Extremely hard amorphous-crystalline hybrid steel surface produced by deformation induced cementite amorphization

Wei Guo, Yifei Meng, Xie Zhang, Vikram Bedekar, Hongbin Bei, Scott Hyde, Qianying Guo, Gregory B. Thompson, Rajiv Shivpuri, Jian min Zuo, Jonathan D. Poplawsky

Research output: Contribution to journalArticlepeer-review


Amorphous and nanograined (NG) steels are two categories of strong steels. However, over the past decade, their application has been hindered by their limited plasticity, the addition of expensive alloying elements, and processing challenges associated with producing bulk materials. Here, we report that the surface of a carburized Fe-Mn-Si martensitic steel with extremely low elemental alloying additions can be economically fabricated into an amorphous-nanocrystalline hybrid structure. Atom probe tomography and nanobeam diffraction of a hard turned steel surface together with molecular dynamics (MD) simulations reveal that the original cementite surface structure experiences a size-dependent amorphization and phase transformation during heavy plastic deformation. MD simulations further show that the martensite-cementite interface serves as a nucleation site for cementite amorphization, and that cementite can become disordered if further strained when the cementite particles are relatively small. These graded structures exhibit a surface hardness of ∼16.2 GPa, which exceeds the value of ∼8.8 GPa for the original nanocrystalline martensitic steel and most nanocrystalline steels reported before. This practical and cost-efficient approach for producing a hard surface with retained bulk ductility and toughness can provide expanded opportunities for producing an amorphous-crystalline hybrid structure in steels and other alloy systems.

Original languageEnglish (US)
Pages (from-to)107-118
Number of pages12
JournalActa Materialia
StatePublished - Jun 15 2018


  • Amorphous-crystalline hybrid structure
  • Atom probe tomography
  • Cementite decomposition
  • Hard turning
  • Molecular dynamics simulation

ASJC Scopus subject areas

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


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