Mold filling dynamics of thermoplastic forming of bulk metallic glass MEMS parts: Numerical simulation and comparisons with experiment

Abstract

Bulk metallic glasses (BMGs) exhibit excellent mechanical properties as well as unique thermoplastic net formability, which make them ideal materials for MEMS application. Due to the diversity of MEMS configurations, the predicting and controlling of mold filling process are crucial for reliable replication, remain poorly understood. In this paper, combined with finite element simulations and experiments, the mold filling dynamics of BMGs in the supercooled liquid region (SCLR) are systematically investigated. The phase diagram predicting the range of mold geometric parameters which allow for reliable replication is determined, which agrees with experimental observations. Meanwhile, it is found that if not designed properly, irregular shape molds which are widely used in MEMS, can lead to complex filling dynamics and replication failure. Our work provides new insights into the mold filling dynamics of highly viscous fluids and the guideline for thermoplastic molding of BMGs, which could fascinate the application of BMGs in MEMS. • The mold filling dynamics of BMGs in the supercooled liquid region are systematically investigated. • It is found that irregular shape molds widely used in MEMS can lead to complex filling dynamics and replication failure. • The phase diagram predicting the range of mold geometric parameters which allows for reliable replication is determined.