Acicular ferrite and bainite microfractographic response

Abstract

The acicular ferrite (AF) and bainite (B) formation is practically connected with the same temperature range. The plates (laths) of the both austenite transformation products show displacive mechanism character. The differences are in nucleation sites. At the non-metallic inclusions or precipitates, the intragranular nucleated AF leads to the microstructure refinement consisting of interlocked plates (laths). The B is formed intergranularly. In impact toughness specimens (CVN-60) the fractal analysis of fracture surfaces was performed. In the AF the determined values of fractal dimenses are higher (cleavage fracture) than in the B microstructure. In the zone of ductile fracture, determined difference of fractal dimension is small.