镁钙合金力学性能及腐蚀行为的研究

发布时间：2018-11-18 21:55

【摘要】：镁合金具有低密度、高的比强度和比刚度、高阻尼、电磁屏蔽性良好及机械加工方便等优点,被广泛地应用于轻质结构件、航空航天等领域;而在生物材料领域,镁合金具有良好的生物活性和生物相容性,特别是其可生物降解性,为可降解金属硬组织替代材料展示了一个诱人前景。本课题通过元素合金化手段在镁中添加钙元素,熔炼出不同钙含量的Mg-Ca合金。随后对其进行热处理,并通过电化学试验、浸泡试验、硬度试验和拉伸试验,借助金相显微镜、扫描电镜、能谱仪、X射线衍射仪、万能拉伸试验机、布氏硬度计等对这些合金的显微组织、腐蚀行为和力学性能进行了研究。结果显示,铸态下Mg-XCa合金主要是由Mg相和Mg2Ca相组成,随着钙含量的增加,合金中Mg2Ca相增加,合金的抗拉强度和延伸率逐渐减小,屈服强度和布氏硬度逐渐增大;经过热处理后析出过饱和α-Mg固溶体,沿着晶界析出细小颗粒状第二相Mg2Ca,硬度和拉伸性能都有所提高。合金的腐蚀实验结果表明,铸态下,在相同时间段,钙的添加在一定程度上促进了腐蚀速率的加速,且与钙含量成正比关系。其中,Mg-5Ca腐蚀电流密度最高,腐蚀电位最低,其耐蚀性最差;当腐蚀24小时后,失重比达70%。热处理后,合金的腐蚀速率明显降低,但耐蚀性最差的仍是Mg-5Ca。铸态和热处理后Mg-Ca合金的主要腐蚀形态为点蚀和丝状腐蚀。
[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 伪-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.
【学位授予单位】：长安大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG146.22

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