燃烧合成加热压一体化成型制备TiAl基复合材料技术研究

发布时间：2018-02-13 04:15

  本文关键词： Al2O3陶瓷颗粒 内生陶瓷颗粒 TiAl基复合材料 组织 压缩性能　出处：《吉林大学》2015年硕士论文　论文类型：学位论文

【摘要】：TiAl合金具有高熔点、低密度、高的比强度和比模量、低的蠕变速率和较高的抗高温氧化能力等优点，然而TiAl合金所具有的室温本征脆性严重限制了其作为航空航天发动机用高温轻质合金的应用和发展。因此对TiAl合金的研究主要集中在提高强度和塑性上。目前，向TiAl合金基体中引入陶瓷颗粒是提高TiAl合金强塑性的重要方法，但是关于外加法与原位内生这两种陶瓷颗粒引入方式对TiAl基复合材料强度和塑性的影响的对比研究还较少，二者对TiAl基复合材料强塑性的作用机制的差别尚不明确。 因此，本论文以采用燃烧合成加热压一体化成型制备技术制备出的外加与原位内生陶瓷颗粒增强TiAl基复合材料作为研究对象，探索外加α-Al2O3陶瓷颗粒含量、原位内生Ti5Si3陶瓷颗粒含量、双相内生TiB2与Ti5Si3陶瓷颗粒比例对TiAl合金组织及压缩性能的影响，建立组织与性能之间的关系，提出了陶瓷颗粒改善TiAl合金强度和塑性的机制。 本论文主要研究结果如下： 1)采用燃烧合成加热压的方法成功制备出外加α-Al2O3陶瓷颗粒增强TiAl基复合材料，及原位内生陶瓷颗粒(Ti5Si3、TiB2、Ti5Si3-TiB2)增强TiAl基复合材料。发现外加纳米α-Al2O3陶瓷颗粒团聚体为微米尺寸，原位内生陶瓷颗粒的尺寸则达到纳米尺寸，2vol.%Al2O3/TiAl复合材料中α-Al2O3团聚体的尺寸为1-2μm，Ti5Si3和TiB2的尺寸分别为60-90nm和30-50nm。 2)发现原位内生纳米TiB2与Ti5Si3陶瓷颗粒均可以细化TiAl合金的晶粒尺寸，4vol.%TiB2和4vol.%Ti5Si3陶瓷颗粒分别可以使TiAl基体的晶粒尺寸从~65μm下降到~20μm和~25μm。不同Ti5Si3含量对TiAl晶粒尺寸的影响不大。双相(TiB2-Ti5Si3)纳米陶瓷颗粒使TiAl基体晶粒细化的效果更好，，尤其当TiB2:Ti5Si3=2:1(∑M(TiB2+Ti5Si3)=4vol.%)时，TiAl基体的平均晶粒尺寸约为15μm。 3)发现少量外加纳米α-Al2O3陶瓷颗粒可以提高TiAl合金的强度，但会降低TiAl合金的塑性。2vol.%Al2O3/TiAl复合材料的屈服强度(497MPa)和最大抗压强度(1454MPa)分别比TiAl合金高了32MPa和39MPa，压缩断裂应变(14.5%)比TiAl合金低了2.8%。继续增加α-Al2O3的含量会恶化复合材料的性能。双相纳米陶瓷颗粒具有较好的综合力学性能，其中当TiB2:Ti5Si3=2:1(∑M(TiB2+Ti5Si3)=4vol.%)时的综合力学性能最佳，屈服强度(761MPa)、最大抗压强度(1647MPa)和压缩断裂应变(26.1%)分别比TiAl合金高出296MPa、232MPa和8.8%。 4)提出了外加纳米α-Al2O3陶瓷颗粒及∑4vol.%不同比例原位内生纳米TiB2和Ti5Si3陶瓷颗粒对TiAl合金强塑性的影响机制： i)外加纳米α-Al2O3陶瓷颗粒对TiAl强塑性的影响机制：第二相强化。 ii)内生纳米Ti5Si3与TiB2陶瓷颗粒提高TiAl合金强塑性的机制：弥散分布的第二相纳米Ti5Si3与TiB2陶瓷颗粒对TiAl合金基体的强韧化作用和TiAl合金基体的晶粒细化。
[Abstract]:TiAl alloy has the advantages of high melting point, low density, high specific strength and modulus, low creep rate and high oxidation resistance at high temperature. However, the intrinsic brittleness of TiAl alloy at room temperature severely limits its application and development as a high-temperature light alloy for aerospace engine. Therefore, the research on TiAl alloy is mainly focused on improving strength and plasticity. The introduction of ceramic particles into the matrix of TiAl alloy is an important method to improve the strong plasticity of TiAl alloy. However, there are few comparative studies on the effect of addition method and in-situ method on the strength and plasticity of TiAl matrix composites. The difference between them on the strong plasticity of TiAl matrix composites is not clear. Therefore, the content of added 伪 -Al _ 2O _ 3 ceramic particles in TiAl matrix composites prepared by in-situ and in-situ in-situ ceramic particle reinforced composites prepared by combustion synthesis, heating and pressing, was investigated in this paper. The