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HfC dispersion strengthened tungsten alloys were prepared by the spark plasma sintering (SPS) and an ordinary sintering followed by swaging, respectively. The HfC content is optimized as 0.5 wt% through spark plasma sintering (SPS) processing. The thermal stability, thermal conductivity and mechanical properties of swaged W-0.5 wt%HfC (WHC05) alloys were systematically investigated. Grain of swaged WHC05 has an obvious round bar shaped morphology with an average diameter of 24.5 μm and an average length of 187 μm, respectively, which keeps stability with increasing annealing temperature up to 1400 °C. The ductile-brittle transition temperature of swaged WHC05 is about 250 °C, much lower than that of SPSed WHC05 samples (∼500 °C). The ultimate tensile strength of swaged WHC05 alloys annealed at 1200 °C has no significant drops in a wide tested temperature range from 300 °C to 800 °C. The thermal conductivity of swaged WHC05 annealed at 1200 °C is up to 174 W/m·K at room temperature and always larger than 137 W/m·K from RT to 500 °C, which is much higher than that of the unannealed one and just the same with ITER grade W. [ABSTRACT FROM AUTHOR]

Abstract In this paper, high density nanocrystalline W with uniform dispersion of nanosized oxide particles was fabricated via a dissolution-precipitation process by well controlled high-energy ball milling of the raw powder materials of Y 2 O 3 , Ti and W and the subsequent spark plasma sintering (SPS). XRD and TEM analysis revealed that the Y 2 O 3 and Ti were dissolved in W matrix during the high-energy ball milling and the Y 2 Ti 2 O 7 particles were precipitated in the SPS process, resulting in the refinement in both W grains and oxide particles. The average grain size of W is 67 nm. The average size of particles in grain interior and at grain boundaries is 8.5 nm and 16.4 nm, respectively. The Vickers microhardness of such a nanostructured W alloy is as high as 1441 Hv, which is 2–3 times that of the ever reported W alloys. Such a dissolution-precipitation process offers a general pathway for manufacturing nanocrystalline refractory metals with dispersion of nanoscale oxides in a controllable manner. Highlights • A novel powder metallurgy approach to fabricate high density nanostructured tungsten based alloys. • A WYT alloy contains nanosized tungsten grains (~67 nm) and nano oxide particles (~10 nm). • An unprecedented high Vickers microhardness of ~1441 Hv has been achieved. • The refining mechanisms include molecular-level dissolution and precipitation. [ABSTRACT FROM AUTHOR]

Bulk W-0.5 wt% ZrC (WZC) plates were fabricated using tungsten powders with different powder grain sizes of 0.2 μm, 0.5 μm and 2.8 μm, respectively. The different grain sizes resulted in completely different micro-structures and mechanical properties of as-rolled WZC plates. For the tungsten plate prepared from the initial powder with grain size of 0.5 μm (0.5WZC), more excellent mechanical properties were achieved than those of plates made of powders with grain sizes of 0.2 μm (0.2WZC) and 2.8 μm (2.8WZC). In the as-rolled 0.5WZC, the ductile-brittle transition temperature is as low as 150 °C and ultimate tensile strength is as high as 932 MPa at 150 °C, respectively. Moreover, the 0.5WZC plate has the most outstanding high-temperature stability with a recrystallization temperature of 1500 °C. Micro-structure analysis indicates that the second-phase particles are uniformly distributed in the 0.5WZC, but serious particle aggregation occur in the 2.8WZC. The possible micro-mechanisms have been proposed. [ABSTRACT FROM AUTHOR]

The mechanical properties, microstructure and thermal stability of hot rolled pure W and W-0.5 wt%ZrC alloy manufactured using the same technology are systematically studied. The results of Vickers hardness and tensile tests show that the W-0.5 wt%ZrC alloy has a higher hardness, ultimate tensile strength, ductility and thermal stability compared to pure W. The recrystallization temperature of W-0.5 wt%ZrC alloy is about 1300 °C which is 100 °C higher than that of hot rolled pure W (1200 °C). The ductile to brittle transition temperature (DBTT) of W-0.5 wt%ZrC alloy is 50 °C lower than that of the rolled pure tungsten. The above results indicate that at the fully same fabrication technology, the trace ZrC does improve the mechanical properties and thermal stability of W. The possible micro-mechanisms were investigated and proposed. [ABSTRACT FROM AUTHOR]