The synergy between texture evolution and grain refinement in a BCC steel

Abstract

ABSTRACT This work investigates the synergy between texture evolution and grain refinement in ultra-low carbon body-centred cubic (BCC) ferritic steel. In this regard, experiments and polycrystal plasticity for ambient compressive deformation in low (up to ϵ≈0.22) and moderate (ϵ≈0.22−0.69) strain regimes were carried out. The tests were interrupted at intermediate strains for microstructure and texture characterisation. It was observed that the change in texture to γ -fibre ( { 111 } ∥ Compression direction ( CD ) ) and the formation of θ -fibre ( { 100 } ∥ CD ) up to ϵ ≈ 0.22 contributes towards lattice bending, resulting in grain size reduction from ∼ 104 ( 23 ) μ m to ∼ 23 ( 6 ) μ m . Simultaneously, crystallite size decreases, and statistically stored dislocations (SSD) and geometrically necessary boundaries (GNB) increase rapidly. Thus, resulting in an abrupt decrease in strain hardening rate (SHR). From ϵ ≈ 0.22 − 0.69 , the γ and θ -fibre broadens and θ -fibre intensity increases. The low GNB density increase indicates insignificant deformation-induced lattice curvature formation within grains, resulting in SSD intensification. Thus, leading to elongated grains with sluggish grain size decrease to ∼ 17 ( 4 ) μ m and a lesser decrease in SHR. The α -fibre could not evolve due to the dispersion of 110 axes along the axisymmetric radial direction due to axial deformation. The polycrystal model could appropriately simulate strain-hardening behaviour and texture evolution.