稀土氧化物对FSP制备原位颗粒增强铝基复合材料组织和性能的影响

发布时间：2018-04-14 08:26

本文选题：搅拌摩擦加工 + 铝基复合材料　；参考：《南昌航空大学》2017年硕士论文

【摘要】：本文选取1060Al作为基材,采用搅拌摩擦加工方法(Friction Stir Processing,FSP)制备出Ni/Al复合材料,并在此基础上通过添加不同含量(1-7wt%)、不同种类的稀土氧化物(ReO),研究了ReO对FSP制备Ni/Al复合材料组织和性能的影响,探索了其对原位反应的作用机制,同时研究了热处理前后复合材料组织、性能的变化。试验结果表明:当ReO(La_2O_3或CeO_2)的添加量为5wt%时,(Ni+ReO)/Al复合材料中Al_3Ni增强相颗粒分布较为均匀,且含量最高,块状的Ni粉团聚减少,复合材料的组织最佳;此时,抗拉强度达到最大值,分别为221MPa和238MPa。相比未添加ReO的复合材料(166MPa),抗拉强度分别提高了33.1%和43.3%。当ReO(La_2O_3或CeO_2)添加量增至7wt%时,复合材料中Al3Ni增强相颗粒的含量反而减少,块状的Ni粉团聚重新出现,抗拉强度分别下降至205MPa和201MPa。因此,在本试验条件下ReO的最佳添加量为5wt%。相比Ni/Al复合材料,(Ni+ReO)/Al复合材料中粉末的团聚类型除了常规的焊合形、长条形、树叶纹理形,还出现了新的团聚类型:半聚合形、倒C形、颗粒密集形。在FSP过程中添加La_2O_3或CeO_2后,其会阻碍Ni粉的相互吸附、聚拢行为,使Ni粉无法焊合在一起,改善了Ni粉的团聚行为,从而产生了新的团聚类型,并生成了更多的Al_3Ni增强相;此外,ReO能与基体发生反应生成稀土相,放出巨大的反应热,使复合区的温度升高,促进Al-Ni原位反应的进行,导致Al3Ni增强相体积分数增加。热处理试验中的生成相顺序为:Al+Ni→Al_3Ni+Al+Ni→Al_3Ni+Al_3Ni_2,最终的产物为Al3Ni和Al_3Ni_2的混合物。热处理使Ni/Al及(Ni+ReO)/Al复合材料中Ni粉团聚体强化层厚度增加,并在Ni粉团聚中生成了新相Al_3Ni_2,但是(Ni+ReO)/Al复合材料中Ni粉团聚体的致密度会变差。对比热处理前,Ni/Al复合材料的抗拉强度分别降低了7.2%、16.9%、23.5%;(Ni+5wt%La_2O_3)/Al复合材料的抗拉强度分别降低了21.7%、26.2%、33.9%;(Ni+5wt%CeO_2)/Al复合材料的抗拉强度分别降低了18.5%、24.8%、31.5%。
[Abstract]:In this paper, Ni/Al composites were prepared by friction stir processing (FSP) with 1060Al as substrate.On the basis of this, the effect of ReO on the microstructure and properties of Ni/Al composites prepared by FSP was studied by adding different contents of 1 to 7 wtcht and different kinds of rare earth oxides, and the mechanism of its action on in situ reaction was explored.The changes of microstructure and properties of composites before and after heat treatment were also studied.The results show that when the content of ReO(La_2O_3 or CeO-2) is 5wt%, the particle distribution of Al_3Ni reinforcement phase is more uniform, and the content is the highest, the agglomeration of bulk Ni powder decreases, and the microstructure of the composite is the best, and the tensile strength reaches the maximum.221MPa and 238 MPA, respectively.Compared with the composites without ReO, the tensile strength was increased by 33.1% and 43.3%, respectively.When the content of ReO(La_2O_3 or CeO-2) increased to 7wt%, the content of Al3Ni reinforced particles decreased, and the agglomeration of bulk Ni powder reappeared, and the tensile strength decreased to 205MPa and 201MPA, respectively.Therefore, the optimum addition of ReO in this experiment is 5 wts.Compared with the Ni/Al composite, the agglomeration type of powder is not only the conventional soldering shape, long strip, leaf texture, but also the new type of agglomeration: semi-polymeric, inverted C-shaped and dense particle shape.The addition of La_2O_3 or CeO_2 in the process of FSP will hinder the mutual adsorption of Ni powder and make the Ni powder can not be welded together, thus improving the agglomeration behavior of Ni powder, resulting in a new type of agglomeration and the formation of more Al_3Ni enhanced phases.In addition, Reo can react with the matrix to form rare earth phase, giving off a huge reaction heat, increasing the temperature of the composite region, promoting the in-situ reaction of Al-Ni, and increasing the volume fraction of Al3Ni reinforcement phase.In the heat treatment test, the order of phase formation is: 1: Al-Ni / Al_3Ni Al_3Ni / Al Ni / Al _ 3NiS _ 2, and the final product is a mixture of Al3Ni and Al_3Ni_2.Heat treatment increases the thickness of the strengthening layer of Ni powder aggregates in Ni/Al and Ni ReO)/Al composites, and forms a new phase Al _ 3Ni _ 2 in Ni powder agglomeration, but the densities of Ni powder aggregates in Ni / ReO)/Al composites become worse.Compared with that before heat treatment, the tensile strength of Ni / Al / Al composites decreased by 7.2and 16.9and 23.5mg / L respectively. The tensile strength of Ni / Al / Al composites decreased by 21.7and 26.2mg / Al, respectively. The tensile strength of Ni / Al / Al composites decreased by 18.5U / 24.8g / Al, respectively.
【学位授予单位】：南昌航空大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB333

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