Microstructure and properties of TiN-reinforced W–Ti alloys prepared by spark plasma sintering

• W–Ti/TiN alloys were fabricated by spark plasma sintering of milled TiH2 and micro-sized W powders.
• As the Ti content increased from 0 wt.% to 4 wt.%, the grain size of alloy was refined.
• Ti/TiN solution was observed, thereby implying N diffused into other Ti lattices during sintering.

In this investigation, TiN-reinforced W–Ti alloys were fabricated through spark plasma sintering of milled TiH2 powders and micro-sized W powders. TiH2 powder was used to prevent oxidation during milling. X-ray, FESEM, and TEM analyses were adopted to study the microstructures of the powders and sintered samples. As the Ti content increased from 0 wt.% to 4 wt.%, the grain size of the resultant alloy was significantly refined and a more transgranular fracture was observed. The micro-hardness of the alloys significantly increased with addition of up to 4 wt.% Ti and then decreased with further Ti addition. A Ti/TiN solution in which N probably diffused into other Ti lattices during the sintering process was detected by TEM. The effect of He+ irradiation was investigated in this work. Samples with 0 and 8 wt.% Ti were exposed to a He+ ion beam (He+ ion beam flux, 1.2 × 1022 ions/m2·s; beam energy, 50 eV) for 1 h through the Large-Power Materials Irradiation Experiment System. Results revealed peeling off of TiN particles after irradiation as well as the presence of pores that could induce erosion in the grain boundaries. The sample with 8 wt.% Ti showed no secondary-phase peeling, and only a small density of blisters were found in its W-grain and Ti-rich phases.

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