Aluminum Heat Treatment Guide: Understanding T Temper Designations
Aluminum heat treatment dramatically improves mechanical properties through controlled heating and cooling processes. This guide explains temper designations, heat treatment processes, and selection criteria for optimal performance.
Understanding Aluminum Temper Designations
The T temper designation indicates thermally treated, thermally treated and naturally aged, or thermally treated and cold worked:
- T1: Cooled from elevated temperature and naturally aged
- T2: Cooled from elevated temperature, cold worked, and naturally aged
- T3: Solution heat treated, cold worked, and naturally aged
- T4: Solution heat treated and naturally aged
- T5: Cooled from elevated temperature and artificially aged
- T6: Solution heat treated and artificially aged
- T7: Solution heat treated and over-aged/stabilized
- T8: Solution heat treated, cold worked, and artificially aged
- T9: Solution heat treated, artificially aged, and cold worked
- T10: Cooled from elevated temperature, cold worked, and artificially aged
Common T Temper Conditions
T3: Solution Heat Treated, Cold Worked, Naturally Aged
- Process: Heat to solution temperature → quench → cold work → natural aging
- Properties: Improved strength from cold work, good corrosion resistance
- Common alloys: 2024
T4: Solution Heat Treated and Naturally Aged
- Process: Heat to solution temperature → quench → natural aging at room temperature
- Properties: Good ductility, moderate strength, excellent formability
- Common alloys: 6061-T4, 5052-H32
T6: Solution Heat Treated and Artificially Aged
- Process: Heat to solution temperature → quench → age harden at elevated temperature
- Properties: Maximum strength, good machinability, moderate corrosion resistance
- Common alloys: 6061-T6, 7075-T6
T651: T6 with Stress Relieved
- Process: T6 with stretching to relieve internal stresses
- Properties: High strength with dimensional stability
- Common alloys: 6061-T651, 7075-T651
Heat Treatment Process Details
1. Solution Heat Treatment
| Alloy | Solution Temp (°C) | Typical Time (hrs) |
|---|---|---|
| 6061 | 525-540 | 1-2 |
| 6063 | 515-525 | 1 |
| 7075 | 460-480 | 1-2 |
| 2024 | 485-500 | 1-2 |
2. Quenching
- Water quench: Fastest cooling, highest distortion risk
- Polymer quench: Slower than water, reduced distortion
- Air quench: For certain alloys, less distortion
3. Artificial Aging (Precipitation Hardening)
| Alloy | Aging Temp (°C) | Typical Time (hrs) | Resulting Temper |
|---|---|---|---|
| 6061 | 170-180 | 8-12 | T6 |
| 6063 | 175-185 | 6-8 | T6 |
| 7075 | 120-130 | 24 | T6 |
| 2024 | 185-195 | 8-12 | T6 |
Mechanical Properties by Temper
| Alloy-Temper | Tensile Strength (MPa) | Yield Strength (MPa) | Elongation (%) |
|---|---|---|---|
| 6061-O | 124 | 55 | 25 |
| 6061-T4 | 241 | 145 | 22 |
| 6061-T6 | 310 | 276 | 12 |
| 6063-O | 90 | 48 | 25 |
| 6063-T5 | 152 | 110 | 12 |
| 6063-T6 | 241 | 214 | 12 |
| 7075-T6 | 572 | 503 | 11 |
| 2024-T3 | 483 | 345 | 18 |
Applications by Temper
T4 Temper Applications
- Forming operations: Better ductility allows complex shapes
- Structural components: Good strength with easy fabrication
- Automotive body panels: Stamping and forming
T6 Temper Applications
- Aerospace structures: High strength-to-weight ratio
- Bicycle frames: Maximum strength for thin-walled tubes
- Con precision parts: Excellent machinability
- Marine hardware: Strong, corrosion-resistant
T651 Temper Applications
- Machined parts: Dimensional stability after cutting
- Tooling: Low residual stress
- Optical equipment: Minimal distortion over time
Annealing and Softening
O temper indicates fully annealed, softened condition:
- Purpose: Maximum ductility for forming
- Process: Heat to annealing temperature → hold → slow cool
- Result: Lowest strength, highest formability
| Alloy | Annealing Temp (°C) | Purpose |
|---|---|---|
| 6061 | 415 | Full anneal |
| 6063 | 415 | Full anneal |
| 7075 | 415 | Full anneal |
Conclusion
Understanding aluminum heat treatment and temper designations helps engineers select the right material condition for their application. T6 provides maximum strength, while T4 offers better formability.
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Tracy
Email: tracy@coremetalsteel.com
WhatsApp: +86 182 9191 0632