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標題: | 熱處理對可降解鎂合金ZK60腐蝕行為與機械性質之影響 Effects of Heat Treatment on Corrosion Behavior and Mechanical Properties of Biodegradable ZK60 Magnesium Alloy |
作者: | Chih-Cheng Li 李至晟 |
指導教授: | 蕭浩明(Hao-Ming Hsiao) 蕭浩明(Hao-Ming Hsiao | hmhsiao@ntu.edu.tw | ), |
關鍵字: | ZK60鎂合金,熱處理,抗腐蝕力,機械性質, ZK60 Magnesium alloy,Heat treatment,Corrosion resistance,Mechanical property, |
出版年 : | 2022 |
學位: | 碩士 |
摘要: | 隨著心血管疾病成為全球人口的主要死因之一,心導管手術已成為心血管疾病的主要治療方式,支架在血管中可以有效的支撐血管,然而支架置入的後期有晚期血栓形成的風險。因此,生物可吸收式血管支架便因應而生,它可在完成階段性的任務之後,隨即被人體吸收降解,有望成為未來治療心血管疾病的技術。鎂合金有與骨隨相似的性質與良好的生物相容性,是生物可吸收材料的潛力材料之一,但也因其活性高造成降解快速,在傷口癒合前就已經被吸收分解,無法達到治療心血管疾病的需求。因此本研究以ZK60鎂合金為材料,透過三種不同的熱處理方法(T4、T5、T6)以提升ZK60的抗腐蝕力與機械性質,期望能達到臨床上的需求。本研究利用腐蝕實驗了解材料的降解速率與腐蝕行為,利用拉伸試驗了解材料的機械性質。最後,製作支架雛型品做腐蝕驗證與有限元素方法模擬做力學分析。 研究結果中腐蝕實驗T4抗腐蝕性相對明顯提升25%,而T5與T6僅小幅的提升15%與5%,結果表明熱處理雖然有改善抗腐蝕的能力,但都沒有達到臨床上降解速率的要求,但腐蝕行為卻有明顯得到改善。在機械性質方面,T5與T6的降伏強度只有些微降低3%,而T4卻大幅下降13%。除了熱處理外,也進行電解拋光對表面做初步的處理,使表面粗糙度得到進一步的改善。在驗證中,支架雛型品的腐蝕行為與實驗結果相同外,但還多了應力腐蝕的表現,在應力集中處有較高的腐蝕速率。機械性質方面,徑向力模擬與拉伸試驗有大致相同的趨勢,T4徑向力減少約20%,T5與T6減少約10%,而回彈率都沒有太大的差別。整體比較下,T4有最好的抗腐蝕力,但機械強度大幅減少,需透過支架設計的方式提升徑向強度。而T5可以些微改善抗腐蝕能力,也擁有適當的機械強度,並大幅改善了材料的腐蝕行為,因此本研究會推薦以T5的熱處理方法進行材料改性。 本研究沒有進行電解拋光與應力存在的情形下做腐蝕驗證,但推測兩者皆能明顯改善抗腐蝕能力,電解拋光可以改善材料表面的缺陷大幅減少局部腐蝕的發生。在應力存在的方面,因未經熱處理的材料表面會全面的點蝕,造成支架支撐結構的弱化提升支架斷裂的風險。而熱處理後的腐蝕是較局部的孔蝕,僅會造成支架局部的腐蝕,仍可保有相當的支撐結構,因此有相對較小的血管支架斷裂的風險。本研究提供了生物可吸收式材料不同的材料處理方法,並提出熱處理改變ZK60鎂合金的抗腐蝕性能與機械性質,有望成為改善可降解血管支架抗腐蝕性能的方法。 As cardiovascular diseases have become one of the leading causes of death in the global population, vascular stent has become the main choice of treatment, since the device can effectively support blood vessels. However, the increasing risk of late stent thrombosis after stent implantation has become an important issue in the medical field. Therefore, bioresorbable vascular stent is the answer to the problem, which is absorbed and degraded by the body after completing its designated task. It is expected to become the future preferable treatment for cardiovascular diseases. Magnesium alloy has similar properties with bone as well as good biocompatibility, to serve as a potential bioresorbable material, despite its rapid degradation due to its high reactivity, which may cause it to be absorbed or degraded before wound healing, so it cannot fully satisfy the demand of treating cardiovascular diseases. Thus, this study would use ZK60 magnesium alloy as the material to improve the corrosion resistance and mechanical properties of the metal through three different heat treatment methods(T4、T5、T6), hoping to achieve the clinical requirements. In this study, the corrosion experiment was conducted to understand the rate of degradation and the behavior of material under corrosion. On the other hand, the tensile experiment was designed to understand the mechanical properties after heat treatment. Finally, the prototype of the stent made of the alloy was verified of its corrosion resistance and analyzed of its mechanical strength by finite element simulation. In the research results, the corrosion experiment showed that T4 relatively significantly increased by 25%, while T5 and T6 only slightly increased by 15% and 5%, respectively. The results showed that although heat treatment had the ability to improve corrosion resistance, it did not meet the requirements of clinical degradation rate. In terms of mechanical properties, the yield strength of T5 and T6 only slightly reduced by 3%, while T4 significantly decreased by 13%. In addition to heat treatment, electrolytic polishing was also performed to make preliminary surface treatment to greatly improve surface roughness. For verification, the stent prototype showed similar corrosion behavior as the experimental results, but there was more stress corrosion happening, especially stress concentration of the stent. Mechanically the radial force under simulation and the tensile experiment were approximately the same. The radial force of T4, T5 and T6 respectively decreased by 20%, 12%, 10%, and expansion recoil is only slight difference. In overall comparison, T4 had the best corrosion resistance, but the mechanical strength was greatly reduced, and the radial force must be reinforced by stent design. On the other hand, T5 slightly improves its corrosion resistance and shows adequate mechanical strength and great improvement to the corrosion behavior. Thus, this study concludes with a recommendation of T5 heat treatment for material modification. However, this study did not verify the corrosion resistance of the material under the condition of electropolishing and environmental stress, even though we speculated that both processes could improve the resistance significantly. Because of the improvement of surface, defects of the material surface could drastically reduce the buildup of local corrosion. In terms of environmental stress, the material without heat treatment would be fully pitting, which could weaken the structure of the stent,dramatically increasing the risk of stent fracture. Compared with the heat-treated material, corrosions were often more localized, which still maintained a considerable structure, so there was a relatively smaller risk of stent fracture. The study provided different material processing methods for bioresorbable materials and heat treatment was proposed to change the corrosion resistance and mechanical properties of ZK60 magnesium alloy, which was expected to become a recommended method to improve the corrosion resistance. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/86126 |
DOI: | 10.6342/NTU202202884 |
全文授權: | 同意授權(全球公開) |
電子全文公開日期: | 2027-09-01 |
顯示於系所單位: | 機械工程學系 |
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U0001-2708202216033100.pdf 此日期後於網路公開 2027-09-01 | 6.83 MB | Adobe PDF |
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