The terminal solid solubility of hydrogen and deuterium in Zr-2.5Nb alloys

Experimental Results and Theoretical Interpretations of Solvus Relationships in the Zr–H System

“…Pan et al [31] used the DEM technique, employing a range of heating and cooling conditions on unirradiated Zr-2.5Nb pressure tube material to determine the sensitivities of the measured solvus temperatures to variations in these conditions. For TSSD, changes in heating rate and maximum temperature reached during a thermal cycle did not result in noticeable differences as long as the heating rate was the same as the immediately preceding cooling rate.…”

“…The authors conjectured that the shift to higher temperatures may be a secondary effect resulting from the increased applied shear stress making it possible for the shorter dislocation loops formed at an earlier (higher temperature) stage of hydride growth to contribute to auto-twisting. It should be noted that methods based on dilatometry [7,43,52], electrical resistivity [25], DSC [13-15, 24, 41, 44-50], DEM, and IF [31,[38][39][40] all rely on there being a distinct, reproducible feature in the change of the particular property being monitored as function of temperature that can be identified-depending on the direction of the temperature change-with either the initial stages of formation or final stages of dissolution of hydride precipitates in the solid. The solvus compositions obtained in this way are thus terminal solvus compositions, equivalent to what in Chap.…”

“…Using the linear regression fit to the solvi data of Pan et al [31] given in units of atomic fraction (which is approximately numerically the same as r H for the low concentration considered), we obtain at 260°C that c From Leitch and Puls [21] we have for D" w el inc sphere ð Þ¼441:1 Â " V Zr ¼ 6; 176 J/(mol Zr) while RT = 4,432 (J/mol Zr) at 260°C. Inserting these data into Eq.…”

Formation and characterization of hydride blisters in Zircaloy-4 cladding tubes

“…That means it is possible to reach a hydrogen diffusion equilibrium while precipitated hydrides are still available everywhere in the bulk. The DET situation can be described by equating the TSSD at the hot side (at bulk temperature T b ) to the hydrogen in solid solution concentration at the hot side calculated with the BFT resulting hydrogen distribution Pan et al [90] reported two TSSP solvus, named TSSP1 and TSSP2. The TSSP1, which is the commonly reported TSSP by Diferential Scanning Calorimetry, corresponds to the precipitation solvus when no precipitated hydrides are present in the material (nucleation of the first hydrides).…”

Internal Friction Peaks Associated with Hydrides in Zr and Zr-2.5Nb

“…When the hydrogen content in these alloys exceeds the tenninal solid solubility (TSS), the components could be susceptible to a sub-critical crack growth process called delayed hydride cracking (DHC) [l]. Knowledge of both the TSS [2,3] and the morphology and types of the hydrides are important in understanding DHC. The internal friction (IF) technique has been shown to be a powerful tool for studying hydrogen in metals.…”