Grain boundary engineering for intergranular fracture and creep resistance

Conference · Tue Dec 31 04:00:00 EST 1996

OSTI ID:468832

Palumbo, G; Lehockey, E M; Lin, P ^[1]

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1. Ontario Hydro Technologies, Toronto (Canada); and others

The effect of special grain boundary frequency on the bulk creep performance of 99.99% Ni at 84 MPa and 450{degrees}C (grain boundary sliding regime). Increasing the frequency of `special` grain boundaries (by thermomechanical processing) from 13% to 66% results in a 16-fold reduction in steady state creep rate and a 6-fold reduction in primary creep strain. Consistent with the previous intergranular fracture analysis, a moderate increase in special boundary frequency from 13% to 45% yields the greatest reduction in the creep strain parameters. Microstructural evaluation of the specimens following testing to 1.8% total strain showed that (1) cavitation had occurred exclusively at general grain boundaries (i.e., {Sigma}>29) and (2) no cavities were formed in the material containing 66% special grain boundaries. The results of this study provide considerable promise for a `grain boundary engineering` approach towards the mitigation of intergranular-creep and -fracture in practical engineering materials.

• OSTI ID: 468832
• Report Number(s): CONF-960877--
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CREEP
FRACTURE PROPERTIES
GRAIN BOUNDARIES
MICROSTRUCTURE
NICKEL