{10-12} Twinning Mechanism During In Situ Micro-Tensile Loading of Pure Mg: Role of Basal Slip and Twin-Twin Boundary Interaction

53 Pages Posted: 23 Jun 2020

See all articles by Nicolò Maria della Ventura

Nicolò Maria della Ventura

University of St. Gallen - Laboratory for Mechanics of Materials and Nanostructures

Szilvia Kalácska

University of St. Gallen - Laboratory for Mechanics of Materials and Nanostructures

Daniele Casari

University of St. Gallen - Laboratory for Mechanics of Materials and Nanostructures

Thomas Edward James Edwards

University of St. Gallen - Laboratory for Mechanics of Materials and Nanostructures

Johann Michler

University of St. Gallen - Laboratory for Mechanics of Materials and Nanostructures

Amit Sharma

University of St. Gallen - Laboratory for Mechanics of Materials and Nanostructures

Roland Logé

Ecole Polytechnique Fédérale de Lausanne - Laboratory of ThermoMechanical Metallurgy (LMTM)

Xavier Maeder

University of St. Gallen - Laboratory for Mechanics of Materials and Nanostructures

Abstract

An SEM in situ uniaxial tensile testing setup allowing HR-EBSD acquisition during deformation was used to study the extension twinning mechanism in magnesium (Mg) at the micron scale. Structures with strain gauge sizes of 20 × 5 × 8 µm were fabricated by Ga-FIB in pure Mg with two different crystal orientations, respectively perfectly aligned with, and at 5° to, the [0001] axis. Limited {10-12} twin formation was identified in the former case, while twinning was found to largely accommodate the plastic deformation in the latter case. These two different mechanisms are explained by the activation of basal slip when loading at 5° to the c-axis, which triggers {10-12} twin nucleation and strongly favors twin growth and propagation. The other orientation shows the activation of pyramidal slip together with only limited {10-12} twin growth. The critical resolved shear stress for {10-12} twinning has been determined to be ten times higher than in bulk material due to size effects. 3D HR-EBSD mapping enabled reconstruction of the three dimensional twin structure after deformation. From this, the interaction between twinning dislocations ahead of a twin tip and a pre-existing twin boundary was studied, where the GND distribution and the local shear stress in the active twin variant coordinate system were determined. The results show plastic accommodation up to ~11% of strain through transmission of twinning dislocations across a twin boundary, activation of several slip systems, and the formation of a third extension twin variant.

Keywords: Magnesium In situ tension test Deformation twinning 3D EBSD HR-EBSD

Suggested Citation

Ventura, Nicolò Maria della and Kalácska, Szilvia and Casari, Daniele and Edwards, Thomas Edward James and Michler, Johann and Sharma, Amit and Logé, Roland and Maeder, Xavier, {10-12} Twinning Mechanism During In Situ Micro-Tensile Loading of Pure Mg: Role of Basal Slip and Twin-Twin Boundary Interaction. Available at SSRN: https://ssrn.com/abstract=3628969 or http://dx.doi.org/10.2139/ssrn.3628969

Nicolò Maria della Ventura (Contact Author)

University of St. Gallen - Laboratory for Mechanics of Materials and Nanostructures ( email )

Überlandstrasse 129
Dübendorf, 8600
Switzerland

Szilvia Kalácska

University of St. Gallen - Laboratory for Mechanics of Materials and Nanostructures ( email )

Überlandstrasse 129
Dübendorf, 8600
Switzerland

Daniele Casari

University of St. Gallen - Laboratory for Mechanics of Materials and Nanostructures ( email )

Überlandstrasse 129
Dübendorf, 8600
Switzerland

Thomas Edward James Edwards

University of St. Gallen - Laboratory for Mechanics of Materials and Nanostructures ( email )

Überlandstrasse 129
Dübendorf, 8600
Switzerland

Johann Michler

University of St. Gallen - Laboratory for Mechanics of Materials and Nanostructures ( email )

Überlandstrasse 129
Dübendorf, 8600
Switzerland

Amit Sharma

University of St. Gallen - Laboratory for Mechanics of Materials and Nanostructures ( email )

Überlandstrasse 129
Dübendorf, 8600
Switzerland

Roland Logé

Ecole Polytechnique Fédérale de Lausanne - Laboratory of ThermoMechanical Metallurgy (LMTM)

Rue de la Maladière 71b
Neuchâtel, 2000
Switzerland

Xavier Maeder

University of St. Gallen - Laboratory for Mechanics of Materials and Nanostructures ( email )

Überlandstrasse 129
Dübendorf, 8600
Switzerland

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