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Title: Prediction of Precipitation Strengthening in the Commercial Mg Alloy AZ91 Using Dislocation Dynamics

Abstract

In this paper, dislocation dynamics simulations were used to predict the strengthening of a commercial magnesium alloy, AZ91, due to β-Mg17Al12 formed in the continuous precipitation mode. The precipitate distributions used in simulations were determined based on experimental characterization of the sizes, shapes, and number densities of the precipitates for 10-hour aging and 50-hour aging. For dislocations gliding on the basal plane, which is expected to be the dominant contributor to plastic deformation at room temperature, the critical resolved shear stress to bypass the precipitate distribution was 3.5 MPa for the 10-hour aged sample and 16.0 MPa for the 50-hour aged sample. The simulation results were compared to an analytical model of strengthening in this alloy, and the analytical model was found to predict critical resolved shear stresses that were approximately 30 pct lower. A model for the total yield strength was developed and compared with experiment for the 50-hour aged sample. Finally, the predicted yield strength, which included the precipitate strengthening contribution from the DD simulations, was 132.0 MPa, in good agreement with the measured yield strength of 141 MPa.

Authors:
 [1];  [2];  [2];  [3];  [3]
+ Show Author Affiliations
  1. Idaho National Lab. (INL), Idaho Falls, ID (United States)
  2. Univ. of Michigan, Ann Arbor, MI (United States). Dept. of Materials Science and Engineering
  3. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Univ. of Michigan, Ann Arbor, MI (United States); Idaho National Lab. (INL), Idaho Falls, ID (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES)
OSTI Identifier:
1438644
Report Number(s):
LLNL-JRNL-734977
Journal ID: ISSN 1073-5623; TRN: US1900474
Grant/Contract Number:  
AC52-07NA27344; SC0008637
Resource Type:
Accepted Manuscript
Journal Name:
Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science
Additional Journal Information:
Journal Volume: 49; Journal Issue: 5; Journal ID: ISSN 1073-5623
Publisher:
ASM International
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 97 MATHEMATICS AND COMPUTING

Citation Formats

Aagesen, L. K., Miao, J., Allison, J. E., Aubry, S., and Arsenlis, A. Prediction of Precipitation Strengthening in the Commercial Mg Alloy AZ91 Using Dislocation Dynamics. United States: N. p., 2018. Web. doi:10.1007/s11661-018-4530-6.
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Aagesen, L. K., Miao, J., Allison, J. E., Aubry, S., & Arsenlis, A. Prediction of Precipitation Strengthening in the Commercial Mg Alloy AZ91 Using Dislocation Dynamics. United States. https://doi.org/10.1007/s11661-018-4530-6
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Aagesen, L. K., Miao, J., Allison, J. E., Aubry, S., and Arsenlis, A. Mon . "Prediction of Precipitation Strengthening in the Commercial Mg Alloy AZ91 Using Dislocation Dynamics". United States. https://doi.org/10.1007/s11661-018-4530-6. https://www.osti.gov/servlets/purl/1438644.
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@article{osti_1438644,
title = {Prediction of Precipitation Strengthening in the Commercial Mg Alloy AZ91 Using Dislocation Dynamics},
author = {Aagesen, L. K. and Miao, J. and Allison, J. E. and Aubry, S. and Arsenlis, A.},
abstractNote = {In this paper, dislocation dynamics simulations were used to predict the strengthening of a commercial magnesium alloy, AZ91, due to β-Mg17Al12 formed in the continuous precipitation mode. The precipitate distributions used in simulations were determined based on experimental characterization of the sizes, shapes, and number densities of the precipitates for 10-hour aging and 50-hour aging. For dislocations gliding on the basal plane, which is expected to be the dominant contributor to plastic deformation at room temperature, the critical resolved shear stress to bypass the precipitate distribution was 3.5 MPa for the 10-hour aged sample and 16.0 MPa for the 50-hour aged sample. The simulation results were compared to an analytical model of strengthening in this alloy, and the analytical model was found to predict critical resolved shear stresses that were approximately 30 pct lower. A model for the total yield strength was developed and compared with experiment for the 50-hour aged sample. Finally, the predicted yield strength, which included the precipitate strengthening contribution from the DD simulations, was 132.0 MPa, in good agreement with the measured yield strength of 141 MPa.},
doi = {10.1007/s11661-018-4530-6},
journal = {Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science},
number = 5,
volume = 49,
place = {United States},
year = {Mon Mar 05 00:00:00 EST 2018},
month = {Mon Mar 05 00:00:00 EST 2018}
}
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Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record
https://doi.org/10.1007/s11661-018-4530-6
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Citation Metrics:
Cited by: 13 works
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Figures / Tables:

Figure 1 Figure 1: (a) TEM micrograph of lath-shaped β-Mg17Al12 precipitate at 10 hour aging time. The zone axis is [0001]. The measured l and w is indicated on the figure, and the thickness t is measured in the [0001] direction (perpendicular to the plane of the page). (b) Same precipitate asmore » (a) with an ellipse superimposed on the image. For the dislocation dynamics simulations, precipitates are described as elliptical disks, with an elliptical shape in the basal plane and uniform thickness in the [0001] direction.« less
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Works referenced in this record:

Investigation of precipitation hardening by dislocation dynamics simulations
journal, November 2006

Orowan process controlled dislocation glide in materials containing incoherent particles
journal, July 2001

Modeling the precipitation processes and strengthening mechanisms in a Mg-Al-(Zn) AZ91 alloy
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Bauschinger effect in precipitation-strengthened materials: A dislocation dynamics investigation
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Comparison between dislocation dynamics model predictions and experiments in precipitation-strengthened Al–Li–Sc alloys
journal, October 2014

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Effective values of critical resolved shear stress for slip in polycrystalline magnesium and other hcp metals
journal, October 2010

Enabling strain hardening simulations with dislocation dynamics
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journal, January 2011

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journal, February 1967

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      Figure 2 (p. 12)figure
      Table 2 (p. 12)table
      Figure 3 (p. 13)figure
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      Table 4 (p. 15)table
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