High-energy ball milling and pressure-assisted sintering of Ti-6Al-4 V alloy: a powder design approach for controlled microstructure, enhanced mechanical properties, and improved wear resistance

This work reports wear performance and mechanical properties of Ti-6Al-4 V alloy manufactured using powder metallurgy techniques, mainly, high energy ball milling and pressure assisted sintering. Alloyed powder was ball milled for several durations τ_m = 0, 2 h, 6 h, 12 h and 18 h in order to examine the structural alterations concerning the morphology, size, and nature of powder particles. SEM and laser diffraction results have shown refined powder particles with shape ranges between irregular oblate and prolate spheroids to flaky thin platelets with agglomerations for high milling durations, in the same line, XRD data revealed phase transformation from α-HCP to β-BCC phase accompanied with the formation of amorphous phase. The milled powders were hot pressed under vacuum; consolidated samples were obtained. Increased hardness < HV_0.2 > and Young’s values (E), < GPa > were detected reaching 622HV_0.2 and 268 GPa, respectively, for 18 h of milling. Continuously, metallographic observations have revealed the appearance of low angle grain boundaries. specific wear rate < W_S > , (mm³ Nm⁻¹) and wear volume W_V, (µm³) were evaluated using ball on disc tribometer with a 10 N load. The results show decreasing values of wear rate and volume, yet, taking into consideration SEM and 3D profilometer images, a tribolayer has formed on the 18 h sample limiting its matter loss. Correspondingly, distinctive wear mechanisms were noticed; abrasive wear and delamination for τ_m = 0 and short milling duration τ_m = 2, 6 h, abrasive wear and moderate ploughing for higher τ_m, while, for τ_m = 18 h adhesive third body wear was observed.