Xiaofeng Wan

Magnesium alloys are promising biodegradable implants, but rapid degradation and insufficient early-stage bioactivity limit their clinical use. In this study, hydroxyapatite (HA)/zirconia (ZrO₂)/niobium (Nb) composite coatings with varying Nb contents (10, 20, and 30%) were deposited on ZK60 magnesium alloys via atmospheric plasma spraying. The coatings retained feedstock phases while forming tetracalcium phosphate, tricalcium phosphate, and Nb₂O₅ during spraying. Microstructurally, increasing Nb to 30% induced an interconnected porous network, resulting in increased surface microhardness (~426 HV) and hydrophilicity (contact angle ~50°). Electrochemical tests revealed that, among the investigated compositions, the 20% Nb coating exhibited the lowest corrosion current density (I_corr = 9.688 × 10⁻⁵ A/cm²), indicating the most favorable electrochemical behavior within the tested Nb-content range. Although further increasing Nb to 30% resulted in a higher I_corr than that of the 20% Nb coating, H1Z3N exhibited the highest day-5 OD450 value and favorable cell spreading. This cellular response may be associated with its higher surface roughness, enhanced wettability, and porous architecture. Overall, the investigated compositions exhibited an observed trade-off between electrochemical behavior and cytocompatibility.

This study conducted a systematic investigation on how Ca content affected Mg-6Al-1Sn alloys as anodes for Mg-air batteries in terms of their microstructure, electrochemical corrosion behavior, and discharge performance. According to the investigation results, incorporating Ca induces the formation of blocky β-Mg₁₇Al₁₂ phases containing Ca and refines the grain structure. Compared to Mg alloys without Ca, the alloys with Ca exhibit significantly improved self-corrosion resistance because the preferential enrichment of Ca at the grain boundaries within β-Mg₁₇Al₁₂ phases reduces the potential difference between β-Mg₁₇Al₁₂ phases and Mg matrix. Consequently, galvanic corrosion is mitigated, together with the effective suppression of the self-corrosion reaction of Mg anodes. Additionally, Mg alloy shows a higher anode utilization efficiency with Ca content. The combined results indicate that Mg-6Al-1Sn-0.5Ca alloy exhibits superior self-corrosion resistance and discharge properties vs. other tested compositions. Furthermore, the Mg-air battery using Mg-6Al-1Sn-0.5Ca alloy as the anode demonstrates a heavier average discharge potential and a utilization efficiency of 71.12%, which is 7.56% higher than Mg-6Al-1Sn alloy.

Niobium (Nb) and zirconium dioxide (ZrO₂) were doped into hydroxyapatite (HA) to fabricate HA-based composite coatings prepared on a ZK60 magnesium alloy by plasma spraying technology to improve anti-corrosion and biocompatibility for clinical applications. The results revealed that the Nb-enriched coating exhibits fewer cracks and pores with a flat surface due to the decreased temperature gradient during spraying, and small needle-like structures can fill the cracks and pores in the ZrO₂-contained coating, resulting in a more uniform and dense surface. Compared to coatings with only niobium or zirconium dioxide, the ZrO₂/Nb/HA composite coating significantly enhanced the mechanical properties and corrosion resistance of the magnesium alloys. Among all the specimens, the ZrO₂/HA coating and ZrO₂/Nb/HA coating revealed high surface hardness values (327.73 HV and 293.80 HV, respectively). However, the higher hardness value made the ZrO₂/HA coating fragile and more likely to crack, while the ZrO₂/Nb/HA coating avoided this shortcoming and exhibited a more comprehensive performance. During immersion tests, the ZrO₂/Nb/HA coating exhibited a gradual pH increase and minimal mass loss, and the cytocompatibility test demonstrated promising cellular activity.

