Patent DE-102012006952-A1 (DE)
Title: Creation of ultrafine-granular or nano-crystalline microstructure adjacent to workpiece surface, by subjecting workpiece in region of portion of surface of high deformation under change in directions of material flow adjacent to surface
Inventor: ZACHAEUS RENE
IPC: C21D7/04
Filed: 2012-04-04
Abstract: The method comprises subjecting a workpiece in a region of a portion of a workpiece surface of a transforming high deformation under change in directions of a material flow or direction of deformation adjacent to the workpiece surface. The high deformation of only small material volumes in an edge area of the workpiece in relation to the workpiece cross-section is 1/3 of a cross-section volume of the workpiece. A change in geometry of the workpiece such as reduction in diameter takes place in connection with a structural change of deformation. The method comprises subjecting a workpiece in a region of a portion of a workpiece surface of a high deformation under change in directions of a material flow or direction of deformation adjacent to the workpiece surface. The high deformation of only small material volumes in an edge area of the workpiece in relation to a workpiece cross-section is 1/3 of a cross-section volume of the workpiece. A change in geometry of the workpiece such as reduction in diameter takes place in connection with a structural change of deformation. The method is carried out by a grading die having a grading press configuration provided with the portion for partial deformation of a high superficial outer layer of the workpiece. The workpiece forms a semi-finished product, which is pressed in the form of full extrusion molding by a grading process tool such as the grading die under a cross-section reduction and at the same time a grading press with the change in direction and the direction of flow of the workpiece in a part of an outer layer area (2) of the workpiece is effected under a grading press structure of an inner and/or an outer geometry of the grading pressing tool such as the grading press die. The high deformation of the outer layer area of the workpiece is performed without any change in cross-section between the workpiece cross-section at the input of the grading pressing tool and the output of the grading pressing tool. The workpiece is pressed by an upstream-side first stamper through the grading die, and is pressurized by a backstop as a downstream-side counter stamper, a reduction die or a portion of the reduced cross-section of the grading die in one- or multi-axis tensile state. A thickness of the outer layer area of the high deformation is 5-15% of a diameter of the workpiece. The workpiece is further pressed with a grading profile by the grading die. A flow transition is provided between a coarse-grained structure in an inner side of the workpiece and an ultrafine or nano-crystalline structure in the outer layer area of the workpiece. The workpiece is transformed with an outer layer having the ultrafine or nanocrystalline structure in connection with the full extrusion molding. An independent claim is included for a device for the creation of an ultrafine-granular or nano-crystalline microstructure adjacent to a surface of a workpiece.