A low-cost strategy to enhance strength-ductility balance in AISI1045 steel

Abstract

In the current research, the impact of cold single-roll drive rolling as a low-cost technique on the microstructural evolution and mechanical properties of the AISI1045 sheet was studied. The microstructure of the as-received sample was a lamellar structure consisting of soft domains (proeutectoid ferrite) and hard domains (pearlite). The average grain size of proeutectoid α decreased from 24.5 μm (for the initial steel) to 7.1 μm (for the 60 % rolled steel) due to the occurrence of continuous dynamic recrystallization (CDRX). With an increase in the rolling deformation, the homogeneity of the ferrite and pearlite distribution in the microstructure was improved. Fragmentation and bending of the θ lamellae and several shear bands were seen in the 60 % deformed steel. By increasing the strain, the rotation of ferrite grains towards the θ fiber (as shear texture) increased due to the introduction of severe shear plastic deformation caused by the single-roll drive rolling. By increasing the intensity of ⟨100⟩‖ND (caused by the rolling deformation increasing), the amount of hardness enhanced less in the RD-TD section compared to the RD-ND section. As the rolling reduction increased to 60 %, the yield and tensile strength significantly enhanced and reached a maximum of 993.1 MPa and 1017.8 MPa, respectively. This was due to work hardening, grain refinement strengthening of α, and fragmentation of θ. The decreasing trend of the work hardening of the 60 % rolled steel was not similar to the strain hardening behavior of homogeneous materials, indicating that the number of geometrically necessary dislocations accumulated at the hard domain/soft domain interfaces was large, which was beneficial to the increment of work hardening in the second stage. After the rolling reduction increased, the proportion of dimples reduced, the depth and number of dimples decreased, and the plasticity reduced, which had a large effect on the secondary cracks.

Keywords

• AISI1045 steel
• Single-roll drive rolling
• Microstructure
• Mechanical properties