J. Mater. Sci. Technol. ›› 2023, Vol. 136: 180-199.DOI: 10.1016/j.jmst.2022.07.029

• Research Article • Previous Articles     Next Articles

Development of the high-strength ductile ferritic alloys via regulating the intragranular and grain boundary precipitation of G-phase

Mujin Yanga,b, Chao Huanga, Jiajia Hanc, Haichen Wud, Yilu Zhaoa, Tao Yange, Shenbao Jinf, Chenglei Wanga, Zhou Lia, Ruiying Shuf, Cuiping Wangc, Huanming Lud, Gang Shaf,*, Xingjun Liua,g,h,*   

  1. aSchool of Materials Science and Engineering, Harbin Institute of Technology, Shenzhen 518055, China;
    bDepartment of Mechanical and Energy Engineering, Southern University of Science and Technology, Shenzhen 518055, China;
    cCollege of Materials and Fujian Provincial Key Laboratory of Materials Genome, Xiamen University, Xiamen 361005, China;
    dTest Center, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201, China;
    eDepartment of Materials Science and Engineering, City University of Hong Kong, Hong Kong, China;
    fDepartment of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094, China;
    gState Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Shenzhen 150001, China;
    hInstitute of Materials Genome and Big Data, Harbin Institute of Technology, Shenzhen 518055, China
  • Received:2022-03-23 Revised:2022-07-11 Accepted:2022-07-11 Published:2023-02-10 Online:2022-08-28
  • Contact: * E-mail addresses: jiajiahan@xmu.edu.cn (J. Han), wuhaichen@nimte.ac.cn (H. Wu), gang.sha@njust.edu.cn (G. Sha), xjliu@hit.edu.cn (X. Liu).

Abstract: A typical G-phase strengthened ferritic model alloy (1Ti:Fe-20Cr-3Ni-1Ti-3Si, wt.%) has been carefully studied using both advanced experimental (EBSD, TEM and APT) and theoretical (DFT) techniques. During the classic “solid solution and aging” process, the superfine (Fe, Ni)2TiSi-L21 particles densely precipitate within the ferritic grain and subsequently transform into the (Ni, Fe)16Ti6Si7-G phase. In the meanwhile, the elemental segregation at grain boundaries and the resulting precipitation of a large amount of the (Ni, Fe)16Ti6Si7-G phase are also observed. These nanoscale microstructural evolutions result in a remarkable increase in hardness (100-300 HV) and severe embrittlement. When the “cold rolling and aging” process is used, the brittle fracture is effectively suppressed without loss of nano-precipitation strengthening effect. Superhigh yield strength of 1700 MPa with 4% elongation at break is achieved. This key improvement in mechanical properties is mainly attributed to the pre-cold rolling process which effectively avoids the dense precipitation of the G-phase at the grain boundary. These findings could shed light on the further exploration of the precipitation site via optimal processing strategies.

Key words: G-phase, Precipitation strengthening, Grain boundary segregation, Nano-precipitates