A Study Into the Mechanism(s) for the Electroplastic Effect in Metals and Its Application to Metalworking.
Abstract
High density (approx. 100,000 A/sq. cm.) d.c. current pulses (approx. 100 microsec) produced a marked decrease in the flow stress of polycrystalline metals (Al, Cu, Ni, Fe, Nb, W, Ti) tested in tension and in the force to draw Cu wire. A significant fraction of the decrease in stress or force could be attributed to drift electron-dislocation interactions, a major component of which was an electron wind with a push coefficienct of approx. 0.0001 dyn-sec/sq. cm. High density current pulses also enhanced the rates of sintering Al powder compacts, the recovery, recrystallization and grain growth of Cu and grain growth in Ti. In addition, the current pulses reduced the annealing twin frequency in Cu and sharpened the grain size distribution in Ti. No significant effect of current pulses on H-embrittlement of Fe at 300K was found. A continuous d.c. current of 650 A/sq. cm. retarded the tempering rate of a hardened tool steel. On the other hand, no changes were noted in the fatigue life of 316 stainless steel for continuous currents of 10 to 100 A/sq.cm., nor in the annealing behavior of Cu for currents of 200 to 3100 A/sq.cm. The deformation kinetics of Nb single crystals in the normal state were determined over the temperature range of 4.2 to 300K, employing a magnetic field at temperatures below 10K to retain the normal state. The results led to the conclusion that the rate controlling mechanism was thermally-activated overcoming of the Peierls hills by the nucleation and migration of kink-pairs on screw dislocations, the kink-pair energy for Nb being 0.66 ev.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 31, 1985
- Accession Number
- ADA163785
Entities
People
- Hans Conrad
Organizations
- North Carolina State University