Solute/Stacking Fault Energies in Mg and Implications for Ductility

Research output: Chapters, Conference Papers, Creative and Literary Works (RGC: 12, 32, 41, 45)32_Refereed conference paper (with ISBN/ISSN)peer-review

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Author(s)

Detail(s)

Original languageEnglish
Title of host publicationMagnesium Technology 2018
EditorsDmytro Orlov, Vineet Joshi, Kiran N. Solanki, Neale R. Neelameggham
PublisherSpringer, Cham
Pages15-16
ISBN (Electronic)978-3-319-72332-7
ISBN (Print)978-3-319-72331-0
Publication statusPublished - Mar 2018
Externally publishedYes

Publication series

NameMinerals, Metals and Materials Series
VolumePart F7
ISSN (Print)2367-1181
ISSN (Electronic)2367-1696

Conference

TitleInternational Symposium on Magnesium Technology, 2018
PlaceUnited States
CityPhoenix
Period11 - 15 March 2018

Abstract

Mg is the lightest structural metal but pure Mg has low ductility due to strong plastic anisotropy and to a transition of <c+a> pyramidal dislocations to a sessile basal-oriented structure [1]. Alloying generally improves ductility, but the mechanisms of the enhancement are not yet known. Mg-3 wt% RE (RE = Y, Tb, Dy, Ho, Er) show high ductility [2], as compared to most commercial Mg–Al–Zn alloys at similar grain size. To investigate possible proposed mechanisms of ductility in alloys, and differences between Al, Zn, and Y solutes, first-principles density functional theory (DFT) calculations are used to compute all relevant stacking fault (SF) energies as a function of solute type (Y, Al, Zn) and concentration in the dilute limit. 
In DFT calculations, we compute the solute-SF interaction energy Eint (d) versus solute-SF distance di Accurate energies requires the use of large supercells. For the pyramidal II plane, a single solute may induce migration of the SF. Constraints, and corrections for the constraints, are thus needed. In the random alloy, every atom site has a probability c (in at.) to be occupied by a solute atom. The value of the SF energy of the alloy, at small c, is then γA = γMg + c/A0 Σi Eint (di ) 
The stacking fault energies for basal and pyramidal faults versus concentration are shown in Fig. 1 for the solutes Y, Al and Zn. From these results, we can draw some conclusions regarding ductility in Mg alloys. First, the proposed role of the I1 basal SF in ductility enhancement in Mg–Y [2] is not supported. The effects of Y can be achieved at twice the concentration using Al. However, neither Mg–Al or Mg–Zn alloys show significantly enhanced ductility. Second, using the I1 and pyr. II SFs for Y, elasticity calculations show that Y does not appear to significantly alter the energetics of the detrimental pyramidal-to-basal orientation transformation. Third, the only unique property of Y, compared to Al and Zn, is the much larger reduction of the pyramidal I SF energy. This suggests new mechanisms for enhanced ductility that will be discussed and supported by further results on other solutes.

Research Area(s)

  • Alloys, Dislocations, Ductility, Stacking faults

Citation Format(s)

Solute/Stacking Fault Energies in Mg and Implications for Ductility. / Yin, Binglun; Wu, Zhaoxuan; Curtin, W. A.

Magnesium Technology 2018. ed. / Dmytro Orlov; Vineet Joshi; Kiran N. Solanki; Neale R. Neelameggham. Springer, Cham, 2018. p. 15-16 (Minerals, Metals and Materials Series; Vol. Part F7).

Research output: Chapters, Conference Papers, Creative and Literary Works (RGC: 12, 32, 41, 45)32_Refereed conference paper (with ISBN/ISSN)peer-review