2618 vs 7075 Aluminum: What’s the Difference?

When selecting the right aluminum alloy, the choice between 2618 and 7075 can feel like a balancing act between strength, heat resistance, and machinability. Both alloys are powerhouses in demanding industries, but their subtle differences could make or break your next engineering project. Are you striving for top-notch performance at high temperatures, or is raw tensile strength and machine efficiency more crucial to your design? In this article, you’ll discover how 2618 and 7075 aluminum stack up in terms of material properties, common applications, and cost—giving you a clear roadmap to the alloy that best fits your needs. Ready to find out which aluminum stands up to your toughest challenges?

Introduction to Aluminum Alloys

Definition and Overview of Aluminum Alloys

Aluminum alloys are metallic materials primarily composed of aluminum and various other elements that enhance specific properties. These alloys are classified based on their alloying elements and processing techniques, resulting in a diverse range of materials suited for different applications. The primary aim of alloying aluminum is to improve its strength, durability, and other mechanical properties while maintaining its inherent advantages such as lightweight and corrosion resistance.

Importance in Manufacturing and Engineering

Aluminum alloys are essential because they meet demanding performance criteria such as high strength-to-weight ratios, excellent thermal conductivity, and corrosion resistance. These properties make aluminum alloys indispensable for producing components that are both efficient and reliable in industries such as aerospace, automotive, construction, and electronics.

Key Properties of Aluminum Alloys

Lightweight and High Strength

Aluminum alloys are notable for being both lightweight and strong. This combination is particularly beneficial in applications where reducing weight without compromising structural integrity is essential, such as in aircraft and automotive manufacturing.

Corrosion Resistance

Aluminum alloys exhibit excellent corrosion resistance, which is a significant advantage in environments exposed to moisture and other corrosive elements. This property is achieved through the formation of a protective oxide layer on the surface of the alloy, which prevents further corrosion.

Thermal Conductivity

Aluminum alloys have high thermal conductivity, making them ideal for heat exchange applications. This property is essential in industries such as electronics and HVAC systems, where efficient heat dissipation is required.

Machinability and Formability

The machinability and formability of aluminum alloys are key factors in their widespread use. These alloys can be easily shaped and processed using various manufacturing techniques, including casting, extrusion, and machining. This versatility allows for the production of complex components with precise dimensions.

Classification of Aluminum Alloys

Wrought Aluminum Alloys

Wrought aluminum alloys, processed through mechanical means like rolling, extrusion, and forging, are categorized into series based on their primary alloying elements:

• 1000 Series: Pure aluminum with excellent corrosion resistance and high electrical conductivity.
• 2000 Series: Copper-based alloys known for high strength and good machinability.
• 3000 Series: Manganese-based alloys with moderate strength and good corrosion resistance.
• 4000 Series: Silicon-based alloys primarily used in welding applications.
• 5000 Series: Magnesium-based alloys with high strength and excellent corrosion resistance.
• 6000 Series: Magnesium and silicon-based alloys offering good strength, corrosion resistance, and machinability.
• 7000 Series: Zinc-based alloys with the highest strength among aluminum alloys.

Cast Aluminum Alloys

Cast aluminum alloys are produced by pouring molten aluminum into molds to create specific shapes. These alloys are typically used for applications requiring complex geometries and high dimensional accuracy. The primary alloying elements in cast aluminum alloys include silicon, copper, magnesium, and zinc.

Comparison of 2618 Aluminum vs 7075 Aluminum

Composition and Alloy Series

• 2618 Aluminum: This alloy belongs to the 2000 series, characterized by the inclusion of copper, magnesium, and silicon. These elements contribute to its high-temperature strength and machinability.
• 7075 Aluminum: Part of the 7000 series, this alloy is zinc-based. Zinc, magnesium, and copper give it superior strength and fatigue resistance.

Mechanical Properties

Thermal Properties and Applications

• Thermal Conductivity: Both alloys have similar thermal conductivities, with 2618 at about 160 W/(m·K) and 7075 ranging from 130 to 190 W/(m·K).
• Specific Heat Capacity: Both have nearly identical specific heat capacities, with 2618 around 880 J/(kg·K) and 7075 about 870 J/(kg·K).

Workability and Corrosion Resistance

• Machinability and Weldability: 2618 is very machinable and weldable, whereas 7075, though less machinable, can be significantly strengthened through heat treatment.
• Corrosion Resistance: 7075 has excellent corrosion resistance but is more susceptible to stress corrosion cracking compared to 2618.

