The solubility of nitrogen in austenitic stainless steel was investigated thermogravimetrically by equilibrating thin foils of AISI 304 and AISI 316 in ammonia/hydrogen gas mixtures. Controlled dissolution of colossal amounts of nitrogen under metastable equilibrium conditions was realized, with nitrogen contents as high as corresponding to an occupancy of yN = 0.61 of the interstitial sublattice, i.e. about 38 at.% N. Associated with the dissolution of these unprecedented nitrogen contents in an austenitic matrix a reversible volume expansion of the austenite lattice occurred for yN > 0.17. A simplistic model based on a statistical distribution of the nitride forming elements over the octahedrons constituting the solid state agrees favorably with the experimental data.
|Journal||Metallurgical and Materials Transactions A|
|Publication status||Published - 2006|