Thin films of Al, which had been deposited epitaxially onto (00•1) α-Al2O3 substrates, were thinned cross-sectionally in order to form nanowires. The Al wires, which consisted of two Σ = 3 twin variants, were strained in situ via differential thermal expansion between the wires and the substrate during transmission electron microscopy. Dynamic observations showed that the maximum dislocation activity occurred during the first heating cycle at up to 400C; with decreasing activity during further cycles. The {111}Al||(00•1)α interface acted as a source of dislocation half-loops. The motion of threading dislocations along the wires generated long trailing dislocation segments which were parallel to, and offset from, the {111}Al||(00•1)α interface. Dislocation multiplication occurred via the reaction of half-loops and extended threading dislocation segments at the wire boundaries and substrate interface. The Σ = 3 twin grains bisecting the wires were observed to be stable during thermal cycling at up to 400C, and their {2¯1¯1} boundaries were weak pinning sites.

In situ TEM Observation of Dislocation Motion in Thermally Strained Al Nanowires. B.J.Inkson, G.Dehm, T.Wagner: Acta Materialia, 2002, 50[20], 5033-47