This work presents an experimental study of combustion characteristics of micron-sized aluminum particles in the transition regime under constant volume combustion experiments. Burning velocities were estimated from the measured pressure traces using both a simplified model for aerosol combustion on closed spherical bombs and a semi-empirical correlation, and compared to previous literature. Flame temperatures were measured by bi-color pyrometry and indicate that for particles smaller than 12 m, the flame moves closer to the particle's surface, since flame temperatures were close to aluminum boiling point. For 17:9 µm particles, flame temperatures were close to predicted adiabatic flame temperature and alumina vaporization-dissociation temperature, indicating a classical vapor phase flame under a diffusion-controlled mechanism. However, spectroscopy measurements did not detect significant reductions on molecular AlO emissions for ner particles. This indicates a still very significant presence of vapor phase reaction for powders with a Sauter mean diameter at least as large as 7 µm, which is further supported by the presence of nanometric spheres in the combustion residues, since alumina formed under a vapor phase reaction is expected to condensate into nanometric droplets.