Revision of the Ti-N phase diagram as probed by neutron diffraction
Аннотация
Full-profile (Rietveld) analysis of neutron diffraction patterns was used to show that the homogeneity ranges of a tetragonal phase ɛ-Ti2N1 − x and an ordered tetragonal phase δ′-Ti2N2x phase of the Ti-N system lie within 0.38 ≤ N/Ti ≤ 0.42 and 0.45 ≤ N/Ti ≤ 0.50, respectively. Unit cell parameters were determined for ɛ and δ′ phases at the lower and upper boundaries of the homogeneity ranges. A cubic nitride phase having a short-range order in the nitrogen arrangement was shown to exist in the concentration range 0.45 ≤ N/Ti ≤ 0.75 at relatively high temperatures. The short range order transforms to a long-range order below 800 K in the concentration range 0.45 ≤ N/Ti ≤ 0.50. Phase transition features in titanium nitride were determined for the concentration range TiN0.45–TiN0.50. A revised version of a fragment of the Ti-N phase diagram was proposed proceeding from the formation conditions and the existence ranges of the δ′ and ɛ phases and on the basis of literature data.