【作者】 于善坤；

【导师】 丁雨田；

【作者基本信息】 兰州理工大学 ， 材料加工工程， 2010， 硕士

【摘要】 许多冠状动脉严重狭窄的冠心病患者,药物治疗不能有效逆转冠状动脉狭窄,需介入治疗或开胸搭桥手术,而介入治疗的优势在于既能有效解决冠脉狭窄,又能降低手术风险,目前,介入材料如钴合金,钛合金,不锈钢材料长期植入血管后可导致血管内膜增生,从而增加晚期血栓事件,而生物可降解聚乳酸等高分子材料,由于其血管支撑性能达不到要求,限制了这类材料的使用范围。为了解决上述材料存在的问题,本课题研发一种能够生物可降解稀土镁合金支架基体材料。本文以具有良好生物相容性的稀土镁合金为研究对象,设计了以Mg-Y-Zr(WY=4.2%,WZr=0.5%)为基体合金,研究了不同添加量Nd, Ce(La)稀土元素对其组织与性能的影响,制备出性能优良的Mg-4.2Y-2.4Nd-0.6Ce (La)-0.5Zr,即WE43合金,并系统研究了其铸态、热处理态及挤压态的显微组织结构、生物力学性能及断裂机制。WE43铸态显微组织结构观察发现,镁合金中添加适量的稀土元素Nd,Ce(La)具有良好细化晶粒作用,稀土相富集在晶界。合金经过T4处理热处理后,稀土元素固溶到a-Mg基体中,起到了固溶强化的作用；经T6热处理后,T6态合金的显微组织结构均匀,基体内析出大量弥散的Mg-Re相,时效强化效果明显,其生物力学综合性能得到较大提高,特别是高温下的延伸率比铸态时提高了近两倍多为13.5%。铸态合金经均匀退火后热挤压变形,结果发现,试样横截面组织发生了动态再结晶,晶粒更加细小,纵截面组织发生不完全动态再结晶,存在纤维组织和孪晶组织；挤压态经T6热处理后,合金发生完全再结晶,孪晶组织消失,第二相呈球状,沿挤压方向呈细条状分布,其生物力学性能抗拉强度进一步得到提高为270.2MPa。WE43合金的断裂机制由铸态的准解理断裂,至热处理态的趋向韧性断裂,再至挤压态及高温下的韧性断裂演变。本文对WE43合金的成分设计、熔铸、热处理工艺及挤压工艺作了细致的探究,论证了WE43合金可作为可控降解生物支架基体材料的生物力学相容性的可行性。更多还原

【Abstract】 For coronary heart disease patients with severe coronary artery stenosis, drug therapy can not effectively reverse the coronary arteries, so thoracic intervention or bypass surgery is required. And the advantage of interventional treatment is not only the effective solution to coronary stenosis but also the reduction of surgical risk. At present, the intervention materials such as cobalt, titanium, stainless steel may lead to vascular intimal hyperplasia and increase late thrombotic events after long-term implantation; and polymers such as biodegradable polylactic acid, due to their failure to meet the requirements of blood vessels supporting performance, the use of such materials is restricted. To address these material problems, this study has developed biodegradable magnesium alloy stent matrix material.This paper takes rare-earth-magnesium alloy with good biocompa-tibility as the subject of the study, and has adopted Mg-Y-Zr (WY=4.2%, WZr=0.5%) as the base alloy, analyze the influence of different amounts of Nd, Ce (La) Rare Earth Elements on microstructure and properties, and has prepared Mg-4.2Y-2.4Nd-0.6Ce (La)-0.5Zr (i.e.the WE43 alloy) with excellent performance.The study has also systematically analyzed the microstructure, biomechanical properties and fracture mechanisms of its cast, extruded and heat treatment state.According to the microstructure observation of WE43-cast,adding appropriate amount of rare earth elements Nd, Ce (La) into magnesium alloys can cause good grain refinement effect. The eutectic phase of rare earth gets enriched in the grain boundary. After T4 treatment, the rare earth element in the alloy solutes into the a-Mg matrix which strengthens the solid solution;after the T6 heat treatment, T6 condition alloy’s microstructure is uniform.Grains precipitate a large number of dispersed Mg-Re phase,the age strengthening effect is obvious,its biomechanics overall performance is greatly improved,especially the elongation at high temperature is raised Cast alloy is deformed by hot extrusion after even annealing.It is found that there is follows the three steps:quasi-cleavage fracture of cast state,tendency ductile fracture of heat treatment state,then ductile fracture of extruded state and under high temperature.This paper has made detailed inquiry about the composition design, casting, heat treatment and extrusion of WE43 alloy and demonstrated the feasibility of bio-mechanical compatibility that the WE43 alloy can be used as controllable.更多还原