Can Both 6061 and 6063 Aluminum Be Heat Treated?
Yes. 6061 and 6063 are both members of the 6xxx (Al-Mg-Si) alloy family, which is specifically designed for heat treatment. When a project specification asks for a T5 or T6 temper, the alloy has been solution heat treated, quenched, and aged to develop its strength. The practical difference between the two alloys is not whether they can be heat treated, but how much mechanical strength each one gains from the process and which surface and fabrication properties matter most to your application.
What Heat Treatment Does to 6xxx Alloys
Heat treatment of Al-Mg-Si alloys follows the same basic route for both grades. The alloy is heated to around 520-530 °C to dissolve the magnesium and silicon into solid solution, quenched rapidly to freeze that solution, and then artificially aged at roughly 175-180 °C. The T6 temper means solution heat treated plus artificially aged to peak strength; the T5 temper is aged directly after cooling from an elevated-temperature shaping process such as extrusion, without a separate solutionizing step. Because both 6061 and 6063 respond to this cycle, you will find both alloys supplied in T5 and T6 tempers across ASTM B221, EN 755-2, JIS H4100 and GB/T 6892 standards.
6061 Aluminum: Strength-Focused and Structural
6061 contains approximately 0.8-1.2% magnesium and 0.4-0.8% silicon, with small additions of copper and chromium. In the T6 temper it delivers a minimum tensile strength of about 290 MPa and a minimum yield strength of about 241 MPa for sheet and plate (ASTM B209), with higher minimums for thicker plate. That makes 6061-T6 the default choice for load-bearing frames, machinery, truck bodies, marine fittings, and structural assemblies where fatigue resistance and weldability are required.
6061 Mechanical Properties (T6, typical minimums)
Tensile strength: 290 MPa (42 ksi)
Yield strength (0.2% offset): 241 MPa (35 ksi)
Elongation: 8-12% depending on thickness
Hardness: about 95 HBW
6063 Aluminum: Architectural and Appearance-Focused
6063 uses a leaner Mg-Si balance (about 0.45-0.9% magnesium, 0.2-0.6% silicon), which gives it outstanding extrudability and a smooth, uniform surface that anodizes to a bright, even finish. In the T6 temper its minimum tensile strength is about 205 MPa with a minimum yield strength of about 170 MPa for typical extruded sections (ASTM B221, EN 755-2). It is weaker than 6061, but its corrosion resistance, surface quality, and ability to form complex hollow cross-sections make it the standard for window frames, curtain walls, handrails, and decorative profiles.
6061 vs 6063: Side-by-Side Comparison
| Feature | 6061-T6 | 6063-T6 |
|---|---|---|
| Minimum tensile strength | 290 MPa | 205 MPa |
| Minimum yield strength | 241 MPa | 170 MPa |
| Corrosion resistance | Good | Very good |
| Anodizing / surface finish | Good | Excellent |
| Formability / extrudability | Good | Excellent |
| Best suited for | Structural, mechanical parts | Architectural, aesthetic profiles |
How to Choose Between 6061 and 6063
If your part carries load, faces vibration, or must meet structural codes, choose 6061-T6. If your product is visible, anodized, or exposed to outdoor architectural conditions, 6063-T6 usually delivers a better finish at a lower fabrication cost. For mixed requirements, many buyers pair 6061-T6 structural members with 6063-T6 extrusions in the same assembly, since both alloys weld readily and can be finished to a matching appearance.
Frequently Asked Questions
Can both 6061 and 6063 aluminum be heat treated? Yes, both are heat-treatable Al-Mg-Si alloys and are commonly supplied in T5 and T6 tempers. The main difference is that 6061 gains significantly more mechanical strength from the T6 cycle.
What is the difference between T5 and T6? T6 is solution heat treated, quenched, and artificially aged, which gives peak strength. T5 is artificially aged directly after hot forming such as extrusion, skipping the separate solutionizing step; it costs less but produces lower strength.
Is 6061 stronger than 6063? Yes, in comparable tempers 6061 is roughly 40% stronger. 6063 is selected instead for surface quality, extrudability, and corrosion performance.
Why is 6063 preferred for anodizing? Its low alloy content and uniform grain structure produce a bright, clear anodic film with consistent color, which is why architectural specifiers choose it for visible profiles.
Can 6061-T6 and 6063-T6 be welded? Both weld well with 4043 or 5356 filler wire. Note that welding locally anneals the heat-affected zone, so post-weld heat treatment is needed if full T6 properties must be restored in the joint area.
Which alloy is better for outdoor handrails and fencing? 6063-T6 is the typical first choice for handrails because of its anodizing quality and corrosion resistance; 6061-T6 is chosen where higher mechanical loads or impact resistance are expected. Unsure which alloy fits your application? Our team supplies both 6061 and 6063 in sheet, plate, and extruded profiles with full mill certificates.
