Multicomponent High-Strength Low-Alloy Steel Precipitation-Strengthened by Sub-nanometric Cu Precipitates and M2C Carbides

Divya Jain*, Dieter Isheim, Allen H. Hunter, David N. Seidman

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

41 Scopus citations

Abstract

HSLA-115 is a novel high-strength low-alloy structural steel derived from martensitic Cu-bearing HSLA-100. HSLA-100 is typically used in conditions with overaged Cu precipitates, to obtain acceptable impact toughness and ductility. Present work on HSLA-115 demonstrates that incorporating sub-nanometric-sized M2C carbides along with Cu precipitates produces higher strength steels that still meet impact toughness and ductility requirements. Isothermal aging at 823 K (550 °C) precipitates M2C carbides co-located with the Cu precipitates and distributed heterogeneously at lath boundaries and dislocations. 3D atom-probe tomography is used to characterize the evolution of these precipitates at 823 K (550 °C) in terms of mean radii, number densities, and volume fractions. These results are correlated with microhardness, impact toughness, and tensile strength. The optimum combination of mechanical properties, 972 MPa yield strength, 24.8 pct elongation to failure, and 188.0 J impact toughness at 255 K (−18 °C), is attained after 3-hour aging at 823 K (550 °C). Strengthening by M2C precipitates offsets the softening due to overaging of Cu precipitates and tempering of martensitic matrix. It is shown that this extended yield strength plateau can be used as a design principle to optimize strength and toughness at the same time.

Original languageEnglish (US)
Pages (from-to)3860-3872
Number of pages13
JournalMetallurgical and Materials Transactions A: Physical Metallurgy and Materials Science
Volume47
Issue number8
DOIs
StatePublished - Aug 1 2016

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Mechanics of Materials
  • Metals and Alloys

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