effect of the content of in-situ endogenous Ti5Si3 ceramic particles and the ratio of TiB2 to Ti5Si3 ceramic particles on the microstructure and compressive properties of TiAl alloy was studied. The relationship between microstructure and properties was established. The mechanism of improving the strength and plasticity of TiAl alloy by ceramic particles was put forward. The main results of this thesis are as follows:. 1) addition of 伪 -Al _ 2O _ 3 ceramic particles reinforced TiAl matrix composites and in-situ in-situ ceramic particles Ti _ 5Si _ (3) Ti _ (2) Ti _ (2) Si _ (3-TiB) _ 2) reinforced TiAl matrix composites were successfully prepared by combustion synthesis heating pressing method. It was found that the addition of 伪 -Al _ 2O _ 3 ceramic particle aggregates was of micron size. In situ, the size of in-situ ceramic particles reached the nanometer size of 2vol.Al _ 2O _ 3 / tial composites. The size of 伪 -Al _ 2O _ 3 aggregates was 1-2 渭 m Ti _ 5Si _ 3 and TiB2 was 60-90 nm and 30-50 nm, respectively. 2) it was found that in situ endogenetic TiB2 and Ti5Si3 ceramic particles can refine the grain size of TiAl alloy 4vol.and 4vol.Ti5Si3 ceramic particles, respectively, which can reduce the grain size of TiAl matrix from 65 渭 m to 20 渭 m and 25 渭 m. The effect of different Ti5Si3 content on the grain size of TiAl is discussed. TIB _ 2-Ti _ 5Si _ 3) nanocrystalline particles make the grain refinement of TiAl matrix better. The average grain size of TiAl matrix is about 15 渭 m when TiB2: Ti5Si3Si3Ti5Si3Si3Ti5Si3Ti5Si3Ti5Si3Ti5Si3Ti5Si3Ti5Si3Ti5Si3TiB2Ti5Si3Ti5Si3Ti5Si3Ti5Si3Ti5Si@@. 3) it was found that the strength of TiAl alloy could be improved by adding a small amount of nano-sized 伪 -Al _ 2O _ 3 ceramic particles. However, the yield strength and maximum compressive strength of Al _ 2O _ 3 / tial composite were decreased by 32MPa and 39MPa, respectively, and the compressive fracture strain of TiAl alloy was decreased by 2.8wt% lower than that of TiAl alloy. Further increasing the content of 伪 -Al _ 2O _ 3 would worsen the content of 伪 -Al _ 2O _ 3. Properties. Dual phase nano-ceramic particles have better comprehensive mechanical properties, The comprehensive mechanical properties of TiB2: Ti5Si3Si3Ti5Si3Si3Si3Ti4vol.are the best, the yield strength is 761 MPA, the maximum compressive strength is 1647MPA, and the compressive fracture strain is 26.1 MPA higher than that of TiAl alloy (296MPa 232MPa and 8.8MPa), respectively. 4) the mechanism of the effect of nano-Al _ 2O _ 3 ceramic particles and 鈭

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