This research is developing an understanding of the mechanical properties of cubic forms of trialuminides. Phase stability and ductility of cubic forms of aluminum-titanium-chromium and aluminum-titanium-manganese ternary alloys are the focus of the study. Part of the phase stability work involves the effect of fourth element additions on the extent of the cubic phase (L12) region. This includes the determination of specific element site occupation, atomic size and electronic structure. Micromechanisms associated with the dislocations accounting for plastic flow in the alloys are being studied. It is expected that the research will contribute to the knowledge base needed for the development of new families of low density, heat-resistant alloys that have high specific strengths and excellent oxidation resistance.