Quench sensitivity (Topic: 10044)

Different alloys have different sensitivity regarding quenching rate. Generally the sensitivity increases with the concentration of alloying elements and with density of nucleation sites for the precipitates. Such nucleation sites can for instance be AlMnSi dispersoids in AW-6082 alloys.

The alloys should, according to their quench sensitivity, be cooled quickly through a critical temperature interval, 500ñ250°C, to avoid precipitation. This means that cooling with forced air on the run out table may be sufficient for AW-6060, while AW-6082 normally needs water cooling. The resulting strength of the alloys after ageing is strongly influenced by the quenching rate (see illustration) and an alloy with a higher strength potential can get the lowest resulting strength compared to a lower alloyed alloy if it is cooled too slowly.