What exactly is aluminum? Is it a natural element or a man-made alloy? The answer is: both! But aluminum can take on a variety of shapes and forms depending on how it’s treated. Read on to learn more about this important element and how it has come to play a part in a variety of uses that are essential to our lives.
What is Aluminum?
Aluminum (Al) is a chemical element that appears in Group 13 (IIIa, or boron group) of the periodic table. Its compounds are present in varying degrees in almost all rocks, vegetation, and animals. According to Brittanica, aluminum is the most abundant metallic element in the Earth’s crust and the most widely used non-ferrous metal.
Non-ferrous metals do not contain any iron and are non-magnetic, whereas ferrous metals do contain iron and are magnetic. Aluminum’s lack of magnetic properties makes it a suitable material for many end uses.
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Although aluminum is ubiquitous, it doesn’t occur naturally by itself because its chemical properties make it highly reactive to other elements; therefore, it must be refined from ore. Bauxite ore is the most common source of aluminum. In order for bauxite to yield alumina or aluminum oxide, it must first be chemically treated. While global demand for aluminum products is increasing, the good news is that bauxite is an abundant resource. Its reserves are expected to last for centuries.
What is Aluminum Alloy?
Aluminum by itself is a soft, pliable material. In order to make it more usable for a variety of products and applications, it goes through an alloying process where it is combined with other elements such as silicon, copper, magnesium, manganese, and zinc in order to enhance its strength and other properties.
For classification purposes, aluminum alloys are identified by four-digit numbers. The first digit identifies a general class, or series, characterized by its main alloying elements.
Alloys in the 1xxx series are the closest to pure, unalloyed aluminum. In fact, in this series, aluminum comprises about 99% of the chemical makeup. Because of the softness of this grade of aluminum, it has excellent weldability, but is not typically used for applications requiring high strength.
Aluminum Alloy Series Chart by Properties
Adding different alloying elements produces different results in terms of finished products.
|Main Alloying Elements
|High corrosion resistance. Excellent finishability. Easily joined by all methods. Low strength, poor machinability. Excellent workability. High electrical conductivity.
|High strength. Relatively low corrosion resistance.
Excellent machinability. Heat treatable.
|Low to medium strength. Good corrosion resistance.
Poor machinability. Good workability.
|Cannot be extruded.
|Low to moderate strength. Excellent marine corrosion resistance. Very good weldability.
|Magnesium and Silicon
|Most popular extrusion alloy class. Good strength.
Good corrosion resistance. Good machinability.
Good weldability. Good formability Heat treatable.
|Very high strength. Poor corrosion resistance.
Good machinability. Heat treatable.
Chart source: Aluminum Extruders Council
Choosing the Right Aluminum for Common Applications
When selecting the appropriate aluminum grade for a project, you will want to consider the following needs:
- How important is strength?
- How workable is the material?
- Can it be formed?
- What level of weldability or machining is needed?
- Is corrosion resistance important?
- Is heat treating necessary?
The 1xxx, 3xxx, and 5xxx series are non-heat-treatable alloys; their strength can be developed through cold work after the extrusion process is complete.
The 2xxx, 6xxx, and 7xxx series are heat-treatable and have the highest strength of all aluminum alloys.
Here are some common applications for the different aluminum alloy series:
- 1000 – applications in which strength isn’t a priority. This material shows up frequently in electrical applications like power grid lines, in food packaging trays, manufacturing rotors, or in cladding corrosion-prone alloys.
- 2000 – aircraft and transportation structural components
- 3000 – chemical equipment, furniture, condensers, heat exchangers. and pressure vessels
- 5000 – welded structures, storage tanks, pressure vessels, saltwater applications
- 6000 – the most versatile series, used in a variety of extruded products. Appears in transportation and general structures.
- 7000 – used in applications requiring high strength and stress resistance, such as automotive and aerospace products
Whatever your end goal, aluminum is a winner when it comes to versatility. If you need assistance selecting the right aluminum alloy, Kloeckner Metals’ experts are ready to help!
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