Abstract
In this research work, the double differentiation mathematical method was used to identify more accurately the criti) and critical strain ) associated with the onset of dynamic recrystallization (DRX), which is based on cal stress changes of the strain hardening rate / ) as a function of the flow stress (Poliak and Jonas method, simplified by Najafizadeh and Jonas). For this purpose, a low carbon advanced ultra-high strength steel (A-UHSS) microalloyed with different amounts of boron (14, 33, 82, 126 and 214 ppm) was deformed by uniaxial hot-compression tests at high tempe). Results indicate that ratures 950, 1000, 1050 1100° ) and constant true strain rates 10 , 10 10 both and increase with decreasing deformation temperature and increasing strain rate. On the other hand, these critical parameters tend to decrease as boron content increases. Such a behavior is attributed to a solute drag effect by boron atoms on the austenitic grain boundaries and also to a solid solution softening effect.