May 03, 2026

Aluminum Temper T5 vs T6: Hardness and Strength Explained

In aluminum extrusion, the "Temper" defines the mechanical properties of the metal. You will often see "6063-T5" or "6061-T6" on a quotation. At Leader Aluminum, we want our clients to understand that the temper process—not just the alloy—determines if a profile will bend, snap, or hold firm under pressure.

The T5 Temper: Air Cooled Stability

T5 temper is achieved by cooling the aluminum profile immediately after it exits the extrusion die using high-velocity fans. This process is known as air quenching. Following this, the profiles are placed in an aging oven. For 6063-T5, the typical Webster hardness is between 8 and 12 HW. This temper offers the best dimensional stability and is perfect for window and door systems where extreme structural load is not the primary concern.

The T6 Temper: Water Quenched Power

T6 temper is for maximum performance. Instead of air, the aluminum is quenched with water or a specialized mist. This rapid temperature drop "locks" the molecular structure, which is then further hardened in an aging oven. A T6 profile can achieve a Webster hardness of 12 to 16+ HW. It increases the yield strength by nearly 30% compared to T5, making it essential for solar panel mounts, industrial ladders, and T-slot framing systems.

Critical Considerations

While T6 is stronger, it is also more brittle. If your project requires post-extrusion bending or complex forming, T5 is often the safer choice to avoid micro-cracks.