Temperature-dependent nucleation kinetics of Guinier-Preston zones in Al–Cu alloys: An atomistic kinetic Monte Carlo and classical nucleation theory approach

Competing nucleation of single- and double-layer Guinier–Preston zones in Al–Cu alloys

“…If equilibrium conditions are assumed in the nucleation process of n -atom solute clusters at the atomic level, the rate of cluster growth should be balanced by the rate of the reverse process, as follows 27 : where C ( n ) is the number density of n -atom clusters given by where is the number density of single solute atoms. Furthermore, is defined as: where and A ( n ) are the activation free energy and attempt frequency, respectively, for the attachment of a solute atom to the n -atom cluster; is approximated by 28 , 29 : where is the free energy of activation for vacancy-assisted migration of a solute atom in the matrix. Then, by assuming for sufficiently large n , the logarithm of the ratio between detachment and attachment rates is described as: …”

“…On the other hand, direct DFT calculations for supercells containing a nucleus of GP1 and GP2 clusters, whose sizes typically reach and even exceed several nanometers, are highly challenging and even infeasible owing to the huge computational costs. In this study, to obtain of the GP1 and GP2 zones in Al–Cu alloys, we used an on-lattice effective multi-body potential that considers the interaction between the clusters, which is extension of our previous work 29 .…”

“…As described in the previous sections, clusters with a size above that of the critical nucleus tend to grow spontaneously, whereas those below this size tend to shrink. To examine the CNT results of the temperature dependence of critical nucleus sizes from a kinetic point of view, we used atomistic kinetic Monte Carlo (kMC) calculations 29 , which can describe the effect of configurational entropy without using the approximation based on the ideal solution model given in Eq. ( 3 ).…”

“…We systematically conducted atomistic kMC calculations of growth (or shrinkage) of GP1 and GP2 clusters at temperatures of 370 and 450 K using the same potential applied to the CNT model. It should be noted that vacancy-solute interactions and the activation barriers for vacancy migration were considered following our previous study 29 .…”

Effect of Ultrafine Grains on the Coating Reaction and Anticorrosion Performance of Anodized Pure Aluminum

“…Alloying, such as adding silicon (Si), copper (Cu), magnesium (Mg), zinc (Zn), manganese (Mn), and other elements, is the most important and effective method for improving the strength of Al. Solid-solution strengthening, second-phase strengthening, and precipitation strengthening are the primary mechanisms to strengthen Al alloys [5][6][7][8]. However, with the exception of adding Mg and Mn, alloying always leads to a significant decrease in the corrosion resistance of Al because of the appearance of cathodic secondary phases, which create microcorrosion cells with the Al matrix [9,10].…”