Thermal processing map and thermoplastic forming map of Zr-based bulk metallic glass in the supercooled liquid region

Abstract

In order to make the bulk metallic glass (BMG) better used in micro electro mechanical system (MEMS), the rheological behavior of (Zr0.6336Cu0.1452Ni0.1012Al0.12)99.4Y0.6 BMG in the supercooled liquid phase region (SCLR) was studied, and the thermal processing map and the thermoplastic forming map were constructed in this paper. The Time-Temperature-Transformation (TTT) curve was established according to the crystallization incubation time of (Zr0.6336Cu0.1452Ni0.1012Al0.12)99.4Y0.6 BMG at different temperatures in the SCLR, which provided a theoretical basis for the time and temperature selection of thermal forming. Furthermore, the results show that the flow stress and viscosity coefficient of the BMG in the SCLR are strongly dependent on temperature and strain rate. The flow stress tends to decrease with the increase of temperature and the decrease of strain rate. When the temperature is 703 K with the strain rate of 5 × 10−4 s−1, the flow stress value is only 5 MPa. Meanwhile, the viscosity coefficient of the alloy remain approximately constant at 703 K, showing Newtonian fluid characteristic. It can be concluded that the alloy has excellent thermal processing property and thermoplastic forming (TPF) ability at temperature of 698–703 K, and thermoplastic forming ability is less affected by the strain rate within this temperature range.