High-entropy alloys (HEAs) have emerged as a novel class of materials with exceptional mechanical and corrosion properties, offering promising applications in various engineering fields. However, optimizing their performance through advanced manufacturing techniques, like laser cladding, remains an area of active research. This study investigated the effects of laser energy density on the mechanical and electrochemical properties of CoCrFeMnNi HEA coatings applied to Q235 substrates. Utilizing X-ray diffraction (XRD), this study confirmed the formation of a single-phase face-centered cubic (FCC) structure in all coatings. The hardness of the coatings peaked at 210 HV with a laser energy density of 50 J/mm². Friction and wear tests highlighted that a coating applied at 60 J/mm² exhibited the lowest wear rate, primarily due to adhesive and oxidative wear mechanisms, while the 55 J/mm² coating showed increased hardness but higher abrasive wear. Electrochemical testing revealed superior corrosion resistance for the 60 J/mm² coating, with a slow corrosion rate and minimal passivation tendency in contrast to the 55 J/mm² coating. The comprehensive evaluation indicates that the HEA coating with an energy density of 60 J/mm² exhibits exceptional wear and corrosion resistance.

The Schmid factor (SF) is a critical parameter in crystal plasticity research that is often used to evaluate the level of difficulty in activating the slip systems within a grain. The evolution process and change mechanism of SF in 316 austenitic stainless steel during plastic deformation were investigated in this paper by using the in situ electron backscatter diffraction (EBSD) technique. The results showed that the average Schmid factor of global grains was highest in the original state, but after stretching, multiple rotation paths appeared in the grain, and the SF presented a monotonically decreased tendency with the increase in plastic strain degree. Numerical computation revealed that the decrease of SF was mainly governed by the change in φ angle, i.e., the angle between loading direction and slip plane normal increased inside the grains after the lattice rotation, which caused the slip plane to move parallel to the loading direction. The higher φ, the lower its cosine, which corresponds to low shear stress acting on the slip plane and could increase the difficulty of crystal slip.

The effect of Y₂O₃ addition on the microstructure and properties of the laser cladded Al-Si alloy coating on the surface of AZ91D magnesium alloy was investigated in this study. The experimental results showed that the Al-Si + Y₂O₃ cladding layers contained α-Mg, Mg₂Si, Al₄MgY and a small amount of Al₁₂Mg₁₇ phases. The coarse dendrites, reticulated eutectic structures and massive phases in the coatings tended to be refined and gradually uniformly distributed with the increased amount of Y₂O₃. The introduction of Y₂O₃ into the cladding layer favored the improvement of microhardness and wear resistance due to the grain refinement strengthening and dispersion strengthening. The addition of Y₂O₃ also promoted the reduction of localized corrosion sites and made the corrosion surface smoother, implying that the corrosion resistance of the Y₂O₃-modified coatings was better than that of the unmodified cladding layer.

By applying the orthogonal test, the T6 heat treatment test of the casting AlSi10MgMn alloy was carried out. Hardness, tensile strength, and elongation were selected as indicators for evaluating the toughness of alloy. Grey relational analysis was used to comprehensively evaluate the toughness of the alloy. Based on multiple linear regression, prediction models of hardness, tensile strength, elongation, and grey correlation were established. Through planning and solving, the optimal T6 heat treatment process parameters were obtained. According to the results of the metallographic structure analysis and the fracture SEM on the alloy after the T6 heat treatment, aging time, solution time, and solution temperature were identified as the most important factors affecting alloy hardness, tensile strength, and elongation, respectively. Through the application of grey relational analysis, the optimal T6 heat treatment process of an AlSi10MgMn alloy was obtained, namely 530 °C/1 h + 190 °C/6 h. Based on the solving of the prediction models, the optimal T6 heat treatment process and solution temperature of AlSi10MgMn alloy were obtained, namely 530 °C/3 h + 190 °C/8 h. Under these conditions, the hardness of the alloy was 96.9 HV, the tensile strength was 344.6 MPa, and the elongation was 6.1%. In contrast, the toughness of the alloy was better than that obtained by grey relational analysis. The T6 heat treatment refined the microstructure of the alloy, which resulted in a significant increase in fracture dimples.