Effects of Local Bonding between Solute Atoms and Vacancy on Formation of Nanoclusters in AlMgSi Alloys+1

Abstract

Nanoclusters formed in AlMgSi alloys affect the aging behavior of the alloys depending on the formation temperature. In the present study, first-principles calculations were carried out to evaluate the two- and three-body interactions between Mg, Si atoms and vacancies in the Al matrix and estimate the effect of local bonding on the formation of nanoclusters. Monte Carlo simulations were subsequently performed to investigate the stable structure of the nanocluster formed in Al0.95 mass pct Mg0.81 mass pct Si alloy. We found that the MgSi and SiVac pairs are stable in the Al matrix. The result shows that the solute atoms easily aggregate with different types of solute atoms and that the Si atom has a strong attractive interaction with a vacancy. Furthermore, MgSivacancy triplets are more stable than MgSi and Sivacancy pairs in the Al matrix. The nanoclusters in the Al matrix were thermally stabilized by the stable configurations between solute atoms and vacancy. Thus, the electronic structure calculations suggested that the local bondings within a nanocluster play a significant role in not only the thermal stability but also the formation and growth behavior of nanoclusters during aging at low temperatures. [doi:10.2320/matertrans.MT-L2023006]