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• W alloy irradiated by W2+ and He+. • Pre-damage accelerates the growth of the fuzzy structure to the shedding stage. • Ta-enriched grains show fragmentation under He+ irradiation. Tungsten (W) has been selected as the material for the divertor in ITER due to its good thermal and mechanical properties, and alloying of tungsten has been considered as a potential way to enhance the properties of tungsten. However, the effect of the alloying elements on the irradiation resistance of the material still need to be studied. In this study, we prepared tungsten-tantalum (Ta) alloys, namely, W-1wt%Ta and W-3wt%Ta, by spark plasma sintering (SPS). The feedstock powder was obtained by ball-milling and mixing of W and Ta powders. The bulk material containing a large number of W grains with Ta at the grain boundaries (Ta-enriched grains) was obtained by rapid sintering via SPS. The alloy was subsequently irradiated with high-energy W self-ion (W2+) irradiation and low-energy and high-flux helium ion (He+) irradiation, for exploring the irradiation resistance of the alloy. Ta-enriched grains were found to be more susceptible to the damage by He+, the Ta-enriched grains located near the fuzz layer are damaged by He+. Pre-damaged sample (samples were first irradiated via W2+ ion before He+ irradiation) shows more sparse fuzzy structure than the non-pre-damaged samples. This work explores the effect of the presence of Ta-enriched grains on the irradiation resistance and provides reference information for the irradiation performance of other materials with the presence of enrichment element at the grain boundaries. [ABSTRACT FROM AUTHOR]

Optimizing and regulating the process parameters to form a uniform distribution of nanosized dispersoids remains a major challenge in additive manufacturing oxide dispersion strengthened (ODS) alloys. This study introduces the influence of scanning speed and laser power on the microstructure evolution of laser powder bed fusion (LPBF) ODS FeCrAl alloy. Low laser power and high scanning speed reduce the size of oxide particles and increase their number density. The energy density threshold is 83 J/m3, below which the powder fails to achieve complete melting, leading to the formation of defects during solidification. High density and large number of oxide particles were obtained for the printed samples under the parameters of 140 W laser power and 600 mm/s scanning speed. The average size and number density of oxide particles were ∼ 21.61 nm and ∼ 1.8 × 1020/m3, respectively. High scanning speed have a rapid cooling rate which affects the dislocation density and the average width of the columnar grains. Low laser power significantly weakens the 〈100〉 fiber texture, which is related to the degree of recrystallization in the remelted region. The core-shell oxides consisting of Y-Al-O and Y-Ti-O were distributed in the samples deposited at low and high laser powers, respectively. The formation of core-shell oxide particles in LPBF ODS FeCrAl alloys involves solid-state amorphization and recrystallization. This study can be a guideline to achieve materials with specific microstructure for ODS alloys. • High-density ODS FeCrAl alloys were built by selective laser melting (SLM) process. • Low laser power and high scanning speed result in obtaining small-sized and high-density nanoparticles. • The modification of the laser power affects the composition of core-shell structured oxide particles. • The formation of nanoparticles in SLM ODS FeCrAl alloys involves solid-state amorphization and recrystallization. [ABSTRACT FROM AUTHOR]

Powder bed fusion (PBF) is a well-established method in the additive manufacturing (AM) industry. Despite its popularity, effectively managing the microstructure and mechanical properties of PBF-produced components remains a significant engineering challenge. This study aims to address this challenge by investigating the thermal accumulation effect of PBF substrate preheating on sample microstructure. The study demonstrates the graded microstructure resulting from "in-situ aging" at 630 °C at different deposition heights. The results reveal how heat accumulation and cooling rate contribute to the varying α p lamellae content and α phase selection across different regions. Notably, the bottom region, with an α p lamellae content of 53.5% and a βr content of 46.5%, exhibits the highest of fracture toughness value of 87.5 MPa.m1/2. The mechanical properties exhibit a clear grade distribution with increasing deposition height. In-situ manipulation of microstructure and mechanical properties provides theoretical and engineering guidance for future AM strategies. [ABSTRACT FROM AUTHOR]