Detailed Comparison: 2618 Aluminum vs 7075 Aluminum

2618 Aluminum, a copper-based alloy from the 2000 series, stands out for its excellent performance in high-temperature environments and good machinability. Meanwhile, 7075 Aluminum, part of the 7000 series, is known for its exceptional strength and relatively low weight.

Despite sharing about 93% similarity in average composition, 2618 Aluminum and 7075 Aluminum have distinct performance characteristics driven by their principal alloying elements—copper in 2618 and zinc in 7075.

7075 Aluminum is one of the highest-strength aluminum alloys, perfect for applications with high mechanical load and fatigue resistance. Conversely, 2618 Aluminum excels in high-temperature environments, maintaining structural integrity where 7075 would weaken.

2618 Aluminum is easier to machine due to its softer nature, making it ideal for complex shapes. In contrast, 7075 Aluminum, being harder, requires specialized tooling and techniques.

2618 Aluminum is best for aerospace engine parts and automotive components exposed to heat. 7075 Aluminum is ideal for aircraft structures, military gear, and sports equipment, where strength-to-weight ratio and fatigue resistance are crucial.

Application Areas for Each Alloy

Application Areas for 2618 Aluminum Alloy

Aerospace Applications

The aerospace industry relies heavily on 2618 aluminum alloy due to its outstanding resistance to high temperatures. This property makes it ideal for components such as engine pistons and cylinder heads, which are subjected to extreme thermal conditions. The alloy’s ability to maintain strength and structural integrity at elevated temperatures ensures reliability and performance in critical aerospace applications.

Automotive Applications

In the automotive sector, 2618 aluminum is preferred for manufacturing engine parts like pistons and turbocharger components, thanks to its high machinability which allows for precise manufacturing of complex shapes. Furthermore, the alloy’s resistance to thermal fatigue is crucial for parts that undergo frequent temperature fluctuations, ensuring long-term durability and efficiency.

Thermal Fatigue Resistance

2618 aluminum alloy is well-suited for environments with frequent temperature changes due to its excellent thermal fatigue resistance. This characteristic is particularly valuable in aerospace and automotive applications, where components are regularly exposed to varying thermal conditions. The alloy’s stability under such conditions contributes to its widespread use in industries requiring high reliability.

Application Areas for 7075 Aluminum Alloy

Structural Applications

Known for its exceptional strength and fatigue resistance, 7075 aluminum alloy is an ideal choice for structural components in the aerospace industry. It is used in aircraft frames, wings, and other critical structural components where high strength-to-weight ratios are essential. The alloy’s ability to withstand mechanical loads and stress ensures safety and performance in demanding environments.

Sports Equipment

The high strength and lightweight properties of 7075 aluminum make it popular in the manufacturing of sports equipment, such as bicycle frames, baseball bats, and climbing gear. These applications benefit from the alloy’s excellent performance characteristics, providing athletes with durable and efficient equipment that enhances their performance.

Military Equipment

7075 aluminum is extensively used in military applications for its remarkable strength and corrosion resistance, making it suitable for producing armor plating, vehicle components, and weapons systems. The alloy’s ability to endure harsh conditions and mechanical stress makes it a reliable material for defense applications.

Comparative Analysis of Application Areas

2618 aluminum alloy is predominantly used in applications requiring high-temperature resistance and machinability, such as aerospace and automotive engine parts. Conversely, 7075 aluminum alloy excels in structural applications demanding superior strength and fatigue resistance, making it suitable for aircraft structures, sports equipment, and military gear. Both alloys serve critical roles in their respective industries, with 2618 focusing on heat-intensive environments and 7075 on strength-demanding uses.

When choosing between 2618 and 7075 aluminum alloys, consider their unique properties and how they match your application needs.

High-Temperature Performance

For applications requiring superior performance at elevated temperatures, 2618 aluminum is the better choice. Its copper-based composition allows it to maintain strength and structural integrity in high-temperature environments, making it ideal for engine components in aerospace and automotive industries.

Strength and Structural Use

7075 aluminum, with its zinc-based composition, is favored in high-stress structural applications due to its exceptional strength and fatigue resistance, making it suitable for aircraft structures, military equipment, and high-performance sports gear.

Corrosion Resistance

7075 aluminum has better overall corrosion resistance but is more prone to stress corrosion cracking, requiring extra protection. 2618 aluminum is generally resistant to corrosion but can be more vulnerable in humid conditions.

Machinability and Workability

2618 aluminum is easier to machine because of its softer nature, making it ideal for complex components. On the other hand, 7075 aluminum, being harder, poses more challenges during machining but compensates with superior mechanical properties.

