本文選題：Mg-Zn-Zr-Gd合金　切入點(diǎn)：Gd元素　出處：《太原理工大學(xué)》2017年碩士論文

【摘要】：鎂元素是人體必需的一種營(yíng)養(yǎng)元素,并且鎂合金在人體的環(huán)境中有良好的生物相容性,又由于它在人體內(nèi)形成的腐蝕產(chǎn)物無(wú)毒無(wú)害,所以鎂合金常常被作為生物材料應(yīng)用在醫(yī)學(xué)中,例如鎂合金作為血管支架的常用材料,在當(dāng)植入人體后的支架材料,在人體的環(huán)境中經(jīng)過(guò)緩慢的降解,最終被新生成的骨組織取代,這樣就避免了從患者體內(nèi)取出植入件而帶來(lái)的二次手術(shù)的痛苦,同時(shí)還大大減少了醫(yī)療費(fèi)用。但是,因?yàn)殒V合金在液體環(huán)境中腐蝕速度快,這樣就有可能導(dǎo)致導(dǎo)致了患者未完全治愈之前,植入的支架材料就喪失了完整的力學(xué)性能,這一缺點(diǎn)則在很大程度上限制了鎂合金作為植入材料在醫(yī)學(xué)上的廣泛應(yīng)用。本課題選取了生物相容性良好的Gd、Zn和Zr作為合金材料,研究Gd對(duì)Mg-Zn-Zr合金的力學(xué)性能及腐蝕性能的影響,并確定最優(yōu)的合金成分,在此基礎(chǔ)上繼續(xù)研究了擠壓溫度對(duì)合金的性能影響,并最終確定最佳的擠壓溫度。具體研究結(jié)果如下:(1)鑄態(tài)合金中,不同Gd含量(0wt.%、1wt.%、2wt.%、3wt.%)的Mg-4Zn-x Gd-0.4Zr合金,隨著Gd含量的增加,合金的晶粒尺寸有明顯減小的趨勢(shì)。Gd含量越多,晶粒組織越細(xì)小,力學(xué)性能也就越好,Mg-4Zn-0.4Zr-3Gd表現(xiàn)出了最佳的力學(xué)性能。同時(shí)Gd元素的變化,影響了合金中相的組成,Mg-4Zn-0.4Zr合金由鎂基體和Mg0.97Zn0.03二元相組成,當(dāng)添加Gd元素之后Mg-4Zn-0.4Zr-1Gd、Mg-4Zn-0.4Zr-2Gd以及Mg-4Zn-0.4Zr-3Gd主要由鎂基體、Mg0.97Zn0.03相和Mg3Gd相組成,并且Mg3Gd相的體積分?jǐn)?shù)隨著Gd含量的增加而增加。(2)鑄態(tài)合金中晶粒的細(xì)化能夠增強(qiáng)耐腐蝕性能,同時(shí)存在適量的Mg3Gd也會(huì)增強(qiáng)耐蝕性能,但是Mg3Gd的含量超過(guò)一定的值時(shí)會(huì)削弱鎂合金的耐腐蝕性能,Mg-4Zn-0.4Zr-1Gd合金具有比較細(xì)化的晶粒尺寸和存在少量的Mg3Gd相,綜合作用下表現(xiàn)出了最佳的性能。(3)擠壓工藝可以有效的細(xì)化晶粒;材料的擠壓溫度較低可以有效的抑制晶粒的長(zhǎng)大,250℃時(shí)合金的晶粒尺寸最小;擠壓之后合金組織并不完全均勻化。(4)擠壓溫度為250℃時(shí),第二相破碎比較明顯,顆粒狀形態(tài)的第二相較多,顆粒也較小;當(dāng)隨著溫度升高到350℃時(shí),第二相的破碎程度逐漸減小,并且第二相體積分?jǐn)?shù)也隨著降低。與鑄態(tài)相比,擠壓溫度的變化并沒(méi)有改變合金的相的組成,合金仍然是由α-Mg、Mg0.97Zn0.03以及少量的Mg3Gd相組成。(5)擠壓態(tài)合金在浸泡初期,腐蝕速率會(huì)突然增大,然后慢慢的變得平緩穩(wěn)定,隨著溫度的升高,合金的腐蝕速率越低,耐腐蝕性能也會(huì)越好。當(dāng)擠壓溫度為350℃,合金的抗腐蝕性能最佳。平均腐蝕速率為0.42mm/a。(6)電化學(xué)腐蝕試驗(yàn)中,擠壓溫度為250℃時(shí),自腐蝕電位是-1.62V,擠壓溫度升高到300℃,自腐蝕電位也隨著升高到-1.54V,當(dāng)溫度繼續(xù)升高到350℃,自腐蝕電位升高到-1.52V。隨著擠壓溫度的升高,合金的自腐蝕電位就會(huì)變得越正。在溫度為350℃時(shí)具有最佳的耐腐蝕性能,與失重實(shí)驗(yàn)的結(jié)果一致。
[Abstract]:Magnesium is a necessary nutrient element in human body, and magnesium alloy has good biocompatibility in human environment, and the corrosion products formed in human body are non-toxic and harmless.So magnesium alloys are often used as biomaterials in medicine, such as magnesium alloys as common materials for vascular stents, and the scaffolds that are implanted in humans are slowly degraded in the human environment.It was eventually replaced by new bone tissue, thus avoiding the pain of secondary surgery to remove implants from patients and greatly reducing medical costs.However, because magnesium alloys corrode rapidly in liquid environments, this may lead to the loss of complete mechanical properties of the scaffold materials before the patient is fully cured.This disadvantage limits the wide application of magnesium alloys as implants in medicine to a large extent.The effect of Gd on the mechanical and corrosion properties of Mg-Zn-Zr alloy was studied, and the optimum alloy composition was determined.On this basis, the influence of extrusion temperature on the properties of the alloy was studied, and the optimum extrusion temperature was determined.The specific results are as follows: (1) in the as-cast alloy, the grain size of the Mg-4Zn-x Gd-0.4Zr alloy with different Gd contents and different Gd contents is 0 wt.and 2wt.and 3wt.k.) with the increase of Gd content, the grain size of the alloy tends to decrease obviously. The more Gd content, the smaller the grain structure.The better the mechanical properties are, the better the mechanical properties of Mg-4Zn-0.4Zr-3Gd are.The composition of Mg-4Zn-0.4Zr alloy is composed of magnesium matrix and Mg0.97Zn0.03 binary phase. After the addition of Gd element, Mg-4Zn-0.4Zr-0.4Zr-2Gd and Mg-4Zn-0.4Zr-2Gd are mainly composed of mg _ (0.97) Zn _ (0.03) and Mg3Gd phases.And the volume fraction of Mg3Gd phase increases with the increase of Gd content.However, when the content of Mg3Gd exceeds a certain value, the corrosion resistance of magnesium alloy will be weakened. Mg-4Zn-0.4Zr-1Gd alloy has fine grain size and a small amount of Mg3Gd phase.When the extrusion temperature of the material is low, the grain size of the alloy is the smallest when the grain grows up to 250 鈩，

本文編號(hào)：1724637