Effects of retained austenite volume fraction, morphology, and carbon content on strength and ductility of nanostructured TRIP-assisted steels

MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING

卷:636

Article

Shen, Y. F.¹  Qiu, L. N.¹  Sun, X.²  Zuo, L.¹  Liaw, P. K.³  Raabe, D.⁴ 

[1] Northwestern Univ, Key Lab Anisotropy & Texture Mat MOE, Shenyang 110004, Peoples R China

[2] Pacific NW Natl Lab, Richland, WA 99352 USA

[3] Univ Tennessee, Dept Mat Sci & Engn, Knoxville, TN 37996 USA

[4] Max Planck Inst Eisenforsch GmbH, D-40237 Dusseldorf, Germany

关键词: Retained austenite;    Morphology;    Mechanical stability;    Strength;    Ductility;   

DOI  :  10.1016/j.msea.2015.04.030

来源: Elsevier

【 摘 要 】

With a suite of multi-modal and multi-scale characterization techniques, the present study unambiguously proves that a substantially-improved combination of ultrahigh strength and good ductility can be achieved by tailoring the volume fraction, morphology, and carbon content of the retained austenite (RA) in a transformation-induced-plasticity (TRIP) steel with the nominal chemical composition of 0.19C-030Si-1.76Mn-1.52Al (weight percent, wt%). After intercritical annealing and bainitic holding, a combination of ultimate tensile strength (UTS) of 1100 MPa and true strain of 50% has been obtained, as a result of the ultrafine RA lamellae, which are alternately arranged in the bainitic ferrite around junction regions of ferrite grains. For reference, specimens with a blocky RA, prepared without the bainitic holding, yield a low ductility (35%) and a low UTS (800 MPa). The volume fraction, morphology, and carbon content of RA have been characterized using various techniques, including the magnetic probing, scanning electron microscopy (SEM), electron-backscatter-diffraction (EBSD), and transmission electron microscopy (TEM). Interrupted tensile tests, mapped using EBSD in conjunction with the kernel average misorientation (KAM) analysis, reveal that the lamellar RA is the governing microstructure component responsible for the higher mechanical stability, compared to the blocky one. By coupling these various techniques, we quantitatively demonstrate that in addition to the RA volume fraction, its morphology and carbon content are equally important in optimizing the strength and ductility of TRIP-assisted steels. (C) 2015 Elsevier B.V. All rights reserved.

【 授权许可】

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