纳米压痕对颗粒增强金属基复合材料界面微区性能的研究

发布时间：2018-03-24 11:52

本文选题：金属基复合材料　切入点：纳米压痕　出处：《上海交通大学》2015年硕士论文

【摘要】：颗粒增强金属基复合材料中,增强体和基体的界面作为连接增强体和基体的重要“桥梁”,其性能对复合材料的综合性能十分重要。本文利用SiC颗粒(SiCp)增强Al基复合材料为模型材料,制备不同热处理条件下的试样,用纳米压痕技术表征界面微区力学性能分布规律,并结合界面微区组织结构的位错和晶粒尺寸分析,以及宏观拉伸试验结果,来探究界面附近过渡区和复合材料力学性能的关系。合理选择纳米压痕位置、间距对于有效表征SiCp/Al界面附近力学性能分布十分重要。当选择压入深度为120 nm,相邻间隔为1μm的压痕点,从颗粒穿过平缓界面向基体依次做压痕测试时,可以真实反映界面的硬度分布规律。SiCp/Al界面的硬度变化过渡区与基体的位错分布相一致。本文选择α-SiC颗粒和7A04铝合金,并用搅拌铸造法制备复合材料。通过挤压变形、固溶和时效处理,最终得到4种时效时间不同的试样,分别为挤压态、欠时效、峰值时效、过时效。在不同时效处理的样品上做压痕实验。根据不同试样的SiCp/Al界面硬度分布规律可知,峰值时效样品基体的硬度值最高,挤压态样品基体的硬度值最低。相较于挤压态和欠时效样品,峰值时效和过时效样品上的硬度变化区(过渡区)较小。前者约为2μm,后者约为6μm。对样品进行微区组织结构分析可知,位错集中区随着时效时间的增加而减小。这是由于时效过程中,析出相易在界面位错集中区域成核,而析出相的长大会导致位错的重排以及亚晶界的移动,从而引起位错减少。复合材料中基体的晶粒尺寸随时效时间的增加先减小后增大,也从侧面证实了时效过程中发生了回复再结晶,并影响了界面附近位错的分布。由复合材料宏观力学性能测试结果可知,4种不同时效处理的复合材料断裂应变随时效时间的增加而减小。这与时效过程生成的不同种类的沉淀相、以及界面的载荷传递能力有关。此外,实验证明时效处理的复合材料的强度和基体的强度成正比,不依赖于增强体和基体间的载荷转移。综上所述,用纳米压痕技术做微区力学性能表征可以作为评价颗粒增强复合材料宏观力学性能的一个标准,为实际块体复合材料的建模和优化设计提供实验依据。
[Abstract]:Particle reinforced metal matrix composites, The interface between reinforcement and matrix acts as an important "bridge" between reinforcement and matrix, and its properties are very important to the comprehensive properties of composites. In this paper, SiC particle reinforced Al matrix composites are used as model materials. Samples were prepared under different heat treatment conditions. The distribution of mechanical properties of interfacial microstructures was characterized by nano-indentation technique. The dislocation and grain size analysis of interfacial microstructures were combined with the results of macroscopic tensile tests. To explore the relationship between the transition zone near the interface and the mechanical properties of the composite. The spacing is very important to characterize the distribution of mechanical properties near the SiCp/Al interface effectively. When the indentation point with a depth of 120nm and an adjacent interval of 1 渭 m is selected, the indentation is measured from the particle through the flat interface to the matrix. The hardness distribution of interface. The hardness transition zone of sic / Al interface is consistent with the dislocation distribution of matrix. In this paper, 伪 -SiC particles and 7A04 aluminum alloy are selected, and the composites are prepared by agitation casting. After solid solution and aging treatment, four kinds of aging samples with different aging time were obtained, which were extruded, underaged, and peak aging, respectively. Over aging. Indentation experiments were performed on samples with different aging treatments. According to the distribution of hardness at the SiCp/Al interface of different samples, the hardness of the matrix of the peak aging samples was the highest. Compared with extruded and underaged samples, the hardness of extruded samples was the lowest. The hardness change zone (transition zone) on the peak aging and overaging samples is smaller. The former is about 2 渭 m, the latter is about 6 渭 m. The dislocation concentration region decreases with the increase of aging time. This is because the precipitation phase is easy to nucleate in the interfacial dislocation concentration region during the aging process, and the growth of the precipitated phase will lead to the dislocation rearrangement and the movement of the sub-grain boundary. The grain size of the matrix decreases first and then increases. It is also confirmed that the recovery recrystallization occurs during aging. And the distribution of dislocation near the interface is affected. According to the test results of the macroscopic mechanical properties of composite materials, the fracture strain of the composites with four different aging treatments increases and decreases at any time, which is not related to the aging process. The precipitation phase of the same species, In addition, the experimental results show that the strength of the aged composites is proportional to the strength of the matrix and does not depend on the load transfer between the reinforcement and the matrix. The nanoindentation technique can be used as a criterion for evaluating the macroscopic mechanical properties of particle reinforced composites, which can provide experimental basis for modeling and optimization design of bulk composites.
【学位授予单位】：上海交通大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB33

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