發(fā)布時間：2018-06-03 17:47

  本文選題：Mg-Y-Zn-Zr合金 + 顯微組織�。� 參考：《太原理工大學》2017年碩士論文

【摘要】：冠心病是危害人類健康的重大疾病之一,在動脈血管中植入支架是治療冠心病的常用方法。鎂合金具有良好的生物相容性和自發(fā)降解性,使其成為血管支架的理想材料。但是鎂合金也存在著強度較低、耐腐蝕性能較差等缺點,制約了其在臨床上的應(yīng)用。本文旨在開發(fā)性能優(yōu)異的新型可降解鎂合金血管支架材料。本實驗選用生物安全性良好的Zn、Y、Zr元素作為合金化元素,通過常規(guī)鑄造法制備了Mg-xY-3Zn-0.4Zr(x=0,1,2,3,4 wt.%)合金和Mg-2Y-yZn-0.4Zr(y=0,1,2,4,5 wt.%)合金,并對優(yōu)選出的最佳成分合金進行熱處理。采用OM、SEMEDS、XRD、失重法、析氫法、電化學測試和室溫拉伸等方法,對比研究了Y、Zn元素及熱處理工藝對合金顯微組織、力學性能和耐腐蝕性能的影響。實驗結(jié)果表明:添加Y元素能夠顯著細化合金晶粒。Mg-3Zn-0.4Zr合金主要由α-Mg和小顆粒狀Mg0.97Zn0.03相組成;當Y含量為1 wt.%時合金中出現(xiàn)長條狀Mg3YZn6相(I相);當Y含量為2 wt.%時合金中出現(xiàn)魚骨狀Mg3Y2Zn3相(W相)。少量Y的加入,促進I相的形成,I相與Mg基體電位差較小,形成的微電池數(shù)量減少。此外,Y元素與合金中的Fe、Mn等雜質(zhì)元素形成金屬間化合物,提純?nèi)垡?改善合金的耐腐蝕性能。過量Y的加入形成硬脆的W相呈網(wǎng)狀分布在晶界上,W相與鎂基體結(jié)合鍵較弱,易產(chǎn)生微裂紋。且第二相數(shù)量較多時,合金產(chǎn)生嚴重的偏析現(xiàn)象,降低合金的力學性能。Mg-2Y-3Zn-0.4Zr合金表現(xiàn)出最佳的綜合性能。與Y元素相比,添加Zn元素對合金的晶粒細化作用有限。Mg-2Y-0.4Zr合金主要由α-Mg基體和Mg24Y5相組成;Mg-2Y-1Zn-0.4Zr合金由α-Mg基體和I相組成;繼續(xù)增加Zn含量,合金中出現(xiàn)W相。微量的Zn元素能提高基體腐蝕電位,提高合金耐腐蝕性能。Zn溶入Mg基體中,產(chǎn)生固溶強化。過量的Zn產(chǎn)生大量的第二相,增加了合金電偶腐蝕的傾向。硬脆的W相聚集甚至割裂基體,降低合金力學性能。因此,隨著Zn含量的增加,合金的耐腐蝕性能和力學性能均呈現(xiàn)出先增加后降低的趨勢。Mg-2Y-1Zn-0.4Zr合金表現(xiàn)出最佳的綜合性能。在熱處理過程中,Mg-2Y-1Zn-0.4Zr合金的晶粒發(fā)生了一定程度的長大現(xiàn)象;熱處理未改變合金的相組成(α-Mg基體和I相),長條狀I(lǐng)相轉(zhuǎn)變?yōu)轭w粒狀,均勻分布在基體上。T4-10態(tài)合金中大部分I相溶解,減少了合金中的微電池數(shù)量,耐腐蝕性能增強。T4-30態(tài)合金由于保溫時間太長,晶粒嚴重粗化,總晶界面積減小,晶界對位錯的阻礙作用減弱,且晶界上難熔的雜質(zhì)密度增大,性能降低。時效處理后,基體上析出細小彌散分布的I相,起到彌散強化的作用。此外,析出相均勻分布在基體上,降低了局部腐蝕的傾向,耐腐蝕性能增強。本研究中,T6態(tài)綜合性能最佳:失重平均腐蝕速率為0.189 mm/a,抗拉強度為258 MPa,屈服強度為144 MPa,伸長率為15.5%。該結(jié)果基本滿足支架材料對力學性能和耐腐蝕性能的要求。
[Abstract]:Coronary artery disease (CHD) is one of the major diseases that endanger human health. Stent implantation in arterial vessels is a commonly used method in the treatment of coronary artery disease (CHD). Magnesium alloy has good biocompatibility and spontaneous degradation, which makes it an ideal material for vascular stent. However, magnesium alloys also have some disadvantages, such as low strength and poor corrosion resistance, which restrict their clinical application. The aim of this paper is to develop new degradable magnesium alloy vascular scaffolds with excellent performance. In this experiment, the Zn-ZY Zr alloy, which has good biological safety, was used as alloying element. Mg-xY-3Zn-0.4ZrxOZn-0.4ZrxCX 4wt.) alloy and Mg-2Y-YZn-0.4ZryZn-0.4ZryZn-0.4ZryZn-0.4ZryZn-0.4ZryZn-45wt.) alloy were prepared by conventional casting method, and the best component alloys were heat-treated. By means of OMSEMEDS XRD, weightlessness, hydrogen evolution, electrochemical measurement and room temperature tensile test, the effects of Y _ (Zn) and heat treatment on the microstructure, mechanical properties and corrosion resistance of the alloy were studied. The experimental results show that the addition of Y element can significantly refine the grain size of the alloy. Mg-3Zn-0.4Zr alloy mainly consists of 偽 -Mg and small granular Mg0.97Zn0.03 phase. When Y content is 1 wt.%, long stripe Mg3YZn6 phase I phase is found in the alloy, and fishbone Mg3Y2Zn3 phase W phase is found in the alloy when Y content is 2 wt.