In-plane tensile deformation and formability of pure titanium sheet at cryogenic temperature

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In this study, the in-plane tensile deformation in the rolling direction (RD) and transverse direction (TD), and sheet formability of pure Ti sheets were investigated at 100 and 298 K. A decrease in temperature from 298 to 100 K increased the difference in tensile deformation in the two directions. Notably, the Ti sheets exhibited a considerably higher tensile ductility in the RD at 100 K than at 298 K. In contrast, the ductility in the TD showed only a slight increase at 100 K compared to that at 298 K. This remarkable improvement was attributed to a prolonged plateau of strain hardening in the RD tensile deformation at 100 K, which hindered strain softening and suppressed necking during the tensile test. Prismatic <a> slip was the underlying factor for the notable strain-hardening behavior observed for tensile deformation in the RD at 100 K, while twinning was important to prolong the plateau strain-hardening stage. The sheet formability deteriorated at 100 K, despite an increase in the overall tensile ductility. This degradation was caused by the amplified anisotropy of the tensile deformation at 100 K. This anisotropy may facilitate cracking by inhibiting homogenous deformation accommodation in various in-plane directions. These findings will advance the understanding of the deformation behavior of pure Ti, especially at low temperatures, and guide the development of pure Ti with superior sheet formability.