School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, PR China.
School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, PR China.
J Mech Behav Biomed Mater. 2018 Apr;80:246-257. doi: 10.1016/j.jmbbm.2018.01.028. Epub 2018 Feb 2.
Magnesium and its alloys have unique advantages to act as resorbable bone fixation materials, due to their moderate mechanical properties and biocompatibility, which are similar to those of human tissue. However, early resorption and insufficient mechanical strength are the main problems that hinder their application. Herein, the effects of microstructure transformation on the mechanical properties and corrosion performance of Mg-Zn-Mn-Ca were investigated with electrochemical and immersion measurements at 37 °C in a simulated body fluid (SBF). The results showed that the number density of CaMgZn/MgCa precipitates was remarkably reduced and grain sizes were gradually increased as the temperature increased. The alloy that received the 420 °C/24 h treatment demonstrated the best mechanical properties and lowest corrosion rate (5.94 mm/a) as well as presented a compact and denser film than the others. The improvement in mechanical properties could be explained by the eutectic compounds and phases (MgCa/CaMgZn) gradually dissolving into a matrix, which caused severely lattice distortion and facilitated structural re-arrangement of the increased Ca solute. Moreover, the difference in potential between the precipitates and the matrix is the main essence for micro-galvanic corrosion formation as well as accelerated the dissolution activity and current exchange density at the Mg/electrolyte interface. As a result, the best Mg alloys corrosion resistance must be matched with a moderate grain size and phase volume fractions.
镁及其合金作为可吸收性骨固定材料具有独特的优势，因为它们具有中等的机械性能和生物相容性，与人体组织相似。然而，早期的吸收和不足的机械强度是阻碍其应用的主要问题。本文通过在 37°C 的模拟体液（SBF）中进行电化学和浸泡测量，研究了微观结构转变对 Mg-Zn-Mn-Ca 的机械性能和腐蚀性能的影响。结果表明，随着温度的升高，CaMgZn/MgCa 析出物的数密度显著降低，晶粒尺寸逐渐增大。经 420°C/24 h 处理的合金表现出最佳的机械性能和最低的腐蚀速率（5.94mm/a），并且具有比其他合金更致密和更密集的膜。机械性能的提高可以用共晶化合物和相（MgCa/CaMgZn）逐渐溶解到基体中来解释，这导致晶格严重变形，并促进了增加的 Ca 溶质的结构重排。此外，沉淀相与基体之间的电位差是微电偶腐蚀形成的主要本质，加速了 Mg/电解质界面的溶解活性和电流交换密度。因此，最佳的镁合金耐腐蚀性必须与适度的晶粒尺寸和相体积分数相匹配。
