Change in electrical resistivity of commercial purity aluminium severely plastic deformed

Abstract

Commercial purity aluminium sheets were severely plastic deformed by accumulative roll bonding (ARB). Changes in electrical resistivity at 77 K and microstructure during the ARB process were traced up to 12 cycles, which corresponded to an equivalent strain of 10. The resistivity at 77 K increased with increasing number of ARB cycles, then saturated after about the sixth ARB cycle with a maximum increment of resistivity from starting material of about 1.1 n m. Since lattice defects affect the resistivity of metals, the internal dislocation density and the density of grain boundaries were evaluated from scanning transmission electron microscopy images using Ham's method and grain boundary maps obtained from electron back-scattering diffraction, respectively. The relationship between the change in resistivity and the lattice defects is discussed.

Optimization of electrical conductivity and strength combination by structure design at the nanoscale in Al–Mg–Si alloys

“…On should note that with this simple approach, the contribution of nanoscaled precipitates to the resistivity will be neglected. The contribution of crystalline defects to the resistivity of aluminum has been reviewed and experimentally investigated for SPD materials by Miyajama and co-authors [45]. Since their data show a relatively good agreement with their theoretical predictions, we propose to use here similar estimates for the constants: Dq vac = 26 nX m/at.%, Dq dislo = 2.7 Â 10 À25 X m 3 and Dq GB = 2.6 Â 10 À16 X m 2 .…”

Evaluation of Dislocation Density for 1100 Aluminum with Different Grain Size during Tensile Deformation by Using <i>In-Situ</i> X-ray Diffraction Technique

“…The development of severe plastic deformation technique, such as accumulative roll-bonding (ARB), 13) high-pressure torsion (HPT), 4) equal channel angular pressing (ECAP), 5) has facilitated fabrication of ultrafine-grained aluminum with average crystal grain sizes of several 100 nm. When the grain size in materials with conventional grain sizes is refined, their strength is known to empirically rise with the inverse square root of the average grain size, in accordance with the HallPetch relation.…”

“…Several methods can be used to evaluate the dislocation density, including electrical resistance measurements, 12) transmission electron microscopy (TEM), 13) and X-ray diffraction (XRD). However, electrical resistance measurements and TEM encounter specific problems.…”

Effects of Temperature and Strain Rate on Plastic Deformation of Ultrafine-Grained Copper Prepared by Equal-Channel Angular Pressing

“…Dislocations and dislocation networks can be seen clearly. As discussed previously, 16,23) much clearer dislocation images can be obtained from STEM images compared with conventional TEM images. With Ham's interception method, 24) dislocation density μ in ECAPed specimens was evaluated and the results are shown in Table 1.…”