| The effect of grain boundaries (GB) on phase stability and transformation kinetics has been investigated in framework of simple model which takes into account a competition between ordering and chemical decomposition processes. It was shown that a deviation of alloy parameters near GB from bulk values can essentially change the equilibrium of an alloy and precipitation kinetic. In particular, GB segregation can stimulate the surface directed decomposition of the ordered phase; the decrease of the ordering energy near GB results in formation of the concentration inhomogeneity which coexists together with ordering in the bulk. The effect of GB appears significant for small grain size, when the GB segregation is able to change the alloy composition inside the grains. These results allow understanding the mechanism of the phase instability of alloys subjected to severe plastic deformation. |
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