Hydrogen-induced cleavage fracture of Fe{sub 3}Al-based intermetallics

Journal Article · Sun Dec 01 04:00:00 EST 1996 · Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science

OSTI ID:438558

Qiao, L; Mao, X ^[1]

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1. Univ. of Calgary, Alberta (Canada). Dept. of Mechanical Engineering

Hydrogen-induced fracture of ductile Fe{sub 3}Al-based intermetallics was studied through mechanical testing, fracture surface observation, and in situ transmission electron microscopy (TEM) tests of tensile specimens. Mechanical properties of ordinary ductile X-80 pipeline steel (low-alloy steel) were tested and compared with Fe{sub 3}Al intermetallics. Elongations of the Fe{sub 3}Al alloy decreased from 14 to 10 pct, with increases in the strain rate from 10{sup {minus}6} to 10{sup {minus}3}/s. The elongation reduction of Fe{sub 3}Al was caused by the hydrogen-induced fracture. There was no elongation reduction when the testing was done in mineral oil. Non-necking occurred near the fracture section, and the fracture surfaces mainly consist of cleavage and partial intergranular morphologies. Elongation near the fracture surface of the Fe{sub 3}Al intermetallics was about 14 pct, which is the same as the total elongation. For the pipeline steel, however, an elongation near the fracture cross section was greater than 130 pct, which was much higher than its total elongation of 17 pct. In situ TEM observation on a tensile test sample showed crack propagation accompanied by dislocation plasticity. When the Fe{sub 3}Al was precharged cathodically, the crack tip was sharp. Its radius was much less than that obtained without hydrogen charging. The crack propagated along the grain boundary for the charged specimens, but penetrated the grain boundary for the specimen without hydrogen charging. Effects of hydrogen on plastic deformation and grain-boundary cracking are discussed in this article.

• OSTI ID: 438558
• Journal Information: Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science, Journal Name: Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science Journal Issue: 12 Vol. 27; ISSN MMTAEB; ISSN 1073-5623
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM ALLOYS
CRACK PROPAGATION
DISLOCATIONS
ELONGATION
FRACTOGRAPHY
FRACTURE PROPERTIES
GRAIN BOUNDARIES
HYDROGEN
INTERMETALLIC COMPOUNDS
IRON ALLOYS