An extraordinary-performance gradient nanostructured Hadfield manganese steel containing multi-phase nanocrystalline-amorphous core-shell surface layer by laser surface processing

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

2 Scopus Citations
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Author(s)

  • Wanting Sun
  • Jiasi Luo
  • Yim Ying Chan
  • J.H. Luan
  • Xu-Sheng Yang

Detail(s)

Original languageEnglish
Pages (from-to)209-222
Journal / PublicationJournal of Materials Science and Technology
Volume134
Online published26 Jul 2022
Publication statusPublished - 20 Jan 2023

Abstract

Reducing grain size (i.e. increasing the fraction of grain boundaries) could effectively strengthen nanograined metals but inevitably sacrifices the ductility and possibly causes a strengthening-softening transition below a critical grain size. In this work, a facile laser surface remelting-based technique was employed and optimized to fabricate a ∼600 μm-thick heterogeneous gradient nanostructured layer on an austenitic Hadfield manganese steel, in which the average grain size is gradually decreased from ∼200 μm in the matrix to only ∼8 nm in the nanocrystalline-amorphous core-shell topmost surface. Atomic-scale microstructural characterizations dissected the gradient refinement processes along the gradient direction, i.e. transiting from the dislocations activities and twinning in sub-region to three kinds of martensitic transformations, and finally a multi-phase nanocrystalline-amorphous core-shell structural surface. Mechanical tests (e.g. nanoindentation, bulk-specimen tensile, and micro-pillar compression) were conducted along the gradient direction. It confirms a tensile strength of ∼1055 MPa and ductility of ∼10.5% in the laser-processed specimen. Particularly, the core-shell structural surface maintains ultra-strong (tensile strength of ∼1.6 GPa, micro-pillar compressive strength of ∼4 GPa at a strain of ∼8%, and nanoindentation hardness of ∼7.7 GPa) to overcome the potential strengthening-softening transition. Such significant strengthening effects are ascribed to the strength-ductility synergetic effects-induced extra work hardening ability in gradient nanostructure and the well-maintained dislocation activities inside extremely refined nanograins in the multi-phase nanocrystalline-amorphous core-shell structural surface, which are evidenced by atomic-scale observations and theoretical analysis. This study provides a unique hetero-nanostructure through a facile laser-related technique for extraordinary mechanical performance.

Research Area(s)

  • Gradient nanostructure, Hadfield manganese steel, Laser surface processing, Martensitic transformation, Nanocrystalline-amorphous

Citation Format(s)

An extraordinary-performance gradient nanostructured Hadfield manganese steel containing multi-phase nanocrystalline-amorphous core-shell surface layer by laser surface processing. / Sun, Wanting; Luo, Jiasi; Chan, Yim Ying et al.

In: Journal of Materials Science and Technology, Vol. 134, 20.01.2023, p. 209-222.

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