High strength-superplasticity combination of ultrafine-grained ferritic steel:The significant role of nanoscale carbides  

作　　者：J.W.Liang Y.F.Shen R.D.K.Misra P.K.Liaw 

机构地区：[1]Key Laboratory for Anisotropy and Texture of Materials(MOE),School of Materials Science and Engineering,Northeastern University,Shenyang,110004,China [2]The State Key Lab of Rolling&Automation,Northeastern University,Shenyang,110819,China [3]Laboratory for Excellence in Advanced Steel Research,University of Texas at El Paso,TX,79968,USA [4]Department of Materials Science and Engineering,University of Tennessee,Knoxville,TN,37996,USA

出　　处：《Journal of Materials Science & Technology》2021年第24期131-144,共14页材料科学技术（英文版）

基　　金：financially supported by the Natural Science Foundation of China(No.51922026);the Fundamental Research Funds for the Central Universities(Nos.N2002013 and N2002005);the support from the National Science Foundation(Nos.DMR-1611180 and 1809640)with the program directors,Drs.G.Shiflet and D.Farkas。

摘　　要：There is currently a gap in our understanding of mechanisms that contribute to high strength and high plasticity in high strength UFG ferritic steel with nano-size Fe3 C carbides in situations that involve combination of various strain rates and high temperature.In this regard,we describe the mechanistic basis of obtaining high strength-high plasticity combination in an ultrafine-grained(UFG)(~500±30 nm)ferritic steel with nano-size carbides,which sustained large plastic deformation,exceeding 100%elongation at a temperature significantly below 0.5 of the absolute melting point(Tm).To address the missing gap in our knowledge,we conducted a series of experiments involving combination of strain rate and temperature effects in conjunction with electron microscopy and atom probe tomography(APT).Strain rate studies were carried out at strain rates in the range of 0.0017-0.17 s^(-1)and at different temperatures from 25℃to 600℃.Dynamic recrystallization occurred at 600℃,resulting in a significant decrease in yield and tensile strength.Nevertheless,the UFG ferritic steels had an advantage in tensile strength(UTS)and elongation-to-failure(εf)at 600℃,especially at strain rate of 0.0017 s^(-1),with high UTSof 510 MPa and excellent low temperature(<0.42 Tm)superplasticity(εf=110%).These mechanical properties are significantly superior compared to similar type of steels at identical temperature.A mechanistic understanding of mechanical behavior of UFG ferritic steels is presented by combining the effect of strain rate,temperature,and nano-size carbides.

关 键 词：UFG ferritic steel Strain rate Temperature Nano-size precipitate Low temperature superplasticity 

分 类 号：TG142.23[一般工业技术—材料科学与工程]