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Ductility of Aluminum: Everything You Need to Know

The ductility of a material refers to its ability to undergo a large amount of inelastic deformation until it breaks. It is usually considered a soft property of any material. However, in reality, ductile materials such as aluminum have an important role to play in every structural application. Aluminum, which is one of the most commonly used materials in high-rise structures and skyscrapers, has good ductility. However, its ductility does vary depending on the heat treatment it received and any alloying materials that were added to it.

Below, we first detail the importance of ductility in structural applications and then explore the advantages and disadvantages of aluminum ductility.

The Importance of Ductility in Structural Applications

Deformability and ductility are two major properties of a material that define its lateral strength. A material with good ductility can undergo a large elongation before it collapses.

To better understand ductility, let’s look at a stress-strain graph of material, shown below:

Stress-strain graph of material

Here, the yield strength represents the point up to which the material can bear a certain load before it starts to deform. Up to this point, the material can reverse back to its original shape once the load is removed, just like rubber.

If we increase the load beyond the yield point, the material will show plastic deformation. That means the material will have permanent deformity, but it will not break until the load reaches the ultimate strength point in the curve. Beyond that point, the material will rupture before breaking down completely.

The phase between the yield strength and the ultimate strength represents the ductility of the material. The ductility of a material is measured in terms of ductility ratio or ductility factor, as shown below.

Ductility Factor Formula

Ideally, the value should be between four to five.

In the case of a highly ductile material, these two points are very far from each other, and thus, the material can undergo large plastic deformation before collapse. However, in the case of a brittle material, it is the opposite.

Stress Strain Comparison ChartDifferent metals have different ductility. Materials like gold and silver can be drawn into thin wires, as they are highly ductile. On the other hand, tungsten carbide and cast iron are highly brittle. Now, let’s discuss aluminum ductility.

Advantages of Aluminum Ductility

Pure aluminum is ductile in nature. However, aluminum comes in different grades. The addition of extra elements and the type of heat treatment affect its ductility.

The following table lists the ductility of some commonly used aluminum alloys compared to some commonly used steel alloys.

Alloy Heat Treatment  Elongation at Break (at 77°F)
Aluminum 3003 O (Annealed) 40%
H14 (Strain Hardened) 16%
Aluminum 5052 O 30%
H32 18%
Aluminum 6061 O 30%
T6 17%
AISI 4140 Steel Oil Quenched 15%
AISI 4340 Steel Normalized 12%
AISI 6150 Steel Oil Quenched 14%

Clearly, all forms of aluminum have better ductility than steel. With subsequent heat treatments, aluminum achieves higher strength but at the cost of ductility. Nevertheless, aluminum ductility offers an essential advantage in structural applications.

In the event of any unexpected overload, a brittle structure (made up of only steel) will suddenly collapse, whereas a ductile structure (steel + aluminum) undergoes a controlled collapse. The addition of ductility to the iron structure through beams or suspension cables increases its maximum potential as a whole; thus, at the time of an earthquake, it doesn’t collapse suddenly but yields in a controlled manner. This can be life-saving, as it gives people in life-threatening situations sufficient time to escape. This is the reason ductile materials like aluminum are used as the major structural element in earthquake-prone areas.

Science Fact: Aluminum’s ductility is so remarkable that it can be stretched into thin wires or beaten into thin sheets, a property that makes it ideal for manufacturing products like aluminum foil. 

Disadvantages of Aluminum Ductility

As aluminum is a relatively soft material with a low melting point, it can be somewhat challenging to machine. Depending on its alloying elements, aluminum can melt due to heat produced by the friction between the tool and the workpiece. As a result, gummy chips can begin to build up around the blade and offer resistance to the tool with each pass. When enough materials build up, the blade can grab onto the aluminum, potentially causing injuries to the machinist. Cutting blades can also quickly wear out due to the soft yet abrasive nature of aluminum, and the costs associated with having to purchase new tools can be significant.

It’s important to select the right cutting tool for the job and follow best practices to produce faster cuts with minimum material losses. Without industrial-grade sawing equipment and the right blades (non-ferrous/carbide-tipped wood), it is impossible to achieve a clean cut with ductile materials like aluminum.

Partnering with an experienced metal supplier will help you get your desired aluminum cut-to-precision without having to spend money on new tools or struggle with new techniques.

Impact of Alloying and Heat Treatment on Aluminum’s Ductility

Starting with pure aluminum, known for its high ductility, the addition of other metals to create an aluminum alloy can dramatically change its properties. While pure aluminum is soft and highly ductile, the introduction of elements like copper, magnesium, or zinc transforms it into a much stronger material. This is particularly important when considering the tensile strength and thermal conductivity of aluminum products. The balance between strength and ductility is crucial for applications where flexibility and durability are essential.

Heat treatment plays a pivotal role in this transformation. It alters the mechanical properties of the aluminum alloy, impacting not only its strength but also its ductility. The process involves heating the alloy to a specific temperature and then cooling it at a controlled rate. This treatment can significantly improve the thermal conductivity of the alloy, making it more suitable for applications where heat dissipation is crucial.

Moreover, certain aluminum alloys are designed to be corrosion-resistant, an essential attribute for products exposed to harsh environments. The corrosion-resistant nature of these alloys extends the life and maintains the integrity of aluminum products in various applications.

The crafting of aluminum alloys and the application of heat treatment are key to optimizing the mechanical properties of aluminum. This manipulation enhances the material’s utility, expanding its applications across different industries. The balance between maintaining the innate ductility of pure aluminum while enhancing other properties like tensile strength, thermal conductivity, and corrosion resistance is a testament to the versatility and adaptability of aluminum as a material.

Purchase High-Quality Aluminum From an Experienced Supplier

For more than two decades, Industrial Metal Service has been supplying new and recycled aluminum and aluminum alloys to the San Francisco Bay Area and beyond. Our wide inventory includes 6061 aluminum plate stock, bar stock, and round stock, as well as 5080 aluminum tooling plate and MIC-6 aluminum plate. We also supply other metals such as copper, titanium, and specialty metals such as Hastelloy and Invar 36.

Take advantage of our state-of-the-art metal sawing services for precision-cut aluminum, each and every time. With a surface finish as low as 12 microinches, our MetlSaw NF12-T12 can handle up to 12-inch thick aluminum plates and can cut them up to 12 feet long.

Published by IMS Team

Industrial Metal Service has decades of experience and over 1.1 billion pounds of metal sold and recycled. Our founder, Jeff, has spent his life in the industry and prides himself on offering fair, efficient, trustworthy, knowledgeable, outstanding customer service. We offer metal salesmetal recycling pickup service, and other associated services, such as precise metal sawing, machinery teardown, and warehouse cleanupGive us a call and we’ll get it done.