How Do T5 and T6 Tempers Differ in Aluminum Profile Mechanical Properties?

A sourcing engineer receives two shipments of 6061 Aluminum Profiles for a CNC machining project. The purchase order specifies 6061-T6. The first supplier delivers profiles with a mill certificate marked T6. The second supplier delivers profiles marked T5, with a note that T5 is "equivalent" for this application. The engineer checks the hardness of both batches with a portable hardness tester. The T6 batch reads 95 to 100 HB. The T5 batch reads 75 to 80 HB. The engineer rejects the T5 batch because the lower hardness will cause the part to deflect during machining and will not meet the drawing's strength requirement. The difference between T5 and T6 is not a labeling issue. It is a difference in the cooling process after extrusion, which changes the mechanical properties of the profile. This guide explains the difference.

1. What Is the Process Difference Between T5 and T6 Tempers?

The temper designation describes the heat treatment and mechanical working that the Aluminum Profiles undergo after extrusion. The T5 and T6 tempers both involve solution heat treatment at the extrusion press, followed by cooling and artificial aging. The critical difference is the cooling method. In the T5 temper, the profile is cooled by air or by a controlled water mist after extrusion. The cooling rate is moderate. In the T6 temper, the profile is cooled by water quenching or by a high-intensity water spray. The cooling rate is rapid. The rapid cooling in T6 retains more alloying elements in solid solution, which allows a higher strength to be achieved during artificial aging. The table below shows the process steps for each temper.

In our factory, we produce Aluminum Profiles in both T5 and T6 tempers. The choice of temper is determined by the customer's application requirements. We provide a mill certificate for each batch that shows the temper, the chemical composition, and the mechanical properties. Ningbo Gangtong Zheli Fasteners Co.,Ltd. has been supplying aluminum profiles for over 12 years.

2. How Do the Mechanical Properties of T5 and T6 Compare?

The mechanical properties of T5 and T6 Aluminum Profiles differ in yield strength, tensile strength, and hardness. The T6 temper has higher values for all three properties because the rapid cooling retains more alloying elements in solution. The table below shows the minimum mechanical properties for 6061 and 6063 alloys in the T5 and T6 tempers, according to ASTM B221.

3. When Should You Choose T5 Instead of T6?

T5 is not a lower-quality version of T6. It is a different temper with different characteristics. T5 is preferred in three situations. The first is when the profile has a complex cross-section with thin walls. The rapid quenching of T6 can cause distortion in complex profiles. The moderate cooling of T5 reduces the risk of distortion. The second is when the profile will be bent or formed after extrusion. The lower strength and higher elongation of T5 make it easier to form without cracking. The third is when the surface finish is critical. The rapid quenching of T6 can cause surface defects such as quench marks. The table below shows the recommended temper for different applications.

In our factory, we help customers select the right temper for their application. We ask for the profile drawing, the intended use, and the required mechanical properties. We then recommend T5 or T6 based on the trade-off between strength, formability, and surface finish. Ningbo Gangtong Zheli Fasteners Co.,Ltd. provides temper selection guidance for all of our aluminum profile customers.

4. How Should Incoming Inspection Verify the Temper?

The incoming inspection should verify three things: the mill certificate, the hardness, and the dimensional accuracy. The mill certificate should state the temper and the mechanical properties. The hardness should be measured with a portable hardness tester at three points along the profile. The dimensional accuracy should be checked against the drawing. The table below shows the inspection criteria for T5 and T6 profiles.

In our factory, we perform a hardness test on every batch of Aluminum Profiles before shipment. We also provide a certificate of analysis that includes the temper, the hardness, and the mechanical properties. Ningbo Gangtong Zheli Fasteners Co.,Ltd. recommends that customers perform their own incoming inspection to verify that the material meets the purchase order specification.

Summary for Sourcing Engineers and Designers

The difference between T5 and T6 tempers in Aluminum Profiles is the cooling rate after extrusion. T6 uses rapid quenching, which produces higher strength and hardness. T5 uses moderate cooling, which produces lower strength but better formability and surface finish. The choice between T5 and T6 depends on the application requirements. Structural and machined parts usually require T6. Complex profiles, bent parts, and architectural trim usually require T5. The incoming inspection should verify the temper by checking the mill certificate and measuring the hardness. Ningbo Gangtong Zheli Fasteners Co.,Ltd. has been supplying aluminum profiles for over 12 years and provides full temper selection and verification support for our customers.

Ningbo Gangtong Zheli Fasteners Co.,Ltd. supplies Aluminum Profiles in 6061 and 6063 alloys, in T5 and T6 tempers, with mill certificates and hardness test reports. We provide temper selection guidance and incoming inspection support for all of our products.