Application of High Pressure Gas Jet Mill Process to Fabricate High Performance Harmonic Structure Designed Pure Titanium

Through many years, conventional material developments have emphasized on microstructural refinement and homogeneity. However, "Nano- and Homogeneous" microstructures do not, usually, satisfy the need to be both strong and ductile, due to the plastic instability in the early stage of the deformation. As opposed to such a "nano- and homo-"microstructure design, we have proposed "Harmonic Structure" design. The harmonic structure has a heterogeneous microstructure consisting of bimodal grain size together with a controlled and specific topological distribution of fine and coarse grains. In other words, the harmonic structure is heterogeneous on micro- but homogeneous on macro-scales. In the present work, the harmonic structure design has been applied to pure-Ti via a novel powder metallurgy route consisting of controlled severe plastic deformation of the fine-sized powder particles via jet milling and subsequent consolidation by SPS. At a macro-scale, the harmonic structure materials exhibited significantly better combination of strength and ductility, under quasi-static tensile loadings, as compared to their homogeneous microstructure counterparts.