Study on fractography in the low-temperature brittle fracture of an 18Cr-18Mn-0.7N austenitic steel

Shi Cheng Liu, T. Hashida, H. Takahashi, H. Kuwano, Y. Hamaguchi

Research output: Contribution to journalArticle

29 Citations (Scopus)

Abstract

The fracture mode and crack propagation behavior of brittle fracture at 77 and 4 K in an 18Cr-18Mn-0.7N austenitic stainless steel were investigated using optical and scanning electron microscopy. The fracture path was examined by observing the side surface in a partially ruptured specimen. The relationship of the fracture facets to the microstructures was established by observing the fracture surface and the adjacent side surface simultaneously. Three kinds of fracture facets were identified at either temperature. The first is a smoothly curved intergranular fracture facet with characteristic parallel lines on it. The second is a fairly planar facet formed by parting along an annealing twin boundary, a real {111} plane. There are three sets of parallel lines on the facet and the lines in different sets intersect at 60 deg. The third is a lamellar transgranular fracture facet with sets of parallel steps on it. Fracture propagated by the formation of microcracks on a grain boundary, annealing twin boundary, and coalescence of these cracks. The observation suggests that the ease of crack initiation and propagation along the grain boundary and the annealing twin boundary may be the main reason for the low-temperature brittleness of this steel. A mechanism for grain boundary cracking, including annealing twin boundary parting, has been discussed based on the stress concentration induced by impinging planar deformation structures on the grain boundaries.

Original languageEnglish
Pages (from-to)791-798
Number of pages8
JournalMetallurgical and Materials Transactions A: Physical Metallurgy and Materials Science
Volume29 A
Issue number3
DOIs
Publication statusPublished - 1998 Mar

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Mechanics of Materials
  • Metals and Alloys

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