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1、成都理工大学硕士学位论文MgBO/ZK60复合材料的制备及时效行为研究姓名：贾希光申请学位级别：硕士专业：材料学指导教师：陈善华20090501摘 要 Mg2B2O5W/ZK60 复合材料的制备及时效行为研究复合材料的制备及时效行为研究 作者简介：贾希光，男，1983 年 2 月出生，师从成都理工大学陈善华教授，2009 年 6 月毕业于成都理工大学材料学专业，获得工学硕士学位。 摘摘 要要 镁合金是结构材料中最轻的金属，具有比强度和比刚度高、导热性好、屏蔽电磁干扰能力强及减振、降噪性能好、回收再生性良好等一系列优点。但是，镁合金的机械性能不佳、耐蚀性差、高温蠕变性能差，使其应用受到限制。与镁
2、合金相比，镁基复合材料的比强度和比模量等机械性能显著提高，而且保持了镁的尺寸稳定性好和高阻尼等优点，因而得到越来越广泛的重视和研究。 本文采用粉末冶金法成功制备了硼酸镁晶须 （Mg2B2O5W） 体积百分数为 15%的 Mg2B2O5W/ZK60 复合材料，综合应用了金相分析、X 射线衍射（XRD） 、扫描电镜（SEM） 、透射电镜（TEM） 、显微硬度等测试手段，分析了粉末冶金法制备的复合材料在固溶、时效后所引起的对材料显微组织及硬度的影响，并探讨了其时效硬化机理。 研究结果表明，Mg2B2O5W/ZK60 复合材料的显微组织由基体组织 Mg、Mg2B2O5W、MgZn2共晶相和锆单质组成。
3、 Mg 为白色长条状或不规则形状的晶粒，MgZn2共晶相产物分布在晶界或枝晶边界，晶须在基体中分布较均匀。同时，复合材料中有 ZrH 存在。在加入 Mg2B2O5W晶须后，复合材料的晶粒大小较ZK60 合金晶粒有所减小，且晶粒大小均匀。晶须的加入起到了一定的细化晶粒作用。晶须界面没有发现反应产物的存在。 复合材料固溶处理后部分锌被氧化生成 ZnO，存在于晶界或枝晶边界富锌区。同时显微组织中仍存在少量 MgZn2稳定相，MgZn2相是在烧结过程中就已经形成，在随后的热处理过程中基本没有明显变化。复合材料时效过程中时效强化相为 MgZn 相。时效硬化曲线呈双峰，Mg2B2O5W的加入没有从根本上上
4、改变ZK60 的时效硬化机制，而且 Mg2B2O5W的加入、固溶温度的提高都可以加快时效硬化速度。 通过对 Mg2B2O5W/ZK60 复合材料时效后显微组织变化分析， 复合材料在 170时效过程中的再结晶主要以亚晶形核机制形核， 再结晶晶核既有镁基体晶粒内部形核也有晶界突出形核，再结晶后形成的组织形状几乎不变。在冷等静压成形过程中，由于晶须的阻断作用，从而晶须富集区的镁基体优先再结晶。此外，Zr原子在再结晶晶粒长大前沿界面富集到一定程度将阻碍再结晶晶粒长大。 成都理工大学硕士学位论文 粉末冶金法制备的 Mg2B2O5W/ZK60 复合材料比未加入晶须的 ZK60 合金硬度相比增加了 28.0
5、%， Mg2B2O5晶须的加入对 ZK60 合金起到了显著的增强作用。 关键字： 硼酸镁晶须 镁基复合材料 制备 固溶 时效 Abstract Study on Fabrication and Aging behavior of Mg2B2O5W/ZK60 Magnesium Matrix Composites Introduction of the author: Jia Xiguang, male was born in February, 1983 whose tutor was Professor Chen Shanhua. He graduated from Chengdu Univ
6、ersity of Technology in Material Science major and was granted the Master Degree in June, 2008. Abstract Magnesium alloy is the lightest structure material, which has many traits such as high specific strength and stiffness, high thermal conductivity, good electromagnetic shielding characteristics,
7、good vibration and noise reduction capability and well recycle property etc. However, the use of magnesium alloy is limited. Because it has low mechanical property, corrosion resistance, and high temperature creep resistance. In comparison with magnesium alloy, magnesium matrix composites have highe
8、r specific strength, specific stiffness, the composites remain good stability of size and superior damping capacity, so much attention has been paid to the development of magnesium matrix composites. This article reports the preparation Mg2B2O5W/ZK60 magnesium matrix composites with 15% volume fract
9、ion of boric acid magnesium whisker (Mg2B2O5W) by powder metallurgy. And this research analyzed the effect on microstructure and Vickers hardness of the composite after solution and aging treatment for different time prepared by powder metallurgy through metallographic analysis, X-ray diffraction (X
10、RD) analysis, scanning electron microscope analysis (SEM), transmission electron microscope (TEM) and micro hardness analysis. The results showed that microstructure of Mg2B2O5W/ZK60 composites consisted of - Mg (matrix), Mg2B2O5W and eutectic phase MgZn2 and simple substance of zirconium (Zr). - Mg
11、 was white strip or irregular shaped, eutectic phase MgZn2 was at the boundary of the grains and dendrites. Boric acid magnesium whiskers, with excellent composite effect, were distributed uniformly. Meanwhile, the zirconium hydride (ZrH) was produced in magnesium matrix composites. With the additio
12、n of Mg2B2O5W, grain size of composite was uniform and was smaller than that of ZK60 alloy. The introduction of the whisker played a certain role in grain refinement. There 成都理工大学硕士学位论文 were no productions of interface reaction products and attachments at boundary of whicker. In zinc rich area of th
13、e boundary of the grains and dendrites, there were zinc oxide (ZnO) produced from part of zinc in composite after solid solution treatment. Moreover, there was a little stable phase MgZn2 which formed in the process of sintering without big changing in the following heat treatment. MgZn was strength
14、ening phase during the aging and curve of age hardening had two peaks which meant the addition of Mg2B2O5W didnt essentially change mechanism of age hardening. By analysis of microstructure changing of Mg2B2O5W/ZK60 composites after aging, the composites mainly recrystallized as sub grains at 170 du
15、ring aging. Nucleus of recrystallization had nucleation within magnesium matrix and nucleation of crystal boundary bulge. The shape of microstructure after recrystallization almost unchanged. During the process of cold isocratic progressing, Magnesium matrix in whisker rich area recrystallized prima
16、rily because of whisker blocking. Furthermore, if there were enough Zr atoms gathering at the front interface of recrystallization nucleus, it would hinder growth of the nucleus. Hardness of the composite prepared by powder metallurgy was improved by 28% than ZK60 alloy without boric acid magnesium whisker. So, the addition of boric acid magnesium whisker enhanced ZK60 alloy greatly. Keywords: Boric acid magnesium whisker Magnesium matrix composites Fabrication Solutio
