Risheng Qiu

CeO₂ is widely used as a non-radioactive surrogate for UO₂ because of its fluorite crystal structure and similar thermophysical characteristics. In this study, an FIB-assisted specimen preparation route combined with high-temperature nanoindentation was used to evaluate the micromechanical behavior of CeO₂ from room temperature to 400 °C. Hardness and Young’s modulus were experimentally measured at room temperature, 100 °C, 200 °C, 300 °C, and 400 °C. The load–displacement curves were smooth, and no obvious pop-in events were observed within the tested load range. From 100 °C to 400 °C, both Young’s modulus and hardness decreased approximately linearly with increasing temperature, and linear fitting was used to describe their temperature dependence. The measured Young’s modulus decreased from 191.3 ± 14.0 GPa at 100 °C to 136.7 ± 9.5 GPa at 400 °C, while the hardness decreased from 6.79 ± 0.58 GPa to 5.08 ± 0.48 GPa. The obtained temperature-dependent trend is consistent with previously reported high-temperature nanoindentation data for fluorite-structured oxides. These results provide useful micromechanical data and methodological support for elevated-temperature small-scale mechanical characterization of ceramic nuclear fuel surrogate materials.

The effect of deep cryogenic treatment (DCT) on microstructure and mechanical properties of 10.5Cr–1.5W–2.0Mn ferritic/martensitic steel is studied. The results show that DCT has little effect on the hardness and strength of steels, while the plasticity and toughness of steels can be significantly influenced by DCT. An appropriate DCT process can greatly improve the plasticity and toughness of steels. The impact toughness and elongation of the steel through 2‐cycle DCT are 28.8 and 30.8% higher than the steel without DCT, respectively. The results of microstructure show DCT‐refined martensitic laths/blocks, reduced carbide size, increased carbide volume fraction, and increased dislocation density. The fine‐grain strengthening effect caused by the refinement of martensitic laths/blocks improves the plasticity and toughness of the steel, while the dislocation strengthening effect caused by the increase of dislocation density and the precipitation strengthening effect caused by the precipitation of fine carbides reduce the plasticity and toughness of the steel.

The microstructure and properties of as‐cast Zr‐2.5Nb‐1X (X = Ru, Mo, Ta and Si) alloy are screened to explore novel biomedical zirconium alloys for magnetic resonance applications. Corresponding microstructure and phase transformation were characterized using X‐ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). Hardness test, magnetic detection and electrochemical corrosion measurements are taken to present properties. The results show that all alloys consist of α‐Zr, β‐Zr and ω‐Zr. α‐Zr and β‐Zr mainly exist in the form of parallel and intersecting plates, and nanoscale ω‐Zr is dispersed in β‐Zr plate. Especially, blocky ω‐Zr with needle‐like α‐Zr is only found in plate‐free blocks of Zr‐2.5Nb‐1Mo/Ru alloy. The orientation relationship (OR) between α‐ Zr and ω‐Zr follows // and //( 011) _ω . Combining this OR with the OR between β‐Zr and ω‐Zr, the transformation relationship between β‐Zr/ω‐Zr and α‐Zr is also discussed. Zr‐2.5Nb‐1Ru alloy with high corrosion potential (− 0.500 V), low corrosion rate (0.949 μm·year ^–1 ) and low magnetic susceptibility (92 × 10 ⁻⁶ ) shows great potential to be a novel biomedical implant with magnetic resonance imaging compatibility. Based on the experimental results, the possible relationship among alloying elements, microstructure and properties has been established in these Zr‐2.5Nb‐1X alloys.