The relative difference between the average dislocation density of 6061Al-15vol% SiC composites investigated by two independent methods (namely hardness, H, and differential scanning calorimetry, DSC), is discussed. They are interpreted in terms of the "actual" temperature at which the measurements are made with each technique. The present analysis accounts for the high microstructural stability of these composites at elevated temperatures. (C) 2003 Kluwer Academic Publishers.