Mechanical response and microstructure evolution of commercially pure titanium subjected to repetitive bending under tension

The aim of this work was to study the cold formability of commercially pure Titanium alloy (Grade 2) by a testing methodology known as repetitive bending under tension (R-BUT). A dedicated test rig to perform the test was designed and fabricated to analyse the room temperature deformation behaviour of Ti-50A alloy sheet of 1.2 mm thickness. Samples from three different orientations were tested to investigate the effect of mechanical anisotropy on deformation behaviour. The results confirmed a significant increase in elongation to failure in samples subjected to R-BUT as compared to those subjected to standard tensile tests under similar conditions. This may be due to a delay in localised necking during R-BUT. Finite element analysis (FEA) suggested that a decrease in stress triaxiality in R-BUT could be the reason for enhanced formability of the materials compared to the conventional tension. Furthermore, electron backscatter diffraction (EBSD) study of the microstructure confirmed the development of highly strained regions that eventually lead to the formation of fine grains in the samples subjected to R-BUT. This could be due to a strain induced dynamic recovery process occurring during the test.