High-and medium-Mn(H/M-Mn)base lightweight steels are a class of ultrastrong structural materi-als with high ductility compared to their low-Mn counterparts with low strength and poor ductility.However,producing these H/M-Mn materials requires the advanced or high-tech manufacturing tech-niques,which can unavoidably provoke labor and cost concerns.Herein,we have developed a facile strategy that circumvents the strength-ductility trade-off in low-Mn ferritic lightweight steels,by em-ploying low-temperature tempering-induced partitioning(LTP).This LTP treatment affords a typical Fe-2.8Mn-5.7Al-0.3C(wt.％)steel with a heterogeneous size-distribution of metastable austenite embedded in a ferrite matrix for partitioning more carbon into smaller austenite grains than into the larger austen-ite ones.This size-dependent partitioning results in slip plane spacing modification and lattice strain,which act through dislocation engineering.We ascribe the simultaneous improvement in strength and total elongation to both the size-dependent dislocation movement in austenite grains and the controlled deformation-induced martensitic transformation.The low-carbon-partitioned large austenite grains in-crease the strength and ductility as a consequence of the combined martensitic transformation and high dislocation density-induced hardening and by interface strengthening.Additionally,high-carbon-partitioned small austenite grains enhance the strength and ductility by planar dislocation glide(in the low strain regime)and by cross-slipping and delayed martensitic transformation(in the high strain regime).The concept of size-dependent dislocation engineering may provide different pathways for de-veloping a wide range of heterogeneous-structured low-Mn lightweight steels,suggesting that LTP may be desirable for broad industrial applications at an economic cost.

Kwang Kyu Ko;Hyo Ju Bae;Eun Hye Park;Hyeon-Uk Jeong;Hyoung Seok Park;Jae Seok Jeong;Jung Gi Kim;Hyokyung Sung;Nokeun Park;Jae Bok Seol

Department of Materials Engineering and Convergence Technology,Center for K-metal,Gyeongsang National University(GNU),Jinju 52828,South Korea;School of Materials Science and Engineering,Yeungnam University,Gyeongbuk 38541,South Korea;Materials Research Team R&D,Hyundai Mobis,Yongin 16891,South Korea;Materials Technology Development Team,Doosan Heavy Industries&Construction,Changwon 51711,South Korea

材料科学技术（英文版）

[1]Kwang Kyu Ko;Hyo Ju Bae;Eun Hye Park;Hyeon-Uk Jeong;Hyoung Seok Park;Jae Seok Jeong;Jung Gi Kim;Hyokyung Sung;Nokeun Park;Jae Bok Seol-.A feasible route to produce 1.1 GPa ferritic-based low-Mn lightweight steels with ductility of 47％)[J].材料科学技术（英文版）,2022(22):225-237

ultrastrong,ploying,austen,ascribe

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