Contents lists available at ScienceDirect Computational Materials Science journal homepage: www.elsevier.com/locate/commatsci Solidification and heat treatment simulation for aluminum alloys with scandium addition through CALPHAD approach Rajesh Jha a,b, ⁎ , George S. Dulikravich a a MAIDROC Laboratory, Mechanical and Materials Engineering Department, Florida International University, Miami, FL 33174, USA b Department of Mechanical Engineering, Colorado School of Mines, Golden, CO 80401, USA ARTICLE INFO Keywords: Aluminum alloys CALPHAD Deep Learning Artificial Neural Network (DLANN) Scheil-Gulliver’s solidification simulation Heat treatment Interfacial energy 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 Al 3 Sc 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 Al 3 Sc 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 con- sidered 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 Al 3 Sc crystals during heat treatment, it is important that Al 3 Sc 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. 1. Introduction In structural materials, aluminum alloys are preferred over other alloys due to superior strength to weight ratio. Strength in these alloys is achieved by ageing or precipitation hardening [1,2]. Precipitation hardening phases depend on the major alloying element and its com- position [1,3]. Aluminum alloys have been divided into several classes based on the major alloying element in addition to aluminum [4]. One of the problems with aluminum alloys is their poor corrosion resistance [1]. In recent years, a significant amount of research has been reported on the use of scandium in aluminum alloys [1] with the objective of improving the anti-corrosion potential of aluminum alloys even when scandium is added in small amounts [1]. Regarding pre- cipitation hardening, research shows that scandium is one of the best alloying elements that enhances strengthening mechanism by pre- cipitation hardening in aluminum alloys, where some reports also suggest that only gold is better than scandium in enhancing strength- ening of these alloys [1]. One of the factors that limit precipitation of Al 3 Sc phase is the temperature regime of precipitation of Al 3 Sc during heat treatment [1–3,5,6]. Al 3 Sc precipitates at about 300 °C, while other phases that strengthen aluminum alloys precipitate around 160–200 °C [1–3,5,6]. In non-heat-treatable alloys, strengthening by Al 3 Sc plays an important role [1]. In heat-treatable alloys, it is im- portant that some amount of Al 3 Sc is present in the melt to enhance the precipitation of Al 3 Sc phase in the desired grain size range as a limited amount of Sc can be precipitated from supersaturated solution [1,2]. First phase diagrams of the Al-Sc system appeared in the USSR in 1964 [1]. In these diagrams, four phases were shown, Al 3 Sc, Al 2 Sc, AlSc and AlSc 2 , where Al 3 Sc is an equilibrium phase, or is the phase which is in thermodynamic equilibrium with Al [1]. Since the 1980’s, aluminum alloys containing Sc have been systematically developed and some parts of military aircraft have been manufactured from Al-Li alloys https://doi.org/10.1016/j.commatsci.2020.109749 Received 25 December 2019; Received in revised form 8 April 2020; Accepted 14 April 2020 ⁎ Corresponding author at: Postdoctoral Researcher, MAIDROC Laboratory, Mechanical and Materials Engineering Department, Florida International University, Miami, Florida 33174, USA. E-mail addresses: rjha001@fiu.edu, rjha@fiu.edu (R. Jha). Computational Materials Science 182 (2020) 109749 0927-0256/ © 2020 Elsevier B.V. All rights reserved. T