Bridging room-temperature and high-temperature plasticity in decagonal Al–Ni–Co quasicrystals by micro-thermomechanical testing

Abstract

(2016) Bridging room-temperature and high-temperature plasticity in decagonal Al-Ni-Co quasicrystals by micro-thermomechanical testing, Philosophical Magazine, 96:32-34, 3356-3378, DOI: 10.1080/14786435.2016 Ever since quasicrystals were first discovered, they have been found to possess many unusual and useful properties. A long-standing problem, however, significantly impedes their practical usage: steadystate 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, consequently, their deformation mechanisms are still not clear. Here, we systematically study the deformation behaviour of decagonal Al-Ni-Co quasicrystals using a micro-thermomechanical technique over a range of temperatures (25-500 °C), strain rates and sample sizes accompanying microstructural analysis. We demonstrate three temperature regimes for the quasicrystal plasticity: at room temperature, cracking controls deformation; at 100-300 °C, dislocation activities control the plastic deformation exhibiting serrated flows and a constant flow stress; at 400-500 °C, diffusion enhances the plasticity showing homogenous deformation. The micrometersized quasicrystals exhibit both high strengths of ~2.5-3.5 GPa and enhanced ductility of over 15% strains between 100 and 500 °C. This study improves understanding of quasicrystal plasticity in their lowand intermediate-temperature regimes, which was poorly understood before, and sheds light on their applications as small-sized structural materials.

Combinatorial investigation of Al–Cu intermetallics using small-scale mechanical testing

“…However, in this study, all brittle intermetallic phases demonstrate significant plasticity during micro-scale testing. This results from a wellknown size-induced brittle-to-ductile transition in brittle materials [39], which has been previously observed in semiconductor materials such as silicon [40,41] and even quasicrystals [42].…”

Materials selection in micro- or nano-mechanical design: Towards new Ashby plots for small-sized materials

“…It should be noted that Figure 4 represents the size effects of materials that are only measured at room temperature and nearly identical strain rate (~10 -3 s -1 ) and the size dependence of a material strength may depend on the testing temperature and strain rate. Some previous studies demonstrate three-dimensional (3D) size-temperature-strength deformation maps, such as in Si [38] and quasicrystals [43], but the systematic studies on various materials over a large temperature and strain rate range are still scarce. Nevertheless, although the detailed underlying strengthening mechanism may vary among different materials, this general trend in Figure 4 can be technologically important, providing a common guide to predict material strengths at multi-scales.…”

Cold Spray Additive Manufacturing: Microstructure Evolution and Bonding Features

“…It is highly desirable to measure the mechanical properties of microscale particles at high strain rates over a large temperature range. Over the past decades, many new metallic materials have been developed and investigated. There are new opportunities to employ the cold spray method to these emerging metallic systems, including typical fcc HEAs, refractory bcc HEAs, − nanostructured alloys, , and quasicrystals, − providing a fundamental understanding of bonding mechanisms and microstructure evolution of these emerging materials processed by cold spray. …”