This paper describes the microstructure of a Roman ferrous nail through its observation by transmission electron microscopy. The morphologies of pearlitic colonies and ferritic grains are detailed and the relationship between pearlitic colonies and ferrite in Roman nails is explicitly demonstrated for the first time. Observations also confirm the presence of dislocations in ferritic grains and attest to the existence of very small carbide precipitates that have not been pointed out previously in standard archaeometric studies.
The influence of starting point microstructures on the transformation mechanisms and mechanical properties of a micro alloyed steel after annealing in the α + γ region have been investigated. Three different microstructures: austenite, pearlite in a ferrite matrix and martensite were used as starting point microstructures for the production of dual (α + ά) phase structures in the test steel. Photomicrographs obtained from metallographic examination of the heat treated samples were used as criteria for the assessment of results obtained from impact toughness and hardness testing. The results obtained showed that the transformation mechanisms and hence the morphology of ferrite -martensite microalloyed steels are strongly influenced by their initial microstructural details. Ferrite -martensite structures produced via the intercritical quench (IQ) treatment, with martensite as the starting point microstructure, have the best combination of hardness and impact energy.
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