The effect of structure on the deformation of as-quenched and tempered martensite in an Fe-0.2 pct C alloy

Abstract

As-quenched and tempered martensite in an Fe-0.2 pct C alloy were subjected to tensile testing and structural characterization by light and transmission electron microscopy. The light temper, 400°C-l min, did not change packet morphology, but did reduce dislocation density, coarsen lath size and cause the precipitation of carbides of a variety of sizes. The yield strength of the as-quenched martensite was strongly dependent upon packet size according to a Hall-Petch relationship, but tempering significantly diminished the packet size dependency, a result attributed to packet boundary carbide precipitation and the attendant elimination of carbon segregation present in the as-quenched martensite because of autotempering. Examination of thin foils from strained tensile specimens showed that a well-defined cell structure developed in the as-quenched martensite, but that the random distribution of jogged dislocations and carbide particles produced by tempering persisted on deformation of the tempered specimens.