Aluminum-rich alloys that contain a few atomic percent of a transition metal and a rare earth element belong to the class of marginal glass-forming alloys that is characterized by a critical cooling rate for amorphization of the order of 106K/s. Many representatives of this class of alloys do not have a resolved glass transition upon reheating and instead form a dispersion of nanometer sized Al-crystallites within an amorphous matrix during a primary crystallization reaction. For the amorphous Al-base systems the high undercooling for glass formation appears to be controlled largely by the suppression of growth of nuclei formed during rapid melt quenching. However, this same kinetic control also provides the foundation for the development of the high number density (1022 m−3) of nanocrystals (diameter <20 nm) during primary crystallization. With alternate synthesis routes basedupon solid state alloying resulting from intense deformation, the kinetic pathways to glass formation has been altered to avoid the nanocrystalline Al-dispersions. Moreover, quantitative transmission electron microscopy and temperature-modulated calorimetry have been used to extract the endothermic glass-transition signal from exothermic contributions due to the nanocrystal formation. The results are direct proof that the rapidly quenched amorphous alloys are truly vitreous and are further utilized to estimate the thermodynamic excess functions. These developments present new opportunities for controlling crystallization in multicomponent glasses.