医用层状结构镁合金的流变成型及梯度降解机理

.　Although a number of magnesium implant devices are admitted for clinical applications, structure failure induced by localized corrosion is still a primary practical problem to be overcome, which cannot be solved by traditional methods including alloying and surface treatment. The applicant designed a new multilayer magnesium alloy with positive corrosion potential gradient from surface, via which the alloy would homogeneously degraded during implantation period. The applicant has manufactured double-layer magnesium alloys by clad rheo-extrusion method, but there are still some crucial scientific problems in alloy design, processing mechanism, element gradient establishment and in vivo degradation mechanism. Therefore, to design and manufacture multilayer magnesium alloys and study their gradient degradation mechanism in vivo, the present proposal will focus on rheo-extruded multilayer structure Mg-Ag alloys treated by vibration system. After studying the reho-forming dynamics, solidification and evolution of micro-structure, establishment of element gradient and in vivo degradation mechanism, the theory on clad rheo-extrusion method for multilayer magnesium alloys would be established. Based on the study, techniques towards protection of localized corrosion via establishment of positive corrosion potential gradient from surface would be obtained, and structure failure induced by localized corrosion as a common practical problem would be solved.

.尽管多种医用镁合金植入器件已进入临床应用阶段，但仍面临局部腐蚀造成结构失效过快的应用难题，而传统的合金化和表面处理方法无法对局部腐蚀进行有效防护。申请人运用逆向思维，设计出腐蚀电位梯度向纵深趋正的层状结构镁合金材料，以实现逐层梯度降解的效果。前期研究使用复合流变挤压成型方法成功制备出双层结构镁合金材料，但在合金设计、成型机理、成分梯度构建、体内降解机理等方面仍存在关键科学问题需要解决。因此，为设计制备多层结构镁合金并研究其在植入环境下的梯度降解机理，本项目将经剪切振动耦合熔体处理后复合流变挤压成型的Mg-Ag层状结构合金作为研究对象。通过研究其流变成型动力学、凝固和组织演化机理、成分梯度构建和体内梯度降解机理，建立镁合金层状材料的复合流变挤压成型理论，获得通过构建材料纵深正向腐蚀电位梯度提高镁合金耐局部腐蚀性能的手段，解决因局部腐蚀造成镁合金植入器件结构失效过快的共性应用难题。.

尽管多种医用镁合金植入器件已进入临床应用阶段，但仍面临局部腐蚀造成结构失效过快的应用难题，而传统的合金化和表面处理方法无法对局部腐蚀进行有效防护。项目团队设计出具有腐蚀电位梯度的层状结构镁合金材料，以实现逐层梯度降解的效果。项目使用复合流变挤压成型方法成功制备出双层结构镁合金材料，针对合金设计、成型机理、成分梯度构建、体内降解机理等方面的关键问题进行研究。..项目以设计制备出多层结构镁合金并研究其在植入环境下的梯度降解机理为核心研究目标，以将流变熔体处理后复合流变挤压成型的层状结构镁合金作为研究对象。项目重点研究了其流变成型动力学、凝固和组织演化机理、成分梯度构建和体内梯度降解机理。通过项目研究解决了三个关键科学问题，即复合流变凝固条件下的熔体流体类型判据与本构关系、流变挤压及热处理对溶质分布与析出相的影响规律、层状结构镁合金界面区域合金元素分布对局部腐蚀的影响机理。项目最终成功揭示了剪切场作用下的熔体在复合界面的凝固和组织演化机理，建立了镁合金层状材料的复合流变挤压成型理论，获得了通过构建材料纵深正向腐蚀电位梯度提高镁合金耐局部腐蚀性能的手段，初步解决了因局部腐蚀造成镁合金植入器件结构失效过快的共性应用难题。项目的成果为医用镁合金植入器件的研发，以及功能镁合金器件的制备技术提供了新的研究思路和技术方法。