Choosing materials is a crucial decision when starting a project. Modern technologies rely on specialized materials, with aluminum being a key option. As the most abundant metal on Earth, aluminum is cost-effective and valuable in many industries. Its alloying capability results in various grades classified based on elements and properties.
Several types of aluminum are available for an extensive range of applications. These aluminum grades have varying properties, uses, and suitable machining processes. Therefore, understanding the right grade of aluminum for your project will help you get the best result.
This article provides an overview of the available aluminum types, their major differences, and various benefits. You will also learn the optimal alloys for specific applications. Discover the easiest method for selecting the best aluminum grade for part production by reading to the end.
A Brief Overview of Aluminum
Aluminum is Earth’s most abundant metal in the crust. Aluminum alloys result from a unique blend of various metal elements. They are appreciated for their low density, durability, resistance to corrosion, and outstanding strength-to-weight ratio. Aluminum is less dense than steel, making it a great alternative to steel in some applications.
The numerous aluminum alloys are easily shaped and machined because they are malleable and ductile. They possess good electrical and thermal conductivity, along with non-magnetic properties. Aluminum is one of the most recyclable materials having a low re-melting temperature. It requires only 5% of the energy for primary metal production.
Different Aluminum Grades Available
When added to aluminum, elements like Zinc, Magnesium, Iron, Copper, and Silicon provide enhanced workability, strength, electrical conductivity, and corrosion resistance. The Aluminum Association categorized standard aluminum grades based on the primary alloying element(s) and their response to thermal or mechanical treatments.
Aluminum alloys fall into two main classifications: wrought and cast aluminum. These classes have distinct identification numbering systems for differentiation. Let’s take a look at each of them.
Wrought Aluminum
Wrought aluminum possesses remarkable mechanical strength and it can take on various shapes. This aluminum grade is created by melting aluminum ingots with measured amounts of an alloying metal, determining the composition of the grade. After smelting, the alloy is cast into slabs or billets and undergoes mechanical processes such as extrusion, rolling, or forging. Heat treatment is then applied to enhance the natural properties of the aluminum alloy.
The wrought aluminum grade is identified with a four-digit code number:
- The first digit signifies the main alloying element that has been added to pure aluminum, influencing the grade’s properties.
- The second digit indicates modifications to the alloy. A zero signifies an original or unmodified alloy.
- The third and fourth digits on the codes are often arbitrary (given to specific alloys). For instance, the digits denote the alloy’s purity for the 1000 series.
Advantages of wrought aluminum grade include:
- Outstanding mechanical properties
- Excellent structural integrity
- Smooth and uniform surface finishes
- Excellent machinability and weldability
- Good formability, allowing transformation, shaping, machining, and extrusion into any desired shape.
Cast Aluminum
This aluminum grade is made from bauxite dissolved in caustic soda by crystallizing alumina. An electric current breaks down the alumina, separating aluminum from oxygen. The resulting aluminum is sent to a casting house for impurity removal and formation into pure aluminum billets.
After purifying and shaping into billets, the aluminum is melted and mixed with alloying elements. It is then poured into molds or shaped for further processing in varying percentages. Each cast aluminum grade is assigned a four-digit code, including a decimal value:
- The first digit signifies the primary alloying element of the series.
- The second and third digits are arbitrary numbers, except for the 1XX.X series. They indicate the purity of the pure aluminum alloy.
- The last digit designates if the aluminum alloy is a casting alloy (“.0”) or an ingot alloy (“.1” or “.2”).
Cast aluminum alloys exhibit lower tensile strength than wrought aluminum due to defects from the molding process. Therefore, they are susceptible to cracking and shrinkage. Despite this, cast aluminum is cost-effective and easily takes on the mold’s shape in its molten form.
Wrought and Cast Aluminum: What Is the Difference?
Cast and wrought aluminum alloys differ significantly in various ways. They include the following:
Metal Alloying Elements
Compared to cast alloys, wrought alloys have fewer additional metals. Wrought alloys generally have less than 4% of alloying elements, while cast alloys have more than 22%. This seemingly insignificant difference has a greater impact on these metals’ material characteristics.
The addition of more alloying agents decreases the flexibility of an aluminum alloy. Because of this, most cast alloys are susceptible to brittle fracture. On the other hand, by incorporating additional alloying elements, wrought aluminum alloys can retain their flexibility and other advantageous properties. At the same time, they have increased strength, conductivity, and corrosion resistance.
