Superb strength and high plasticity in laves phase rich eutectic medium-entropy-alloy nanocomposites

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

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Author(s)

Detail(s)

Original languageEnglish
Pages (from-to)57-72
Journal / PublicationInternational Journal of Plasticity
Volume106
Online published7 Mar 2018
Publication statusPublished - Jul 2018

Abstract

Laves phase and laves-phase based conventional composites usually show extreme brittleness at room temperature due to poor fracture toughness. However, in this work, we design a FeCoNiNb0.5 medium-entropy-alloy nanocomposite which possesses a high volume fraction (>50%) of a cubic laves phase but shows superb strength and excellent malleability at room temperature. This high mechanical performance results from the formation of an in-situ nano-scale lamellar structure that joins the hard cubic laves phase and soft medium entropy face-centered cubic (FCC) phase through a semi-coherent interface. When the size of the lamellar structures is tuned below a critical value, this nanocomposite exhibits strong and sustainable strain hardening, leading to a fracture strain over 20% and fracture strength over 3.5 GPa in conventional compression. The mechanism for the unusual strain hardening in the laves-phase rich nanocomposite is explored afterwards with micromechanical experiments and theoretical modeling, which unveils a size-controlled transition in the plasticity mechanism from dislocation slip to twinning in the nano-scale laves phase. Our current work demonstrates that, through mixing a set of carefully selected elements, one can obtain high performance dual-phase eutectic
nanostructures which are promising for structural applications.

Research Area(s)

  • Eutectic alloy, High entropy alloy, Laves phase, Size effect, Twinning