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Aluminum rods. Image Credit: Shutterstock.com/Yulia Grigoryeva

Aluminum Alloy: Definition, Characteristics, Types, Properties, and Applications

Learn more about this popular metals including what they're made of and its history.

Xomety X
By Team Xometry
April 15, 2023
 11 min read
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One of the most popular metals in the manufacturing sector is aluminum. It is renowned for being extremely light and having a great strength-to-weight ratio. To develop materials with unique qualities appropriate to different industries, aluminum is combined with additional elements including: copper, magnesium, silicon, and zinc to create aluminum alloys.

All kinds of products — including: consumer electronics, packaging, and parts for automobiles and airplanes — employ these alloys. Aluminum alloys come in many forms, and their particular compositions and traits tailor them to unique purposes. This article will go into further detail on the definition, traits, categories, characteristics, and uses of aluminum alloys.

What Is Aluminum Alloy?

Aluminum is a metal that can be combined with other elements including copper, magnesium, silicon, zinc, and manganese, to alter its mechanical and physical qualities. These metals are added in specific proportions to achieve the desired properties for a given application. For instance, combining magnesium with aluminum can result in a strong, light alloy ideal for use in the aerospace and automotive industries. Aluminum alloys sees extensive use in many different industries because of their low density, resistance to corrosion, and thermal conductivity. Many different items, including consumer electronics, automobiles, and aircraft, are made from aluminum alloys. For more information, see our guide on Aluminum.

What Is the History of Aluminum Alloy?

Naturally occurring compounds that contain aluminum have been known since antiquity, but aluminum’s elemental nature as a metal wasn’t confirmed until 1825. This came thanks to the efforts of German chemist Friedrich Wöhler and Danish physicist Hans Christian Ørsted. After being discovered, aluminum was difficult to process and cost more than gold. The price didn't start to drop until Henri Étienne Sainte-Claire Deville, a French chemist, started the first industrial manufacture in 1856. It would be an additional 50 years before duralumin, the first structural aluminum alloy with appreciable strength, was created. It was developed with military and industrial purposes in mind. 

What Is Aluminum Alloy Made Of?

The following are some typical elements found in aluminum alloys:

  1. Copper (Cu): Adding copper to aluminum increases its strength and hardness. An example of aluminum-copper alloy is 2024.
  2. Zinc (Zn): Aluminum-zinc alloys are known for their strength and corrosion resistance. One common example is 7075
  3. Magnesium (Mg): Aluminum-magnesium alloys are lightweight and have excellent corrosion resistance. An example of such an alloy is 5083.
  4. Silicon (Si): Adding silicon to aluminum improves its casting properties and reduces shrinkage during solidification. 4043 aluminum alloy numbers among those that offer such exceptional qualities.

It is important to remember that many additional metallic and non-metallic elements can be added to aluminum alloys to improve their properties further. For example, chromium can be used to increase corrosion resistance while magnesium can be added to increase strength and toughness. Because of this, a large number of aluminum alloys are available, each with a distinctive set of properties and potential uses.

What Are the Characteristics of Aluminum Alloy?

Here are the characteristics of aluminum alloys:

  1. Lightweight: Aluminum alloys have low densities, making them lightweight and ideal for applications where weight is a critical factor.
  2. Corrosion Resistance: The surfaces of aluminum alloys form a natural oxide layer that protects against corrosion in many environments.
  3. High Strength-to-weight Ratio: Aluminum alloys are strong and durable despite their low mass, making them useful in various applications where strength and weight must be carefully balanced.
  4. Formability: Aluminum alloys can be easily shaped and formed, making them versatile in manufacturing processes.

However, since these traits can differ significantly depending on the particular alloy in question, it is crucial to refer to the pertinent material data sheet to gain a precise understanding of a given alloy's characteristics.

What Is the Color of Aluminum Alloy?

Most aluminum alloys have a metallic silver-gray color. This is caused by the material's surface oxidation, which naturally forms a thin layer of aluminum oxide. However, different finishing techniques like anodizing, painting, or powder coating can change how they look.

What Does Aluminum Alloy Look Like?

Figure 1 is an example of an aluminum alloy: 

Slide 1 of 1
scraps of aluminum alloy
scraps of aluminum alloy
scraps of aluminum alloy

Aluminum alloy scrap.

Image Credit: Shutterstock.com/KickaPoo

Natural aluminum alloys have a metallic silver hue and a texture that can change depending on the manufacturing process.

What Are the Different Types of Aluminum Alloy?

Aluminum alloys can be categorized into different series based on their chemical makeup and physical characteristics. Some of these types are listed below:

1. 1000 Series (Pure)

Aluminum makes up at least 99% of the 1000-series alloys’ composition, with only traces of other elements. They are very thermally conductive, highly ductile, and corrosion-resistant. Pure aluminum is utilized in products like chemical tanks, conductive bus bars, and rivets. The precise composition and impurity content of the various alloys in the 1000 series is what distinguishes them from one another.

2. 2000 Series (Copper)

Copper serves as the primary alloying element in the 2000 series of aluminum alloys, giving them better strength. These alloys are machinable, can withstand high temperatures, and can be heat treated. Military, aerospace, and other high-performance applications all find them valuable. Copper content and other trace elements vary between different 2000 series alloys.

