Simultaneous enhancement of strength and stability in commercially pure titanium via cryogenic pre-straining

In this study, the effects of pre-strain at both cryogenic temperature (CT) and room temperature (RT) on the tensile properties of commercially pure titanium (CP-Ti) are investigated, focusing on strength improvements without compromising ductility. Specimens were prepared by subjecting them to a consistent strain of 6% at both cryogenic and room temperatures. The tensile tests were conducted at room temperature on these pre-strained specimens. The cryogenically pre-strained specimen demonstrated a significant increase in ultimate tensile strength (UTS: 409 MPa) and strain hardening rate compared to the room-temperature pre-strained (UTS: 351 MPa) and as-received specimens (UTS: Furthermore, the cryogenic pre-strained specimen exhibited more uniform deformation, higher necking resistance, and enhanced material stability during tensile deformation relative to the room-temperature pre-strained specimen. These improvements are attributed to an increased strain hardening rate, likely due to greater dislocation storage facilitated by a higher twin fraction formed during deformation at cryogenic temperatures. Notably, the yield strength of the cryogenically pre-strained specimen was lower than that of the room temperature counterpart, possibly caused by a reduced dislocation density at the yielding onset. This study presents a novel approach to simultaneously enhance strength and material plastic stability in CP-Ti through cryogenic pre-straining without compromising elongation.