Superplastic forming of micro components

#This invention relates to the formation of miniaturized shaped components such as components for microelectromechanical systems (MEMS) and nanoelectromechanical systems (NEMS).

#Current technology for producing MEMS and NEMS devices is based mainly on silicon microfabrication techniques. Silicon, however, has relatively poor mechanical properties which rendered forming techniques difficult. New materials and fabrication techniques are need to produce micro components with greater reliability.

#Nanostructured materials exhibit exceptional strength and fatigue properties, rendering them good candidates for high performance micro components. Fabrication is difficult, however, because conventional machining techniques available for larger components do not readily scale down for use with micro components.

#FIG. 1 is graphical presentation of elongation and temperature data for superplastic material of the type deformed in this invention.

#FIGS. 2 and 3 are schematic illustrations of equipment for carrying out the invention.

#FIG. 4 is a schematic illustration of a multiple-cavity extrusion die for carrying out the invention.

#Superplastic materials are those materials which exhibit superplasticity when heated to an appropriate temperature under the proper conditions. Superplasticity, generally, is the capacity of metal to undergo larger uniform plastic deformation without rupture. Structural superplasticity has been defined many ways, but for purposes of this description refers to the ability of a metal to undergo more than about 200% elongation under tension without rupturing. High strain rate superplasticity is defined as a minimum strain rate of 10−2 s−1 (Glossary of Terms Used in Metallic Superplastic Materials, JIS-H-7007, p. 3, Japanese Standards Association, Tokyo, Japan (1995)). Among the bulk superplastic materials which are processed in accordance with this invention are aluminum alloys which have been processed to have superplastic properties, other alloys to which have been imparted nanocrystalline microstructure (average grain size less than 100 nanometers) by processes such as torsional strain (TS)-SePD as described by Mishra et al. in J. Metals 51(1), 37 (1999), and metallic glass.

#Metals have been treated by a variety of methods to impart superplasticity to enable the formation of small and intricate components. As a general proposition, with aluminum alloys, superplasticity is imparted by treating the metal to yield a fine grain size of less than about 20 microns and high angle grain boundaries.

#Bulk metallic glasses are amorphous and exhibit superplasticity in a narrow temperature range, between the glass transition temperature and the crystallization temperature.