Pencil‐Shaped Necking of Thick Al Whisker Grown by Stress‐Induced Migration and Enhancement of Tensile Strength

This study aims to characterize the mechanical response of thick Al whiskers under tension. Wire‐shaped whiskers are fabricated by stress‐induced migration using an original sample structure. Straight and single‐crystal whiskers are suspended between a W probe tip attached to a micromanipulator and an atomic force microscope tip attached to a nanostage using electron beam irradiation hardening glue. Tensile tests are conducted by pulling the probe tip. A tensile strength of 1 GPa is obtained for a whisker with a diameter of 500 nm. Observations using a high‐voltage electron microscope show that the whisker is deformed by pencil‐shaped sharp necking with signs of recrystallization at the tip, which displays a novel mechanical response of Al whiskers. The obtained tensile strength is more than twice that of whiskers with similar diameters reported in the literature, indicating that the tensile strength of not only thin, but also thick whiskers can be enhanced by activating a different mode of deformation.