The as-quenched microstructures of twelve commercial s teels were observed using optical microscope and scanning electron microsco pe.It is found that the
packet martensite formed in medium and high carbon stee ls quenched from high temperature is not lath martensite, but rather fine
plate martensite. The formation
mechanism of the packet martensite was explored in detail from mar tensite
crystallography. Remaining the twi n relationship between the adjacent martensitic plates may significantly lower t he free energy barrier of
Martensite nucleation and growth, which may be realize d through changing the direction of homogeneous shear of austensite and the aust enitic direction,which is parallel with martensite platelet(i.e. double alterati on). The packet mechanism of twin boundary proposed is a common f ashion of transformation of fine plate martensite, that is to say, a new
nucleus with twin relationship will form at two sides of the old nucleus along the same habit plane for diminishing remarkably the boundary energy and the volume strai n energy, then forming
Packet plate martensite.
More abstracts about the Formation Mechanism of Packet Martensite in Medium and High Carbon Steels