Metals and Metallic Alloys

Metals and Metallic Alloys

Properties

The terminology “Metals” is a general term that refers to metals and metallic alloys (Tisza, 2001, p.15). Metals have an abundant natural occurrence comprising more than half of natural elements. Pure metals contain only one metallic material component, for example, aluminum, iron, and copper. Alloys of metals are combinations of more than one component (Dennis, 2010). The base component (basic material) of metallic alloys is a metal, but the complimentary component or material may not necessarily be a metallic. Metals have a crystalline structure in which atoms align themselves in a regular manner (Ibid). Materials of metallic nature have high thermal and electrical conductivity, lustrous appearance, relatively high rigidity, and relative flexibility. The atomic and crystal structure of metallic alloys determines the direct properties of metallic alloys.

Classification

Metals are of two prime groups. The first group comprises ferrous metals and iron-based alloys (Fesquet, 2002). This group of materials has iron as the main material. It contains steel and cast iron which are the most essential materials in engineering. The second main group comprises the non-ferrous metals and alloys. These include aluminum, titanium, copper, and many other metals including their alloys. Non-ferrous metals are many and are the main components used in alloys.

Metallic Alloys

An alloy of a metal is a combination of more than one material (Srinivasan, 2010). One of the elements in the combination must be a metal with a high proportion for it to qualify as a metallic alloy. The other components in the combination may be metals or non metals. Brass and steel are examples of metallic alloys. Brass is a combination of copper and zinc while steel combines iron and carbon. Metallic alloys have a wide variety of applications in the manufacturing industry. Pure metals are useful in situations that require specificity as regards properties such as high ductility, high electrical conductivity, or high corrosion resistance. These properties exist at maximum values in pure metals. However, alloys improve mechanical properties such as hardness, yield point, and tensile strength.

Alloys can either exist in a single phase, or as a mixture (Chatterjee, 2007). Phases are states of materials that are physically distinct or homogeneous. An alloy in the metal state has three possible phases: pure metal, solid solution, and intermediate phase. If a material has a single phase, then it can either be a solid solution or intermediate phase. If the alloy is a mixture, then it could have a composition made combination of any of the three phases. A solid solution is a state of an alloy that has the solute atoms distributed in the solvent matrix and has the same structure of the solvent. A solvent is the component present in a higher proportion than the other component, the solvent (Habashi, 1998). Intermediate phases (chemical compounds) comprise two different elements with divergent electrochemical properties.

General Applications

Metals have a wide variety of functions ranging from structural to chemical functions. Metals are materials that are most common in engineering functions including the manufacture of various devices and equipments (Tisza, 2001, p.16). These include household appliances, equipments for aircraft and astronautics, car components, or machines and devices. These are devices and equipments that contain metals as the base materials. In most cases, the manufacture of these metals use metallic alloys. The manufacture of aircraft turbine engine uses super alloys to increase the power and efficiency. A nickel-based super alloy can withstand extreme temperatures of up to 1000^◦C, and, so, is applicable in the manufacture of the engine.

Uses of Metallic Alloys

Metallic alloys have several essential functions (Habashi, 1998).

a) Bearing alloys: These are alloys applied in the manufacture of metallic components that encounter sliding contact under pressure with another surface. The bearing alloys comprise hard inter metallic particles that have the capacity to resist wear. Bearing alloys have these particles embedded in the matrix of softer material.

b) Corrosion-resisting alloys: These are noble methods that resist corrosion and include precious metal alloys. Some alloys resist corrosion because they develop a protective oxide film. These include stainless steel and aluminum alloys. Other corrosion resisting alloys are Monel and Incol.

c) Dental alloys: These are alloys used for hardening purposes. Examples include silver based alloys and dental-based alloys. Silver based alloys, made of silver amalgam, contain small amounts of tin, zinc, and copper for the purpose of hardening.

d) Die-casting alloys: These are alloys that have low melting temperatures such that, in the liquid form, injection into steel dies can occur under pressure. The castings are useful for household and office appliances, and automobile parts. These appliances and vehicle parts are complex.

e) Fusible Alloys: These are alloys with extremely low melting points used for several purposes such as in fusible elements, in automatic spinners.

f) High temperature alloys: These alloys are strong at high temperatures such as in jet engines, power generating plants, and gas turbines. They also resist oxidation by steam and fuel-air mixtures.

g) Joining alloys: These are alloys used for bonding by soldering, brazing and welding. They provide filler material will lower melting point than that of the joined parts.

h) Light-metal alloys: These are alloys composed of low density elements such as magnesium, titanium, and aluminum. They are useful in the age hardening processes.

i) Low-expansion alloys: These are alloys that do not change their dimensions over the atmospheric temperature range. Their uses include the manufacture of temperature-sensitive devices such as watches and glass-to-metal seals.

j) Magnetic alloys: These are alloys applicable for magnetization purposes. Purposes include magnetic cores of transformers and motors. For instance, an alloy of silicon and ferrite applies to alternating current applications.

k) Precious-metal alloys: Precious metals are scarce and beautiful. Uses include application in electronic devices, temperature-measuring devices, and catalytic applications.

l) Metallic glasses: These are alloys that are strong, corrosion resistant, and tough. Rapid solidification technology is one of the applications of metallic glasses.

m) Prosthetic alloys: These are alloys used for surgical procedures such as implants. Corrosion property is essential for use in these alloys.

References

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