4 research outputs found
Bridging room-temperature and high-temperature plasticity in decagonal Al-Ni-Co quasicrystals by micro-thermomechanical testing
Ever since quasicrystals were first discovered, they have
been found to possess many unusual
and useful properties. A long-standing problem, however, sig
nificantly impedes their
practical usage: steady-state plastic deformation has only
been found at high temperatures or
under confining hydrostatic pressures; at low and intermediate temperatures, they are very
brittle, suffer from low ductility and formability and, con
sequently, the
ir
deformation
mechanisms are still not clear. Here, we systematically
study the deformation behavior of
decagonal Al-
Ni
-Co quasicrystals using a micro-thermomechanical technique ove
r a range of
temperatures (25-500 °C), strain rates, and sample sizes
accompanying microstructural
analysis. We demonstrate three temperature regimes for th
e quasicrystal plasticity: at roo
m
temperature, cracking controls deformation
;
at 100-300 °C, dislocation activities control the
plastic deformation exhibiting serrated flows and a con
stant flow stress; at 400-500 °C
,
diffusion enhances the plasticity showing homogenous deformation. The micrometer-sized
quasicrystals exhibit both high strengths of ~2.5-3.5 GPa and
enhanced ductility of over 15%
strains between 100-500 °C
.
This study may lead to an improved understanding of
quasicrystal plasticity in the low- and intermediate temperature regimes.Y.Z. acknowledges the financial support through the Swiss National Science Foundation (SNF Grant: 200021_143633