Synthesis, characterization, and mechanical behavior of ultra-fine-grained Ti-6Al-5V alloy prepared by mechanical alloying and spark plasma sintering

The aim of this research is to focus on the fabrication and comparison of microstructural changes and mechanical properties of nanocrystalline Ti-6Al-5 V powders (milled from 0 to 120 h) and ultra -fine-grained Ti-6Al-5 V bulk samples through mechanical alloying (MA) followed by spark plasma sintering (SPS) at 1050 degrees C and 50 MPa. The variation in powder structural parameters and morphological behavior was examined using XRD and advanced electron microscopes (HR-SEM, HR-TEM). The 120 -hour milled Ti-6Al-5 V powders exhibited a crystallite size of around 12 nm with a lattice strain of 1.97% due to extensive plastic deformation, and a higher dislocation density (70.44 x10(15) m(-2)) produced during the prolonged MA time. XRD results of bulk SPS samples revealed dual phases (alpha-Ti, beta-TiAl), confirmed through EBSD and HR-TEM results. Uniform beta-TiAl crystals were formed over alpha-Ti crystals (around 82 nm) in the 120 h sample, whereas non -uniform distribution was observed in the 0 h sample (289 nm). Vickers hardness strength and ultimate compressive strength of the 120 h SPS Ti-6Al-5 V samples reached 8.02 GPa and 1.93 GPa, respectively. These values were 383% and 14.88% higher compared to the 0 h SPS Ti-6Al-5 V sample, attributed to the prolonged MA process introducing more structural changes and uniform distribution of beta-TiAl crystals over alpha-Ti crystals.