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Abstract Tungsten alloys with high strength, high toughness and high-temperature stability are strongly desired in extreme conditions. The nanoengineering of potassium bubbles (5–50 nm) is a fascinating strategy to strengthen these properties. However, such nano potassium bubbles can only be acquired in tungsten wires through swaging and drawing process till now. Here, we report an intra- and inter-potassium nano-bubbles strengthened bulk tungsten fabricated via an industrially applicable process combining aluminum-potassium-silicon (AKS) doping and spark plasma sintering (SPS), which exhibits desirable strength and remarkable toughness, as well as high thermal-shock resistance. The AKS-doping incorporated the K-Al-Si-O particles inside the W grains and the rapid high-temperature sintering of SPS produced the nanometer K bubbles from the K-Al-Si-O particles and kept the K bubbles inside the W grains. Our K-bubble strengthened tungsten material displays high potential in high-temperature applications. This strategy is also potentially applicable to other refractory metals such as molybdenum. Highlights • Nanoscaled potassium-bubbles strengthened bulk tungsten alloy is prepared. • This alloy exhibits highly desirable mechanical and thermal properties. • Those properties further lead to a high thermal-shock resistance. • This nanostructuring strategy helps guide endeavors to design other metal system. [ABSTRACT FROM AUTHOR]

Pure tungsten and tungsten-tantalum alloys with tantalum concentrations of 5, 10, 15 and 20 wt.% were fabricated by spark plasma sintering. Effects of tantalum concentration on the basic characterization of tungsten-tantalum alloys were studied. The results show that the addition of tantalum contributes to a decrease of grain size and an improvement of relative density and mechanical properties. Adding a small amount of tantalum (about 10 wt.%) increases the relative density significantly, while if the concentration of tantalum is higher than 15 wt.%, the relative density decreases apparently. The hardness of the alloy with 10 wt.% tantalum is highest, which is 508.65 HV, 42% higher than pure tungsten. The bending strength of the alloy with 5 wt.% tantalum reaches up to 742 MPa, which is 27.1% higher than pure tungsten. Pure tungsten fractures intergranularly, while the failure mode in the alloy is predominantly transgranular. SEM images show that if the concentration of tantalum is higher than 10 wt.%, tantalum tends to gather together, and this phenomenon has a negative effect on the mechanical property of materials. [ABSTRACT FROM AUTHOR]

Ti(C, N)-based cermets were coated with TiAlN and TiAlN/CrAlN films by physical vapor deposition. The cross-sectional morphology was characterized by scanning electron microscopy (SEM), and the adhesive strength was evaluated by the scratch test. Cutting tests on the coated cermets were conducted on the different cutting conditions. The cutting performance and wear mechanism were analyzed with SEM and EDS. It is found that TiAlN coating has a better adhesion to the cermet substrate. The coated cermet inserts show better wear resistance than the uncoated ones. By contrast, the TiAlN coating suffers a slight abrasive flank wear. However, the TiAlN/CrAlN coating show more severe adhesive flank wear because of the Cr interdiffusion between the inserts and the workpiece. In addition, TiAlN coating is weak in resisting against oxidation wear, while the TiAlN/CrAlN coating has an excellent resistance to oxidation. [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]

The unique solidification character of selective laser melting (SLM) can result in non-equilibrium microstructure and correspondingly unreliable mechanical properties in as-built Ti-alloy components. As a classical microstructure optimization method, heat treatment is promising in tailoring the microstructure and enhancing the mechanical properties of SLM-built Ti-alloys. This study aimed to increase the strength of metastable β structure of SLM-fabricated near β Ti-5Al-5Mo-5 V-3Cr-1Zr (Ti55531) alloy via heat treatment. Three conventional heat treatments, including solution in β phase region and aging (β-STA), triplex heat treatment, and solution in α + β phase region and aging (αβ-STA) were carried out to tailor the metastable β structure, and the transformed β, bi-lamellar and bimodal structures were formed respectively. Tensile tests were performed on horizontal and vertical planes in order to evaluate the anisotropy and the relationship between microstructures and mechanical properties. It was found that the strength and ductility were influenced by the intragranular α precipitates and the intergranular α continuity along β grain boundary, respectively. The anisotropic tensile behavior in these heat treated samples was affected by the β grain morphology. This work demonstrated that SLM-fabricated metastable β Ti-alloy had a strong heat treatability, which can provide different heat treated microstructures and mechanical property. • Ti55531 with metastable β structure was fabricated by SLM. • Three conventional heat treatments were used to tailor the metastable β structure. • Heat treatment can enhance the strength of SLMed Ti55531. [ABSTRACT FROM AUTHOR]