【作者】 施虹霞；

【导师】 李爱滨；

【作者基本信息】 哈尔滨工业大学 ， 材料学， 2009， 硕士

【摘要】 为了明确颗粒尺寸对铝基复合材料组织、力学性能和阻尼性能的影响规律,本文采用粉末冶金法制备了10%的纳米级、亚微米级和微米级(40nm、500nm、1μm、5μm和10μm)的SiCp/Al复合材料。重点研究了制备纳米级复合材料的球磨工艺,以及制备微米级复合材料的球磨和机械混粉两种工艺。采用SEM和TEM研究了具有不同粒径的复合材料的微观组织,测试了其相应的室温拉伸性能,分析了颗粒尺寸对材料组织和力学性能的影响。采用动态机械分析仪(DMA)测试复合材料的低频阻尼性能随应变和温度变化的阻尼性能,阐述了颗粒尺寸对复合材料的阻尼性能的影响规律和阻尼机制。通过对纳米SiC和Al球磨工艺中的球磨时间以及硬脂酸含量对混粉效果的影响的研究,确定的最佳球磨工艺参数为:球磨时间15h,过程控制剂含量2wt%。并成功制备出综合性能良好的纳米和亚微米级复合材料,抗拉强度分别达到395和365MPa,较纯Al分别提高了259%和232%;虽然延伸率下降,依然分别达到了12.51%和11.4%。退火处理后性能有所下降,幅度不大。分别采用球磨和机械混粉两种工艺制备出微米级(1μm、5μm和10μm)复合材料。球磨制备出的复合材料抗拉强度达到305~316MPa,塑性却只有4.0~7.2%;而机械混粉制备出的复合材料抗拉强度只有133~142MPa,而塑性却达到17.3~26.3%。研究表明,球磨工艺比机械混粉工艺更容易大幅度提高复合材料抗拉强度,同时却使塑性急剧下降。对于高能球磨混粉制备的不同颗粒尺寸SiCp/Al复合材料,抗拉强度、屈服强度都比纯Al显著提高,延伸率明显下降。随着SiC颗粒尺寸的减小,复合材料挤压态的抗拉强度、屈服强度和延伸率逐渐增大;退火后,复合材料的强度和塑性较挤压态稍有降低。TEM分析结果表明,颗粒粒径为40nm和500nm时,挤压态SiCp/Al复合材料的界面附近没有热错配位错产生,基体上有热挤压造成的变形位错,复合材料晶粒细小。退火消除了部分变形位错,复合材料发生了再结晶,纳米SiC阻碍位错运动抑制晶粒长大,再结晶晶粒非常细小。挤压态下的微米级SiCp/Al复合材料的界面处和基体上都有大量位错存在,退火消除了部分变形位错,复合材料发生了再结晶。采用动态机械分析仪研究复合材料阻尼。对室温阻尼-应变振幅的曲线研究表明,无论是纳米、亚微米级和微米级复合材料在室温下显示的都是典型位错机制。并随着SiC颗粒尺寸的减小,阻尼性能逐渐增大。退火后,随着SiC颗粒尺寸的增大,阻尼性能逐渐增大。并且发现,纳米级复合材料阻尼性能明显要高于其它尺寸材料;退火后,其阻尼性能变为最低。阻尼-温度谱的测试结果表明,颗粒尺寸显著影响着内耗峰的出现。无论是纳米、亚微米级和微米级复合材料都发现了位错内耗峰的存在,并且随着颗粒尺寸增大,内耗峰后移。晶界阻尼峰在纳米、亚微米级复合材料中可以明显观察到,在微米级复合材料中并不明显。更多还原

【Abstract】 In order to obtain the effect of particle size on the microstructure, the mechanical properties and the damping properties of aluminum matrix composite, the aluminum matrix composites reinforced by 10vol% SiC particles with various sizes were fabricated by powder metallurgy The high energy ball milling technics twas studied in detail. The microstructure of composites were analysed by SEM and TEM and the mechanical properties at room temperature were measured. The strain dependent and temperature dependent low frequency damping capacities of these composites and alloys were studied by dynamic mechanical thermal analyzer (DMA). The effect of particle size on the tensile mechanical properties and the damping properties were analysed in detail.According to the investigations of the influences of milling time and process control agent(PCA) on the ball-milling effect, the ball-milling parameters were optimized as followed: milling time: 4:1; PCA content :2wt%. The tensile strength of the aluminium composites with 40nm and 500nm SiC reached 395 and 365 MPa respectively, meanwhile the elongation reached 12.51% and 11.4%。The aluminum matrix composite with various sizes changed from 1μm to 10μm were fabricated by high energy ball milling and regular powder milling technics. The tensile strength of composites fabricated by high energy ball milling reached 305~316MPa, the elongation reached 4.0~7.2%, while the tensile strength of composites fabricated by regular powder milling reached 133~316MPa, the elongation reached 17.3~26.3%. The results showed that the high energy ball milling can improve the strength and reduce the elongation.The tensile strength and the yield strength of SiCp/Al MMCs fabricated by powder metallurgical process with high energy ball milling were significantly greater than Al, and the elongation lower than that of Al. With decreasing SiC particle size, the strength and elongation of the MMCs as-extruded increase, the strength and elongation decreased after annealing.According to TEM results,free dislocations were observed in the SiCP/Al composite as extruded reinforced with SiC particles of 40nm and 500nm. The dislocations of high-density were generated in the matrix by thermal extrusion, and the grain size was fine. The dislocations were disappeared and recrystallization occurred in the annealing process. The grains were restrained by nano-SiC and the recrystallized grain size was refined furthermore. The high-density dislocations existed in the matrix and near the interfaces and annealing made some dislocations disappear and recrystallize.The research of damping capacity of extruded and annealed MMCs showed that damping-strain amplitude can be explained by G-L dislocation damping mechanism. With decreasing SiC particle size, the damping-strain amplitude of the MMCs as-extruded increased, and that decreased after annealing.The research of the damping-temperature capacity for SiCp/Al composites showed that the damping peak influenced by particle size. The damping peak induced by dislocation was observed in all MMCs, and with increasing the particle size, the peak location moved to high temperature.更多还原