A systematic study of lattice imperfections in metal whiskers by laue method

Abstract

Investigations were made of lattice imperfections in straight cadmium, iron, and copper whiskers by analysing the Laue diffraction photographs of the whiskers recorded with a microfocus X‐ray source (focal spot ≈ 40 μm in diameter). Perfect whiskers gave single and sharp Laue spots. The other whiskers gave irregular shaped Laue spots, or Laue spots consisting of two fine components (doublets), or streak like Laue spots. None of the investigated perfect cadmium, iron, and copper whiskers was found to contain an axial screw dislocation. However, the lattice planes of these whiskers were found to be deformed in a complicated way. In imperfect whiskers, each set of parallel lattice planes which gave a Laue doublet, in fact consisted of two sets of parallel lattice planes, slightly misoriented with each other. The angle of misorientation was found to be ≈ 10′ for imperfect Cd whiskers. The angular deformation in the lattice planes of some imperfect Cd whiskers was few degrees of are. In perfect whiskers the lattice perfection did not change appreciably on studying different portions of the whiskers. The lattice imperfection in other whiskers decreased on going from the base towards the tip. On annealing, the Laue spots of perfect whiskers did not show appreciable change in the lattice imperfections. Imperfect whiskers, except the ribbons, showed a decrease in the lattice imperfections on annealing. An increase in the lattice and surface imperfections was observed on annealing the ribbons. The present results can be qualitatively explained by assuming that the growth has taken place at the steps provided by an axial screw dislocation or dislocations, which may themselves have annealed out during growth.