A feasible route to produce 1.1 GPa ferritic-based low-Mn lightweight steels with ductility of 47%  

作　　者：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 

机构地区：[1]Department of Materials Engineering and Convergence Technology,Center for K-metal,Gyeongsang National University(GNU),Jinju 52828,South Korea [2]School of Materials Science and Engineering,Yeungnam University,Gyeongbuk 38541,South Korea [3]Materials Research Team R&D,Hyundai Mobis,Yongin 16891,South Korea [4]Materials Technology Development Team,Doosan Heavy Industries&Construction,Changwon 51711,South Korea

出　　处：《Journal of Materials Science & Technology》2022年第22期225-237,共13页材料科学技术（英文版）

基　　金：The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.Patent application(Korean Patent application number 10-2020-0172118)has been filed based on the results of this study。

摘　　要：High- and medium-Mn (H/M-Mn) base lightweight steels are a class of ultrastrong structural materials 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 techniques, which can unavoidably provoke labor and cost concerns. Herein, we have developed a facilestrategy that circumvents the strength–ductility trade-off in low-Mn ferritic lightweight steels, by employing 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 embeddedin a ferrite matrix for partitioning more carbon into smaller austenite grains than into the larger austenite 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 andtotal elongation to both the size-dependent dislocation movement in austenite grains and the controlleddeformation-induced martensitic transformation. The low-carbon-partitioned large austenite grains increase the strength and ductility as a consequence of the combined martensitic transformation andhigh dislocation density-induced hardening and by interface strengthening. Additionally, high-carbonpartitioned small austenite grains enhance the strength and ductility by planar dislocation glide (inthe low strain regime) and by cross-slipping and delayed martensitic transformation (in the high strainregime). The concept of size-dependent dislocation engineering may provide different pathways for developing a wide range of heterogeneous-structured low-Mn lightweight steels, suggesting that LTP maybe desirable for broad industrial applications at an economic cost.

关 键 词：Low-Mn lightweight steel Carbon partitioning Metastable austenite Dislocation movement 

分 类 号：TG142[一般工业技术—材料科学与工程]