Despite the widespread use of laser heat treatment, a fundamental understanding of austenite formation kinetics at high heating rates remains a challenge. This gap is addressed by developing a novel model that uniquely accounts for the initial pearlite colony size and interlamellar spacing as critical input parameters. The model's predictions are validated against experimental observations, where the spatial variation of hardness reveals a distinct two-zone microstructure: a fully austenitized region and a partially transformed intercritical layer. The results show that the relative size of these zones is directly controlled by the initial microstructure. This research provides a crucial insight that austenite formation under rapid heating conditions occurs with negligible superheating, which is essential for optimizing laser processing parameters to achieve a desired microstructure.

This study investigates the sub-structure of IF steel in three conditions: cold rolled, statically recovered, and warm rolled. After both cold and warm rolling, the steel exhibits the typical 〈110〉//RD and 〈111〉//ND fiber textures. Considering the short-range misorientation gradient ∆θ/∆x to assess locally stored energy variations, it was observed that 〈111〉//ND grains exhibit significantly higher gradients than 〈001〉//ND grains in all conditions. In the statically recovered conditions, the ∆θ/∆x values are significantly reduced compared to the cold rolled condition, but these values are significantly higher than those of the dynamically recovered after warm rolling. The strongly reduced orientation gradients in the 〈111〉//ND grains after warm rolling may reduce the nucleation potency of these orientations in the ensuing recrystallization. This study enhances our knowledge of deformation microstructure as a function of rolling temperature and is relevant in explaining reported differences in annealing textures during static recrystallization after cold vs warm rolling.