【作者】 孙振明；

【导师】 吴昆；

【作者基本信息】 哈尔滨工业大学 ， 材料学， 2018， 硕士

【摘要】 本文以AZ91D镁合金为基体,以M40碳纤维为增强体,用压力浸渗法制备出碳纤维增强镁基复合材料,研究不同制备工艺对复合材料组织与力学性能的影响;通过观察复合材料的界面结构,研究界面对其力学性能的影响规律;最后利用超声波C扫和X射线三维显微镜检测复合材料中的缺陷,研究缺陷对其力学性能的影响规律。通过研究表明,当浸渗温度为750℃时,M40/AZ91D复合材料的弯曲强度在预热温度为550℃时达到最高,为1408MPa,预热温度为500℃和450℃时的弯曲强度分别为1257 MPa和1007 MPa。预热温度越高,纤维表面与浸渗熔体表面温差越小,热应力减小;当预制件的预热温度为550℃时,随着镁合金熔体浸渗温度的升高,M40/AZ91D复合材料上部的弯曲强度在浸渗温度为760℃时达到最高,为1793MPa,浸渗温度为750℃和780℃时的弯曲强度分别为1408MPa和1042MPa,浸渗温度越高为熔体的浸渗提供了充裕的时间,而其下部的弯曲强度要比上部低将近一半,因为下部基体合金来不及浸渗已有部分凝固,而复合材料靠近石墨一侧的力学性能一般比靠近合金一侧高。在M40/AZ91D复合材料界面处发现少量的针状Al₄C₃和块状的Mg₁₇Al₁₂相,界面结合强度适中;M40/AZ91D（Y）复合材料界面处发现大量较粗的主要含有Y元素的针状界面产物和块状的Al₅Mg₁₁Zn₄析出相,界面结合强度过高容易发生脆性断裂,使其力学性能降低。超声波C扫需要制备人工缺陷做对比,对复合材料中分层缺陷检测灵敏度高,可以检测到尺寸约在100μm以上的缺陷。超声波C扫平面图可以确定缺陷的具体尺寸以及位置坐标,而其三维4D图可以知道缺陷在复合材料中的分布状况,但却不能直观地知道缺陷的具体类型;X射线三维显微镜根据待测对象内部不同结构对X射线的吸收率不同,对其进行360°扫描,对其内部结构进行三维重建,可以直观地确定复合材料中的缺陷类型。X射线三维显微镜可以明显地检测到M40/AZ91D复合材料人为造成的裂纹,可以检测到5μm左右大小的裂纹,比C扫更加精确。更多还原

【Abstract】 Here,carbon fiber reinforced magnesium matrix composites were prepared by pressure impregnation method using AZ91 D magnesium alloy as the matrix and M40 carbon fiber as reinforcement,The influence of different preparation processes on the microstructure and mechanical properties of the composites was studied;The influence of interface on mechanical properties was also studied;Finally,ultrasonic C scanning and X ray three dimensional microscopy were used to detect the defects in the composites,and the effect of defects on the mechanical properties of the composites was studied.The study shows that when the infiltration temperature is 750℃,the bending strength of M40/AZ91 D composites reaches the highest 1408 MPa when the preheating temperature is 550℃,and the bending strength of the preheating temperature is 500℃and 450℃is 1257 MPa and 1007 MPa,respectively.The higher the preheating temperature,the smaller the temperature difference between the surface of the fiber and the impregnated melt,which reduces the thermal stress;When the preheating temperature of the preform is 550℃,the bending strength of the M40/AZ91 D composite material reaches the highest at the temperature of 760℃when the melt infiltration temperature of the magnesium alloy increases,which is 1793 MPa.The bending strength of the centigrade is 1408 MPa and 1042 MPa respectively when the infiltration temperature is750℃and 780℃.The higher the infiltration temperature,the longer the infiltration time for the melt,and the bending strength of the lower part is nearly half lower than that in the upper part,Because the lower matrix alloy is not enough to infiltrate the existing part of the solidification,and the mechanical properties of the composite near the graphite side are generally high then one side close to alloy.A small amount of needle like Al₄C₃ and massive Mg₁₇Al₁₂2 phase were found at the interface of M40/AZ91 D composite.The bonding strength of the interface was moderate;and a large number of thicker interface products like needle which mainly containing Y and massive A_l5Mg₁₁Zn₄ precipitates were found at the interface of M40/AZ91D（Y）composite,and the interface reactions are so voilent that interfacial bonding was easily brittle fracture and the more interfacial reactions due to the reduction of mechanical properties of the composites.The ultrasonic C scan needs to make the artificial defects to make the contrast.The sensitivity of the layer defect detection in the composite material is high,and the defects with the size of more than 100μm can be detected;The ultrasonic C scanning plane diagram can determine the specific size and position coordinates of the defects,and the three-dimensional 4D diagram can know the distribution of the defects in the composite material,but it can not intuitively know the specific type of the defect;The X ray three-dimensional microscope according to the different absorptivity of X ray in the different structure of the object to reconstruct the internal structure in three dimensions by 360degrees-scanning.The defects in the internal structure can be clearly defined,and the defect type in the composite can be directly determined.The X ray three-dimensional microscope can clearly detect the wire cutting of M40/AZ91 D composites,and the size of the cracks about 5μm can be detected,which is more accurate than the C scanning.更多还原