Hall-Petch effect and strain gradient effect in the torsion of thin gold wires

Gold wires with diameters of 20 and 50 mu m were annealed in the temperature range 330-750 degrees C to obtain different grain sizes. Torsion and tension experiments on these wires confirm that the Hall-Petch effect is stronger than the strain gradient effect in the small grain size region (below 5 mu m). With the grain size becomes larger, the strain gradient effect is evident. We find that these two mechanisms are synergistic, and this interaction strongly depends upon the grain size. (C) 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.