DEVELOPMENT OF THE TORSION PENDULUM AND EARLY RESEARCH ON GRAIN-BOUNDARY RELAXATION AND THE COLD-WORK INTERNAL-FRICTION PEAK

This paper gives a historical review of the early research on anelasti city during the author's stay at Chicago (1945-1949). Research topics suggested initially by Professor C. Zener were the study of the mechan ical properties of grain boundaries and of slip bands in metals by ane lastic measurements. The torsion pendulum and the moving coil twisting device were developed for this purpose, so that internal friction, dy namics modulus defect, creep under constant stress and stress relaxati on at a constant strain could be measured with the same specimen. The grain boundary peak (vs. temperature) was observed for the first time. A ''disordered atom groups'' model for high-angle grain boundaries wa s suggested. Similar internal friction peaks associated with slip band relaxation were observed in partially recrystallized cold-worked meta ls. Anomalous internal friction peaks were discovered in cold-worked a nd partially annealed Al-Cu solid solutions.