University of Tennessee at Chattanooga, 615 McCallie Ave, Chattanooga, TN 37403, USA.
Department of Materials Science and Engineering, The Ohio State University, 460 West 12th Avenue, Columbus, OH 43210, USA.
Mater Sci Eng C Mater Biol Appl. 2019 Oct;103:109700. doi: 10.1016/j.msec.2019.04.079. Epub 2019 May 2.
While potentially strong enough for load-bearing skeletal reconstruction applications, the corrosion (biodegradation) rate of biocompatible Mg-Zn-Ca-based alloys still presents. The present work reports on the use of heat treatment (strengthening and resorption delaying) and micro arc oxidation (MAO) coating (corrosion delaying) processes which were developed to induce desirable corrosion rates which are essential to maintaining the mechanical integrity of Mg-Zn-Ca-based alloys during the bone healing period. Three Mg-x%Zn-0.5%Ca (wt%) alloys with different levels of Zn content (1.2, 1.6 and 5 wt%) were prepared and heat-treated at different age hardening temperatures (100, 150, 200 and 250 °C). In order to further decrease the corrosion rate and improve the bioactivity, samples of the heat-treated Alloy I (Mg-1.2wt%Zn-0.5wt%Ca) at the optimized age-hardening conditions were successfully coated with a biocompatible composite coating without and with HA/β-TCP nanoparticles by using an MAO process. The microstructure, morphology and the composition of the heat-treated and coated materials were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and x-ray diffraction (XRD). Hardness and compression tests were conducted, while a corrosion investigation of heat-treated and coated samples was performed using potentiodynamic polarization (PDP) and a mechanical integrity immersion test. The results confirmed that Zn content and age hardening temperature have significant effects on the mechanical and corrosion properties of heat-treated Mg-Zn-Ca-based alloys. Alloy I, which has 1.2 wt% Zn content and was aged at 200 °C, showed the best combination of corrosion (slowest) and mechanical (highest) properties. The MAO (HA/β-TCP) composite coating significantly improved corrosion resistance compared to the uncoated heat-treated alloy, with only 11.3% reduction in the compressive strength after 8 weeks of immersion.
虽然生物相容性 Mg-Zn-Ca 基合金具有足够的强度用于承重骨骼重建应用，但仍存在腐蚀（生物降解）问题。本研究报告了热处理（强化和延缓吸收）和微弧氧化（MAO）涂层（延缓腐蚀）工艺的应用，这些工艺的开发是为了诱导理想的腐蚀速率，这对于维持 Mg-Zn-Ca 基合金在骨愈合期间的机械完整性至关重要。本研究制备了三种不同锌含量（1.2、1.6 和 5wt%）的 Mg-x%Zn-0.5%Ca（wt%）合金，并在不同时效硬化温度（100、150、200 和 250°C）下进行了热处理。为了进一步降低腐蚀速率并提高生物活性，对在最佳时效硬化条件下热处理的合金 I（Mg-1.2wt%Zn-0.5wt%Ca）进行了进一步处理，通过 MAO 工艺成功地在没有和有 HA/β-TCP 纳米颗粒的情况下涂覆了生物相容性复合涂层。通过扫描电子显微镜（SEM）、能谱（EDS）和 X 射线衍射（XRD）对热处理和涂层材料的微观结构、形貌和组成进行了表征。对热处理和涂层样品进行了硬度和压缩试验，同时通过动电位极化（PDP）和机械完整性浸泡试验对热处理和涂层样品的腐蚀情况进行了研究。结果表明，锌含量和时效硬化温度对热处理 Mg-Zn-Ca 基合金的力学性能和腐蚀性能有显著影响。含有 1.2wt%锌且在 200°C 时效的合金 I 表现出最佳的腐蚀（最慢）和力学（最高）性能组合。MAO（HA/β-TCP）复合涂层与未经处理的热处理合金相比，显著提高了耐腐蚀性，浸泡 8 周后压缩强度仅降低 11.3%。
