The Development of High Performance Ti-6Al-4V Alloy via a Unique Microstructural Design with Bimodal Grain Size Distribution

The present work deals with the strengthening of Ti-6Al-4V alloy by creating a unique microstructure with bimodal grain size distribution, termed as “harmonic structure.” The Ti-6Al-4V compacts with harmonic structure design were successfully prepared via a powder metallurgy approach consisting of controlled mechanical milling and spark plasma sintering of the pre-alloyed Ti-6Al-4V powders. The microstructural evolution at each stage of processing has been investigated to establish a correlation between the processing conditions and the microstructural evolution. The Ti-6Al-4V compacts with heterogeneous harmonic structure exhibited better mechanical properties as compared to their homogeneous fine/coarse-grained counterparts. An attempt has also been made to explain the deformation mechanism of the harmonic-structured Ti-6Al-4V specimens with the help of the experimental evidences. The superior mechanical properties of the harmonic structure Ti-6Al-4V were found to be related to the peculiar topological distribution of strong fine-grained and ductile coarse-grained regions, which promotes uniform distribution of strain during plastic deformation and results in improved mechanical properties by avoiding the localized plastic deformation in the early stages of deformation.