High aspect ratio micro mechanical structures made of bulk metallic glass

A new processing route for the replication of high aspect ratio microstructures from a silicon wafer into a bulk metallic glass is presented. The approach bases on a casting process with separation of mold filling and quenching in time. Therefore a Zr-based bulk glass forming melt is applied onto a surface microstructured silicon mold with a protective layer, both at a temperature high enough to allow complete wetting of the wafer by the melt. Given enough time, open channels of high aspect ratios are completely filled by the melt which spreads over the wafer. From this state, the mold and the melt are quenched at a rate high enough to suppress crystallization of the glass forming melt. The resulting surface microstructured part out of bulk metallic glass with a high strength, a high elastic limit and good corrosion and abrasion resistance ideally meets the requirements of polymer microinjection molding tools. The wetting behavior of the Zr-based melt on the protective layer and the stability of the protective layer against dissolution in the melt are crucial to this new process and are studied for the alloy Zr52.5Cu17.9Ni14.6Al10Ti5 and silicon wafer molds with different silicon oxide protective layers.