Effect of Grain Size on the Tensile Deformation Mechanisms of Commercial Pure Titanium as Revealed by Acoustic Emission

The effect of grain size on the deformation mechanisms during different tensile stages in commercial pure titanium was investigated by acoustic emission (AE) at room temperature. The deformation mechanisms, dislocation slip, and mechanical twinning were found to be the two AE sources for all grain sizes throughout the experiments. Based on the AE features of frequency and energy, the AE signals stemming from the two deformation mechanisms were classified. As grain size increased, the AE activity and intensity attributed to twinning increased. The twinning activity was confirmed by optical microscope and scanning electron microscopy. The results showed that for the specimen with small-sized grains, the entire tensile deformation was mainly achieved by slip, and only slightly assisted by twinning. Deformation of the specimen with medium-sized grains was accomplished by combined slip and twinning. For the specimen with large grains, twinning was the more active mechanism during the early stages of the tensile tests, while slip played a larger role in the later stages of the tensile tests. This larger role of slip in the later stages occurred despite the notable increase in the amount of twinning.