Fabrication, characterization and analysis of improvements in mechanical properties of AA7075/ZrB2 in-situ composites

In this research work, AA7075/xZrB(2) [x = 0, 3, 6 and 9 volume fraction] in-situ composites have been fabricated by exothermic chemical reactions between the inorganic salts K2ZrF6 and KBF4 with aluminum melt at 900 degrees C. The fabricated composites were characterized using Optical Microscope (OM), Field Emission Scanning Electron Microscope (FESEM) and Transmission Electron Microscope (TEM). The microhardness, yield strength and ultimate tensile strength (UTS) were evaluated. Energy Dispersive Spectroscopy (EDS) and X-ray Diffraction (XRD) depict the presence of ZrB2 particles in the matrix with-out formation of any other inter-metallic compounds. The fabricated castings with 30 min holding time of melt were characterized with FESEM and the mechanical properties were evaluated and compared with the results of fabricated castings with 60 min holding time of melt. The size of ZrB2 particles formed in the Aluminum Matrix Composites (AMCs) was found from 2 to 9 mu m with different shapes like cubic and pyramid. The reduction in grain size of Al-rich phase of the AMCs was observed from TEM. The improvements on mechanical properties have been found with successive added volume fraction of ZrB2 particles in AMCs with 60 min holding time of melt. The effect of strengthening mechanisms on yield strength was calculated experimentally and theoretically and its results were tabulated. (C) 2019 Elsevier Ltd. All rights reserved.