Effects of Y addition on microstructure and mechanical properties of TiC/Ti6Al4V composites

Abstract

TiC/Ti6Al4V composites with different addition contents of Y element were fabricated successfully, and the effects of Y content on the microstructure and mechanical properties of the composites were investigated. The results show that the effects of Y can be considered into two ranges, the one is 0.1–0.5 wt.% and the other 1.0–2.0 wt.%. When the Y addition was in the first range, the morphology of the primary TiC in the composites was dendrite. With the increasing of Y content, eutectic TiC with flake shape or palpus shape began to separate out around the primary TiC and some indexes about microstructure and properties increased including the volume fraction of TiC, the hardness and the compressive strength of composites, while other indexes reduced obviously such as the primary dendrite arm-diameter, the secondary dendrite arm spacing and the abrasive property; On the other hand, when the Y content further increased from 1.0 to 2.0 wt.%, the refinement of dendritic TiC was not obviously. Meanwhile, the hardness and the compressive strength decreased, but abrasive property increased. The hardness and the compressive strength of composites reached the peak value at 0.5 wt.%Y. The refinement mechanism of Y was attributed to the combined effects of the increase in nucleation rate at the constitutional undercooling zone in front of the solid–liquid interface and the reduction in growth rate of TiC.