Method of quenching alloy sheet to minimize distortion

A method of producing a sheet article or other elongated product of solution heat treated aluminum alloy substantially free of permanent thermal distortion. The method involves subjecting an article made of a heat-treatable aluminum alloy to a solution heat treatment, cooling the article in a gas from the solutionizing temperature to an upper critical temperature below which precipitation of second phase particles of the alloy may occur, further cooling the article in a gas/liquid from the upper temperature to a lower critical temperature below which precipitation of the components may no longer occur, and optionally additionally cooling the article to a temperature below the lower critical temperature. The cooling of the article in the gas is carried out at a rate of cooling at which the yield strength of the article remains high enough to resist permanent deformation caused by thermal stress generated within the article by the cooling.