%. The addition of a small amount of Y promoted the formation of phase I and the potential difference between phase I and mg matrix was smaller, and the number of formed microbatteries decreased. In addition, Y element forms intermetallic compound with impurity elements such as Feo mn in the alloy to purify the melt and improve the corrosion resistance of the alloy. The hard and brittle W phase was formed by the addition of excess Y, and the bonding bond between W phase and magnesium matrix was weak on the grain boundary, resulting in microcracks easily. When the number of the second phase is higher, serious segregation occurs, and the mechanical properties of the alloy. Mg-2Y-3Zn-0.4Zr alloy shows the best comprehensive properties. Compared with Y element, the effect of Zn addition on grain refinement is limited. Mg-2Y-0.4Zr alloy is mainly composed of 偽 -Mg matrix and Mg24Y5 phase, which consists of 偽 -Mg matrix and I phase, and W phase appears in the alloy with increasing Zn content. Trace Zn element can increase the corrosion potential of the matrix and improve the corrosion resistance of the alloy. Zn is dissolved into the mg matrix, resulting in solid solution strengthening. Excessive Zn produces a large number of secondary phases, which increases the tendency of galvanic corrosion of the alloy. The hard and brittle W phase aggregates and even cleans the matrix, which reduces the mechanical properties of the alloy. Therefore, with the increase of Zn content, the corrosion resistance and mechanical properties of the alloy increased first and then decreased. Mg-2Y-1Zn-0.4Zr alloy showed the best comprehensive properties. The grain size of Mg-2Y-1Zn-0.4Zr alloy grew to a certain extent during heat treatment, and the phase composition (偽 -Mg matrix and I phase) was not changed after heat treatment. The dissolution of most of phase I in the matrix. T4-10 alloy reduces the number of microbatteries in the alloy. The corrosion resistance of the alloy is enhanced. Due to the long holding time, the grain size is coarsened and the total grain boundary area is decreased. The hindrance of the grain boundary to the dislocation is weakened, and the impurity density on the grain boundary increases and the performance decreases. After aging treatment, I phase was precipitated from the matrix, which played the role of dispersion strengthening. In addition, the precipitation phase is uniformly distributed on the matrix, which reduces the tendency of local corrosion and enhances the corrosion resistance. In this study, the comprehensive performance of T6 state is the best: the average weight loss corrosion rate is 0.189 mm / a, the tensile strength is 258MPa, the yield strength is 144MPa, and the elongation is 15.5 mm / a. The results basically meet the requirements of mechanical properties and corrosion resistance of scaffolds.
【學位授予單位】：太原理工大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TG146.22;R318.08

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