The metal additive manufacturing (AM) technology offers a unique advantage for production of complex and unconventional parts. However, the thermal history during the AM process often leads to anisotropy in the mechanical properties and inherent porosity of the deposits, which limits their performance compared to traditional forgings. To overcome these limitations, laser powder bed fusion (LPBF) technology was employed to produce single-step die-forging preforms. This innovative approach used coarse powder with a wide distribution of particle sizes to create a variety of molten pool structures, preventing the growth of columnar β grains in AM Ti–5Al–5V–5Mo–3Cr–1Zr (Ti-55531) alloys. The subsequent die-forging process eliminated inherent defects and regulated grains to be near-equiaxed, significantly improving the mechanical properties and reducing anisotropy. With proper post-heat treatment, the strength-ductility trade-off of the Ti-55531 alloy was adjusted to meet standards. This unconventional process route produced parts with isotropic and excellent mechanical properties, overcoming the defects and anisotropic properties of AM parts. This supplement to the traditional manufacturing process of high-performance titanium alloy parts holds great promise for future applications. [ABSTRACT FROM AUTHOR]

Obtaining higher mechanical properties, particularly the coexistence of strength and ductility, is always an important issue for high-strength and high-ductile metastable β titanium alloy, such as Ti55531. Rare earth element doping to gain reticulate structure is a possible way to break the strength-ductility trade-off considering the excellent capability of yttrium in improving the properties of titanium alloys and limiting grain growth. In this study, a new strategy was devised for the preparation of Ti55531 alloys with a reticulate structure by introducing yttrium and a tailored spark plasma sintering (SPS) procedure. Compared to the homogeneous structure, the strength of the material with a reticulate structure is prominently improved at the little expense of loss in ductility. Furthermore, the addition of yttrium can significantly increase the precipitation of α phase by affecting the local element concentration. It is hoped that this study can provide important inspiration for improving the mechanical properties of powder metallurgy fabricated titanium alloys. • Titanium alloys with reticulate structure prepared by doping yttrium and SPS technology. • The Ti55531 alloy with reticulate structure has good strength-ductility matching. • Yttrium affects the microstructure evolution and crack propagation path of Ti55531 alloy. [ABSTRACT FROM AUTHOR]

Recently, additive manufacturing (AM) of titanium alloys has become favored by manufacturing industries. However, the obvious anisotropy of microstructure during the process of AM will be caused by the complex solidification mechanism, which will cause uncertainties in determining corrosion behavior. Two heat treatment techniques are developed to tune the microstructure of selective laser melted Ti-5Al-5Mo-5V-3Cr-1Zr (Ti-55531) alloy, i.e. , αβ phase region (αβ-STA) and supertransus triplex heat treatment (Triplex-HT). Bimodal and bi-lamellar microstructure are obtained after certain heat treatments and the corresponding corrosion resistance is systematically investigated. The columnar β grains in the vertical planes (VP) are eliminated by conducting Triplex-HT, and the corresponding corrosion anisotropy between the horizontal planes (HP) and VP is significantly reduced. While the Ti-55531 treated by αβ-STA possesses significant refinement of primary α precipitates (α p) within β grains. The size of α grains relates to the Al-rich active region, where the corrosion pits are mainly concentrated. Further immersion experiments indicate that the generation and development of pits on the passive film are determined by the occupation of oxygen vacancies by chlorine ions. The results are expected to provide a reference for the selective laser melting (SLM) Ti-55531 alloy to eliminate anisotropy and improve corrosion resistance by the adjustment of the micromorphology. • The anisotropy of the corrosion behavior of Ti-55531 is caused by columnar β. • The isotropy of Ti-55531 alloy is achieved by supertransus triplex heat treatment. • The formation of oxygen vacancies is influenced by elemental segregation. • Oxygen vacancy plays a decisive role in pitting resistance of passive film. [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]