【摘要】：鎂合金具有低密度、高的比強度和比剛度、高阻尼、電磁屏蔽性良好及機械加工方便等優(yōu)點,被廣泛地應(yīng)用于輕質(zhì)結(jié)構(gòu)件、航空航天等領(lǐng)域;而在生物材料領(lǐng)域,鎂合金具有良好的生物活性和生物相容性,特別是其可生物降解性,為可降解金屬硬組織替代材料展示了一個誘人前景。本課題通過元素合金化手段在鎂中添加鈣元素,熔煉出不同鈣含量的Mg-Ca合金。隨后對其進行熱處理,并通過電化學(xué)試驗、浸泡試驗、硬度試驗和拉伸試驗,借助金相顯微鏡、掃描電鏡、能譜儀、X射線衍射儀、萬能拉伸試驗機、布氏硬度計等對這些合金的顯微組織、腐蝕行為和力學(xué)性能進行了研究。結(jié)果顯示,鑄態(tài)下Mg-XCa合金主要是由Mg相和Mg2Ca相組成,隨著鈣含量的增加,合金中Mg2Ca相增加,合金的抗拉強度和延伸率逐漸減小,屈服強度和布氏硬度逐漸增大;經(jīng)過熱處理后析出過飽和α-Mg固溶體,沿著晶界析出細小顆粒狀第二相Mg2Ca,硬度和拉伸性能都有所提高。合金的腐蝕實驗結(jié)果表明,鑄態(tài)下,在相同時間段,鈣的添加在一定程度上促進了腐蝕速率的加速,且與鈣含量成正比關(guān)系。其中,Mg-5Ca腐蝕電流密度最高,腐蝕電位最低,其耐蝕性最差;當(dāng)腐蝕24小時后,失重比達70%。熱處理后,合金的腐蝕速率明顯降低,但耐蝕性最差的仍是Mg-5Ca。鑄態(tài)和熱處理后Mg-Ca合金的主要腐蝕形態(tài)為點蝕和絲狀腐蝕。
[Abstract]:Magnesium alloys with low density, high specific strength and stiffness, high damping, good electromagnetic shielding and easy machining have been widely used in light structure, aerospace and other fields. In the field of biomaterials, magnesium alloys have good bioactivity and biocompatibility, especially their biodegradability, which shows an attractive prospect for biodegradable hard tissue substitute materials. In this paper, Mg-Ca alloy with different calcium content was produced by adding calcium element into magnesium by elemental alloying. Then heat treatment was carried out, and by electrochemical test, immersion test, hardness test and tensile test, metallographic microscope, scanning electron microscope, energy spectrometer, X-ray diffractometer, universal tensile tester, The microstructure, corrosion behavior and mechanical properties of these alloys were investigated by Brinell hardness tester. The results show that the as-cast Mg-XCa alloy is mainly composed of Mg phase and Mg2Ca phase. With the increase of calcium content, the Mg2Ca phase in the alloy increases, the tensile strength and elongation of the alloy decrease, and the yield strength and Brinell hardness increase. After heat treatment, supersaturated 偽-Mg solid solution was precipitated, and fine granular second phase Mg2Ca, hardness and tensile properties were improved along the grain boundary. The results of the corrosion test show that the addition of calcium accelerates the corrosion rate in a certain extent and is proportional to the content of calcium in the as-cast alloy at the same time. The corrosion current density of Mg-5Ca is the highest, the corrosion potential is the lowest, and the corrosion resistance is the worst. After heat treatment, the corrosion rate of the alloy decreased obviously, but the worst corrosion resistance of the alloy was Mg-5Ca.. Pitting and filamentous corrosion are the main corrosion patterns of Mg-Ca alloy after cast and heat treatment.
【學(xué)位授予單位】：長安大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TG146.22

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