Microstructures, Mechanical Properties and Thixoformability of TiB2/Al Composite Prepared by Ultrasonic-Assisted Squeeze Casting

In this work, the 4 wt.% TiB 2 /Al composite with non-dendritic microstructures was fabricated by ultrasonic-assisted squeeze casting. The microstructures and mechanical properties of as-cast composites solidified under different casting temperatures were studied. Furthermore, a short process semisolid billet preparation route was developed, and hereby the thixoformability of as-cast composite was analyzed via thixoforging a complex-shaped part. The semisolid microstructure evolution, microstructures, and mechanical properties of thixoforged part were investigated. Results showed that the decreasing of the casting temperature was helpful to generate non-dendritic microstructures and improve the mechanical properties. When casting billet was partially remelted at 628 °C for 5 min by induction heating, the ideal semisolid billets consisting of fine and near-spherical solid grains were generated. The average grain size and shape factor were 66.9 μm and 0.85, respectively. A kind of connecting rod with favorable forming quality was successfully forged from the as-cast billet based on short process thixoforging. The yield strength, ultimate tensile strength and elongation of thixoforged part (I-beam region) were 160.81, 317.21 MPa and 19.14%, respectively, which were improved by deformed solid grains, refinement of TiB 2 particles and eutectic phases compared with the casting billets.