Фазовая диаграмма системы K-Na

К оглавлению: Другие диаграммы (Others phase diargams)

K-Na (Potassium-Sodium) C.W. Bale There are four stable condensed phases in the K-Na system at 1 atm pressure ( above 240 K): (1) the liquid, L; (2) the peritectically melting stoichiometric solid KNa2; (3) solid Na; and (4) solid K. There is limited solid solubility of Na in (K) and vice versa. At pressures above 40 kbar and temperatures above 420 K, limited data suggest the existence of another intermetallic phase, K2Na, but the evidence is not conclusive. The assessed K-Na phase diagram is taken directly from the detailed thermal analysis of [69Ott], except for the melting points of the pure metals, which are the currently accepted values. This diagram is in good agreement with [ Hansen]. The solvus lines and the subeutectic metastable liquidus lines were calculated using thermodynamic parameters. The calculated values of the liquidus are in excellent agreement with the limiting slopes of the solidus lines of [69Ott], which are estimated to be 0.10 and 0.033 at.%/K at pure K and pure Na, respectively. Thus, the liquidus and solidus data are thermodynamically self- consistent in the dilute regions, giving credence to the values of [69Ott] reported in the other regions. For all compositions, the agreement of the liquidus temperature is always within 1 K and generally less than 0.5 K. The solvus lines and the metastable subeutectic liquidus lines also were calculated. Halt behavior as a function of pressure is similar to that of elemental Cs. The temperature of the peritectic and eutectic halts increases as the pressure increases, but with different slopes, so that the two invariant points merge at approximately 35 kbar. 69Ott: J.B. Ott, J.R. Goates, D.R. Anderson, and H.T. Hall, Jr., Trans. Faraday Soc., 65, 2870 (1969). Published in Bull. Alloy Phase Diagrams, 3(3), Dec 1982. Complete evaluation contains 3 figures, 4 tables, and 32 references. 1