Preparation method for metal material

A preparation method for a metal material, comprising:

• horizontally placing a to-be-prepared metal material between wavy surfaces of a female die and a male die, wherein the female die and the male die respectively include a plurality of first mountain-shaped features having the wavy surfaces, and the plurality of first mountain-shaped features are substantially identical;
• starting a press machine which is connected to the male die, and pressing the metal material through the male die, so that the metal material makes complete contact with the male die and the female die;
• ejecting the pressed metal material, horizontally overturning the metal material, and then placing the metal material between the wavy surfaces of the female die and the male die, wherein the pressed metal material has a plurality of second mountain-shaped features;
• repeatedly performing the pressing process, ejecting a re-pressed metal material, horizontally overturning the re-pressed metal material again, then, placing the re-pressed metal material between the wavy surfaces of the female die and the male die, and repeatedly performing the pressing and overturning processes until accumulated strain of the metal material meets a requirement;
• and
• taking out the metal material after the deformed metal material is flattened by a plane die.