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