【摘要】 为探究SiCp/Al复合材料中两相材料相互作用引起的力学性能差异，研究微观尺度下法向载荷变化对SiCp/Al复合材料形变和去除的影响。采用纳米压痕实验，基于Oliver-Pharr法测得其硬度和弹性模量，并对其压痕表面进行观察，结合有限元仿真分析产生力学性能差异的原因；同时，根据纳米压痕实验所得力学参数进行变载荷纳米划痕仿真，并配合实验后划痕表面观察结果分析材料的形变和脆塑性行为。结果表明：当金刚石压头作用于SiC颗粒时，颗粒出现破碎和二次压入现象，所测硬度与弹性模量小于单晶SiC的理论值；当金刚石压头作用于基体相时，由于SiC颗粒阻碍基体压入，复合材料的硬度与弹性模量测量结果偏大。在纳米划痕过程中，复合材料的去除形式随载荷变化体现为划擦、耕犁和切削阶段，其中的基体相通过塑性流动产生塑性脊堆积并伴随有涂覆现象，SiC颗粒则以脱黏、断裂破碎和拔出等脆性机制而去除，且SiC颗粒的二次压入、断裂、破碎和拔出是导致复合材料力学性能与单晶SiC的力学性能产生巨大差异的主要原因。随着划痕载荷增加，SiC体积分数为45%的SiCp/Al复合材料的去除机制更多取决于以塑性去除为主的基体相，而SiC颗粒则主要表现为脆性去除。更多还原

【Abstract】 Objectives: SiCp/Al composite is a kind of particle-reinforced metal matrix composite, which offers high specific strength and low density. It is widely used in electronic packaging, aerospace and automobile manufacturing.Although the presence of a large number of SiC particles improves the mechanical properties of the material, it also presents significant challenges in processing. As the volume fraction of SiCp/Al composite material increases, its mechanical parameters such as hardness improve, but a large number of surface defects appear during processing.To improve the surface machining quality and select better machining parameters, it is crucial to investigate the mechanical properties and the removal mechanism of SiCp/Al composites with medium or high volume fraction. Methods: Nanoindentation is a commonly used method for testing hardness, which can quantitatively characterize the hardness, elastic modulus and other mechanical parameters of materials. It provides a theoretical basis for predicting machined surface roughness. The load-depth curves of SiCp/Al composites under specific indentation load and rate can be obtained through nanoindentation experiments. The hardness and elastic modulus of SiCp/Al composites are determined using the OliverPharr method. Due to the presence of a large number of SiC particles in the SiCp/Al composite, different failure behaviors are observed when the diamond indenters applies loads to the SiC particles, Al matrix, and two-phase interfaces, resulting in significant differences in measured hardness and elastic modulus. After the indentation experiment, scanning electron microscope(SEM) is used to observe the indentation surface morphology, and the ABAQUS finite element software is used to simulate the indentation process of SiCp/Al composites. The reasons for the differences in mechanical properties are then analyzed based on the finite element simulation results and the experimental indentation surface defects. Results: It is found that when the diamond indenter acts on SiC particles, the experimental values of hardness and elastic modulus of the material are the largest, with average values of 22.75 GPa and 190.78 GPa, respectively.When the indenter acts on the matrix phase, the average values of hardness and elastic modulus are 1.39 GPa and 66.52GPa, respectively. For the interface between the two phases, the average hardness and elastic modulus measured are 4.62 GPa and84.38 GPa, respectively. Additionally, the nanoscratch experiment simplifies the complex interaction between abrasive particles and the workpiece during grinding. It explores the brittle-plastic transformation behavior and potensial surface defects of the material surface by applying loads to the workpiece. This is an effective method for studying the material removal form. The hardness and elastic modulus values obtained from the nanoindentation experiment are introduced into the scratch finite element simulation. A variable load of 0 to 400 mN is applied to the SiCp/Al composite, with the scratch speed fixed at 0.05 mm/s. The results show that the removal form of the material changes with the load during the scraping, ploughing and cutting stages. The matrix phase undergoes plastic plastic flow, causing plastic ridge accumulation with coating phenomenon, while the SiC particles are removed by brittle mechanisms such as debonding,breaking, and pulling out. Conclusions: In the indentation experiment, secondary indentation of SiC particles in SiCp/Al composites results in significant differences between the mechanical properties of SiC particles and the theoretical mechanical properties of SiC crystals. Due to fracture and breakage of the particles during the loading process of the diamond indenter, the test results tend to be exaggerated. As the scratch load increases, the removal form of SiCp/Al composites with a volume fraction of 45% replies more on the plastic removal of the matrix phase, while the removal form of SiC particles is mainly brittle. The brittle-plastic behavior of the material surface during machining, as analyzed by the nanoindentation/scratch experiments, provides a theoretical basis for predicting the material’s surface quality during machining.更多还原