Solubility of hydrogen in α-iron and its alloys with Ti, Mn, V, and Ni at atmospheric hydrogen pressure and two temperature of 800 and 700℃ was determined with thermal charging and vacuum extraction analysis.
These solubilities show minimum points at low concentration of alloying elements and it is suggested that this phenomenon may be interpreted by the nature of the density of state at Fermi surface of matrix metal.
With these solubility data, interation parameter and interaction energy between each alloying elements and hydrogen are calculated applying the concept of Quasi-chemical model. These values are all negative and are more negative in the order of Ti, V, Mn, and Ni.
The nature of these interation energies is discussed in terms of the two major parts, i.e. the electronic structure of alloying element and strain induced by the difference between atomic radius of iron and that of alloying element. And the result is that the former contributes dominantly to the solubility of hydrogen in the alloys investigated and the effect of the latter may be ignored at the condition studied in this study.
Calculated interation energies between alloying elements and hydrogen in iron are linearly proportional to the electronegativity function F defined by McLellan. Following is the empirical relation between interaction energies (Δε) and F.
Δε = -4.5-7.7F at 800℃
Δε = -3.3-6.7 F at 700℃
Using this equation, the effect of some elements unmeasured can be predicted.