MORPHOLOGICAL INSTABILITY OF δ-FERRITE/γ-AUSTENITE INTERPHASE BOUNDARY IN LOW CARBON STEELS

摘要

The dynamic behavior of the δ-ferrite/γ-austenite interphase boundary during δ/γ transform- ations was observed in situ with a confocal scanning laser microscope. The morphological instability and the growth of the finger pattern of the δ/γinterphase boundary were mainly focused on and studied in this work. It was found that the incoherent δ/γinterphase boundaries were always unstable with finger-like morphology during δ→γ transformation, which developed along δ-GBs at low supercoolings (< 7 K) and even into the δ-matrix at higher supercoolings for the transformation. At the same time, the finger spacing was measured and analyzed by using the classical constitutional supercooling and instability theories, which show good agreement between the observations and theories.