Roman Nail, Broken below Head, Found in Vicenza, Italy – Montage of the broken Roman nail (left, Klemm’s I) and view of a typical large slag stringer (2% nital).
Patches of as-quenched martensite were found in the carburized nail head. Picral will not etch as-quenched martensite, but it will etch tempered martensite.
Patches of as-quenched martensite within the pearlitic carburized head revealed using 10% sodium metabisulfite.
Most of the head, but not in the center of the top face, was carburized. Etched with Beraha’s sulfamic acid 3/1 reagent (left) and Klemm’s I (right) and imaged with polarized light and sensitive tint.
Montage of the microstructure starting from under the head at the left corner (C –carburized) and going inward at the top of the shaft (AF –acicular ferrite; S –slag; EF –equiaxed ferrite). Klemm’s I, polarized light and sensitive tint used to image the structure.
Microstructure in the shaft (left, center and right side, respectively) revealing numerous mechanical twins (Neumann Bands) and slag stringers in a ferritic matrix. Beraha’s sulfamic acid (3/1) solution used with polarized light and sensitive tint to image the microstructure.
Higher magnification view of the mechanical twins in the ferrite in the shaft above the break (Beraha’s 3/1 sulfamic acid reagent, XP+ST).