The wear phenomenon in which hard particles, in this case the quasicrystalline alloy Al62Cu25.5Fe12.5, leave marks on the surface of a softer metal can be described as abrasive smearing. This process differs from classical abrasive wear, where micro-cutting or micro-plowing of the surface occurs.
In the case of smearing, quasicrystals, which have high hardness and brittleness, do not penetrate deeply into the soft metal under the effect of load, but rather deform its surface layer. In this case, the abrasive particles can fragment, and their fragments are “smeared” over the surface, forming a thin film or individual microscopic areas.
The mechanism of smearing of the Al62Cu25.5Fe12.5 abrasive is determined by its specific properties. Quasicrystals, unlike conventional crystalline materials, have icosahedral symmetry, which leads to the absence of translational periodicity in their structure. This complicates the sliding of dislocations and contributes to the high hardness and brittleness of the material.
When in contact with soft metal, under the influence of load, quasicrystals deform the surface layer, causing plastic flow of the material. As a result, microscopic grooves and depressions are formed, in which abrasive particles are retained. Further sliding movement leads to the “smearing” of these particles over the surface, forming a thin film or individual areas with an increased concentration of quasicrystalline alloy.
The intensity of smear wear depends on a number of factors, including the hardness and roughness of the abrasive surface, the properties of the soft metal (hardness, plasticity), the magnitude of the applied load and the sliding speed. Analysis of the microstructure of the worn surface, as well as the study of the composition and distribution of elements using modern microscopy and spectroscopy methods, allows us to establish the wear mechanism and assess its intensity.
In order to compare with traditional hard abrasives (diamond, aluminum oxide, silicon dioxide), the polishing characteristics of Al Cu25.5 12.5 quasicrystal on copper, aluminum and austenitic stainless alloys were studied. Unlike the three standard abrasives, the wear mechanism similar to lubrication was dominant for the quasicrystalline abrasive, which was expressed in a smaller size of the resulting depressions relative to the depth of the removed layer of material.
By producing a smooth surface with minimal material removal, quasi-crystalline abrasive polishing can open up new perspectives in areas where low wear and precision surface finishing are important.
Author: Yongjun Chen,Jianbin Qiang, Chuang Dong
Institute: Key Laboratory of Material Modification by Laser, Ion and Electron Beams (Ministry of Education), School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024, China