Fabrication Methods
The key distinction between these two grades is in the fabrication technique these alloys undergo to achieve the end product. Cast alloys typically emerge from their mold in the precise solid form desired.
In contrast, wrought alloys require various modifications while in their solid form. Consequently, the difference in their fabrication significantly influences the end products’ possible forms and physical characteristics.
Characteristics
Cast aluminum alloys have a lower melting point and tensile strength than wrought aluminum. The high silicon concentration allows for easier casting. Thus, the aluminum-silicon alloy is commonly used. Wrought aluminum is finding new applications, and manufacturers produce prototypes and parts using various methods.
Here’s a summary of the differences between the aluminum alloy types:
| Features | Wrought Aluminum | Cast Aluminum |
| Production method | Mechanical working (rolling, extrusion, forging) | Melting and pouring into a mold |
| Grain structure | Elongated grains due to mechanical working | Equiaxed grains due to solidification |
| Tensile strength | Higher tensile strength due to grain alignment | Lower tensile strength due to random grain orientation |
| Surface finish | Smooth and uniform surface finish | Rougher surface finish due to solidification |
| Weldability | Excellent weldability | Less weldable due to porosity and shrinkage |
| Applications | Aerospace components, structural components, automotive parts | Engine blocks, cylinder heads, housings |
| Examples | 6061, 7075 | A356, A380 |
Wrought Aluminum Series
Discussed below are the different wrought aluminum alloy series.
1000
This series is not heat-treatable and is made up of about 99% of aluminum without any major alloying elements. This series of grades has outstanding corrosion resistance, the maximum thermal and electrical conductivity, and is ductile with delayed work hardening. While the 1000 series is suited for harsh deformation operations, it has low tensile and yield strength.
Two notable alloys in the series are the 1000 and 1350 alloys. Aluminum 1100 is recognized for its good forming properties and application in heat exchange equipment and heat sinks. Aluminum 1350 has high electrical conductivity and is commonly used to produce transformers and switchgear. It offers good formability, rendering it an ideal choice for electronics manufacturing.
2000
Copper provides strength and hardness to the 2000 aluminum series, comprising 0.7 to 6.8% of copper and tiny amounts of manganese, magnesium, silicon, and other metals. While these high-performance alloys are appropriate for aerospace applications, the presence of copper lowers ductility and corrosion resistance.
The 2000 series aluminum grade is heat-treatable. Thus, the alloys in this series can undergo precipitation hardening to enhance strength. The formation of intermetallic elements during heat treatment further increases hardness, but it also makes welding challenging.
Aluminum 2011 exhibits excellent machinability for high-speed lathing. Despite being highly versatile, it lacks corrosion resistance, but this can be addressed through anodizing or coating. Conversely, Aluminum 2024 is a well-known high-strength alloy in the series. It is suitable for heavy-duty applications but has relatively poor corrosion resistance
3000
This aluminum series contains 0.05 to 1.5% of manganese as the primary alloying element. The alloys exhibit higher mechanical strength than the pure aluminum. This strength is maintained over a wide temperature range, and the grades offer good corrosion resistance, formability, ductility, and suitability for welding. They can be hardened through cold working because they are not heat-treatable.
Aluminum 3003 is a widely used grade in the 3000 series. It offers good mechanical properties with high tensile strength. Meanwhile, aluminum 3005 offers good elongation, processing performance, and corrosion resistance. It helps manufacture strips and coils for various applications.
4000
The 4000 series use silicon as the primary alloying element. They comprise 3.6 to 13.5% of silicon and trace amounts of magnesium and copper. Silicon lowers the alloy’s melting point, enhancing fluidity in the molten state. Thus, these grades are excellent filler materials for welding and brazing.
Certain grades in this series are heat-treatable. However, this depends on the proportions of magnesium and copper in such alloys. The addition of these elements provides a better response to heat treatment. This allows for applications in welding when combined with heat-treatable aluminum grades.
5000
The 5000 series features 0.5 to 5.5% of magnesium. These grades are non-heat-treatable but can be hardened through cold working. They exhibit high ductility when annealed, and moderate-to-high strength, including good corrosion and alkaline resistance.
