激光冲击强化对AZ80镁合金微观组织和电化学腐蚀的影响

发布时间：2018-04-29 19:10

本文选题：AZ80镁合金 + 激光冲击强化　；参考：《江苏大学》2016年硕士论文

【摘要】：作为最轻的结构金属材料,镁合金具有优良的电磁屏蔽性能、散热性能、机械加工性能和减震性能等,被广泛应用于航空航天和汽车工业领域。近年来,交通工具轻量化被认为是应对能源过度消耗和环境严重污染的有效途径之一,这也使得镁合金受到越来越多的重视。然而,镁合金的电极电位很低,耐腐蚀性能较差,对使用环境要求较高,极大地限制了其应用范围。激光冲击强化作为一种新型的表面改性技术,具有可控性强、强化效果明显等优点,在提高材料的耐蚀性方面发挥出独特的优势。本文以连铸态和轧制态AZ80镁合金为研究对象,对其进行热处理、区域LSP及电化学腐蚀实验。论文主要研究内容如下:对AZ80镁合金试样进行预固溶及预时效处理,并采用两种不同激光脉冲能量的激光束对试样进行了光斑搭接的区域LSP试验。对比分析了LSP试样的表面残余应力、显微硬度、物相及微观组织。结果表明,LSP在试样表面形成高幅值残余压应力,随激光脉冲能量增大而增大;厚向显微硬度明显提高,且呈梯度变化,强化层深度在1.0mm以上;预固溶LSP试样组织中有大量孪晶生成,而预时效LSP试样组织中只有少量孪晶,但第二相分布更加连续均匀。对AZ80镁合金试样进行电化学腐蚀实验,得到不同预处理状态及不同激光脉冲能量下区域LSP后试样的电化学腐蚀曲线。从极化曲线和电化学阻抗谱两个方面分析了不同状态镁合金的耐腐蚀性能,并通过拟合电路方式模拟了镁合金表面腐蚀过程中的电极过程。结合组织与性能分析,探讨了不同预处理状态下LSP提高镁合金耐蚀性机理,得到了不同预处理试样LSP的最佳激光脉冲能量范围。对预固溶LSP试样进行了后时效处理,从微观组织、显微硬度、表面残余应力等方面分析了其组织性能变化,并对时效后的试样进行了电化学腐蚀实验和分析。对腐蚀机理、第二相析出及LSP组织性能的稳定性进行了初步探索。
[Abstract]:As the lightest structural metal material, magnesium alloy has excellent electromagnetic shielding performance, heat dissipation, mechanical processing performance and shock absorption properties. It is widely used in aerospace and automotive industry. In recent years, the light weight of vehicles is considered to be one of the effective ways to cope with excessive energy dissipation and serious environmental pollution. Magnesium alloys have been paid more and more attention. However, the electrode potential of the magnesium alloys is very low, the corrosion resistance is poor and the application environment is higher, which greatly limits its application. As a new type of surface modification technology, the laser shock strengthening has the advantages of strong controllability and obvious strengthening effect, which can improve the corrosion resistance of the material. In this paper, the AZ80 magnesium alloy in continuous casting state and rolling state is studied in this paper. The heat treatment, regional LSP and electrochemical corrosion experiments are carried out. The main contents of this paper are as follows: the presolution and preaging treatment of AZ80 magnesium alloy samples are carried out, and two laser pulses with different laser pulse energy are used to carry out the sample. The regional LSP test of the spot lap of the light spot. The residual stress, microhardness, phase and microstructure of the LSP specimen are compared and analyzed. The results show that the high amplitude residual compressive stress on the surface of the sample is formed, which increases with the increase of the laser pulse energy; the thickness of the microhardness is obviously improved, and the gradient is changed, the depth of the strengthening layer is above 1.0mm; the prefixing is prefixed. There are a large number of twins in the tissue of the LSP sample, but only a small amount of twins in the pre aging LSP specimen, but the second phase is more continuous and uniform. The electrochemical corrosion test of the AZ80 magnesium alloy samples was carried out. The electrochemical corrosion curves of the samples after the different pretreated States and different laser pulse energy were obtained. The polarization curves and the polarization curves were obtained. The corrosion resistance of magnesium alloys in different states was analyzed in two aspects by electrochemical impedance spectroscopy. The electrode process in the surface corrosion process of magnesium alloy was simulated by fitting circuit. The corrosion resistance mechanism of LSP alloy in different pretreated States was discussed with microstructure and performance analysis. The best LSP of different pretreatment samples was obtained. The laser pulse energy range. The post aging treatment of predissolved LSP samples was carried out. The microstructure, microhardness and surface residual stress were analyzed. The electrochemical corrosion test and analysis were carried out for the sample after aging. The corrosion mechanism, the second phase precipitation and the stability of the LSP microstructure were preliminarily carried out. Explore.

【学位授予单位】：江苏大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TG146.22;TG665;TG166.4

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