UBC Theses and Dissertations
Growth and deformation of copper whiskers Shetty, Mangalore Nagappa
Copper whiskers were grown by the hydrogen reduction of the halide vapours. The substrate and the whiskers were examined for growth morphologies. Whiskers of (100), (110) and (111) orientations in the diameter range 30-400μ were tested in tension. Differences in the work hardening characteristics of (111) and (100) whiskers were discussed in terms of the different kinds of jogs formed in the two orientations. Analysis of the diameter dependence of the yield stress resulted in a 1/d relation based on the assumption of surface nucleation of dislocations. Temperature and strain rate change experiments were made on (110) whiskers. Activation distance and activation energies were used to determine a rate controlling mechanism. At low temperatures, cross slip and intersection processes were indistinguishable, while at higher temperatures, cross slip is rate controlling. From the calculated activation distance and for a given rate controlling dislocation mechanism, stacking fault energies were estimated for copper and other FCC metals. A twinning model was proposed based on the idea of failure by recombination of a Lomer-Cottrell barrier.
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