Perfectly plastic flow in amorphous silica

Using in situ compression in a SEM, we have directly demonstrated plastic yielding in uniaxial compression for amorphous silica. A decent pîllar is turned into a pan-cake within dozens of seconds. Of course its (original) diameter is little more than 2 microns...

Figure : three stages of the compression of a silica pillar, a few microns across. The flattening without fracture is the result of extensive plasticity.

More quantitatively, we have demonstrated that this plastic flow occurs without hardening. On the theory side, this was expected since the amorphous structure leaves no mechanism for hardening... but experimetally not easy to prove, because it requires careful assessment of the section.

Reference :
Perfectly plastic flow in silica glass
Kermouche, G. ; Guillonneau, G. ; Michler, J. ; Teisseire, J. ; Barthel, E.
Acta Materialia 114 (2016) 146-153