Solid Solution Equilibria in the Zirconium-Hydrogen System¹

Abstract

The solubility of hydrogen in zirconium has been determined as a function of temperature and hydrogen pressure in the temperature range 6000 to 9000C. The solubilities obtained for a hydrogen pressure of one atmosphere are about ten per cent higher than those obtained by Hall, Martin, and Rees. 9 A partial binary phase diagram is presented and correlated insofar as possible with previous x-ray work. In particular, we have indicated existence of a new phase, ' , in the composition range 59.4 to about 61 atom per cent bydrogen. The zirconium-rich boundary of this phase is invariant with temperature. This phase is apparently separated frvm the C phase (which includes the composition ZrH 2 ) by a very narrow twophase field which has generally escaped detection and was only indirectly established in this paper.

High-temperature thermodynamic functions for zirconium and unsaturated zirconium hydrides

“…The hydrogen-activity data so chosen as a basis were those reported graphically by LaGrange, Dykstra, Dixon, and Merten [8] at T = 1,073.2 and 13 compositions ( x =0.05 to 1), and those reported in tabular form by Edwards, Levesque, and Cubicciotti [5] for values of x of 0.650, 0.733, 0.815, and 0.894 and at 8 temperatures over the range T = 1,023 to 1,173. (These points all lie in the β field.)…”

“…Plots of the hydrogen-pressure data of Edwards et al [5] for the four compositions from x = 0.650 to x = 0.894, used above, gave without trend almost identical values which averaged false(trueH¯2β−H2°false)1123=−40,500. Ells and McQuillan [6] measured α2β at one high concentration of hydrogen ( x =0.66) from approximately 875 to 1,035 °K, leading to a value which when corrected to 1,123 °K by the enthalpy data gave false(trueH¯2β−H2°false)1123=−37,500.…”

“…The enthalpy data were obtained by Douglas and Victor [16] for the compositions x =0.701, 0.999, and 1.071, but the values show serious inconsistencies between two of the sample compositions,14 and therefore were given no weight in deriving properties in this field. Hydrogen-activity values in the ( β + δ ) field were reported as follows: by Edwards et al [5] for x =1.222 at 973, 1,023, 1,073, 1,098, 1,123, 1,133, 1,138, and 1,148 °K; by LaGrange et al [8] for several compositions at 843, 889, 919, 967, 1,022, and 1,073 °K. The values of the two sets of workers, which disagree somewhat at the lower temperatures, show excellent agreement as well as smooth temperature dependence at and above 1,023 °K, and were used to define the adopted values in this higher temperature range.…”

“…Experimental data on the thermodynamic and other physical properties of the system have been published by a number of investigators. Some of these have measured equilibrium pressures of hydrogen in certain ranges of temperature and composition [1, 2, 3, 4, 5, 6, 7, 8]. 1 The rates of diffusion of hydrogen in the metal have been studied [9, 7].…”

“…The composition range covered is from Zr to ZrH 1.25 , and the temperature range from 298.15 to 1,200 °K. (Though thermodynamic data are available for higher temperatures [1] and higher hydrogen contents [2,3,5,8,10], these were omitted from consideration because of their generally inferior precision or lack of agreement.) The coexistence of phases in equilibrium is in a sense accidental, and the theoretical interest in the system therefore centers mainly in the properties of individual phases.…”