Characterization of ordering transitions in Au–Cu–Al alloys

A2 → B2 → L21 ordering transitions in Au–Cu–Al alloy were investigated by a combination of thermal analysis, electrical resistivity and internal friction technique. Results show that A2–B2 ordering transition was accompanied by volume change and thermal effects, features of the first-order transformation. While B2–L21 ordering transition belongs to the second-order transition, since only the change of Cp (heat capacity) was observed. Critical temperatures of A2–B2 and B2–L21 ordering transitions were appropriately determined by internal friction measurement. Comparison among different techniques was presented, and the applicability of these techniques was suggested. The mechanics of ordering transition in Au7Cu5Al4 alloy was also discussed.