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Aging harden aluminum profiles

The aging process is an extended heat treatment process. This process strengthens the aluminum alloys. The aluminum profiles are placed in an oven at very high temperatures to increase the rate at which the properties of the aluminum change after the extrusion process. Typically, the chemical properties of freshly cast and extruded aluminum will naturally change slowly at room temperature.

The process of aging in an oven at a high temperature speeds up this change to give the aluminum surface resistance to corrosion and weathering. The aging process enhances quality and increases accuracy for profiles that have close tolerance specifications. It also helps to produce machine-ready profiles at a faster rate.

An important aspect of the hardening process is called precipitation hardening. During this process, heat imparts strength to the metals and their alloys. The tensile strength is also increased. The precipitates formed stops the movement of defects in the metal crystal lattice. For this to happen, the metal has to be kept at a high temperature for several hours for this type of age hardening to take place.

During the process of age hardening, the metal is treated with a solution at a high temperature. Then the solution is cooled rapidly. This prevents diffusion. Then the supersaturated solution is heated up to a temperature that induces precipitation. The heat treatment with the solution and the quick cooling gives a stable material by stopping the development of any defects in the metal lattice.

Precipitation hardening is generally done inside a vacuum, in an inert atmosphere in temperatures that range between 900 and 1150 degrees Fahrenheit. The process goes on for at least four hours or more depending on the type of aluminum alloy and the specifications for the profile.

Just as it is with tempering and other forms of metal surface treatment, it is important to strike a balance between the increase in hardness and the loss of ductility. Also, it is vital to avoid over-aging the aluminum profile material by hardening it for too long. This could result in a reduction in hardness.

In the process of precipitation hardening, the selection of the alloying elements or precipitate is very important. It is vital to avoid adding an excessive amount of precipitate so that it remains soluble at a reasonable aging temperature. Elements used for precipitation hardening of aluminum include magnesium and copper. These usually make 10% or less of the total metal composition. Some other components may also be used for corrosion resistance or grain refinement.

It is also important to note that the strength of the aluminum profiles can be increased by adjusting the aging process. Typically, using lower temperatures for a longer time will increase the formation of a stronger metal matrix and reduce the amount of dislocation while the metal profile is in use. Also, using lower temperatures prevents the occurrence of over-aging since it stops the precipitate from growing too quickly thereby increasing the final strength of the profile.