A2 → B2 → L21 ordering transitions in Au–Cu–Al alloys

The critical transition temperatures of A2 → B2 ordering and B2 → L21 ordering in Au–Cu–Al alloys were determined by electrical resistivity measurement and internal friction analysis. The Bragg–Williams–Gorski (BWG) approximation has been widely used for years as a simple mean field method to characterize order–disorder phenomena in alloys. In this article a modified BWG model was employed to analyze the chemical ordering sequence in Au–Cu–Al alloys. Based on the measured critical transition temperatures of A2 → B2 ordering, the critical temperatures of B2 → L21 ordering were calculated. The theoretical predictions were in agreement with the measured temperatures.