Within the 5000 series, grades with 3.5% of magnesium are recognized as marine grades due to their corrosion resistance in saltwater environments. However, they are unsuitable for high-temperature applications as they are susceptible to stress corrosion.
Aluminum 5052 boasts the highest strength in this series. It offers better resistance to marine conditions and exhibits excellent finishing qualities when machined. Its incredible workability also allows it to be formed into several intricate shapes and sizes.
6000
This series comes with 0.2 to 1.8% of silicon and 0.35 to 1.5% of magnesium. The alloys can undergo solution heat treatment to increase yield strength. Precipitation hardening is possible due to the production of magnesium-silicide during the aging process. However, reduced flexibility due to high silicon can be corrected by adding manganese and chromium during heat treatment. These grades are difficult to weld due to sensitivity to cracking.
Aluminum 6061 is one of the most versatile heat-treatable alloys in the series. It boasts excellent formability, weldability, and corrosion resistance. Manufacturers use this grade to produce various structural shapes like beams, angles, channels, and more. On the other hand, Aluminum 6063 is known for high tensile strength, superior finishing qualities, and good corrosion resistance. It is employed in aluminum extrusion and architectural applications such as window and door frames, railings, etc.
7000
The 7000 aluminum series has 0.8 to 8.2% of zinc as the main alloying element. The series boasts some of the aluminum alloys with the highest strengths. The alloys here are heat-treatable with a solution heat treatment. Aging further increases their yield strength. Addition of copper even further enhances their already good corrosion resistance.
Aluminum 7075 is recognized for its high performance. It ranks among the strongest aluminum grades. With superior hardness and tensile strength compared to Aluminum 6061, it can endure prolonged periods of stress. This aluminum type is commonly known in aerospace applications.
Cast Aluminum Series
The series of cast aluminum alloys includes the following:
1xx.x
These cast alloys are unalloyed and commercially pure aluminum with excellent corrosion resistance, finishing properties, and welding attributes. 1xx.x alloys are commonly used in the production of rotors or for cladding corrosion-prone alloys.
2xx.x
These alloys are predominantly composed of copper, with chromium, magnesium, and manganese also present. They are heat-treatable, which means they can obtain additional strength through heat-treatment. They have the greatest strength and hardness of any casting alloy, particularly at higher temperatures. Because of the copper content of its composition, it is prone to corrosion and becomes less ductile and prone to cracking when heated. 2xx.x alloys are commonly used in car exhaust system components, cylinder heads, and aircraft engine parts.
3xx.x
The principal alloying components of 3xx.x cast alloys are silicon, copper, and magnesium, with additional nickel and beryllium. They are heat-treatable and have a high strength. As a result, these alloys are resistant to cracking and wear and are easy to machine. 3xx.x alloys are commonly used in car wheels, automotive cylinder blocks/heads, compressor/pump components, aircraft fittings, etc.
4xx.x
Silicon is the only alloying element used in 4xx.x cast alloys. These alloys are non-heat treatable and offer excellent casting properties, strength, wear resistance, and corrosion resistance. Cookware, pump casings, and bridge railing support casings are common uses for 4xx.x aluminum alloys.
5xx.x
These cast alloys are not heat-treatable and use magnesium as the main alloying element. They have excellent corrosion resistance, good machinability, and an appealing surface finish when anodized. Sand-casted components are typical applications for 5xx.x alloys.
7xx.x
Zinc is the primary alloying ingredient of 7xx.x cast alloys, which are heat-treatable. They often do not cast well but have excellent dimensional stability, good machinability, fine finishing characteristics, and corrosion resistance.
8xx.x
These alloys are not heat-treatable and are mostly composed of tin with trace amounts of copper and nickel. These alloys are low in strength but have excellent machinability and wear resistance. They were created for bearing applications like bi-metal sliding bearings for combustion engines.
Common Aluminum Alloys Used in Custom Manufacturing
Here, you will learn the different types of aluminum alloys applicable for manufacturing products for various industries.
Aluminum 6061
6061 aluminum alloy contains magnesium and silicone as its main elements. Belonging to the 6000 series, the last two digits (61) reveal its composition (97.9% aluminum, 1.0% magnesium, 0.6% silicon, 0.28% copper, and 0.2% chromium). It is highly versatile due to its strength, weldability, heat treatability, and corrosion resistance.
