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Mechanical alloying (MA) is widely used to produce oxide‐dispersion‐strengthened (ODS) steels, which are potential candidate structural materials for the next‐generation fusion reactors. Here in this study, two kinds of ODS ferritic alloys, labeled A and B, are prepared through MA, followed by spark plasma sintering (SPS) and annealing. To prepare Alloy A, Fe powder, YH2 powder, and TiO2 powder are mixed for MA. To prepare Alloy B, a pre‐alloyed Fe–Cr–W–Y powder is first obtained by gas‐atomization, after which TiO2 powder is added for MA. Compared with the traditional MA method, where the highly stabilized Y2O3 powder is usually selected, the use of TiO2 powder successfully reduces the milling time since it should be more easily decomposed and dissolved into the ferrite matrix. Some TiO2–Y2TiO5 duplex oxide particles of about 50 nm are found to generate through diffusion‐induced in situ reactions in Alloy A. In Alloy B, in contrast, a high number density of well‐distributed Y2O3 particles of about 20 nm and ultrafine Y2Ti2O7 particles within 10 nm are observed. These nanoparticles maintain good coherent interfaces with the matrix, suggesting the precipitation mechanism. Herein, a new route for the efficient fabrication of ODS alloys is provided. [ABSTRACT FROM AUTHOR]

Abstract: Taking the use of Nb and Si elemental powders as raw materials, Nb/Nb5Si3 composites were successfully fabricated by a spark plasma sintering (SPS) technology. The influence of sintering temperatures on microstructures of the synthesized composites was mainly investigated. The results show that there exists a critical sintering temperature T c (1400°C) in the synthesis of Nb/Nb5Si3 composites by SPS technology. When sintering temperature is lower than T c, an intermediate Nb3Si phase is produced in the fabricated samples. Moreover, the relative density of the samples is lower. Only if the sintering temperature is higher than T c, the intermediate Nb3Si phase is thoroughly eliminated, Nb particles become a finer size and desirable Nb/Nb5Si3 composites up to 99.59% theoretic density are achieved. [Copyright &y& Elsevier]

Abstract: Spark plasma sintering was employed to synthesize high-density bulk MoSi2 in one step, using Mo and Si element powders as starting materials. Influence of sintering temperature on sintering behavior and microstructures of MoSi2 were investigated. The sintering behavior at whatever temperature (1473, 1673 and 1873K) is characterized by four stages, i.e., initial expansion, slight shrinkage, abrupt shrinkage and slight expansion. The maximum shrinkage displacement increased with increasing sintering temperature. When the sintering temperature reaches 1673K or 1873K, the second phases, i.e., SiO2 and Mo5Si3/Mo4.8Si3C0.6, were uniformly distributed in the synthesized MoSi2 matrix accompanied with a small amount of porosity. Most of SiO2 and Mo5Si3/Mo4.8Si3C0.6 particles were concentrated at grain boundaries. The relative density of the products (atomic ratio: Mo/2.00Si) was improved tremendously from 89% to 98.2% over the range 1473–1673K, and much smaller enhancement up to 99.0% was achieved from 1673 to 1873K. At the same time, the grain size and amount of second phase particles (mainly Mo5Si3/Mo4.8Si3C0.6) consistently increased with increasing temperature over 1473–1873K. However, the use of a slight excess of Si (e.g., atomic ratio: Mo/2.06Si) at 1673K resulted in dense products of MoSi2 nearly free of Mo5Si3/Mo4.8Si3C0.6, with the relative density of 99.2% and the average grain size of 5–10μm. Thereby, in order to pursue an equilibrium among densification, microstructural refinement and formation of second phases, the most suitable sintering temperature and stoichiometry for fabrication of MoSi2 by SPS are recommended to be 1673K and a hyperstoichiometry of Mo/2.06Si in the present work. [Copyright &y& Elsevier]

