Aluminium 2618 vs. 2024: What’s the Difference?
When it comes to selecting the right aluminum alloy for your project, the choice can significantly impact performance, durability, and…
When it comes to selecting the right aluminum alloy for high-performance applications, the choice often narrows down to two heavyweights: 2618 and 7075. Known for their exceptional strength-to-weight ratios, these alloys are staples in industries like aerospace, defense, and manufacturing. But while both boast impressive properties, their unique compositions and performance characteristics make them suited for very different roles. Are you looking for superior temperature resistance? Or is ultimate tensile strength your top priority? Understanding the differences between these two alloys is key to making an informed decision.
In this comparison, we’ll dive deep into the mechanical properties, chemical compositions, and real-world applications of 2618 and 7075 aluminum. From weldability and workability to corrosion resistance and hardness, we’ll explore how each alloy performs under varying conditions and why these differences matter. Whether you’re designing aircraft components, structural parts, or high-stress machinery, this guide will help you determine which alloy is the perfect fit for your specific needs. Let’s break it down.
Aluminum alloys play an essential role in modern engineering and manufacturing, thanks to their unique blend of lightweight, strength, and corrosion resistance. Their lightweight yet strong nature makes them crucial in industries such as aerospace, automotive, and defense, where efficiency and safety heavily depend on material performance.
The aerospace industry relies on aluminum alloys for their unmatched strength-to-weight ratio, which is critical for reducing fuel consumption and increasing payload capacity. Similarly, the automotive sector uses these materials to boost vehicle performance and improve fuel efficiency. In the defense industry, aluminum alloys are prized for their durability and ability to withstand extreme conditions, ensuring the reliability of military equipment even in the harshest environments.
This article compares two popular aluminum alloys, 2618 and 7075. It focuses on their mechanical properties, chemical composition, and applications to help engineers and manufacturers make better material choices. By understanding the differences and similarities between these alloys, decision-makers can select the most suitable material for their specific needs, balancing performance and cost-effectiveness.
Tensile and yield strength are crucial for determining how well an alloy can withstand forces without breaking or deforming. These properties help engineers choose the right materials for various applications, ensuring safety and performance.
For 2618 aluminum, the maximum stress it can endure before breaking, known as ultimate tensile strength, is about 420 MPa (61,000 psi), while its yield strength—indicating the stress level at which it begins to deform permanently—is around 350 MPa (51,000 psi). In contrast, 7075-T6 aluminum boasts a higher ultimate tensile strength of 510 to 540 MPa (74,000 to 78,000 psi) and a yield strength between 430 and 480 MPa (63,000 to 69,000 psi). This makes 7075-T6 a more suitable choice for highly stressed structural components.
The Brinell hardness of an alloy reflects its resistance to surface wear and deformation. Imagine how a wooden table resists scratches compared to a metal one; this is similar to how 2618 aluminum, with a hardness of about 120 HB, compares to 7075-T6 aluminum, which ranges from 150 to 200 HB. The higher hardness of 7075-T6 makes it ideal for applications requiring superior surface durability.
Fatigue strength is the alloy’s ability to handle repeated stress over time without cracking, much like how a paperclip can only be bent back and forth a limited number of times before breaking. 2618 aluminum can handle stress cycles up to 110 MPa, whereas 7075-T6 aluminum can withstand up to 160 MPa, making it more reliable for dynamic applications like aircraft structures.
The elastic modulus measures stiffness, akin to how much a rubber band stretches when pulled. Both alloys are relatively stiff, with 2618 aluminum at 71 GPa and 7075-T6 slightly stiffer at 71.7 GPa. This stiffness contributes to their performance in high-stress situations.
Elongation at break indicates ductility, or how much an alloy can stretch before fracturing. 2618 aluminum stretches about 5.8% before breaking, reflecting moderate ductility. In comparison, 7075-T6 aluminum varies from 5% to 11%, offering a balance between strength and flexibility, depending on specific requirements.
Shear strength refers to the alloy’s ability to resist forces that try to cut or slide its layers apart. Think of it like cutting through cheese versus cutting through a carrot. 2618 aluminum has a shear strength of about 260 MPa, while 7075-T6 is stronger at 330 MPa. The shear modulus, indicating stiffness under shear forces, is around 27 GPa for 2618 and slightly less for 7075-T6 at 26 GPa.
Poisson’s ratio describes how an alloy expands in directions perpendicular to compression, similar to how a sponge expands sideways when squeezed. Both 2618 and 7075-T6 aluminum have similar behavior, with ratios of 0.33 and 0.32, respectively.
