The thermal stability of nanograined pulsed-laser deposited Ni was studied by annealing free-standing thin films in situ in a transmission electron microscope. The observed grain growth was sporadic and catastrophic, as expected for abnormal grain growth. The large grains contained various defects including twins, dislocation lines, small dislocation loops and stacking-fault tetrahedra. This microstructure developed at annealing temperatures as low as 498K, and was stable at the annealing temperature. The proposed sources of the defects, and especially the stacking-fault tetrahedra, were the grain boundaries; which had excess free volume. This defect source provided an insight into the structure of the deposited grain boundaries. This had important consequences for the macroscopic mechanical properties of nanograin pulsed-laser deposited Ni.

Defect Structures Created during Abnormal Grain Growth in Pulsed-Laser Deposited Nickel. K.Hattar, D.M.Follstaedt, J.A.Knapp, I.M.Robertson: Acta Materialia, 2008, 56[4], 794-801