg2Si), they become too small due to the limited content of Mg and Si in the aluminum. In this case, the dislocation easily circumvent these particles and the strength of the material is reduced.

This shows a schematic graph of a typical artificial aging in the figure below.

thermal treatment of the alloy alyuminevogo 6060 (/АД31)
thermal treatment of the alloy alyuminevogo 6060 (AD31)

Peak strength properties is achieved when a large number of fine particles β”-Mg2Si. For alloys 6xxx typical parameters are the temperature artificial aging 170 ° C when exposed 8 hours or 185 ° C when exposed 6 hours.

T states aluminum alloys

Different parameters correspond to embodiments of aging различные обозначения состояния алюминиевых сплавов:

  • Т1 – охлажденый после прессования до комнатной температуры и естественно состаренный;
  • Т4 – после прессования закаленный с отдельного нагрева и естественно состаренный;
  • Т5 – охлажденный после прессования до комнатной температуры и искусственно состаренный до максимума прочностных свойств;
  • T6 – hardened after pressing with a separate heating and artificially aged to peak strength properties.

To designate other aging treatments, are specifically designed to obtain mechanical properties, which differ from the maximum strength properties. for instance, state T52 and T591 are applied to aluminum profiles, which are subject to bending, T7 and the state - for profiles, which are applied at elevated temperatures.

Stretching and maturing this mass profiles

The usual practice of manufacturing aluminum extrusions involves stretching them from 0,5 % by 3 % и затем вылеживание с задержкой на сутки искусственного старения для профилей из малолегированных сплавов 6ххх (не более 0,9 % Mg2And), for example, Aluminum alloys AD31, 6060 and 6063. This contributes to the achievement of optimum mechanical properties after aging profiles.

Однако такая задержка для более высокопрочных алюминиевых сплавов (содержание Mg2Si more 0,9 %), for example, 6061, It may lead to reduced mechanical properties of the material of aluminum profiles. These alloys contain copper in an amount of not less 0,1 %, which counteracts the influence of delay artificial aging on the final mechanical properties of thermally toughened aluminum profiles.