ORALS

SESSION: MagnesiumThuPM1-R4	Intl Symp. on Next Generation Magnesium Alloys and Their Applications for Sustainable Development
Thu Oct, 24 2019 / Room: Adonis
Session Chairs: Elias Aifantis; Session Monitor: TBA

14:25: [MagnesiumThuPM106]
In Situ Neutron Diffraction during Compression or Tension of Extruded Mg97Zn1Y2
Stefanus Harjo¹ ; Kazuya Aizawa² ; Wu Gong³ ; Takuro Kawasaki² ; ¹Japan Atomic Energy Agency, Naka-gun, Japan; ²Japan Atomic Energy Agency, Tokai-mura, Japan; ³Kyoto University, Tokai-mura, Japan;
Paper Id: 239 [Abstract]

Mg₉₇Zn₁Y₂ alloy is a magnesium alloy with a duplex microstructure consisting of a long period stacking ordered (LPSO) phase and an alpha-Mg phase [1]. Kink deformation was observed in an as-cast Mg₉₇Zn₁Y₂ alloy subjected to hot compression. The refinement of LPSO via kinking was found to be the reason for strengthening of the material from microscopy analyses [2]. Direct evidence, however, has shown that increase in strength via kinking has not been observed so far. In this work, in situ neutron diffraction was used to investigate the anisotropic deformation behavior of LPSO and alpha-Mg phases during uniaxial compression or tension in an as-cast Mg₉₇Zn₁Y₂ alloy and an extruded Mg₉₇Zn₁Y₂ alloy. The evolutions of phase stresses in both the LPSO and alpha-Mg phases were evaluated and discussed with the occurrences of twinning and kinking during compression or tension. The as-cast Mg₉₇Zn₁Y₂ alloy was prepared by high frequency induction melting in a carbon crucible. The extruded Mg₉₇Zn₁Y₂ alloy was prepared by hot extrusion at 623 K of a round bar of an as-cast Mg₉₇Zn₁Y₂ alloy at an extrusion ratio of 10 and a ram speed of 2.5 mm/s in the air. The in-situ neutron diffraction experiment during compression was carried out using TAKUMI of J-PARC and a cylindrical test piece having a length of 16 mm and a diameter of 8 mm. The peak positions and integrated peak intensities were evaluated from the obtained diffraction patterns and the evolutions of lattice strains. The texture was then estimated and the phase stresses were subsequently evaluated. The response of phase stress to the applied stress of alpha-Mg deviated from the linearity which describes a smaller value at the applied stress that is lower than the macroscopic yield stress for the as-cast alloy. The response obtained pretended to keep the linearity up to the macroscopic yield stress for the extruded alloy. The details will be presented.

References:
[1] Y. Kawamura et al., Material Transactions 42 (2001) 1172-1176.\n[2] X.H. Shao, Z.Q. Yang, X.L. Ma, Acta Mater. 58 (2010) 4760-4771.

SESSION: MagnesiumFriPM1-R4	Intl Symp. on Next Generation Magnesium Alloys and Their Applications for Sustainable Development
Fri Oct, 25 2019 / Room: Adonis
Session Chairs: Takao Tsumuraya; Session Monitor: TBA

14:50: [MagnesiumFriPM107]
Dynamics of Kink Formation Behavior under Compressive Stress via Hybrid Measurement of In Situ Neutron Diffraction and Acoustic Emission
Kazuya Aizawa¹ ; Wu Gong² ; Stefanus Harjo³ ; Takuro Kawasaki¹ ; ¹Japan Atomic Energy Agency, Tokai-mura, Japan; ²Kyoto University, Tokai-mura, Japan; ³Japan Atomic Energy Agency, Naka-gun, Japan;
Paper Id: 237 [Abstract]

