Importance of Aluminum Density

Aluminum is one of the most popular industrial materials because of its many flexible and desirable traits. One of those characteristics is its density. Aluminum is a lightweight material – in fact, its density is one-third of the density of steel. Aluminum has a high strength-to-weight ratio, meaning that it delivers significant strength despite its lightweight nature. These characteristics translate into a material that is easy to work with, yet durable and able to withstand a variety of industrial applications.

In fact, aluminum is a favorite of many industries – from aerospace and automotive down to sporting equipment – because it is so light and flexible. Its density is markedly lower than other metals. If you’re curious, you can also read more about which lightweight aluminum alloys appear in the aerospace and automotive industries.

What is the Density of Pure Aluminum?

The density of pure aluminum in solid form is 2,699 kg/m3 (theoretical density based on lattice spacing) and 2,697-2,699 kg/m3 (polycrystalline material). The liquid density of pure aluminum is 2,357 kg/m3 at 973K and 2,304 kg/m3at 1173K.

How is Density Calculated?

The density of an object is the object’s mass divided by its volume. For the purposes of the aluminum industry, density is a computation based on pure aluminum’s density plus its composition with other alloying elements. The Aluminum Association’s computed densities can be referenced to help users calculate measurements such as weight per unit length, weight per unit area, and covering area.

How Density Varies by Type of Aluminum

While the density of pure aluminum is generally considered to be about 2.7 g/cm³, the application of alloys can cause that number to vary slightly. Heavier alloying elements will increase the product’s weight. Alloys in the 1xxx series, for example, produce densities that are closer to that of pure aluminum; in fact, alloys in this series are considered 99% pure commercial aluminum.

Alloys in the 7xxx series and 8xxx series, on the other hand, can produce densities of up to around 2.9 kg/m3. 7075 aluminum in particular, at 2.81 g/cm³, has a higher density than other alloys. Consequently, 7075 aluminum offers one of the highest strengths of aluminum available (its ultimate tensile strength is nearly double that of the popular 6061 aluminum).

Interestingly, alloys in the 4xxx series (whose primary alloying constituent is silicon) can produce densities that dip below pure aluminum’s specific gravity of 2.7 g/cm³. In certain quantities, silicon causes aluminum’s specific gravity to decrease.

How Does Aluminum Compare in Density with Other Metals?

Low density is one of the main advantages of aluminum over other structural metals. Aluminum has a density that measures at about one-third the density of steel or copper. As one of the lightest commercially available metals, aluminum offers a high strength-to weight ratio that makes it desirable for many structural applications and products. In addition, it is less expensive to fabricate than steel and offers greater malleability, ductility, and corrosion resistance.

Here is a sampling of how the density of aluminum compares with other metals:

What are the Benefits of Aluminum’s Density?

Aluminum’s low density means that it is lightweight and easy to move around. Even though it’s lightweight, the material is very strong and easy to form and extrude into shapes. Aluminum’s density is a significant advantage in products where lightness is considered a very important characteristic. These include transportation components (especially aerospace and automotive), machines, and appliances. Other fields of use that benefit from aluminum’s low density are building materials, packaging, electrical components, household items, and food/chemicals.

Aluminum’s low density is highly attractive to automakers, for example, for its ability to compare well with steel’s density when forming automotive parts and structures. Aluminum’s low density reduces vehicle weights which:

• Improves performance and vehicle handling
• Improves safety, crash resistance, and the ability to withstand accidents
• Allows increased payloads and fuel savings

From the standpoint of weight and cost basis, aluminum is a stronger heat conductor than copper. Its high thermal conductivity makes aluminum appropriate for heat-based products such as radiators and cooking utensils.

It’s easy to see why aluminum’s low density is considered a positive characteristic. Its lightweight nature makes it easily formed into different shapes and easier to move and handle in the manufacturing process. Yet, aluminum’s low density – marked by a high strength-to-weight ratio – makes it a great choice of material where lightness, yet toughness, is paramount.