Dynamically recrystallized austenitic grain in a low carbon advanced ultra-high strength steel (A-UHSS) microalloyed with boron under hot deformation conditions

摘要

This research work studies the dynamically recrystallized austenitic grain size (D_(rec)) in a new family of low carbon NiCrCuV advanced ultra-high strength steel (A-UHSS) microalloyed with boron under hot deformation conditions. For this purpose, uniaxial hot-compression tests are carried out in a low carbon A-UHSS microalloyed with different amounts of boron (14, 33, 82, 126 and 214 ppm) over a wide range of temperatures (950, 1000, 1050 and 1100°C) and constant true strain rates (10~(-3), 10~(-2) and 10~(-1) s~(-1) ). Deformed samples are prepared and chemically etched with a saturated aqueous picric acid solution at 80°C in order to reveal the D_(rec) and examined by light optical (LOM) and scanning electron microscopy (SEM). The D_(rec) is related to the Zener-Hollomon parameter (Z), and thereafter the D_(rec) divided by Burger's vector (b) is related to the steady state stress (σ_(ss)) divided by the shear modulus (μ) (Derby model). Results shown that the D_(rec) in the current steels is fine (≈ 23 μm) and almost equiaxed, and the recrystallized grain size-flow stress relationship observed after of plastic deformation is consistent with the general formulation proposed by Derby. It is corroborated that boron additions to the current A-UHSS do not have meaningful influence on the D_(rec)