VII. Corrosion Behavior of 7475 t7351
A. Stress Corrosion Cracking Resistance
7475 T7351 aluminum alloy exhibits excellent stress corrosion cracking (SCC) resistance in most environments, including seawater, aerospace fluids, and chemicals. This resistance is attributed to the alloy’s high strength, low chloride content, and the presence of protective oxide layers.
B. Pitting Corrosion Resistance
7475 T7351 has good pitting corrosion resistance in a wide range of environments. The alloy’s protective oxide layers, along with its low copper content, help to minimize the initiation and propagation of pits.
Pitting Corrosion Resistance Comparison with Other Aluminum Alloys
The following table compares the pitting corrosion resistance of 7475 T7351 to other commonly used aluminum alloys:
| Alloy | Pitting Corrosion Resistance |
|—|—|
| 7475 T7351 | Good |
| 2024 T3 | Poor |
| 6061 T6 | Moderate |
| 7075 T6 | Good |
Corrosion Behavior in Specific Environments
- Seawater: 7475 T7351 has excellent corrosion resistance in seawater, comparable to or better than other high-strength aluminum alloys.
- Aerospace Fluids: The alloy is highly resistant to corrosion by aerospace fluids, such as jet fuels and hydraulic fluids.
- Chemicals: 7475 T7351 is generally resistant to most chemicals, including acids, bases, and solvents. However, it may be susceptible to corrosion in highly corrosive environments, such as concentrated acids or strong alkalis.
Factors Affecting Corrosion Behavior
Several factors can influence the corrosion behavior of 7475 T7351, including:
- Heat Treatment: The T7351 heat treatment provides the alloy with its optimal strength and corrosion resistance.
- Surface Condition: Smooth, well-prepared surfaces are less susceptible to corrosion.
- Environment: The type of environment (e.g., seawater, aerospace fluids, chemicals) plays a significant role in the corrosion behavior of the alloy.
- Protective Coatings: Applying protective coatings, such as anodizing or painting, can further enhance the corrosion resistance of 7475 T7351.
Mitigation of Corrosion
To mitigate corrosion in 7475 T7351, several strategies can be employed:
- Proper Heat Treatment: Ensure that the alloy is properly heat treated to achieve the desired strength and corrosion resistance.
- Surface Preparation: Clean and prepare surfaces thoroughly before application.
- Environmental Control: Minimize exposure to corrosive environments whenever possible.
- Protective Coatings: Apply protective coatings, such as anodizing or painting, to provide an additional barrier against corrosion.
- Stress Relief: If SCC is a concern, consider stress relief annealing to reduce residual stresses.
VIII. Welding of 7475 t7351
A. Weldability Considerations
7475 T7351 is a high-strength aluminum alloy that can be welded using various methods. However, its low weldability due to its high strength and susceptibility to cracking requires careful consideration of welding parameters. Key weldability considerations include:
- High weldability temperature to minimize the formation of intermetallic phases.
- High welding heat input to compensate for the alloy’s high thermal conductivity.
- Careful control of welding parameters to prevent weld shrinkage and distortion.
- Use of appropriate filler materials to maintain strength and avoid corrosion.
B. Recommended Welding Methods
The following welding methods are recommended for 7475 T7351:
| Welding Method | Advantages | Disadvantages |
|—|—|—|
| Gas Tungsten Arc Welding (GTAW) | Precise, high-quality welds; low heat input | Skilled operators required; slow process |
| Gas Metal Arc Welding (GMAW) | Fast, economical; high deposition rate | Susceptible to porosity and oxidation |
| Laser Beam Welding (LBW) | Narrow, deep welds with minimal heat input | High equipment cost; requires precise joint preparation |
| Electron Beam Welding (EBW) | High-quality, deep welds with minimal distortion | Requires vacuum chamber; limited workpiece size |
Welding Parameters
Optimal welding parameters vary depending on the welding method, joint design, and workpiece thickness. The following table provides general welding parameters for 7475 T7351:
| Parameter | Range |
|—|—|
| Preheat Temperature | 150-250 °C (300-480 °F) |
| Interpass Temperature | 100-150 °C (210-300 °F) |
| Welding Speed | 15-30 cm/min (6-12 in/min) |
| Welding Current | 150-350 A |
| Arc Voltage | 10-15 V |
| Heat Input | 0.5-1.5 kJ/mm |
Post-Weld Treatment
Post-weld heat treatment (PWHT) is often used to improve the strength and toughness of welded 7475 T7351 components. The recommended PWHT cycle is:
- Solution heat treatment at 495 °C (923 °F) for 1 hour per 25 mm (1 in) of thickness.
