Microstructure and mechanical characterization of in situ synthesized AA6061/(TiB2+Al2O3) hybrid aluminum matrix composites

TiB2 and AI(2)O(3) particulates reinforced AA6061 aluminum matrix composites (AMCs) were synthesized by in-situ reaction of titanium (Ti) and boric acid (H3BO3) powders with molten aluminum. AMCs were fabricated using an electric stir casting furnace under a controlled environment. Heat flow curves of differential thermal analysis (DTA) showed that the synthesis temperature for the formation of TiB2 and AI(2)O(3) using Al-Ti-H3BO3 reaction system was 950 degrees C. The in-situ synthesized composites were characterized using XRD, FESEM, TEM and EBSD. XRD results revealed the formation of TiB2 and AI(2)O(3) particulates in the composite. FESEM micrographs revealed a homogenous distribution of both the particulates with good interfacial bonding. EBSD maps showed that the in-situ formed TiB2 and AI(2)O(3) particulates refined the grains of the aluminum matrix from 103 mu m at 0 wt% to 14 mu m at 15 wt%. AI(2)O(3) particles exhibited spherical shape while TiB2 particles displayed hexagonal and cubic shapes. The formation of ultrafine and nano scale thermodynamically stable TiB2 and AI(2)O(3) particles enhanced the microhardness and the tensile strength of the AMCs. The microhardness and the tensile strength were respectively 122 HV and 287 MPa at 15 wt%. (C) 2018 Elsevier B.V. All rights reserved.