Fractal analysis of crack paths in Al2O3-TiC-4%Co composites
(1. Institute of Materials Science and Engineering, Ocean University of China,
Qingdao 266003, China;
2. Department of Materials Science and Engineering,
Shandong Institute of Architecture and Engineering, Ji’nan 250101, China;
3. Key Laboratory for Liquid Structure and Heredity of Ministry of Education,
Shandong University, Ji’nan 250061, China)
Qingdao 266003, China;
2. Department of Materials Science and Engineering,
Shandong Institute of Architecture and Engineering, Ji’nan 250101, China;
3. Key Laboratory for Liquid Structure and Heredity of Ministry of Education,
Shandong University, Ji’nan 250061, China)
Abstract: Al2O3-TiC-4%Co(volume fraction) composites(ATC) with high toughness (7.8±0.8 MPa•m1/2) and strength (782±60 MPa) were fabricated. In comparison with Al2O3-TiC composites(AT), the fracture toughness was significantly improved by 60%. The crack paths, generated by Vickers indentation on the polished surfaces of both composites, were analyzed from a fractal point of view to distinguish the possible toughening mechanisms involved. Quantitative evaluation of indentation cracks indicates that the crack deflection plays a more effective role. Cracks of the ATC composites show higher deflection angles and more deflections along the path. ATC composites present higher fractal dimension (D=1.07) than AT composites (D=1.02), which is directly related to the higher fracture toughness. A significant relationship between crack path and toughness is evident: the more irregular the geometry of the crack, the higher the fracture toughness.
Key words: Al2O3-TiC-Co; Al2O3-TiC; fractal; toughening mechanism; indentation crack