Dynamics of kink formation behavior under compressive stress on the 18R Mg-based LPSO alloy, prepared by the one-directional solidification technique, will be presented. This technique uses materials of high strength dual phase Mg-based LPSO alloys [1]. This is observed at room temperature via a hybrid measurement of in situ neutron diffraction and acoustic emission (AE). By in situ neutron diffraction, we revealed the relationship between the basal plane strains and kink formation. On the other hand, by AE measurement, we obtained statistics about kink formation size by analysis of AE absolute energy which consists of flat behavior in low energy regions and power law behavior in higher energy regions. This is basic knowledge for introducing kink structure efficiently. In the AE data plot, we can clearly observe the emergence of an amoeba which is defined by the image of the logarithm of the absolute complex coordinates of the plane complex algebraic curve in the mathematics context. This excludes the scale factor. Specifically, a plot of the energy-difference between (n+1) and n events versus energy-difference between n and (n-1) events indicates an amoeba whose Newton polygon consists of the coordinates (0,0), (1,0) and (0,1). This characteristic has deep meaning regarding the dynamics of kink formation. This reveals that the statistical sequence of kink formation is governed by a simple complex algebraic curve.

References:
[1] Y. Kawamura et al., Material Transactions 42 (2001) 1172-1176.

SESSION: MagnesiumFriPM1-R4	Intl Symp. on Next Generation Magnesium Alloys and Their Applications for Sustainable Development
Fri Oct, 25 2019 / Room: Adonis
Session Chairs: Takao Tsumuraya; Session Monitor: TBA

15:15: [MagnesiumFriPM108]
Deformation Behavior of Directionally Solidified Mg/LPSO Alloy with Respect to its Lamellar Structure
Daria Drozdenko¹ ; Kristián Máthis² ; Michiaki Yamasaki³ ; Stefanus Harjo⁴ ; Wu Gong⁵ ; Kazuya Aizawa⁶ ; Yoshihito .kawamura⁷ ; ¹Magnesium Research Center, Kumamoto University, Kumamoto, Japan; ²Department of Physics of Materials, Charles University, Prague, Czech Republic; ³Kumamoto university, Kumamoto, Japan; ⁴Japan Atomic Energy Agency, Naka-gun, Japan; ⁵Kyoto University, Tokai-mura, Japan; ⁶Japan Atomic Energy Agency, Tokai-mura, Japan; ⁷Kumamoto University, Kumamoto, Japan;
Paper Id: 308 [Abstract]

Recently, a new generation of Mg alloys with an LPSO phase have received considerable attention due to their enhanced mechanical and promising high-temperature properties compared to the conventional Mg alloys. Nevertheless, those alloys still suffer from anisotropy of mechanical properties. It is generally agreed that besides the dislocation slip, deformation kinking and twinning contribute to the plastic deformation of those alloys. The materials’ parameters (shape and orientation of LPSO phase, grain size, texture) as well as the experimental conditions (loading direction, temperature etc.) are factors on which deformation kinking depends for it to be considered common for Mg/LPSO alloys. The conditions for kink formation in Mg-LPSO alloys and their dependence on temperature, however, are still under consideration. In this present work, a directionally solidified Mg -24 wt.% Y- 12wt.% Zn alloy having a lamellar structure elongated along the solidification direction was investigated. In order to reveal the effect of orientation on deformation behavior, uniaxial compression tests were performed parallel and perpendicular to the LSPO lamellae. Active deformation mechanisms were revealed by combination of two advanced in-situ techniques: acoustic emission and neutron diffraction. Detailed microscopy observations by optical and scanning electron microscopy (including EBSD, BSD imaging and IGMA) were performed for getting information about microstructure changes (e.g. twin and kink formation) with respect to a lamellar structure and crystallographic orientation. Kinking was found to be a dominant deformation mechanism during compression along the lamellar structure, resulting in high yield strength. In the case of loading perpendicular to lamellae, kinking was limited to well oriented lamellae and rather higher activity of the <c+a> dislocation slip was observed. IGMA analysis has shown that all observed kinks in both orientations were found to be of <1-100>-and <1-210>-rotation types.

References:
[1] Kawamura et al. Mater Trans 42(7) 2001 1172-1176
[2] Hagihara et al. Intermetallics 18 (2010) 267-276
[3] Yamasaki et al. Acta Mater, 61 (2013) 2065-2076
[4] Garces et al. Int. J. Plast. 106 (2018) 107-128
[5] W.Gong et al. Int J Plast 111 (2018) 288-306