Excellent tensile yield strength with ultrafine grain and tailored microstructure in plastically deformed Ti–Re alloys

Abstract

The pursuit of strong and ductile titanium alloys for critical structural applications remains a constant focus in metallurgical engineering research. To evaluate the microstructure evolution and strengthening effect of Rhenium (Re) addition, binary alloys of Ti–xRe (x = 0, 2, 4, 6 wt%) were fabricated via spark plasma sintering and hot extrusion techniques. Microstructure characterization by electron backscatter diffraction (EBSD) and transmission electron microscope (TEM) revealed the presence of equiaxed α and β phases in the extruded materials, with an increased fraction of β phase corresponding to higher Re concentrations. X-ray diffraction (XRD) analysis indicated lattice expansion in the β phase due to Re diffusion, suggesting solid solution formation and preferential diffusion of Re into the β phase. Moreover, Re increments of 4 and 6 wt% resulted in significant grain refinement towards the formation of ultrafine grains (0.8 and 0.6 µm, respectively). The extruded Ti–Re alloys exhibited a linear strengthening trend, with an increase of 250–300 MPa per 2 wt% Re added. The yield strength of Ti–6Re exceeded three times higher than that of commercially pure (CP) Ti produced via a similar process, while maintaining over 13 % elongation. Re increment was also found to influence the deformation behavior of the extruded Ti–Re alloys during tensile test. This comprehensive investigation provides valuable insights into the microstructural changes and strengthening mechanisms associated with the addition of Re in titanium alloys, contributing to the ongoing efforts in developing high-performance materials for critical structural applications.