【作者】 王素环；

【导师】 刘耀辉；

【作者基本信息】 吉林大学 ， 材料加工工程， 2006， 硕士

【摘要】 本研究采用合金化方法,在AZ91镁合金中加入稀土Ho来改善其抗腐蚀性能。通过扫描电子显微镜观察、X射线衍射物相分析、拉伸实验、硬度实验、腐蚀失重试验和溶液电偶试验,研究了Ho对镁合金微观组织、机械性能和耐蚀性能的影响,NaCl溶液浓度以及耦接材料对镁合金耐蚀性的影响。结果表明,加入稀土Ho后镁合金有新相Al2Ho生成,合金组织得到细化,β相由不完全离异共晶变为完全离异共晶,二次析出β相的形成得到抑制;镁合金抗拉强度、屈服强度、宏观硬度和α相硬度得到提高,断裂机制从解理断裂转变为准解理断裂;抗浸泡腐蚀性能和抗电偶腐蚀性能得到提高,并且氯离子浓度越大,镁合金的耐蚀性越差,镁合金与QT400-15球墨铸铁和45号钢耦接时腐蚀严重,因此,实际应用中应尽量避免镁合金件与其直接接触。综合机械性能、抗腐蚀性能和经济性,在实验Ho含量范围内AZ91Ho3镁合金的性能最佳。更多还原

【Abstract】 Magnesium alloys are widely used in aviation, automobile, electron and other fields due to their light density, good dimensional stability, excellent mechanical property and shielding electromagnetic interference property. Application in engineering is limited due to its inherent drawbacks, however, such as low elastic modulus, poor plasticity and corrosion resistant properties and so on. Poor corrosion resistant property is the most important factor that restricts to its application. Therefore, it is important to study the anticorrosion properties and push the development of magnesium alloys applications.Nowadays, most of the anticorrosion researches are focused on the surface protection magnesium alloy and so in the state of passivity. Surface anticorrosion technology is just for some specifically condition or accessory. Such one-to-one corrosion control method can not meet apparently the enlarging of magnesium alloys application fields.Alloying addition agent can modify the phase structure and matrix corrosion potential of Magnesium alloy and thus it is an important and essential way to improve the corrosion resistant properties of Magnesium alloys. Consequently, this paper adopted alloying method and added rare earth element Ho into Magnesium alloys in order to improve their anticorrosion properties. Five kinds of heterogeneous Magnesium alloys are AZ91、AZ91+0.1wt.%Ho、AZ91+1.0wt.%Ho、AZ91+2.0wt.%Ho and AZ91+3.0wt.% Ho respectively.The microstructure and phase of magnesium alloys have been analyzed by scanning electronic microscope (SEM) and X-ray diffraction (XRD). The results indicated that there wereαphase,β(Mg17Al12)phase and Al2Ho phase coexisted in Magnesium alloys added with rare earth element Ho. With the addition of rare earth element Ho, the microstructure refined into grain state from bulky bones state and the size of crystal grain decreased; discontinuous reticularβphases distribute over the grain boundary ofα-Mg phase, its eutectic mode have changed into fully-divorced eutectic from partially-divorced eutectic. The formation of second separationβphases is restricted. Tensile and hardness tests showed that rare earth element Ho improved the tensile strength, yield strength and hardness of AZ91 magnesium alloys. The fracture mechanism changed from cleavage fracture to quasi-cleavage fracture. The AZ91 magnesium alloy with 2.0wt.% rare earth element Ho has the best microstructure and mechanical properties in this test.更多还原