Abstract
The precipitation kinetics of a laboratory alloy (AlCu4.3) is compared with that of a commercial alloy AW2024 (AlCu4Mg) by continuous and isothermal dilatometry and differential scanning calorimetry (DSC). The precipitation and decomposition sequence are demonstrated by means of DSC. Precipitation of θ ′ causes an accelerated thermal expansion of AlCu4.3 complemented by retarded expansion in the dissolution temperature range. Dilatometry results from several temperature scan rates are analysed by the Kissinger method to give apparent activation energies and rate constants for the precipitation of θ ′ in AlCu4.3. The activation energy of formation varies from 80 to 100 kJ/mol, while that for dissolution amounts to 200 kJ/mol. The sequence of precipitation of the S phase in solutionized 2024 aluminium is more complex, but shows only little effect on the thermal expansion.

Key words
Al-Cu alloys, precipitation kinetics, dilatometry, differential scanning calorimetry

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