The effect of Cu addition on the thermoelectric power and electrical resistivity of Al–Mg–Si balanced alloy: A correlation study

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Structural materials : properties, microstructure and processing, 2007-09, Vol.465 (1), p.274-282
• Main Authors: Gaffar, M.A., Gaber, A., Mostafa, M.S., Abo Zeid, E.F.
• Format: Article
• Language: English
• Subjects: Al–Mg–Si–Cu alloy; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Cross-disciplinary physics: materials science; rheology; Electrical and thermal conduction in amorphous and liquid metals and alloys; Electrical and thermal conduction in crystalline metals and alloys; Electrical resistivity; Electronic conduction in metals and alloys; Electronic transport in condensed matter; Exact sciences and technology; Materials science; Phase diagrams and microstructures developed by solidification and solid-solid phase transformations; Physics; Precipitation; Q phase; Thermoelectric power; β phase
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/j.msea.2007.02.023

The thermoelectric power (TEP) and the electrical resistivity (ER) of Al–Mg–Si (balanced) and Al–Mg–Si–Cu (balanced + Cu) alloys have been measured in the temperature range 300–800 K. TEP and ER are found affected by different types of precipitates in the Al matrix. Addition of Cu refined the microstructure of the balanced alloy hence altered the TEP and ER measurements. Cu promotes the kinetics of artificial aging due to the formation of the Q′ phase and the intermediate phases which precipitate at earlier temperatures. The coexistence of the equilibrium β (Mg 2Si) and the stable Q-phases results in stabilization of the TEP at elevated temperatures. The existence of Cu slightly increases the lattice rigidity leading to a decrease in the rate by which the ER increases with temperature. Repeating measurements after slow cooling of the two alloys changed considerably the results of TEP and ER. Correlation was found between different types of precipitates and changes in the TEP and ER indicating the possibility of employing TEP and ER measurements to study the precipitation sequence in such alloys.