Investigation of TiB distribution characteristics on the microstructure of in situ TiB/Ti6Al4V-ELI manufactured by laser metal deposition

Abstract

This study presents the investigation of TiB distribution characteristics on the microstructure of in-situ synthesized TiB/Ti6Al4V single-track composites manufacture with laser metal deposition. Ti6Al4V alloy was reinforced by adding TiB2 ceramic at mass volumes of 0%, 1% and 2% for microstructure modification and mechanical properties enhancement. The TiB/Ti6Al4V composite was characterized using optical microscope (OM), scanning electron microscope (SEM), electron backscatter diffraction (EBSD) and microhardness. It was found that the addition of TiB2 resulted in the transformation of the prior β-grain into two types of morphologies of dendritic and columnar microstructures. Furthermore, the increase in the amount of TiB2 resulted in the reduction of the volume fraction of β-Ti phase, with the in situ formed TiB replacing and occupying the β-Ti positions. Deposition at 2% promoted the formation of unmelted TiB2 particles which promoted hardness increase to 496 ± 17 HV.