Shuiqing Liu

The application of zirconium alloy in nuclear reactors is supported by its excellent performance and corrosion resistance, but under the action of high-energy neutrons, the atoms in the lattice will change, resulting in the accumulation of lattice defects and the evolution of the microstructure, which not only affect the strength and shape of the material but also affect the tensile resistance, impact resistance and other mechanical properties of the zirconium alloy. Common industrial processes for the preparation of nuclear-grade zirconium sponges are discussed, the advantages, disadvantages and applications of the main production processes are summarised, and the characteristics of irradiation-induced loops are comprehensively examined, encompassing their formation mechanisms, interactions with dislocations, and the range of potential microscopic defects during irradiation. In addition, the phenomena of irradiation growth and irradiation creep and their relationship with microstructure evolution are also discussed. The effect of oxidative corrosion under irradiation has also been explored. Specifically, irradiation can aggravate the corrosion process of zirconium alloy and lead to the thickening of the corrosion layer, but the specific degree of influence is closely related to the working temperature and irradiation conditions. The comprehensive study of zirconium alloy under irradiation conditions aims to provide a scientific basis for the future design of long-life and high-reliability nuclear reactor materials and support the sustainable development of the nuclear industry.

In recent years, Zn and its alloys have become some of the most promising degradable metals as in vivo implants due to their acceptable biocompatibility and more suitable degradation rate compared with Mg-based and Fe-based alloys. However, the degradation rate of Zn-based materials after implantation in the body for orthopedic applications is relatively slow, leading to long-term retention of the implants after fulfilling their missions. Moreover, the excessive release of Zn²⁺ during the degradation process of Zn-based implants usually leads to high cytotoxicity and delayed osseointegration. To provide a feasible solution to the problem faced by Zn-based implants, a Zn-Ca composite was fabricated by an air pressure infiltration method in this work. The XRD pattern of the composite suggests that the composite is fully composed of Zn-Ca intermetallic compounds. The degradation tests in vitro show that the composite has a much higher degradation rate than pure Zn, and the high Ca content regions in the composite can preferentially degrade as sacrificial anodes. In addition, the composite can efficiently induce Ca-P deposition during immersion tests in Hank’s solution. Cytotoxicity tests indicate that L-929 cells exhibit around 82% cell viability (Grade 1) even after being cultured in the 100% extract prepared from the Zn-Ca composite for 1 day and show excellent cell viability.

Aluminum and its alloys are widely used in packaging, transportation, electrical materials, and many other fields because of their abundance, light weight, good mechanical properties, suitable corrosion resistance, excellent electrical conductivity, and other advantages. Grain refinement achieved by adding inoculant is important not only to reduce the segregation and thermal cracking of alloy castings but also to improve the mechanical properties of alloy castings. Therefore, fine equiaxed grain structure has always been one of the goals pursued by the aluminum alloy casting industry. For this reason, the selection and development of effective inoculants for aluminum alloy is a key technology in the aluminum processing industry. This paper summarizes the development history of inoculants for aluminum alloy, including Al-Ti-C, Al-Ti-B, Al-Ti, Al-Ti-B-(C)-Ce, Al-Sc, and the Fe-rich phase of Al-Si alloy. At the same time, the advantages and disadvantages of common inoculants are introduced and prospective future applications are reviewed.

By restricting the dilated deformation, surface modification can stimulate multiple shear banding and improve the plasticity of bulk metallic glasses (BMGs). Aimed at modifying the surface of BMGs by thin layers, a crystalline Ni coating with ultrafine grains was coated on the surface of a Ti-based BMG by electroless plating. With a thickness of about 10 μm, the prepared thin coating could effectively limit the fast propagation of primary shear bands and stimulate the nucleation of multiple shear bands. As a result, the compression plasticity of the coated Ti-based BMG was improved to about 3.7% from near 0% of the non-coated BMG. Except for a small amount of Ni coating was adhered to the BMG substrate after fracture, most of the coatings were peeled off from the surface. It can be attributed to the abnormal growth of some coarse grains/particles in local region of the coating, which induces a large tensile stress at the interface between the coating and the BMG substrate. It is suggested that, for electroless nickel plating, improving the adhesive bonding strength between the coating and the substrate has a better geometric restriction effect than simply increasing the thickness of the coating.

