The plasticity of tungsten alloy refers to the property that an object is subjected to a force exceeding its elastic limit, showing continuous and permanent deformation. It refers to the ability of the material to withstand plastic deformation without breaking. It is usually measured by a universal tensile strength testing machine. The tensile testing machine is a new generation of mechanical testing equipment that integrates computer control, automatic measurement, data acquisition, screen display, and test result processing. It uses the host machine under the oil cylinder as the platform, and is equipped with precision oil pumps, electro-hydraulic servo valves, and PC servos. controller.
The plasticity of tungsten alloy is not constant and will be affected by many factors, such as material composition, raw material ratio, microstructure, process parameters, post-processing and working environment, etc. Generally speaking, the greater the elongation or the higher the reduction of area, the better the plasticity of the alloy material; conversely, the smaller the elongation or the lower the reduction of area, the worse the plasticity of the alloy material.
1. Material composition
The composition of tungsten-based alloys includes hard phase tungsten, binder phase nickel, iron or copper, etc. When the binder phase is different, the plasticity index of the tungsten-based alloy is also different. Studies have shown that the elongation of 90W7Ni3Fe is 18%-29%, and the elongation of 90W6Ni4Cu is about 6%.
2. Raw material ratio
When the material composition and application are the same, and the ratio of raw materials is within a certain range, the greater the binder phase content or the less tungsten content, the better the plasticity of the tungsten alloy; on the contrary, the less the binder phase content or the higher the tungsten content, The plasticity of tungsten alloy is worse. Studies have shown that the elongation rate of 90W7Ni3Fe is 18%-29%, that of 91W6Ni3Fe is 17%-27%, that of 92W5Ni3Fe is 16%-26%, that of 93W4Ni3Fe is 16%-24%, and that of 95W3Ni2Fe is 10%-22%. 97W2Ni1Fe is 6%-13%.
3. Microstructure
In the case of the same material composition and other factors, the finer the tungsten particles, the more uniform the particle size distribution, and the more uniform the binder phase distribution, the better the plasticity of the tungsten-based alloy.
4. Process parameters
The production process of tungsten alloy mainly includes powder metallurgy and injection molding technology. Among them, the process of powder metallurgy method is: mixing → pressing → pre-firing → liquid phase sintering → heat treatment → blank cutting → cold processing → actual effect → final cutting → finished product. The process of injection molding technology is: mixed feeding → granulation → injection → degreasing and pre-sintering → sintering → heat treatment → finished product.
However, in both processes, the sintering temperature has a great influence on the plasticity of the tungsten alloy. Its plasticity will first increase and then decrease with the increase of sintering temperature.
5. Post-processing
The plasticity of the post-treated tungsten alloy is significantly improved. Post-treatment mainly includes heat treatment and deformation strengthening. Among them, heat treatment methods mainly include solution quenching treatment, vacuum or inert atmosphere dehydrogenation treatment, cyclic heat treatment, etc.; deformation strengthening mainly includes forging, hot extrusion, hot rolling and forging composite deformation process.
