Effect of purity on the internal morphology of blisters on aluminum surfaces

Abstract

This study investigates the effect of purity of aluminum on the morphology of blisters formed on aluminum plates. To this end, aluminum samples with 99 % and 99.99 % purities are prepared, and blisters are generated on the sample surfaces through atmospheric heat treatment. Subsequently, the morphology of blisters on the surface and within the samples are examined using an ion-milling method and field-emission scanning electron microscopy (FE-SEM) with energy-dispersive X-ray spectroscopy. The FE-SEM images reveal that the shape and number density of the blisters vary with the purity of aluminum. The voids under the blisters are spherical when the purity of aluminum is greater than 99.99 % compared to flatter voids when the purity is 99 %. This morphological change is attributed to the local stress caused by neighboring impurity precipitates, and this is theoretically confirmed through Eshelby's ellipsoidal inclusion analysis.

Keywords

• Hydrogen
• Blistering
• Aluminum
• Purity
• Heat treatment