An Investigation of mechanical properties in accumulative roll bonded nano-grained pure titanium

Room-temperature accumulative roll bonding was employed to refine the grain structure in commercial pure titanium. The microstructural evaluations show reduction in the grain size from about 45 µm to about 90 nm upon six cycles of accumulative roll bonding while increase in the degree of deformation inhomogeneity, measured through micro-hardness testing. The yield stress and tensile strength of the nano-grained commercial pure titanium after the sixth cycle, 799 MPa and 989 MPa, were about 180% and 140% increase as compared with the as-received sample, 284 MPa and 415 MPa. A remarkable grain refinement during the initial cycles of accumulative roll bonding resulted in increasing strain hardening rate and decreasing strain hardening exponent. However, upon the initial cycles, the saturation in hardening led to nearly constant strain hardening rate and exponent.