Abstract: The invention relates to a method of manufacturing an AIMgSc-series aluminium alloy product, the method comprising the step of cooling said AIMgSc-series aluminium alloy product from a final annealing temperature to below 150° C., wherein the cooling in a first temperature range of about 250° C. to about 200° C. is at an equivalent time of more than 4 hours, and wherein the cooling in a second temperature range from about 200° C. to about 150° C. is at an equivalent time of more than 0.2 hours, and wherein the equivalent time (t(eq)) is defined as (I) wherein T (in degrees Kelvin) indicates the temperature of the heat treatment, which changes over the time t (in hours) and Tref (in degrees Kelvin) is the reference temperature selected at 473K.