Formation of precipitates in an ordering alloy and their dissolution under irradiation

Abstract

The formation process of precipitates in an ordering alloy and their dissolution under irradiation have been studied by solving coupled kinetic equations for local composition X( r, t) and local degree of order S( r, t) in a two-dimensional continuous medium. Spherical precipitates of an ordered (or disordered) phase are formed in a disordered (or ordered) matrix during isothermal annealing of a quenched homogeneous state. Two-dimensional snap-shots of the processes clearly demonstrate that heterogeneous fluctuations of S induce compositional modulation, leading to nucleation of the precipitates. Irradiation with energetic particles makes the precipitates unstable and dissolves them into the matrix. It is suggested that the life time of precipitates under irradiation would be elongated with increase of volume fraction of the ordered phase. The coupling of local fluctuations in X and S plays an important role also in the dissolution process under irradiation.