With a yield tensile strength of 40 ksi and an ultimate tensile strength of 45 ksi, 6061 aluminum is suitable for structural applications and is corrosion-resistant. Suited for extrusion, applying the T6 temper enhances its strength and durability, while anodizing improves its aesthetic finish.
Pros
- High strength
- Highly machinable
- Excellent corrosion resistance
- Accepts surface finishes very easily
- High weldability
Cons
- Lower fatigue strength
- High temperatures reduce its strength
- Susceptibility to brittle fracturing or cracking when bent
- Experience is required for welding
Common Applications
- High-strength automotive components
- Automotive or locomotive frames
- Pressure vessels
- Hydraulics
- Heat exchangers
- Precision robotics
- Electronics industry components like connectors and fittings
- Consumer products like cabinet hardware
- Marine industry fittings and bodies
- Bicycle frames
- Aerospace fittings
- Valve parts
Aluminum 7075
The principal alloying constituents of the 7075 alloy are copper and zinc. 7075 aluminum is part of the 7xxx series, which indicates zinc as the principal alloying element and high tensile strength. It comprises 90% aluminum, 5.6% zinc, 2.5% manganese, 1.6% copper, and 0.23% manganese.
It is among the strongest and lightest aluminum alloys, with a density of 2.81g/cm3 and an ultimate tensile strength of 83 ksi. It is used in applications requiring extreme strength because it is strong, somewhat weldable, and stress-resistant.
Pros
- Very high shear and tensile strength
- Good fatigue strength
- High formability
- Accepts finishes easily
Cons
- Relatively low corrosion resistance
- Fair machinability
- High cost
Common Applications
- Aerospace frames and structural parts
- Aircraft wing panels
- Structural beams
- Bicycle frames
- Marine and automotive parts
- Tooling
- Gears
- Rock climbing equipment
Aluminum 6063
The 6063 aluminum alloy, which has moderate strength and good ductility, is commonly known as architectural aluminum. It is composed of silicon and magnesium. It works really well with die forming.
Additionally, aluminum 6063 is composed of magnesium and silicon, so it has great corrosion resistance. This type of aluminum can also be etched using a laser. This alloy can also be used for die forming because of its excellent ductility and mild strength.
Pros
- Good welding and brazing properties
- Heat treatable
- Excellent corrosion resistance
- Smooth and lustrous appearance
- Good for parts with complex geometries
Cons
- Relatively lower strength
- Not very machinable
Common Applications
- Heat Exchangers
- Piping
- Electrical conduits
- Decorative products
- Commercial components like window frames
- Railing
Aluminum 5052
A dependable alloy with good corrosion resistance and moderate strength is 5052 aluminum. Because the alloy has no copper, it is ideal for applications in seawater. The most prevalent part made of 5052 aluminum is marine equipment. Nevertheless, heat treatment is not an option as the 5052 comes from the 5000 aluminum alloy grade.
Pros
- Excellent corrosion resistance
- High fatigue strength
- Highly machinable, workable, and weldable
Cons
- Lower shear and tensile strength
- Can only be hardened through cold working
Common Applications
- Fuel and oil lines for automotive and aerospace applications
- Wiring
- Lighting
- Consumer electronics like televisions and computers
- Motor mounts
- Flooring panels
- Boating panels and parts
- Marine industry components
- Electrical enclosures/boxes
Aluminum 2024
2024 aluminum is a cheap, versatile alloy that is less strong than some of the other alloys on this list. It is simple to complete and offers a reasonable degree of machinability and workability. Copper and magnesium are the primary alloying elements that give it greater strength and hardness.
2024 aluminum is easily heat treated and has a high strength to weight ratio. However, the increased copper content of 2024 aluminum also lessens its resistance to corrosion. Because 2024 aluminum has a reduced resistance to corrosion, it is frequently found as clad sheets.
