Processing of in situ Al₃Ti/Al composites by advanced high shear technology: influence of mixing speed

High shear technology (HST) is an advanced melt stirring technology with the intensive shear effect and allows the production of particle-reinforced Al composites (PAMCs) with a homogeneous particle distribution. In the fabrication process, applying an appropriate mixing strategy to obtain the excellent microstructure and properties is crucial. In this work, Al₃Ti/Al composites with different Al₃Ti volume fractions were fabricated in situ by high shear technology at various mixing speeds. The effect of mixing speed on the microstructure and mechanical properties was investigated. The results show that the reaction rate and Al₃Ti particle size increase with the increase of mixing speed. An intermediate mixing speed is appropriate for preparing the Al₃Ti/Al composite with a homogeneous distribution of reinforcing particles and low porosity. A lower mixing speed leads to severe particle agglomerations, which deteriorates the ductility of Al₃Ti/Al composites. A higher mixing speed results in high porosity within castings resulting from severe air entrainment, which significantly reduces mechanical properties. Young’s modulus improves with increasing the stiff Al₃Ti particle content and matches well with the predicted results as well. Tensile and compression strength and hardness are enhanced due to generating the uniform distribution of reinforcing particles and the matrix grain refinement.