Dislocation-twin boundary interactions induced nanocrystalline via SPD processing in bulk metals.

Fucheng Zhang,Tiansheng Wang,Jie Kang,Xiaoyong Feng,Zhinan Yang

doi:10.1038/srep08981

Abstract

This report investigated dislocation–twin boundary (TB) interactions that cause the TB to disappear and turn into a high-angle grain boundary (GB). The evolution of the microstructural characteristics of Hadfield steel was shown as a function of severe plastic deformation processing time. Sessile Frank partial dislocations and/or sessile unit dislocations were formed on the TB through possible dislocation reactions. These reactions induced atomic steps on the TB and led to the accumulation of gliding dislocations at the TB, which resulted in the transition from coherent TB to incoherent GB. The factors that affect these interactions were described, and a physical model was established to explain in detail the feasible dislocation reactions at the TB.

Highlights

This report investigated dislocation–twin boundary (TB) interactions that cause the TB to disappear and turn into a high-angle grain boundary (GB)
Face-centered cubic metals have been found to deform via twinning more readily than their coarse-grained counterparts[29,30,31], this increases the probability of interactions between dislocations and twins. These reports raise certain questions: Is the dislocation–TB interaction a type of grain refinement mechanism in most metals? If it is, what are the possible dislocation reactions at TB? How do the extrinsic factors affect the interactions during nanocrystallization?
The results reveal that the feasible dislocation–TB interactions cause the TB to disappear and turn into a grain boundary (GB) during nanocrystallization

Summary

Introduction

This report investigated dislocation–twin boundary (TB) interactions that cause the TB to disappear and turn into a high-angle grain boundary (GB). M any studies explored the nanocrystallization mechanisms during the severe plastic deformation (SPD) of various metals, including pure Fe1–2, Cu and Cu alloys[3,4,5], stainless steels[6,7], Ni and Ni alloys[8,9,10,11], and Al and Al alloys[12] These mechanisms principally include dislocation activities (dislocation nucleation, slipping, and reaction), twinning, and their interactions. Face-centered cubic metals have been found to deform via twinning more readily than their coarse-grained counterparts[29,30,31], this increases the probability of interactions between dislocations and twins These reports raise certain questions: Is the dislocation–TB interaction a type of grain refinement mechanism in most metals? The interactions and the factors that affect these interactions are described in detail

Methods

Results

Conclusion