Closed back pressure bidirectional upsetting extrusion forming method for preparing refractory metal ultrafine grain material

Abstract

The invention discloses an enclosed-type back-pressure two-way extrusion-upsetting forming method for manufacturing refractory metal ultrafine-grained material. The forming method is based on a combined concave die forming a cross-shaped channel which is arranged in the manner that a first channel and a second channel are vertically intersected. The forming method comprises following steps: material replacement and die combination; first-pass extrusion-upsetting; pressure relief and die opening; and the step of placing a first-pass extrusion-upsetting specimen to the first channel again and repeating. Compared with the prior art, the enclosed-type back-pressure two-way extrusion-upsetting forming method for manufacturing refractory metal ultrafine-grained material has following beneficial effects: enclosed-die forging technology is introduced to severe plastic deformation technology; based on the principle of a floating concave die, double-punch extrusion-upsetting of a highly-symmetrical structure is obtained; an unbalance loading problem existing in conventional equal channel angular pressing technology is solved; die bulking failure tendency is reduced; material is in the triaxial compressive stress state; deformation capability of low-ductility refractory metal (tungsten, molybdenum and the like) is effectively improved; operation is conducted easily; high practicability is obtained; and the enclosed-type back-pressure two-way extrusion-upsetting forming method is easy to apply.

Description

technical field [0001] The invention relates to the technical field of material processing methods, in particular to a closed-type back-pressure bidirectional upsetting extrusion forming method for preparing refractory metal ultrafine-grained materials. Background technique [0002] Refractory metal materials such as tungsten and molybdenum have the highest melting point among metals, high density, high hardness, low linear expansion coefficient, slow evaporation speed, and corrosion resistance, making them have broad application prospects in various high-end engineering fields. At present, the main factors limiting its industrial application are poor plasticity, high ductile-brittle transition temperature, low-temperature brittleness, and easy oxidation. In recent years, the method of preparing ultra-fine-grained materials by using large plastic deformation technology to improve the structure and properties of materials has attracted extensive attention. A literature searc...

AI Technical Summary

Problems solved by technology

However, in the existing large plastic deformation process, the grain refinement effect of the multi-directional compression process is relatively weak, and the uniformity of the structure is low; The repeatability is poor; the size of the billet processed by the high-pressure torsion process is small, and the prospect of industrial application is uncertain

The existing large plastic deformation process is difficult to meet the requirements of modern nuclear industry, national defense and military industry for refractory metals (tungsten, molybdenum, etc.)

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