Magnesium-based bulk metallic glass matrix composites (BMGMCs) have better plasticity than the corresponding bulk metallic glasses (BMGs); however, their strength and density are often compromised due to the fact that the effective reinforcement phase is mostly plastic heavy metal. For lightweight SiC-particle reinforced BMGMCs, interface wettability and the sharpness of the particles often reduce the strengthening effect. In this work, SiC particles were coated with a thin Cu coating by electroless plating, and added to Mg₅₄Cu_26.5Ag_8.5Gd₁₁ melt in an amount of 5 wt % to prepare a BMGMC. The microstructure of the interface, mechanical behavior and fracture morphology of the BMGMC were studied by scanning electron microscopy and quasi-static compression testing. The results showed that the Cu coating improved the wettability between SiC and the matrix alloy without obvious interfacial reactions, leading to the dispersion of SiC particles in the matrix. The addition of Cu-coated SiC particles improved the plastic deformation ability of Mg₅₄Cu_26.5Ag_8.5Gd₁₁ BMG, proving that electroless plating was an effective method for controlling the interface microstructure and mechanical behavior of BMGMCs.

Mg-Zn-Ca metallic glass (MG) is effective for degrading azo dyes; however, the related surface evolution and degradation mechanisms are little known. We comparatively investigated the initial surface corrosion morphologies of melt-spun Mg₆₆Zn₃₀Ca₄ MG in deionized water and artificial seawater. It was found that the basic corrosion behavior of the MG was the same, except that the corrosion process was accelerated in seawater. The presence of NaCl obviously promotes the formation of nano-ZnO on the surface of ribbons, causing the rapid degradation of azo dyes due to the photocatalytic effect. The degradation efficiency when combined with 3.5 wt % NaCl was over 100 times higher than that without NaCl. This indicates that Mg-Zn-Ca MG ribbons are effective additives for the degradation of azo dyes in seawater.

This paper deals with a novel fabrication method (a vacuum rapid solidification technique) to prepare in situ Ti₅Si₃/Ti composite ribbon as inoculants to modify Ti6Al4V alloy to obtain titanium matrix composites (TMCs). Microstructure and morphology observations showed that the grain size of the TMCs was refined as the volume fraction of inoculants increased. The grain size of the TMCs can be refined from a grade of 650 μm to about 110 μm with a very small refiner adding ratio of 0.6% in weight. Thereafter, the mechanical properties of the TMCs, including their tensile strength, microhardness, impact properties, and resistant properties were improved obviously by adding the ribbon inoculants. The excellent grain refining and reinforcement effect can be attributed to the nano-sized Ti₅Si₃ refiner particles distributed homogeneously in the matrix, the well-banded particle/matrix interface, and the good wettability between the Ti₅Si₃ particles in inoculants and the Ti6Al4V alloy melt, which are benefit for the heterogeneous nucleation of the TMCs during solidification.

Melt spinning was performed to process an in situ CeB₆/Al inoculant at different rotating speeds to investigate the influence of cooling rate on the grain refining behavior of inoculants. It has been found that a high cooling rate caused two obvious changes in the inoculant: the supersaturated solid solution of Ce in the α-Al matrix and the miniaturization of CeB₆ particles. At high cooling rates of ~10⁸ K/s, the Ce content is largely beyond the theoretical solid solubility of Ce in Al, and the size of the CeB₆ particles in ribbons is reduced to ~100 nm. The grain refining effect of melt-spun CeB₆/Al composite inoculant shows significant dependence on holding time of which the best value should be no more than 2 min. The excellent grain refinement of the inoculant can be attributed to the combined effect of the nano-sized refiner particles and the large undercooling caused by the sudden melting of supersaturated Al–Ce solution.