The Cu±Li±Mg system at room temperature M.H. Braga a,* , L.F. Malheiros b , M. Ha Èma Èla Èinen c a Instituto Superiorde Engenharia do Porto, R. Dr. Roberto Frias, 4200 Porto, Portugal b GMM-IMAT, DEMM, FEUP, Rua dos Bragas, 4099 Porto-Codex, Portugal c Laboratory of Materials Processing and Powder Metallurgy, Helsinki University of Technology, PB 6200, FIN-02015, HUT, Espoo, Finland Accepted 23 August 1999 Abstract The Cu±Li±Mg system still remains very unknown. Mel'nik et al. (Russ. Metall. 3 (1976) 152±156) studied it at 643 K. They considered the existence of a stoichiometric compound Cu 8 Li 2 Mg 15 with an orthorhombic structure. In this work, the Cu±Li±Mg system was studied at room temperature by means of SEM (scanning electron microscopy) / EDS (energy dispersive spectroscopy) and X-ray diffraction. Results were compared with the ones from (Russ. Metall. 3 (1976) 152±156) and with the assessments for the binaries Cu±Li, Cu±Mg and Li±Mg present in the literature (COST-507, Thermochemical database for light metal alloys, in: I. Ansara (Ed.), Concerted Action on Materials Sciences, European Commission DGXII Publ., 1994, pp. 132±134; A.A. Nayeb-Hashemi, J.B. Clark, Phase Diagrams of Binary Magnesium Alloys, ASM International, 1988, pp. 184±194). # 2000 Elsevier Science B.V. All rights reserved. Keywords: SEM/EDS; XRD; Phase diagrams; Thermodynamic assessment 1. Introduction The Cu±Li±Mg system was studied by Mel'nik et al. [1] at 643 K and the samples were examined by X-ray structural analysis. The only ternary com- pound they found in the system contains about 60 at.% Mg, 8 at.% Li and 32 at.% Cu (X-phase), and has an orthorhombic structure with a  5.24 A Ê , b  8.99 A Ê , and c  54.33 A Ê . They also found that the compound Cu 2 Mg (Laves-C15) dissolves lithium approximately up to 13 at.%, that the solubility of Li in CuMg 2 is about 1 at.% and that there is no appreciable dissolu- tion of Cu in hcp-A3 and in bcc-A2. The aim of this study is to determine the con®gura- tion of the ternary phase diagram at room temperature. 2. Experimental The alloys, for the present study, were prepared in Baikov Institute of Metallurgy from Cu 99.96%, Li 99.8% and Mg 99.96% pure elements. Melting of the alloys was performed in a resistance furnace in alu- mina crucibles under a ¯ux, consisting of a salt mixture, 75% LiCl  25% LiF, for preventing Li losses. The alloy melts were poured into a copper round mould with an inner cavity with 16 mm of diameter and cooled down. Afterwards, the ingots were hot squeezed at temperatures between 573 and 623 K to a 50% reduction of their initial thickness using a 160-tonne hydraulic press. Thermochimica Acta 344 (2000) 47±54 * Corresponding author. E-mail address: lfmf@fe.up.pt (M.H. Braga). 0040-6031/00/$ ± see front matter # 2000 Elsevier Science B.V. All rights reserved. PII:S0040-6031(99)00325-1