Method of forming a component of complex shape from sheet material
Method of forming a component of complex shape from an Al-alloy sheet or a Mg-alloy sheet. The method includes the steps of: a) heating the sheet to a temperature below the solution heat treatment (SHT) temperature for the alloy; b) forming the heated sheet between heated dies into or towards the complex shape; c) heating the sheet to at least its SHT temperature and substantially maintaining that temperature until SHT has been completed; and d) quenching the solution heat treated sheet between cold dies and at the same time completing the forming into the complex shape or maintaining that shape.
1. A method of forming a sheet component of multi-dimensional shape from an Al-alloy or Mg-alloy sheet, the method comprising the following sequence of steps in order:
(a) heating an Al-alloy or Mg-alloy sheet to a temperature below the solution heat treatment (SHT) temperature for the alloy;
(b) forming the heated sheet between heated dies into a shape whilst maintaining the sheet at a temperature below the solution heat treatment (SHT) temperature for the alloy;
(c) solution heat treating the sheet by heating the sheet to its SHT temperature and substantially maintaining that temperature until SHT has been completed; and
(d) quenching the solution heat treated sheet between cold dies and at the same time completing the formation of the sheet into a finished shape, wherein step (a) includes either:
heating the Al-alloy sheet to a temperature between 430° C. and 493° C.; or
heating the Mg-alloy sheet to a temperature between 400° C. and 480° C.
2. The method according to claim 1 , wherein step (a) includes heating the sheet to a temperature below that at which inclusions in the alloy melt.
3. The method according to claim 1 , wherein step (a) includes heating the sheet to a temperature at which formability of the alloy is greater than that at the SHT temperature.
4. The method according to claim 1 , wherein step (a) includes heating the sheet to a temperature at which formability of the alloy is substantially maximized.
5. The method according to claim 1 , wherein step (b) includes forming the sheet in hot dies arranged to minimize heat loss from the sheet.
6. The method according to claim 1 , wherein, in step (b), the dies are at substantially the same temperature as that to which the sheet is heated in step (a).
7. The method according to claim 1 , wherein, during step (b), the temperature of the dies is kept substantially constant.
8. The method according to claim 1 , wherein the dies of step (b) comprise one or more heating elements.
9. The method according to claim 1 , wherein the dies of step (d) are cooled.
10. The method according to claim 1 , wherein the method includes the subsequent step of (e) artificially ageing the resulting component.
11. The method according to claim 1 , wherein the sheet is an AZ31 or AZ91 Mg-alloy.
12. The method according to claim 1 , wherein the sheet is a 2XXX series Al-alloy.
13. The method according to claim 12 , wherein the 2XXX series Al-alloy is AA2024.
14. The method according to claim 9 , wherein the dies of step (d) comprise one or more cooling elements, cooling channels, or both.