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

M. QUIROGA; C. MACCHI; A. SOMOZA

Orlando

Congreso; 18th International Conference on Positron Annihilation; 2018

Department of Physics and Astronomy, Bowling Green State University

Thefirst aging stage of the supersaturated solid solutions (SSSS) decomposition kinetic,commonly named solute clustering is crucial for establishing the finalmicrostructure of age-hardenable alloy. The comprehension of the atomisticmechanisms involved in the solute clustering in age-hardenable alloys is ofutmost importance to understand the kinetic decomposition process. The combineduse of PALS and CDB have proved to be a powerful tool for the study theprecipitation process in age-hardenable alloys and, in particular the soluteclustering [1]. On the other hand, atomistic simulations based on diffusivemodels such as Kinetic Monte Carlo simulations (KMC) has been used to get detailedinformation regarding vacancy trapping and solute diffusion processes and onthe stabilization of small solute clusters in this kind of alloys [2]. In this work, wepresent the first results of a systematic study on the solute clustering in theAl-4wt.%Cu alloy combining PALS and CDB with KMC simulations. The Al-4%Cu alloywas chosen due to this binary system represents the classical and simplest age-hardenablealloy. PALS was used tofollow the decomposition kinetic of the SSSS of the Al-4wt.%Cu. In-situ measurementswere carried out at different temperatures between 293 and 342K and for different ageingtimes up to 25 days. On the other hand, with the aim to obtain the chemicalenvironment surrounding the positron traps i.e. vacancies CDB measurements wereperformed for selected aging stages. The KMC simulations wereimplemented using different cell sizes up to 100x100x100 unit cells andconsidering periodic boundary conditions. In the proposed model, the diffusionprocess was only ascribed to the vacancy migration while the vacancy hoppingrate was obtained using the residence-time algorithm. To simulate the soluteclustering the main parameters used were the pair binding energies, themigration barriers and the jump attempt frequencies reported for the Al-Cusystem in the literature.  The KMC simulations of the SSSS structuralevolution at atomic scale at different temperatures are discussed in terms ofthe 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)