Precipitation kinetics of Al-1.12 Mg2Si-0.35 Si and Al-1.07 Mg2Si-0.33 Cu alloys

• Published in: Journal of alloys and compounds 2007-02, Vol.429 (1-2), p.167-175
• Main Authors: GABER, A, GAFFAR, M. A, MOSTAFA, M. S, ABO ZEID, E. F
• Format: Article
• Language: English
• Subjects: Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Materials science; Phase diagrams and microstructures developed by solidification and solid-solid phase transformations; Physics; Precipitation; Solid solution, precipitation, and dispersion hardening; aging; Treatment of materials and its effects on microstructure and properties
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2006.04.021

The kinetics of hardening precipitates of Al-1.12wt.% Mg2Si-0.35wt.% Si (excess Si) and Al-1.07wt.% Mg2Si-0.33wt.% Cu (balanced+Cu) alloys have been investigated by means of differential scanning calorimetry and hardness measurements. The excess Si enhances the precipitation kinetics and improves the strength of the material. On the other hand, however addition of Cu assist formation of the Q' phase which positively changed the alloy strength. The high binding energy between vacancies and solute atoms (Si and Mg) enhances the combination of Si, Mg and vacancies to form Si-Mg-vacancy clusters. These clusters act as nucleation sites for GP-zones. The coexistence of the beta'- and Q'-precipitates in the balanced+Cu alloy results in a higher peak age hardening compared to the alloy with Si in excess.