  The process of crystal nucleation can be accelerated or retarded by
ultrasonic vibration, which is particularly attractive for the addictive
manufacture and thermoplastic forming of metallic glasses, however, the effect
and mechanism of oscillatory loading on the nucleation process are still
elusive. By using molecular dynamics simulation, the changes in the
time-temperature-transformation (TTT) curve under oscillatory external loading
are systematically investigated in two typical binary alloys. A glass forming
ability dependent response to the external loading is found, and the shortest
incubation time is insensitive to the external loading, while the corresponding
temperature can be significantly shifted. Within the framework of classical
nucleation theory, a fitting formula is proposed to describe the simulation
data quantitatively. In contrast to stationary shear, the elastic stress,
rather than the strain rate, is the key parameter to control the evolution of
TTT curve under oscillatory loading. Furthermore, the model shows that
oscillatory loading can decouple the mobility and nucleation in the deeply
supercooled liquid, hence the formation ability can be enhanced while the
nucleation is suppressed, which is particularly helpful for the forming and
manufacturing of metallic glasses.
