Thick-section metal forming via friction stir processing
View Patent ↗Friction stir processing (FSP) modifies the surface microstructure of metals so that thick-section metal workpieces can be bent over large angles without formation of surface cracks. A thick 2519-T8 aluminum plate (25.4 mm thick and 50.8 mm wide) was friction stir processed across the pre-tensile surface to a depth of 6.3 mm, and was then bent at room temperature over a punch with radius 38.1 mm into a v-shaped die to an 80° bend angle. Whereas unprocessed workpieces of this type exhibited surface cracking at 31° bend angle and failed at 40° bend angle, no cracking was evident for the friction stir processed workpiece up to 80° bend angle.
1. A method for forming a metallic workpiece, comprising the steps of:
friction stir processing a predetermined area of a pre-tensile surface of the workpiece to a depth of up to 50% of the maximum thickness of the workpiece; and
forming the workpiece such that at least a portion of the predetermined area undergoes tensile strain in a bend area.
2. The method of claim 1 , wherein the metallic workpiece comprises a metal selected from the group consisting of aluminum, titanium, nickel, copper, iron, and alloys thereof.
3. The method of claim 1 , wherein the metallic workpiece is a metal plate.
4. The method of claim 1 , wherein said step of friction stir processing is performed using a FSP tool rotating at a rate between 150 and 2000 rotations per minute.
5. The method of claim 1 , wherein said step of friction stir processing is performed using a FSP tool moved along the workpiece surface at a rate of 50 to 7000 mm/minute.
6. The method of claim 1 , wherein the predetermined area of the pre-tensile surface of the workpiece substantially coincides with the bend area.
7. A method for bending a metal workpiece, comprising the steps of:
friction stir processing a predetermined area of a pre-tensile surface of the workpiece to a depth of up to 50% of the maximum thickness of the workpiece; and
bending the workpiece such that at least a portion of the predetermined area undergoes tensile strain in a bend area.
8. The method of claim 7 , wherein the metallic workpiece comprises a metal selected from the group consisting of aluminum, titanium, nickel, copper, iron, and alloys thereof.
9. The method of claim 7 , wherein the metallic workpiece is a metal plate.
10. The method of claim 7 , wherein said step of friction stir processing is performed using a FSP tool rotating at a rate between 150 and 2000 rotations per minute.
11. The method of claim 7 , wherein said step of friction stir processing is performed using a FSP tool moved along the workpiece surface at a rate of 50 to 7000 mm/minute.
12. The method of claim 7 , wherein the predetermined area of the pre-tensile surface of the workpiece substantially coincides with the bend area.
13. A method for forming an aluminum workpiece, comprising the steps of:
friction stir processing a predetermined area of a pre-tensile surface of the aluminum workpiece to a depth of up to 50% of the maximum thickness of the workpiece; and
forming the aluminum workpiece such that at least a portion of the predetermined area undergoes tensile strain in a bend area.
14. A method for bending an aluminum workpiece, comprising the steps of:
friction stir processing a predetermined area of a pre-tensile surface of the aluminum workpiece to a depth of up to 50% of the maximum thickness of the workpiece; and
bending the aluminum workpiece such that at least a portion of the predetermined area undergoes tensile strain in a bend area.