Effect of Different Cooling Rates in High Rheological Rate Forming Process on Mechanical Properties of Zr57Cu20Al10Ni8Ag5 Bulk Metallic Glass

Abstract

The influence of cooling rates on the mechanical properties of a Zr-based bulk metallic glass prepared with high rheological rate forming (HRRF) was investigated and compared with traditional suction cast methods. Amorphous samples of Zr57Cu20Ni8Al10Ag5 were prepared in copper molds with different sizes in order to obtain different cooling rates for both HRRF and traditional cast methods. These specimens were subjected to compression experiments, including microhardness testing, X-ray diffraction testing and differential scanning calorimetry analysis. The results indicate that the plasticity of the samples formed by HRRF are higher than that of the as-cast ones at the same cooling rates, while the microhardness manifests the opposite principle. As the cooling rate increases further, the difference in plasticity further increases between two methods, indicating that the plasticity of metallic glasses is more sensitive to cooling rates during the HRRF process. At the core of this phenomenon is the fact that HRRF methods can introduce more free volume into glasses than traditional cast methods with an elevated cooling rate are able to.