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Trace titanium and yttrium (~0.1 wt.%) were doped to the novel W-K-Mo-Ti-Y alloys to investigate their performance under simulated transient heat loads in fusion reactor. The micro-structure, Vickers micro-hardness, cracks formation and surface roughness after transient heat loads were analyzed through X-ray diffraction analysis (XRD), Vickers Micro-hardness device, scanning electron microscopy (SEM) and three dimensional (3D) industrial optical microscope, respectively. It indicated that the transient heat loads would lead to surface cracking and roughening on the loaded surface, as well as a decrease on micro-hardness. Further, trace titanium and yttrium doping in the samples could largely mitigate surface roughening after transient heat loads. Both titanium and yttrium have significant influence on the surface cracking threshold and plastic deformation, indicating the improvement of transient heat loads resistance in this novel alloy. [ABSTRACT FROM AUTHOR]

W-K-TiC alloys with different titanium carbide concentration (0.05, 0.1, 0.25, 1) wt.% were fabricated through spark plasma sintering (SPS) method. Single shot thermal shock tests with a length of 5 ms and 100 shots thermal shock tests with a length of 1 ms were carried out. The microstructure and Vickers micro-hardness of each sample were investigated. It is revealed that the surface of the samples began to recrystallize after thermal shock tests, and the samples with 5 ms for single shot had more serious recrystallization than the samples with 1 ms for 100 shots because of its higher surface temperature after thermal shock tests. The samples were annealed at 1400 °C, 1600 °C, 1800 °C, respectively. It is shown that the addition of TiC particles could slow down recrystallization of W-K-TiC alloy, and its recrystallization temperature can reach to between 1400 °C and 1600 °C. [ABSTRACT FROM AUTHOR]

Effects of helium plasma irradiation on spark plasma sintering (SPS) W-K, pure W and traditionally sintered commercial W-K have been studied, concerning the density, grain size and potassium content as the influence factors. Pinholes are formed under 120 eV He ions at 600 °C and 1 × 10 23 m −2 fluence on the surface of all samples. It is found that SPS-sintered W-K shows the best irradiation resistance among the present samples, and SPS-sintered pure W exhibits higher irradiation tolerance than commercial W-K. Different He-plasma tolerance was observed among the SPS-sintered W-K samples due to varied potassium content and grain size. In addition, the microstructure evolution under helium irradiation, the growth-migration of helium bubbles and their interactions of potassium bubbles have also been discussed. [ABSTRACT FROM AUTHOR]

W K Mo Ti Y powder were mechanically alloyed (MA) and then consolidated through spark plasma sintering (SPS). Four different concentrations of molybdenum, i.e ., (0, 2, 5, 10) wt%, were applied to investigate the behavior of the alloys. The microstructure, Vickers micro-hardness and thermal shock behavior were analyzed. It is found that the molybdenum doping can mechanically alloy with tungsten and occupy tungsten lattice, which results in a correspondingly decrease of Vickers micro-hardness and thermal conductivity at the room temperature. Among the molybdenum doped samples, W K-2wt% Mo Ti Y alloy displays highly enhanced resistance against thermal shock. It is suggested that appropriate molybdenum doping in W K Mo Ti Y alloy is beneficial in consolidating and improving its thermal shock resistance. [ABSTRACT FROM AUTHOR]

Dense potassium-doped tungsten (W–K) ingots with homogeneously dispersed nanoscaled bubbles were fabricated by spark plasma sintering (SPS) using Al–K–Si (AKS) doped tungsten powder. Parameters such as sintering temperature, holding time and sintering pressure were considered to tune the grain size, density, microhardness, bubble formation and impurity contents. In addition, a two-step sintering scheme was designed to reduce Al/Si impurity contents and enhance the density. The sample prepared by the two-step sintering scheme displays both inter- and intra-granular nanocomposites, which is expected to have better creep resistance, high bending strength and fracture toughness. Potassium was detected inside the bubbles, determining the crucial role in the bubble formation process, and thus leading to compatible properties as plasma-facing material. [ABSTRACT FROM AUTHOR]

Nano‑potassium bubble strengthened tungsten (W-K) alloy with excellent overall performance has been proven to be one of the most desirable plasma facing materials (PFMs). However, some key properties, e.g., thermal heat resistance, ductile-brittle transition temperature (DBTT), strength and toughness need to be further improved to meet the requirements of fusion reactor. Herein, pure yttrium (Y) was doped in W-K alloy to achieve multiple strengthening effects. The grains of W-K alloy have been significantly refined, and the tensile strength was improved along with the introducing of Y. Thermal shock cracking threshold has increased to exceed 0.62 GW/m2. Interestingly, the existing form and size of the precipitates differed with the change of doping amount, leading to the nonlinear evolution of DBTT. The W-K alloy with 0.1 wt%-Y doping content (W-K-0.1Y) showed the best match of strength and toughness. Furthermore, coupled with relatively good thermal conductivity, W-K-0.1Y alloy displayed prominent thermal shock resistance. This work may pave a way for designing PFMs with higher performance. • Pure yttrium (Y) was doped in W-K alloy to realize multiple strengthening effects. • The grains of W-K alloy were significantly refined by Y doping. • The existing form of the precipitates differed with the change of doping content. • The DBTT of W-K-0.1Y alloy has been reduced to ~200 °C. • The thermal shock cracking threshold of W-K-0.1Y alloy exceeded 0.62 GW/m2. [ABSTRACT FROM AUTHOR]

In this work, the first successful attempt of additive manufacturing (AM) Ti-55531 near-β alloy fabricated by laser melting deposition (LMD) is reported. Optimized processing parameters of LMD were used to manufacture high relative density (99.8%) Ti-55531 alloy. It was found that the microstructure of as-deposited sample is mainly composed of β phase with heterogeneous distribution of α phase. The heterogeneity of microstructure of as-deposited sample was caused by the ubiquitous temperature gradient during LMD process. Thus, the as-deposited samples have a significant anisotropic tensile property which may not meet the aeronautical criterion. To overcome the issue of inhomogeneous microstructure and minimize the anisotropy, the microstructure was tailored by two kinds of heat treatment, i.e., β solution treatment subsequent aging (β-STA) and triplex annealing (α/β-STA). A transformed β microstructure was obtained in β-SAT condition, which resulted in the high ultimate tensile strength (UTS) (>1350 MPa) and low ductility (<6.5%). Besides, the bimodal structure was formed in α/β-STA condition and the associated sample shows an excellent balance of strength (UTS>1200 MPa) and ductility (>8%). Furthermore, the formation mechanism of microstructure and the subsequent impact on mechanical properties was systematically discussed. This work demonstrates the potential of fabricating Ti-55531 alloy parts by LMD and paves the way for enhancing LMD processed near β Ti-alloys through heat treatment. • The Ti-55531 alloy was fabricated by LMD with high density of 99.8%. • The deposited sample exhibits a mixed structure with columnar and equiaxed grains. • The β transformed structure and bimodal structure are obtained by heat treatment. • Triplex annealing drives superior tensile properties in LMD processed Ti-55531 alloy. [ABSTRACT FROM AUTHOR]