Application-Specific Recommendations

• Aerospace and Automotive: 2618 aluminum is recommended for parts subjected to high temperatures, such as engine components.
• Structural and High-Strength Applications: 7075 aluminum is the preferred choice for its strength and fatigue resistance, suitable for aircraft frames and military applications.
• Sports Equipment: 7075 aluminum’s lightweight and high strength make it ideal for manufacturing durable sports gear.

Cost Considerations

Cost and availability are important in material selection. 7075 aluminum is typically more expensive due to its high strength, while 2618 aluminum’s specialized high-temperature performance can also be costly depending on the application. Evaluating the total cost of ownership, including processing and potential protective treatments, is crucial for making an informed decision.

Diagrams and Tables

Composition and Alloy Series

Mechanical Properties

Thermal Properties

Corrosion Resistance

Typical Applications

Visual Comparison Diagram

References

Technical References

The following references provide detailed information on the properties, applications, and processing of 2618 and 7075 aluminum alloys, including standards and technical guidelines relevant to their use in various industries.

Standards and Specifications

• ASTM B209: This standard specifies requirements for aluminum and aluminum-alloy sheets and plates, such as 2618 and 7075 alloys. It provides guidelines on mechanical properties, heat treatment, chemical composition, fabrication processes, and quality control measures.
• AMS 4027: Aerospace Material Specification for 2618 aluminum alloy sheet and plate. It includes requirements for mechanical properties, fabrication processes, and quality control measures.
• AMS 4045: Aerospace Material Specification for 7075 aluminum alloy sheet and plate. This standard details material properties, heat treatment, and typical applications in aerospace.

Technical Papers and Articles

• "The Effect of Heat Treatment on the Mechanical Properties of 7075 Aluminum Alloy": This paper examines how various heat treatments impact the strength, hardness, and fatigue resistance of 7075 aluminum, offering insights for optimizing its use in high-stress environments.
• "High-Temperature Performance of 2618 Aluminum Alloy in Aerospace Applications": This analysis of 2618 aluminum’s thermal stability and fatigue resistance highlights its suitability for engine components exposed to extreme temperatures.

Industry Guidelines

• SAE International’s Aerospace Materials Standards: Comprehensive guidelines covering the selection, processing, and testing of aluminum alloys used in aerospace applications. These standards ensure the reliability and performance of materials like 2618 and 7075 aluminum in critical components.
• The Aluminum Association’s Designation System: A resource that explains the classification of aluminum alloys, including the 2000 and 7000 series. It provides a framework for understanding the properties and applications of different aluminum alloys.

Books and Manuals

• "Aluminum Alloys: Structure and Properties" by L.F. Mondolfo: This book offers a detailed examination of the microstructure, mechanical properties, and applications of various aluminum alloys, including 2618 and 7075. It serves as a valuable reference for engineers and material scientists.
• "The Metallurgy of Aluminum Alloys" by J.E. Hatch: An authoritative text on the metallurgy of aluminum alloys, covering topics such as alloy development, heat treatment, and performance characteristics. It includes specific chapters on the 2000 and 7000 series alloys.

Online Resources

• MatWeb Material Property Data: An online database that provides detailed material properties for 2618 and 7075 aluminum alloys. It includes data on mechanical properties, thermal properties, and typical applications.
• ASM International’s Aluminum Database: A comprehensive resource for information on aluminum alloys, including technical data sheets, processing guidelines, and application notes for 2618 and 7075 aluminum.

These references provide comprehensive information on the properties and applications of 2618 and 7075 aluminum alloys, supporting informed material selection and optimized design.

Frequently Asked Questions

Below are answers to some frequently asked questions:

What are the key differences between 2618 and 7075 aluminum?

The key differences between 2618 and 7075 aluminum primarily lie in their composition, mechanical properties, thermal properties, corrosion resistance, and application suitability.

7075 aluminum is an aluminum-zinc-magnesium-copper alloy known for its exceptional strength and hardness, with an ultimate tensile strength of approximately 560 MPa and a yield strength of around 480 MPa. It also has a higher Brinell hardness (~150) and excellent fatigue resistance, making it ideal for high-stress applications like aircraft structural parts and high-performance sporting equipment. However, it is more prone to embrittlement and stress corrosion cracking at elevated temperatures, and its machinability and weldability are more challenging.

In contrast, 2618 aluminum contains higher copper content, enhancing its high-temperature strength and thermal fatigue resistance, making it more suitable for engine components and aerospace parts subjected to heat. It has a lower ultimate tensile strength (~420 MPa) and yield strength (~350 MPa) compared to 7075 but maintains better elasticity and strength at high temperatures. While it is easier to machine and weld, 2618 aluminum has lower corrosion resistance, particularly in humid or stressed conditions.

