Interstitial Order-Disorder Transformation in the Ti-O Solid Solution. IV. A Neutron Diffraction Study

Interstitial order-disorder transformation regarding oxygen atoms dissolved in alpha-titanium has been studied by neutron diffraction on single crystals in the range from 17 to 28 at% O. Occupation probabilities of the oxygen atoms in the octahedral interstitial sites are determined quantitatively with the variation of composition and temperature. The change of the long-range order with increasing temperature reveals a two-step process attributed to the disordering of the oxygen atoms. The static displacement of the titanium atoms parallel to the c -axis increases almost linearly with the oxygen concentration. The results are compared with the previous works in Parts I, II and III.