What is the difference between T5 and T6 temper in aluminum plates
6-series aluminum plates are aluminum-magnesium-silicon alloys, with representative grades including 6061, 6063, and 6082. Unlike the other seven series of aluminum plates, 6-series plates are mainly in T temper, with the most common being T5 and T6. With only a single letter difference, what is the distinction between these two tempers?
Before explaining the difference between T5 and T6 states, the user must first understand the following two definitions:
Aging: The process of relieving internal stress in metal.
Quenching: Heating the metal to a certain temperature and then suddenly cooling it to achieve the required hardness. Aluminum plates of series 2, 6, and 7 can all have their strength improved through quenching.
The T5 temper refers to aluminum plates that, after being extruded from the extruder, are cooled by air to quickly lower the temperature to achieve the required hardness (Brinell hardness 8–12). The T6 temper refers to aluminum plates that, after being extruded from the extruder, are cooled by water to rapidly lower the temperature, allowing the aluminum plates to reach a higher hardness (Brinell hardness above 13.5).
The air cooling process takes a relatively long time, usually 2-3 days, which we call natural aging; while water cooling is shorter, which we call artificial aging. The main difference between T5 and T6 states lies in strength, with T6 state having higher strength than T5, while other performance aspects are similar. In terms of price, due to differences in production processes, the price per ton of T6 aluminum plate is higher than that of T5.
What is stress relief
During the production process of aluminum plates, due to heating and extrusion, the density between crystals becomes uneven, and the energy cannot be fully released, accumulating inside the aluminum plate. This energy is called internal stress. Certain users' production processes (such as heating, bending, deep drawing, and stretching) can release the internal stress of the aluminum plate, causing the plate to warp, form waves, or have an uneven surface. Therefore, it is necessary to release the internal stress of the aluminum plate beforehand.
The process of eliminating internal stress is quite simple. After the aluminum sheets come off the production line, the manufacturer adds an additional step: using a machine to stretch the aluminum sheets, which releases the energy inside them.
