Synthesis of Al7075/TiB2-Al2O3 In-Situ Hybrid Composite by Stir Casting Method

In this study, mechanically milled (MM) Al-24TiO 2 -20B 2 O 3 powder in molten Al7075 matrix was used in order to fabricate in-situ TiB 2 and Al 2 O 3 reinforcements in Al7075 matrix. Differential thermal analysis (DTA) examination was adopted to find reaction temperature between milled Al, TiO 2 , and B 2 O 3 powders. X-Ray Diffraction (XRD) patterns showed the existence of TiB 2 and Al 2 O 3 peaks (750 °C at Ar atmosphere) in MM powder. Scanning Electron Microscopy (SEM) results revealed the uniform distribution of TiO 2 and B 2 O 3 particles in the aluminum matrix. 6 wt.% MM powder was added to molten Al7075 at 750 °C. The molten Al7075/TiB 2 -Al 2 O 3 composite was poured in copper mold. The stir casted composites were hot extruded at 465 °C with extrusion ratio of 6:1 and ram speed of 5 mm/s. The microstructures (optical microscopy and TEM) and mechanical properties (hardness and tensile testing) of samples were evaluated. TEM results showed that in-situ TiB 2 nanoparticles were formed. The tensile strength of extruded Al7075/TiB 2 -Al 2 O 3 composite was reached the value of 496 MPa. This result was around four times greater than that of the as cast Al7075 alloy.