Role of hydrogen, sulfur and other impurities in intergranular fracture in iron

Conference · Tue Jan 01 04:00:00 EST 1985

OSTI ID:6468377

Shin, K S; Meshii, M

The intergranular fracture stress was investigated as a function of grain boundary concentrations of sulfur and/or H in polycrystalline MRC-VP iron specimens. The fracture energy was determined as a function of grain boundary sulfur concentration by analyzing the empirical relations with a modified Griffith equation. Two different effects of H, permanent and reversible, were identified. The permanent effect of H was caused by the formation of intergranular microcracks due to the precipitation of supersaturated H and recovered only partially after annealing at high temperatures. The size of microcracks was found to be proportional to the square of H concentration at grain boundaries. The predicted sizes of the microcracks agreed well with those determined metallographically. The present study clearly indicates that there is no synergistic effect between H and sulfur on intergranular fracture of iron regardless of whether the H effect is reversible or permanent. It was found that the primary effect of C is to displace sulfur from grain boundaries and thus to improve the grain boundary strength by reducing the embrittling effect of sulfur. The second effect of C is to increase the frictional stress to dislocation motion and thus to increase the apparent stress for intergranular fracture.

• Research Organization: Arizona State Univ., Tempe (USA). Dept. of Mechanical and Aerospace Engineering; Northwestern Univ., Evanston, IL (USA). Dept. of Materials Science and Engineering
• DOE Contract Number: AC02-76ER01367
• OSTI ID: 6468377
• Report Number(s): DOE/ER/01367-157; CONF-850823-5; COO-1367-157; ON: DE86001884
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360103* -- Metals & Alloys-- Mechanical Properties
CARBON
CARBURIZATION
CRACKS
CRYSTAL STRUCTURE
ELEMENTS
FRACTURE PROPERTIES
GRAIN BOUNDARIES
HARDENING
HYDROGEN
IRON
MECHANICAL PROPERTIES
METALS
MICROSTRUCTURE
NONMETALS
SULFUR
SURFACE HARDENING
SURFACE TREATMENTS
TRANSITION ELEMENTS