激光微熔纳米SiC颗粒增强Al基复合层数值模拟与实验研究

发布时间：2018-06-07 17:39

本文选题：激光微熔 + 纳米SiC颗粒　；参考：《江苏大学》2017年硕士论文

【摘要】：铝(Al)是机械行业仅次于钢铁的用量最大的金属材料,而铝金属构件的失效多发生于表面或始于表面,因此铝金属构件的表面性能成为决定其整体服役行为的关键因素。纳米颗粒增强金属基复合涂层既有金属良好的塑性、韧性,又具备陶瓷的高硬度、耐高温等优点,展现出广泛的工程应用前景。为了解决激光熔覆制备纳米涂层中纳米颗粒大量熔化而导致涂层中纳米颗粒强化作用下降的问题,本论文提出采用激光微熔的方法制备纳米颗粒增强金属基复合层,拟通过有限元分析软件ANSYS和FLUENT模拟工业纯铝表面激光微熔纳米SiC颗粒的温度场、流场及纳米颗粒在整个激光微熔过程中的微观动态运动过程,同时进行相关的激光微熔实验研究,主要结果如下:(1)模拟了不同激光工艺参数下工业纯铝表面激光微熔纳米SiC颗粒的温度场,并且选出合适的激光工艺参数。结果表明,脉冲激光微熔纳米SiC颗粒温度场的等温线呈圆形分布,未出现连续激光加工中的尾托现象;激光作用下,材料表面温度呈现急热骤冷的特点;熔池极值温度、熔宽和熔深均随着单脉冲激光能量的增加、频率的增大而增加;选择激光能量0.6 J、脉宽10 ns、频率1Hz、光斑直径1 mm、扫描速度2 mm/s作为后续流场仿真的激光工艺参数。(2)研究了激光微熔过程中流场及纳米SiC颗粒在熔池中的动态运动过程。在脉冲激光的作用下,熔池熔合线处产生向内旋转的Marangoni涡流;熔池的横截面上形成两个对称的漩涡;熔池径向向外产生两个大小不一的漩涡,其中心前部的涡流较强;上表面的流体由熔池中心流向四周;建立了高温SiC颗粒与基体的动态结合可视化模型,进行了合理的机理描述。(3)开展了不同激光能量下工业纯铝表面激光微熔纳米SiC颗粒的实验研究。结果显示,工业纯铝表面SiC衍射峰的强度随着能量的提高明显增强,实现了激光微熔固态颗粒嵌入基体的良好效果;表面硬度随着激光能量的提高而增加,在0.6 J时显微硬度高达163 HV;随着激光能量的提高,纳米颗粒团聚现象明显减少,表层中的纳米SiC颗粒更加均匀地分布在基体中。
[Abstract]:Aluminum (Al) is the second largest metal material in mechanical industry after iron and steel, and the failure of aluminum metal component occurs mostly on the surface or begins on the surface. Therefore, the surface performance of aluminum metal member becomes the key factor to determine its whole service behavior. Nano-particle reinforced metal-based composite coatings not only have good plasticity and toughness of metals, but also have the advantages of high hardness and high temperature resistance of ceramics. In order to solve the problem that a large number of nanoparticles melt in the laser cladding coating, which results in the decrease of the strengthening effect of nano-particles in the coating, a laser micro-melting method is proposed to prepare the nano-particle reinforced metal-based composite layer. The finite element analysis software ANSYS and fluent are used to simulate the temperature field, the flow field and the micro dynamic motion of the nano-particles in the whole process of laser micro-melting on the industrial pure aluminum surface. The main results are as follows: (1) the temperature field of nano-SiC particles on the surface of industrial pure aluminum is simulated with different laser processing parameters, and the appropriate laser parameters are selected. The results show that the temperature field isotherms of pulsed laser micromelt nanocrystalline sic particles show a circular distribution, and there is no tail support phenomenon in continuous laser processing, the surface temperature of the material shows the characteristics of rapid hot and sudden cooling under the action of laser, the extreme temperature of melting pool, the temperature of melting pool, and the temperature of melting pool. Both the melting width and the penetration depth increase with the increase of the energy and the frequency of the monopulse laser. Laser energy 0.6 J, pulse width 10 ns, frequency 1 Hz, spot diameter 1 mm, scanning speed 2 mm/s were selected as laser process parameters for subsequent flow field simulation. The flow field and the dynamic motion of sic nanoparticles in the molten pool were studied. Under the action of pulsed laser, Marangoni eddies rotate inward at the fusion line, two symmetric swirls are formed on the cross section of the pool, two swirls of different sizes are produced in the radial direction of the pool, and the eddy current in the front of the center is stronger. The fluid on the upper surface flows from the center of the molten pool to all sides, and the visualization model of the dynamic bonding of sic particles with the matrix at high temperature is established. A reasonable description of the mechanism is given. (3) the experimental study of laser micromelting of nano-SiC particles on industrial pure aluminum surface under different laser energy is carried out. The results show that the intensity of sic diffraction peak on the surface of industrial pure aluminum increases obviously with the increase of energy, and the good effect of laser micromelting solid particles embedded in matrix is realized, and the surface hardness increases with the increase of laser energy. The microhardness reaches 163 HVV at 0.6 J, and with the increase of laser energy, the agglomeration of nano-particles decreases obviously, and the nano-sic particles in the surface layer distribute more evenly in the matrix.
【学位授予单位】：江苏大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG174.4

【参考文献】