Phase transformation details in the three-phase region of AISI 304 stainless steel were revealed by quenching. At the initial stage of solidification, microstructure consisting of thin lathy ferrite and austenite forms directly from the melt. When forming lathy ferrite in the two-phase microstructure, Cr concentration at the solid/liquid interface remains almost unchanged and large numbers of Ni solutes are rejected into the liquid. When austenite forms, both Cr and Ni solutes are rejected into the liquid. When this process repeats several times, the concentration of Ni in the liquid becomes higher and Cr solute is slightly enriched. Thus, the retained liquid is transformed into austenite after forming the two-phase microstructure due to high concentration of austenite-stabilizing element. This phase transformation pattern was confirmed by consideration of the difference in Gibbs free energy. (c) 2012 Elsevier B.V. All rights reserved.
[fu, j. w.
; yang, y. s.] chinese acad sci, inst met res mat sci & engn, shenyang 110016, peoples r china.
; yang, ys (reprint author), chinese acad sci, inst met res mat sci & engn, shenyang 110016, peoples r china.