Transmission electron microscopy studies of the crystallography of b. c. c. /18R martensite in Fe-Mn-Al-C

Journal Article · Sun Jan 01 04:00:00 EST 1995 · Acta Metallurgica et Materialia; (United States)

DOI:https://doi.org/10.1016/0956-7151(95)90257-0· OSTI ID:6637124

Lee, W B; Chen, F R; Chen, S K; Wan, C M ^[1]; Olson, G B ^[2]

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1. National Tsing Hua Univ., Hsinchu (Taiwan, Province of China)
2. Northwestern Univ., Evanston, IL (United States). Dept. of Materials Science and Engineering

The 18R martensite phase was observed in the b.c.c. matrix of an Fe-25.8 wt% Mn-7.4 wt% Al-0.11 wt% C alloy, after cooling from high temperature. The crystal structure is determined from the selected area diffraction (SAD) and high resolution imaging techniques. The 18R martensite has an orthorhombic lattice with lattice constants a = 0.448 nm, b= 0.259 nm and c = 3.865 nm and is best described as an 18R(4[bar 2])[sub 3] rather than an 18R(5[bar 1])[sub 3] structure. The expression of 18R(4[bar 2])[sub 3] and 18R(5[bar 1])[sub 3] comes from the combined notation of Ramsdell and Zhdanov [Nishiyama, Martensitic Transformation, p. 75 (1978)]. The stacking fault density relative to the 18R(4[bar 2])[sub 3] structure is determined from high resolution imaging to be 0.096. Martensite crystallographic parameters such as orientation relationship, habit plane, shape strain direction and magnitude of lattice invariant shear are calculated using the CRAB theory, in good agreement with experimental observations. The Burgers vector of anticoherency dislocations and the shape strain direction were confirmed using the two beam technique and computer image simulation. The observed interfacial dislocation structure and choice of lattice correspondence are discussed in terms of near-CSL concepts.

• OSTI ID: 6637124
• Journal Information: Acta Metallurgica et Materialia; (United States), Journal Name: Acta Metallurgica et Materialia; (United States) Vol. 43:1; ISSN 0956-7151; ISSN AMATEB
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360102* -- Metals & Alloys-- Structure & Phase Studies
ALLOYS
ALUMINIUM ALLOYS
CARBON ADDITIONS
CRYSTAL STRUCTURE
CRYSTALLOGRAPHY
IRON ALLOYS
IRON BASE ALLOYS
LATTICE PARAMETERS
MANGANESE ALLOYS
METALLURGICAL EFFECTS
SAMPLE PREPARATION