Microstructure and Mechanical Properties of Ti6Al4V Alloy Modified and Reinforced by In Situ Ti5Si3/Ti Composite Ribbon Inoculants

This paper deals with a novel fabrication method (a vacuum rapid solidification technique) to prepare in situ Ti5Si3/Ti composite ribbon as inoculants to modify Ti6Al4V alloy to obtain titanium matrix composites (TMCs). Microstructure and morphology observations showed that the grain size of the TMCs was refined as the volume fraction of inoculants increased. The grain size of the TMCs can be refined from a grade of 650 mu m to about 110 mu m with a very small refiner adding ratio of 0.6% in weight. Thereafter, the mechanical properties of the TMCs, including their tensile strength, microhardness, impact properties, and resistant properties were improved obviously by adding the ribbon inoculants. The excellent grain refining and reinforcement effect can be attributed to the nano-sized Ti5Si3 refiner particles distributed homogeneously in the matrix, the well-banded particle/matrix interface, and the good wettability between the Ti5Si3 particles in inoculants and the Ti6Al4V alloy melt, which are benefit for the heterogeneous nucleation of the TMCs during solidification.