Chengwen Tan

The Al-Ta energetic structural material (ESM) has significant potential for applications in energetic fragments. To rationally design the hot isostatic pressing (HIP) process for Al-Ta, this paper developed a novel parameter identification method for the modified Drucker–Prager Cap (DPC) model. The identified parameters were subsequently applied to simulate the densification behavior of Al/Ta mixed powders during HIP. Based on the simulation results, the HIP process parameters for fabricating the Al-Ta ESM were determined. Meanwhile, the microstructure, mechanical properties, and impact-induced reaction characteristics of the HIP-fabricated Al-Ta ESM were further analyzed. The main results are as follows. The comparison between the HIP simulations and experiments revealed good agreement, confirming the high accuracy of the identification of the modified DPC model parameters. In addition, the Al-Ta ESM fabricated via HIP at 460 °C/140 MPa/2 h exhibits a dense microstructure and enhanced mechanical properties. Furthermore, it demonstrates effective damage performance during the penetration of double-layered targets.

Binary magnesium‐silver (Mg‐Ag) alloys were designed as antibacterial materials for biomedical implant applications. In the present study, we focused on the effects of extrusion (extrusion ratio (ER): 1, 7.1, and 72.2) and Ag content (Ag = 0, 3, and 6 wt.%) on the degradation of Mg‐Ag alloys in vitro and in vivo via microstructure characterization and corrosion/degradation measurements. The results showed that the Ag promoted a galvanic reaction with the Mg matrix to accelerate degradation or formed a protective oxide mesh texture to inhibit degradation, especially in vivo. Ag might also be beneficial for product crystallization, biomineralization, and organic matter deposition. For pure Mg, extrusion produced a more refined grain and decreased the degradation rate. For the Mg‐Ag alloys, a low extrusion ratio (7.1) accelerated the degradation caused by the increase in the proportion of the precipitate. This promoted the release of Mg²⁺ and Ag⁺, which led to more deposition of organic matter and calcium phosphate, but also more H₂ bubbles, which led to disturbance of product deposition in some local positions or even inflammatory reactions. Extrusion at a higher ratio (72.2) dissolved the precipitates. This resulted in moderate degradation rates and less gas production, which promoted osteogenesis without an obvious inflammation reaction.

Tantalum coating for bio-medical applications is prepared by atmospheric pressure chemical vapour deposition in a TaF₅–H₂ system on the inner wall of a stainless steel tube. The concentration of hydrogen fluoride (HF) has a significant effect on the morphology and crystallographic orientation of the tantalum coating. As the HF concentration increases, the tantalum coating gradually becomes smooth from roughness. The rougher part and the smoother part of tantalum coating reveal (200) and (110) preferred orientation, respectively. Simultaneously, the kinetic equation containing HF concentration has been developed. The calculated results from the equation show a good correspondence with the experimental results. The performance of tantalum coating with distinct morphologies on the effect of osseointegration was studied by implanting samples in vivo. The coating with a rougher surface was more osteoattractive than the one with a smoother surface.

Porous tungsten (W) is used in aeronautic and aerospace engineering, power electronics field and metallurgical industry. In this study, porous W with 98wt% W was prepared on a carbon foam substrate by atmospheric-pressure chemical vapor deposition (CVD) with tungsten fluoride (WF6) as the precursor. The porous W with 78.1346% porosity displayed a pure α-W phase and the uniform surface. The mode pore diameter of porous W is 208.0 µm. In a compression test, the fracture strength of porous W is 20.3 MPa.

Tungsten carbide / tungsten coating is prepared from tungsten hexafluoride (WF6), hydrogen (H2) and dimethyl ether (DME) mixtures by chemical vapor deposition (CVD) under atmospheric pressure conditions. The cross-sectional structure and the surface morphology of the coating were observed using optical microscope and scanning electron microscopy. It is found that the tungsten layer is columnar and tungsten carbide / tungsten coating is fine grain lamellar structure. The preferential growth of tungsten was proposed to be effect of DME, and the {100} preferred orientation gradually disappeared by XRD. That the pre-deposition of tungsten on the substrate can improve the coverage of the tungsten carbide coating was observed. Finally, the cross section of the micrograph was measured at 28.77 GPa with a nano-indentation.