Effect of deformation on mechanical properties and lattice parameters in Ti-6Al-4V through cryo rolling

The present study deals with the study of mechanical properties, lattice parameters and texture analysis under cryo-rolling effect. Ti-6Al-4V sheets had been rolled at sub-zero temperature at different deformation percentages. Optical Microscope shows equiaxed microstructure at small deformation percentages which were further transformed to elongated microstructure with increase in deformation percentage due to rolling effect. Annealing after cryo-rolling leads to the formation of Widmanstätten structure along with equiaxed microstructure. Presence of deformation bands were observed through SEM. These bands get densified at the condition of high deformation percentage. With increase in the percentage of rolling deformation, the increasing trend of strength without any appreciable change in tensile deformation was observed through tensile test. The presence of orthorhombic phase had been observed through XRD, along with some unidentified peaks which were predicted as FCC peaks in some previous literatures. Further study of which is required through TEM. There is little localized variation in lattice parameters without much variation in the overall lattice parameter of each phase, which shows the presence of undeformed crystals in bulk. For HCP c/a ratio=1.59, for BCC a=3.32, and for orthorhombic a=3.84, b=2.62 and c=3.62. Annealing after cryorolling shows randomly oriented texture due to the recrystallization process. (author)