Microstructure, mechanical properties and fracture mechanisms of ZrB2 ceramic reinforced A7075 composites fabricated by stir casting

In the present work, 7075 aluminum-zinc alloy is strengthened with blends of ZrB2 particles using the stir casting technique. The reinforcements were added to the base alloy at weight percentages of 5, 10, and 15. An attempt was made to establish a correlation among microstructure, physical, and mechanical properties such as density, hardness, strength, and electrical resistivity. A linear relationship between the concentration of reinforcement of ZrB2 and electrical resistivity was observed. When compared with the base alloy, the hardness and density of the composites were considerably improved. A significant difference was observed in the mechanical properties such as the ultimate tensile strength, elastic modulus, and yield stress. With the current processing sequence, the composite with 15 wt. % exhibited an enhancement of about 34 % in tensile strength compared to base alloy. The tensile tested fracture surface and XRD imaging comprised and gave the evidence for weak linkage of the phases, which lead to fracture. The evidence for the strength properties was revealed in the Electron backscatter diffraction (EBSD) observations. The microstructure and the interfacial binding of various phases in the specimens were observed in the high resolution Transmission Electron Microscopy (HRTEM) graphs.