Page 260 - Book Hosokawa Nanoparticle Technology Handbook

4.5 STRUCTURE CONTROL OF NANOPARTICLE COLLECTIVES BY SINTERING AND BONDING FUNDAMENTALS
IF steel, whose grain size is 0.65 m, was produced by
accumulative roll bonding (ARB). If the crystal grain
of the base material is too small for a pure material,
such as IF steel, grains become relatively larger in the
stir zone, and the hardness of the stir zone approaches
that of the annealed material. For such a material, the
grain growth of the stir zone can be prevented during
FSW [11] by a heat treatment before FSW, to some
extent, that makes the grains grow as shown in
Fig. 4.5.23(c). In this case, the heat treatment condi-
tions are 30 min. at 600 C. The grain sizes in the stir
zone after FSW are not always in the same order of the
grain sizes before FSW. The minimum grain size can-
not be obtained after FSW when the grain size is too
large or too small before the FSW. Thus, there is an
optimal initial grain size for obtaining the final high-
est strength, indicating the requirement of a material
Figure 4.5.24 design especially for FSW. The same result has also
Carbon nanotube distributed AZ31 by FSP. been obtained for an aluminum alloy.

Figure 4.5.25
Thermal stability of SiC distributed AZ31by FSP.

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