Tungsten alloy is a two-phase alloy with high density (≥16.5g/cm3), also known as high-density tungsten alloy. High-density tungsten alloy is currently not only widely used in military fields such as aviation, aerospace, and weapons, but is also increasingly used in civilian industry. The preparation process of high-density tungsten alloy is:
1. Ingredient design
In high-density tungsten alloys, the tungsten content is generally 85-98wt%. In addition to W, the elements with more content in high-density tungsten alloys are Ni, Fe (Cu, etc.). When preparing high-density tungsten alloys, elements or compounds such as Mo, Ta, Re, and La are also added.
2. Flour making
The use of powders with high purity, small particle size and good uniformity will produce alloys with excellent mechanical properties. In the field of powder making, nanopowders are a hot research topic and mainly fall into the following two categories:
1) Spray drying method
The spray drying method is the first choice to prepare an original salt solution with a certain composition. The salt solution includes tungstate and metal chloride, and the solution is atomized to generate small droplets. Due to the rapid evaporation of the solvent and the rapid deposition of the solute in the small droplets, a powder crystal with uniform chemical composition is obtained.
2) Mechanical alloying method
The mechanical alloying method is to select a certain proportion of the initial tungsten alloy powder and metal balls and put them into a ball mill. Under the action of the metal balls at unequal speeds, the powder undergoes cold welding and multiple deformations, and finally obtains a finer structure and smaller composition. Uniform composite powder.
3. Forming
The more traditional tungsten alloy forming process is compression molding, and the new alternative processes are powder extrusion molding and powder injection molding. Since these two methods mix tungsten alloy powder with the forming agent and then squeeze and inject it into the molding machine, they have significant advantages in preparing parts with complex shapes. Powder extrusion molding and powder injection molding technology also have The addition of forming agent makes it have wider applicability.
4. Sintering
Because of the solid phase
The sintering method has relatively high requirements on the size of the original alloy powder. The liquid phase sintering method requires a long sintering time and can easily cause collapse and deformation. Based on the advantages and disadvantages of the two, people have proposed a two-step sintering process of solid phase sintering + liquid phase sintering. Since the deformation during the two-step sintering is smaller, the structure of the tungsten alloy obtained is more uniform, and the material properties will be greatly improved, so the two-step sintering is widely used. In addition, the newly developed microwave sintering and discharge plasma sintering technologies in recent years are also being promoted and used.
