Theoretical progress in non-equilibrium grain-boundary segregation(II):Micro-mechanism of grain boundary anelastic relaxation and its analytical formula

Finding the internal-friction peak of grain boundary anelastic relaxation was one of the important breakthroughs in the study of internal friction in the last century. But the micro-mechanism of grain boundary anelastic relaxations is still obscure. Based on the observations of the grain boundary segregation or depletion of solute induced by an applied stress, the following micro-mechanism was suggested: grain-boundaries will work as sources to emit vacancies when a compressive stress is exerted on them and as sinks to absorb vacancies when a tensile stress is exerted, inducing grain-boundary depletion or segregation of solute, respectively. The equations of vacancy and solute concentrations at grain boundaries were established under the equilibrium of grain-boundary anelastic relaxation. With these the kinetic equations were established for grain boundary segregation and depletion during the grain boundary relaxation progress. Supported by the National Natural Science Foundation of China (Grant No. 50771036)