纳米SiC_p增强7075铝基复合材料半固态触变成形研究

发布时间：2018-03-17 04:11

  本文选题：纳米SiCp　切入点：铝基复合材料　出处：《哈尔滨工业大学》2015年硕士论文　论文类型：学位论文

【摘要】：铝基复合材料具有良好的强度、耐磨性和导热性能的特点,在航空、航天和民用领域得到了大量的应用。纳米颗粒增强铝基复合材料可以实现复合材料强度、韧性、硬度和耐磨性等性能的结合,具有优异的强度和韧性。半固态触变成形技术可以有效地避免铸造过程中的紊流和热裂。本文结合纳米颗粒增强铝基复合材料的制备方法和铝合金半固态成形技术,实现高性能纳米增强铝基复合材料结构件的成形制造,促进半固态触变成形技术在纳米颗粒增强铝基复合材料结构件成形方面的应用。采用超声辅助半固态机械搅拌方法制备纳米Si C颗粒增强7075铝基复合材料,复合材料的微观组织具有明显的球状晶特征,晶粒平均尺寸为30μm,纳米Si C颗粒在晶粒内部均匀分布,在晶界处存在一定的偏聚。铝基复合材料等温处理过程中固相晶粒尺寸和圆整度取决于等温温度和等温时间,保温温度为590℃和600℃时制备的半固态坯料具有较小的晶粒尺寸和较好的圆整度,当保温时间大于20min时,坯料中固相长大显著,出现了明显的蔷薇组织。利用Deform-2D有限元软件对纳米Si C颗粒增强7075铝基复合材料触变成形过程进行了数值模拟分析。模拟结果表明,触变成形过程中的等效应力随着坯料温度的升高逐渐减小,成形件不同位置处的等效应变数值相近,提升模具温度和凸模速度可以有效地减缓坯料热量的散失。开展了纳米Si C颗粒增强7075铝基复合材料半固态触变成形实验研究,研究结果表明,触变变形的复合材料触变成形筒形件不同位置处的金相存在较大差异,晶粒沿着挤压方向被严重拉长,侧壁区域的晶粒在垂直挤压方向上变形量相对较小,触变成形过程中纳米Si C颗粒在基体中的分布没有发生变化,晶界处Si C颗粒的分布高于晶粒内部的分布。成形件力学性能中屈服强度达到245MPa,比原材料提高了53%,抗拉强度达到313MPa,提高了2.3%,筒形件侧壁的抗拉强度高于底部区域的抗拉强度,侧壁区域的断裂方式以韧性断裂为主。经过T6热处理后,材料中Cu元素的偏聚得到解决,抗拉强度达到552MPa,比原材料提高了12.7%,延伸率达到8%,与原材料7075铝合金的延伸率相近。在室温大气环境下材料的耐磨性没有得到明显的提高,材料的磨损形式主要是磨粒磨损。
[Abstract]:Aluminum matrix composites have been widely used in aeronautical, aerospace and civil fields because of their good strength, wear resistance and thermal conductivity. The combination of hardness and wear resistance, With excellent strength and toughness, semi-solid thixoforming technology can effectively avoid turbulence and hot cracking in casting process. In this paper, the preparation method of nano-particle reinforced aluminum matrix composite and semi-solid forming technology of aluminum alloy are combined. To realize the forming manufacture of high performance nano-reinforced aluminum matrix composite structure, To promote the application of semi-solid thixoforming technology in the forming of nano-particle reinforced aluminum matrix composite structure, the ultrasonic assisted semi-solid mechanical stirring method was used to prepare the nano-Si C particle reinforced 7075 aluminum matrix composite. The microstructures of the composites have obvious spherulite characteristics, the average grain size is 30 渭 m, and the nano sic particles distribute uniformly in the grains. During the isothermal treatment of aluminum matrix composites, the grain size and roundness of solid phase depend on the isothermal temperature and time. The semi-solid billets prepared at the holding temperature of 590 鈩，

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