SYMPOSIA PAPER Published: 01 January 1966



This sixth volume on “Advances in Electron Metallography” continues the fine tradition of its predecessors in providing a continuing record of advances in the fields of electron microscopy and electron probe X-ray microanalysis. The progressively increasing range of subject matter and coverage of these volumes reflects the broadening interests and scope of Subcommittee XI of Committee E-4. Indeed, recognizing this transition, a new name for Subcommittee XI, “Electron Microscopy, Diffraction, and Microprobe Analysis,” was approved by the executive committee of E-4 at the Sixty-eighth Annual Meeting. The first paper, by Gilpin et al, describes an electron microautoradiographic technique, which was developed to study the microscopic distribution of a radioactive isotope in steel specimens by electron microscopic examination of a gelled emulsion monolayer containing fine silver bromide particles. The resolution of the technique was estimated at about 0.1µ. Using tritium, H3, hydrogen migration through AISI 4340 steel was studied. The results surprisingly suggest that, though pronounced cathodic reaction occurs at the prior austenite boundaries, the volume migration is random and not through these boundaries. Under tensile stress, a hydrogen-charged specimen exhibited hydrogen migration to the region of maximum stress triaxiality. Phillips compares electron metallographic techniques with light microscopic and interferometric methods for study of slip line spacing and heights in a copper alloy with about 3 per cent cobalt. The electron metallographic methods (both replication and thin section) were found to have better resolution—especially in lateral resolution of slip line spacing—than light interferometry. Transmission techniques showed slip line spacings as small as 300 A; a new technique for gaining improved contrast at slip steps involved metal-shadow casting a one-sided thinned transmission specimen. The slip-step spacing and height in the aged alloy (precipitate size about 180 A) were similar to those in the solution-treated condition. Since dislocations easily penetrated the precipitate particles, this result is not surprising and suggests that precipitation hardening in this alloy is mainly due to coherency strain fields.

Author Information

Banerjee, B., R.
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Developed by Committee: E04
Pages: 1–3
DOI: 10.1520/STP46413S
ISBN-EB: 978-0-8031-6799-5
ISBN-13: 978-0-8031-6623-3