Optical observation of real materials using laser scanning confocal microscopy Part 2 – direct observation of ferrite nucleation sites in weld metal and heat affected zone

Abstract

High temperature laser scanning confocal microscopy (LSCM) allows in situ observation of microstructure changes that occur during welding thermal cycles in the weld metal and the heat affected zone (HAZ). To assess the effect of the inclusion type on the nucleation of intragranular acicular ferrite, direct verification of the nucleation site of the ferrite phase in the phase transformation of Si–Mn–Ti–B–Al weld metal was carried out by LSCM. Furthermore, it was observed that acicular ferrite can be formed in the HAZ by controlling the deoxidisation elements during the steel making process. The effect of the inclusion type on acicular ferrite formation in the HAZ was also assessed by tracking the ferrite formation behaviour during phase transformations by LSCM.