Measurement of Electrical Resistivity during Tensile Deformation of Pure Ti

The observation and evaluation of lattice defects such as vacancies, dislocations, and grain boundaries are very important in materials design. Electrical resistivity measurement is superior to electron microscopy for obtaining average microstructural information, including density and type of lattice defects. The purpose of this study was to estimate changes in electrical resistivity during the tensile deformation of commercial-purity (CP) Ti. The electrical resistivity of a cold-rolled Ti sheet was measured at 77 K (ρ77) and 300 K (ρ300) along the rolling direction (RD) using a direct current (DC) four-point method to determine Matthiessen’s empirical relationship, ρ77 = α/(R – 1) + β, R = ρ300/ρ77. Plots of ρ77 versus 1/(R – 1) showed a linear relationship, and the values of α and β were determined to be 0.5266 and –0.0024, respectively. Changes in ρ77 during tensile deformation were estimated by substituting the resistance ratio R into Matthiessen’s empirical relationship. In the elastic deformation region, no remarkable change in the resistivity was observed. Therefore, the dislocation density did not change significantly. However, the resistivity did increase drastically near the yield point.