| 摘要 |
A method for the manufacture of a sheet of an A1MgSi alloy of the AA6xxx type containing Si in an amount of 0.4 to 1.7 wt% and Mg in an amount of 0.2 to 0.9 wt%, comprises the following steps carried out in the following sequence:- (i) cold-rolling of the alloy to the final desired sheet thickness, (ii) solution heat treatment of the sheet, (iii) cooling from the solution heat treatment temperature to below 150 DEG C at a cooling rate of at least 100 DEG C/min. and further cooling to below 50 DEG C, (iv) holding the sheet below 50 DEG C for a holding time of not more than 30 minutes after the end of step (iii), (v) immediately after step (iv), heating the sheet to a predetermined holding temperature within the temperature range 165-185 DEG C, (vi) maintaining the sheet at the predetermined holding temperature for a holding time in the range 60 to 600s, before cooling again. Steps (iv) to (vi) particularly effect a preliminary ageing to prepare the sheet for a subsequent paint-bake as an automotive body part. |
