| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 1278390 | International Journal of Hydrogen Energy | 2015 | 10 Pages |
•We continue our solubility determinations in metal hydride formers; the H–Ti system.•Our motivation is the scarce and scattered data regarding the solvus of H–Ti system.•We used the sensitive DSC technique to determine the complexity of the solvus line.•Tendencies in the solubility led to different solvus enthalpies for γ and δ phases.•Accurate values for the eutectoid temperature and solubility limit were obtained.
The terminal solid solubility of hydrogen in titanium was measured by differential scanning calorimetry in the concentration range of 0.3–4.1 at.% which practically corresponds to the whole solubility range of hydrogen in α-Ti. The solvus enthalpy obtained in this range from the overall data set was 22.8 ± 0.5 kJ/molH. However, a more careful analysis of the experimental results shows that the solubility curve has two different behaviors as a function of concentration. In the high concentration range 1.4–4.1 at.% a solvus enthalpy of 29.0 ± 1.5 kJ/molH was obtained representing the α/α + δ equilibrium boundary. In the low concentration range, 0.3 at.% to 1.4 at.%, the slope was noticeably lower with 24.2 ± 1.5 kJ/molH for the solvus enthalpy. This last value should correspond to the [α]/[α + γ] equilibrium curve. Although it is possible this value might be influenced by the presence of tiny amounts of the now metastable δ phase–as its presence is revealed by X-ray diffraction analysis – anyway it is consistent with a α + δ ↔ γ peritectoid reaction temperature of 168 °C obtained from the literature.The eutectoid α + δ ↔ β decomposition temperature was determined using samples of high hydrogen contents, ranging from 9 to 11.0 at.%. This temperature was determined to be 319.9 ± 1 °C from the analysis of the DSC diagrams. The solubility limit [α]/[α + δ] at this eutectoid reaction was estimated to be 5.44 ± 0.27 at.%.The present results are believe to provide a closer approximation to the solubility values of H in α-Ti as presently reported in the literature.
