ABSTRACT
Aluminum–scandium alloys exhibit a unique combination of high strength and plasticity, corrosion resistance, and weldability. These features are due to their structure and phase composition. The knowledge of phase interactions gained from phase diagrams helps to make the optimum compositions of alloys and choose the best methods for their casting and treatment. These data can be obtained from the appearance of liquidus and solidus surfaces, and from the polythermal and isothermal sections of phase diagrams. Phase diagrams of alloy systems containing scandium were constructed using differential thermal analysis, optical and transmission electron microscopy, X-ray diffraction, electron microprobe analysis, and measurements of microhardness and electrical conductivity. The following alloy systems look promising in the development of new aluminum alloys: Al–Sc–Mg, Al–Sc–Cu, Al–Sc–Si, Al–Sc–Li and Al–Sc–Zr. Some important ternary and quaternary systems are considered. The terminal solubility of scandium in aluminum-based solid solution calculated from the equation describing the solvus is found to be 0.15 " Sc.
