Effects of Alloying Elements on the Activity of Nitrogen in Austenite : II Effect of Nickel and Solubility of Nitrogen in Pure Iron

Abstract

Solubility of nitrogen in austenite was measured in iron-nickel alloys in order to study the effect of nickel on the activity of nitrogen in austenite and to obtain the value of their interaction parameter. The composition of samples covered the whole range of iron-nickel alloys biginning from pure iron to pure metallic nickel, and the experimental temperatures were 1050° and 1250°C. The presence of nickel increased the activity of nitrogen in austenite and the interaction parameters were obtained as : The solubility of nitrogen in pure gamma-iron under the various partial pressures of less than 1 atm of nitrogen was measured at 1150°C and it was shown that Sieverts' law was obeyed on the dissolution of nitrogen in austenite. The free energy of solution of nitrogen in austenite is given as : A close relationship between the interaction parameters and the atomic number of alloying elements was observed and it was also found that the absolute value of the interaction parameters was decreased with the increase in temperature. The differences of the interchange energies between the pair of iron-nitrogen and that of alloying element-nitrogen were calculated from two theoretical equations, but the results of calculation did not show a good agreement.