Common Aluminum Plate Temper "T" Explained: T6, T651, T6511, and More
GNEE is a professional manufacturer and global supplier of high-quality aluminum plate, including 6061 and 7075 series alloys for precision machining, molds, aerospace, and structural applications. One of the most important factors when selecting aluminum plate is understanding temper designations, especially the widely used "T" temper.
This guide explains the meaning of common T tempers, how they are processed, and how 6061-T6 aluminum plate differs from 7075-T651 aluminum plate, helping you choose the right material with confidence.
What Does the Aluminum Temper "T" Mean?
The "T" temper stands for Thermally Treated (Heat Treated). It applies to heat-treatable aluminum plate alloys and is the most commonly used temper symbol in aluminum engineering.
Aluminum plates with a T temper undergo:
Solution heat treatment
Rapid quenching
Natural or artificial aging
Different numbers following "T" define specific heat-treatment sequences, stress-relief methods, and mechanical property levels.
Common "T" Tempers for Aluminum Plate Explained
6061 T3 Aluminum Plate
Solution heat treated
Cold worked
Naturally aged to a stable condition
Used where cold working improves strength (e.g., straightened products)
6061 T4 Aluminum Plate
Solution heat treated
Naturally aged
No cold working after heat treatment
Suitable where forming is required before final strength develops
6061 T5 Aluminum Plate
Formed at high temperature (casting or extrusion)
Cooled, then artificially aged
Improves strength and dimensional stability without solution treatment
6061 T6 Aluminum Plate
Solution heat treated
Artificially aged
Most common temper for 6061 aluminum plate
Balanced strength, machinability, and corrosion resistance
6061 T651 Aluminum Plate
Based on T6
Includes controlled stretching after heat treatment to relieve internal stress
Mainly used for thick aluminum plate
Excellent dimensional stability during machining
6061 T6511 Aluminum Plate
Similar to T651
Additional straightening after stretching
Common for extruded bars and plates
Permanent deformation typically 1–3%
Summary of T Tempers for 6061 & 7075 Aluminum Plate
Although 6061 and 7075 aluminum plates share the same chemical composition within their alloy families, different T tempers (T6, T651, T6511) mainly affect:
Residual stress levels
Machining stability
Risk of deformation
Flatness and dimensional accuracy
T651 and T6511 aluminum plates have lower internal stress than T6, making them less prone to warping during CNC machining.
Aluminum Plate "T" Temper Heat Treatment Process
Step 1: Solution Heat Treatment & Quenching
The aluminum plate is heated to approximately 527°C and held for about 1 hour. This dissolves alloying elements (Mg, Si, Zn) into the aluminum matrix.
The plate is then quenched rapidly in water to prevent premature precipitation.
Step 2: Aging Treatment
The plate is reheated to approximately 177°C and held for 1–18 hours, depending on thickness and application.
This step forms Mg₂Si precipitates, significantly increasing strength and hardness.
6061-T6 Aluminum Plate vs 7075-T651 Aluminum Plate
6061-T6 Aluminum Plate (6000 Series)
Main alloying elements: Magnesium (Mg) + Silicon (Si)
Strengthening phase: Mg₂Si
Excellent weldability and corrosion resistance
Good machinability and formability
Widely used in machinery, architectural structures, and general engineering
6061 aluminum plate is one of the most versatile heat-treatable alloys and is often the first choice for mechanical and structural applications.
7075-T651 Aluminum Plate (7000 Series)
Main alloying element: Zinc (Zn), with Mg and Cu
Strengthening phases: MgZn₂ and AlCuMg
Stress-relieved by stretching (T651)
Extremely high strength, comparable to some steels
Preferred for aerospace and high-stress components
While machinability is lower than 6061, 7075 aluminum plate offers an exceptional strength-to-weight ratio.
Typical Chemical Composition of Aluminum Plate
6061 Aluminum Plate
| Element | Content (%) |
|---|---|
| Aluminum | Balance |
| Magnesium | 0.8 – 1.2 |
| Silicon | 0.4 – 0.8 |
| Copper | 0.15 – 0.40 |
| Chromium | 0.04 – 0.35 |
7075 Aluminum Plate
| Element | Content (%) |
|---|---|
| Aluminum | Balance |
| Zinc | 5.1 – 6.1 |
| Magnesium | 2.1 – 2.9 |
| Copper | 1.2 – 2.0 |
Typical Mechanical Properties of Aluminum Plate
| Alloy & Temper | Tensile Strength (MPa) | Yield Strength (MPa) |
|---|---|---|
| 6061-T6 | ~290 | ~240 |
| 6061-T651 | ~290 | ~240 |
| 7075-T651 | ~570 | ~500 |
Other Aluminum Plate Temper Designations
F (As Fabricated): No special heat treatment or strain hardening
O (Annealed): Softest condition, maximum ductility
H (Strain Hardened): For non-heat-treatable alloys (e.g., 5xxx series)
W (Solution Heat Treated): Temporary, unstable condition
Common Machining Problems & GNEE's Solutions
Problem: Sand holes or grain defects after polishing
Solution:
GNEE applies a grain refinement process and ultrasonic flaw detection, ensuring aluminum plates are free from bubbles, inclusions, and internal defects.
Problem: Deformation of 7075 aluminum plate after machining
Solution:
GNEE supplies 7075-T651 aluminum plate with complete stress-relief stretching, eliminating warping, cracking, and post-machining deformation.
What Does "AA" Mean in AA6061 or AA7075?
AA stands for Aluminum Association (USA).
It indicates the aluminum plate grade complies with American Aluminum Association standards for production and inspection.
Conclusion: Choosing the Right Aluminum Plate Temper
Understanding T tempers is essential when selecting aluminum plate for machining, molds, aerospace, or structural use:
T6 → General strength and versatility
T651 / T6511 → Stress-relieved, stable machining
6061 aluminum plate → Balanced performance
7075 aluminum plate → Maximum strength
Choosing the correct temper ensures dimensional stability, processing efficiency, and long-term performance.
Contact GNEE for Aluminum Plate Solutions
GNEE supplies premium 6061 and 7075 aluminum plates in T6, T651, and T6511 tempers, with full certification and custom sizes available.
Need technical advice or a fast quotation?
Contact GNEE today to get professional aluminum plate solutions tailored to your project.
