Visualization of the Skin-Effect under Electric Pulsing and Its Influence on Structure and Strength of Cryorolled Aluminum Alloy

Using a high-speed thermal imaging camera, the temperature field on the surface of a 3 × 3 mm square sample of cryorolled high-strength aluminum alloy was recorded and analyzed during high-dense electropulsed processing. Uneven heating of the surface was observed, manifested by elevated temperatures in areas adjacent to the fins. The results of a comparative analysis of the alloy microstructure changes by SEM-EBSD method and the microhardness distributions along the specimen cross-section, induced by a current pulsing, are discussed. It was found that in zones of increased heating adjacent to the specimen’s surfaces, static processes of recovery and recrystallization of the highly work-hardened structure were more intense and accompanied by greater softening. It is concluded that this phenomenon is caused by the skin-effect inherent to electropulse treatment. Good agreement is demonstrated between the depth of the softened layer and the calculated current penetration depth into the conductor.