Experimental validation of negative stacking fault energies in metastable face-centered cubic materials

Konstantin V Werner,Marcel A J Somers,Frank Niessen,Matteo Villa

doi:10.1063/5.0063761

Konstantin V Werner, Marcel A J Somers + Show 2 more

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https://doi.org/10.1063/5.0063761

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Journal: Applied Physics Letters	Publication Date: Oct 4, 2021
Citations: 15	License type: cc-by

Affiliation: Technical University of Denmark

Abstract

Stacking fault energy (SFE) is considered an important parameter to predict the prevalent plastic deformation mechanism in face-centered cubic (fcc) alloys. Experimental methods for determining SFE presuppose that SFE is positive. Density functional theory (DFT) is a promising tool to predict alloy compositions with low SFEs and desirable mechanical properties. For metastable fcc alloys, DFT predicts negative SFE values, which cannot be validated by the existing experimental procedures. In this contribution, it is demonstrated that experimental procedures to assess SFE values only provide an apparent value that needs correction. The suggested correction relies on the critical resolved shear stress for twinning, which is grain size-dependent, just like the apparent SFE. The correction provides SFE values that are independent of grain size. Accordingly, negative SFEs predicted by DFT can be experimentally validated.

Highlights

Density functional theory (DFT) is a promising tool to predict alloy compositions with low Stacking fault energy (SFE) and desirable mechanical properties
DFT predicts negative SFE values, which cannot be validated by the existing experimental procedures
The current paradigm for tailoring the deformation mechanisms in fcc metals is tailoring the intrinsic stacking fault energy (SFE),[3,4] which is the excess energy associated with a stacking fault suspended between the leading and trailing Shockley partial dislocations that result from the dissociation of a full dislocation

Summary

Introduction

The current paradigm for tailoring the (combination of) deformation mechanisms in fcc metals is tailoring the intrinsic stacking fault energy (SFE),[3,4] which is the excess energy associated with a stacking fault suspended between the leading and trailing Shockley partial dislocations that result from the dissociation of a full dislocation. DFT predicts negative SFE values, which cannot be validated by the existing experimental procedures. The suggested correction relies on the critical resolved shear stress for twinning, which is grain size-dependent, just like the apparent SFE.

Results

Conclusion