Precision measurements of plastic deformation of β-CuZn at helium temperatures

By attaching condenser plates directly to the tensile specimen, creep rates of β-CuZn single crystals have been measured by the capacitance change in the strain-rate range of 10⁻⁷ to 10⁻⁵ s⁻¹ and at temperatures between 0.7 and 17 K using a ³He cryostat. Slope of the temperature variation of the stress to give a constant strain-rate decreases below 5 K and seems to level off at 0 K. The strain-rate sensitivity becomes almost constant below 2 K. The conventional activation analysis showed that an ARRHENIUS type strain-rate equation breaks down drastically below 5 K. For an effective temperature T^* which gives 2 K at 0 K and asympototically coincides with the testing temperature at 5 K, the experimental results can be fitted to the ARRHENIUS strain-rate equation with an activation enthalpy ΔH(τ) for the PEIERLS mechanism. The above result is interpreted in terms of the quantum-mechanical oscillation of the dislocations.