On the solute clustering kinetic in the Al-4wt.%Cu alloy: A systematic study using PALS and CDB experimental techniques and Kinetic Monte Carlo simulations

C. MACCHI; A. SOMOZA; M. QUIROGA

Orlando

Congreso; 18th International Conference on Positron Annihilation; 2018

International Conference on Positron Annihilation

The first aging stage of the supersaturated solid solutions (SSSS) decomposition kinetic, commonly named solute clustering is crucial for establishing the final microstructure of age-hardenable alloy. The comprehension of the atomistic mechanisms involved in the solute clustering in age-hardenable alloys is of utmost importance to understand the kinetic decomposition process. The combined use of PALS and CDB have proved to be a powerful tool for the study the precipitation process in age-hardenable alloys and, in particular the solute clustering [1]. On the other hand, atomistic simulations based on diffusive models such as Kinetic Monte Carlo simulations (KMC) has been used to get detailed information regarding vacancy trapping and solute diffusion processes and on the stabilization of small solute clusters in this kind of alloys [2]. In this work, we present the first results of a systematic study on the solute clustering in the Al-4wt.%Cu alloy combining PALS and CDB with KMC simulations. The Al-4%Cu alloy was chosen due to this binary system represents the classical and simplest age-hardenable alloy. PALS was used to follow the decomposition kinetic of the SSSS of the Al-4wt.%Cu. In-situ measurements were carried out at different temperatures between 293 and 342K and for different ageing times up to 25 days. On the other hand, with the aim to obtain the chemical environment surrounding the positron traps i.e. vacancies CDB measurements were performed for selected aging stages. The KMC simulations were implemented using different cell sizes up to 100x100x100 unit cells and considering periodic boundary conditions. In the proposed model, the diffusion process was only ascribed to the vacancy migration while the vacancy hopping rate was obtained using the residence-time algorithm. To simulate the solute clustering the main parameters used were the pair binding energies, the migration barriers and the jump attempt frequencies reported for the Al-Cu system in the literature.  The KMC simulations of the SSSS structural evolution at atomic scale at different temperatures are discussed in terms of the solute clustering revealed by means of the positron techniques used.[1] A. Dupasquier, G. Kögel, A. Somoza. Acta Mater. 52 4707 (2004). Overview N°140[2] G. Sha, A. Cerezo: Acta Mater. 53 907 (2005)