I. A Vacuum X-Ray Diffractometer for High Temperature Studies. II. An Investigation of the Allotropic Transformation of Titanium

[摘要] A vacuum high temperature x-ray diffractometer has been designed and constructed to study metals, sensitive to oxygen and nitrogen contamination, up to 1200°C. The factors which affect the accuracy of the diffractometer method and the proper choice of extrapolation functions are discussed. It is shown that this instrument can determine lattice parameters with an accuracy of one part in forty thousand. The thermal expansion of titanium has been investigated to 650°C and the c/a parameter is found to increase rapidly above 400°C. This variation of c/a is correlated with other properties of titanium to formulate a band model. On the basis of this model it is shown that the electrons can give an appreciable positive contribution to the free energy as the transformation temperature is approached and it is proposed that this is the main factor causing the instability of the low temperature modification of titanium.

[发布机构] University:California Institute of Technology;Department:Engineering and Applied Science

[关键词] Engineering Science and Physics