- Quench in cold water or forced air.
- Artificial aging at 120 °C (248 °F) for 24 hours.
IX. Machinability of 7475 t7351
Introduction:
7475-T7351 is a high-strength aluminum alloy widely used in aerospace, defense, and high-performance automotive applications. Its excellent strength-to-weight ratio makes it ideal for demanding components such as aircraft frames, landing gear, and structural parts. However, machining this alloy can be challenging due to its high hardness and toughness.
A. Cutting Tools:
- Carbides: Tungsten carbide and coated carbide tools are primarily used for machining 7475-T7351. These tools provide good wear resistance and tool life.
- High-Speed Steel (HSS): HSS tools are less expensive than carbides but have lower wear resistance. They are often used for roughing operations or when precision is not critical.
- Cryogenic Tools: Cryogenically treated tools have improved wear resistance and toughness, resulting in longer tool life and better surface finishes.
- Diamond-Coated Tools: Diamond-coated tools provide exceptional wear resistance but are more expensive than other options. They are ideal for high-volume production or machining complex geometries.
B. Cutting Parameters:
The appropriate cutting parameters for machining 7475-T7351 are crucial for achieving optimal performance. Here are some guidelines:
1. Cutting Speed:
- Use lower cutting speeds compared to softer aluminum alloys.
- Start with a conservative speed and gradually increase it until the desired surface finish is achieved.
- For carbides, a speed range of 100-200 m/min is a good starting point.
- For HSS, use speeds in the range of 50-100 m/min.
2. Feed Rate:
- Use low feed rates to prevent excessive tool wear.
- For carbides, a feed rate of 0.05-0.15 mm/rev is recommended.
- For HSS, use feed rates of 0.025-0.075 mm/rev.
3. Depth of Cut:
- Take shallow cuts to minimize tool deflection and improve surface quality.
- For finishing operations, depth of cut should be 0.5-1 mm.
- For roughing operations, it can be increased to 2-3 mm.
4. Coolant:
- Use a high-pressure coolant to evacuate chips and reduce friction at the cutting zone.
- Soluble oil or synthetic coolants are recommended.
5. Lubrication:
- Apply a cutting oil or paste to the cutting zone to further reduce friction and extend tool life.
Comparison of Cutting Parameters:
| Cutting Parameter | Carbide | HSS |
|—|—|—|
| Cutting Speed (m/min) | 100-200 | 50-100 |
| Feed Rate (mm/rev) | 0.05-0.15 | 0.025-0.075 |
| Depth of Cut (mm) | 0.5-3 | 0.5-3 |
Additional Tips:
- Use sharp cutting tools to ensure a clean cut and minimize tool wear.
- Maintain a rigid setup to prevent vibrations and improve surface finish.
- Consider using high-performance machining techniques such as high-speed machining (HSM) or micromilling for improved efficiency and precision.
- Experiment with different cutting parameters and tools to determine the optimal settings for specific applications.
X. Forging of 7475 t7351
Introduction
7475 T7351 is an aluminum alloy with high strength, low density, and excellent corrosion resistance. It is commonly used in aerospace, automotive, and marine applications. Forging is a metalworking process that improves the mechanical properties of 7475 T7351 by shaping the material under high pressure.
A. Forging Equipment
The following equipment is typically used for forging 7475 T7351:
| Equipment | Function |
|—|—|
| Hydraulic press | Applies pressure to the workpiece |
| Forging dies | Shapes the workpiece |
| Heating furnace | Heats the workpiece to the forging temperature |
| Quenching tank | Cools the workpiece after forging |
| Tempering oven | Stabilizes the microstructure of the workpiece |
B. Forging Process
The forging process consists of the following steps:
- Heating: The workpiece is heated to a temperature between 450°C and 510°C. This temperature is below the recrystallization temperature of the alloy, which prevents grain growth and maintains the desired strength properties.
- Forging: The heated workpiece is placed between forging dies and subjected to high pressure. This pressure forces the material to flow into the shape of the dies.
- Quenching: The workpiece is rapidly cooled in a water or oil quenching tank. This quenching process locks in the desired microstructure and prevents the alloy from becoming too soft.
- Tempering: The quenched workpiece is heated to a temperature between 165°C and 190°C and held for a period of time. Tempering stabilizes the microstructure, reduces residual stresses, and improves the alloy’s toughness.
