DESIGN, ASSEMBLY AND CHARACTERIZATION OF COMPOSITE ...

2.5.3.4 Final Stage
During this stage, the removal of these closed pores takes place. The string of
pores at the grain boundary will migrate to the point of lowest energy: the intersection of
four grains in three dimensions, as shown in Figure 2.21. And the pore at the intersection
then shrinks continuously to zero size in a stable fashion. However, this trend may be
hindered by abnormal grain growth that consumes neighboring grains and trap the pores
inside, as illustrated in Figure 2.22. The final density is then limited to less than the
theoretical density.
Figure 2.21 Migration of spherical pores from grain boundary to the four grain
intersections. 37
Figure 2.22 Pore detachment from grain boundary. 37
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