Which aluminum alloy is better suited for high-temperature applications?

When comparing 2618 aluminum and 7075 aluminum for high-temperature applications, 2618 aluminum is better suited due to its superior thermal stability and ability to maintain mechanical properties under elevated temperatures. While 7075 aluminum boasts higher ultimate tensile strength and yield strength at room temperature, its performance significantly deteriorates when exposed to high heat. On the other hand, 2618 aluminum, a copper-based alloy from the 2000 series, retains its strength and offers excellent thermal fatigue resistance, making it ideal for applications such as aerospace engine components and automotive pistons that operate under sustained high temperatures.

How do 2618 and 7075 aluminum compare in terms of strength and machinability?

In terms of strength, 7075 aluminum is generally superior to 2618 aluminum. 7075 aluminum, particularly in the T6 temper, has a tensile strength range of 510-540 MPa and a yield strength of 430-480 MPa. This high strength makes it ideal for aerospace structural components and other high-stress applications. On the other hand, 2618 aluminum has a tensile strength of 440-460 MPa and a lower yield strength, making it less robust than 7075 aluminum but still suitable for demanding applications.

Regarding machinability, 2618 aluminum offers better performance due to its moderate hardness and reduced tool wear. It is easier to machine, producing short, broken chips and maintaining dimensional accuracy during high-speed machining. This makes it suitable for precision engine parts. In contrast, 7075 aluminum can be challenging to machine due to its higher hardness, requiring specialized tooling and techniques to prevent cracking and ensure proper chip formation. Thus, while 7075 excels in strength, 2618 is more manageable in machining operations.

What are the common uses of 2618 aluminum in the aerospace industry?

2618 aluminum alloy is commonly used in the aerospace industry due to its high strength, rigidity, and excellent resistance to high temperatures. These properties make it ideal for critical components that operate under severe conditions. Specifically, 2618 aluminum is frequently employed in engine parts, such as compressor blades and pistons, where its ability to maintain structural integrity at elevated temperatures is crucial. Additionally, it is used in rotating components within aircraft engines, where both high strength and thermal stability are essential. The alloy is also applied in various structural parts of aircraft, including brakes and other high-stress components, as well as aerodynamic parts like propellers and landing gear, due to its toughness and fatigue resistance. Overall, 2618 aluminum’s unique properties make it indispensable for high-temperature and high-strength applications in aerospace engineering.

How does the cost of 2618 aluminum compare to 7075 aluminum?

When comparing the cost of 2618 aluminum to 7075 aluminum, 2618 aluminum generally tends to be more expensive. This price difference is due to several factors. Firstly, 2618 aluminum has a more complex manufacturing process and a higher concentration of copper and other elements that provide superior thermal stability, particularly beneficial for high-temperature applications like aerospace engines and automotive parts. These specialized requirements increase both the cost of raw materials and processing.

On the other hand, 7075 aluminum is typically cheaper because it is produced on a larger scale and used extensively in structural applications where high strength is critical but extreme temperature resistance is not as necessary. The heat treatment process for 7075 aluminum is also more efficient and cost-effective, further reducing its overall cost.

What factors should be considered when selecting between 2618 and 7075 aluminum for a project?

When selecting between 2618 and 7075 aluminum for a project, several key factors should be considered:

1. Mechanical Strength and Stress Resistance: 7075 aluminum is known for its exceptional strength and high tensile strength, making it ideal for highly stressed structural applications such as aircraft wings and fuselages. 2618 aluminum, while also strong, offers slightly lower tensile strength but performs better at elevated temperatures, making it suitable for engine components and aerospace parts exposed to heat.

2. Corrosion Resistance: 7075 aluminum has average corrosion resistance and is prone to stress corrosion cracking due to its high zinc and copper content. It often requires protective coatings. In contrast, 2618 aluminum typically exhibits better corrosion resistance under high-temperature conditions.

3. Machinability and Weldability: 7075 aluminum is fairly machinable but has poor weldability, which can significantly weaken its structure. 2618 aluminum, on the other hand, offers better weldability, which is crucial if the project involves welding processes.

4. Thermal Stability: 7075 aluminum performs well at normal temperatures but loses strength at elevated temperatures. 2618 aluminum is preferred for applications requiring sustained mechanical properties at higher temperatures (up to around 300°C).

5. Density and Weight Considerations: Both alloys are lightweight compared to steel, but 7075 aluminum’s excellent strength-to-weight ratio makes it ideal for weight-sensitive applications like aerospace and high-performance sports equipment.

6. Cost and Availability: Availability and cost can vary, but generally, 7075 aluminum might be more expensive due to its higher strength and specialized applications.