aluminum alloys 6060, 6063 and AD31

Alloys of aluminum profiles

Изготовление прессованных алюминиевых профилей из сплавов серии 6ххх (самый технологичный и потому популярный из нихAluminium alloy 6060 по стандартам EN и ISO (его частичный аналог – Aluminum alloy AD31 GOST 4784-97) сопровождается сложной комбинацией нескольких термических процессов. Therefore, without a basic understanding of these steel alloys can hardly achieve consistently high quality aluminum profiles.

The role of magnesium and silicon in the alloys 6060, 6063 and AD31

are typical thermally hardenable aluminum alloys. They reach their strength due to heat treatment, instead of strain hardening. Ключевыми элементами этих алюминиевых сплавов являются магний (Mg) и кремний (Si), particles which form Mg2Si. These particles may take several forms, которые обычно объединяют в три основных категории:

  • b "-Mg2Si - the smallest particles Mg2Si, which have a rod shape and make the main contribution to the strength properties, когда имеют большую плотность распределения;
  • b-Mg2Si - enlarged version of the rod-shaped discharge, which grow from β "-category. Эти частицы дают пренебрежимо малый вклад в повышение прочностных свойств;
  • b-Mg2Si - the largest particles Mg2Si, which have a cubic shape and because of its large size do not contribute to increasing the strength properties.

Most of the aluminum alloys 6xxx series, which includes alloys 6060, 6063 and AD31, "Designed" so, чтобы иметь сбалансированные («стехиометрические») содержания магния и кремния, that is, in the proportions, in which they are contained in the magnesium silicide Mg2Si. The figure below shows the boundary line for a balanced chemical composition.

splavy-6000Figure 1 – Comparing the chemical composition of aluminum alloys 6xxx

Excess silicon is preferable, чем избыток магния по следующим причинам:

  • избыточный магний не дает прироста прочностных свойств готового изделия;
  • избыточный магний повышает напряжение течения сплава и делает прессование сплава более трудным;
  • excess silicon increases the efficiency of artificial aging and thus increases the strength properties of the finished product

Effect of alloying

Iron

Iron is always present in aluminum alloys and often forms in combination with silicon and aluminum AlFeSi intermetallics. These intermetallic compounds do not affect the mechanical properties of the alloy, but if not heat treated alloy may adversely affect its moldability. Accurate control of the iron content is important for anodizing profiles. Various iron content may produce differences in shades of color or haze degree anodized surface.

Manganese

Manganese is added to the 6xxx alloys for several reasons.

  • Manganese homogenization reduces the duration, helping to accelerate the conversion of β-AlFeSi particles into α- ALFEU.
  • It prevents the growth of coarse grains during the thermal treatments with separate heating of high-strength alloys, such as, 6061 and 6082.
  • Another is the use of manganese is, Additives that increase its viscous properties of the alloy, as it helps to prevent the loss of free silicon at the grain boundaries.

The most durable aluminum alloy 6xxx series, которые имеют повышенное содержание марганца (более 0,1 %), it reduces the compressibility, and increases sensitivity to quenching.

Chromium

Chromium acts much like manganese, but its effect on the quench sensitivity is more significant.

Copper

  • Добавки меди способствуют улучшению качества механической обработки (резки, фрезеровки и т.п.) прессованных профилей.
  • A small copper content reduces the negative effect of the time delay of the operation of artificial aging to the level of strength properties of high strength alloys, for example, 6061.
  • When the copper content is more 0,2 % decreases the corrosion resistance of alloys 6xxx series.

Zinc

  • Zinc does not have any adverse effect on the mechanical properties of the alloys of the 6xxx series.
  • However, when the content of a 0,03 % Zinc may be the cause of the defect, заключающегося в выборочном (дифференцированном) травлении поверхности профилей при их анодировании.

Thermal transformations in alloys 6060, 6063 and AD31

Сплавы серии 6ххх достигают максимальной прочности в ходе следующей последовательности термических обработок:

  • нагрев в ходе прессования до полного растворения всех частиц в алюминии или отдельный нагрев с той же целью;
  • cooling at a rate, которая зависит от химического состава сплава;
  • aging hardening due to the release of the excess phase particles.

Maximum mechanical properties of aluminum profiles achieved with strict control of temperature during the whole of their production. It is dependent on the temperature characteristics of the particles Mg2Si. The figure 2 shows the temperature history of the production process of aluminum extrusions of alloys 6xxx. All structural transformations occur with magnesium and silicon.

temperaturnyji-cikl-splavov-6xxxFigure 2 – Scheme temperature change during the production of aluminum profiles