EFFECT OF SULFUR SEGREGATION TO GRAIN BOUNDARIES ON YIELDING, FLOW, AND FRACTURE OF NICKEL.

Tensile tests on nickel containing 10 ppm sulfur showed increased yield strength and fracture ductility with increased cooling rate from the recrystallization temperature. The yield strength results, together with changes in work hardening rate, were consistent with formation of sulfur clusters near grain boundaries. Ductility results, however, appeared to have a different cause. Increased ductility was correlated with decreasingly intergranular fracture, and was independent of yield strength. Films of a grain boundary phase which appeared to be Ni//3S//2 were observed in foils; Auger spectroscopy showed that boundaries were enriched in sulfur.