  A multidisciplinary approach is presented to analyse the precipitation
process in a model Al-Cu alloy. Although this topic has been extensively
studied in the past, most of the investigations are focussed either on
transmission electron microscopy or on thermal analysis of the processes. The
information obtained from these techniques cannot, however, provide a coherent
picture of all the complex transformations that take place during decomposition
of supersaturated solid solution. Thermal analysis, high resolution
dilatometry, (high resolution) transmission electron microscopy and density
functional calculations are combined to study precipitation kinetics,
interfacial energies, and the effect of second phase precipitates on the
mechanical strength of the alloy. Data on both the coherent and semi-coherent
orientations of the {\theta}"/Al interface are reported for the first time. The
combination of the different characterization and modelling techniques provides
a detailed picture of the precipitation phenomena that take place during aging
and of the different contributions to the strength of the alloy. This strategy
can be used to analyse and design more complex alloys.
