| CPC B21D 22/022 (2013.01) [C22F 1/06 (2013.01)] | 5 Claims |
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1. A method for preparing a rare earth magnesium alloy with ingots by severe plastic deformation, comprising:
S1: providing a cylindrical magnesium alloy bar;
S2: homogenizing the cylindrical magnesium alloy bar to form a cylinder blank;
S3: heating the cylinder blank to a forming temperature and holding the forming temperature, and heating a preparation mold above an experimental temperature and holding the experimental temperature for half an hour, wherein the preparation mold comprises a male mold installed on an upper workbench of a press machine, a female mold installed on a lower workbench of the press machine, a recoverable discard block and a back pressure plate connected with a pushing cylinder of the press machine, the female mold is provided with an upper mold cavity and a lower mold cavity, and an upper part of the upper mold cavity is configured for placing blanks, the recoverable discard block and the male mold, and a lower part of the upper mold cavity is inclined inward to form an extrusion deformation area communicated with the lower mold cavity; the recoverable discard block is separated between the cylinder blank and the male mold, the recoverable discard block is made of deformable material, and the recoverable discard block is configured to be deformed and filled in an extrusion deformation area and restored through deformation; an upper part of the back pressure plate is fitted in the lower mold cavity, so that a molding cavity is formed between the upper part of the back pressure plate and the lower mold cavity, and an upper surface of the back pressure plate is raised in a middle;
S4: installing the preparation mold after preheating and heat preservation on a pressing machine, and evenly spraying organic graphite lubricant on the male mold and the female mold;
S6: putting the cylinder blank after homogenization and heat treatment into the upper mold cavity;
S7: placing the recoverable discard block above the cylinder blank;
S8: adjusting a height of the back pressure plate to an outlet of the extrusion deformation area by an upward movement of the pushing cylinder in an initial stage of extrusion forming; wherein the pressing machine drives the male mold to move downward and gradually extrudes the cylinder blank into the extrusion deformation area; a bottom of the cylinder blank slowly deforms, contracts and fills the extrusion deformation area; as the male mold continues to move downward, the bottom of the cylinder blank contacts the upper surface of the back pressure plate; when a contact width is close to a size of an extruded part, the back pressure plate starts its downward return with the male mold; after a stroke of the male mold is completed, the recoverable discard block fills the extrusion deformation area, and an upsetting deformation is completed; in this process, the back pressure plate always gives an upward back pressure to the cylinder blank;
S9: driving the back pressure plate downward to remove from a lower part of the lower mold cavity by the pushing cylinder, wherein the recoverable discard block has been broken; taking out the cylinder blank after extruded and a powder of the recoverable discard block from the lower part of the lower mold cavity, and restoring the powder into a plate shape for use next time.
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