A Collector Plate Mechanism-Based Classical Intergranular Precipitation Model for Al Alloys Sensitized at Different Temperatures

作者：Yi Gaosong; Derrick Alexander T; Zhu Yakun; Free Michael L

来源：Metallurgical and Materials Transactions A-Physical Metallurgy and Materials Science, 2015, 46A(11): 5393-5406.

DOI：10.1007/s11661-015-3110-2

The sensitization behavior of Al 5xxx alloys is mainly caused by the formation of Mg-rich precipitates at grain boundaries. In this study, a classical nucleation-growth-coarsening theory for the description of intergranular precipitation is formulated, which adopts a collector plate mechanism, an equivalent average Mg concentration at the grain boundary, and new coarsening mechanisms. Three coarsening mechanisms, the modified Lifshitz-Slyozov-Wagner, the Kirchner mechanism, and a combination of these two mechanisms, are compared. Modeling results reveal that the Kirchner mechanism will breakdown when continuity () is close to 1. According to the new model, the coarsening still accounts for a small fraction (only 10 pct) in the final growth rate after aging at 343 K (70 A degrees C) for 40 months, which is confirmed by the precipitate size distribution data. Thickness and continuity results predicted by the new model agree well with the experimental results obtained from scanning transmission electron microscopy images of Al 5083 H131 alloys aged at 343 K (70 A degrees C) for different times. In addition, the new model is also applied to a high-temperature [453 K (180 A degrees C)] situation, where coarsening of precipitates is observed.

• 出版日期2015-11