ECAP에 의한 강가공이 저탄소 페라이트-펄라이트강의 역변태 거동에 미치는 영향

Abstract

The effect of heavy deformation by ECAP on reverse transformation from ferrite and pearlite to austenite during heating has been investigated in a plain carbon-manganese steel using a dilatometer and optical and electron microscopy. Pearlite first transformed to austenite up to about 790℃ and then ferrite changed to austenite in both ECAPed and unECAPed specimens. Austenite preferentially formed at the interface between pearlite and proeutectoid ferrite and at the pearlite nodule boundaries. The recrystallization of proeutectoid ferrite and pearlitic ferrite occurred in advance before the reverse transformation in the case of ECAPed specimen. Consequently, the reverse transformation kinetics of ferrite to austenite is not greatly different in ECAPed and unECAPed specimens. However, the reverse transformation of pearlite to austenite in the ECAPed sample was faster than that in unECAPed one because of enhanced decomposition of pearlitic cementite by ECAP.