A study on the austenite-to-ferrite phase transformation in binary substitutional iron alloys

The massive transformation from austenite to ferrite (y --> x) in binary su bstitutional Fe-X alloys, where X represents successively about 1 or 2 at.% of Co, Cu, Mn, Cr or Al, is experimentally investigation by means of dilat ometry. The resulting transformation curves have been modelled by an interf ace-controlled growth model. laking the characteristics of the austenitic m icrostructure into account. The assumption of an Arrhenian temperature depe ndence of the interface mobility, defined as the ratio between the interfac e velocity and the driving force. is found to give a consistent picture of the observations with an activation energy for atoms crossing the interface of 140 kJ mol (1). The spurious presence of interstitial nitrogen is shown to have a significant effect on the mobility, as large as a factor 8 at co ncentration levels on the order of 10 (4). (C) 2000 Elsevier Science S.A. A ll rights reserved.