Effects of Ball-milling on the microstructure and properties of W Ti alloy gasket

Abstract W Ti alloy, which is a candidate of the gasket material used for the neutron high pressure diffraction, was proposed and fabricated by the powder metallurgy method in this paper. The laser particle size analyzer, scanning electron microscope, and transmission electron microscope were used to study the effects of milling time on the particle size distribution and the microstructure. The results show that with the extension of milling time, the particle size of the milled powders decreases, and the grain size of the sintered alloys also decreases. However, the oxygen content increases, and the αTi phase gradually appears and its amount increases with the increase of the milling time. The microstructure is composed of the W-rich (βTi,W) phase, the αTi phase and the eutectic phase before the milling time of 2 h, and after that the eutectic phase disappears. Oxygen coming from the milling gets rich in titanium so that it makes more and stable αTi phase. This is because, with the extension of milling time, the oxygen content is so high that the αTi phase can be very stable and the diffusion of W into Ti at the high temperature is suppressed. Moreover after 0.5 h ball milling, the maximum strength of the alloy is 3323 MPa due to the uniform microstructure.