The Influence of a Small Boron Addition on the Microstructure and Mechanical Properties of Ti-6Al-4V Fabricated by Metal Injection Moulding

Abstract

The effect of boron additions on the sintering behavior, microstructural development, and mechanical properties of a Ti-6Al-4V alloy fabricated by metal injection moulding (MIM) was studied. The addition of boron promotes a significant refinement of the microstructure by changing the microstructure from the typical lamellar to a more equiaxed morphology. The presence of both features: α colonies and α grains were confirmed by electron backscatter diffraction (EBSD) experiments. Furthermore, the pinning effect of TiB particles on grain boundary motion enhances the densification process due to the fact that the separation of pores and grain boundaries is suppressed. As a result of the refinement of the microstructure achieved by adding 0.5 wt% boron to the Ti-6Al-4V alloy, excellent tensile (σ0.2=787MPa, UTS=902 MPa and ε=12%) and fatigue (endurance limit=640 MPa) properties were obtained.