In summary, 2618 aluminum offers moderate strength, ductility, and stability across temperatures, making it suitable for applications where these properties are prioritized. On the other hand, 7075-T6 aluminum provides superior strength and wear resistance, ideal for high-stress, dynamic environments such as aerospace and sports equipment. Choosing between these alloys depends on the specific demands of the application, balancing strength, durability, and environmental factors.
The chemical makeup of aluminum alloys like 2618 and 7075 plays a crucial role in determining their performance and applications. The elements and their amounts determine the strength, corrosion resistance, and overall performance of these alloys.
The aluminum content in these alloys is key to their lightweight nature and resistance to corrosion, with 2618 containing 92.4% to 94.9% aluminum and 7075 slightly less, at 86.9% to 91.4%.
2618 aluminum includes:
7075 aluminum owes its high strength to:
With its high zinc content, 7075 aluminum is exceptionally strong, making it perfect for demanding, high-stress applications.
Magnesium improves corrosion resistance in both alloys, though performance depends on the environment and protective coatings.
2618’s composition allows for easier machining and better weldability compared to 7075, which can be more challenging due to its higher strength and hardness.
Ultimately, the choice between 2618 and 7075 depends on the specific balance of strength, temperature resistance, and machinability required for the application.
Renowned for their unique strengths, 2618 and 7075 aluminum alloys serve crucial roles in various high-demand industries. Their distinct properties make them indispensable in fields ranging from aerospace to sports equipment, where performance and reliability are paramount. Let’s explore the specific applications of these two remarkable materials.
In the aerospace industry, 2618 aluminum is a trusted material for components that must endure extreme temperatures and heavy mechanical stress. Its ability to withstand high heat and maintain its structural integrity makes it ideal for manufacturing parts like engine pistons, turbine blades, and other critical elements. For example, in jet engines, where temperatures can soar to thousands of degrees, 2618 aluminum ensures these components remain durable and reliable under intense operating conditions.
In the fast-paced world of automotive engineering, 2618 aluminum shines in the design of high-performance engine components. Whether it’s the pistons powering a race car or the connecting rods in a high-pressure engine, this alloy’s resistance to heat and wear ensures peak performance under the most demanding conditions. Motorsport teams, in particular, rely on 2618 aluminum for its ability to handle the rigors of competition, where every fraction of a second matters.
When it comes to defense applications, 2618 aluminum is a material of choice for aircraft and armored vehicle components. Its exceptional strength and ability to perform in harsh environments make it indispensable for military-grade equipment. From high-temperature engine parts to structural reinforcements, 2618 aluminum delivers the reliability needed in critical missions.
In aerospace engineering, 7075 aluminum stands out for its unmatched strength-to-weight ratio. This makes it a go-to material for structural components like fuselage frames, wings, and landing gear. Its superior fatigue resistance ensures that aircraft can withstand dynamic loads and stress over time, making 7075 aluminum essential for both commercial and military aviation. Even smaller components, such as fasteners and fittings, benefit from this alloy’s strength and lightweight nature.
7075 aluminum plays a pivotal role in the automotive and transportation industries, particularly in performance-focused designs. It’s commonly used in chassis parts, suspension systems, and lightweight wheels, where strength and reduced weight are key to improving fuel efficiency and handling. Cyclists and motorcyclists also value 7075 aluminum for its use in lightweight yet durable frames that can endure rugged terrains and high-impact forces.
Athletes and adventurers alike rely on 7075 aluminum for its unbeatable strength in sports and recreational gear. From golf club heads that deliver powerful swings to climbing equipment that ensures safety in the most challenging conditions, this alloy offers unmatched reliability. Ski poles, bicycle frames, and other high-performance gear benefit from the alloy’s combination of strength, lightweight properties, and long-lasting durability.
In military applications, 7075 aluminum is a cornerstone of modern equipment design. Firearms, such as rifle receivers, are often crafted from this alloy due to its high impact resistance and rigidity. Additionally, combat aircraft and armored vehicles incorporate 7075 aluminum for structural components that demand both strength and reduced weight, ensuring optimal performance in the field.
While both 2618 and 7075 aluminum alloys offer exceptional performance, their unique strengths cater to different needs. 2618 aluminum thrives in heat-intensive environments, making it ideal for aerospace engines and high-performance automotive components. On the other hand, 7075 aluminum excels in high-stress, lightweight applications, such as structural aerospace parts, sports gear, and military equipment.
