Fractography

About: Fractography is a research topic. Over the lifetime, 5043 publications have been published within this topic receiving 86068 citations.

Effects of reinforcement oxidation on the mechanical properties of SiC particulate reinforced aluminum composites

Abstract: The microstructures and mechanical properties of artificially oxidized and as-received silicon carbide particle (SiCp) reinforced pure aluminum and 2024Al composites were investigated. It was shown that surface oxidation of SiCp increased the tensile strength and fracture strain of the pure Al based composite. Diffusion of aluminum into SiO 2 during fabrication of the composite, which increased the diffusion bonding between the SiC particle and the aluminum matrix, is thought to be responsible for the increases in strength and ductility. However, the strength and ductility of the oxidized SiCp reinforced 2024Al composite were much lower than those of the as-received SiCp reinforced 2024Al composite. Based on the experimental results from DSC, TEM, EDX and SEM fractography analyses, it is suggested that the interfacial reactions related to SiO 2 depleted the magnesium in the matrix and subsequently decreased the amount of the age strengthening phase containing magnesium. The lower level of strengthening in the matrix and the formation of a thick interfacial reaction layer, which was continuous and brittle, finally led to the lower strength and ductility of the artificially oxidized SiCp reinforced composite.

Evaluation of Porous ZrO2‐SiO2 and Monazite Coatings Using NextelTM 720‐Fiber‐Reinforced Blackglas™ Minicomposites

Abstract: A procedure was developed to fabricate oxide-fiber-reinforced minicomposites with a dense matrix and evaluate two oxidation-resistant interface coatings, porous oxide (zirconia-silica mixture) and monazite. The coatings were evaluated using NextelTM 720-fiber-reinforced BlackglasTM-matrix minicomposites. Boron nitride (BN) coated and uncoated fibers were used as controls for comparison. The evaluation was based on ultimate failure strengths, fractography, and fiber pushin tests. All the composites that used fiber coatings had ultimate strengths significantly better than the control that used uncoated fibers. In addition, porous-oxide-coated fibers were found to be similar to BN-coated fibers in strength, fractography, and fiber pushin behavior. Monazite-coated fibers resulted in similar ultimate strengths but showed no appreciable fiber pullout. Fiber pushin tests showed that monazite debonds readily but frictional resistance is higher than for BN or porous oxide fiber coatings.

Correlation of microstructure with hardness and fracture properties of (TiC,SiC)/Ti-6Al-4V surface composites fabricated by high-energy electron-beam irradiation

Abstract: Correlation of microstructure with hardness and fracture toughness of (TiC,SiC)/Ti–6Al–4V surface composites fabricated by high-energy electron-beam irradiation was investigated in this study. The mixtures of TiC, SiC, or TiC+SiC powders and CaF 2 flux were placed on a Ti–6Al–4V substrate, and then the electron beam was irradiated on these mixtures using an electron-beam accelerator. The surface composite layers of 1.2∼2.1 mm in thickness were formed, and contained a large amount (up to 66 vol.%) of precipitates such as TiC and Ti 5 Si 3 in the martensitic matrix. This microstructural modification including the formation of hard precipitates and hardened matrix in the surface composite layer improved hardness. In situ observation of the microfracture process revealed that microcracks primarily initiated at precipitates, and that shear bands formed in the matrix between these microcracks. Thus, fracture toughness was determined mainly by the volume fraction of precipitates working as fracture initiation sites and partly by the matrix property interrupting the crack propagation.