An oxide-dispersion-strengthened (ODS) 13Cr-1W steel has been fabricated through mechanical alloying (MA) and spark plasma sintering (SPS) using pre-alloyed Fe-Cr-W-Y powder and TiO 2 powder. Sufficient MA effects, indicated by homogeneous distribution of alloying elements and high level of lattice strain inside the powder, have been obtained within 20 h of high-energy ball-milling. Grain refinement of the bulk materials is successfully achieved by optimizing the sintering temperature and pressure during SPS. A fine-grained ODS steel with average grain size of 626.75 nm is prepared when sintered at 950 °C/80 MPa. Ultrafine oxide dispersoids, identified as Y 2 O 3 , Y 2 TiO 5 and Y 2 Ti 2 O 7 , are observed homogeneously distributed in the steel matrix after annealing. They have a number density of 4.5 × 1022 m−3 and an average size of 11.15 nm. Tensile tests from room temperature to 700 °C are conducted to this ODS steel. It exhibits an ultimate tensile strength and a yield strength of 1559.60 MPa and 1352.82 MPa at room temperature, respectively. Due to a good combination of dislocation strengthening, grain boundary strengthening and precipitation strengthening, this alloy wins superior tensile properties over most of the commercial ODS steels and those reported in some previous studies. • A nano-Y-Ti-O dispersion strengthened 13Cr-1W steel was prepared by MA and SPS. • MA process has been finished within 20 h using Y-containing pre-alloyed powder and TiO 2 powder. • Grain refinement was achieved by optimizing sintering temperature and pressure. • High number density of Y-Ti-O nanoparticles in-situ precipitated during annealing. • The steel possesses excellent tensile properties from room temperature to high temperature. [ABSTRACT FROM AUTHOR]

Abstract: Bulk dense composites of Al–Fe alloys containing 2.5–10at% Fe were fabricated by mechanical alloying (MA) and spark plasma sintering (SPS). Supersaturated Al(Fe) solid solutions were obtained by MA for 80h. The sintered samples are composed of nano and ultrafine needle-like Al13Fe4 phase and angular-shaped Al13Fe4 phase with a size range of 1–2μm uniformly distributed in the Al matrix. Needle-like Al13Fe4 phase originates from the precipitation of supersaturated Al(Fe) solid solutions, and angular-shaped Al13Fe4 phase originates from the reaction of undissolved Fe particles and the Al melt. The hardness of the alloys varied from 1.44 to 1.97GPa and Al–10%Fe exhibited highest specific yield strength of 391.1kNm/kg. The yield strength varied from 657 to 1130MPa, depending on the Fe content. Excellent plastic strain (>14.5%) were achieved in the alloys containing 2.5–5%Fe, but the Al–10%Fe exhibited elastic behavior only, failing without any macroscopic yielding or plastic strain. The lack of plastic performance of Al–10%Fe is attributed to large amount of undissolved Fe particles reacted with the Al melt to form angular-shaped Al13Fe4, leading to the absence of soft α-Al phase. [Copyright &y& Elsevier]

Abstract: Nb/Nb5Si3 composites were successfully fabricated by a spark plasma sintering (SPS) technology. The effects of element (Nb and Si) proportions on the microstructures of the synthesized composites were mainly investigated. The results show that element proportions strongly affect the microstructures of Nb/Nb5Si3 composites; Nb/Nb5Si3 in situ composites up to 99.59% of theoretical density were fabricated by SPS technology, and the microstructures of the fabricated composites comprise the synthesized Nb5Si3 and the uniformly distributed Nb particles. Moreover, with the increase in the Si content from 6% to 20% (atom fraction), the volume fraction of the synthesized Nb5Si3 in the composites increases, whereas the content and size of Nb particles decrease obviously. The higher shrinkage and densification for Si content (16at.% and 20at.%) close to the eutectic composition take place. When sintering temperature over 1400°C, the shrinkage obviously retards and finally stops. [Copyright &y& Elsevier]