【作者】 顾敏；

【导师】 沈宁福； 王西科；

【作者基本信息】 郑州大学 ， 材料加工工程， 2003， 博士

【摘要】 随着金属基复合材料（MMC）的发展及其应用范围的拓展，对其阻尼性能的要求日益迫切。本文结合实际工程应用的需求，对喷射共沉积颗粒增强Al基复合材料在多种热处理状态下的阻尼特性进行了较为系统深入的研究。 研究表明，由于喷射共沉积工艺的快速凝固特点以及陶瓷颗粒增强体的加入引起的基体中位错的增殖和溶质原子在界面的偏聚等因素，6013Al（6061Al、6066Al）／SiCp（碳化硅颗粒）复合材料的热处理时效过程的热力学和动力学发生改变，使得时效析出的过程加速。 本文首次通过固溶后采用不同的冷却方式，对不同热处理状态的6000系列Al／SiCp复合材料的阻尼特性进行了系统的研究。结果表明，该类复合材料在不同的热处理状态下，阻尼特性的变化规律基本一致。热处理对常温下的阻尼性能影响不大，高温下的阻尼性能存在显著不同。100℃～270℃阻尼能力的大小依次为：炉冷态＞空冷态＞-70℃＞原样＞-195℃＞水淬态，超过180℃各热处理态材料的阻尼能力均可达到1×10^-2以上，表现出较好的高温阻尼性能。低温下模量基本不随频率发生变化，超过160℃时，随着温度提高大致表现为线性的下降，且频率越低，模量的亏损越严重。理论分析认为，该类复合材料的频率特性是：以位错运动耗能为主的情况下，阻尼性能随着频率的升高而增加；当以界面粘滞性滑移耗能时，阻尼随频率的降低而增大。其温度阻尼特性为：阻尼随温度的升高增加较大。其阻尼性能的应变振幅特性为：同一频率下，在应变振幅（5～40）×10^-6范围内，内耗值几乎不随应变振幅发生变化，振幅效应不明显，而应变振幅大于10^-4时，则内耗与应变振幅具有强烈的依存性关系，材料的内耗随着应变振幅的增加而大幅地得到提高。实验表明，在兼顾高的机械性能的情况下，固溶后适当地选用比水淬更快的冷却介质可获得比水淬处理更好的阻尼性能，但这时阻尼性能的增加与冷却速度的提高之间并不存在线性的关系。 对6000系列Al／SiCp各种热处理态试样，在150℃～200℃的内耗峰，以及首次在6000系列Al／SiCp／Gr（石墨）混杂增强复合材料中发现的同样温度区间内的内耗峰的形成机理进行了分析。本文通过计算测得这种内耗峰的激活能均高于1eV，且指数前因子介于10^-15～10^-21之间，内耗峰的峰巅温度T_p随着频率的郑州大学博士学位论文摘要提高向高温移动，峰值内耗提高。固溶处理后不同的冷却速度对于内耗峰有明显的影响，当淬火冷却速度高于水淬时，随着冷速的加大，内耗峰向高温移动。分析表明，该峰具有弛豫特性，它是在热与应力的双重作用下，通过热激活，由位错拖曳点缺陷运动耗能所致，此峰为位错阻尼峰，与G一L的位错阻尼理论有较好的符合性。 通过引入位错阻尼模型和建立界面的微滑移模型，对SICP/Gr混合增强的AI基复合材料的阻尼特性进行了研究。表明混杂增强的MMC的最主要阻尼机制可以归结为:在低温下的位错阻尼机制、Gr/基体界面的微滑移和界面阻尼机制;较高温下的界面的滑移机制和位错脱钉阻尼机制。实验获得SicP/Gr混杂增强的MMC较之单一Sicp增强的MMc的阻尼性能，提高了2倍以上。表明在单一SICp增强的基础上，通过小体积分数Gr的加入进行混杂增强，可以实现在不降低材料模量的同时，使MMC的整体阻尼性能得到显著的改善。这一研究结果对实际的应用意义重大。 采用有限元方法，利用实验的数据，首次通过建立多颗粒模型，在考虑热处理因素、界面实际应力状态等的更加接近实际的条件下，对颗粒增强Al基复合材料的阻尼性能进行了动态模拟。模拟结果与实验结果有较好的对应和一致性。这一成果对进一步开展颗粒增强金属基复合材料阻尼性能的模拟具有一定的理论和实际指导意义。更多还原

【Abstract】 With the expending applications of metal matrix composites (MMCs), there is growing demand for their damping capacity. In this dissertation, the damping behavior of Al alloy based MMCs fabricated by spray atomization and codeposition with different heat treatment processing was studied systematically.The courses of ageing precipitation of 6013A1(6061A1, 6066Al)/SiCp MMC were accelerated, owing to the microstructure features resulted from rapid solidification in spray codeposition as well as the increased dislocation density in the matrix reinforced by silicon carbide particles.The damping behaviors of 6000 series Al alloys/SiCp MMC with different heat treatments was investigated systematically by means of changing the quench medium after solution treatment. The damping capacity of all the treated samples were tested using a multifunctional internal friction instrument and DMA, and the spectra showing the dependence of internal friction upon frequency, temperature and strain amplitude were obtained. As the results show, the damping capacity of different treated samples changed slightly at low temperature, but remarkably at elevated temperature. Over a 100癈 to 270 癈 temperature range, the damping capacity was ranked from great to small as follows: sample cooled in furnace, sample cooled in the air, sample quenched at -70 癈, sample without heat treatment, sample quenched at-195癈 and sample quenched in water. In addition, the damping capacity of all the specimen reached 1?10-2 when temperature was above 180癈, which exhibited excellent high temperature damping capacity. On the other hand, the modulus did not change with frequency at low temperature, while, it decreased linearly with increasing frequency above the temperature of 160癈Meanwhile, the lower the frequency was, the more modulus deterioration was observed. It was considered that the dislocation damping, the interface damping between the matrix and reinforcement particulates and the inherent internal friction of the matrix alloys andmechanisms of the peak phenomena were in good accordance with the G-L theory of dislocation internal friction.Through introducing the model for dislocation damping and setting up a relaxation model for micro-sliding of interface, the damping mechanisms for the SiCp/Gr hybrid MMC were studied. The operation mechanisms in the hybrid MMC were dislocation damping, Gr/Al interface micro gliding damping and interface internal friction at low temperature, and the interface sliding and dislocation movement dragging the point defects damping at high temperature. The damping capacity of SiCp/Gr hybrid MMC were much greater than the SiCp-reinforced MMC. It was over three times higher than that of the SiCp-reinforced MMC. It was further proposed that selecting the proper SiCp/Gr ratio could improve the damping capacity of the materials, with holding high strength and modulus.The damping capacity of SiCp-reinforced MMC was simulated dynamically by setting up a new multi-particulate interface model, under the condition of different heat treatments and actual interface stress using finite element method and experiment dada. As a result, the simulation results were in good accordance with the experiments.更多还原