title: The formation mechanism of eutectic microstructures in NiAl-Cr composites.
abstract: NiAl-based eutectic alloys, consisting of an ordered bcc matrix (B2) and disordered bcc fibers (A2), have been a subject of intensive efforts aimed at tailoring the properties of many of the currently used nickel-based superalloys. A thermodynamic phase field model was developed on a thermodynamic foundation and fully integrated with a thermo-kinetic database of the Ni-Al-Cr ternary system to elucidate the resulting peculiar eutectic microstructure. Invoking a variation of the liquid/solid interfacial thickness with temperature, we simulated the characteristic sunflower-like eutectic microstructures in the NiAl-Cr composites, consistent with experimental observations. The mechanism that governs the formation of the peculiar eutectic morphology was envisioned from the modeled evolutions associated with six sequential steps. Our calculations show that the conditional spinodal decomposition occurring in sequence could further trim and revise the microstructure of the eutectics by generating fine-domain structures, thereby providing an additional method to explore the novel NiAl-based eutectic composites with tunable properties at elevated temperatures.
authors.affiliation: State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi'an 710072, P. R. China and IMDEA Materials Institute, c/Eric Kandel, 2, Getafe 28906, Madrid, Spain.
authors.forename: Bin
authors.initials: B
authors.lastname: Tang
authors.affiliation: Department of Materials Science & Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Cogswell
authors.affiliation: IMDEA Materials Institute, c/Eric Kandel, 2, Getafe 28906, Madrid, Spain.
authors.forename: Guanglong
authors.initials: G
authors.lastname: Xu
authors.affiliation: IMDEA Materials Institute, c/Eric Kandel, 2, Getafe 28906, Madrid, Spain.
authors.forename: Srdjan
authors.initials: S
authors.lastname: Milenkovic
authors.affiliation: IMDEA Materials Institute, c/Eric Kandel, 2, Getafe 28906, Madrid, Spain and Institute for Advanced Metallic Materials & School of Materials Science and Engineering, Nanjing Tech University, Nanjing 210009, China. ycui@njtech.edu.cn.
authors.forename: Yuwen
authors.initials: Y
authors.lastname: Cui