5000 series aluminium alloy element and application

5000 series main character

5000 aluminium alloy is a non-heat treatable reinforced aluminium alloy with Mg as the main alloying element. 5000 series aluminium alloys have low density and higher strength than 1000 and 3000 series aluminium alloys, belonging to medium-high strength aluminium alloys, with good fatigue and welding properties, and good resistance to marine atmospheric corrosion. The alloys are mainly used for the production of welded structural components and applications in the field of shipbuilding, silo tanker manufacturing, tanker car or oil tanker manufacturing.

 Mg-Alu binary phase diagram

According to the magnesium-aluminium two-phase diagram, the maximum solubility of magnesium in aluminium at the eutectic temperature is 17.4%, but under the rapid cooling conditions of semi-continuous casting, the solubility is 3%-6%, and when the magnesium content of the alloy exceeds the critical value, the alloy organization produces a(Al)+Mg5Al8 work crystal

5000 Series aluminium main product mechanical property & chemical composition

5000 series aluminium main product include 5083, 5754, 5052

5052 Aluminium Alloy  chemical composition

5083 Alloy Chemical composition

5754  Alloy Chemical composition

Role of Aluminium Alloy Main Elements

5000 series aluminium alloys are mainly composed of Mg, with small amounts of Mn, Cr, Ti and other elements.

The role of Mg elements

Mg mainly exists in solid solution and beta (Mg2Al3 or Mg5Al8), 5 series aluminium alloys are also called non-strengthenable aluminium alloys.

The strength of aluminium alloy increases with the increase of Mg content, the plasticity decreases, and its machining processability becomes poor. the Mg content has a big influence on the recrystallization temperature of the alloy, when the Mg content is less than 5%, the recrystallization temperature decreases with the increase of Mg content, and when the Mg content is more than 5%, the recrystallization temperature increases with the increase of Mg content.

Mg content of the alloy welding performance also has a significant impact, when the Mg content of less than 6%, the alloy’s tendency to weld cracking with the increase in Mg content and reduce; when the Mg content of more than 6%, the opposite; when the Mg content of less than 9%, the strength of the weld with the increase in the Mg content increased significantly, when the plasticity and weld coefficient of a slight decrease; when the Mg content of more than 9%, its strength, plasticity and Welding coefficient are significantly reduced

The role of  Mn elements

The 5000 series usually contains less than 1% Mn, which is present in the product in the chemical composition MnAl6. The addition of Mn to aluminium alloys increases the recrystallisation temperature, prevents crystal coarsening and increases the strength, more so for yield strength. In high magnesium alloys, the addition of Mn can reduce the solubility of Mg in the matrix, reduce weld cracks, and improve the strength of the weld and base metal.

The role of  Cr elements

Cr and Mn role is similar, can improve the base metal and weld strength, reduce weld warmth, improve resistance corrosion performance, but plasticity will be reduced. In the strengthening effect, Cr is not as good as Mn, mixed two elements, the effect is better than one element

The role of  Ti elements

Small amounts of Ti can refine the grains

The effect of Aluminium Alloy Impurity Element

The effect of  Fe elements

Fe forms insoluble compounds with Mn and Cr, which reduces the role of Mn and Cr in the alloy and is prone to machining cracks. In addition, Fe also reduces the corrosion resistance of the alloy, so Fe content should generally be controlled at 0.4% or less, for the wire material, Fe content control at 0.2% or less.

The effect of  Si elements

Si and Mg chemical reaction to form Mg2Si phase, due to excess Mg content, reducing the solubility of Mg2Si in the matrix, so not only the strengthening effect is not great, but also reduces the plasticity of the alloy. Si has a greater effect than Fe, so the Si content should generally be limited to less than 0.5%.

The effect of  Cu elements

Trace amounts of Cu make the corrosion resistance of the alloy worse, so the Cu content should be strictly controlled.

The effect of  Zn elements

Adding a small amount of Zn to high magnesium alloys can improve the tensile strength, but when the Zn content is greater than 0.2%, it will make the mechanical properties and corrosion resistance of the alloy worse

The effect of  Na elements

When the Na content exceeds 0.001%, high magnesium alloys will produce “sodium embrittlement”, leading to serious thermal cracking, therefore, high Mg alloys in the melting, can not be used in the melting of Na-containing flux.

Application View of 5000 series aluminium

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