Kinetics of Pore-Boundary Interactions

With the definition of the pore mobility, it is possible to analyze the influence of the interactions between the pores and the grain boundaries on the kinetics of grain growth. There are two cases that can be considered (i) the pore becomes separated from the boundary and (ii) the pore remains attached to the boundary. 

When Vp Vb, pore separation will be observed, and this condition can also be written as follows  

The effective driving force on the boundary is F = Fb - NaFp, and from Eq. (8.78), there is F= Vp/Mb. From Vp = Vb = F M INa, there is F=EbMp/T/A b Fb. The driving force on the boundary is almost balanced by the drag of the pores, while the boundary migration is limited by the pore mobility. This condition is referred to as pore control. The other limiting condition is NaM Mp, in which case  

The drag exerted by the pores is NaFp = NA.(FiMh/Mp) Fb- The presence of the pores has almost no effect on the boundary velocity, which is a condition known as boundary control. 

---