3. 3000 Series (Manganese)

Manganese is the primary alloying element in aluminum alloys from the 3000 series; it improves the metal’s corrosion resistance and formability. These alloys are not heat-treatable and have moderate strength. They are employed in cookware, automotive parts, and construction materials. They also work well when welding and anodizing.

4. 4000 Series (Silicon)

Silicon, which is the main alloying component in this series, gives aluminum excellent molten fluidity and minimal shrinkage when it solidifies. It has good machinability, moderate strength, and good corrosion resistance. In the automotive industry, it is usually used for engine blocks and other parts that need to dissipate heat efficiently. For more information, see our guide on Silicone.

5. 5000 Series (Magnesium)

The main alloying element in the 5000 series is magnesium. These versions of aluminum find relevance in vehicles, pressurized vessels, and bridges.

6. 6000 Series (Magnesium and Silicon)

The 6000 series alloys contain magnesium and silicon as the main alloying elements. They exhibit good strength, significant resistance to atmospheric corrosion, and are machinable. They are commonly used in structural components within the aerospace, automotive, and construction industries.

7. 7000 Series (Zinc)

Another category of aluminum alloy is the 7000 series. It is a heat-treatable alloy involving zinc with smaller amounts of copper, magnesium, and other elements. It has high strength, good toughness, and excellent fatigue resistance. The alloys are used in aircraft and aerospace applications, as well as in high-performance sporting goods. This type also strongly resists corrosion and can be welded, although care must be taken to avoid cracking.

What Type of Metal is Aluminum Alloy?

Aluminum alloy is a type of metallic substance that primarily consists of the metal aluminum and may also contain other elements like: copper, magnesium, manganese, silicon, or zinc. The specific composition and relative proportions of these elements determine the particular type of alloy. Aluminum alloys are used in a variety of applications and are particularly common in the construction, automotive, and aerospace industries. They are known for being strong, lightweight, and corrosion-resistant.

What Are the Properties of Aluminum Alloy?

Aluminum alloys have different physical and chemical properties depending on the alloying element and specific composition. Tables 1 and 2 below summarize some of the common properties:

What Are the Physical Properties of Aluminum Alloy?

Table 1 below lists the physical properties of certain aluminum alloys:

Table 1: Physical Properties of Aluminum Alloys
Aluminum Alloy TypeDensity (g/cm³)Thermal Conductivity (W/mK)Electrical Conductivity (%IACS)Coefficient of Thermal Expansion (10^-6/K)Specific Heat Capacity (J/kg K
Aluminum Alloy Type
1100
Density (g/cm³)
2.71
Thermal Conductivity (W/mK)
222
Electrical Conductivity (%IACS)
61.8
Coefficient of Thermal Expansion (10^-6/K)
23.6
Specific Heat Capacity (J/kg K
904
Aluminum Alloy Type
2024
Density (g/cm³)
2.78
Thermal Conductivity (W/mK)
121
Electrical Conductivity (%IACS)
49
Coefficient of Thermal Expansion (10^-6/K)
23.2
Specific Heat Capacity (J/kg K
875
Aluminum Alloy Type
3003
Density (g/cm³)
2.73
Thermal Conductivity (W/mK)
190
Electrical Conductivity (%IACS)
40
Coefficient of Thermal Expansion (10^-6/K)
23.1
Specific Heat Capacity (J/kg K
893
Aluminum Alloy Type
5052
Density (g/cm³)
2.68
Thermal Conductivity (W/mK)
105
Electrical Conductivity (%IACS)
35
Coefficient of Thermal Expansion (10^-6/K)
23.8
Specific Heat Capacity (J/kg K
880
Aluminum Alloy Type
6061
Density (g/cm³)
2.70
Thermal Conductivity (W/mK)
152
Electrical Conductivity (%IACS)
43
Coefficient of Thermal Expansion (10^-6/K)
23.2
Specific Heat Capacity (J/kg K
897
Aluminum Alloy Type
7075
Density (g/cm³)
2.81
Thermal Conductivity (W/mK)
130–150
Electrical Conductivity (%IACS)
37
Coefficient of Thermal Expansion (10^-6/K)
23.6
Specific Heat Capacity (J/kg K
714.8

Table Credit: https://www.matweb.com/

What Are the Chemical Properties of Aluminum Alloy?

