Neutron Diffraction High Pressure Cavity Gasket Material—Tungsten Titanium Alloy

Neutron diffraction usually refers to the Prague diffraction of neutrons (thermal neutrons) passing through crystalline material when the De Broglie wavelength is about 0.1 nm.

The gasket of neutron diffraction high pressure cavity is used to fix sample. At high pressure, the gasket formed by high pressure forms a metal ring, which plays a protective role on anvil surface. The sample is located in the central sample of gasket hole. The gasket prevents the rheology of the sample well. At the same time, the loading of liquid sample and pressure transmitting medium become possible. 

The early gasket material is Ti-Zr alloy, in the process of looking for alternative materials, the scientists found that the tungsten alloy has a series of excellent physical and mechanical properties, such as strength, ductility, high hardness, good toughness, low thermal expansion coefficient, thermal conductivity, good corrosion resistance and good oxidation resistance, machining and welding characteristics, so therefore, by preparation of W-Ti alloy gasket material has its unique advantages.

Prepare W-Ti alloy by powder metallurgy method. The micron grade W powder with 73.1% total mass and 26.9% micron TiH₂ powder mixed with cemented carbide ball are put into planetary high energy ball mill, and the ball material ratio is 5: 1. The ball mill was milled by adding alcohol, sealed and milled. The speed of the ball mill was 170r·min^-1, and the milling time was 22 hours. After the ball milling powder was formed by cold isostatic pressing, sintered at 1500°C for 3 hours with vacuum tungsten sintering furnace, the raw material of W-Ti alloy gasket was obtained.

In the process of planetary ball milling, small and hard W particles promote the fragmentation of coarse and brittle TiH₂ powder, which makes the size of the whole powder finer. With the increase of milling time, the distortion and crystal defects of W-TiH₂ powder increase, which provides more favorable conditions for the sintering diffusion of the alloy, and the microstructure is more compact and even and smaller.

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