The aluminium-copper-gold ternary system

Abstract

Despite Au, Al and Cu being individually very well-known elements, their ternary phase diagram has not been studied in as much detail as those of many other Au-containing ternaries. Here we review what is known, and consider the prospects for technological exploitation of some of the ternary compositions. The components of greatest interest in Al-Au-Cu may be the P-phases, at least two of which have shape memory properties. Of these, 'Spangold', which has the nominal stoichiometry Au7Cu5Al4, has received some attention for jewellery applications, while the edge compound Cu3Al is a well-known shape memory composition with corresponding specialised industrial uses. The properties of other beta-phase compositions in the system have been scarcely investigated. The system also contains an extensive gamma-phase, Al4AuxCu9-x, where x ranges from 0 to similar to 6.5, and the purple gold phase AuAl2.