Aluminium alloys EN AW 6028 and EN AW 6262 (Al-Mg-Si) are among those with a
good combination of strength, machinability and corrosion resistance. The chemical
composition - Al: 90–98% by weight, Mg: 0.6–1.5% by weight, Si: 0.4–1.5% by weight,
Cu: 0.1–0.6% by weight, Fe: up to 0.7% by weight - allows heat treatment and thus an
improvement of the mechanical properties. They are mainly used in the construction,
automotive, aerospace and machine component industries.
The aim of the thesis is to carry out a thermodynamic characterisation of EN AW 6028
and EN AW 6262 alloys. Thermodynamic calculations of the equilibrium and nonequilibrium
states have been carried out with the Thermo-Calc program and phase
diagrams and Scheil diagrams have been drawn on the basis of the obtained
calculations. Differential scanning calorimetry (DSC) was also performed for the cast
and homogenised samples using a NEZTSCH DSC 404 F3 Pegasus. The
characteristic temperatures and the corresponding enthalpies of formation of the
individual phases were read.
Thermodynamic calculations for EN AW 6028 and EN AW 6262 alloys show that at the
solidification, primary α-Al mixture crystals form first, followed by eutectics with Mg3Bi2,
Al15Si2Mn4 and Mg2Si phases. The microstructure shows the primary dendritic grains
of the primary α-Al mixture crystals and the eutectics along the crystal boundaries.
After homogenisation, the Mg2Si phase is no longer observed, but increased porosity
appears. Solidification takes place between 700 and 470 °C.
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