Probing the Small-Scale Plasticity of an Icosahedral Quasicrystal I-Al-Pd-Mn at Elevated Temperatures

Quasicrystalline materials possess a unique structure that is ordered yet not periodic. Despite their special configuration and many useful properties, they are typically very brittle at temperatures below ~75% of their melting points, rendering them difficult to process and often unsuitable for practical implementation. Here, we study the mechanical behavior of a typical icosahedral quasicrystal (i-Al-Pd-Mn) using micro-thermomechanical techniques over the temperature range of 25-500 °C, which has never been explored before. A few interesting phenomena have been observed, including micro-pillar shrinkage, phase transformations, grain refinement, and thermally induced transitions in deformation behavior (from brittle fracture to serrated plastic flows, and then to homogeneous flows). Furthermore, we discuss the multiple underlying mechanisms on the mechanical behavior of the quasicrystal in this temperature regime, exploring surface evaporation/diffusion, diffusion-enhanced plasticity, dislocation activities, and grain boundary rotation/sliding. Our study bridges the gap between room-temperature and high-temperature plasticity in quasicrystals, demonstrating a new opportunity to study complex intermetallic phases in broad size and temperature regimes.