What is the difference between 7075 T6 vs T6511 vs T73 vs T7351？
When engineers reach for 7075 aluminum, the reason is almost always the same: strength. Few aluminum alloys match its combination of high strength, low weight, and machinability — which is why it remains a default choice in aerospace, tooling, and high-performance mechanical applications.
The alloy designation alone does not determine how the material performs. A 7075-T6 plate and a 7075-T7351 plate share the same chemical composition, but they show different performance during machining and in service.
The temper controls not only strength. It influences residual stress, dimensional stability, resistance to stress corrosion cracking (SCC), toughness, and long-term reliability.
For that reason, knowing the difference between T6, T6511, T73, and T7351 seems more important.
The Temper Designations
All four tempers begin with the same base alloy and the same initial heat treatment process.
Solution Heat Treatment
The material is heated to a temperature where the primary alloying elements dissolve into a solid solution. It is then rapidly quenched to retain that structure.
At this stage, the alloy has the potential for high strength but has not yet developed it.
Artificial Aging
After quenching, the material is aged at controlled temperatures to form strengthening precipitates throughout the microstructure.
The aging cycle determines whether the alloy reaches peak strength (T6/T6511) or is intentionally overaged for improved corrosion resistance (T73/T7351).
Stress Relief by Stretching
Some tempers include an additional stretching operation after quenching.
This process removes much of the residual stress introduced during rapid cooling. The improvement is particularly important for parts that will undergo significant machining, where internal stress can cause distortion once material is removed.
The "51" designation indicates stress relief by stretching.
7075-T6: Peak Strength Condition
T6 is the peak-strength temper for 7075 aluminum.
After solution heat treatment, the material is artificially aged to maximize tensile and yield strength.
Characteristics
Highest strength among the four tempers
Widely available in multiple product forms
Good fatigue performance
Moderate SCC resistance
Relatively high residual stress
Typical Mechanical Properties
| Property | Value |
|---|---|
| Tensile Strength | 510–570 MPa |
| Yield Strength | 430–505 MPa |
| Elongation | 8–11% |
Where 7075 T6 is Used
T6 is often selected when strength is the primary design requirement and corrosion exposure is limited.
Examples include:
Structural fittings
High-strength fasteners
Forgings
Mechanical hardware
Components with limited machining after purchase
One practical limitation is distortion during machining. Large parts machined from unstress-relieved stock may move as material is removed, requiring additional machining allowances or process controls.
7075-T6511: Peak Strength with Improved Dimensional Stability
From a strength standpoint, T6511 is very close to T6.
The key difference is that the material is stretched after quenching to relieve residual stress before the aging process is completed.
For many machine shops, this distinction is more important than the published strength values.
Characteristics
Strength essentially equivalent to T6
Lower residual stress
Better dimensional stability during machining
Commonly supplied as bar, rod, and extruded shapes
Typically produced to AMS 4045 requirements
Typical Mechanical Properties
| Property | Value |
|---|---|
| Tensile Strength | 510–570 MPa |
| Yield Strength | 430–505 MPa |
| Elongation | 8–11% |
Where 7075 T6511 is Used
T6511 is frequently specified for precision-machined components produced from bar stock.
Typical examples include:
Aerospace fittings
Tooling components
Mold frames
High-strength shafts
Precision mechanical parts
In many cases, the decision between T6 and T6511 has little to do with strength. It comes down to whether dimensional stability during machining is important to the finished part.
In practice, T6511 is most commonly encountered in aerospace round bar and extruded products. The reduced residual stress helps maintain dimensional accuracy when large amounts of material are removed during machining.
7075-T73: Reduced Strength for Improved Corrosion Resistance
T73 is produced using a controlled overaging process.
Compared with T6, the precipitate structure is intentionally allowed to coarsen beyond the peak-strength condition. While this reduces mechanical strength, it significantly improves resistance to stress corrosion cracking.
For components exposed to moisture and sustained tensile loads over long service periods, that trade-off is often worthwhile.
Characteristics
Lower strength than T6/T6511
Excellent SCC resistance
Improved fracture toughness
Suitable for long-term outdoor or marine exposure
Available in plate, sheet, and extrusion forms
Typical Mechanical Properties
| Property | Value |
|---|---|
| Tensile Strength | 460–500 MPa |
| Yield Strength | 390–430 MPa |
| Elongation | 9–12% |
Where 7075-T73 is Used
Applications commonly include:
Aircraft structural members
Marine-adjacent hardware
Long-service aerospace components
Parts exposed to humid environments
Structures carrying sustained loads
Although T73 offers substantial corrosion benefits, it does not include the stress-relief stretching step found in T7351.
T73 is also widely used in forged aerospace components where long-term environmental durability is a higher priority than achieving the maximum possible strength.
7075-T7351: Corrosion Resistance and Machining Stability Combined
T7351 combines two advantages:
The overaged corrosion-resistant structure of T73
Stress relief through stretching
As a result, it is often selected when both long-term durability and machining stability are important.
Characteristics
Excellent SCC resistance
Low residual stress
Improved dimensional stability
Good toughness
Commonly supplied as plate
Typically produced to AMS 4078 requirements
Typical Mechanical Properties
| Property | Value |
|---|---|
| Tensile Strength | 470–540 MPa |
| Yield Strength | 390–470 MPa |
| Elongation | 8–11% |
Where 7075-T7351 is Used
T7351 is commonly specified for machined aerospace plate components such as:
Wing structures
Bulkheads
Frames
Structural brackets
Large precision-machined parts
For thick plate applications, engineers are often balancing three competing requirements:
Strength
Corrosion resistance
Dimensional stability
T7351 provides a practical compromise between all three.
