基于应变诱导晶粒细化的亚微/纳米级LZE系镁合金心血管支架制备原理及应用基础研究

Due to excellent biological safety, high specific strength and degradability, LZE series Mg alloy is a new material with great potential in the field of cardiovascular stent. While, to improve corrosion resistance and plasticity by using grain refinement is significant for enlarging application range in the field of cardiovascular stent. In this project, atomization-twin rolls quenching technology will be used to prepare LZE series Mg alloy. Then, grains will be segmented by a great mount of twins produced with multiple accumulated deformation process, and submicro/nanosized grains could be obtained. By investigating the evolution of microstructure and mechanical properties, the icroscopic mechanism and the related influence factors for RS technology could be explored. Then, the evolution characteristics of twinning type and amount for rapid solidified Mg alloy with different texture in the following multiple accumulated deformation process will be explored and the influence for twinning generation and growth will be revealed. The effect of twinning segmentation can be carefully evaluated and the regulation mechanisms and feature of twinning will also be generalized. Based on these experimental results, in order to discuss the degradation controllability and corrosion resistance of LZE series Mg alloy, the vitro degradation behavior of the alloy in the process of RS and strain induced grain refinement will be researched and the effect of the main parameters will also be discussed. It is.believed that the research can be used to furthest improve plasticity and corrosion resistance, as well as provide theoretical and technical support for the application of the alloy in the field of cardiovascular stent.

LZE系镁合金由于生物安全性高、比强度高和可降解性等优点，是心血管支架领域颇具应用潜力的新型材料。通过细化晶粒来提高该合金的耐腐蚀性和塑性变形能力是扩大其在心血管支架领域应用的关键问题。本项目拟采用雾化双辊急冷工艺制备快速凝固LZE系镁合金，并利用多道次累积变形的办法产生大量孪晶来分割细化晶粒，以便获得平均晶粒尺寸亚微/纳米级的心血管支架用LZE系镁合金。在此过程中，通过探究微观组织和力学性能变化规律，分析该合金快速凝固原理及影响因素；探索不同织构类型的快速凝固镁合金多道次累积变形时的孪晶类型和孪晶数量变化规律，揭示LZE系合金中孪晶产生及演变的演变机理。研究结果可为最大限度地挖掘该合金的塑性变形能力和耐腐蚀性能，实现该合金在心血管支架领域的应用提供理论和技术支撑。

镁合金凭借其比强度高、生物安全性高、可降解性和优良的力学相容性，已成为心血管支架、骨固定材料等领域一个非常活跃的研究热点。Mg-Li-Zn-RE合金（LZE系）中，由于Li、Zn的引入使合金塑性有明显改善，Zn和稀土元素还有助于提高合金的耐腐蚀性；且该合金的降解产物Li+、Zn2+、Mg2+离子是人体必须的微量元素，生物安全性高。目前镁合金心血管支架应用中最主要的两个问题是：合金塑性变形能力差和耐腐蚀性有待提高。晶粒细化是公认同时解决上述两个问题最有效的途径之一。如能将合金晶粒普遍细化至亚微/纳米级，则对大幅度提高合金综合性能极其重要。基于此问题，项目首先自制了快速凝固设备。并通过多次改进该设备，制备出了经过雾化双辊急冷后的LZE系合金。在多次试验后，改进了合金的熔炼及快速凝固工艺，研究了该合金加工的微观控制机制。随后利用多道次累积变形的办法初步产生了孪晶来分割细化晶粒，获得了平均晶粒尺寸小于1μm的镁合金。于此同时，通过hanks体液中的体外降解行为观察，对快速凝固后的镁合金进行综合分析，为提高该合金降解行为可控性打下基础。结果发现，该镁合金的耐蚀性与常规镁合金的生物耐蚀性相似。综合快速凝固、塑性变形中微观组织、力学性能和体外降解行为的变化，初步揭示了该合金快速凝固+应变诱导晶粒细化的控制机理。