The Effects of Double-Step Homogenization on Precipitation Behavior of Al3Zr Dispersoids and Microstructural Evolution in 2196 Aluminum Alloy

Abstract

The effects of double-step homogenization processes on the precipitation of Al3Zr dispersoids and the dissolution of the primary phases of 2196 aluminum alloy were studied by optical microscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). It was revealed that first-step homogenization facilitates the nucleation of Al3Zr, while second-step homogenization results in the dissolution of the primary phases and the growth of Al3Zr dispersoids. The nanosized θ’ precipitates formed in the first-step homogenization are dissolved after the second-step homogenization. The optimum homogenization process was selected as 400 °C/10 h + 520 °C/24 h, which effectively dissolves the primary phases and promotes the formation of refined distribution of Al3Zr dispersoids. This phenomenon is mainly caused by the highest nucleation rate of the Al3Zr phase at 400 °C. While reducing the heating rate of the homogenization process can increase the number density of the Al3Zr dispersoids and reduce the precipitate free zone (PFZ), it does not alleviate the inhomogeneity of the Al3Zr precipitation. These results are expected to be meaningful for tailoring the industrial homogenization processing of as-cast Al-Cu-Li alloy.

Coupling Effect of Mn Addition and Deformation on Mechanical and Electrical Properties of Al-Zr Alloys

“…The TEM examinations were performed on a JEOL-2100 microscope (JEOL Ltd., Tokyo, Japan) operating at 200 kV. The TEM foils were prepared following the standard electro-polishing techniques for Al alloys [16,17]. Cross-sectional TEM examinations were carried out to measure average grain size (d) of the hot-deformed alloys using a linear intercept method, for which at least 150 grains were examined to obtain an average value.…”

“…Similarly, at least 200 precipitates were measured to determine the average inter-particle spacing. More details about the measurements of precipitates are provided in previous publications [16,17,20]. Image analysis was performed by geometrical phase analysis (GPA) [21], where the reference area used in the digital processing as a strain-free area was chosen in the matrix as far as possible from the precipitate under study, as a general procedure.…”