Study on Dislocation Relaxation Peaks in Gold and Copper

An inverted torsion pendulum apparatus is described for the measurement of internal friction and dynamic modulus of metals over the temperature range 4° to 300°K after deformation in situ at 4°K. A detailed study of low‐temperature internal friction peaks in pure gold and copper was carried out with this apparatus. By comparison of the results with other reported measurements, the activation energies for the Niblett‐Wilks peak (E_N‐W) and for the Bordoni peak (E_B) in gold and copper were deduced as follows: $$E_{\mathrm{N-W}}\hspace{0.17em}\mathrm{was}\text{\hspace{0.17em}0.10\hspace{0.17em}}\mathrm{eV\; (for\; gold)\; and}\text{\hspace{0.17em}0.045\hspace{0.17em}}\mathrm{eV\; (for\; copper)}$$ ; and $$E_{\mathrm{B}}\hspace{0.17em}\mathrm{was}\text{\hspace{0.17em}0.19\hspace{0.17em}}\mathrm{eV\; (for\; gold)\; and}\text{\hspace{0.17em}0.12\hspace{0.17em}}\mathrm{eV\; (for\; copper).}$$ The internal friction below 15°K was found to rise for gold specimens deformed at low temperature. This rise is discussed in detail and suggests a relaxation peak below 15°K in cold‐worked gold.