Low-energy electron-driven observation of nanometer-sized Laves phases at alloy surfaces enabling statistical characterization with high precision and efficiency

Alloys strengthened by nanometer-sized Laves phases have been used as structural components working in corrosive environments at high temperatures owing to the favorable physical and chemical properties of Laves phases. However, due to the small sizes of Laves phases in alloys, their precise characterization cannot be realized efficiently by the existing methods. We previously found that under irradiation of a polished Zircaloy-4 alloy [Zr–1.50Sn–0.25Fe–0.15Cr (wt.%)] with a focused, low-energy (30 keV) electron beam, surface Zr atoms in the α-phase matrix, instead of the ones in nanometer-sized Zr(Fe, Cr)2 Laves phases, were able to undergo significant sputtering into vacuum in a field-emission scanning electron microscope (FE-SEM), resulting in the exposure of the Laves-phase nanoparticles (NPs). Based on this surprising physical phenomenon, here we successfully develop a methodology for performing statistical characterization of Laves-phase NPs in fully recrystallized Zircaloy-4 alloys as well as their partially recrystallized counterparts. By comparing the attributes of the Laves-phase NPs in both partially and fully recrystallized alloys, the conventional, tiny Ostwald ripening of the Laves phases was, for the first time, found to occur during the alloy recrystallization process. These understandings are likely to elucidate the universal mechanisms underlying the nucleation and growth of Laves-phase NPs in solid solutions.