Enhancing strength-ductility balance in Fe-Mn-Al-C-Ni austenitic low-density steel via intragranular dual-nanoprecipitation  

作　　者：Y.F.An X.P.Chen L.Mei Y.C.Qiu Y.Z.Li W.Q.Cao 

机构地区：[1]College of Materials Science and Engineering,Chongqing University,Chongqing 400044,China [2]Guangxi Engineering Research Center for Characteristic Metallic Powder Materials,School of Electronic Engineering,Guangxi University of Science and Technology,Liuzhou 545006,China [3]Central Iron&Steel Research Institute,Beijing 100081,China

出　　处：《Journal of Materials Science & Technology》2024年第33期38-51,共14页材料科学技术(英文版)

基　　金：supported by the National Natural Science Foundation of China(Nos.52171105 and 51871062).

摘　　要：Strength-ductility trade-off is usually an inevitable scenario inκ′-carbides strengthened austenitic lightweight steel.The reduction of ductility is primarily attributed to the shearing of coherentκ′-carbides by dislocations,resulting in strain localization and ultimately leading to a low work hardening rate.Semicoherent B2 particles,on the other hand,effectively enhance the work hardening capability due to the non-shearable feature.However,achieving a large volume fraction and uniform distribution of B2 particles within the austenite matrix,as well as optimizing their morphology as fine particles,remains a challenge for austenitic lightweight steel.In this study,we have addressed the above challenges by implementing the two-step aging process combined with pre-cold rolling process.The pre-cold rolling treatment,performed prior to the initial aging treatment at 900℃,effectively promotes the heterogeneous nucleation of B2 particles by introducing dislocations,resulting in a more uniform distribution of B2 particles and a refinement in size(with an average length of 200–500 nm and a width of 50–80 nm).Furthermore,these intragranular B2 particles exhibit the typical K-S and N-W orientation relationships with the austenite matrix.Subsequently,after the second-step aging process at 450℃,spherical nano-sizedκ′-carbides(5 nm)are homogeneously dispersed within the austenite matrix.The above dual nanoparticles provide an approximate precipitation hardening effect of 400 MPa.Concurrently,the nanoscale“planar slip and dislocation bow-out”multiple deformation mechanisms contribute to an efficient source of work hardening capability,leading to a beneficial synergy of strength-ductility.This promising strategy is expected to expand the applications of dual-nanoprecipitation austenitic low-density steel in various lightweight structural materials.

关 键 词：Lightweight steel Dual-nanoprecipitation Precipitation strengthening Work hardening capability 

分 类 号：TG1[金属学及工艺—金属学]