Фазовая диаграмма системы Au-Zr

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Au-Zr (Gold-Zirconium) T.B. Massalski, H. Okamoto, and J.P. Abriata The equilibrium phases of the Au-Zr system are (1) the liquid, L; (2) the fcc terminal solid solution, (Au), with 7.25 at.% solid solubility of Zr at the L + Au4Zr = (Au) peritectic temperature of ~1065 C; (3) the high-temperature, bcc terminal solid solution, (bZr); (4) the low-temperature cph terminal solid solution, (aZr); (5) the orthorhombic intermetallic compound Au4Zr; (6) the Cu3Ti-type orthorhombic intermetallic compound Au3Zr; (7) the MoSi2-type tetragonal intermetallic compound Au2Zr; (8) the bct intermetallic compound Au10Zr7; (9) the intermetallic compound Au4Zr5 with an unknown crystal structure; (10) the MoSi2-type tetragonal intermetallic compound AuZr2; and ( 11) the Cr3Si-type cubic intermetallic compound AuZr3. The phase diagram of the Au-Zr system is not well established, particularly on the Zr-rich side. The assessed phase diagram covers the full composition range and is based mainly on the work of [48Rau] and [62Sto]. However, lack of experimental data on the liquidus boundaries renders them speculative for compositions above 45 at.% Zr. Because the peritectic temperature is extremely close to the melting point of Au, the L + (Au) two-phase field is very small and is shown as a line. The allotropic a = b transformation temperature in pure Zr is 863 C. There have been no reports on the solubility of Au in solid (Zr). Au is anticipated to have a substantial solubility (~10 at.%) in (bZr), indicating the stabilization of this phase with respect to (aZr). The solubility limit of Au in solid (Zr) has been drawn assuming the AuZr3 compound to be congruently melting and assuming a L = AuZr3 + (bZr) eutectic reaction to occur at ~1200 C. The arrest temperature at about 1220 C between 12 and 19 at.% Zr is identified as the L + Au3Zr = Au4Zr peritectic temperature. No solubility range was reported for Au4Zr. The congruent melting temperature of Au3Zr is ~1560 C. No appreciable solubility range has been reported. An order-disorder transition may occur in this phase. It is not known whether Au2Zr melts congruently or forms by a peritectic reaction. No solubility range has been reported [62Sto]. Au10Zr7 forms by a peritectoid reaction, Au2Zr + Au4Zr5 = Au10Zr7. No solubility range has been reported. Au4Zr5 tentatively has a congruent melting point between 1300 and 1400 C [62Sto]. No solubility range has been reported. AuZr2 has a homogeneity range of about 2 at.% and may form by a peritectoid reaction, Au4Zr5 + AuZr3 = AuZr2 at about 1100 C. Little is known about AuZr3, which is tentatively indicated as a line compound that melts congruently at ~1200 C. 48Rau: E. Raub and M. Engel, Z. Metallkd., 39, 172-177 (1948) in German. 62Sto: E. Stolz and K. Schubert, Z. Metallkd., 53, 433-444 (1962) in German. Published in Phase Diagrams of Binary Gold Alloys, 1987, and Bull. Alloy Phase Diagrams, 6(6), Dec 1985. Complete evaluation contains 1 figure, 2 tables, and 15 references. 1