Grain boundary sliding phenomena in polycrystalline solids

Technical Report · Mon Aug 01 04:00:00 EDT 1988

OSTI ID:6508046

Wilson, C H

At elevated temperatures (T > 0.4T/sub m/), grain boundary sliding (GBS) becomes a significant deformation mechanism which directly alters both the flow and failure properties of polycrystalline solids. In this work the nature of GBS, primarily in Incoloy 800H, is investigated in terms of the effects of stress, temperature and grain size on the flow behaviors obtained by using the load relaxation test. Flow behaviors are obtained for average grain diameters (d) of from 224 ..mu..m to 6 ..mu..m. The flow behavior of large grain size materials (d > 10 ..mu..m), plotted as logarithmic stress versus logarithmic strain rate exhibits a sigmoidal shape which is traditionally associated with the effects of grain boundary sliding (GBS) on creep deformation. For small grain size materials (d > 10 ..mu..m) the mechanical properties tend toward those characteristic of superplasticity as the grain size is decreased; the material becomes increasingly ductile and the strain rate sensitivity and material flow rate at a given stress increases. Reloading experiments and the observations of a scaling behavior with increasing level of work hardening show that the microstructure of the specimen during each test is stable. The change in flow behavior with decreasing grain size is shown to result from a change in the dominant mode of GBS accommodation. 42 refs., 59 figs., 4 tabs.

• Research Organization: Cornell Univ., Ithaca, NY (USA). Dept. of Materials Science
• DOE Contract Number: FG02-84ER45055
• OSTI ID: 6508046
• Report Number(s): DOE/ER/45055-23; ON: DE89007792
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360102* -- Metals & Alloys-- Structure & Phase Studies
360103 -- Metals & Alloys-- Mechanical Properties
CHEMICAL COMPOSITION
CRYSTAL STRUCTURE
CRYSTALS
DEFORMATION
DIAGRAMS
ENGINEERING DRAWINGS
GRAIN BOUNDARIES
GRAIN SIZE
HARDENING
INCOLOY 800
MECHANICAL PROPERTIES
MICROSTRUCTURE
POLYCRYSTALS
RELAXATION
SAMPLE PREPARATION
SHEAR
SIZE
SLIP
STRAIN HARDENING
STRAIN RATE
STRESS RELAXATION
TEMPERATURE DEPENDENCE