Abstract Aluminum alloyed with approximately 1,000 at. ppm Sc was studied by high-pressure energy dispersive X-ray diffraction in two different states, homogenized and aged to peak microhardness. The microhardness of the aged sample is about three times higher than the microhardness of the homogenized sample (as a result of the formation of nanosize Al 3 Sc precipitates in the aged sample). The results, which were refined using the Rietveld analysis technique, indicate a single cubic phase with no phase transition up to a pressure of 32 GPa. The Vinet equation was used to fit the volume-pressure curve to the equation-of-state. The bulk modulus (B 0 ) is found to be 73 ± 5 GPa, and is equal to the value measured for an unalloyed aluminum sample. The fact that the bulk modulus does not change, despite a large difference in microhardness between the samples, is the result of the different origins of the two quantities
