Yanying Hu

Bio: Yanying Hu is an academic researcher from Sun Yat-sen University. The author has contributed to research in topics: Friction stir welding & Welding. The author has an hindex of 3, co-authored 11 publications receiving 35 citations. Previous affiliations of Yanying Hu include Harbin Institute of Technology.

Comparative study on the tensile cracking behavior of CrN and Cr coatings for accident-tolerant fuel claddings

Abstract: In this work, a comparative study was conducted on the tensile behaviors of two representative accident-tolerant cladding coatings, i.e., CrN coating and Cr coating, at both room temperature and 400 °C by in situ tensile testing. The surface and interfacial cracking behaviors of the coatings were experimentally tested and analyzed, with the surface crack densities predicted by a modified shear-lag model. The results showed that CrN coating exhibited brittle fracture at both room temperature and 400 °C, while the failure of Cr coating showed brittle-to-ductile transition when increasing the temperature from room temperature to 400 °C. Moreover, Cr coating exhibited better crack resistance than that of CrN coating under mechanical loading at both temperatures, due to: (i) the higher fracture toughness and ductility of Cr; (ii) better deformation compatibility between Cr coating and Zr-4 substrate. In particular, at 400 °C, Cr coating with excellent plastic deformability exhibited a protective or prohibitive effect on the crack initiation process of the Zr-4 substrate. It is indicated that the mechanical deformation properties and failure mechanisms of Cr and CrN coatings are important factors that should be considered in the selection and evaluation of accident-tolerant coatings.

Achievement of high-strength 2219 aluminum alloy joint in a broad process window by ultrasonic enhanced friction stir welding

Abstract: High-strength joints are required to suit a more and more wide industrial application of friction stir welding (FSW). However, the achievement of high-strength joints is generally confined within a narrow process window due to the significant dependence of material plastic deformation on welding parameters. In the present study, ultrasonic enhanced friction stir welding (UFSW) was proposed as a strategy to broaden the process widow for achieving high-strength joints. The results indicated that the tensile strength of UFSW joint only slightly fluctuated around 355–361 MPa, indicating a stable joint efficiency of 81%–82%, even though the welding speed was increased from 300 mm/min to 600 mm/min at a constant rotation speed of 800 rpm. Acoustoplastic effect of the ultrasonic contributes to sufficient plastic deformation of the materials in the stir zone (SZ) and thus welding defects were successfully avoided. With the welding speed increasing, the widths of SZ can stabilize at 4.7 mm in the middle and 3.3 mm in the bottom, respectively. Furthermore, ultrasonic improved the SZ strength by enhancing precipitation strengthening and thus the fracture position was located in the TMAZ. Coarsening of precipitates in the TMAZ cannot make prominent contributions to the resultant strength, leading to a stable joint efficiency of 81%–82%.

Recent Advances in Protective Coatings for Accident Tolerant Zr-Based Fuel Claddings

Abstract: Zirconium-based alloys have served the nuclear industry for several decades due to their acceptable properties for nuclear cores of light water reactors (LWRs). However, severe accidents in LWRs have directed research and development of accident tolerant fuel (ATF) concepts that aim to improve nuclear fuel safety during normal operation, operational transients and possible accident scenarios. This review introduces the latest results in the development of protective coatings for ATF claddings based on Zr alloys, involving their behavior under normal and accident conditions in LWRs. Great attention has been paid to the protection and oxidation mechanisms of coated claddings, as well as to the mutual interdiffusion between coatings and zirconium alloys. An overview of recent developments in barrier coatings is introduced, and possible barrier layers and structure designs for suppressing mutual diffusion are proposed.

Grain size effect on tensile deformation behaviors of pure aluminum

Abstract: Grain refinement is a very effective method to improve the mechanical properties of materials and attracts widespread interests among researchers. However, the grain size effect on the mechanical properties is still unclear due to the undesirable microstructure in ultrafine grained (UFG) materials. In the present work, series of ideal materials with average grain sizes range from 0.7 μm to 30.0 μm containing high fraction of high angle grain boundaries (HAGBs), equiaxed grains and low density of dislocations were produced by friction stir processing (FSP). It was found that the Hall-Petch relationships could be classified into three stages as the grain size reduced from coarse grain to UFG regimes, which were decided by the strengthening mechanisms during tensile deformation. The strengthening effect of HAGBs (71 MPa ⋅ μm1/2) was almost three times of low angle grain boundaries (25 MPa ⋅ μm1/2), resulting in the positive deviation of Hall-Petch slope in fine grain regime by the increased specific surface area of HAGBs. The further positive deviation of the Hall-Petch slope in UFG regime was affected by the occurrence of an extra dislocation source limited strengthening mechanism, which was up to 29 MPa and reached to about 20% of the yield strength. The increased recovery rate of dislocations at HAGBs contributed to the decrease of mobile dislocation density, leading to the losing of work hardening in UFG regime during tensile deformation.