Nano Tungsten--Zirconium Carbide Alloy

Because of its high melting point and high high temperature mechanical properties, tungsten metal is widely used in high temperature components, lighting, national defense and other fields. Besides, tungsten metal has the advantages of low thermal expansion coefficient and anti-sputtering. It is the most promising candidate wall material for fusion reactor. However, tungsten has some shortcomings, such as low temperature brittleness and recrystallization brittleness, which lead to brittleness and difficult to process and shape, and affect its application.

In order to improve the strength and toughness of tungsten metal, some attempts and efforts have been made. For example, adding high melting point second phase particles in tungsten, such as titanium carbide, zirconium carbide, lanthanum oxide and yttrium oxide, can play the role of dispersion strengthening and refinement of tungsten grains. It can improve the high temperature strength and recrystallization temperature of tungsten, but reduce the toughness of tungsten.

Among many attempts, some scholars have proposed a preparation method of nano-tungsten-zirconium carbide alloy, which includes the following steps:

1) Mixing steps, including wet mixing and dry mixing:
According to the proportion of 98.0%-99.8%:0.2%-2.0% by weight, tungsten metal powder and zirconium carbide powder are mixed evenly and the mixture is obtained. Among them, the particle size of tungsten metal powder is less than 5 micron, and the purity of zirconium carbide powder is better than 99.5%. The particle size of zirconium carbide powder is less than 300 nm, and the purity of zirconium carbide powder is better than 98%. Among them, ball mill, mixer or grinding can be used for powder mixing. It is preferable to use wet method in argon, nitrogen, vacuum less than 10 Pa or alcohol medium.

2) Direct hot pressing sintering process:
Hot pressing sintering at 1600 - 2300 ℃

3) Processing steps:
In step 2, nano tungsten-zirconium carbide alloy was prepared by thermoplastic deformation of sintered tungsten block at 800-1600℃.

The nano tungsten-zirconium carbide alloy has good mechanical properties and high temperature stability, and the zirconium carbide nanoparticles can be uniformly distributed inside the tungsten crystal grains, thereby avoiding stress concentration and embrittlement of coarse particles at the tungsten grains, and can pass the nails. The positional error, the strength and the high temperature performance are ensured, and the toughness is ensured, so that the ductile-brittle transition temperature of the alloy is greatly reduced, and it is expected to be applied in high temperature parts, aerospace devices, high temperature resistant containers and fusion reactor wall materials.

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