Mobility of Domain Walls in Proper Ferroelastic Martensites

Abstract
Based on the Landau-Ginzberg free energy functional for an O_h-D_4h proper ferroelastic martensitic transformation the mobility of a (110) twin boundary in a large bicrystal has been calculated by including dissipation in the approximation of the phonon viscosity model and by solving the inverse boundary value problem for the limiting case of strong shear modulus softening. Application to actual materials requires determination of the phonon viscosity tensor from experimental ultrasonic attenuation or low frequency internal friction data after subtraction of "extrinsic" losses, especially those from pretransformation structural strain modulations ("tweed'') and dislocations. Numerical application to V₃Si, the only proper ferroelastic martensite for which such experimental data pertaining to the soft [110]/[1-10] shear mode are available, is discussed.