This project is designed to determine the effects of small alloying additions on the mechanism of high temperature creep cavitation and intergranular fracture. A model nickel-20% chromium alloy containing trace additions of cerium, boron, zirconium and magnesium will be used in this study. The specific research objectives include: (1) determination of the effects of trace elements on high temperature creep flow, cavity nucleation, intergranular fracture, and ductility; (2) determination of kinetics, mechanisms of grain boundary sliding and of stress relaxation phenomena by means of internal friction; measurement of cavity nucleation rates and associated parameters particularly with determination of surface free energies. The results will be analyzed and compared to models of cavity nucleation, creep rupture time and ductility.
