Nanocrystalline rare-earth high-entropy alloys Gd20Dy20Er20Ho20Tb20 samples are prepared by high-pressure torsion method， and their magnetic transformation and magnetocaloric effect are studied. The results show that， compared with the as-cast coarse-grained samples， the nanocrystalline samples exhibit a more pronounced second-order magnetic transition from paramagnetic to antiferromagnetic at the Néel temperature of 183 K. In addition， the refrigerant capacity of the nanocrystalline samples decreases （627 J·kg⁻¹ and 528 J·kg⁻¹， respectively， at a 5 T magnetic field）， while the working temperature interval widens from 102 K to 113 K. Analysis indicates that， unlike conventional magnetic refrigerant materials such as Pr₂Fe₁₇ and GaCMn₃， for high-entropy alloys which are intrinsically characterized by high chemical disorder， the microstructural nanocrystallization and the structural disorder arising from the large number of irregularly arranged atoms at grain boundaries do not significantly enhance the magnetocaloric effect， but can effectively broaden the working temperature interval.
Nickel-based single-crystal superalloys exhibit excellent high-temperature mechanical properties， oxidation resistance， and corrosion resistance. However， solidification defects such as sliver defects often occur during the preparation of single-crystal blades， compromising their structural integrity and significantly degrading high-temperature performance. Understanding the formation mechanisms， influencing factors， and distribution patterns of sliver defects is therefore essential for defect prevention and microstructural optimization. This study investigates the effect of withdrawal rate on sliver defect formation.Results show that at low withdrawal rates （1-2 mm/min）， sliver defects are distributed on both the heating and shadow sides of castings， with higher frequency. At high withdrawal rates （4-6 mm/min）， freckles primarily form on the upper shadow side， with lower frequency. As the withdrawal rate increases， the average length of sliver defects increases， while their misorientation with the matrix decreases. Two formation mechanisms are identified： thermalsolutal convection in the mushy zone causing dendrite fragmentation， and adhesion of dendrites to the mold wall in the mushy zone followed by tensile rupture during solidification. Both mechanisms operate at low withdrawal rates， whereas the second mechanism dominates at high rates.
The lead-based fast reactor is an advanced nuclear reactor with advantages such as high thermal efficiency， good neutron economy， and excellent fuel-cycle capability， making it an important research direction in nuclear energy development. It uses liquid lead-bismuth eutectic （LBE） as the coolant， which has a high boiling point， good neutron performance， high cooling efficiency， and stable chemical properties. However， it is highly corrosive to metallic structural materials. In the LBE environment， structural materials such as stainless steel face severe challenges of liquid metal corrosion and liquid metal embrittlement， directly threatening the safe and reliable operation of the reactor. This article systematically reviews the latest progress in the interaction between stainless steel and LBE， including corrosion mechanisms， influencing factors， and protective strategies， providing a reference for the design of stainless steel materials and components resistant to LBE corrosion.
Wire Arc Additive Manufacturing （WAAM） has attracted significant attention for the fabrication of large-scale titanium alloy structural components in aerospace and related fields due to its high deposition efficiency and fewer size constraints. However， the combination of high heat input and directional solidification tends to produce coarse primary β columnar grains preferentially aligned along the 〈001〉 direction， which， together with texture inheritance during rapid solid-state phase transformation， promotes the formation of acicular α bundles and results in pronounced anisotropy in the mechanical properties of the deposited components， limiting their engineering application. This review focuses on the columnar-to-equiaxed transition behavior of primary β grains and its intrinsic correlation with isotropic performance. The evolution of the solidification microstructure is discussed in terms of melt pool thermal characteristics， solute redistribution， and nucleation behavior. Strategies such as process parameter optimization and microalloying to control primary β grain morphology are summarized， alongside post-processing techniques， including hot isostatic pressing， laser shock peening， and ultrasonic impact treatment， for refining columnar grain structures. This overview aims to provide theoretical guidance for achieving equiaxed microstructures and isotropic properties in WAAM titanium alloys.
Fe-based composite coatings with varying B4C contents（5%， 8%， and 10%， mass fraction， the same below） are prepared on Cr12MoV steel substrates using laser cladding technology. The effects of B4C content on the phase composition， microstructure， and corrosion resistance behavior of the coatings are systematically investigated by means of XRD， SEM，EDS， electrochemical measurements， and XPS analysis. The results show that the Fe-based composite coatings are mainly composed of α-（Fe，Cr） and γ-（Ni-Cr-Fe） solid solutions phases，as well as carbide and boride phases such as Fe2B，M7C3，Fe3Si， and M23C6. As the B4C content increases， the types and amounts of carbides and borides in the coatings correspondingly increase， and the interdendritic eutectic structure fully rises. However， an excessive amount of B4C（10%） leads to dendrite coarsening and noticeable carbide agglomeration. Composite coatings with different B4C contents exhibit superior corrosion resistance performance compared to the substrate in both 3.5%NaCl and 1 mol/L HCl solutions. Moreover， as the B4C content increases， the corrosion resistance performance of the coatings initially increases and then decreases.With 8%B4C addition， the Fe-based composite coatings exhibit distinct passivation in corrosive media. Benefiting from the synergistic effect of the passive film and the barrier layer formed by carbides， the coatings show excellent anti-permeation capability and optimal corrosion resistance performance.
