Effects of LaB₆ additions on the microstructure and mechanical properties of a sintered and hot worked P/M Ti alloy

A trace amount of LaB₆ powder was added to P/M Ti and Ti–6Al–4V alloy to improve mechanical properties and refine the microstructure. After sintering, TiB whiskers and La₂O₃ dispersoids had formed in the microstructure. In a CP Ti alloy, the generation of secondary phases leads to a much refined microstructure, but the alignment of TiB whiskers led to a variation in mechanical properties. Open die forging (ODF) or powder compact extrusion (PCE) was carried out on sintered Ti–6Al–4V alloy to further improve the mechanical properties. This caused severe deformation and re-alignment of the TiB whiskers. Comparing the properties of hot worked Ti–6Al–4V alloy and Ti–6Al–4V alloy with boron additions, an addition of LaB₆ leads to slightly lower strength but gives significant better ductility. - Highlights: • LaB₆ powder was added to sintered and hot worked Ti and Ti–6Al–4V alloy. • TiB whiskers and La₂O₃ dispersoids formed in the microstructure. • Different alignments of TiB_w led to a variation in mechanical properties. • Hot working caused severe deformation and re-alignment of TiB_w. • An addition of LaB₆ is better than pure boron additions.