Characterization by thermoelectric power of a commercial aluminum-iron-silicon alloy (8011) during isothermal precipitation

Abstract

We have characterized a commercial 8011 (Al-Fe-Si) alloy by studying samples under different initial states of strain hardening and iron and silicon supersaturation using thermoelectric power as a measurement technique. Isothermal kinetics of precipitation are obtained in the temperature range between 225 ЊC and 600 ЊC. We determine the atom fraction precipitated for each microstructural condition, identifying the dominant alloying additions and evaluating the typical parameters of the precipitated phases, such as, for example, the apparent activation energy. Finally, we determine the time-temperature-transformation (TTT) diagrams. Our results prove that iron is the alloying addition that controls the precipitation kinetics of the 8011 alloy in the temperature range studied.

Experimental Study of the Interaction between Recrystallization and Precipitation Processes of an AA8011 Commercial Alloy

“…Figure 3(a) shows that for temperatures below the appearance of the first peak, the behavior observed is similar to the one shown previously, even though the position of said peak seems to be slightly changed due to the isochronous treatment of the samples. Like in the previous case for HS and DHS samples, the peak is associated with the precipitation of the -AlFeSi phase; however, the release of energy stored must occur simultaneously in the DHS samples, although not enough for a complete recrystallization to occur, the reason being that the measurements of thermoelectric power still keep showing a single peak associated with both processes, the precipitation of Fe masking the particular effect that the dislocations may have on that property [9,13]. However, at higher temperatures, the dissolution of the phase, as well as the precipitation of the Al 3 Fe phase, seems to present a more uniform behavior in agreement with our previous explanation.…”

“…The main peaks are placed at a temperature near 335 ∘ C for low preaging times, corresponding to the precipitationrecrystallization reaction, and at 322 ∘ C for high preaging times, where undoubtedly a great amount of recrystallization and precipitation has occurred (mainly for 500 min at 300 ∘ C with 90% of the precipitation-according to Luiggi [9]). The second peak, regardless of preaging and associated with the precipitation of the stable Al 3 Fe phase, occurs at 485 ∘ C. The transition between both reactions shows a difference in Δ of −0.1 V/K only explained by a significant introduction of Si atoms in the solution and a few Fe atoms, which regroup when temperature increases in order to generate said stable phase.…”

“…The commercial alloy AA8011 was chosen for this purpose, where Fe and Si, as main alloying elements, regulate the microstructure and properties of the Al-Fe-Si system. Several works dealing with this alloy have been reported in the literature [7][8][9][10][11]. Garcia-Cordovilla and Louis [12] differentiated exothermal reactions associated with precipitation and recrystallization of this alloy via DSC measurements.…”

Influence of Second Phase Particles on Recrystallisation of Cold-Rolled Low Carbon Microalloyed Steels during Isothermal Annealing

“…A schematic representation of the TEP apparatus is given elsewhere [2]. The experimental procedure of the TEP measurement is the following: the sample is pressed between two blocks of a reference metal (in this case, pure iron).…”

Evaluation of the Austenitic Grain Growth by Thermoelectric Power Measurements

“…The micrographs were then analysed with the Image Tool 2.0 software. A schematic representation of the TEP apparatus is given elsewhere [1]. The experimental procedure of the TEP measurement is the following: the sample is pressed between two blocks of a reference metal (in this case, pure copper).…”