Table 2 compares certain chemical properties of some aluminum alloys:

Table 2: Chemical Properties of Aluminum Alloys
Aluminum Alloy TypeCompositionCorrosion ResistanceWeldabilityMachinabilityAnodizing Response
Aluminum Alloy Type
1100
Composition
99.95% Al, 0.05–0.20% Cu, Iron: 0.95% max.
Corrosion Resistance
Good
Weldability
Good
Machinability
Good
Anodizing Response
Poor
Aluminum Alloy Type
2024
Composition
93.50% Al, 4.3–4.5% Cu, 0.5–0.6% Mn, 1.3–1.5% Mg
Corrosion Resistance
Poor
Weldability
Poor
Machinability
Good
Anodizing Response
Poor
Aluminum Alloy Type
3003
Composition
98.60% Al, 1.20% Mn, 0.12 Cu
Corrosion Resistance
Good
Weldability
Good
Machinability
Good
Anodizing Response
Poor
Aluminum Alloy Type
5052
Composition
97.25% Al, 2.50% Mg, 0.25% Cr
Corrosion Resistance
Good
Weldability
Good
Machinability
Poor
Anodizing Response
Good
Aluminum Alloy Type
6061
Composition
97.90% Al, 0.60% Si, 1.0% Mg, 0.2% Cr, 0.28% Cu
Corrosion Resistance
Good
Weldability
Good
Machinability
Good
Anodizing Response
Good
Aluminum Alloy Type
7075
Composition
90.00% Al, 5.60% Zn, 2.50% Mg, 1.60% Cu
Corrosion Resistance
Poor
Weldability
Poor
Machinability
Fair
Anodizing Response
Good

What Are the Applications of Aluminum Alloy?

The excellent characteristics of aluminum alloys, including their low density, high strength, resistance to corrosion, and good formability, make them useful across multiple industries. A few of the most popular uses for aluminum alloys are as follows:

1. Transportation

Aluminum alloys are valuable for their light weight and ability to resist corrosion. They are used in boats and ships as well as engine blocks, body panels, and structural components in the railway, automotive, and marine industries.

2. Electrical Applications

Aluminum alloys serve as conductors in power transmission lines, electrical wires, and electronic components. The low density is beneficial in power transmission lines since the cable's weight can be a limiting factor. Aluminum alloys are also utilized in electronic devices due to their excellent heat dissipation capabilities and thermal management characteristics. Generally speaking, aluminum alloys can make for affordable, durable, and capable electrical components. 

3. Consumer Goods

Aluminum alloys most often find their way into consumer goods because of their minimal weight and ability to resist corrosion. Automobile parts, cookware, electronics, and beverage cans are just a few of the products that are usually made of aluminum. Durability, strength, and recyclability are advantages of using an aluminum alloy in consumer goods.

4. Medical Equipment

Aluminum alloy is used in various medical equipment such as wheelchairs, hospital beds, and surgical instruments due to its low density, relative strength, and corrosion resistance. It is also utilized in medical implants like bone plates and screws because it is biocompatible. It’s very often important for a medical device to be both durable and immune to rust and other types of corrosion. 

5. Construction

Aluminum alloys’ inherent qualities make them useful components in windows, doors, roofing, siding, and framing. These alloys are ideal in abrasive outdoor environments because they are strong, lightweight, and resist corrosion. Aluminum alloys can also be easily formed into a variety of shapes and sizes, providing flexibility in design and construction.

What Are the Benefits of Aluminum Alloy?

Some benefits of aluminum alloys include:

  1. Low Density: Aluminum alloys are perfect for applications where weight reduction is crucial. Aluminum items are much lighter in weight than those made of other metals.
  2. High Strength-to-weight Ratio: Aluminum alloys are stronger than many other materials of comparable density.
  3. Corrosion Resistance: Aluminum alloys are perfect for use in harsh environments like marine or industrial applications because they have excellent corrosion resistance.
  4. Ductility: Most aluminum alloys are highly ductile, which allows for easy shaping without breaking or cracking.
  5. Thermal Conductivity: Alloys of aluminum make good thermal conductors anywhere that heat needs to be transferred efficiently. 

What Are the Limitations of Aluminum Alloy?

Some limitations of aluminum alloys include:

  1. Lower Melting Point: Aluminum alloys' melting point is lower than most other structural metals, making them potentially unsuitable for high-temperature applications.
  2. Lower Hardness: Aluminum’s relative softness means it can’t withstand as much wear as certain other materials. 
  3. Higher Cost: In some applications, aluminum alloys may not be as cost-effective as other materials.

Is Aluminum Alloy a Metal?

Yes, aluminum alloys are metals. Chemically speaking, aluminum itself belongs to the family of elements known as metals. When combined with other metals such as copper, magnesium, or zinc, it forms valuable metal alloys that are useful to many industries for their low densities, high strength, and resistance to corrosion. 

What Is the Difference Between Aluminum Alloy vs. Alloy?

While alloy is a general term for a combination of two or more metals or a metal and a nonmetal, aluminum alloy is a particular type of alloy that uses aluminum as its base metal. This means that while all aluminum alloys are alloys, not all alloys are aluminum alloys.

What Is the Difference Between Aluminum vs. Alloy?

Aluminum is a specific metal element on the periodic table, while alloy refers to a mixture of two or more metals or a metal and a nonmetal. Aluminum, at its most basic, is therefore a pure metal, whereas an alloy is a combination of various metals or elements.

Summary

This article presented aluminum alloys, explained what they are, and discussed their various applications and benefits. To learn more about aluminum alloys, contact a Xometry representative.

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Xomety X
Team Xometry
This article was written by various Xometry contributors. Xometry is a leading resource on manufacturing with CNC machining, sheet metal fabrication, 3D printing, injection molding, urethane casting, and more.