Grain-boundary migration

Fig. 8 reveals that under the assumption of reasonable values for the adjustable parameters in Eq. (7) the theoretical predictions compare well to the experimental data. The very different behaviour of special and non-special boundaries reflects an influence of grain boundary structure on grain boundary migration mechanism. In particular, impurities not only may have an effect on migration by impurity drag, but also by changing grain boundary structure itself. This was shown recently by Udler and Seidman in a Monte Carlo... 

The effect of solute atoms on grain boundary migration cannot adequately be described by standard impurity drag theories. A more satisfactory agreement is obtained by taking an interaction ofthe impurities in the boundary into account. 

Solute atoms do not always reduce grain boundary mobility. Small amounts of Ga in AI will enhance grain boundary migration. 

D. A. Molodov, J. Swiderski, G. Gottstein, W. Lojkowski and L. S. Shvindlerman, Effect of pressure on grain boundary migration in aluminium bicrystals, Acta metall. mater. 42 3397 (1994). 

H. Gleiter. The mechanism of grain boundary migration. Acta Metall., 17(5) 565—573, 1969. 

G. Gottstein and L.S. Shvindlerman. Grain Boundary Migration in Metals Thermodynamics, Kinetics, Applications. CRC Press, London, 1999. 

D.A. Smith, C.M.F. Rae, and C.R.M. Grovenor. Grain boundary migration. In R.W. Balluffi, editor, Grain Boundary Structure and Kinetics, pages 337-571, Metals Park, OH, 1980. American Society for Metals. 

H. Ichinose and Y. Ishida. In situ observation of grain boundary migration of silicon E3 boundary and its structural transformation at 1000 K. J. Phys. Colloq. (Paris), 51(suppl. no. 1) C1 185—190, 1990. 

T. Kizuka, M. Iijima, and N. Tanaka. Grain boundary migration at atomic scale in MgO. Mater. Sci. Forum, 233-234 405-412, 1997. 

R.J. Jahn and P.D. Bristowe. A molecular dynamic study of grain boundary migration without the participation of secondary grain boundary dislocations. Scripta Metall., 24(7) 1313—1318, 1990. 

Thus far, the discussion has been conhned to the static properties of grain boundaries. However, grain boundaries are metastable conhgurations and, as such, in response to external forces (e.g. thermal, mechanical), they exhibit dynamical behavior. Two of the more important ones are briefly mentioned here - grain-boundary migration and sliding. 

For various mechanisms of grain boundary migration, the mobility wQl have various definitions, as given in Table 16.8. The driving force for grain-boundary migration is assumed to be due to the difference in grain curvature ... 

TABLE 16 Effect of Additives on Grain Boundary Migration ... 

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