碳纳米管和石墨烯增强AZ31镁基复合材料的组织和性能研究

发布时间：2018-10-10 07:11

【摘要】：采用粉末冶金法结合热挤压制备了不同含量的碳纳米管(Carbon nanotubes,CNTs)、石墨烯(Graphene nanoplates,GNPs)及两者混杂增强AZ31镁基复合材料。利用光学显微镜、X射线衍射、能谱分析和扫描电子显微镜等对复合材料进行表征。研究了 CNTs、GNPs加入含量对显微组织、致密度、力学性能、导电性能和摩擦性能的影响;考察了过程控制剂含量对球磨结果的影响;为了进一步发挥增强体的效果,探索了不同混杂比例CNTs/GNPs增强体对复合材料组织和性能的影响;进行了复合材料的等径角挤压试验。主要结果如下:当过程控制剂硬脂酸的含量为0.3wt.%时,球磨后粉末颗粒最均匀,挤压后材料的抗压强度、硬度、致密度和导电性能最高。随着CNTs含量的增加,复合材料的晶粒尺寸先减小后增大、强度先升高后降低、延伸率和导电率逐渐降低、抗摩擦性能逐渐提高。当CNTs的含量为1wt.%时,晶粒尺寸比基体合金降低19%;其强度稍有升高;硬度和断裂应变比基体提高10%和13%;当摩擦中的法向载荷为50N时,摩擦系数和磨损量分别降低15%和39%。GNPs的含量越高,复合材料的抗拉强度、显微硬度和抗摩擦性能也越高、延伸率、密度和导电率越低。当GNPs的含量为0.5wt.%,挤压方向的晶粒尺寸比基体降低12%;抗拉强度、延伸率、抗压强度、硬度分别为269MPa,13.8%,480MPa和83.5HV;当法向载荷为50N时,摩擦系数和磨损量分别降低9%和25%。CNTs/GNPs混杂增强比单一增强的综合力学性能好。尤其当混杂比例为1:1(CNTs和GNPs的含量分别为0.5wt.%)时,复合材料表现出优异的协同效应。该复合材料的晶粒均匀细小;抗拉强度、硬度和延伸率最高,分别为315MPa、88.7HV和18.5%,比基体合金提升了 11%、9%和28%;导电率为基体的75%;当法向载荷为50N时,复合材料的摩擦系数和磨损量降低了 10%和27%。ECAP变形一道次后,组织明显细化,屈服强度和抗压强度有较明显提升、塑性保持不变。混杂比例为1:1(CNTs和GNPs的含量分别为0.5wt.%)复合材料的屈服强度和抗压强度分别为247MPa和507MPa,比挤压态提升了 14%和9%,比挤压态基体合金提升了 14%和12%。
[Abstract]:Carbon nanotubes (Carbon nanotubes,CNTs), graphene (Graphene nanoplates,GNPs) and mixed AZ31 magnesium matrix composites were prepared by powder metallurgy and hot extrusion. The composite was characterized by X-ray diffraction, energy spectrum analysis and scanning electron microscope. The effects of the content of CNTs,GNPs on microstructure, density, mechanical properties, electrical conductivity and friction properties were studied. The effect of process control agent content on the results of ball milling was investigated. The effects of CNTs/GNPs reinforcements with different hybrid ratios on the microstructure and properties of the composites were investigated, and the equal path angular extrusion tests were carried out. The main results are as follows: when the content of stearic acid is 0.3 wt.%, the powder particle is the most uniform after ball milling, and the compressive strength, hardness, density and electrical conductivity of the extruded material are the highest. With the increase of CNTs content, the grain size of the composites decreases first and then increases, the strength increases first and then decreases, the elongation and conductivity decrease gradually, and the friction resistance increases gradually. When the content of CNTs is 1 wt.%, the grain size is 19% lower than that of the base alloy, the strength is slightly higher, the hardness and fracture strain are 10% and 13% higher than that of the matrix, and when the normal load in friction is 50 N, The higher the content of 39%.GNPs and friction coefficient, the higher the tensile strength, microhardness and friction resistance of the composites, and the lower the elongation, density and conductivity of the composites. When the content of GNPs is 0.5 wt., the grain size in the extrusion direction is 12% lower than that of the matrix, and the tensile strength, elongation, compressive strength and hardness are 269mpa, 13.8MPa and 83.5HVrespectively, and when the normal load is 50N, the tensile strength, elongation, compressive strength and hardness are respectively 480MPa and 83.5HV. The friction coefficient and wear rate were reduced by 9% and 25%.CNTs/GNPs respectively. Especially when the hybrid ratio is 1:1 (the content of CNTs and GNPs is 0.5 wt.%), the composite shows excellent synergistic effect. The composite has the highest tensile strength, hardness and elongation, which are 315MPA, 88.7HV and 18.5, which are 11.9% and 28% higher than the matrix alloy, the conductivity of which is 75%, and when the normal load is 50N, the composite has the highest tensile strength, hardness and elongation of the composite, and the tensile strength, hardness and elongation of the composite are the highest (315MPA, 88.7HV and 18.5HV, respectively). When the friction coefficient and wear capacity of the composites are reduced by 10% and 27%.ECAP deformation, the microstructure is refined, the yield strength and compressive strength are obviously increased, and the plasticity remains unchanged. The yield strength and compressive strength of the composite at 1:1 (CNTs and GNPs = 0.5wt.%) are 247MPa and 507MPA, respectively, which are 14% and 9% higher than those of extruded state and 14% and 12% higher than that of extruded matrix alloy.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB333

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