Clustering of Mg in binary alloys was studied by means of atomistic simulation. This phenomenon was analyzed in the undistorted Al lattice, as well as in the presence of dislocations. In the undistorted lattice, the Mg exhibited a tendency to cluster into a coherent phase. The binding energy of this structure was relatively low, and it dissolved at room temperature; only dynamic associations of doublets or triples of solute atoms were observed. Increasing the temperature to above 100C inhibited the formation of any solute short-range order. The application of an homogeneous hydrostatic strain had no effect upon clustering. In the presence of dislocations and at room temperature, the Mg clustered at cores to form the coherent phase observed in the undistorted lattice at low temperatures. Clustering at the cores of all types of dislocation was considered. It was shown that the size, shape and structure of the cluster could not be predicted by using elementary calculations which were based upon the pressure field generated by the unclustered dislocation. Moreover, the field of the clustered dislocation was observed to differ from that of the unclustered defect, even at distances as large as 20 Burgers vectors from the core. The variation in the stacking fault due to clustering was determined simply by monitoring the distance between partials. This was observed to decrease upon clustering.

Solute Clustering in Al–Mg Binary Alloys. D.Zhang, R.C.Picu: Modelling and Simulation in Materials Science and Technology, 2004, 12[1], 121-32