Research On The Mechanical Properties Of The Zr-based Metallic Glass Under Nanoindentation

The outstanding mechanical performance of bulk metallic glass（BMG）makes it apotential structural material. However, the limited plasticity restricts the application ofbulk metallic glass. Compared with crystalline substances, deformation mechanism ofmetallic glass has not been clearly established, but the research on the mechanicalproperties of the metallic glass is quite important.Being two means to change the microstructure of BMG, pressure and temperatureare two factors used in this experiment of this paper. Zr-based BMG are treated underlaser, at different pressures and temperatures. The mechanical properties are studied bynanoindentation after treatment.Cyclic nanoindentation test were carried out on Zr-based BMG before and aftertreatment. From the designed quasi-static and incremental cyclic experiments at loadingrates ranging from300to3000μN/s and at ambient temperature, we observed significantdifference in inelastic deformation as a function of solicitation modes. Under incrementalcyclic loadings, the hardness of the BMG increased each time when the sample wasreloaded immediately after unloading and then gradually reduced before the nextunloading. In contrast, we found that quasi-static cyclic loadings induced a mechanicalsoftening which appears to be dependent on the number of cycles and the loading rates.The structure of Zr-based BMG changed after the laser treatment. The hardnessincreased after the treatment. Pop-in phenomenon can be seen in this experiment and itappears to be dependent on the loading rates. The lower of the loading rate, the moreobvious of the pop-in. Compared to the sample before treatment, the pop-in phenomenonappears more evident. Creep can been observed before and after the laser treatment.Creep deformation increased with the loading time. The rate of creep deformation isfaster at the primary period than the next steady period.We can see from the X-ray spectrum, the higher of the pressure, the easier tocrystallize treated below the Tgtemperature of Zr-based BMG. The higher of the pressure,the more difficult to crystallize treated over the Tgtemperature. The hardness increasedwith the pressure increase. However, the value of the elastic modulus appeared to decreased with the pressure increase. The value of hardness and elastic modulusdecreased after crystallization.