Introduction to Metal Alloys

In engineering topics, when we talk about materials, these are the basic substances combined and produced to be used in operations, processes and building machines. During early times, only natural materials are available such as stones and woods. But as modernization approaches, materials that are made by men are now available and are continuously being improved. Typically, materials may fall into four major classifications: metals and metal alloys, ceramics, polymers and composites. Metals are the most common materials being used and handled by mechanical engineers especially in designing and building machines. Metal alloys are also used in various thermocouple types to measure temperatures.

Metal alloys

Metal alloys are the most common materials used by mechanical engineers in designing and inventing machines. Metal alloys are mixtures of two or more metals combined to produce a better property. Metal alloys also play an important role in the history of civilization. The period was named after a certain metal alloy was discovered and was widely used over that era such as bronze ages and iron era.
There are two major types of metal alloys:

A. Ferrous metals – these are metal alloys that contain amount of iron. Typical ferrous metals used in engineering are the following:
* Cast iron – an iron formed by casting. These are commonly used for making gears, block and brake drums.
* Carbon steel – used to make drill bits and other cutting tools. This type can be classified as low, medium and high carbon steel depending on the amount of carbon it contains. Low carbon steel usually contains 0.1 to 0.25% of carbon and is used for carburizing. Medium carbon steel has 0.25 to 0.50% carbons and is usually tempered to hardness. High carbon steel contains more than 0.5% of carbon and is commonly used for wear-resisting parts such as springs.
* Stainless steel – alloy of iron, nickel and chromium.
* Wrought steel – commonly made by hammering, rolling or drawing and is used for bars and tube pipes.

B. Non-ferrous metal alloys – metal alloys that do not contain iron. Common types are the following:
* Brass – alloy of copper and zinc commonly used for screws, pistons, piston rods and shafts.
* Bronze – alloy of copper and tin, with small amount of phosphorous and is commonly used for clutch disks and pump rods.

Metal processes and heat treatment

Aside from adding an alloy to a metal, metal treatment and processes are done to achieve greater property. Common treatments and processes are the following:

• Annealing – process used to soften metal to improve its machineability.
• Hardening – usually done with quenching process to increase hardness of metals.
• Normalizing – used to provide uniform structure of metals.
• Stress relieving – used to reduce residual stress of metal.