Microstructure, texture, and mechanical properties of inter-pass annealed CGPed low carbon steel after cold rolling

This study investigates the influence of post-cold rolling on the mechanical properties, microstructure, fracture surface, and crystallographic texture of low-carbon steel processed by Constrained Groove Pressing (CGP), a severe plastic deformation (SPD) technique. While CGP effectively refines material properties, the potential of combining it with post-processing cold rolling remains largely unexplored. Based on initial surface quality assessments, a 30% cold rolling reduction was selected for detailed analysis and further processing steps. A single CGP pass followed by 30% cold rolling significantly refined the grain size from 44.5 μm to 19 μm and enhanced mechanical properties, increasing UTS from 288 MPa to 504 MPa, dislocation density by over 400%, and hardness from 98.9 HV to 175 HV. Although ductility decreased to 8.5%, the material still exhibited a ductile fracture. Texture analysis revealed weak conventional α-fiber (<110>//RD) and γ-fiber (<111>//ND) textures while promoting shear-related ζ-fiber (<011>//ND) (2.2 × R) with strong Goss and Rotated Goss intensities. To optimize the strength–ductility trade-off, multi-pass CGP with inter-pass annealing at 400 °C followed by rolling was investigated. With progressive CGP passes and inter-pass annealing, the material exhibited a steady increase in strength and a noticeable reduction in ductility. Dislocation density and grain size gradually decreased, while hardness remained nearly unchanged throughout the process. After three passes, the material achieved a UTS of 580 MPa and an elongation of 3.6%, accompanied by grain refinement to 15 μm, which resulted in a brittle fracture. The crystallographic texture at this stage was dominated by the ζ-fiber (2.2 × R), with prominent Rotated Goss (2.54 × R) and {011}<111> (2.45 × R) components, alongside a weak Cube component. Texture evolution indicated that increasing the number of CGP passes did not linearly intensify texture, with both shear-induced and recrystallization-related components present. Overall, combining CGP, inter-pass annealing, and post-rolling offers an effective route to tailor the strength and ductility of low-carbon steel for advanced engineering applications.