【作者】 周日学；

【导师】 张会臣；

【作者基本信息】 大连海事大学 ， 材料加工工程， 2008， 硕士

【摘要】 微电子机械系统(MEMS)的迅猛发展促进了纳米金属薄膜在微电子机械系统中的广泛应用。同宏观机械系统一样,当流体通过微电子机械系统时,若满足空泡生成的流体力学条件,系统微型腔内部也会出现空蚀磨损现象。本文利用磁致伸缩超声振荡仪研究了离子束增强沉积钛合金薄膜的空蚀磨损特性,分析了沉积薄膜的空蚀磨损机理,探讨了超声发生强度对薄膜空蚀磨损性能的影响。论文的主要结论如下:1.空蚀实验后,钛合金薄膜试样表面出现了一些随机分布、大小不一的凹坑;随着时间的增加,试样表面凹坑的数目和尺寸均变大。这是由于空泡在表面溃灭时产生的冲击破坏作用而引起的。由于空泡大小、空间分布和溃灭时距表面的距离具有随机性,所以使表面受到的冲击破坏力不同,近而导致薄膜试样表面凹坑大小和分布的随机性。2.在钛合金沉积薄膜和钛合金本体的空蚀磨损过程中,薄膜试样表面未出现沿晶界的滑移和裂纹,且观察不到沉积薄膜的塑性变形;本体试样表面也没有出现明显的沿晶界的滑移和变形,但随着实验时间的增加,本体试样表面出现相对均匀的塑性变形。3.通过对钛合金薄膜空蚀磨损形貌特征的分析,可将其空蚀磨损过程划分为4个阶段:空蚀孕育阶段、薄膜空蚀磨损阶段、薄膜剥蚀脱落阶段、基体空蚀磨损阶段。膜层的空蚀磨损特征表现为空泡溃灭冲击作用力下的凹坑形成、凹坑周围疲劳裂纹形成和扩展、膜层表面局部断裂以及薄膜的剥落。4.对薄膜试样的空蚀光学显微照片进行黑白两色的分色处理,绘制的试样空蚀磨损过程曲线表明:基于两色的空蚀图像处理能够较好的反应材料空蚀磨损过程,易于对局部区域的空蚀情况进行定量描述和表征。5.通过对不同超声发生强度条件下薄膜试样空蚀磨损特性的研究发现,在相同的空蚀时间内,功率越大,试样空蚀破坏程度越严重,由空蚀破坏而导致的薄膜剥蚀脱落所需时间越短。因为超声波发生器输出功率的变化,改变了设备超声发生强度,而超声发生强度的变化改变了设备振动系统的振幅,进而改变了试验系统的空化强度,空化强度的大小影响了材料的空蚀破坏程度。更多还原

【Abstract】 The metal coatings have been widely used in microelectromechanical systems with the rapid development of microelectromechanical. When the liquid is flowing through the micropumps and microvalves, there is definitely a possibility of cavitation erosion in the micro-electromechanical systems if apt hydrodynamic conditions develop, just like the cavitation erosion in the conventional scale hydraulic machinery. The cavitation erosion performance of coatings prepared by ion beam enhanced deposition were investigated on a ultrasonic magnetostrictive cavitation erosion tester. The cavitation erosion process and mechanism were analyzed, and the influence of the different power of the tester on the cavitation erosion performance was explored. The main conclusions are as follow:1. A lot of cavitation pits were produced on the surface of the titanium alloy films after the cavitation test, and the positions and sizes of the pits were stochastic. The number and size of the pits increased with the testing time. It was found that the pits were caused by the effect of cavitation bubbles collapsed. The size and position were decided by the distribution of cavitation bubbles on the surface of the tester.2. It was found that there existed different cavitation erosion behaviors by contrasting the cavitation erosion process of titanium alloy films and the titanium alloy bulk. There are no obvious slippage and deformation along the grain boundary both on the surface of the titanium alloy films and the titanium alloy bulk. There is obvious plastic deformation during the cavitation erosion process of the the titanium alloy bulk, but it is not found during the cavitation erosion process of the the titanium alloy films.3. The cavitation erosion progressed into incubation period, concave formation by the effect of cavitation bubbles collapsed, delamination, and localized fracture, corresponding to the four stages of the cavitation erosion.4. The optical microscope topographs of the samples during the stages of cavitation erosion were treated with the colors-abstraction method. The Cavitation erosion curves were drawen according the data of the colors-abstraction process. It is found that two-color image processing can exhibit the inception of cavitation erosion process well, which can be used to analyze surface changes of the materials qualitatively.5. After the cavitation erosion test with different powers, it was found that the damaged area of samples increased with the power in the same testing time, and it was easy to get the stage of coating’s desquamation. Because the cavitation intensity was altered with the change of the ultrasonic intensity of the device, and the ultrasonic intensity was decided by the power of the device.更多还原