  Study of condensed matter in certain extreme conditions allows one to better
understand the mechanisms of microscopic structural transformations and to
develop materials with completely new mechanical properties. In the present
work, we study the structure and crystallization kinetics of bulk metallic
glass (BMG) Ni$_{62}$Nb$_{38}$. We show that this BMG is rapidly crystallized
under the combined effect of shear deformation and ultrahigh pressure. A
threshold pressure required to initiate the formation of a stable crystalline
phase is revealed. Shear deformation and pressure lead to the phase separation:
two high-density inhomogeneous crystal structures are formed. We find that the
crystallization of this BMG occurs in two stages due to the significant
difference in the growth rates of Ni and Nb crystalline phases. The results of
the present study make a significant contribution to understanding the
crystallization and amorphization features of Ni-based BMG's.
