Study of retained austenite and nano-scale precipitation and their effects on properties of a low alloyed multi-phase steel by the two-step intercritical treatment

Xie, Z. J.; Zhou, W. H.; Zeng, C. Y.

doi:10.1016/J.MATCHAR.2016.01.009

Title: Study of retained austenite and nano-scale precipitation and their effects on properties of a low alloyed multi-phase steel by the two-step intercritical treatment

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Abstract

Microstructure evolution and properties were studied in a low carbon low alloyed hot-rolled bainitic steel by annealing and annealing plus tempering. Microstructure of the hot-rolled steel consists of lath bainite and martensite. By annealing at 720 °C for 30 min and water quenching, multi-phase microstructure consisting of intercritical ferrite, tempered bainite/martensite, retained austenite and fresh martensite was obtained. With increasing annealing temperature to 760 °C, microstructure of the steel consisted of intercritical ferrite, fresh martensite without retained austenite. After the second step of tempering at 680 °C for samples annealed both at 720 °C and 760 °C, ~ 8–9% volume fraction of retained austenite was obtained in the multi-phase microstructure. Moreover, fine precipitates of VC with size smaller than 10 nm and copper precipitates with size of ~ 10–50 nm were obtained after tempering. Results from scanning transmission electron microscopy (STEM) give evidence to support that the partitioning of Mn, Ni and Cu is of significance for retained austenite stabilization. Due to the combined contribution of multiphase microstructure, the transformation-induced-plasticity effect of retained austenite and strengthening effect of nanometer-sized precipitates, yield strength greater than 800 MPa, yield to tensile ratio of 0.9, uniform elongation of ~ 9% and good lowmore »« less

Authors:: Xie, Z. J.; Zhou, W. H.; Zeng, C. Y.

Publication Date:: Tue Mar 15 00:00:00 EDT 2016

OSTI Identifier:: 22587112

Resource Type:: Journal Article

Journal Name:: Materials Characterization

Additional Journal Information:: Journal Volume: 113; Other Information: Copyright (c) 2016 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 1044-5803

Country of Publication:: United States

Language:: English

Subject:: 36 MATERIALS SCIENCE; 77 NANOSCIENCE AND NANOTECHNOLOGY; ANNEALING; AUSTENITE; CARBON; ELONGATION; FERRITE; LOW ALLOY STEELS; MARTENSITE; MICROSTRUCTURE; NANOSTRUCTURES; PRECIPITATION; QUENCHING; TEMPERING; TRANSMISSION ELECTRON MICROSCOPY

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                    Xie, Z. J., Han, G., E-mail: hangang@mater.ustb.edu.cn, Zhou, W. H., Zeng, C. Y., and Shang, C.J., E-mail: cjshang@ustb.edu.cn. Study of retained austenite and nano-scale precipitation and their effects on properties of a low alloyed multi-phase steel by the two-step intercritical treatment.  United States: N. p., 2016. 
        Web.  doi:10.1016/J.MATCHAR.2016.01.009.

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                    Xie, Z. J., Han, G., E-mail: hangang@mater.ustb.edu.cn, Zhou, W. H., Zeng, C. Y., & Shang, C.J., E-mail: cjshang@ustb.edu.cn. Study of retained austenite and nano-scale precipitation and their effects on properties of a low alloyed multi-phase steel by the two-step intercritical treatment.  United States.  https://doi.org/10.1016/J.MATCHAR.2016.01.009

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                    Xie, Z. J., Han, G., E-mail: hangang@mater.ustb.edu.cn, Zhou, W. H., Zeng, C. Y., and Shang, C.J., E-mail: cjshang@ustb.edu.cn. 2016.  
        "Study of retained austenite and nano-scale precipitation and their effects on properties of a low alloyed multi-phase steel by the two-step intercritical treatment".  United States.  https://doi.org/10.1016/J.MATCHAR.2016.01.009.

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@article{osti_22587112,

  title        = {Study of retained austenite and nano-scale precipitation and their effects on properties of a low alloyed multi-phase steel by the two-step intercritical treatment},

  author       = {Xie, Z. J. and Han, G., E-mail: hangang@mater.ustb.edu.cn and Zhou, W. H. and Zeng, C. Y. and Shang, C.J., E-mail: cjshang@ustb.edu.cn},

  abstractNote = {Microstructure evolution and properties were studied in a low carbon low alloyed hot-rolled bainitic steel by annealing and annealing plus tempering. Microstructure of the hot-rolled steel consists of lath bainite and martensite. By annealing at 720 °C for 30 min and water quenching, multi-phase microstructure consisting of intercritical ferrite, tempered bainite/martensite, retained austenite and fresh martensite was obtained. With increasing annealing temperature to 760 °C, microstructure of the steel consisted of intercritical ferrite, fresh martensite without retained austenite. After the second step of tempering at 680 °C for samples annealed both at 720 °C and 760 °C, ~ 8–9% volume fraction of retained austenite was obtained in the multi-phase microstructure. Moreover, fine precipitates of VC with size smaller than 10 nm and copper precipitates with size of ~ 10–50 nm were obtained after tempering. Results from scanning transmission electron microscopy (STEM) give evidence to support that the partitioning of Mn, Ni and Cu is of significance for retained austenite stabilization. Due to the combined contribution of multiphase microstructure, the transformation-induced-plasticity effect of retained austenite and strengthening effect of nanometer-sized precipitates, yield strength greater than 800 MPa, yield to tensile ratio of 0.9, uniform elongation of ~ 9% and good low temperature impact toughness of 147 J at − 40 °C were achieved. - Highlights: • Stable retained austenite was produced in a low alloyed steel. • Partition of Mn, Ni and Cu was confirmed by STEM for austenite stabilization. • Nano-sized VC and Cu precipitates were achieved by second tempering. • High strength–high toughness with low Y/T ratio was obtained.},

  doi          = {10.1016/J.MATCHAR.2016.01.009},

  url          = {https://www.osti.gov/biblio/22587112},
  journal      = {Materials Characterization},

  issn         = {1044-5803},

  number       = ,

  volume       = 113,

  place        = {United States},

  year         = {Tue Mar 15 00:00:00 EDT 2016},

  month        = {Tue Mar 15 00:00:00 EDT 2016}

}

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