Local crystallization induced in Fe-based amorphous alloys by swift heavy projectiles

We report the effect of the high density of electronic excitation deposited along the path of swift heavy ions in various amorphous alloys. The samples were irradiated at low temperature with GeV Pb ions up to fluences of 1 × 10¹¹ to 2.3 × 10¹³ cm^-2. The formation of nanocrystalline phases was observed by transmission electron microscopy in the FIN-EMET-like Fe_73.5Nb_4.5Cr₅Cu ₁B₁₆ alloy and in the NANOPERM ternary Fe ₉₀Zr₇B₃ glassy systems but not in the Fe _80.5Nb₇Bi_2.5 alloy. The crystallization phenomenon was interpreted in terms of the relaxation of the high level of energy deposited in electronic excitations along the path of Pb ions in the target, which induce radial pressure waves in the vicinity of the projectile trajectories. These mechanical stresses destabilize the amorphous structure and induce nanocrystallization.