  Modulating energy states of metallic glasses (MGs) is significant in
understanding the nature of glasses and control their properties. In this
study, we show that rejuvenation in enthalpy can be achieved and preserved in
bulk MGs by using high pressure (HP) annealing, which is a controllable method
to continuously alter the energy states of MGs. Contrary to the decrease in
enthalpy by conventional annealing at ambient pressure, such rejuvenation can
occur and be enhanced by increasing both of annealing temperature and pressure.
By using double aberration corrected scanning transmission electron microscopy,
it is revealed that the rejuvenation, which is attributed to coupling effect of
high pressure and high temperature, originates from the microstructural change
that involves "negative flow units" with a higher atomic packing density
compared to that of the elastic matrix of MGs. The results demonstrate that HP
annealing is an effective way to rejuvenate MGs into higher energy states, and
it may assist in understanding the microstructural origin of the rejuvenation
in MGs.

Materials Science