Effect of layered heterogeneous microstructure design on the mechanical behavior of medium carbon steel

• Published in: Materials & design 2022-09, Vol.221, p.110953, Article 110953
• Main Authors: Du, Jinliang, Li, Jie, Feng, Yunli, Ning, Jiangli, Liu, Shuai, Zhang, Fucheng
• Format: Article
• Language: English
• Subjects: Annealing; Heterogeneous microstructure design; Mechanical behavior; Medium carbon steel; Warm rolling
• ISSN: 0264-1275; 1873-4197
• DOI: 10.1016/j.matdes.2022.110953

[Display omitted] •The multiscale lamellar structured medium carbon steel was fabricated by quenching and warm rolling which can be scaled up for industrial production.•The strength and ductility of medium carbon steels in layered heterostructures are close to low-alloyed high-strength steels.•The improved toughness is attributed to the hierarchical heterogeneous structure of the lamellar, particle dispersion distribution, and the three-level coordinated control of grain size.•A ripening model of cementite during annealing is proposed. A heterogeneous microstructure composed of multiscale ferrite (spanning ultrafine, fine, and coarse grains) and granular or short rod cementite was obtained by warm rolling pseudoeutectoid microstructure. Combined with the short-time annealing process, the deformation tendency of ferrite grains and the dissolution and precipitation of cementite were adjusted. The mechanical properties of medium carbon steel are close to that of low alloy high strength steel. It was found that the GNDs are distributed in a gradient at the interface of the soft domain, and the closer to the boundary the higher the density, which contributes to the occurrence of the hetero-deformation induced (HDI) hardening mechanism and provides additional strength and plasticity. The increase in elongation of the annealed samples is due to the recrystallization of ferrite and the redistribution of cementite, which realizes the combination of HDI mechanism, Orowan strengthening and annealing softening mechanism. Additional strengthening mechanisms are calculated and a physical model of cementite ripening during annealing is proposed. The tensile fracture shows that the cracks mainly propagate along the grain boundaries of the layered microstructure, and the high density of dimples can make the propagation path of the cracks tortuous and increase the elongation.