Parameter Comparison
The forging parameters for 7475 T7351 can significantly affect the final properties of the workpiece. The following table compares different parameters and their effects:
| Parameter | Effect |
|—|—|
| Forging temperature | Higher temperature results in lower strength and higher toughness |
| Cooling rate | Faster cooling rates produce finer grain size and higher strength |
| Tempering temperature | Higher temperature reduces strength and increases toughness |
| Tempering time | Longer time improves dimensional stability and machinability |
Conclusion
Forging is a critical process for improving the mechanical properties of 7475 T7351 aluminum alloy. By carefully controlling the forging parameters, it is possible to achieve the desired combination of strength, toughness, and other properties for specific applications.
XI. Standards and Specifications
The standardization of materials and processes is crucial for ensuring the quality, safety, and performance of products. In the context of building and construction, two prominent organizations play a significant role in setting industry standards: ASTM International and the Aluminum Association.
A. ASTM International
ASTM International (originally the American Society for Testing and Materials) is an international standards organization that develops and publishes technical standards for a wide range of materials, products, systems, and services.
ASTM standards for metal building materials include:
- ASTM A6/A6M-15: Standard Specification for Zinc-Coated Steel Sheets for Roofing and Siding
- ASTM A792/A792M-15: Standard Specification for Steel Sheet, Zinc-Coated (Galvanized) or Aluminum-Coated (Galvannealed) by the Hot-Dip Process
- ASTM A924/A924M-16: Standard Specification for General Requirements for Steel Sheet, Zinc-Coated (Galvanized) or Zinc-Iron Alloy-Coated (Galvannealed) by the Hot-Dip Process
B. Aluminum Association
The Aluminum Association is a trade association that represents the aluminum industry in the United States. It develops and publishes standards for the production and use of aluminum materials.
Aluminum Association standards for metal building materials include:
- AA 3003: Standard Specification for Aluminum Sheet and Plate
- AA 3105: Standard Specification for Aluminum Alloy 3105-H19 Sheet
- AA 5005: Standard Specification for Aluminum Alloy 5005-H19 Sheet
Comparison of Product Parameters
The following table compares some key product parameters for metal building materials according to ASTM and Aluminum Association standards:
| Parameter | ASTM | Aluminum Association |
|—|—|—|
| Material | Zinc-coated steel, aluminum-coated steel | Aluminum |
| Coating | Zinc, aluminum-zinc alloy | None |
| Thickness | Varies | 0.019-0.040 inches |
| Strength | High | Medium |
| Corrosion resistance | Good | Excellent |
| Weight | Heavy | Light |
| Cost | Relatively low | Relatively high |
Choosing the Right Standard
The choice of which standard to use for a particular application depends on factors such as the desired properties of the material, the intended use, and the applicable building codes. ASTM standards are widely accepted in the building industry, while Aluminum Association standards are more specific to aluminum materials.
By adhering to established standards, architects, engineers, and contractors can ensure the quality and reliability of metal building materials, contributing to a safe, durable, and sustainable built environment.
XII. Other Considerations
Cost
The cost of a product is a major factor to consider when making a purchase. The price of a product can vary depending on a number of factors, including the brand, the features, and the availability. It is important to compare the prices of different products before making a purchase to ensure that you are getting the best value for your money.
Availability
The availability of a product is another important factor to consider when making a purchase. If a product is not available, you will not be able to purchase it. It is important to check the availability of a product before making a purchase to ensure that you will be able to get the product when you need it.
Environmental impact
The environmental impact of a product is another important factor to consider when making a purchase. Some products have a greater environmental impact than others. It is important to consider the environmental impact of a product before making a purchase to ensure that you are making a choice that is sustainable.
Table of Comparison
The following table compares the cost, availability, and environmental impact of three different products.
| Product | Cost | Availability | Environmental impact |
|—|—|—|—|
| Product A | $100 | In stock | Low |
| Product B | $150 | Out of stock | Moderate |
| Product C | $200 | Available for preorder | High |
As you can see from the table, Product A has the lowest cost, Product B has the highest cost, and Product C has a moderate cost. Product A is in stock, Product B is out of stock, and Product C is available for preorder. Product A has a low environmental impact, Product B has a moderate environmental impact, and Product C has a high environmental impact.
Conclusion
When making a purchase, it is important to consider the cost, availability, and environmental impact of the product. By considering these factors, you can make an informed decision about which product is the best choice for you.