Hardening mechanisms and impact toughening of a high-strength steel containing low Ni and Cu additions

H. J. Kong, C. Xu, C. C. Bu, C. Da, J. H. Luan, Z. B. Jiao, G. Chen, C. T. Liu

Research output: Journal article publicationJournal articleAcademic researchpeer-review

15 Citations (Scopus)

Abstract

Aging treatments at 400–550 °C are commonly used to attain a peak strengthening for the Cu-rich nanocluster-strengthened high-strength low-alloy (HSLA) steels. However, these temperatures fall within the dangerous 300–600 °C temper-embrittlement regime, leading to poor impact toughness. On the other hand, aging at temperatures above the embrittlement regime can improve the impact toughness but at a great expense of strength. In this work, the strengthening mechanisms as well as the toughening of a low cost weldable HSLA steel with a low content of carbon (C ∼0.08 wt.%), nickel (Ni = 0.78 wt.%), and copper (Cu = 1.3 wt.%) were carefully investigated. Our findings show that the low-C-Ni-Cu HSLA steel is insensitive to the aging temperatures and can achieve a yield strength (YS) and ultimate tensile strength (UTS) over 1000 and 1100 MPa, respectively, with tensile ductility >10% (reduction of area >60%) at a heat-treat temperature of 640 °C through multiple strengthening mechanisms. Besides, a good low-temperature (−40 °C) impact performance (∼200 J) with high YS (∼900 MPa) and UTS (∼1000 MPa) can be obtained by seeking a strength balance among the fine grain size (∼2.5 μm), medium-sized (∼14 nm) overaged Cu-rich precipitates, tempered martensite, and fresh martensite (or carbides). Moreover, a relatively lower YS (∼800 MPa) and UTS (∼900 MPa) useful for steel manufacturing can be attained by a prolonged aging at 640 °C. In addition, the dislocation-precipitate interactions were also explored based on the dislocation theories in this study.

Original languageEnglish
Pages (from-to)150-160
Number of pages11
JournalActa Materialia
Volume172
DOIs
Publication statusPublished - 15 Jun 2019

Keywords

  • Cu-rich nanocluster-strengthened high-strength low alloy (HSLA) steel
  • Dislocation-precipitate interactions
  • Impact toughening
  • Multiple strengthening mechanisms
  • Temper-embrittlement

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Ceramics and Composites
  • Polymers and Plastics
  • Metals and Alloys

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