Title: Micromechanical Fields Associated with Irregular Deformation Twins in Magnesium

Abstract

Understanding and controlling the development of deformation twins is paramount for engineering strong and stable hexagonal close-packed (HCP) Mg alloys. Actual twins are often irregular in boundary morphology and twin crystallography, deviating from the classical picture commonly used in theory and simulation. In this work, the elastic strains and stresses around irregular twins are examined both experimentally and computationally to gain insight into how twins develop and the microstructural features that influence their development. A nanoprecession electron diffraction (N-PED) technique is used to measure the elastic strains within and around a $$\left\{ {10\overline{1}2} \right\}$$ tensile twin in AZ31B Mg alloy with nm scale resolution. A full-field elasto-viscoplastic fast Fourier transform (EVP-FFT) crystal plasticity model of the same sub-grain and irregular twin structure is employed to understand and interpret the measured elastic strain fields. The calculations predict spatially resolved elastic strain fields in good agreement with the measurement, as well as all the stress components and the dislocation density fields generated by the twin, which are not easily obtainable from the experiment. The model calculations find that neighboring twins, several twin thicknesses apart, have little influence on the twin-tip micromechanical fields. Furthermore, this work reveals that irregularity in the twin-tip shape has a negligible effect on the development of the elastic strains around and inside the twin. Importantly, the major contributor to these micromechanical fields is the alignment of the twinning shear direction with the twin boundary.

Authors:

Leu, Brandon ^[1]; Mariyappan, Arul Kumar  ^[2];

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Rottmann, Paul F. ^[3]; Hemker, Kevin J. ^[4]; Beyerlein, Irene J. ^[1]

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+ Show Author Affiliations

1. Univ. of California, Santa Barbara, CA (United States)
2. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
3. Univ. of Kentucky, Lexington, KY (United States)
4. Johns Hopkins Univ., Baltimore, MD (United States)

Publication Date:

Mon Aug 15 00:00:00 EDT 2022

Research Org.:

Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

Sponsoring Org.:

USDOE Office of Science (SC). Office of Basic Energy Sciences (BES); National Science Foundation (NSF)

OSTI Identifier:

1885751

Report Number(s):

LA-UR-22-29044
Journal ID: ISSN 1059-9495

Grant/Contract Number:  

89233218CNA000001; FWP 06SCPE401; MOM-2051390; DMR-1709865

Resource Type:

Accepted Manuscript

Journal Name:

Journal of Materials Engineering and Performance

Additional Journal Information:

Journal Volume: 32; Journal Issue: 6; Journal ID: ISSN 1059-9495

Publisher:

Springer

Country of Publication:

United States

Language:

English

Subject:

36 MATERIALS SCIENCE; crystal plasticity; deformation twin; local strain; magnesium; N-PED