镍涂层短碳纤维增强AZ91D镁基复合材料的界面特征和阻尼性能

Interface Characteristics and Damping Performance of Ni-coated Short Carbon Fiber Reinforced AZ91D Magnesium Matrix Composites

使用表面化学镀镍的短碳纤维为增强体、AZ91D粉为基体金属,用粉末冶金法和热挤压工艺制备镁基复合材料,用SEM、TEM-EDS、拉伸和动态热机械分析(DMA)等手段表征其微观形貌、界面结构、力学性能和阻尼性能,研究了金属镍涂层短碳纤维对AZ91D镁基复合材料的界面和阻尼性能的影响。结果表明,碳纤维在复合材料中分布均匀,沿着挤压方向定向排列;镍涂层改善了碳纤维与AZ91D基体之间的润湿性;不同频率的应变谱和G-L特征线都表明:复合材料的阻尼机制,除了位错之外还有其他机制;随着应变频率的提高复合材料的阻尼机制由以界面滑移为主转变为以位错为主。随着温度的升高涂层碳纤维增强镁基复合材料的阻尼容量增大,在250~300℃出现一个阻尼峰。随着频率的提高阻尼峰值的温度移向高温,表现出热激活弛豫过程的特征,根据Arrhenius公式计算出其热激活能(H)为3.448 e V。

Carbon fiber/Mg-alloy composites were fabricated by powder metallurgy technique using short carbon fibers without and with electroless plated Ni-coating as reinforcer and AZ91D powder as matrix. Then their interfacial morphology, elemental composition, mechanical properties and damping capacities were characterized by means of SEM, TEM-EDS, tensile tests and dynamic mechanical analyzer （DMA）. Results shows that the carbon fibers are uniformly distributed in the composites and preferentially oriented paralleling to the extrusion direction. The Ni coating improves the wettability between the carbon fibers and AZ91D matrix. Based on the strain spectrum by different frequency strain and G-L characteristic line, it follows that there should be a damping mechanism other than the known dislocation damping mechanism for the composite. With the increasing strain frequency, the control step for the damping performance of composite changes mainly from interface slip to dislocation. The damping capacity of Ni-coated carbon fiber reinforced magnesium matrix composites increase with the rising temperature. One damping peak exists in the range of 250～300℃ .The peak temperature moves to higher tem- perature with the increasing frequency, which shows the characteristics of the thermal activation of relaxation process. According to the Arrhenius formula the calculated thermal activation is 3.448 eV.