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The effect of hot rolling on the microstructure and fracture behavior of a bulk W–Y 2 O 3 alloy was studied. The as-sintered compact was comprised of polyhedral tungsten grains with an average grain size of 4 μm, spherical Y 2 O 3 disperoids and trace amount of nano-sized/submicron pores. It showed typical inter-granular fracture. After hot rolling, it was observed that the tungsten grains were elongated along the rolling direction, showing much severe deformation than Y 2 O 3 particles. The residual pores were reduced. The as-rolled alloy showed obvious anisotropic fracture behavior. For the longitudinal specimens, the fracture mode could be totally transformed to trans-granular cleavage fracture. Three point bending test showed that the longitudinal specimens of the bulk W–Y 2 O 3 alloy performed appreciable ductility and superior fracture strength (2152.7 MPa) as compared to the as-sintered alloy (brittleness, 543.4 MPa) and transverse specimens (brittleness, 1105.0 MPa). The responsible strengthening and toughing mechanisms were analyzed and presented. [ABSTRACT FROM AUTHOR]

The W-3 Y composites were successfully prepared by spark plasma sintering of milled W-3 Y powders with different milling times (0 h, 5 h, 15 h, 30 h). X-ray diffraction (XRD), scanning electron microscope (SEM), and laser particle size analysis were used to study the microstructural evolution and morphological change during the milling process. The crystallite sizes exhibited a continuous refinement along with the increased milling time. The median particle sizes, measured by the laser diffraction method, showed a similar change tendency. Due to the existence of Y particles, the W–Y milled powders exhibited spherical-like morphology while pure tungsten milled powders exhibited lamellar morphology at the early milling stage (5–15 h). The microhardness of W-3 Y compacts showed a slight increase with the increase of milling time. The maximum bending strength of 795 MPa was obtained by sintering W-3 Y powders milled for 15 h. As the milling time was prolonged to 30 h, the increased oxygen impurity resulted in a slight decrease of density as well as the degradation of bending strength. [ABSTRACT FROM AUTHOR]

The effects of rare earth elements (Y 2 O 3 , Y and La) on the consolidation behavior, microstructure and mechanical properties of tungsten alloys were investigated in this work. The starting powders were mechanical alloyed (MA) and then consolidated by spark plasma sintering (SPS). It was found that Y doping was beneficial to obtain fully dense tungsten alloys with more refined grains as compared to any other rare earth elements. The maximum values of Vickers microhardness and bending strength obtained from W–0.5 wt.% Y alloy reached up to 614.4 HV 0.2 and 701.0 MPa, respectively. [ABSTRACT FROM AUTHOR]

In this study, the microstructure and microhardness of tungsten–yttrium (W–Y) composites were investigated as a function of Y doping content (0.25–3 wt%). It was found that the crystallite sizes and the powder particle sizes were increased as a result of the increase of Y content. Nearly fully dense materials were obtained for W–Y alloys when the Y content was higher than 0.5 wt%. The EDS analysis revealed that the Y rich phases were complex (W–Y) oxides formed during the sintering process. The Y doping content showed obvious influence on the refinement of tungsten grains during sintering. W–1.5Y composite showed the finest microstructure with an average grain size of 0.32 μm, and thus achieved the highest Vickers microhardness with the value of 770 HV 0.2 . [ABSTRACT FROM AUTHOR]

The applicability of nano-crystalline W/Cu composites is governed by their mechanical properties and microstructural stability at high temperatures. Therefore, mechanical and structural investigations of a high-pressure torsion deformed W/Cu nanocomposite were performed up to a temperature of 600 °C. Furthermore, the material was annealed at several temperatures for 1 h within a high-vacuum furnace to determine microstructural changes and surface effects. No significant increase of grain size, but distinct evaporation of the Cu phase accompanied by Cu pool and faceted Cu particle formation could be identified on the specimen′s surface. Additionally, high-temperature nanoindentation and strain rate jump tests were performed to investigate the materials mechanical response at elevated temperatures. Hardness and Young′s modulus decrease were noteworthy due to temperature-induced effects and slight grain growth. The strain rate sensitivity in dependent of the temperature remained constant for the investigated W/Cu composite material. Also, the activation volume of the nano-crystalline composite increased with temperature and behaved similar to coarse-grained W. The current study extends the understanding of the high-temperature behavior of nano-crystalline W/Cu composites within vacuum environments such as future fusion reactors. [ABSTRACT FROM AUTHOR]