Atomic Force Microscopy Applied to the Study of Metallic Glasses Alloys Based on CuZrAlEr and CuZrAl

Abstract

Metallic glasses are materials that present absence of periodic atomic order of long scale and seem to be promising to application in the fields of science and engineering. They were first obtained in 1960 through the technique of rapid cooling with thinner thickness, but the development of new production techniques and the combination of elements allowed the production of amorphous condition in millimeter-thick alloys, which received the denomination of bulk metallic glasses. Two alloys of metallic glasses, with the Cu47.5Zr45.5Al5Er2 and Cu47.75Zr47.75Al4.5 compositions, were here studied. Their production was made through arc furnace, and the characterization through X-ray diffraction (XRD), with Cu Kα radiation, Scanning Electron Microscope (SEM), ultra-microhardness tester, and Atomic Force Microscopy (AFM), from Nanoscope IIIA. The analysis of the atomic structure of the Cu47.5Zr45.5Al5Er2 alloy showed great structural disorder, and the Cu47.75Zr47.75Al4.5 sample presented peaks arising from crystalline phases, like Zr4Cu2O (big cubic phase) formed due to the affinity between zirconium and oxygen, in the amorphous matrix. Using the AFM, the Cu47.5Zr45.5Al5Er2 sample presented the values of 2.15 nm from Ra (roughness average) and 3.14 nm from RMS (Root Mean Square). Another sample has shown better results of roughness, where Ra was 1.88 nm and the RMS was 2.53 nm. As it is known, roughness is an import tribological parameter in materials and lower values allow that less surface area is exposed to harmful atmospheric effects such as corrosion, as evidence of the advantage of the sample with erbium.