Abstract
Fe -10 Ni -7 Mn ( wt %) martensitic steel is a member of ultrahigh strength steels. This alloy is ductile in the solution annealed condition and shows good age hardenability but it suffers from severe embrittlement after aging. Discontinuous coarsening of grain boundary precipitates was found as the main source of embrittlement. In this paper the effect of cold rolling on the mechanical properties and phase stability of Fe -10 Ni -7 Mn steel was investigated. Cold rolling for 20%, 60%, and 90% were carried out on a solution annealed material with subsequent aging at 753 K. X- ray diffraction results and transmission electron microscopy (TEM) micrographs showed the presence of austenite in severely cold rolled samples. This austenite is likely formed as a result of deformation, and it seems to originate from a reverse transformation from bcc-martensite to hcp-martensite to austenite, stimulated by increasing the amount of deformation. This transformation improves the mechanical properties in this steel while in as annealed and aged condition it has premature fracture and zero ductility.
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