Side-by-Side Comparison
| Property | T6 | T6511 | T73 | T7351 |
|---|---|---|---|---|
| Tensile Strength | 510–570 MPa | 510–570 MPa | 460–500 MPa | 470–540 MPa |
| Yield Strength | 430–505 MPa | 430–505 MPa | 390–430 MPa | 390–470 MPa |
| SCC Resistance | Moderate | Moderate | Excellent | Excellent |
| Residual Stress | High | Low | Moderate | Very Low |
| Dimensional Stability | Fair | Good | Moderate | Excellent |
| Toughness | Moderate | Moderate | Good | Better |
| Typical Product Form | Various | Bar / Rod | Plate / Sheet | Plate |
| Common Specification | — | AMS 4045 | — | AMS 4078 |
7075 Aluminum Typical Product Forms
Although temper designations describe the heat treatment condition of the alloy, engineers typically purchase 7075 in a specific product form. In many cases, the available temper depends on whether the material is supplied as tube, bar, plate, or forging stock.
Understanding the relationship between product form and temper can simplify material selection and help avoid unnecessary processing costs.
7075 Aluminum Tube
Seamless cold-drawn tubing is commonly used when a lightweight structure requires high strength and consistent mechanical properties throughout the cross-section.
Depending on the application environment, tubing may be supplied in T6, T73, or T7351 condition.
For example, aerospace hydraulic systems, structural tubing, and high-performance mechanical assemblies often use 7075 T6 T73 T7351 Aluminum Tube Cold Drawn Seamless products when weight reduction and mechanical performance are both critical requirements.
7075 Aluminum Round Bar and Rod
Round bar is frequently selected for CNC-machined components because it offers flexibility in machining and material utilization.
When distortion during machining is a concern, stress-relieved stock is generally preferred.
Many aerospace machine shops choose Cold Drawn Finished 7075 T6 T6511 Aluminum Aerospace Round Bar because it provides the strength associated with T6 while improving dimensional stability during machining.
Typical applications include:
Aerospace fittings
Shafts
Precision tooling
Mechanical components
Structural hardware
7075 Aluminum Forgings
Forged products are often selected when grain flow, structural integrity, and mechanical performance are important design considerations.
Unlike plate or bar stock, forgings can provide a near-net-shape starting point that reduces machining time and material waste.
For corrosion-sensitive applications, 7075-T73 Forged Aluminum AMS 4126 Stock remains a common specification for aerospace structural components that may experience long service lives in demanding environments.
Typical examples include:
Landing gear components
Structural fittings
Aircraft attachments
High-load mechanical parts
7075 Aluminum Plate
Large structural parts are frequently machined from thick plate rather than produced from forgings.
In these situations, both residual stress and corrosion resistance become important considerations.
This is one reason why AMS 4078 Aluminum Plate 7075 T7351 Aircraft material is commonly specified for heavily machined aerospace structures.
Typical applications include:
Wing structures
Bulkheads
Frames
Structural brackets
Aircraft support structures
The combination of stress-relief stretching and overaging helps minimize distortion while maintaining excellent resistance to stress corrosion cracking.
7075 Temper Selection by Product Form
For many buyers, the easiest way to narrow down the correct temper is to start with the product form being used.
| Product Form | Common Temper |
|---|---|
| Tube | T6,T6511,T73 |
| Round Bar | T6,T6511,T73,T73511 |
| Forging | T6,T73 |
| Plate | T6,T651,T73,T7351,T851 |
How to Choose the Right Temper
Maximum Strength
→ T6 or T6511
Corrosion-Critical Environment
→ T73 or T7351
Precision Machining from Bar
→ T6511
Precision Machining from Plate
→ T7351
Aerospace Specification Compliance
→ Verify AMS requirements before sourcing material.
Frequently Asked Questions
What is the difference between T6 and T6511?
The mechanical properties are nearly identical.
The primary difference is residual stress. T6511 has been stretched after quenching, which improves dimensional stability and reduces the likelihood of movement during machining.
What is the difference between T73 and T7351?
Both tempers are overaged and provide excellent resistance to stress corrosion cracking.
T7351 includes an additional stress-relief stretching step, making it better suited for precision-machined plate applications.
Why is T73 weaker than T6?
The reduction in strength is intentional.
T6 represents the peak-strength condition of 7075. T73 is overaged to improve corrosion resistance and toughness, sacrificing some strength in exchange for improved long-term durability.
Is T6511 the same as T651?
Not exactly.
Both tempers are stress-relieved by stretching, but T6511 includes an additional straightening operation. T6511 is commonly associated with extruded products, bars, and rods.
Which temper is most commonly used in aerospace applications?
There is no single aerospace temper.
Different components use different tempers depending on loading conditions, corrosion exposure, manufacturing processes, and certification requirements.
In practice:
T6 and T6511 are common for fittings and machined hardware.
T73 is used where SCC resistance is critical.
T7351 is frequently specified for thick structural plate components.
Summary
Choosing a 7075 temper is ultimately a matter of balancing strength, corrosion resistance, and manufacturing requirements.
If maximum strength is the goal, T6 and T6511 are typically the leading options.
If long-term durability in demanding environments is a concern, T73 and T7351 provide significantly better resistance to stress corrosion cracking.
For machined components, residual stress often becomes just as important as strength. In those cases, T6511 bar and T7351 plate are often preferred because they provide greater dimensional stability during manufacturing while retaining the core advantages of 7075 aluminum.