【作者】 刘帅；

【导师】 殷锦捷； 刘忆；

【作者基本信息】 辽宁工程技术大学 ， 材料学， 2008， 硕士

【摘要】 镁合金具有低的密度和高的阻尼减震性能以及良好的可成型性和切削加工性能,因此近年来其在工业应用中受到越来越多的重视,但是镁合金的室温强度低、耐磨性差和耐蚀性差大大限制了作为工程结构材料的应用范围。因此,采用表面改性技术以增强镁合金表面化学和力学性能具有重要的现实意义。为此本文以AZ91D镁合金为研究对象,采用激光表面合金化技术提高镁合金表面性能。利用现代微观分析技术和性能检测手段,对改性层微观组织结构、性能特征随激光工艺参数的变化规律进行了系统分析。在试验中找到显著提高镁合金耐蚀性、耐磨性最佳的激光合金化工艺参数。实验结果表明,激光合金化改性层分为合金化区、结合区和热影响区。合金化区鱼骨状组织为α-Mg和梅花状组织为α-Mg+β-Mg17Al12的组织,灰色基体为少量的α-Mg和较多β-Mg17Al12的组织。改性层同样是由α-Mg和金属间化合物β-Mg17Al12构成,并且β-Mg17Al12相的含量较基体镁合金均有明显增加。不同激光工艺参数下改性层的腐蚀速率远远低于基体。激光功率一定时,扫描速度为3mm/s为最佳。扫描速度一定时功率为1.5kW时,耐蚀性最佳。改性层最终凝固组织呈明显的梯度分布特征,最高强度出现在亚表层中。在功率为2kW时,不同扫描速度下亚表层平均硬度约在150-330HK范围内,较基体(70HK)约提高100-370%。其中扫描速度为10mm/s时为最佳,较基体约提高250-370%。在扫描速度为7mm/s时,功率为2.5kW为最佳,较基体提高约250-470%。在磨粒磨损机制下,改性层耐磨性的高低与硬度试验结果基本相吻合,即硬度越高耐磨性越好。在功率为2kW时,扫描速度为9mm/s时耐磨性最好;扫描速度为7mm/s时,功率2.5kW为最佳。更多还原

【Abstract】 Magnesium alloys have low densities, high-damping shock absorption properties and good molding and machining performance, so in recent years magnesium alloy is increasing attention in the field of industries application. However, the magnesium at room temperature low strength, alloy wear resistance poor and corrosion resistance poor, as a major constraint on the structure of engineering materials applications. Therefore, by taking the surface modification technology, the improvement of the chemical and mechanical properties of Mg alloys has the important practical significance. In this paper, the AZ91D magnesium alloy used for researching, laser surface alloying is carried out to improve the surface properties of Mg alloy. The microstructure and properties of the coatings, as well as the influence of processing parameters on them, were investigated by modern micro-analysis techniques and performance analysis facility.The results show that laser-modified alloy layer is divided into alloying zone, the bond zone and heat-affected zone. The microstructure of fishbone in alloying zone isα-Mg and the microstructure for the plum blossom isα-Mg +β-Mg17Al12, gray substrate is a small amount ofα-Mg and more Mg17Al12. The modified layer is constituted by theα-Mg and metal compoundsβ-Mg17Al12, and the content ofβ- Mg17Al12 is increased than the substrate Mg alloy. The corrosion rate of modified layer is far lower than the substrate under different laser technology parameters. When the scanning speed is 3mm/s, the best corrosion resistance was got under certain laser power. The best corrosion resistance was got when power is 1.5kW under certain scanning speed, modified-final solidification structure is obvious gradient distribution, and the intensity maximum was in the subsurface. When the power is 2kW, under the different scanning speed the average hardness is between 150-330HK in the sub-surface, which is raise about 100-370% than the substrate (70HK). the hardness raised about 250-370% than substrate when the scanning speed is 10mm/s. When the scanning speed is 7mm/s, the power is 2.5kW the best hardness was got, increasing about 290-470% than the matrix. With the abrasive wear mechanism, the wear resistance of modified layer coincides the hardness test results, that is, the hardness is higher, the wear resistance is better. The best wear resistances were got when the power is 2kW and the scanning speed is 9mm/s, and the scanning speed is 9mm / s, the power 2.5 kW.更多还原