Stress-dependent dislocation core structures leading to non-Schmid behavior

Abstract

The stress-dependent core structures of dislocations for basal slip in magnesium are calculated using ab initio generalized stacking fault energy surface and microscopic phase-field method. The dissociation of dislocation cores exhibits the dependence on the non-shear component in the stress tensor; the Peierls stress is found to either become virtually zero or increase by an order of magnitude, depending on the applied shear stress magnitude and direction. The results, in contrast to the classical Schmid's law for crystal plasticity, are explained using the Escaig stress concept and the resulting implication on plastic deformation is discussed.

GRAPHICAL ABSTRACT

IMPACT STATEMENT

Dependence of dislocation core structure on stress is predicted using a microscopic phase-field model with subatomic resolution, revealing non-Schmid behavior together with significant influence on the Peierls stress.

KEYWORDS:

• Magnesium
• basal dislocation
• Peierls stress
• phase-field
• Escaig stress

Acknowledgements

DQ would like to acknowledge the support from China Postdoctoral Science Foundation under grant number 2018M630437, National Postdoctoral Program for Innovative Talents under grant number BX201600099, The National Key Research and Development Program of China under grant number 2020YFB0704503, and National Science Foundation of China under grant number 51801123. PZ would like to acknowledge the support from Shanghai Pujiang Program under grant number 20PJ1406500. PZ and YW would like to acknowledge the support from the US National Science Foundation under grant number DMR-1922239. DRT acknowledge the support from the US National Science Foundation under Grants No. 0825961 and 1410596. DQ and PZ jointly conceptualized the work and developed the model; DQ conducted the simulations and analysis; DRT provided the ab initio GSF energy surface data; YW organized the partnership and supervised the work; DQ and PZ took the lead in writing the manuscript, with contributions from all other authors.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by China Postdoctoral Science Foundation: [Grant Number 2018M630437]; National Science Foundation of China: [Grant Number 51801123]; Shanghai Pujiang Program: [Grant Number 20PJ1406500]; The National Key Research and Development Program of China: [Grant Number 2020YFB0704503]; US National Science Foundation: [Grant Number 0825961, 1410596,DMR-1922239]; National Postdoctoral Program for Innovative Talents: [Grant Number BX201600099].