Effect of electric current on the creep deformation of lead

Using the impression test, the effect of electric current on the creep deformation of Pb was studied in the temperature range of 343-403 K and under the punching stress of 11.1-30.5 MPa. During the impression test of constant load, a direct electric current in a range of 0-5 A passed through the punch into the Pb-sample. A steady state creep with sudden jumps in the impression curves was observed. A power-law relation was used to describe the dependence of the steady state impression velocity on the punching stress. The average stress exponent increased from 3.2 to 4.0 with increasing electric current and the apparent activation energy was 36.0 kJ/mol for small punching stresses. For large punching stresses, the average stress exponent decreased with increasing electric current and the apparent activation energy decreased from 63.5 kJ/mol to 49.7 kJ/mol with increasing electric current from 0 to 5 A.