稀土氧化物對FSP制備原位顆粒增強鋁基復合材料組織和性能的影響
本文選題:攪拌摩擦加工 + 鋁基復合材料。 參考:《南昌航空大學》2017年碩士論文
【摘要】:本文選取1060Al作為基材,采用攪拌摩擦加工方法(Friction Stir Processing,FSP)制備出Ni/Al復合材料,并在此基礎上通過添加不同含量(1-7wt%)、不同種類的稀土氧化物(ReO),研究了ReO對FSP制備Ni/Al復合材料組織和性能的影響,探索了其對原位反應的作用機制,同時研究了熱處理前后復合材料組織、性能的變化。試驗結果表明:當ReO(La_2O_3或CeO_2)的添加量為5wt%時,(Ni+ReO)/Al復合材料中Al_3Ni增強相顆粒分布較為均勻,且含量最高,塊狀的Ni粉團聚減少,復合材料的組織最佳;此時,抗拉強度達到最大值,分別為221MPa和238MPa。相比未添加ReO的復合材料(166MPa),抗拉強度分別提高了33.1%和43.3%。當ReO(La_2O_3或CeO_2)添加量增至7wt%時,復合材料中Al3Ni增強相顆粒的含量反而減少,塊狀的Ni粉團聚重新出現(xiàn),抗拉強度分別下降至205MPa和201MPa。因此,在本試驗條件下ReO的最佳添加量為5wt%。相比Ni/Al復合材料,(Ni+ReO)/Al復合材料中粉末的團聚類型除了常規(guī)的焊合形、長條形、樹葉紋理形,還出現(xiàn)了新的團聚類型:半聚合形、倒C形、顆粒密集形。在FSP過程中添加La_2O_3或CeO_2后,其會阻礙Ni粉的相互吸附、聚攏行為,使Ni粉無法焊合在一起,改善了Ni粉的團聚行為,從而產生了新的團聚類型,并生成了更多的Al_3Ni增強相;此外,ReO能與基體發(fā)生反應生成稀土相,放出巨大的反應熱,使復合區(qū)的溫度升高,促進Al-Ni原位反應的進行,導致Al3Ni增強相體積分數(shù)增加。熱處理試驗中的生成相順序為:Al+Ni→Al_3Ni+Al+Ni→Al_3Ni+Al_3Ni_2,最終的產物為Al3Ni和Al_3Ni_2的混合物。熱處理使Ni/Al及(Ni+ReO)/Al復合材料中Ni粉團聚體強化層厚度增加,并在Ni粉團聚中生成了新相Al_3Ni_2,但是(Ni+ReO)/Al復合材料中Ni粉團聚體的致密度會變差。對比熱處理前,Ni/Al復合材料的抗拉強度分別降低了7.2%、16.9%、23.5%;(Ni+5wt%La_2O_3)/Al復合材料的抗拉強度分別降低了21.7%、26.2%、33.9%;(Ni+5wt%CeO_2)/Al復合材料的抗拉強度分別降低了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.
【學位授予單位】:南昌航空大學
【學位級別】:碩士
【學位授予年份】:2017
【分類號】:TB333
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