The effect of temperature and deviation from stoichiometry on the mechanical properties of titanium monoxide

Abstract

The mechanical properties of TiO have been investigated with particular reference to the effects of temperature and composition on the yield and flow stresses in the temperature region 980–1250°C.The results obtained indicate that macroscopic plastic deformation only occurs at temperatures above 1000°C. In the temperature range 1000–1250°C deformation occurs by slip on a {111} 〈110〉 system, in a manner similar to f.c.c. metals. The activation energy for dislocation motion, is higher, however (1.0 eV). This is attributed to the high frictional resistance of the crystal lattice resulting from the presence of covalent metal-non-metal bonds. This explanation is supported by the observation that the yield strength increases as the oxygen content of the phase is increased. It is probable, however, that a further component of the lattice friction arises from the presence of residual locally ordered domains of the ordered structure stable below 980°C.A brief summary is also given of the problems associated with the growth of single-crystal TiO of various compositions in the extensive phase range.