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4000 Series Aluminium alloys

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Tibor Majzik

on 2 April 2014

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Transcript of 4000 Series Aluminium alloys

4000 Series Aluminum alloys
These alloys contain silicon (3-49%) as the main alloying ingredient but do not contain copper or magnesium. Their main use stems from their lower melting point, which confers good casting qualities.
Application: Castings, welding wires, architectural app. construction panels, extruded elements
Electromagnetic properties
Electric conductivity depends mostly on the amount of silicon in solution. Values of the order of 35-40% IACS for annealed materials and of 22-35% IACS for solution treated alloys are reported. In the liquid state resistivity is some 10-15 times the resistivity at room temperature.
Magnetic susceptibility is only slightly decreased by silicon.

Mechanical properties
Thermal properties
Thermal expansion is reduced substantially by silicon. Expansion coefficients at subzero temperatures also are some 10-20% lower than those for pure aluminum. Alloys produced by powder metallurgy containing up to 50% Si have even lower expansion coefficients.
Thermal conductivity is of the order of 1.2-1.6 x 10-2W/m/K, the lower values being for the alloys cast in metallic molds or heat treated to retain silicon in solution.

Additional properties
Corrosion resistance. Aluminum-silicon alloys (without copper) have good corrosion resistance in most reagents; only in alkaline solutions which attack silicon as well as aluminum their performance is poor.
Machinability is poor, because the extreme hardness of the silicon combined with the relative softness of the matrix tends to wear the tools very rapidly. In hypereutectic alloys phosphorus additions that improve the silicon distribution improve machinability; but in hypoeutectic alloys phosphorus tends to reduce it.
4000 Series Aluminium alloys
ultimate tensile strengths of 200-400 MPa
ductility from 20 to 2-3%
Compressive strength is higher than tensile by some 10-15%.
Shear strength is approximately 70% of the tensile strength.
Impact resistance is low, but so is notch sensitivity, as is to be expected in alloys that contain a large amount of hard, brittle second phase, often with sharp angles. Impact resistance is improved by spheroidising the silicon.
The modulus of elasticity is of the order of 85-95 GPa, changing with temperature, as does tensile strength. A decrease in damping capacity with aging is reported.
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