The discipline of
Materials Science and Engineering can sometimes be subdivided into Materials
Science and Materials Engineering sub-disciplines. Strictly speaking, Materials
Science involves investigating the relationships that exist between the
structures and properties of materials. In contrast, materials engineering is
on the basis of these structure–property correlations, designing or engineering
the structure of a material to produce a predetermined set of properties. From
a functional perspective, the role of a materials scientist is to develop or
synthesize new materials, whereas a materials engineer is called upon to create
new products or systems using existing materials and/or to develop techniques
for processing materials. Most graduates in materials programs are trained to
be both materials scientists and materials engineers. Structure is at this
point a nebulous term that deserves some explanation. In brief, the structure
of a material usually relates to the arrangement of its internal components.
Subatomic structure involves electrons within the individual atoms and
interactions with their nuclei. On an atomic level, structure encompasses the
organization of atoms or molecules relative to one another.
The next larger
structural realm, which contains large groups of atoms that are normally
agglomerated together, is termed microscopic, meaning that which is subject to
direct observation using some type of microscope. Finally, structural elements
that may be viewed with the naked eye are termed macroscopic. The notion of
property deserves elaboration. While in service use, all materials are exposed
to external stimuli that evoke some type of response. For example, a specimen
subjected to forces will experience deformation or a polished metal surface
will reflect light. A property is a material trait in terms of the kind and
magnitude of response to a specific imposed stimulus.
Generally, definitions
of properties are made independent of material shape and size. Virtually all
important properties of solid materials may be grouped into six different
categories: mechanical, electrical, thermal, magnetic, optical and
deteriorative. For each there is a characteristic type of stimulus capable of
provoking different responses. Mechanical properties relate deformation to an
applied load or force; examples include elastic modulus (stiffness), strength
and toughness. For electrical properties, such as electrical conductivity and
dielectric constant, the stimulus is an electric field. The thermal behavior of
solids can be represented in terms of heat capacity and thermal conductivity.
Magnetic properties demonstrate the response of a material to the application
of a magnetic field and for optical properties, the stimulus is electromagnetic
or light radiation; index of refraction and reflectivity are representative
optical properties. Finally, deteriorative characteristics relate to the
chemical reactivity of materials. In addition to structure and properties, two
other important components are involved in the science and engineering of
materials namely; processing and performance. With regard to the relationships
of these four components, the structure of a material will depend on how it is
processed. Furthermore, a material’s performance will be a function of its
properties. Thus, the interrelationship between processing, structure,
properties and performance can be depicted thus: PROCESSING-STRUCTURE-PROPERTIES-PERFORMANCE which depicts the
Material Science Tetrahedron. They are the four components of the discipline of
materials science and engineering.
No comments:
Post a Comment