Effects of aluminum additions on the microstructure and mechanical properties of alumina-forming austenitic stainless steels

The mechanical properties, including tensile and impact properties at different testing temperatures of alumina-forming austenitic steels (25 % nickel, 20 % chromium) with different aluminum contents (0, 2.5 %, 5 % and 8 %) were investigated. Scanning and transmission electron microscopy together with tensile and impact properties tests were conducted. The results showed that the tensile strength of steels at 298 K increased obviously along with aluminum contents increasing, while plasticity decreased at the same, which attributed to the higher volume fraction and number density of spherical NiAl precipitation together with main ferrite in matrix. In addition, spherical NiAl particles dispersed easily in ferrite. In particular, the ultimate tensile strength of the sample with 8 % aluminum could reach 1398 MPa, with the elongation of 14 % at 298 K. However, NiAl precipitations would lose strengthening effects at high temperatures, but the plasticity could be improved. In addition, the sample with 5 % aluminum showed better comprehensive properties by comparison to other samples, and the ultimate tensile strength was 1018 MPa and 491 MPa at 298 K and 973 K with the elongation of 26 % and 43 %, respectively, enabling it to be promising material for industrial application in advanced nuclear systems.     

Diffusion bonding of transparent ceramics by spark plasma sintering (SPS) complemented by hot isostatic pressing (HIP)

Diffusion bonding is a viable technique for fabricating larger parts or composite transparent ceramics. Spark plasma sintering (SPS) and hot isostatic pressing (HIP) allow for simultaneous application of high temperature and pressure, making them suitable for bonding various materials, including transparent ceramics. In this study, we demonstrated the combined use of SPS followed by HIP for successful diffusion bonding of transparent MgAl₂O₄ (spinel) and Y₃Al₅O₁₂ (YAG) ceramics. The YAG samples had superior surface quality and were adequately bonded using SPS alone, while rougher spinel samples showed inadequate bonding initially due to insufficient surface contact. However, subsequent HIP treatment effectively closed the voids at the interface and promoted grain growth across the joint, resulting in a strong seamless bond. The combination of SPS and HIP, as a two-step process, holds promise for diffusion bonding of ceramics and offers a potential solution for compensating surface quality issues in the bonded parts.     

Research progress of rare earth composite shielding materials

With the rapid development of nuclear technology,nuclear protection has received extensive attention.As an important strategic resource,rare earth plays an important role in the field of nuclear shielding materials.In this review,the shielding principles of rare earth materials are first introduced.According to the type of matrix,the characteristics and current research status of metal-based,inorganic nonmetallic-based and polymer-based rare earth shielding materials are reviewed.Meanwhile,the f...     

Dynamic Precipitation of Laves Phase in FeCrAl Alloy with Zr Addition

FeCrAl alloy is one of potential candidates for accident-tolerant-fuel (ATF)-cladding materials due to its excellent oxidation and corrosion resistance at accident temperature, combining good mechanical properties at service temperature. Alloying strategy is an important way for improving comprehensive properties of FeCrAl alloy through the precipitation of fine Laves phase. Zr alloying can stabilize the Laves phase due to its lower diffusion coefficient and solubility in body-centered-cubic ferrite matrix. Herein, it is found that Zr addition changes the dynamic precipitation features of Laves phase in FeCrAl alloy during high-temperature deformation, from only one type of Fe₂M (M = Nb, Mo, Ta) Laves phase to Fe₂Zr combining Fe₂M-type Laves phase. The Fe₂Zr-type Laves phase precipitates dynamically first, and the interface precipitates between which with ferrite matrix creates more nucleation sites for subsequent precipitation of Fe₂M Laves phase. The results can be possibly applied for alloy design and microstructure tailoring in series of FeCrAl alloys used for ATF cladding in the near future.