Solidification and heat treatment simulation for aluminum alloys with scandium addition through CALPHAD approach

Abstract

Scandium, and scandium combined with zirconium, improves multiple properties of aluminum based alloys. In this work, we performed solidification and heat treatment simulations for studying precipitation kinetics of Al3Sc crystals within the framework of CALPHAD approach on novel candidate alloy compositions from our previous work belonging to 2XXX, 6XXX and 7XXX class of aluminum alloys. In our previous work, computational study was performed on stability of various stable and metastable phases along with thermodynamically stable Al3Sc phase in heat-treatable aluminum alloys of 2XXX, 6XXX and 7XXX series by application of several concepts of artificial intelligence on phase stability data generated under the framework of CALPHAD approach. We considered 12 elements for 2XXX, 10 elements for 6XXX and 11 elements for 7XXX class of alloys, thus selected a comparatively large multicomponent system when compared to works reported on aluminum alloys through CALPHAD approach. In 2XXX and 7XXX series, both Sc and Zr were included, while in 6XXX series only Sc was added. Software Thermocalc was used to generate phase stability data. For proper precipitation of Al3Sc crystals during heat treatment, it is important that Al3Sc is present in the melt. Hence, solidification simulation (Scheil–Gulliver) was performed, followed by heat treatment simulation at various temperatures for a few candidate alloys belonging to these three series of aluminum alloys with Sc added. Additional strengthening phases were also considered in aluminum base alloys of these three series in our previous work. The presented computational approach can be useful and can be used as a screening tool for selecting a chemical composition and heat treatment protocol prior to performing experiments.