MSE_442_Lecture_23_Nov 18 2013

The boundary mobility mb depends on the diusion

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Unformatted text preview: s taken as the pressure difference across the boundary Therefore IntegraGon where G0 is the iniGal grain size (G = G0 at t = 0) and K is a temperature dependent growth factor given by 7 Normal Grain Growth in Dense Solids The equaGon (Burke and Turnbull Model) is the parabolic grain growth law that has the same form as the LSW equaGon for interface reacGon- controlled Ostwald ripening The growth factor K has an Arrhenius dependence on temperature T , given by K = K0exp(- Q /RT) , where K0 is a constant, R is the gas constant, and Q is the acGvaGon energy for grain growth. The boundary mobility Mb depends on the diffusion coefficient Da for the atomic jumps across the boundary of the pure material and is termed the intrinsic boundary mobility. For an ionic solid, in which both caGons and anions must diffuse, Da represents the diffusion coefficient of the rate- limiGng (or slowest) species. 8 Exercise 9 Answer 10 Abnormal Grain Growt...
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