The choice between 2618 and 7075 aluminum ultimately depends on the demands of the application. Each alloy brings its own set of advantages, whether it’s 2618’s resilience in extreme heat or 7075’s unparalleled strength-to-weight ratio. By selecting the right material for the job, engineers and designers can push the boundaries of innovation, delivering solutions that perform flawlessly in even the most challenging environments.
Workability is how easily a material can be machined or formed into a specific shape, making it crucial in manufacturing processes that require precision.
2618 aluminum is moderately workable, largely due to its softer nature compared to 7075 aluminum, which allows for easier machining and shaping. However, precautions are necessary to reduce tool wear and ensure accuracy. When machining 2618 aluminum, standard cutting tools can be used effectively, although carbide tools are recommended for longer tool life. Maintaining moderate cutting speeds and feed rates optimizes the surface finish and minimizes wear. The use of coolants is also beneficial in dissipating heat and preventing surface defects.
7075 aluminum is harder and more challenging to machine due to its high strength. This characteristic increases tool wear and requires specialized techniques. High-performance tools, such as carbide or diamond-coated options, are essential to maintain cutting efficiency. By using reduced cutting speeds and increased feed rates, overheating can be prevented, ensuring effective chip removal and maintaining quality.
2618 aluminum offers moderate weldability, though it is not as easily welded as some lower-strength alloys. Preheating reduces stress and cracking risks, making gas tungsten arc welding (GTAW/TIG) or gas metal arc welding (GMAW/MIG) more effective. Post-weld heat treatments, like solution heat treatment followed by aging, are necessary to restore the material’s mechanical properties and enhance joint strength.
7075 aluminum is traditionally considered difficult to weld using conventional methods due to its high zinc content, which can lead to cracking. Innovative techniques have made welding 7075 more feasible. Adding titanium carbide nanoparticles refines the weld’s structure and reduces cracking. Additionally, friction stir welding (FSW), a solid-state process, significantly minimizes defects and improves joint strength. Post-weld treatments, such as solutionizing and aging, are crucial for restoring the material’s strength.
For workability, 2618 aluminum is easier to machine and shape, while 7075 is better suited for simpler designs due to its hardness. Regarding weldability, 2618 can be welded with standard methods, whereas 7075 requires advanced techniques to achieve satisfactory results.
Understanding how aluminum alloys resist corrosion is essential when selecting materials for environments exposed to moisture or chemicals. The corrosion resistance of 2618 and 7075 aluminum alloys depends on their chemical composition and microstructure.
7075 aluminum is well-known for its high strength but has only moderate resistance to corrosion. Containing zinc, magnesium, and copper, this alloy is strong but more prone to corrosion due to its composition. In humid environments or when in contact with other metals, 7075 aluminum is vulnerable to galvanic corrosion. Anodizing or applying protective coatings can help reduce the risk of corrosion in 7075 aluminum. Overaged tempers, such as T73 and T7351, offer improved resistance to stress-corrosion cracking.
Though 2618 aluminum excels in high-temperature strength, it generally has poor corrosion resistance. Its high copper and nickel content contributes to its vulnerability to corrosion. In corrosive conditions, 2618 aluminum is prone to pitting, making it suitable mainly for applications where high-temperature strength outweighs corrosion resistance concerns. Coatings or corrosion inhibitors are often required to protect 2618 aluminum in corrosive environments.
For applications requiring both high strength and corrosion resistance, 7075 aluminum is generally a better choice, especially in overaged forms like T73. However, neither alloy is naturally immune to corrosion, so additional protective measures—such as anodizing, coatings, or sealants—are essential to extend their service life.
2618 and 7075 aluminum alloys have different levels of temperature resistance based on their melting points and thermal properties. The melting point of 2618 aluminum ranges from approximately 550°C to 640°C, while 7075 aluminum melts at a lower range of 477°C to 635°C. The higher melting point of 2618 aluminum makes it better suited for prolonged exposure to high temperatures.
Both alloys share similar thermal conductivity and heat capacity, which are essential for managing heat in demanding applications. 2618 aluminum has a thermal conductivity of around 160 W/(m·K), while 7075 aluminum ranges from 130 to 190 W/(m·K). Their specific heat capacities are also nearly identical, with 2618 aluminum at approximately 880 J/(kg·K) and 7075 aluminum at around 870 J/(kg·K). This allows both materials to manage heat efficiently and maintain their strength under changing temperatures.
