The most widely used extrusion alloys in the 6000 series require controlled temperature treatment that starts with solution heat treatment, which is applied at the extrusion stage.
The ingot is heated to just below the established temperature for each ingot, after which the surplus heat and “stirring” obtained by re-shaping spreads Magnesium Silicides evenly through the extruded material.
To avoid concretion of Mg-Si, the material requires rapid cooling immediately after the extrusion stage. This is to prepare the material for subsequent precipitation hardening.
In order to achieve the desired final material durability, hardenable alloys must be subject to controlled temperatures and times in accordance with a specially adapted schedule for each type of alloy and desired final durability.
In general terms, the following applies:
Pressing temperature elapse diagram (from Hydro Aluminium datasheet)
The heating phase is relatively similar for all alloys, with a small variation in solution temperature, whilst the cooling phase is time-critical.