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The Al-containing particles in ODS alloys with Al addition usually exhibit relatively large size, and inevitably result in a limited improvement in mechanical properties. In this paper, W-Al-Y 2 O 3 alloy was prepared by a two-step sintering process to refine the Al-containing particles. Microstructure evolution of dispersoid particles was characterized by scanning electron microscope (SEM), electron probe microanalysis (EPMA) and transmission electron microscopy (TEM). During the first holding step at 1000 °C, the dissolved Al precipitated directly from W matrix, where the formed γ-Al 2 O 3 particles were nano-sized and developed a coherent relationship with W matrix. This coherent relationship hindered transformation of γ-Al 2 O 3 into submicron-sized α-Al 2 O 3. Moreover, the nano-sized γ-Al 2 O 3 contributed to formation of fine Y 3 Al 5 O 12 dispersoid particles with the sintering temperature further increased to 1600 °C. 71% of the dispersoid particles were distributed within grains and most of them were nano-sized γ-Al 2 O 3 and Y 3 Al 5 O 12 , giving a fine grain size of 0.49 μm. Due to the refined microstructure, the compressive strength and microhardness of W-Al-Y 2 O 3 alloy reached 2545.9 MPa and 787.8 HV, respectively. • W-Al-Y 2 O 3 alloy was prepared by two-step SPS to refine Al-containing dispersoids. • Nano-sized γ-Al 2 O 3 precipitated from W matrix during first holding step at 1000 °C. • Nano-sized γ-Al 2 O 3 exhibited coherent relationship with W matrix. • Nano-sized γ-Al 2 O 3 also contributed to formation of fine Y 3 Al 5 O 12 dispersoids. • Compressive strength and microhardness reached 2545.9 MPa and 787.8 HV, respectively. [ABSTRACT FROM AUTHOR]

Aggregation of Y 2 O 3 particles with relatively large size along grain boundaries is a main limiting factor for performance improvement in W–Y 2 O 3 alloys. In order to tailor the distribution and achieve size refinement of Y 2 O 3 dispersoids, W–Y 2 O 3 alloy was prepared using ball milling with extended milling time and subsequent spark plasma sintering (SPS) in this study. Microstructure evolution of Y 2 O 3 during the preparation process was characterized in detail using X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). Mechanical properties of SPSed alloy were evaluated in terms of microhardness, three-point bending and compression tests. Structure transformation of Y 2 O 3 from BCC to FCC during the process of ball milling and subsequent sintering was first identified in W–Y 2 O 3 alloy in this study. Compared with the raw micron sized Y 2 O 3 powders, the transformed Y 2 O 3 dispersoids experienced significant size refinement. Around 76% of the nanosized Y 2 O 3 dispersoids were distributed inside grain interior, and they exhibited semi-coherent relationship with tungsten matrix. These microstructural characteristics contributed to the high compressive strength of 1804.2 MPa and microhardness of 625.7 HV in the SPSed W–Y 2 O 3 alloy. • W–Y 2 O 3 alloy were prepared by extended ball milling and SPS. • Structure transformation of Y 2 O 3 from BCC to FCC was identified in W–Y 2 O 3 alloy. • Y 2 O 3 also experienced size refinement and 76% of them were inside grain interior. • The nanosized Y 2 O 3 exhibited semi-coherent relationship with tungsten matrix. • Y 2 O 3 dispersoids contributed to improved strength mainly through grain refinement. [ABSTRACT FROM AUTHOR]