7075 aluminum responds well to heat treatment, which boosts its strength and toughness at different temperatures. This makes it a popular choice for applications where mechanical performance must be maintained under thermal stress. On the other hand, while 2618 aluminum does not respond as dynamically to heat treatment, its inherent thermal stability makes it a reliable option for high-temperature conditions.
Both alloys show similar coefficients of thermal expansion, meaning they expand at similar rates when temperatures change. For 7075 aluminum, the coefficient is about 2.36×10^-5 K^-1, while for 2618 aluminum, it is approximately 22 µm/m·K. This minimizes dimensional changes, ensuring precision and reliability in temperature-sensitive applications.
Thanks to its higher melting point and stability, 2618 aluminum is ideal for high-heat applications like aerospace engines and automotive parts. In contrast, 7075 aluminum’s strength and heat treatment capabilities make it perfect for structural uses like aircraft frames and sports equipment.
Below are answers to some frequently asked questions:
The main differences between 2618 and 7075 aluminum in terms of mechanical properties are primarily related to their strength, hardness, and fatigue resistance. 7075-T6 aluminum exhibits higher ultimate tensile strength (560 MPa) and yield strength (480 MPa) compared to 2618 aluminum, which has a UTS of 420 MPa and yield strength of 350 MPa. In terms of hardness, 7075-T6 aluminum has a Brinell hardness of 150, higher than 2618’s 120. Fatigue strength also varies, with 7075-T6 offering a range of 110 to 190 MPa, whereas 2618 has a fatigue strength of 110 MPa. Although 7075-T6 is stronger, it may be more susceptible to stress corrosion cracking and typically has a lower elongation at break, affecting its formability compared to 2618. These distinctions make 7075-T6 ideal for high-strength applications like aerospace, while 2618 is preferable in situations requiring better thermal properties and resistance to high temperatures.
The chemical compositions of 2618 and 7075 aluminum alloys significantly impact their performance and suitability for different applications. 2618 aluminum contains higher levels of copper (2.20-2.80%) and nickel (0.9-1.2%), which enhance its high-temperature resistance and make it ideal for aerospace and automotive components subjected to extreme heat. Its composition also provides good machinability and workability, but the presence of copper makes it more prone to corrosion, requiring protective treatments in certain environments.
In contrast, 7075 aluminum is rich in zinc (5.1-6.1%) and magnesium (2.1-2.9%), which contribute to its exceptional strength, hardness, and fatigue resistance, making it one of the strongest aluminum alloys available. However, these elements also make it less machinable and more challenging to weld compared to 2618. While 7075 has better corrosion resistance than 2618, it still benefits from coatings in highly corrosive environments. Ultimately, the choice between these alloys depends on the application’s specific requirements, such as strength, heat resistance, or ease of processing.
For high-temperature applications, 2618 aluminum is generally better suited than 7075 aluminum. 2618 is known for its strength retention at elevated temperatures, making it ideal for use in high-temperature environments like engine components. While specific thermal properties for 2618 aren’t detailed, its established performance in such applications suggests it handles heat well. On the other hand, 7075 aluminum, although strong and with good thermal conductivity, is more susceptible to embrittlement and stress corrosion cracking, making it less ideal for high-temperature applications where thermal stability is crucial.
7075 aluminum exhibits superior corrosion resistance compared to 2618 aluminum. This is primarily due to the presence of zinc and magnesium in 7075, which enhance its ability to withstand corrosion. In contrast, 2618 aluminum, with its high copper content, is more susceptible to corrosion, particularly in humid environments and under stress. For applications where corrosion resistance is critical, 7075 aluminum is generally the more suitable choice.
2618 aluminum is generally more challenging to weld than 7075 aluminum due to its higher copper content, which increases the risk of hot cracking and the formation of brittle intermetallic compounds during welding. In contrast, 7075 aluminum, while not ideal for welding compared to non-heat-treatable alloys, has lower copper content and is considered relatively more forgiving when proper welding techniques and parameters are applied.
7075 aluminum is best suited for applications requiring a high strength-to-weight ratio, such as aerospace structures (e.g., aircraft fuselages and wings), high-performance automotive components, recreational equipment like bicycles and climbing gear, military equipment, and precision engineering parts. Its exceptional strength and fatigue resistance make it ideal for these high-stress applications.
On the other hand, 2618 aluminum excels in environments where high thermal conductivity, hardness, and resistance to thermal fatigue are crucial. It is commonly used in aerospace applications like jet engines, automotive components such as pistons and engine blocks, and plastic processing molds. Its ability to withstand high temperatures makes it particularly suitable for high-temperature environments and composite tooling in aerospace and automotive industries.
