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

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalNot applicablepeer-review

2 Scopus Citations
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Author(s)

  • C. Xu
  • C. C. Bu
  • J. H. Luan
  • Z. B. Jiao
  • G. Chen

Detail(s)

Original languageEnglish
Pages (from-to)150-160
Journal / PublicationActa Materialia
Volume172
Online published24 Apr 2019
Publication statusPublished - 15 Jun 2019

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.

Research Area(s)

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