Why Metals?

Metallurgy falls within the spectrum of materials science and engineering and  by definition is the science and technology of metals in relation to their properties, production and purification. Metals have historically played a critical role in human’s civilizations and this role not only did not diminish with the advancement of societies but also continued to provide pathway to further development. The pleasure of having technologies around such as computers, smart phones, cars, airplanes, spacecrafts, implants, etc. is partly (if not largely) owed to the science of metals and a world with no metallic materials is actually an impossible world.

High popularity of metallic materials is originated from their generosity with offering variety of properties for various applications. They even allow you to design and alter their properties according to your needs. This level of willingness to cooperate is rarely observed in other groups of materials and that is why the effort to replace metallic materials has not been greatly successful so far.

This uniqueness in their properties and behaviour is largely related their atomic structures. Atomic arrangement of materials or in a more general term solids can be either highly ordered like metals or disordered such as glass. Periodically ordered atoms form crystals and numerous microscopic crystals of different orientation and size (which are called grains in metals) fuse together and form a polycrystalline metal. The area at which two grains of different orientations and sizes meet is called grain boundary. Depending on their applications, grain boundaries can appear very useful in some to highly disadvantageous in others. In the latter case, single crystals of metals are grown and used.

crystalline structure of metals from left to right: BCC, FCC, HCP
crystalline structure of metals from left to right: BCC, FCC, HCP

In crystalline materials, atomic arrangements (or crystalline structures) follow specific geometrical patterns and that geometrical pattern is very critical to their properties. The commonly observed crystalline structure of metals are face centred cubic (FCC), body centred cubic (BCC) and hexagonal close packed (HCP). Being cubic, FCC and BCC metals possesses isotropic properties and therefore preferable over HCP metals for structural applications. However, the recent urge to reduce carbon emission has resulted in a great shift to investigate, improve and apply magnesium from the family of HCP metals for structural applications duo to its incredibly light weight compared with common cubic metals such as steel.

However, it should be noted that crystalline structure does not take the whole credit for amazing properties of metals. Metallic bonding and presence of defects in the atomic arrangment contribute largely as well. I will write about defects in crystalline structure in the following posts but in conclusion, the ongoing love of human for metals does not seem to be ending anytime soon as the present rivals do not appear competitive enough yet. 

Advertisements