The second observation is that the refining of Al3Ti particles was only
affected by mechanical fracture. Most of initial Al3Ti clusters in the SZ
were pulverized by 1-pass FSP (Fig. 5a). Meanwhile, the rotating pin
also knocked off the corners and sharp edges from the Al3Ti and thus
blunted the sharp Al3Ti: an example of this is shown in Fig. 6b. Increasing
the number of FSP passes, more plastic deformation and thorough
mixing would persistently decrease the size of Al3Ti particles and improve
particle homogeneity (Fig. 5c and e)