Aggregation of Y 2 O 3 particles with relatively large size along grain boundaries is a main limiting factor for performance improvement in W–Y 2 O 3 alloys. In order to tailor the distribution and achieve size refinement of Y 2 O 3 dispersoids, W–Y 2 O 3 alloy was prepared using ball milling with extended milling time and subsequent spark plasma sintering (SPS) in this study. Microstructure evolution of Y 2 O 3 during the preparation process was characterized in detail using X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). Mechanical properties of SPSed alloy were evaluated in terms of microhardness, three-point bending and compression tests. Structure transformation of Y 2 O 3 from BCC to FCC during the process of ball milling and subsequent sintering was first identified in W–Y 2 O 3 alloy in this study. Compared with the raw micron sized Y 2 O 3 powders, the transformed Y 2 O 3 dispersoids experienced significant size refinement. Around 76% of the nanosized Y 2 O 3 dispersoids were distributed inside grain interior, and they exhibited semi-coherent relationship with tungsten matrix. These microstructural characteristics contributed to the high compressive strength of 1804.2 MPa and microhardness of 625.7 HV in the SPSed W–Y 2 O 3 alloy. • W–Y 2 O 3 alloy were prepared by extended ball milling and SPS. • Structure transformation of Y 2 O 3 from BCC to FCC was identified in W–Y 2 O 3 alloy. • Y 2 O 3 also experienced size refinement and 76% of them were inside grain interior. • The nanosized Y 2 O 3 exhibited semi-coherent relationship with tungsten matrix. • Y 2 O 3 dispersoids contributed to improved strength mainly through grain refinement. [ABSTRACT FROM AUTHOR]

W alloys prepared via oxide dispersion strengthening have shown enhanced mechanical performance. In this paper, W-1.10 vol% Zr-2.00 vol% Y 2 O 3 (WZY) and W-1.10 vol% Zr-2.00 vol% Er 2 O 3 (WZE) were fabricated to investigate the effects of formation of complex oxide dispersions on mechanical properties and microstructure of multi-doped W alloys. By controlling the atomic ratio of added ZrH 2 and rare earth oxides through composition design, the goal of complete formation of complex oxide particles with pyrochlore structure (A 2 B 2 O 7) was achieved. Electron probe microanalysis (EPMA) and transmission electron microscopy (TEM) results showed that these dispersion particles in WZY and WZE were Y 2 Zr 2 O 7 and Er 2 Zr 2 O 7 , respectively. Moreover, microstructure analysis showed that Er 2 Zr 2 O 7 exhibited smaller size, higher number density and more homogenous distribution compared to Y 2 Zr 2 O 7 , which led to finer grains of WZE (0.58±0.03 μm) compared to WZY (1.34±0.29 μm). Finer microstructure including smaller grains and dispersion particles of WZE contributed to its higher strength and better ductility. Furthermore, the formation mechanism of complex oxide dispersion particles was discussed in detail. • W–Zr–Er 2 O 3 (WZE) and W–Zr–Y 2 O 3 (WZY) were fabricated to investigate the effects of formation of complex oxide dispersions on W alloys. • By controlling the atomic ratio of Zr:Y/Er to be 1:1, the complete formation of complex oxide particles with pyrochlore structure A 2 B 2 O 7 were achieved. • The formation of Er 2 Zr 2 O 7 and Y 2 Zr 2 O 7 can be explained by the mechanism of dissolution-reprecipitation. • Finer Er 2 Zr 2 O 7 (44.37 nm) with a higher number density distributed more homogeneously in WZE compared to Y 2 Zr 2 O 7 (92.65 nm), which made WZE have higher bending strength and better ductility performance compared to WZY. [ABSTRACT FROM AUTHOR]

Oxide dispersion strengthened tungsten (ODS-W) alloys are promising plasma facing material in future fusion reactors. In this study, composite powders of W-Er 2 O 3 were prepared by co-deposition method and hydrogen reduction, and then consolidated by spark plasma sintering (SPS). Microstructure evolution during co-deposition process was investigated using X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and Fourier transform infrared spectrometer (FTIR). Also, simulation using DMol3 module in Materials Studio was carried out to understand the co-deposition mechanism. The results showed that H+ of W-OH bond in white tungstic acid was replaced by Er3+ due to coordination reaction during co-deposition process, leading to formation of ring-like chelate of (WO) n Er. This indicates that doping of Er3+ was achieved at a molecular level. Consequently, Er 2 O 3 particles were relatively uniformly distributed in W-Er 2 O 3 alloy, and the hardness and compressive strength reached 627 ± 19 HV and 1640 ± 40 MPa, respectively. • Thermodynamic diagram of W-H 2 O was calculated to optimize co-deposition process. • Co-deposition mechanism was analyzed by simulation and experimental methods. • W-Er 2 O 3 alloy was prepared by co-deposition method and two-step SPS. • Er 2 O 3 particles were relatively uniformly distributed in alloy. • Hardness and compressive strength reached 627 HV and 1640 MPa, respectively. [ABSTRACT FROM AUTHOR]