Mesoscale and Microscale Manufacturing Processes: Challenges for Materials, Fabrication and Metrology.

[attachment=18218]

Introduction
Length scales for processes and materials are generally classified as nanoscale (< 100
nm), microscale (100 nm to 100 μm) and mesoscale (> 100 μm). The length can be an external
dimension of a component, or the internal dimension of a material such as the crystalline grain
size. A comprehensive summary of the recent state-of-the art for Micro Meso Mechanical
Manufacturing (M4) is given in the NSF workshop report [1]. Material properties play an
important role for all of the manufacturing processes. The M4 report concludes that
"understanding mechanics and physics of materials at the microscale is essential", and that
"material can no longer be considered homogeneous when the process size dimensions approach
the material grain size". The overview presented in this paper will focus on material properties,
and in particular the structural properties of metals that will be used for the production of
miniaturized mechanical components and assemblies. Many of the other papers in this
conference will address the specific fabrication processes or metrology methods for
manufacturing down to the microscale or nanoscale.

Mechanical Micromachining and Materials
Milling, drilling, turning or grinding are basic mechanical
manufacturing processes used for the production of complex 3D
components. Metallic materials used are steels and nonferrous
alloys of aluminum, copper, titanium and other metals. These
engineering materials provide the range of mechanical properties
required for fabrication and end use. Manufacturing at the
microscale using mechanical processes, ie., mechanical
micromachining, requires suitable adaptation of the conventional
processes. Fig. 1a shows an example of miniaturized tooling used to
turn the demonstration microgrooves in 6061 aluminum shown in
Fig. 1b [2]. Fig. 2 shows commercially micromachined components
with overall dimensions on the order of 1-2 mm [3].



Synthesis of Nanocrystalline Metals and Alloys
Research on nc materials includes the
synthesis of particles, thin or thick films and bulk
material along with the characterization of their
properties. The state of the art is described in
recent reviews [5]. Materials can be metals,
ceramics or polymers.



Mechanical Properties of Nanocrystalline Metals and Alloys
The mechanical properties of nc metals and alloys will be a key factor in determining
their success as optimum materials for manufacturing. For machining, properties such as
strength, ductility and work-hardening capacity determine tool forces, surface finish and features
such as shear localization or burr formation. For end use of a component or an assembly,
performance can be limited by properties such as fatigue life, wear resistance and fracture
toughness. Although a large number of studies have been done on the mechanical properties of
nc materials, a fundamental understanding of the deformation mechanisms and a reliable
database of the engineering properties is just beginning to emerge [6,7].