不同长度短碳纤维增强2024Sc铝基复合材料组织及性能研究

发布时间：2018-01-10 01:25

  本文关键词：不同长度短碳纤维增强2024Sc铝基复合材料组织及性能研究　出处：《郑州大学》2017年硕士论文　论文类型：学位论文

  更多相关文章： C_f增强铝基复合材料 密度 微屈服强度 热膨胀系数 力学性能

【摘要】：本文采用传统的熔炼铸造法制备了2024Sc铝合金,并采用液态搅拌铸造法制备质量分数为3%长度分别为2mm、3mm、4mm、5mm短碳纤维增强2024Sc铝基复合材料。用化学镀铜的方法处理碳纤维,采用扫描电子显微镜(SEM)观察材料的微观组织和拉伸断口形貌,采用EDS分析材料的微观组织中第二相成分,利用阿基米德原理,对材料的密度、致密化程度进行分析,通过室温拉伸试验、加载-卸载试验测量了五种材料双级时效下的常规力学性能和微屈服性能,采用热膨胀仪测量材料的热膨胀系数。结果表明:(1)铸态的2024Sc铝合金,由于非平衡凝固时发生偏析,微观组织中有白色连续网状的第二相和深灰色α-Al基体组成,在C_f增强复合材料中观察到碳纤维均匀分布在界面上,发生了轻微的界面反应。经过均匀化处理后,连续白色网状第二相变成不连续状,Zr、Sc部分溶解到基体中,部分以Sc、Zr化合物的形式存在。经过挤压后,第二相晶粒被拉长且沿着晶界分布,碳纤维由乱序排列变成沿着挤压方向分布。(2)研究发现,复合材料的理论密度和实际密度均小于2024Sc铝合金,铸态时的密度均小于挤压后的密度。随着碳纤维长度的增加,复合材料的铸态密度先增加后降低,经过挤压后复合材料的密度之间没有明显差异,但是,复合材料孔隙率明显降低,孔隙率分别降低了71.3%、59.4%、80.2%和80%。且随着碳纤维长度的增加,复合材料的致密化程度越来越高,改善了材料的力学性能。(3)经过495℃/2h固溶,130℃/3h+200℃/(5h、10h、15h)双级时效处理后,研究发现,当碳纤维长度小于5mm时,同种材料的抗拉强度、屈服强度和弹性模量均是先升高后降低,终级时效10h时复合材料的抗拉强度、屈服强度和弹性模量最大分别为472MPa、411MPa、87GPa;当长度为5mm时,峰时效时间提前至5h,抗拉强度和屈服强度分别达到494MPa、419MPa;当铝合金中添加碳纤维后,材料的抗拉强度、屈服强度和延伸率均下降,但是材料的弹性模量明显提高,最高为90GPa;复合材料经过拉伸后,通过观察断口形貌发现,碳纤维一般被拔出(提前失效)或拔断。(4)研究发现,微屈服阶段时效硬化率远远高于屈服阶段的时效硬化率,经过495℃/2h固溶,130℃/3h+200℃/10h双级时效处理后,材料的微屈服达到最大值。随着碳纤维长度的增加,C_f增强复合材料的微屈服强度先升高后降低,当碳纤维长度为4mm,复合材料的微屈服强度达到最大值为304MPa。随着碳纤维的加入,降低了C_f增强复合材料的微屈服强度。(5)研究发现,材料相对伸长量与温度变化基本上呈线性关系。加入碳纤维后,复合材料的热膨胀系数降低,随着碳纤维长度的增加,复合材料的热膨胀系数先降低后升高。当碳纤维长度为4mm时,复合材料的热膨胀系数最小,为24.2×10-6/℃。综合分析可得,当碳纤维为4mm时,综合性能最佳。
[Abstract]:In this paper, 2024Sc aluminum alloy was prepared by traditional melting casting method. The mass fraction of 2024Sc aluminum alloy was prepared by liquid agitation casting method. The length of 2024Sc aluminum alloy was 3% mm ~ 3mm ~ 4mm, respectively. 5mm short carbon fiber reinforced 2024Sc aluminum matrix composites. Carbon fibers were treated by electroless copper plating. The microstructure and tensile fracture morphology of the composites were observed by scanning electron microscopy (SEM). The density and densification degree of the material were analyzed by EDS and Archimedes principle, and the tensile test at room temperature was carried out. The conventional mechanical properties and micro-yield properties of five kinds of materials under two-stage aging were measured by load-unloading test. The thermal expansion coefficient of the material was measured by thermal expansion instrument. The results show that the 2024Sc aluminum alloy in the as-cast state is segregated due to non-equilibrium solidification. The microstructure is composed of white continuous reticular second phase and dark gray 伪 -Al matrix. Carbon fiber is observed to distribute uniformly on the interface in Capf reinforced composites. After homogenization treatment, the second phase of the continuous white reticular form was partially dissolved into the matrix, and the second phase was partially dissolved in the matrix, and the second phase was partially dissolved in the matrix. After extrusion, the grain of the second phase is elongated and distributed along the grain boundary, and the carbon fiber changes from disorderly arrangement to the distribution along the extrusion direction. The theoretical and actual densities of the composites are less than 2024Sc aluminum alloy, and the density of as-cast composites is smaller than that of extruded composites. With the increase of carbon fiber length, the as-cast density of the composites increases first and then decreases. There was no significant difference in the density of the composites after extrusion, but the porosity of the composites decreased obviously, and the porosity decreased by 71.3% and 59.4% respectively. The densification degree of the composites increased with the increase of carbon fiber length, and the mechanical properties of the composites were improved by 495 鈩，

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