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A novel fluorine-free and silicon-free superhydrophobic aluminum alloy (treated-Al) is fabricated by chemical etching using hydrochloric acid and hydrogen peroxide and modified with an organic carbon dot (OCD) coating. The water contact angle (CA) of the treated-Al surface increases with the OCD concentration. When etched aluminum (etched-Al) is modified with 0.5 mg/ml OCDs, a CA of 161.4° is achieved, which indicates good nonwettability. SEM results verify that porous microstructures with cavities are uniformly distributed on the surface of etched-Al, in contrast to the bare aluminum alloy, which forms a primary rough structure. After treatment with 0.5 mg/ml OCDs, a nanoparticle coating is dispersed on the rough structures of treated-Al-0.5, which can trap air and make a water droplet essentially rest on a layer of air. The treated-Al-0.5 material has good self-cleaning properties and can sweep away contaminants at both 20 and 0°C. The Ecorr and Icorr of treated-Al-0.5 are − 0.56 V and 2.82 × 10−6 A/cm2, respectively, which shows good anticorrosion performance.

Magnesium alloys were considered to be used as biodegradable implants due to their biocompatibility, biodegradability and nontoxicity. However, under the simultaneous action of corrosive environment and mechanical loading in human body, magnesium alloys are easy to be affected by corrosion fatigue and stress corrosion cracking. In this work, the fatigue behavior of the extruded Mg–Zn–Y–Nd alloy used for vascular stents was studied both in air and in simulated body fluid (SBF). It was revealed that the fatigue limit of as-extruded Mg–Zn–Y–Nd alloy in air is about 65 MPa at 107 cycles, while there is no limit in SBF and shows a linear relationship between the fatigue life and stress amplitudes. The fatigue crack source in air was formed by the inclusions and defects. However, the stress corrosion and hydrogen embrittlement are the main reasons for the formation of the fatigue initial crack source in SBF. Keywords: Biodegradable magnesium alloy, Corrosion fatigue, Simulated body fluid, Fatigue crack source

Mg alloys, as a new generation of biodegradable bone implant materials, are facing two tremendous challenges of enhancing strength and reducing degradation rate in physiological environment to meet clinical needs. In this study, tricalcium phosphate (β-TCP) particles were dispersed in Mg–2Zn–0.46Y–0.5Nd alloy by friction stir processing (FSP) to produce Mg-based functional gradient materials (Mg/β-TCP FGM). On the surface of Mg/β-TCP FGM, the hydroxyapatite (HA) coating was prepared by electrodeposition. The effects of FSP and electrochemical parameter on the microstructure, microhardness, bonding strength and corrosion performance of the Mg/β-TCP FGM were investigated. After four passes of FSP, a uniform and fine-grained structure was formed in Mg/β-TCP and the microhardness increased from 47.9 to 76.3 HV. Compared to the samples without β-TCP, the bonding strength of the Mg/β-TCP FGM increased from 23.1 ± 0.462 to 26.3 ± 0.526 MPa and the addition of degradable β-TCP contributed to the in situ growth of HA coating. The thickness of HA coating could be dominated by controlling the parameters of electrodeposition. According to the results of immersion tests and electrochemical tests in simulated body fluid, it indicated that the degradation rate of the Mg/β-TCP FGM could be adjusted.