Quasicrystals (QCs) are structures with orientational order that can exhibit rotational symmetries (e.g., fivefold, eightfold, tenfold, and twelvefold) forbidden by classical laws. The discovery of QCs was recognized by the Nobel Prize in Chemistry in 2011, awarded to Professor Dan Shechtman. Due to their aperiodicity, these materials are expected to have unique properties that differ from those of ordinary metals, which opens up prospects for their industrial application.
The effect of mechanical activation of a mixture of carbon powder and quasicrystalline AlCuFe alloy on the microhardness of the resulting composite material was investigated. Mechanical activation was carried out in a planetary mill, which led to dispersion and mixing of the components at the micro level.
It is shown that the microhardness of the composite increases significantly compared to the microhardness of the original components. This effect is explained by the formation of a strengthening structure due to the uniform distributionIn this work, we studied composites consisting of an icosahedral Al65Cu20Fe15 quasicrystal and mechanically activated carbon (graphite). Under a gentle grinding mode (100 rpm) of a mixture of the quasicrystalline phase and mechanically activated carbon (MAC), the quasicrystalline (CC) phase is preserved, as well as a small amount of the nanocrystalline phase B2 is formed. The study of the mechanical properties of sintered samples (at 200 °C) revealed an increase in the hardness of the composite materials with the addition of up to 5 at.% MAC. The hardness value increases by almost 0.37 times compared to a stable Al–Cu–Fe quasicrystal. It is assumed that the increased hardness is due to changes in the microstructure caused by the addition of 5 at.% MAC. The study demonstrated the possibility of creating composite materials based on MAU and KK with improved and reliable properties.
Mechanical activation promotes the creation of crystal lattice defects and an increase in the dislocation density in quasi-crystalline particles, which also promotes an increase in hardness. In addition, the interaction between carbon and the quasi-crystalline phase can lead to the formation of carbides with high hardness. The obtained results allow us to consider composites based on mechanically activated carbon and quasi-crystals as promising materials for use in conditions of increased requirements for wear resistance and hardness.
Author: TP Yadav, Devinder Singh, RS Tiwari, ON Srivastava
Institute: Surface Science Centre and Department of Physics, University of Liverpool, Liverpool, L69 3BX, UK, Centre for Advanced Studies, Department of Physics, Banaras University, Varanasi-221005, India