Study On The Fracture Behavior Of In Situ Particles Reinforced Metal Matrix Composites

As an outstanding representative of new materials, in situ particles reinforced metal matrix composites not only inherited the merits of traditional particles reinforced metal matrix composites, such as high specific strength, high specific stiffness, good electrical and thermal conductivity, high wear resistance, excellent damping properties and dimensional stability, but also overcame the defects of traditional particles reinforced metal matrix composites, such as too many internal defects, weak interfaces and critical clusters of particles and so on. Great advantages of its own makes in situ particles reinforced metal matrix composites to be high-profile in both researching and industrial fields.In this thesis, by taking in situ TiB₂/A356 composite as the target and combining test and numerical simulation, the fracture behavior of in situ particles reinforced metal matrix composites was studied. Not only provided key data for the industrial application of in situ TiB₂/A356 composite, but also made attempt and exploration in numerical simulation based on the microstructure of in situ particles reinforced metal matrix composites.In this thesis, the plane strain fracture toughness K_IC value of in situ TiB₂/A356 composite was obtained by taking test. The fact that the K_IC value of in situ TiB₂/A356 composite goes near to that of pure alloy matrix while other major mechanical properties of in situ TiB₂/A356 composite are much higher than those of pure alloy matrix makes it to be possible that substitute n situ TiB₂/A356 composite for pure alloy matrix in the future. By the combining image processing, CAD geometric modeling and finite element meshing techniques, the multi-particle microstructural finite element model of in situ particles reinforced metal matrix composites was built. In the process of building the multi-particle based on the scanning electron microscopic images, by substituting pits, formed by the detaching of some particles, for these detached particles, the problem of traditional modeling method that not all particles in the image could be characterized was solved successfully. This opened a new way for the numerical simulation of in situ particles reinforced metal matrix composites.By using finite body tessellation method with image processing and using coefficient-of-variance of the mean near-neighbor distance as parameter, the quantitied estimate of the homogeneity of the particles in in situ particles reinforced metal matrix composites was realized, which provides powerful a tool for studies in connection with the homogeneity of the particles in processes of manufacturing and researching of the material. By setting baseline mode and getting the historical cure of the normalized stress intensity factor, the influence of the homogeneity of particles on the fracture behavior of in situ particles reinforced metal matrix composites was studied as well.