Plastic deformation, anharmonicity and Grüneisen parameter of α-titanium

Grüneisen's parameter γ of polycrystalline α-titanium is experimentally found to be very sensitive to the amount of plastic deformation previously suffered by the sample. The observed behaviour may be explained in terms of sessile dislocation density within crystallites, leading to short-wavelength phonon-phonon coupling. Experimental values of γ, obtained by a new thermodynamic method, are fitted to a simple model based on dislocation attrition and multiplication and which is a modified version of a model due to Gilman (1965).