Strengthening a Medium-Carbon Low-Alloy Steel by Nanosized Grains: The Role of Asymmetrical Rolling

Abstract

A medium-carbon low-alloy steel was prepared via the asymmetric rolling process with different ratios of upper and down roll velocities. Subsequently, the microstructure and mechanical properties were explored by using SEM, EBSD, TEM, tensile tests and nanoindentation. The results show that asymmetrical rolling (ASR) can significantly improve strength while retaining good ductility compared with conventional symmetrical rolling. The yield strength and tensile strength of the ASR-steel are 1292 ± 10 MPa and 1357 ± 10 MPa, respectively, which are higher than the values of 1113 ± 10 MPa and 1185 ± 10 MPa for the SR-steel. The ASR-steel retains good ductility of 16.5 ± 0.5%. The significant increase in strength is related to the joint actions of the ultrafine grains, dense dislocations and a large number of nanosized precipitates. This is mainly because of the introduction of extra shear stress on the edge under asymmetric rolling, which induces gradient structural changes hence increasing the density of geometrically necessary dislocations.

Analysis of the Asymmetrical Rolling of Ultra-Thin Strips Considering Elastic Deformation of the Strips

“…Amegadzie et al [23] conducted an asymmetrical rolling experiment to investigate the influences of rolling parameters on the mechanical properties of AA6061. Li et al [24] found the strengthening mechanism of medium-carbon low-alloy during asymmetric rolling. Xiao et al [25] employed asymmetrical rolling to refine grains in order to investigate the mechanical properties of pure titanium foils.…”

Analysis of Mechanical Parameters in Multi-Pass Asymmetrical Rolling of Strip by Slab Method

“…Lin et al [ 27 ] investigated the effects of different speed ratios on the homogeneity of through thickness microstructure and texture. Li et al [ 28 ] explored the microstructure and mechanical properties of a medium-carbon low-alloy steel prepared via the asymmetric rolling process with different speed ratios and suggested that strengthening is mainly because of the introduction of extra shear stress on the edge under asymmetric rolling. In the exploration of the mechanical properties of pure titanium foils, asymmetrical rolling was employed by Xiao et al [ 29 ] in the grain refinement process to produce compressive strain and shear strain.…”