The effect of oxygen and stress state on the yield behavior of commercially pure titanium

Titanium alloys containing a majority volume fraction of the low temperature HCP α-phase have been known to display yield and creep strength asymmetries when deformed under uniaxial conditions at room temperature. This behavior has only been documented in materials alloyed with significant concentrations of aluminum (<∼10 at%); however, little work has examined the phenomenon in commercial purity alloys. In this study, the yield strengths of two commercial purity titanium alloy sheet materials (Grade 1 and Grade 4) are examined under tensile and compressive loading conditions. Yield strength asymmetry has been observed and has been found to be dependent on alloy composition and crystallite distribution relative to the deformation axis.