Superplastic nano/microforming of bulk metallic glasses and the application to micromachines

Abstract

Bulk metallic glasses as second-generation amorphous alloys exhibit Newtonian viscous flow under very low stresses in the supercooled liquid temperature range and furthermore, the materials exhibit superior micro/nano formability and good geometrical transferability of die. These alloys are therefore expected to become some of the most useful materials for fabricating nano-/micro-machines (MEMS) and devices. The present paper demonstrates the macroscopic and microscopic deformation behavior of La-, Zr-, Pd- and Pt-based bulk metallic glasses, as well as micromachine production methods for the materials. Nano/microforming techniques are shown as follows: microextrusion with microdies made of laser-micromachined polyimide and of Ni by UV-LIGA (lithography and electroforming) process, submicron imprinting with silicon die fabricated by EB lithography and etching, microforging of microgear of 10 /spl mu/m in module with Ni-microdie fabricated by UV-LIGA process, microforging of micro cantilever with laser-micromachined polyimide die. As a result, bulk metallic glasses are highly useful for realizing high-performance micro-actuators and microstructures due to their excellent characteristics as functional or structural materials, including isotropic homogeneity free from crystalline anisotropy on micrometer and nanometer scales.