Quasi-static cyclic loadings induced inelastic deformation in a Zr-based bulk metallic glass under nanoindentation
Résumé
Cyclic nanoindentation tests were carried out
on Zr50Cu40Al10 bulk metallic glass (BMG). From the
designed quasi-static and incremental cyclic experiments at
loading rates ranging from 250 to 2500 lN/s and at
ambient temperature, we observed significant difference in
inelastic deformation as a function of solicitation modes.
Under incremental cyclic loadings, the hardness of the
BMG increased each time when the sample was reloaded
immediately after unloading and then gradually reduced
before the next unloading. In contrast, we found that quasistatic
cyclic loadings induced a mechanical softening
which appears to be dependent on the number of cycles and
the loading rates. The inelastic deformation was studied by
analysing the remnant indent morphology using atomic
force microscopy. A free-volume mechanism was proposed
for interpreting these observations quantitatively.