Hot Embossing of Zr-Based Bulk Metallic Glass Micropart Using Stacked Silicon Dies

Zhijing Zhu,Chuanyun Yi,Yichun Zhang,Guanglan Liao,Tielin Shi,Yang Gao

doi:10.1155/2015/179714

Abstract

We demonstrated hot embossing of Zr65Cu17.5Ni10Al7.5bulk metallic glass micropart using stacked silicon dies. Finite element simulation was carried out, suggesting that it could reduce the stress below 400 MPa in the silicon dies and enhance the durability of the brittle silicon dies when using varying load mode (100 N for 60 s and then 400 N for 60 s) compared with using constant load mode (200 N for 120 s). A micropart with good appearance was fabricated under the varying load, and no silicon die failure was observed, in agreement with the simulation. The amorphous state of the micropart was confirmed by differential scanning calorimeter and X-ray diffraction, and the nanohardness and Young’s modulus were validated close to those of the as-cast BMG rods by nanoindentation tests. The results proved that it was feasible to adopt the varying load mode to fabricate three-dimensional Zr-based bulk metallic glass microparts by hot embossing process.

Highlights

With superior strength, high hardness, large elasticity, excellent wear, and corrosion resistance, BMGs (Bulk Metallic Glasses) are recognized as promising materials for structure, sensor, wear-resistant, and corrosion-resistance coating [1, 2]
As silicon owns high strength and hardness and can be structured into micro geometry with high precision and low surface roughness by lithography and etching process, it has been widely used for microdies in hot embossing process to form BMG microparts [19, 22]
Most of microparts fabricated by the hot embossing process using silicon dies are quasi three-dimensional structures, which cannot satisfy diverse requirements in MEMS [24]

Summary

Introduction

High hardness, large elasticity, excellent wear, and corrosion resistance, BMGs (Bulk Metallic Glasses) are recognized as promising materials for structure, sensor, wear-resistant, and corrosion-resistance coating [1, 2]. To fabricate BMG microparts, there are mainly two processes: direct casting and thermoplastic forming [5] The former casts the molten alloy into a microdie followed by fast cooling to inhibit crystallization [6, 7]. This process is usually carried out to form macroscale BMG materials [8, 9], which can be used as feedstock for other processes [10]. As silicon owns high strength and hardness and can be structured into micro geometry with high precision and low surface roughness by lithography and etching process, it has been widely used for microdies in hot embossing process to form BMG microparts [19, 22]. With good appearance was hot embossed successfully, its glassy state was detected by DSC (Differential Scanning Calorimeter) and XRD (X-Ray Diffraction), and the mechanical properties were validated by nanoindentation tests

Experimental

Finite Element Simulation

Results and Discussion

Conclusions