A principal strengthening mechanism in high strength low alloy (HSLA) steels arises from the ultra-fine grain sizes developed during thermomechanical processing. Strain induced precipitation of NbC in the γ-Fe phase promotes a fine grain size on transformation to α-Fe. A detailed understanding of the strain induced precipitation mechanism has hitherto proved impossible because the dislocation structure present in the γ-Fe is lost on transformation. In this paper we report the behaviour of a new model alloy (Fe-30Ni-1.6Mn-0.1Nb-0.1C(wt%)) which does not transform on cooling to room temperature. Weak beam dark field and electron spectroscopic imaging is used to determine the distribution of the NbC with respect to the deformed structure.
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