Nucleation and growth of surface texture during α-γ-α transformation in ultra low carbon steel alloyed with Mn, Al and Si

摘要

It is well known that surface energy anisotropy is one of the driving forces for the orientation selection at the metal-vapour interface. This affects the microstructure and texture evolution at the surface during phase transformation, which is an inherent feature of low-alloyed low-carbon steels. This paper investigates the nucleation and growth of the surface texture by orientation contrast microscopy. It has been found that the surface texture is dominated by {001} oriented grains, which exhibit a remarkable orientation gradient from the centre of the grain towards the edge. The {001} oriented grain centre gradually rotates around a <110> axis in small incremental steps when nearing the edge of the grain. Towards the edge the accumulated rotation angle has commonly reached a value of 30°. Underneath the surface grains (~ 30 μm) the bulk texture consists of a strong γ-fibre.