Pros
- Machinable and formable
- High strength alloy
- Heat treatable
- High fatigue resistance
Cons
- Low corrosion resistance
- Can only be welded through friction welding
Common Applications
- Aircraft structural components
- Engine components like cylinders and pistons
- Aerospace paneling
- Fasteners
- Automotive wheels
- Gears
- High-pressure cylinders
- Automotive engine parts
- Robotics
To help summarize these alloys, here is an aluminum grades chart for comparison:
| Feature | 6061 Aluminum | 7075 Aluminum | 6063 Aluminum | 5052 Aluminum | 2024 Aluminum |
| Composition | 97.9% Al, 1.0% Mg, 0.6% Si, 0.28% Cu, 0.2% Cr | 90% Al, 5.6% Zn, 2.5% Mn, 1.6% Cu, 0.23% Mn | 98.5% Al, 0.4% Si, 0.7% Mg, 0.2% Mn | 99.5% Al, 2.5% Mg, 0.2% Cr | 93% Al, 3.8% Cu, 1.5% Mg, 0.6% Mn |
| Strength | High | Very high | Moderate | Moderate | High |
| Machinability | Highly machinable | Fair machinability | Not very machinable | Highly machinable | Machinable and formable |
| Formability | Excellent | Good | Good | Good | Good |
| Weldability | Excellent | Somewhat weldable | Good welding and brazing properties | Highly weldable | Can only be welded through friction welding |
| Heat Treatability | Yes | Yes | Yes | No | Yes |
| Corrosion Resistance | Excellent | Relatively low | Excellent | Excellent | Low |
| Applications | Structural components, aerospace components, automotive parts | Aerospace frames and structural parts, aircraft wing panels | Heat exchangers, piping, electrical conduits | Fuel and oil lines for automotive and aerospace applications, wiring, lighting | Aircraft structural components, engine components like cylinders and pistons |
Considerations for Selecting an Aluminum Grade
Selecting the appropriate types of aluminum alloy for your project is crucial to achieving optimal outcomes. The following are essential things to consider while choosing an aluminum alloy.
Material Availability and Cost
The aluminum alloy’s availability is crucial. A rare grade of aluminum will cause production to slow. For instance, 7075 aluminum is much more expensive yet has good machinability. However, 6061 aluminum is substantially less expensive and has a lower tensile strength and hardness, which makes it simpler to machine.
Similarly, the cost of the aluminum alloy grade must be taken into account when selecting a material for your project. Strive to strike a balance between the material that has the best qualities for your project at a price and your budget. It assists in creating a productive framework for your manufacturing procedure.
Desirable Properties
You must also consider the characteristics of the material you want to choose. These features include the following:
- Corrosion Resistance: A manufactured part’s intended usage dictates whether or not corrosion resistance is required. For instance, components intended for chemical or marine applications must be exceptionally corrosion-resistant.
- Machinability: An aluminum alloy’s machinability rating indicates whether or not it is compatible with aluminum CNC machining procedures. Knowing the appropriate alloys with high to moderate machinability ratings would be beneficial. Examples include 6061-T6 and 7075 aluminum. As such, these materials can be used to make a wide range of parts with complex geometries.
- Weldability: When manufacturing a part that must be welded to other parts, the alloy’s weldability is a crucial consideration. For instance, if weldability is a top priority, the 3000 series is an excellent option.
- Strength: The amount of stress an alloy can withstand before deforming is determined by its strength. Therefore, high-strength aluminum alloys are required for parts that are inherently exposed to severe stress.
Heat Treatment
Aluminum alloys are subjected to high heat temperatures during the heat treatment process to improve their durability and strength. Therefore, you should ascertain which series of aluminum can be heat treated and which cannot. Heat treatment is compatible with the aluminum 2000, 6000, and 7000 alloy series. These alloys can be heat-treated to increase the strength of the final products.
End-Use Applications
When choosing aluminum alloys, it’s crucial to consider the intended final applications. Different alloys possess varying properties, such as strength, corrosion resistance, and formability. For example, if you’re designing components for aerospace structures, you might prioritize alloys known for their lightweight yet strong characteristics.
On the other hand, if you’re working on heat exchangers or automotive parts, you might focus on alloys with excellent thermal conductivity and durability. Understanding the end-use applications helps ensure that the chosen aluminum alloy meets the specific requirements and performance criteria for the intended purpose.
Conclusion
Depending on the element composition, aluminum is a metallic material that is frequently used and has a variety of qualities. Due to their diverse qualities, multiple types of aluminum alloys are suitable for a range of applications. Thus, to select the best material for your projects, you must thoroughly understand the differences between various aluminum alloys.
Nevertheless, selecting an aluminum metal for your prototype design may seem challenging, given the abundance of options. At Zintilon, we provide qualified guidance on the ideal materials for various manufacturing tasks. Contact us now for assistance in resolving your material selection challenge.
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