HT-XRD in the study of Cu-Li-Mg

In a previous study on Cu-Li-Mg system, the authors of the present paper con- cluded that the ternary phase in that system corresponds to CuMg2-xLix (x ~ 0.11), with a hexagonal structure, space group P6222 (180), and lattice parameters a = b = 0.5260 nm, c = 1.3649 nm (1). The structure was refined by the Rietveld method (2). In order to characterize the thermal behaviour of the ternary compound and to assess the Cu-Li-Mg phase diagram (3), HT-XRD measurements were performed on samples whose compositions were close to the one corresponding to the ternary compound. SEM/EDS measurements of the phases' compositions in equilibrium, as well as DSC/DTA heating curves, contributed to the identifi- cation of the transition temperatures and the phases present in equilibrium. It was concluded that the ternary phase decomposes at ~ 702 ± 2K.