In-situ observation of strain evolution in CP-Ti during uniaxial tensile loading

First results are presented for in-situ tensile loading experiments performed on the Powder Diffraction beamline at the Australian Synchrotron facility. For direct measurement of strain evolution, the beamline was fitted with a uniaxial tensile stage and a high-resolution CCD detector. Precise calibration of the experimental diffraction geometry, taking into account slight misalignment of the detector (pitch, roll, yaw), was achieved by simulation of the ring patterns recorded from the standard reference material LaB6 (660). The material examined was a commercially pure titanium strip, which from prior electron microscopy studies, was found to have an average grain size of ∼20-30 μm. Tensile specimens conformed to ASTM E8, with a gauge length of 25 mm. To probe the bulk material properties all experiments were performed at 20 keV. In these preliminary experiments, measurement of the relative change in the interplanar lattice spacing was used to monitor the elastic response in seven crystallographic orientations during the loading cycle. To overcome problems encountered with grain size and associated discontinuous Debye-Scherrer ring patterns, two strategies were implemented to measure the Bragg peak (2θB) positions. In cases where the radial integration routine provided inconsistent results for peak determination, a new approach based on determining the averaged sum of 2θB positions from individual spots making up the ring pattern was utilised. Results obtained for the diffraction elastic modulus were found to be in agreement with predictions based on the single-crystal and Neerfield-Hill crystal coupling models.