Microscopic phase-field study on L12 interface properties of Ni75Al18Cr7 superalloy

In this study, the solidification and precipitation process of Ni75Al18Cr7 superalloy was investigated based on the microscopic phase-field method. The simulation results were validated by using the experimental results. There were three types of ordered interfaces between L1(2) phase, namely (200)(L)//(200)(L).1/2[001](L),(200)(L)//( 200)(L) and (100)(L)//(200)(L).1/2[001](L), which were studied by plotting the microstructural characteristics of Ni75Al18Cr7 superalloy and the distribution of atomic occupation probability and evolution of atomic occupation probability on both sides of the interface between L1(2) phases. The simulation results show that the former two interfaces could migrate with the precipitation evolution process, while the latter ordered interface (100)(L)//(200)(L).1/2[001](L) could not migrate. The interface migration was caused by the migration and exchange of Ni/A1 atoms at the ordered interface. The atomic concentration in the ordered interface before and after migration was almost constant, i.e., the segregation and dilution of each atom was almost constant. The experimental results show that the L1(2) phase structure grew gradually with the increase in heat treatment time, which is consistent with the simulation results of microscopic phase-field method. Moreover, the volume fraction of L1(2) phase calculated by the phase-field method was almost the same as that obtained by X-ray diffraction (XRD) experiments, which indicates the feasibility of using microscopic phase-field method to guide the optimization design of alloy. (C) 2021 Elsevier B.V. All rights reserved.