Enhanced machinability of additively manufactured Ti-5553 tailored with Mo

• Adding Mo to L-PBF Ti-5553 gives a positive impact on its machinability. • The presence of α- and isothermal ω-phases leads to higher cutting forces. • Mo addition reduces the fluctuations in cutting force during the machining of Ti-5553. • Residual Mo particles can inhibit the formation of serrations in chip morphology. Tailoring the composition of titanium alloys with strategic additives to refine microstructure and enhance performance is a promising approach to overcome limitations associated with conventional alloy systems. Among these, molybdenum (Mo) has recently emerged as a potent bifunctional additive that promotes grain refinement, reduces phase heterogeneity, and improves the strength and ductility of Ti-5Al-5Mo-5V-3Cr (Ti-5553), a widely used aerospace alloy. However, the impact of Mo addition on the alloy’s machinability remains unexplored. This study evaluates the machinability of Ti-5553 modified with 5 wt.% Mo, produced via laser powder bed fusion (L-PBF), with a focus on cutting forces, tool wear, surface integrity, and chip morphology. With Mo addition, the tool flank wear reduced by a factor of three compared to Ti-5553, cutting forces stabilised, and the machined surface roughness reduced by nearly 50%. Furthermore, chip morphology reveals smoother, less serrated features in the Ti-5553+5Mo alloy, indicative of more stable shear behaviour during cutting. These findings demonstrate that targeted Mo addition, known to enhance the performance of additively manufactured Ti-5553 alloy, can simultaneously improve machinability.