Role of yttrium in activation of 〈c + a〉 slip in magnesium: An atomistic approach

doi:10.1016/j.scriptamat.2015.06.028

Scripta Materialia

Volume 108, November 2015, Pages 104-108

https://doi.org/10.1016/j.scriptamat.2015.06.028 Get rights and content

Abstract

The effect of Y addition on the slip behavior of an edge dislocation on basal, prismatic and second-order pyramidal slip planes of Mg has been investigated using a molecular dynamics simulation. It is found that Y increases the critical resolved shear stress of basal slip more than that of non-basal slip and eventually reduces the difference in the CRSS between different slip systems, which is proposed as the reason for the experimentally reported activation of 〈c + a〉 slip in Mg–Y alloys.

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Acknowledgments

This work was financially supported by Pohang Iron and Steel Co. (POSCO) under Contract No. 2013Y006 and partly (N.J.K.) by the WPM Program funded by the Ministry of Trade, Industry and Energy, Republic of Korea.

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Citation Excerpt :
A few computation studies have found that solute Y can critically reduce the CRSS ratio between non-basal slip and basal slip in Mg. By simulating the interaction between solute Y with dislocation cores, Kim et al. [17] estimated the ratio of CRSSpyramidal <c+a> /CRSSbasal to be reduced from a value greater than 100 in pure Mg to around 1.8 in Mg-1.0at%Y (equivalent to Mg-3.6 wt%Y). Another study by Tsuru and Chrzan [20] using DFT estimated the ratio of CRSSprism <a> /CRSSbasal to be reduced from a value greater than 20 in pure Mg to around 1.5 in Mg-1.0at%Y.
Mg-Y cast alloy shows excellent ductility (elongation to failure > 15%) compared with pure Mg and commercial Mg cast alloys. By monitoring the microstructure evolution during an in situ tensile test of a Mg-2.5 wt%Y alloy, we identify the activation of prismatic <c> slip, which is rare in Mg. Synchrotron X-ray micro-beam Laue diffraction (μ-Laue) and transmission electron microscopy revealed the morphology of prismatic <c> slip bands and individual <c> dislocations. Density functional theory and molecular dynamics calculations indicate that solute Y can significantly reduce the stacking fault energy (SFE) along <c> direction on prismatic plane in Mg lattice and thus facilitate the nucleation of <c> dislocations during deformation. The presence of free <c> dislocations in the Mg lattice can also lead to nucleation of {10–12} twins even under unfavorable geometric conditions.
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Role of yttrium in activation of 〈c + a〉 slip in magnesium: An atomistic approach

Abstract

Graphical abstract

Section snippets

Acknowledgments

Int. J. Plast.

Mater. Sci. Eng. A

Scr. Mater.

Scr. Mater.

Acta Mater.

Mater. Sci. Eng. A

Acta Mater.

Acta Mater.

Mater. Sci. Eng. A

Mater. Sci. Eng. A

Scr. Mater.

Acta Mater.

Acta Mater.

Acta Mater.