Aluminum alloys are vital in aerospace, automotive, construction, and manufacturing thanks to their lightweight, corrosion resistance, and strength. But not all aluminum is the same — heat treatment, known as tempers, plays a decisive role in performance.

This guide explains the T4, T5, and T6 tempers — how they’re processed, their mechanical properties, best applications, and what professionals in steel and metals need to know for material selection.

🔍 What Are Aluminum Tempers?

The aluminum temper system—standardized by the Aluminum Association (AA)—includes letter-number designations indicating treatment and mechanical properties:

• T4 – Solution heat-treated & naturally aged

• T5 – Cooled after extrusion & artificially aged

• T6 – Solution heat-treated & artificially aged to maximize strength

Understanding these distinctions is crucial for matching alloy properties to your project requirements.

⚙️ T4 Temper – Formable & Weldable

Process: Solution heat treatment followed by natural aging at room temperature.

Properties:

• Tensile strength around 180–210 MPa (26–30 ksi)

• Yield strength approx. 110 MPa (16 ksi)

• Elongation 10–16% — good ductility en.wikipedia.org+3modulusmetal.com+3aludepot.com+3reddit.com+6shop.machinemfg.com+6en.m.wikipedia.org+6aludepot.com+1modulusmetal.com+1

Ideal For:

• Components needing forming or welding post-extrusion

• Examples: Aircraft skins, automotive panels (e.g., 2024-T4, 6061-T4)

🔧 T5 Temper – Stonger Extruded Shapes

Process: Extrusion followed by artificial aging, omitting solution heat treatment.

Properties:

• Tensile strength higher than T4, but lower than T6

• Moderate ductility

Ideal For:

• Finished extrusions requiring more strength

• Examples: Window frames, heat sinks, tubing (e.g., 6063-T5)

💪 T6 Temper – Maximum Strength & Wear Resistance

Process: Solution heat treatment followed by artificial aging.

Properties:

• Tensile strength ~290–310 MPa (42–45 ksi)

• Yield strength ~240–276 MPa (35–40 ksi)

• Elongation ~8–10% — reduced ductility shop.machinemfg.com+1en.m.wikipedia.org+1

• Hardness ~95 HB (~107 HV) shop.machinemfg.com+5mfgproto.com+5modulusmetal.com+5

Ideal For:

• High-performance engineering applications

• Examples: Aircraft structures, bicycle frames, automotive chassis (e.g., 6061-T6)

📊 Comparison at a Glance

🛠️ Practical Tips for Fabricators & Distributors

• Choose T4 when expecting further machining, bending, or welding.

• Use T5 if extruded shapes don’t require additional forming.

• Pick T6 for maximum strength—even though it has lower formability.

• Design note: T6’s lower ductility (~8–10%) means tight bends require careful planning to prevent cracking shop.machinemfg.com+12en.m.wikipedia.org+12shop.machinemfg.com+12en.wikipedia.org+15mechanical-engineering.com+15dekmake.com+15amspec-inc.com+1dekmake.com+1shop.machinemfg.comdekmake.com+3es.wikipedia.org+3shop.machinemfg.com+3dekmake.com+2en.wikipedia.org+2aludepot.com+2dekmake.com.

• Weld caution: T6 loses temper in weld zones — plan for post-weld heat treatment or design around T4/T5 .

🎯 Final Takeaways

• T4 delivers good ductility & formability — great for bending and welding.

• T5 fits well for extrusions needing stronger performance with no further forming.

• T6 ensures peak strength and wear resistance — ideal for structural, high-load applications.

• Matching the right temper ensures material performance, cost efficiency, and fabrication success.

🤝 Need Help Selecting Aluminum for Your Project?

Whether you’re specifying aluminum plate for structural components, extrusion shapes, or custom parts, we can help:

• Select the proper temper for strength vs. formability

• Ensure welding or bending processes align with alloy properties

• Optimize material cost and performance