Anisotropic deformation behavior under various strain paths in commercially pure titanium Grade 1 and Grade 2 sheets

Abstract

In this study, the anisotropic deformation behavior in commercially pure titanium Grade 1 and Grade 2 sheets under various strain paths was examined. A small but sharp stress peak arose during tension following compression in the Grade 1 sheet when loaded in the rolling direction, and the occurrence of a stress peak was retarded when the sheet was subjected to cyclic loading; however, such behavior did not occur in the Grade 2 sheet. Similarly, the work-hardening rate was different between the initial and latter stages of compression following tension. These behaviors did not arise when the sheets were loaded in other directions. The type of active twin mode was different depending on the loading path. When loaded in the rolling direction in both Grade 1 and Grade 2 sheets, <1012> twinning and detwinning were active, respectively, during compression and tension following compression, whereas <1122> twinning and detwinning were active during tension and compression following tension. The twinning activity was much more pronounced in the Grade 1 sheet than in the Grade 2 sheet. The abovementioned stress-strain responses were presumed to result from twinning and detwinning activities as for magnesium alloy sheets. However, we concluded that the effect of twinning activity on the stress-strain curves was much smaller in the titanium sheet than in magnesium alloy sheets.