The invention relates to ultra-fine crystal tantalum material and a preparation method thereof. The grain size of the ultra-fine grain Ta material is less than or equal to 3μm; Its ultimate strength is greater than or equal to 410MPa, yield strength is greater than or equal to 300MPa. The preparation method is as follows: the tantalum source is melted by electron beam, the ingot is coated in a protective atmosphere after casting. Three-dimensional hot forging blank, blank total deformation 65 75%, blank temperature 1150 1250 deG C; After the billet, removing the sheath and low high temperature cross rolling; Ultrafine Ta material was obtained. The Ta band prepared by the invention has the advantages of simple process, uniform grain size and very fine, so that it has favorable strength, plasticity and toughness. The ultra-fine crystal Ta belt is designed and prepared for the preparation of electronics, metallurgy, iron and steel, chemical industry, cemented carbide, atomic energy, superconducting technology, automotive electronics, aerospace, medical and health and scientific research and other high-tech fields.
In order to meet the needs of deep processing, higher requirements are put forward for the grain size and anisotropy of tantalum. The smaller the grain size and anisotropy, the better. Deep plastic deformation technology is the main process for preparing ultrafine crystallized metal, including: Constant diameter angular extrusion, high pressure rotation, folding, wrinkle-pressing and hourglass extrusion, etc. The principle is that through the pass plastic deformation, the grain inside the material repeatedly mutual compression and shear strain, in this repeated compression and shear action of the grain is chopped, gradually refined, combined with the appropriate heat treatment process to control the temperature and speed of metal recrystallization, and finally get ultrafine grain or nano size grain. The following is a brief introduction to various deep plastic deformation techniques:
Equal-diameter angular extrusion: a metal forming process in which large plastic deformation of bulk materials is achieved by pure shear. Specimen vertically into the mold cavity, and then from the horizontal cavity extrusion, extrusion process, so as to complete a passes equal channel angular extrusion without changing the material under the condition of cross-sectional area and cross section shape, only after several deformation produced by the shear should be completed in a variable is equivalent to normal stress under the action of 100:1 or 1000:1 the accumulation of pressure ratio should be variable.
High pressure rotation: its working principle is the sample in high pressure, high-speed rotation of the punch generated by the friction relay and shear force under the joint action, the system of ultrafine crystal.
Hourglass extrusion method: the block material is repeatedly extruded and processed in an equal diameter mold, so that the material can obtain a large cumulative deformation, and the grain is gradually refined, so as to obtain ultrafine crystal material.
