Deformation Mechanisms of FCC-Structured Metallic Nanocrystal with Incoherent Twin Boundary

Yang Tao,Libo Fu,Zhanxin Wang,Lihua Wang,Yufeng Zhao

doi:10.3390/met11111672

Yang Tao, Libo Fu + Show 3 more

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https://doi.org/10.3390/met11111672

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Abstract

Incoherent twin boundaries (ITBs) can significantly affect the mechanical properties of twin-structured metals. However, most previous studies have focused on the deformation mechanism of the coherent twin boundary (CTB), and metals with ITB-accommodated plasticity still require further investigation. In this study, deformation mechanisms of FCC-structured nanocrystal metals with ITBs were investigated using molecular dynamic (MD) simulations. We revealed that three deformation mechanisms occur in metals with ITBs. The first type of deformation was observed in Au, where the plasticity is governed by partial dislocation intersections with CTBs or reactions with each other to form Lomer–Cottrell (L–C) locks. In the second type, found in Al, the deformation is governed by reversible ITB migration. The third type of deformation, in Ni and Cu, is governed by partial dislocations emitted from the ITB or the tips of the stacking faults (SFs). The observed L–C lock formation, as well as the reversible ITB migration and partial dislocation emission from the tips of SFs, have rarely been reported before.

Highlights

Previous studies have shown that face-centered cubic (FCC) structured metals with growth nanotwins always exhibit ultrahigh strength and excellent ductility [1,2,3,4,5]
Many molecular dynamics (MD) simulations and experimental investigations have suggested that the ultrahigh strength of twin-structured metals results from partial dislocations intersecting with coherent twin boundaries (CTBs) [10,20,21,22]
We showed that three deformation mechanisms, including the partial dislocation intersection with CTBs or reaction with each other to form Lomer–Cottrell (L–C) locks, reversible incoherent twin boundaries (ITBs) migration, and partial dislocations emitted from the ITB or the tips of the stacking faults (SFs), occur in different FCC metals

Summary

Introduction

Previous studies have shown that face-centered cubic (FCC) structured metals with growth nanotwins always exhibit ultrahigh strength and excellent ductility [1,2,3,4,5]. Many molecular dynamics (MD) simulations and experimental investigations have suggested that the ultrahigh strength of twin-structured metals results from partial dislocations intersecting with coherent twin boundaries (CTBs) [10,20,21,22]. These studies on the deformation mechanism of CTBs suggest that the strengthening effect in twin-structured metals resulted from dislocation–CTB interactions [24,25,26,27,28]. In FCC-structured metals, the ITB consists of Shockley partial dislocations on each {111} plane [30,31,32]. It will be interesting to provide systematic evidence on how ITBs accommodate the plastic deformation of various FCC-structured metals

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