Microstructure evolution in the self-propagating reaction in Al/Ru bilayers by phase-field simulations and experiments

The self-propagating reaction in binary Al/Ru multilayers with two different bilayer thicknesses (89 and 178 nm, respectively) forming single-phase AlRu intermetallic compound is investigated experimentally and by means of phase-field simulations. Experimentally, the time-temperature evolution in free-standing films was recorded with a high-speed pyrometer, and the resulting microstructure was determined from electron backscatter diffraction measurements. The phase-field model is constructed based on the minimization of the grand potentials for which the required thermodynamic data are taken from the Calphad database. The simulation of the reaction and subsequent AlRu grain growth starts from Al-rich and Ru-rich layer fillings. After the formation of the AlRu phase is complete, the grain growth during cooling is simulated based on the experimentally recorded time-temperature curves. Finally, the resulting grain sizes obtained from the simulation are found to be in good agreement with the experimental results. Furthermore, it is shown that the final grain sizes in both simulations and experiments depend on the initial bilayer thicknesses.